Risk Management Series

Design Guide 

for Improving School Safety in Earthquakes, Floods, 

and High Winds

FEMA P-424 / December 2010

FEMA

Risk Management Series Publication

Design Guide 

for Improving School Safety in Earthquakes, Floods, 

and High Winds

FEMA P-424 / December 2010

FEMA

FEMA does not endorse any non-U.S. government entities. This publication is U.S. government work and is not copyrightable in the U.S. 

See 17 USC §105.
Design Guide for Improving School Safety in Earthquakes, Floods, and High Winds

T he views, opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors 

and do not necessarily reflect the official policy or position of 

the Department of Homeland Security (DHS), Federal Emergency 

Management Agency (FEMA), or other federal agencies. The publication of these views by FEMA does not confer any individual rights or 

cause of action against the United States. Additionally, neither FEMA 

or any of its employees makes any warrantee, expressed or implied, or 

assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, product, or process included in 

this publication. Users of information from this publication assume all 

liability arising from such use.

Any appearances of hyperlinks do not constitute endorsement by FEMA 

of the website or the information, products, or services contained therein.  For links outside FEMA, FEMA does not exercise any editorial control 

over the information you may find at these locations.  Users must adhere 

to any intellectual property rights contained in this publication or in material in linked websites.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS i

Foreword and 

Acknowledgments

Background

O ur society places great importance on the education system and 

its schools, and has a tremendous investment in current and future schools. Nearly 50 million students were expected to attend 

approximately 99,000 public elementary and secondary schools in the 

fall of 2009, with an additional 5.8 million expected to attend private 

schools.1

 The sizes of these school facilities range from one-room rural 

schoolhouses to citywide and mega schools that house 5,000 or more 

students. The school is both a place of 

learning and an important community resource and center.

This publication is concerned with the 

protection of schools and their occupants against natural hazards. Architects 

and engineers deal with natural hazards 

in building design and construction and 

building codes have provisions for protection against natural hazards.

This manual addresses two core concepts: multi-hazard design and performance-based design. Neither is revolutionary, but both represent an 

evolution in design thinking that is in tune with the increasing complexity of today’s buildings and that takes advantage of developments and 

innovations in building technology:

1 U.S. Department of Education, National Center for Education Statistics, Fast Facts, Back to 

School Stats, http://nces.ed.gov/fastfacts/display.asp?id=372, accessed April 19, 2010.
ii DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

FOREWORD AND ACKNOWLEDGMENTS

n Multi-hazard design recognizes the fundamental characteristics of 

hazards and how they interact, so that design for protection becomes 

integrated with all the other design demands.

n Performance-based design suggests conducting a systematic investigation to ensure that the specific concerns of building owners and 

occupants are addressed, rather than relying on only the minimum 

requirements of the building code for protection against hazards. 

Building codes focus on providing life safety, while property protection is secondary. Performance-based design provides additional 

levels of protection that cover property damage and functional interruption within a financially-feasible context. 

This publication stresses that the identification of hazards and their frequency and careful consideration of design to resist these hazards must 

be integrated with all other design issues, and be included from the inception of the site selection and building design process. Although the 

basic issues to be considered in planning a school construction program 

are more or less common to all school districts, the specific processes 

differ greatly because each school district has its own approach. Districts 

vary in size, from a rural district responsible for only a few schools, to 

a city district or statewide system overseeing a complex program of all 

school types and sizes. Any of these districts may be responsible for new 

design and construction, renovations, and additions. While one district 

may have a long-term program of school construction and be familiar 

with programming, financing, hiring designers, bidding procedures, 

contract administration, and commissioning a new building, another 

district may not have constructed a new school for decades, and have no 

staff members familiar with the process.

Scope

T his publication is intended to provide design guidance for the 

protection of school buildings and their occupants against natural hazards. It focuses on the design of elementary and secondary 

schools (K–12), as well as repair, renovation, and additions to existing schools. It is one of a series of publications in which multi-hazard 

and performance-based design are addressed (FEMA 577, Design Guide 

for Improving Hospital Safety in Earthquakes, Floods, and High Winds, and 

FEMA 543, Design Guide for Improving Critical Facility Safety from Flooding 

and High Winds). 

This publication considers the safety of school buildings to occupants, 

and the economic losses and social disruption caused by building damage and destruction. The volume covers three natural hazards that have 

the potential to result in unacceptable risk and loss: earthquakes, floods, 
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS iii

FOREWORD AND ACKNOWLEDGMENTS

and high winds. A companion volume, FEMA 428, Primer to Design Safe 

School Projects in Case of Terrorist Attacks, covers the manmade hazards of 

physical, chemical, biological, and radiological attacks.

This publication is intended to assist design professionals and school officials involved in the technical and financial decisions related to school 

construction, repair, and renovations. 

Organization and Content of the Manual

C hapters 1–3 present issues and background information that are 

common to all hazards. Chapters 4–6 cover the development of 

specific risk management measures for each of the three natural 

hazards addressed.

Chapter 1 opens with a brief outline of the past, present, and future of 

school design. Past school design is important because many of these 

older, and even historic, schools are still in use and may be exposed to 

the effects of earthquakes, floods, and high winds. 

Chapter 2 introduces the concept of performance-based design, an approach to design that is driven by the desired performance of a new or 

retrofitted facility. 

Chapter 3 introduces the concept of multi-hazard design and presents 

a general description and comparison of the hazards, including charts 

that show how the design to resist one hazard may interact with the design for other hazards. 

Chapters 4, 5, and 6 outline how to address risk management 

concerns for protection of schools against earthquakes, floods, 

and high winds, respectively. Information is presented on the 

nature of each hazard and its effect on vulnerability, as well as 

and the consequences of building exposure. Procedures for 

risk assessment are followed by descriptions of current methods of reducing the effects of each hazard. These methods 

vary, depending on the hazard under consideration. 

Appendix A contains a list of acronyms that appear in this 

manual. 

This publication provides recommendations to create safe 

schools, but is necessarily limited. Readers should not expect to use the information directly to develop plans and 
iv DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

FOREWORD AND ACKNOWLEDGMENTS

specifications. Rather, the information is intended to help designers 

and facility decision-makers, who may be unfamiliar with the concepts 

involved, to understand fundamental approaches to risk mitigation planning and design. With this understanding, they can then approach the 

implementation phase of detailed planning, which involves consultants, 

procurement personnel, and project administration. 

Acknowledgments

Principal Authors:

Christopher Arnold, Building Systems Development, Inc.

Jack Lyons, School Facilities Consultant

James Munger, James G. Munger and Associates

Rebecca C. Quinn, RCQuinn Consulting, Inc.

Thomas L. Smith, TLSmith Consulting, Inc.

2010 Update:

Philip Line, URS Corporation

Rebecca C. Quinn, RCQuinn Consulting, Inc.

Thomas L. Smith, TLSmith Consulting, Inc.

FEMA Contributors:

Milagros Kennett, DHS, S&T

John Plisich, FEMA, Region IV

Mike Robinson, FEMA HQ

2010 Update:

Paul Tertell, PE, FEMA HQ

Reviewers and Contributors:

Joe Agron, American School and University

Deb Daly, Greenhorne & O’Mara, Inc. 

Connie Deshpande, U.S. Department of Education

Randy Haslam, Jordan, Utah, School District
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS v

FOREWORD AND ACKNOWLEDGMENTS

Danny Kilcollins, Florida Department of Community Affairs

Fred Krimgold, World Institute for Disaster Risk Management

Tom Kube, Council of Educational Facility Planners International

Eric Letvin, URS Corporation, Consultant and Project Manager

Julie Liptak, Greenhorne & O’Mara, Inc. 

Bill Modzeleski, Department of Education

Jack Paddon, Williams and Paddon Architects and Planners

Bob Pendley, Greenhorne & O’Mara, Inc.

Bebe Pinter, Harris County Department of Education

Wanda Rizer, Consultant

John Sullivan, Portland Cement Association

Jon Traw, Traw Associates 

French Wetmore, French and Associates

2010 Update:

Eric Letvin, URS Corporation, Consultant and Project Manager

Ivy Porportage, URS Corporation

Wanda Rizer, Consultant

Scott Tezak, URS Corporation, Consultant and Project Manager

This publication will be revised periodically and FEMA welcomes comments and feedback to improve future editions. 

Please send comments and feedback via e-mail to 

riskmanagementseriespubs@dhs.gov.

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS vii

Table of Contents

Foreword and Acknowledgments................................................................................................i

Background ......................................................................................................................................i

Scope ...............................................................................................................................................ii

Organization and Content of the Manual.....................................................................................iii

Acknowledgments .......................................................................................................................... iv

Principal Authors ............................................................................................................... iv

Contributors ....................................................................................................................... iv

1 An Overview of the School Design and Construction Process............................... 1-1

11.1 Introduction ..................................................................................................................... 1-1

1.2 School Construction: The National Picture .................................................................... 1-2

1.3 Past School Design............................................................................................................ 1-2

1.4 Present School Design...................................................................................................... 1-8

1.5 Future School Design ....................................................................................................... 1-9

1.6 The Design and Construction Process........................................................................... 1-11

1.7 References....................................................................................................................... 1-14

2 Performance-Based Design ......................................................................................... 2-1

2.1 Background....................................................................................................................... 2-1

2.2 Prescriptive vs. Performance-Based Design ..................................................................... 2-3
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2.3 The Performance-Based Design Process ......................................................................... 2-4

2.4 Acceptable Risk and Performance Levels........................................................................ 2-5

2.5 Considerations For Achieving Continuous

Operation Performance Level ......................................................................................... 2-8

2.6 Performance-Based Flood Design ................................................................................. 2-10

2.7 Performance-Based High-Wind Design ........................................................................ 2-11

2.8 Performance-Based Seismic Design .............................................................................. 2-12

2.9 References....................................................................................................................... 2-14

3 Multihazard Design........................................................................................................ 3-1

3.1 Introduction ..................................................................................................................... 3-1

3.2 The Hazards Compared ................................................................................................... 3-1

3.2.1 Location: Where do Hazards Occur? ................................................................ 3-2

3.2.2 Warning: How Much Warning is There? .......................................................... 3-4

3.2.3 Frequency: How Likely are They to Occur?...................................................... 3-5

3.3 A Comparison of Potential Losses ................................................................................... 3-6

3.4 Fire and Life Safety......................................................................................................... 3-10

3.5 Multihazard Design Interactions.................................................................................... 3-11

3.6 References....................................................................................................................... 3-18

4 Making Schools Safe From Earthquakes................................................................... 4-1

4.1 Introduction ..................................................................................................................... 4-1

4.2 The Nature and Probability of Earthquakes.................................................................... 4-2

4.2.1 Earthquakes and Other Geologic Hazards ....................................................... 4-2

4.2.2 Earthquakes: A National Problem .................................................................... 4-4

4.2.3 Common Measures of Earthquakes .................................................................. 4-8

4.2.4 Determination of Local Earthquake Hazards................................................. 4-11

4.3 Vulnerability: What Earthquakes Can Do to Schools.................................................... 4-13

4.3.1 Vulnerability of Schools................................................................................... 4-13
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4.3.2 Earthquake Damage to Schools ..................................................................... 4-16

4.3.3 Significant School Damage in U.S. Earthquakes............................................ 4-23

4.3.4 Consequences: Casualties, Financial Loss, and

Operational Disruption ................................................................................... 4-27

 4.4 Scope, Effectiveness, and Limitations of Codes ............................................................ 4-28

4.4.1 The Background of Seismic Provisions in Building Codes ............................ 4-29

4.4.2 Seismic Codes and Schools.............................................................................. 4-29

4.4.3 The Effectiveness of Seismic Codes................................................................. 4-30

4.5 Evaluating Existing Schools for Seismic Risk and Specific Risk

Reduction Methods ........................................................................................................ 4-31

4.5.1 Rapid Visual Screening.................................................................................... 4-31

4.5.2 Systems Checklist for School Seismic Safety Evaluation................................. 4-32

4.5.3 Seismic Evaluation of Existing Buildings........................................................ 4-37

4.6 Earthquake Risk Reduction Methods ............................................................................ 4-38

4.6.1 Risk Reduction for New Schools ..................................................................... 4-39

4.6.2 Risk Reduction for Existing Schools ............................................................... 4-49

4.7 The School as a Post-Earthquake Shelter ...................................................................... 4-55

4.8 References and Sources of Additional

Information..................................................................................................................... 4-56

4.9 Glossary of Earthquake Terms ....................................................................................... 4-58

5 Making Schools Safe From Flooding.......................................................................... 5-1

5.1 General Design Considerations ....................................................................................... 5-1

5.1.1 The Nature of Flooding..................................................................................... 5-2

5.1.2 Probability of Occurrence or Frequency .......................................................... 5-4

5.1.3 Flood Characteristics and Loads ....................................................................... 5-8

5.1.3.1 Hydrostatic Loads........................................................................... 5-10

5.1.3.2 Hydrodynamic Loads..................................................................... 5-11

5.1.3.3 Debris Impact Loads ...................................................................... 5-13

5.1.3.4 Erosion and Local Scour................................................................ 5-14

5.1.4 Design Parameters ........................................................................................... 5-15

5.1.4.1 Flood Depth .................................................................................. 5-15
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5.1.4.3 Flood Velocity—Riverine ............................................................... 5-19

5.1.4.4 Flood Velocity—Coastal ................................................................. 5-19

5.1.5 Flood Hazard Maps and Zones........................................................................ 5-20

5.1.5.1 NFIP Flood Maps............................................................................ 5-21

5.1.5.2 NFIP Flood Zones .......................................................................... 5-22

5.1.5.3 Coastal A Zones ............................................................................. 5-25

5.1.6 Floodplain Management Requirements and Building Codes ....................... 5-26

5.1.6.1 Overview of the NFIP..................................................................... 5-27

5.1.6.2 Summary of the NFIP Minimum Requirements........................... 5-28

5.1.6.3 Executive Order 11988 and Critical Facilities .............................. 5-30

5.1.6.4 Model Building Codes and Standards........................................... 5-31

5.2 Schools Exposed to Flooding......................................................................................... 5-33

5.2.1 Identifying Flood Hazards at School Sites ...................................................... 5-33

5.2.2 Vulnerability: What Flooding Can Do to Existing Schools............................. 5-34

5.2.2.1 Site Damage.................................................................................... 5-34

5.2.2.2 Structural Damage ......................................................................... 5-36

5.2.2.3 Nonstructural Damage................................................................... 5-39

5.2.2.4 Utility System Damage ................................................................... 5-41

5.2.2.5 Contents Damage........................................................................... 5-44

5.3 Requirements and Best Practices in Flood Hazard Areas............................................. 5-45

5.3.1 Evaluating Risk and Avoiding Flood Hazards................................................. 5-45

5.3.2 Benefits and Costs: Determining Acceptable Risk.......................................... 5-46

5.3.3 Site Modifications ............................................................................................ 5-48

5.3.4 Elevation Considerations................................................................................. 5-50

5.3.5 Dry Floodproofing Considerations ................................................................. 5-56

5.3.6 Flood Damage-Resistant Materials .................................................................. 5-59

5.3.7 Access Roads .................................................................................................... 5-61

5.3.8 Utility Installations........................................................................................... 5-61

5.3.9 Potable Water and Wastewater Systems........................................................... 5-63

5.3.10 Storage Tank Installations ............................................................................... 5-64

5.3.11 Accessory Structures ........................................................................................ 5-64
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5.4 Risk Reduction for Existing Schools.............................................................................. 5-64

5.4.1 Introduction..................................................................................................... 5-64

5.4.2 Site Modifications ............................................................................................ 5-65

5.4.3 Additions.......................................................................................................... 5-67

5.4.4 Repairs, Renovations, and Upgrades .............................................................. 5-68

5.4.5 Retrofit Dry Floodproofing ............................................................................. 5-69

5.4.6 Utility Installations........................................................................................... 5-70

5.4.7 Potable Water and Wastewater Systems........................................................... 5-72

5.4.8 Other Damage Reduction Measures............................................................... 5-72

5.4.9 Drainage Improvements.................................................................................. 5-73

5.4.10 Emergency Measures ....................................................................................... 5-74

5.5 Schools as Emergency Shelters and Safe Rooms........................................................... 5-75

5.6 Checklist for Vulnerability of Floodprone Sites and Schools........................................... 5-77

5.7 References and Sources of Additional Information...................................................... 5-83

5.8 Glossary of Flood Protection Terms............................................................................... 5-86

6 Making Schools Safe From High Winds ..................................................................... 6-1

6.1 General Design Considerations ....................................................................................... 6-1

6.1.1 Nature of High Winds .......................................................................................... 6-3

6.1.2 Probability of Occurrence ................................................................................... 6-4

6.1.3 Wind/Building Interactions................................................................................. 6-6

6.1.4 Building Codes.................................................................................................... 6-12

6.1.4.1 Scope of Building Codes................................................................ 6-13

6.1.4.2 Effectiveness and Limitations of Building Codes.......................... 6-14

6.2 Schools Exposed to High Winds.................................................................................... 6-17

6.2.1 Vulnerability: What High Winds Can Do to Schools......................................... 6-17

6.2.1.1 Types of Building Damage ............................................................. 6-17

6.2.1.2 Ramification of Damage ................................................................ 6-21

6.2.2 Priorities, Costs, And Benefits: New Schools ..................................................... 6-25

6.2.2.1 Priorities ......................................................................................... 6-25

6.2.2.2 Cost, Budgeting, and Benefits ....................................................... 6-26
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6.2.3 Priorities, Costs, and Benefits: Existing Schools................................................ 6-28

6.2.3.1 Priorities ......................................................................................... 6-28

6.2.3.2 Cost, Budgeting, and Benefits ....................................................... 6-29

6.2.4 Evaluating Schools for Risk from High Winds................................................... 6-31

6.2.4.1 New Buildings................................................................................. 6-31

6.2.4.2 Existing Buildings .......................................................................... 6-32

6.2.4.3 Portable Classrooms....................................................................... 6-33

6.3 Requirements and Best Practices in High-Wind Regions ............................................. 6-34

6.3.1 General School Design Considerations ............................................................. 6-35

6.3.1.1 Site .................................................................................................. 6-35

6.3.1.2 School Design................................................................................. 6-37

6.3.1.3 Construction Contract Administration ......................................... 6-42

6.3.1.4 Post-Occupancy Inspections, Periodic

Maintenance, Repair, and Replacement ....................................... 6-43

6.3.1.5 Site and General Design Considerations in

Hurricane-Prone Regions ............................................................. 6-44

6.3.2 Structural Systems............................................................................................... 6-46

6.3.2.1 Design Parameters for Structural Systems..................................... 6-46

6.3.2.2 Design Parameters for Structural Systems in

Hurricane-Prone Regions .............................................................. 6-52

6.3.3 Building Envelope .............................................................................................. 6-53

6.3.3.1 Exterior Doors................................................................................ 6-53

6.3.3.2 Windows and Skylights................................................................... 6-57

6.3.3.3 Windows and Skylights in Hurricane-Prone Regions ................... 6-60

6.3.3.4 Non-Load-Bearing Walls, Wall Coverings, and Soffits .................. 6-63

6.3.3.5 Non-Load-Bearing Walls, Wall Coverings, and 

Soffits in Hurricane-Prone Regions............................................... 6-73

6.3.3.6 Roof Systems................................................................................... 6-74

6.3.3.7 Roof Systems in Hurricane-Prone Regions ................................... 6-86

6.3.4 Nonstructural Systems and Equipment ............................................................. 6-94

6.3.4.1 Exterior-Mounted Mechanical Equipment ................................... 6-94

6.3.4.2 Nonstructural Systems and Mechanical

Equipment in Hurricane-Prone Regions .................................... 6-104

6.3.4.3 Exterior-Mounted Electrical and Communications 

Equipment.................................................................................... 6-106
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6.3.4.4 Lightning Protection Systems in Hurricane-Prone

Regions......................................................................................... 6-109

6.3.5 Municipal Utilities In Hurricane-Prone Regions............................................. 6-115

6.3.5.1 Electrical Power ........................................................................... 6-116

6.3.5.2 Water Service ............................................................................... 6-117

6.3.5.3 Sewer Service ............................................................................... 6-118

6.3.6 Post-Design Considerations in Hurricane-Prone Regions............................ 6-118

6.3.6.1 Construction Contract Administration ...................................... 6-118

6.3.6.2 Periodic Inspections, Maintenance, and Repair ........................ 6-118

6.4 Remedial Work on Existing Facilities ......................................................................... 6-119

6.4.1 Structural Systems............................................................................................. 6-121

6.4.2 Building Envelope ........................................................................................... 6-122

6.4.2.1 Windows and Skylights................................................................. 6-123

6.4.2.2 Non-Load-Bearing Walls, Wall Coverings, and Soffits ................ 6-127

6.4.2.3 Roof Coverings............................................................................. 6-128

6.4.3 Exterior-Mounted Equipment.......................................................................... 6-131

6.4.3.1 HVAC Units, Condensers, Fans, Exhaust 

Stacks, and Ductwork .................................................................. 6-131

6.4.3.2 Antenna (Communications Mast)............................................... 6-134

6.4.3.3 Lightning Protection Systems...................................................... 6-134

6.5 Occupant Protection Best Practices in Tornado- and 

Hurricane-Prone Regions ............................................................................................ 6-135

6.6 Checklist For Building Vulnerability of Schools Exposed to High Winds ................. 6-139

6.7 References and Sources of Additional Information ................................................... 6-143

6.8 Glossary of High Wind Protection Terms.................................................................... 6-147

Appendix

Appendix A: Acronyms.................................................................................................................A-1
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Figures

Chapter 1

Figure 1-1: One-room schoolhouse, Christiana, DE, 1923 ........................................................1-3

Figure 1-2: High school, New York City, NY, 1929......................................................................1-3

Figure 1-3: Elementary school, Washington, DC, constructed in 1930 ....................................1-4

Figure 1-4: Typical finger plan school, 1940s .............................................................................1-5

Figure 1-5: Compact courtyard plan, 1960s................................................................................1-5

Figure 1-6: Fountain Valley High School, Huntington Beach, CA, 1964 ................................1-6

Figure 1-7: Open enclosure plan teaching area, with movable screens 

and storage, Rhode Island, 1970 ..............................................................................1-6

Figure 1-8: Typical portable classrooms, 1980s, still in use........................................................1-7

Figure 1-9: Elementary school, Fairfield, PA, 1980s...................................................................1-7

Figure 1-10: Private high school located in a remodeled industrial 

building, Palo Alto, CA .............................................................................................1-8

Figure 1-11: West High School, Aurora, IL, 2000.......................................................................1-10

Figure 1-12: Elementary school, Oxnard, CA, 2000...................................................................1-10

Figure 1-13: Design and construction process flow chart..........................................................1-13

Chapter 2

Figure 2-1: Performance-based design flow diagram ................................................................2-4

Figure 2-2: Maximum level of damage to be tolerated based on 

performance groups and magnitude of design event ............................................2-7

Figure 2-3: Relative magnitude and return period for seismic, flood, and wind events..........2-8

Chapter 3

Figure 3-1: Areas where earthquakes are likely to occur on the U.S. 

mainland. The contour lines indicate the 2-percent 

probability of exceedance of ground motion accelerations 

within each contour area (or the “odds” [2-percent] that the 

accelerations will be exceeded in a 50-year period)................................................3-3
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Figure 3-2: Basic wind speed map from ASCE 7 for Risk Category III 

and IV buildings and other structures. ASCE 7 is cited in the 

model building codes and used to select design wind speeds................................3-4

Chapter 4

Figure 4-1: School in Anchorage, AK, 1964, severely damaged by 

earthquake-induced landslide ..................................................................................4-3

Figure 4-2: States with seismic risk .............................................................................................4-5

Figure 4-3: Examples of national seismic hazard maps............................................................4-12

Figure 4-4: Representative shapes of building code (or design) response 

spectra for different soils ........................................................................................4-12

Figure 4-5: Ductility ...................................................................................................................4-13

Figure 4-6: Collapse of portion of nonductile concrete frame school 

structure, Helena, MT, 1935 ...................................................................................4-14

Figure 4-7: Modular classrooms pushed off their foundations; note 

stairs at left, Northridge, CA, 1994.........................................................................4-14

Figure 4-8: Fallen filing cabinets and shelves, Northridge, CA, 1994 .....................................4-15

Figure 4-9: Fallen shop equipment, Coalinga, CA, 1983 .........................................................4-15

Figure 4-10: Fallen light fixtures, library, Coalinga, CA, 1983...................................................4-16

Figure 4-11: Fallen heavy lath and plaster ceiling across auditorium 

seating, Northridge, CA, 1994 ................................................................................4-16

Figure 4-12: Damage to the John Muir School, Long Beach, CA, 1933 ...................................4-17

Figure 4-13: Damage to shop building, Compton Junior High School, 

Long Beach, CA, 1933.............................................................................................4-17

Figure 4-14: A dangerous passageway between two buildings, Polytechnic 

High School, Long Beach, CA, 1933......................................................................4-18

Figure 4-15: A heavy corridor lintel ready to fall, Emerson School, 

Bakersfield, Kern County, CA, 1952.......................................................................4-18

Figure 4-16: Overturned shop equipment and failed light fixtures, 

Kern County, CA, 1952............................................................................................4-19
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Figure 4-17: Destroyed exit corridor, Bakersfield, Kern County, CA, 1952 ..............................4-19

Figure 4-18: Typical school damage, Helena, MT, 1935 ............................................................4-20

Figure 4-19: The student body president was killed here by falling 

brickwork, Seattle, WA, 1949 ..................................................................................4-21

Figure 4-20: Another dangerous entry collapse, Seattle, WA, 1949 ..........................................4-21

Figure 4-21: Collapse of roof over stage, Seattle, WA, 1949.......................................................4-22

Figure 4-22: Damage to library shelving, Seattle, WA, 1949 ......................................................4-22

Figure 4-23: Severe structural damage to the West Anchorage High 

School, Anchorage, AK, 1964 .................................................................................4-23

Figure 4-24: Brittle failure at nonductile concrete column, West 

Anchorage High School, 1964................................................................................4-24

Figure 4-25: Ceiling damage, Northridge, CA, 1994..................................................................4-25

Figure 4-26: Damage to ceramic kiln, including fractured 

gas line, Northridge, CA, 1994 ...............................................................................4-26

Figure 4-27: Line of suspended light fixtures fallen on teacher’s station, 

Northridge, CA, 1994..............................................................................................4-26

Figure 4-28: Example of rapid visual screening information form...........................................4-32

Figure 4-29a: Structural and nonstructural elements of a building............................................4-46

Figure 4-29b: Structural and nonstructural elements of a building............................................4-47

Figure 4-30: Suspended ceiling and light fixture bracing and support....................................4-47

Figure 4-31: Bracing tall shelving to the structure .....................................................................4-48

Figure 4-32: Connection of nonstructural masonry wall to structure to 

permit independent movement .............................................................................4-48

Figure 4-33: Bracing for existing unreinforced masonry parapet wall .....................................4-48

Figure 4-34: Design strategies for seismic retrofit of existing buildings ...................................4-51

Figure 4-35: Retrofit of B.F. Day Elementary School, Seattle, WA ............................................4-52
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Figure 4-36: Sections and plans of the B.F. Day School: existing at bottom, 

retrofitted at top. Note that the retrofit has also opened up 

the basement and first floor to provide large spaces suitable 

for today’s educational needs ........................................................................................4-52

Chapter 5

Figure 5-1: The riverine floodplain.............................................................................................5-4

Figure 5-2: The floodplain along an open coast ........................................................................5-5

Figure 5-3: Probability and magnitude .......................................................................................5-6

Figure 5-4: Hydrostatic loads on buildings...............................................................................5-11

Figure 5-5: Hydrodynamic loads on a building or building element .....................................5-11

Figure 5-6: Definition sketch – coastal wave height and stillwater depth...............................5-16

Figure 5-7: Velocity as a function of stillwater flood depth .....................................................5-20

Figure 5-8: Riverine flood hazard zones ..................................................................................5-23

Figure 5-9: Coastal flood hazard zones.....................................................................................5-24

Figure 5-10: Sample digital FIRM format used for modernized maps......................................5-24

Figure 5-11: Illustration of the Limit of Moderate Wave Action, which 

delineates the inland limit of areas referred to as Coastal A Zones.....................5-25

Figure 5-12: Flooding caused the failure of this road bed.........................................................5-35

Figure 5-13: School bus washed away by storm surge ...............................................................5-36

Figure 5-14: Interior unreinforced masonry walls of the Port Sulphur 

High School in Louisiana were damaged by hydrostatic 

loads associated with Hurricane Katrina’s storm surge (2005) ...........................5-37

Figure 5-15: Concrete slab ruptured by hydrostatic pressure (buoyancy) 

induced by the floodwaters of Hurricane Katrina (2005) ....................................5-38

Figure 5-16: Scour undermined the foundation of St. Paul Catholic 

School, Pass Christian, LA ......................................................................................5-38
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Figure 5-17: This parquet wood gymnasium floor was damaged by 

dimensional changes due to saturation (Hurricane Katrina 2005).....................5-40

Figure 5-18: Saturation damage extends above the water line in this 

grade school in Gurnee, IL.....................................................................................5-41

Figure 5-19: Although it was anchored and not displaced by floodwaters, 

this generator was out of service after being submerged 

(Hurricane Katrina, 2005)......................................................................................5-43

Figure 5-20: Destroyed computers and peripheral equipment, Nichols 

Elementary School, Biloxi, MS ...............................................................................5-44

Figure 5-21a: Schematic of typical earthen levee .........................................................................5-49

Figure 5-21b: Schematic of typical permanent floodwall.............................................................5-50

Figure 5-22: High school in Bloomsburg, PA, elevated on fill...................................................5-53

Figure 5-23: A stemwall foundation elevates the Marion T. Academy 

above the flood level in Wilmington, DE. .............................................................5-54

Figure 5-24: School elevated on columns ..................................................................................5-54

Figure 5-25: Typical crawlspace with flood openings.................................................................5-55

Figure 5-26: Specially designed panels are mounted to block doors, 

windows, and other openings to keep water from entering the building. .........5-58

Figure 5-27: Brick facing separated from masonry wall (Hurricane Katrina, 2005)................5-60

Figure 5-28: Equipment room with watertight door ..................................................................5-62

Figure 5-29: A masonry floodwall with multiple engineered openings in 

Fargo, ND, during flooding in 2001.......................................................................5-67

Figure 5-30: Utility component elevated above flood level .......................................................5-71

Figure 5-31: Gravel-filled containers form a barrier to protect 

the University of Iowa (2008) .................................................................................5-75
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Chapter 6

Figure 6-1: Large portions of the roof coverings blew off of this school. 

Estimated wind speed: Approximately 125 to 130 miles per 

hour (mph). Hurricane Katrina (Louisiana, 2005)................................................6-2

Figure 6-2:  Hurricane-prone regions and special wind regions................................................6-3

Figure 6-3:  Average number of tornadoes per year (1953-2005) ..............................................6-5

Figure 6-4: This high school was damaged by a strong tornado 

(Plainfield, IL 1990)..................................................................................................6-6

Figure 6-5:  Basic wind speeds for Risk Category III and IV 

buildings and other structures .................................................................................6-8

Figure 6-6: Wind pressure as a function of wind speed .............................................................6-9

Figure 6-7: Relative roof uplift pressures as a function of roof geometry, 

roof slope, and location on roof, and relative positive and 

negative wall pressures as a function of location along the wall ..........................6-10

Figure 6-8: Aggregate Blow-off associated with building irregularities. 

Hurricane Hugo (South Carolina, 1989) ..............................................................6-11

Figure 6-9: The irregularity created by the stair tower (covered with a 

metal roof) caused turbulence resulting in wind speed-up 

and roof damage. Hurricane Andrew (Florida, 1992)..........................................6-11

Figure 6-10: Plan view of a portion of the building in Figure 6-9 showing 

the use of a corner uplift zone in lieu of a perimeter uplift 

zone on the low-slope roof in the vicinity of the stair tower.................................6-12

Figure 6-11: The single-ply roof membrane on this school was torn by 

a missile. The tear was still unprotected 6 days after it was 

damaged. A substantial amount of water can enter the 

building through such a tear, unless the deck is water tight 

(see Figure 6-13) or a secondary roof membrane is used as 

discussed in Section 6.3.3.8. Estimated wind speed: 105 to 

115 mph. Hurricane Ivan (Florida, 2004) .............................................................6-15
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Figure 6-12: Constructed in 1995, this school was used as a hurricane 

shelter. The large number of occupants moved from one 

area of the school to another as water entered various areas 

of the building due to envelope failures. Estimated wind 

speed: 105 to 115 mph. Hurricane Ivan (Florida, 2004) ......................................6-17

Figure 6-13: Extensive roof covering and rooftop equipment damage 

occurred on this school. However, the cast-in-place concrete 

deck kept most of the water from entering the school. 

Hurricane Andrew (Florida, 1992) ........................................................................6-18

Figure 6-14: The outer window panes were broken by aggregate from a 

built-up roof. Estimated wind speed: 104 mph. Hurricane 

Hugo (South Carolina, 1989).................................................................................6-18

Figure 6-15: Blow-off of metal wall panels allowed wind-driven rain to 

enter this school. Hurricane Frances (Florida, 2004)...........................................6-19

Figure 6-16: Collapsed unreinforced CMU wall. Hurricane Marilyn 

(U.S. Virgin Islands, 1995)......................................................................................6-19

Figure 6-17: The roof and all of the walls of a wing of this elementary 

school were blown away by a violent tornado. (Oklahoma City, 1999)................6-20

Figure 6-18: This elementary school was composed of several buildings. 

The building in the foreground collapsed and several others 

experienced significant structural damage. The buildings 

further up the hillside are residences. Hurricane Marilyn 

(U.S. Virgin Islands, 1995)......................................................................................6-20

Figure 6-19: This portable classroom was blown up against the main 

school building. Depending upon the type of exterior wall, 

an impacting portable classroom may or may not cause wall 

collapse. Hurricane Marilyn (U.S. Virgin Islands, 1995)......................................6-21

Figure 6-20: This newly-constructed gymnasium had a structural metal 

roof panel (3-inch trapezoidal ribs at 24 inches on center) 

applied over metal purlins. The panels detached from their 

concealed clips. A massive quantity of water entered the 

school and buckled the wood gym floor. Typhoon Paka (Guam, 1997)..............6-22

Figure 6-21: The entire metal deck and steel joist roof structure at this 

school’s auto shop blew off. Estimated wind speed: 105 to 

115 mph. Hurricane Ivan (Florida, 2004) ............................................................6-22
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Figure 6-22: The metal straps between this portable classroom and the 

ground anchors were not taut. This classroom is susceptible 

to being blown off the piers and to overturning. See Figure 

6-26 for a robust anchoring system ........................................................................6-23

Figure 6-23: This old school was used as a hurricane shelter. Structural 

failure did not occur during this hurricane. However, 

portions of the roof covering were blown off, rooftop 

equipment was damaged, and many windows were broken 

by aggregate from the built-up roof (red arrow). Estimated 

wind speed: 130 mph. Hurricane Katrina (Mississippi, 2005)..............................6-24

Figure 6-24: This old school was scheduled to be used as a hurricane 

shelter. Sheltering people in schools that lack sufficient 

wind and wind-borne debris resistance presents risk of 

injury or death to occupants. Hurricane Andrew (Louisiana, 1992)...................6-25

Figure 6-25: Lack of fasteners resulted in blow-off of the HVAC unit, 

which caused extensive interior water damage and 

interrupted facility use. Hurricane Marilyn (U.S. Virgin Islands, 1995) .............6-28

Figure 6-26: The cementitious wood-fiber deck panels blew off the 

overhangs and caused a progressive lifting and peeling 

of the roof membrane. Strengthening (or replacing) 

inadequately attached roof decks during a reroofing project 

is both prudent and relatively economical. Estimated wind 

speed: 120 mph. Hurricane Katrina (Mississippi, 2005).......................................6-30

Figure 6-27: Unlike the portable classroom shown in Figure 6-22, with 

the thick T-shaped plates and taut turnbuckles, this portable 

classroom has a robust anchorage to the ground. Hurricane 

Francis (Florida, 2004)............................................................................................6-33

Figure 6-28: Asphalt shingles and vinyl siding blew off of this portable 

classroom. This type of wind-borne debris can break 

unprotected glazing. Hurricane Francis (Florida, 2004)......................................6-34

Figure 6-29: This fallen tree caused minor damage to these portable 

classrooms. However, had the tree landed on the classroom 

at the left of the photograph, it could have caused injuries 

if the building had been occupied. Although portable 

classrooms are not occupied during hurricanes, they are 

frequently occupied during thunderstorms, which often 

topple trees. Estimated wind speed: 105 to 115 mph. 

Hurricane Ivan (Florida, 2004) ..............................................................................6-36
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Figure 6-30: In most of the areas on this roof, the connection of the top 

nailer to the bottom nailer was the weakest link. However, 

in a few locations, the connection of the bottom nailer to 

the roof structure was the weak link (three of the blown-off 

bottom nailers are shown by the red lines). .........................................................6-39

Figure 6-31: Illustration of load path continuity ........................................................................6-40

Figure 6-32: Dirt and vegetation surrounded this roof drain (red arrow) 

and impeded drainage. Roof drains should be checked at 

least annually and cleaned of debris if found. Drains should 

also be checked prior to hurricane landfall. Hurricane Ike 

(Texas, 2008) ...........................................................................................................6-44

Figure 6:33: Open walkways do not provide protection from wind-borne 

debris. Hurricane Katrina (Mississippi, 2005).......................................................6-46

Figure 6-34: The structure on this school was composed of light gauge 

metal framing, with a proprietary composite deck system 

composed of light gauge corrugated metal deck and gypsum 

board. In addition to the gable end wall failure, the asphalt 

shingles and underlayment were blown off at the corner of 

the eave and ridge. Estimated wind speed: 140 to 160 mph. 

Hurricane Charley (Florida, 2004) ........................................................................6-47

Figure 6-35: Even though the roof structure blew off, because of the 

strength and reliability of the screwed deck connections, the 

decking remained attached to the joists. Hurricane Charley 

(Florida, 2004).........................................................................................................6-48

Figure 6-36: View looking down at the top of a steel joist after the metal 

decking blew away. Only a small portion of the deck was well 

fused to the joist (circled area). Tornado (Oklahoma, 1999)..............................6-49

Figure 6-37: Looking down at a sidelap of a deck attached with powderdriven pins. The washer at the top pin blew through the deck............................6-49

Figure 6-38: View looking along a sidelap of a deck attached with 

powder-driven pins. The right pin does not provide 

adequate uplift and shear resistance......................................................................6-49

Figure 6-39: Portions of this waffled precast concrete roof deck were 

blown off. Typhoon Paka (Guam, 1997)................................................................6-50
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Figure 6-40: Twin-Tee roof panel lifted as a result of the combined effects 

of wind uplift and pre-tension. Tornado (Missouri, May 2003) ..........................6-51

Figure 6-41: The wind speed was sufficient to collapse this school’s 

canopy, but the speed was not high enough to blow the 

canopy debris very far. Hurricane Francis (Florida, 2004) ..................................6-51

Figure 6-42: At the school shown in Figure 6-34, wind-borne debris 

ruptured the proprietary composite deck system composed 

of light gauge corrugated metal deck and gypsum board. 

Estimated wind speed: 140 to 160 mph. Hurricane Charley 

(Florida, 2004).........................................................................................................6-53

Figure 6-43: Door sill pan flashing with end dams, rear leg, and turned-down front leg .......6-55

Figure 6-44: Drip at door head and drip with hook at head .....................................................6-55

Figure 6-45: Door shoe with drip and vinyl seal (left); neoprene door sweep (right) ............6-56

Figure 6-46: Automatic door bottom ..........................................................................................6-56

Figure 6-47: Interlocking threshold with drain pan...................................................................6-57

Figure 6-48: Threshold with stop and seal..................................................................................6-57

Figure 6-49: Adjustable jamb/head weatherstripping ...............................................................6-57

Figure 6-50: Two complete windows, including frames, blew out as a 

result of an inadequate number of fasteners. Typhoon Paka 

(Guam, 1997) ..........................................................................................................6-58

Figure 6-51: View of a typical window sill pan flashing with end dams 

and rear legs. ...........................................................................................................6-59

Figure 6-52: Protecting sealant retards weathering and reduces the 

exposure to wind-driven rain..................................................................................6-59

Figure 6-53: Plywood panels (black continuous bands) installed after 

the glass spandrel panels were broken by roof aggregate.

Estimated wind speed: 130 mph. Hurricane Katrina (Mississippi, 2005)............6-60
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Figure 6-54: The red arrow shows a piece of laminated glass that was 

broken, but remained in the frame to protect the building’s 

interior. The blue arrow shows unbroken laminated glass. 

The yellow arrows show granite wall panels. Estimated wind 

speed: 105 mph. Hurricane Katrina (Louisiana, 2005) ........................................6-61

Figure 6-55: The exterior wall stopped just above the soffit (red arrows). 

After the metal soffit panels blew away, wind-driven rain 

blew into the attic space, which saturated the fiberglass 

batt insulation and caused the ceiling boards to collapse. 

Estimated wind speed: 130 mph. Hurricane Katrina (Mississippi, 2005)............6-63

Figure 6-56: The red arrows show the original location of a CMU wall 

that nearly collapsed following a rolling door failure. 

Estimated wind speed: 140–160 mph. Hurricane Charley 

(Florida, 2004).........................................................................................................6-64

Figure 6-57: Although uncommon for schools, precast wall panels were 

attached to the structural frame of this school. This type of 

wall typically offers excellent wind performance. Note the 

roof covering damage and displaced gas line. Estimated 

wind speed: Approximately 125–130 mph. Hurricane 

Katrina (Louisiana, 2005).......................................................................................6-65

Figure 6-58: The four ties shown by the red arrows were not embedded 

into the mortar. Estimated wind speed: 105 mph. Hurricane 

Katrina, (Mississippi, 2005).....................................................................................6-66

Figure 6-59: Water leaked inside along the base of the brick veneer walls 

(red arrow). Estimated wind speed: 115 mph. Hurricane 

Katrina (Louisiana, 2005) ........................................................................................... 6-67

Figure 6-60:  Typical EIFS assemblies...........................................................................................6-67

Figure 6-61: EIFS blow-off near a wall corner. At one area, the metal 

fascia was also blown in ...........................................................................................6-68

Figure 6-62: At this EIFS failure, the screws attaching the gypsum board 

(yellow colored material) were too far apart (red circle). 

Additionally, at the board joint, the screws were too close to 

the board edge (blue circle). In this area, the screws were 

spaced at 41⁄2, 4, 6, 6, 9, and 91⁄2 inches on center. Also, the 

adhesive between the gypsum board and MEPS was applied 

in rows rather than continuously over the gypsum board. 

Estimated wind speed: 120 mph. Hurricane Katrina (Mississippi, 2005)............6-68
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Figure 6-63: The stucco wall failure was caused by inadequate attachment 

between the stud tracks and the building’s structure. All of 

the metal stud framing within the red circle blew away. The 

arrow shows a bottom stud track that detached and pulled 

away from the building. Estimated wind speed: 110–125 

mph. Hurricane Ivan (Florida, 2004) ....................................................................6-69

Figure 6-64: The loss of metal wall panels allowed a substantial amount 

of wind-driven rain to penetrate into the classroom. 

Estimated wind speed: 105–115 mph. Hurricane Ivan 

(Florida, 2004).........................................................................................................6-70

Figure 6-65: Blow-off of metal fascia panels due to inadequate 

attachment of wood furring to the CMU wall. Estimated 

wind speed: 85–95 mph. Hurricane Ivan (Florida, 2004).....................................6-71

Figure 6-66: This cement fiber siding was attached with blind nails (red 

circle). Because of the high design wind speed, face nails 

should have been used (blue circle). Hurricane Francis 

(Florida, 2004).........................................................................................................6-72

Figure 6-67: Three of the panel ribs opened up (one to the right of the 

blue arrow and two to the left). The LPS conductor serving 

the air terminal (red arrow) ran underneath the ridge 

flashing. Estimated wind speed: 105–115 mph. 

Hurricane Ivan (Florida, 2004) ..............................................................................6-75

Figure 6-68: The blown off insulation (red arrow) may have initiated 

blow-off of the roof membrane. Estimated wind speed: 105–

115 mph. Hurricane Ivan (Florida, 2004) .............................................................6-77

Figure 6-69: The orientation of the membrane fastener rows led to blowoff of the steel deck. Hurricane Marilyn (U.S. Virgin Islands, 1995)...........................6-78

Figure 6-70: The ink pen shows an opening that the wind can catch to 

cause lifting and peeling of the membrane...........................................................6-79

Figure 6-71: The metal edge flashing on this building disengaged 

from the continuous cleat and the vertical flange lifted. 

Hurricane Hugo (South Carolina, 1989) ..............................................................6-80

Figure 6-72: The coping blew off because of inadequate attachment of 

the cleats. Estimated wind speed: 92 mph. Hurricane Ike 

(Texas, 2008) ...........................................................................................................6-80
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Figure 6-73: Both vertical faces of the coping were attached with exposed 

fasteners instead of concealed cleats. Typhoon Paka (Guam, 1997) ...................6-81

Figure 6-74:  Because this gutter was not attached to the bracket, wind 

lifted the gutter along with the metal edge flashing that 

lapped into the gutter. Bracket fasteners are indicated by the 

red arrows. Hurricane Francis (Florida, 2004)......................................................6-82

Figure 6-75:  The original modified bitumen membrane was blown away 

after the gutter lifted in the area shown by the red arrow 

(the black membrane is a temporary roof). 

Hurricane Francis (Florida, 2004) .........................................................................6-82

Figure 6-76: At this gutter, a fastener connected the bracket to the gutter. 

Note: To avoid leakage at the fasteners between the bracket 

and gutter, the bracket should extend near or to the top of 

the gutter so that the fastener would be above the waterline. 

Estimated wind speed: 95 mph. Hurricane Ike (Texas, 2008) .............................6-83

Figure 6-77: Sheet metal straps were attached to an existing gutter that 

lacked sufficient uplift resistance. ..........................................................................6-84

Figure 6-78: Blow-off of this downspout resulted in glazing breakage. 

Estimated wind speed: 105–115 mph. Hurricane Ivan 

(Florida, 2004).........................................................................................................6-85

Figure 6-79: If mechanically attached base flashings have an insufficient 

number of fasteners, the base flashing can be blown away. 

Hurricane Andrew (Florida, 2004) ........................................................................6-85

Figure 6-80: The secondary membrane prevented significant leakage into 

the building after the copper roof blew off. Hurricane Andrew (Florida, 1992)6-87

Figure 6-81: Although a missile cut into the SPF, the roof was still 

watertight. The ink pen (blue arrow) shows the relative 

size of the impact area. Estimated wind speed: 110 mph. 

Hurricane Ike (Texas, 2008)...................................................................................6-88

Figure 6-82:  Significant interior water damage and facility interruption 

occurred after the standing seam roof blew off. Hurricane 

Marilyn (U.S. Virgin Islands, 1995)........................................................................6-89

Figure 6-83: Brittle roof coverings, like slate and tile, can be broken by 

missiles, and tile debris can break other tiles. Estimated wind 

speed: 140–160 mph. Hurricane Charley (Florida, 2004)....................................6-90
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Figure 6-84  These wire-tied tiles were installed over a concrete deck. 

The failure was attributed to lack of vertical restraint, which 

allowed the tiles to lift and then be broken when they 

slammed back down onto the deck. Typhoon Paka 

(Guam, 1997) ..........................................................................................................6-91

Figure 6-85:  This mechanically attached single-ply membrane 

progressively tore after being cut by wind-borne debris. 

Hurricane Andrew (Florida, 1992) ........................................................................6-91

Figure 6-86: A continuous peel-stop bar over the membrane may prevent 

a catastrophic progressive failure if the edge flashing or 

coping is blown off. (Modified from FEMA 55, 2000)..........................................6-92

Figure 6-87: Several rubber walkway pads were blown off the single-ply 

membrane roof. Estimated wind speed: 130 mph. Hurricane 

Katrina (Mississippi, 2005)......................................................................................6-93

Figure 6-88: Base flashing protected by metal wall panels attached with 

exposed screws. Estimated wind speed: 120 mph. Hurricane 

Katrina (Mississippi, 2005)......................................................................................6-93

Figure 6-89: This gooseneck was attached with only two small screws. 

Emergency repairs had not been made at the time this 

photograph was taken, which was 5 days after the hurricane 

struck. A substantial amount of water was able to enter the 

school. Hurricane Francis (Florida, 2004) ...........................................................6-94

Figure 6-90: Although this 18,000-pound HVAC unit was attached to 

its curb with 16 straps, it blew off the building during 

Hurricane Ivan. (Florida, 2004) ............................................................................6-95

Figure 6-91: The gooseneck on this building remained attached to the 

curb, but the curb detached from the deck. Typhoon Paka 

(Guam, 1997) ..........................................................................................................6-97

Figure 6-92: Cowlings blew off two of the three fans. Note also the loose 

LPS conductors and missing walkway pad (red arrow). 

Estimated wind speed: 140–160 mph. Hurricane Charley 

(Florida, 2004).........................................................................................................6-98

Figure 6-93: Cables were attached to prevent the cowling from blowing 

off. Typhoon Paka (Guam, 1997)...........................................................................6-98
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Figure 6-94: These condensers were blown off their sleepers. Displaced 

condensers can rupture roof membranes and refrigerant 

lines. Estimated wind speed: 120 mph. Hurricane Katrina 

(Mississippi) ............................................................................................................6-99

Figure 6-95: This condenser had supplemental attachment straps (see 

red arrows). Typhoon Paka (Guam, 1997) ............................................................6-99

Figure 6-96: Failure of vibration isolators that provided lateral resistance 

but no uplift resistance caused equipment damage. A 

damaged vibration isolator is shown in the inset. Estimated 

wind speed: 120 mph. Hurricane Katrina (Mississippi, 2005)............................6-100

Figure 6-97: Guyed flue blew over (red arrow indicates one of the guys). 

Estimated wind speed: 92 mph. Hurricane Ike (Texas, 2008) ...........................6-101

Figure 6-98: The school shown in Figure 6-63 also had an access panel 

blow off. Blown-off panels can puncture roof membranes, 

break glazing, and cause injury. Estimated wind speed: 85–

95 mph. Hurricane Ivan (Florida, 2004) .............................................................6-101

Figure 6-99: The school shown in Figures 6-64 and 6-98 also experienced 

gas line rupture (shown by the lines dangling over the 

side of the building). Estimated wind speed: 85–95 mph. 

Hurricane Ivan (Florida, 2004) ............................................................................6-102

Figure 6-100: At a periodic gas line support on this roof, a steel angle 

was welded to a pipe that was anchored to the roof deck. A 

strap looped over the gas line and was bolted to the support 

angle. Such a connection provides resistance to 

lateral and uplift loads. .........................................................................................6-102

Figure 6-101: These two condensate drain lines detached from their 

HVAC units. They had not been anchored to the roof. 

Estimated wind speed: 125 mph. Hurricane Katrina (Mississippi, 2005)..........6-103

Figure 6-102: Equipment screen panels can puncture roof membranes, 

break glazing, and cause injury. Estimated wind speed: 105–

115 mph. Hurricane Ivan (Florida, 2004) ...........................................................6-104

Figure 6-103: This exhaust fan was impacted by wind-borne debris. 

Although it is often impractical to place all equipment such 

as fans in penthouses, doing so to the extent possible avoids 

debris damage. Estimated wind speed: 130 mph. Hurricane 

Katrina (Mississippi, 2005) ...................................................................................6-105
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Figure 6-104: Leaf debris and ponding near a scupper (red and blue 

arrows). The yellow arrow indicates a piece of coping that 

blew off an upper roof shown in Figure 6-71. Estimated wind 

speed: 92 mph. Hurricane Ike (Texas, 2008) ......................................................6-106

Figure 6-105: Collapsed light fixtures caused by severe corrosion (see 

inset). Estimated wind speed: 105–115 mph. Hurricane Ivan 

(Florida, 2004).......................................................................................................6-107

Figure 6-106: The collapse of the antenna tower at this school caused 

progressive peeling of the roof membrane. Also note that 

the exhaust fan blew off the curb, but the high parapet kept 

it from blowing off the roof. Hurricane Andrew (Florida, 1992) ......................6-108

Figure 6-107:  Common anchoring method for satellite dish. Estimated 

wind speed: 85–95 mph. Hurricane Ivan (Florida, 2004) ..................................6-109

Figure 6-108: A satellite dish anchored similarly to that shown in Figure 

6-106 was blown off this five-story building. Estimated wind 

speed: 140–160 mph. Hurricane Charley (Florida, 2004)..................................6-109

Figure 6-109: An air terminal (red arrow) debonded from the roof. 

Even though the school had a tough membrane (modified 

bitumen), the displaced air terminal punctured the 

membrane in two locations (blue arrows). 

Hurricane Charley (Florida, 2004) ......................................................................6-110

Figure 6-110: View of an end of a conductor that became disconnected. 

Estimated wind speed: 130 mph. Hurricane Katrina 

(Mississippi, 2005) ................................................................................................6-110

Figure 6-111: This conductor connector was adhered to the coping. 

The conductor deformed the connector prongs under wind 

pressure, and pulled away from the connector. Estimated 

wind speed: 130 mph. Hurricane Katrina (Mississippi, 2005)............................6-111

Figure 6-112: This conductor was attached to the coping with a looped 

connector. Estimated wind speed: 130 mph. Hurricane 

Katrina (Mississippi, 2005)....................................................................................6-112

Figure 6-113:  Plan showing conductor attachment ...................................................................6-112

Figure 6-114: Use of intermittent membrane flashing strips to secure an 

LPS conductor, as illustrated in Figure 6-113 .....................................................6-113
xxx DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

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Figure 6-115: Adhesively attached conductor connector that does 

not use prongs.......................................................................................................6-113

Figure 6-116: If conductors detach from the roof, they are likely to 

pull out from pronged splice connectors. Estimated wind 

speed: 90–100 mph. Hurricane Charley (Florida, 2004)....................................6-114

Figure 6-117: Bolted splice connectors are recommended to prevent free 

ends of connectors from being whipped around by wind. 

Estimated wind speed: 130 mph. Hurricane Katrina 

(Mississippi, 2005).................................................................................................6-115

Figure 6-118: In lieu of permanent on-site emergency generators, 

portable generators can be an economical way to provide 

electrical power to schools used as hurricane recovery 

centers. Estimated wind speed: 108 mph. Hurricane Ike 

(Texas, 2008) .........................................................................................................6-116

Figure 6-119: The tree shown by the red line nearly fell on the emergency 

generator (red arrow). Estimated wind speed: 110 mph. 

Hurricane Ike (Texas, 2008).................................................................................6-117

Figure 6-120: The roof and a portion of the EIFS on this 5-year-old 

building blew off. Water leaked into the floor below. The 

floor was taken out of service for more than a month. 

Estimated wind speed: 130 mph. Hurricane Katrina 

(Mississippi, 2005).................................................................................................6-119

Figure 6-121 The cementitious wood-fiber deck panels blew off of much 

of the overhang at this school. Deck panel failure resulted 

in lifting and peeling of the roof system over a large area, 

exposure of the decking in the area shown by the blue 

arrows, and extensive interior water infiltration. Estimated 

wind speed: 105–115 mph. Hurricane Ivan (Florida, 2004)...............................6-121

Figure 6-122: The steel truss superstructure installed on this school as part 

of a steep-slope conversion blew away because of inadequate 

attachment. Hurricane Marilyn (U.S. Virgin Islands, 1995) ..............................6-122

Figure 6-123: Wind pressure caused the window frames on the upper 

floors to fail (red arrow). Estimated wind speed: 130 mph. 

Hurricane Katrina (Mississippi, 2005) .................................................................6-123
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS xxxi

TABLE OF CONTENTS

Figure 6-124: On-site water-spray testing in accordance with ASTM E 1105 

can be used to evaluate wind-driven rain resistance. Older 

window assemblies such as the ones at this school are often 

quite susceptible to leakage. Estimated wind speed: 125 

mph. Hurricane Katrina (Mississippi, 2005) .......................................................6-124

Figure 6-125: This school has accordion shutters. Estimated wind 

speed: 105–115 mph. Hurricane Ivan (Florida, 2004)........................................6-125

Figure 6-126: A metal panel shutter. Hurricane Georges (Puerto Rico, 1998) .......................6-125

Figure 6-127: Polycarbonate shutters were temporary screwed to the doors 

and wall adjacent to the window opening. An advantage of 

polycarbonate is its translucence, which allows daylight to 

enter the building without removing the shutters. Hurricane 

Francis (Florida, 2004)..........................................................................................6-126

Figure 6-128: This school has roll-down shutters. The toggle in the red 

circle allows the shutter to be manually raised. Estimated 

wind speed: 130–140 mph. Hurricane Charley (Florida, 2004).........................6-126

Figure 6-129: Collapsed unreinforced masonry parapet. Greensburg 

Tornado (Kansas, 2007)........................................................................................6-127

Figure 6-130: View of a 5-foot by 5-foot negative pressure chamber used to 

evaluate roof system uplift resistance...................................................................6-128

Figure 6-131: The built-up roof on this school was blown off after a few of 

the rotted wood planks detached from the joists. Estimated 

wind speed: 120 mph. Hurricane Katrina (Mississippi, 2005)............................6-129

Figure 6-132: The nailer (red arrow) blew off an upper roof and landed 

on the roof below. The nailer was anchored to a brick wall. 

Some of the anchors pulled out of the brick, and some 

of the bricks blew away with the nailer. Estimated wind 

speed: 105–115 mph. Hurricane Ivan (Florida), 2004........................................6-130

Figure 6-133: Failed base flashing adhered directly to the brick parapet. 

Estimated wind speed: 105 mph. Hurricane Katrina (Louisiana, 2005) ...........6-130
xxxii DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

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Figure 6-134: During a reroofing project a slot was cut in the plywood 

deck in order to allow air to flow from the attic to a new 

continuous ridge vent. The cutting depth of the saw was not 

adjusted for the thickness of the deck. The top 11⁄2 inch of 

each truss and a portion of the metal nailing plate 

was inadvertently cut. ............................................................................................6-131

Figure 6-135: To strengthen attachment of this HVAC unit, robust pipe 

anchors were attached to the deck and cables with 

turnbuckles installed.............................................................................................6-132

Figure 6-136: At this school, the hood on this HVAC unit was inadequately 

attached. A strap between the hood and unit can be 

economically installed to avoid this problem. Estimated 

wind speed: 110 mph. Hurricane Ike (Texas, 2008) ...........................................6-132

Figure 6-137: These condensers were simply mounted on wood sleepers 

that rested on the roof surface. Note the damaged exhaust 

stacks and missing rain caps (red oval). Estimated wind 

speed: 105 mph. Hurricane Katina (Mississippi, 2005) ......................................6-133

Figure 6-138: Two large openings (red rectangle and inset) through the 

roof were left after the ductwork blew away. Estimated wind 

speed: 130 mph. Hurricane Katrina (Mississippi, 2005).....................................6-134

Figure 6-139: The antenna collapsed and was whipped back and forth 

across the roof membrane. Hurricane Andrew (Florida, 1992) ........................6-135

Figure 6-140: Greensburg Tornado (Kansas, 2007) ...................................................................6-136

Figure 6-141: A violent tornado showered the roof with missiles (Oklahoma, 1999) .............6-136

Figure 6-142:  Frequency of recorded EF3, EF4, and EF5 tornadoes (1950–1998)..................6-137

Figure 6-143 : Unreinforced masonry walls and hollow-core concrete roof 

planks collapsed. Enterprise Tornado (Alabama, 2007).....................................6-139
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS xxxiii

TABLE OF CONTENTS

Tables

Chapter 2

Table 2-1: Combinations of structural and nonstructural seismic performance..................2-12

Chapter 3

Table 3-1: HAZUS-MH earthquake, hurricane, and flood losses (all 

values are in $1,000s—2002 valuation)....................................................................3-8

Table 3-2: HAZUS-MH estimated losses by percentage of school 

building and contents inventory ..............................................................................3-9

Table 3-3: Multihazard design system interactions ................................................................3-12

Chapter 4

Table 4-1: Known historic (1558–1989) earthquakes in 47 U.S. States.................................4-10

Table 4-2: School seismic safety evaluation checklist..............................................................4-33

Table 4-3: Roofing maintenance and repair/re-roofing ........................................................4-54

Chapter 5

Table 5-1: ASCE/SEI 24 provisions related to the elevation of schools................................5-33

Table 5-2: Classes of flood damage-resistant materials...........................................................5-59

Table 5-3: Checklist for building vulnerability of floodprone schools..................................5-77

Chapter 6

Table 6-1:  Number of #12 screws for base case attachment of rooftop equipment .............6-96

Table 6-2:  Checklist for building vulnerability of schools exposed to high winds..............6-140

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 1-1

An Overview of

the School Design and

Construction Process

1

1.1 Introduction

T his chapter presents an overview of the school building to provide 

a context for the chapters that follow. Every building is unique and 

school designs vary greatly; however, the purpose of schools, their 

occupancy, their economic basis, and their role in society dictate certain 

common features that distinguish them from other building types.

A summary of the national public school inventory is also presented (i.e., 

the number of students housed and the number of schools included) 

and projections of future needs are outlined. The sections that follow 

describe school design of the past, because many older schools are still in 

use and must be renovated periodically to meet today’s needs, and current school design with some trends and ideas that might influence the 

design of future schools. 
1-2 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

1 AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS

1.2 School Construction: The National Picture

I

n 2005, the estimated value of the nation’s public school inventory 

was well over $361.6 billion.1

 In 2009, of the almost 98,800 public elementary and secondary schools, 31 percent were located in small 

towns and rural areas and served 43 percent of the students, while 69 

percent were located in cities and suburban areas and served 57 percent 

of the students (U.S. Department of Education, 2009).

The total number of schools in the U.S. increased by 10,600 between 1997 

and 2007 (U.S. Department of Education, 2009). More than half of all 

schools are at least 40 years old and, even with minor renovations, many 

have passed their prime in terms of adaptability to 

modern teaching methods and tools (e.g., computers, in-class electronic information displays, and 

group learning activities). Almost all States require 

school facilities to be replaced with new construction once renovation costs reach a specified level 

(usually 60 percent).2

 Estimates from the late 1990s 

indicated approximately $100 to over $300 billion would be needed to 

bring our nation’s schools up to conditions considered to meet thencurrent standards. 

In 2001, the decade-long growth in kindergarten to grade 12 (K–

12) new school construction peaked while deferred maintenance 

and poor construction quality of many post-World War II schools 

resulted in a huge renovation demand. From 1999 through 2008, 

the National Clearinghouse for Educational Facilities reported that 

$298.16 billion was spent on the construction of nearly 15,000 elementary, middle, and high schools (National Clearinghouse for 

Educational Facilities, 2010). 

1.3 Past School Design

Schools are typically in use for long periods of time. As a result, 

even today, instruction continues in facilities that were designed 

and constructed at the beginning of the 20th century. Early 20thcentury school design was based on late 19th-century models and few 

design changes were implemented until after World War II. Schools 

ranged from one-room rural school houses to major symbolic civic 

1 Conservative estimate based upon elementary and secondary school averages developed 

with the help of Paul Abramson, President of Stanton Leggett & Associates, Education 

Consultants.

2 Use of this estimate as a decision tool was developed by Basil Castaldi, Education Facilities, 

Planning, Modernization and Management (1994).

The purpose of schools, their occupancy, 

their economic basis, and their role in society dictate certain common features that 

distinguish them from other building types.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 1-3

AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS 1

structures in large cities (Figures 1-1 and 1-2). Many inner city schools 

were more modest, inserted into small sites on busy streets and constrained by budget limitations (Figure 1-3).

The typical city school was one to three stories in height and consisted of 

rows of classrooms on either side of a wide, noisy corridor lined with metal lockers. Typical outdoor recreational areas were asphalt play courts 

and rooftops. The larger schools sometimes had libraries, special rooms 

for art, science, and shop, and auditoriums.

The construction surge to meet the demands of the post-war baby boom 

was primarily a suburban development. Much larger sites were available, 

buildings were one or two stories in height, auditoriums became multiuse facilities, and large parking lots appeared. 

Figure 1-1:

One-room schoolhouse, 

Christiana, DE, 1923

Figure 1-2:

High school, New York 

City, NY, 1929
1-4 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

1 AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS

Despite the growth of suburban construction, the fundamental design 

with classrooms along double-loaded corridors did not change very 

much. However, in warm climates, the one-story “finger plan” school, 

typically constructed of wood and a small quantity of steel, was both 

economical and less institutional in feel. For this design, the noisy double-loaded corridor is replaced by a covered walkway, often open to the 

air, with the classrooms on one side and a grassed court on the other 

(Figure 1-4). The cross-section diagram in Figure 1-4 shows the simple 

and effective means this configuration allowed for day lighting and ventilation. Compact versions of these plans appeared as schools became 

larger and sites smaller (Figure 1-5). 

Historically, inner-city high schools have been large facilities, housing 

2,000 to 3,000 students (Figure 1-6). In the 1960s and 1970s, educational methods such as team teaching prompted large open classrooms 

with poor acoustics (Figure 1-7). Some of these new large high schools 

were built as air-conditioned enclosures, with many windowless classrooms, in buildings that resembled the shopping malls that were 

replacing the main street retail centers (Figure 1-7). At the same time, 

many schools were expanded by adding classrooms to accommodate 

increasing enrollments. Although portable classrooms were originally 

intended as temporary space, many are now used as permanent classrooms (Figure 1-8). 

Figure 1-3: 

Elementary school, 

Washington, DC, 

constructed in 1930
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 1-5

AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS 1

Figure 1-4: 

Typical finger plan 

school, 1940s

Figure 1-5: 

Compact courtyard 

plan, 1960s
1-6 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

1 AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS

Gym

Lockers

Dining

Shops

Drafting

Music

Administration

Amphitheater

Social

Science

Library

English

Language

Science

Math

Math

Business

Education

Home

Economics

and Art

Figure 1-6: 

Fountain Valley High 

School, Huntington 

Beach, CA, 1964

Figure 1-7: 

Open enclosure plan 

teaching area, with 

movable screens and 

storage, Rhode Island, 

1970
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 1-7

AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS 1

Schools built in the 1980s and 1990s assumed a wide variety of forms, 

often combining classrooms into clusters and focusing on providing an 

attractive learning environment (Figure 1-9). However, demographic 

needs, shortage of affordable land, and limited construction budgets 

also resulted in some conversions of existing buildings not originally intended for educational purposes (Figure 1-10). Note the exterior 

cross bracing for the converted industrial building in Figure 1-10. The 

building required extensive retrofitting to meet California’s seismic requirements for schools.

Figure 1-8: 

Typical portable 

classrooms, 1980s, still 

in use

Figure 1-9: 

Elementary school, 

Fairfield, PA, 1980s
1-8 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

1 AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS

1.4 Present School Design

At the beginning of the 21st century, evolving social, economic, 

and educational concerns prompted a number of changes in 

school design. New design goals have begun to emerge, though 

some of the following have always been considered:

n The building should provide for health, safety, and security.

n The learning environment should enhance teaching and learning 

and accommodate the needs of all learners.

n The learning environment should serve as a center for the community.

n The learning environment should result from a planning/design 

process that involves all stakeholders.

n The learning environment should allow for flexibility and adaptability to changing needs.

n The learning environment should make effective use of all available 

resources.

These goals have lead, in turn, to a number of current design principles, 

including:

n Design for protection against natural hazards

n Design with increased attention to occupant security

n Design with increased use of day lighting and comfort control

n Design for durability 

Figure 1-10: 

Private high school 

located in a remodeled 

industrial building, Palo 

Alto, CA
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 1-9

AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS 1

n Long-life/loose-fit approach: design for internal change and 

flexibility

n Design for sustainability (also referred to as environmentally friendly 

construction, green construction, and green building) 

Some new schools already respond to these needs and, indeed, their 

originators, school districts, communities, and designers are among 

those defining school design for the future. Some of the changes are the 

result of ideology and analysis. Other changes reflect efforts to provide 

an improved learning environment and enhanced learning resources 

in an economy with increasingly limited funding for school construction. Some school districts will be faced with having to provide a minimal 

learning environment with buildings of the utmost simplicity, while meeting the requirements for health, safety, and security.

In recent years, building methods that recognize “green” building practices for both new construction and renovation have become increasingly 

available. One example is the California Green Building Standards Code, 

which became effective in August 2009 (California Building Standards 

Commission, 2009). As interest in sustainability increases and more 

school districts seek to implement various aspects of green building 

design, construction, and maintenance practices, design professionals 

are incorporating new approaches to make buildings more energy efficient and sustainable with respect to impacts on the environment. These 

approaches are already having a significant influence on building construction, and are likely to have greater influence as proven, innovative 

designs are incorporated into regular practice. A wealth of guidance on 

green design and construction practices that is specific to schools—both 

for new construction and renovations—is being developed, and rating 

systems are being strengthened and utilized to better guide those involved in the process to more sustainable solutions. 

1.5 Future School Design

Schools will continue to vary widely in size. However, even in many 

suburban areas suitable land has become increasingly scarce and 

expensive. Sprawling one-story campuses will become less common and more schools will be more compact and multi-story (Figure 

1-11). The desire for more humanistic environments and the rejection 

of traditional school plans will likely result in more imaginative and 

more complex layouts (Figure 1-12), while the move to re-populate inner cities may result in the construction of dense and compact schools. 

Despite evidence of a trend towards larger buildings, many educational 

researchers believe that students improve their learning skills best in 

smaller schools. 
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1 AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS

Although constructing more small schools may 

be economically unrealistic, methods of organization are being explored that provide some 

of the benefits of small size within a large physical complex. Some schools are organized into 

“learning academies” for each grade, with classrooms that can expand and contract, along with 

other activity rooms of various sizes. 

Other researchers believe that the conventional library will disappear. The trend in many new 

schools is for the library to take the form of a 

multi-media center and material collections, including laptop computers that are distributed 

from mobile units to “classroom clusters.” 

Schools are increasingly seen as community 

resources that go beyond their primary educational functions. Adult education and community 

events now take place on evenings, weekends, and throughout traditional vacation periods. These uses provide affordable means to enhance 

community service resources by maximizing a facility’s utilization.

There is a growing awareness of the importance of recognizing natural 

hazards that may affect schools. The likelihood of earthquakes, floods, 

hurricanes, and tornadoes will continue to be, at some locations, a source 

of worry and fear. Aside from protecting students, schools in earthquakeprone regions are often used as post-earthquake shelters and schools 

in hurricane- and tornado-prone regions are also used as shelters. In 

California, the State’s Field Act, enacted in 1933 following the Long 

Beach earthquake, requires public schools to be designed by a licensed 

architect or engineer and the Department of the State Architect is required to check plans and inspect construction. Elsewhere, floods and 

high winds occur with sufficient frequency that resistance to their effects 

must be addressed by knowledgeable designers and good construction 

practices. 

Figure 1-11: 

West High School, 

Aurora, IL, 2000

Figure 1-12: 

Elementary school, 

Oxnard, CA, 2000
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 1-11

AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS 1

1.6 The Design and Construction Process

Certain basic steps are necessary and certain basic procedures must 

be followed for any school construction program. The actual procedures followed will vary greatly in scope between the design of 

a single small elementary school and the development of a multi-school 

program that involves both new and remedial construction. Review 

and regulation procedures by outside agencies will also vary. Internal 

decisions by a school district regarding the design and construction 

process (e.g., conventional architect design and 

competitive construction bid, design/build, or 

construction manager) will affect the scope and 

timing of some of the activities.

Regardless of the size and scope of a project, a number of planning steps should be taken by school 

districts and their design teams. For a small project, 

the steps may entail relatively informal meetings 

among a few district staff, the school board, and 

others. For a larger program, formal procedures should be established 

to include the following steps.

n Conduct an in-house assessment of the educational needs, often 

with the assistance of a public education committee and consultants. 

Contributions of the committee continue throughout the programming and design process, and may involve acquiring input from 

specialists as necessary at different stages for a large program.

n Determine the size and scope of the proposed program. (In a small 

district, an architect may be employed to assist the school district 

with this task; the architect may later become the design architect.)

n Conduct a siting assessment to determine the size and availability 

of sites (and lease/purchase as necessary) and to identify avoidable 

site constraints such as the presence of flood hazard areas, wetlands, 

and steep slopes.

n Develop educational specifications by in-house staff and/or 

consultants.

n Conduct a financial assessment. 

n Identify financial resources, including alternative sources of funding (e.g., State and Federal programs, local taxes, bond issues).

n Ensure funding is made available (e.g., obtain State grants or pass 

bond issue).

Many of the steps in the design and construction process are appropriate when 

evaluating existing schools for proposed 

renovation. Specific factors to consider 

when evaluating seismic, flood, and wind 

hazards at existing schools are described 

in this design guide.
1-12 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

1 AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS

n Appoint district building program management staff (appointed officials or a committee). 

n Determine the design and construction process (i.e., conventional 

design and bid, design/build, or construction management).

n Select and hire architects and other special design consultants or design/build team members; the timing of hiring will vary depending 

on the number of projects, whether programming is involved, and 

other variables.

n Develop building programs, including building size, room size, 

equipment, and environmental requirements; this may be done by inhouse staff and/or architects or independent program consultants. 

n Appoint a district staff and public stakeholders committee for the 

design phase. 

n Develop designs (architects) and cost estimates. Hold public meetings with architects and encourage public input into the design; 

conduct district progress reviews.

n Complete design and conduct district review of contract documents.

n Submit construction documents to permitting agencies for review 

and approval.

n Submit documents to building department and other required 

agencies.

n Select the contractor (bidding) or finalize design/build or construction management contracts.

n Begin school construction.

n Administer construction contract.

n Initiate architect observations and inspections as required.

n Complete school construction.

n Obtain occupancy permit from the building department.

n Obtain architect acceptance.

n Obtain school district acceptance.

n Commission and occupy school. 

The sequence of the above steps may vary, depending on the complexity of the program, and some steps may be implemented simultaneously. 

The flow chart in Figure 1-13 illustrates the typical process and identifies 

how specific activities related to design for natural hazards fit into the 

general planning and design process.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 1-13

AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS 1

Site/Availability Assessment Size and Scope of 

Construction

Financial Needs Assessment

Multihazard Assessment

Study Relevant Hazards

Acceptable Risk, Performance 

Levels, Cost

Develop Educational 

Specifications

Appoint District Program 

Management Staff

Determine Design and 

Construction Process

Identify Financial Sources

Ensure Financing

Select Architect

Design, Cost Estimates, 

Reviews

Design Completion 

Construction Documents Permitting Submission

Public Education Committee 

Formation

Educational Needs 

Assessment

Hazard/Security Committee 

Formation

Develop Building Programs

Appoint Staff/Public 

Committee

Contractor Selection

Construction Administration

Accept and Commission

Architect Observation

Architect Accept

Construction

Completion and Occupancy

Hazard Information to

Design Team

Figure 1-13: Design and construction process flow chart
1-14 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

1 AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS

1.7 References

Castaldi, Basil, 1994. Education Facilities, Planning, Modernization and 

Management, Fourth edition, Boston, MA: Allyn & Bacon.

California Building Standards Commission, 2009. 2008 California Green 

Building Standards Code, Sacramento, CA, January 2009.

National Clearinghouse for Educational Facilities, U.S. K-12 School 

Construction Data 1999–2008, http://www.ncef.org/cd/School-Construction-Data-1999-2008.pdf, accessed April 21, 2010, citing McGraw-Hill 

Construction Data 1998–2008.

U.S. Department of Education, 2009. The Digest of Education Statistics, 

2008, National Center of Education Statistics, Washington, DC, March 

18, 2009.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 2-1

Performance-Based 2Design

The term “performance,” as it relates 

to exposure to natural hazards, usually 

refers to a building’s condition after 

a disaster, i.e., it signifies a level of 

damage expected or a load that can be 

resisted. 

2.1 Background

T he model building codes define the minimum design requirements to ensure the safety of occupants during specific design 

events. Recent natural disasters have prompted recognition that 

significant damage can occur even when buildings are compliant with 

the building code. Many critical facilities, including school buildings, 

are closed after natural disasters, even if damage is relatively minor, suggesting that satisfying the minimum code criteria may not be sufficient 

to ensure continued functionality. Communities also depend on school 

buildings to provide reliable shelter and critical services. In order to meet 

that need, school buildings should be designed 

and constructed according to criteria that result in 

continued and uninterrupted functionality. 

Building performance is an indicator of how well 

a structure supports the defined needs of its users. 

Acceptable performance indicates acceptable (or 

tolerable) levels of damage or condition that allow 
2 PERFORMANCE-BASED DESIGN

2-2 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

uninterrupted facility operation. Consequently, performance-based design is the process or methodology used by design professionals to create 

buildings that protect functionality and the continued availability of 

services. 

The performance-based design approach is not proposed as an immediate substitute for design to traditional codes. Rather, it can be viewed as 

an opportunity to enhance and tailor the design to match the objectives 

of the community’s stakeholders. For a school project, the stakeholders 

include everyone who has an interest in the successful completion of 

a school project (i.e., the school board members, responsible officials, 

members of the design team, the builders, the community at large, parents, and code enforcement officials). The design team is made up of the 

architects, engineers, and other design professionals and consultants.

Performance-based codes define acceptable or tolerable levels of risk 

for a variety of health, safety, and public welfare issues. Currently, codes 

include the International Code Council Performance Code for Buildings and 

Facilities (ICC PC) produced by the International Code Council (ICC, 

2009), and the NFPA 5000. Building Construction and Safety Code (NFPA, 

2009) and NFPA 101: Life Safety Code (NFPA, 2008) produced by the 

National Fire Protection Association (NFPA). The ICC PC addresses all 

types of building issues, while the provisions of NFPA 101, “PerformanceBased Option,” address only issues related to “life safety systems.” NFPA 

5000 sets forth both performance and prescriptive options for design 

and construction.

The various prescriptive building, fire, and life safety codes all contain 

provisions for what is known as “alternative methods and materials” or 

“equivalency.” These provisions allow for the use of methods, equipment, or materials not specified or prescribed in the code, provided 

the alternative is approved by the code official. A performance-based 

design approach can be employed under these provisions. While the 

“alternative methods and materials” clause of the prescriptive codes 

allows the use of performance-based design procedures, the 2010 edition of the American Society of Civil Engineers (ASCE) Standard 7, 

Minimum Design Loads for Buildings and Other Structures, addresses performance-based design when the standard is used directly, without 

reference from a building code. 

Within ASCE 7-10, “Performance-based Procedures” represent one of 

three approaches for design. Under the performance-based approach, 

both structural and nonstructural components and their connections 

must be shown to provide a reliability not less than that expected under 

the approach referred to as the “strength procedures.” A combination 
PERFORMANCE-BASED DESIGN 2 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 2-3

of testing and analysis can be used to demonstrate the achievement of 

target reliability that is described in the Commentary that accompanies ASCE 7. Factors that affect target reliability include Risk Category 

(or Occupancy Category), extent of structural failure, and whether 

loading conditions include or exclude earthquake. 

In 2006, FEMA published FEMA 445, Next-Generation Performance-Based 

Seismic Design Guidelines. Program Plan for New and Existing Buildings. 

This document includes guidance for developing detailed modeling, 

simulation of building response to extreme loading, and estimates of 

potential casualties, loss of occupancy, and economic losses. The outlined process allows the design of a building to be adjusted to balance 

the level of acceptable risks and the cost of achieving the required level of building performance. Although the process outlined in FEMA 

445 is applied to seismic hazards, it can be generalized for application 

to other hazards. 

2.2 Prescriptive vs. Performance-Based Design

Design and construction in the United States is generally regulated 

by building codes and standards. Building codes are intended to 

ensure the health, safety, and well-being of people in buildings 

by establishing minimum requirements to address structural strength, 

adequate means of egress, sanitary equipment, light and ventilation, 

and fire safety. Building codes may also promote other objectives, such 

as energy efficiency, serviceability, quality or value, and accessibility for 

persons with disabilities. These prescriptive standards are easy for architects and engineers to understand, and easy for community inspectors 

to monitor. This ease of use is their great strength. 

Historically, building codes have been based on a prescriptive approach 

that limits the available solutions for compliance. Prescriptive or specification-based design emphasizes the “input,” or the materials and 

methods required. In contrast, the focus of performance-based design is 

the “output,” or the expectations and requirements 

of the building’s primary users and stakeholders. 

This approach provides a systematic method for assessing the performance capabilities of a building, 

system, or component, which can then be used to 

verify the equivalent performance of alternatives, 

deliver standard performance at a reduced cost, or 

confirm the higher performance needed for critical facilities such as schools. 

The ICC PC defines performance-based 

design as “An engineering approach to 

design elements of a building based on 

agreed upon performance goals and objectives, engineering analysis and quantitative 

assessment of alternatives against the 

design goals and objectives using accepted engineering tools, methodologies 

and performance criteria.”
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2-4 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

2.3 The Performance-Based Design Process

T he performance-based design process explicitly evaluates how 

building systems are likely to perform under a variety of conditions 

associated with potential hazard events. The process takes into 

consideration the uncertainties inherent in quantifying the frequency 

and magnitude of potential events and assessing the actual responses of 

building systems and the potential effects of the performance of these 

systems on the functionality of buildings. Identifying the performance 

capability of a facility is an integral part of the design process and guides 

the many design decisions that must be made. Figure 2-1 presents the 

key steps in this iterative process. 

Performance-based design starts with selecting design criteria articulated through one or more performance objectives. Each performance 

objective is a statement of the acceptable risk of incurring different levels of damage and the consequential losses that occur as a result of this 

damage. Losses can be associated with structural or nonstructural damage, and can be expressed in the form of casualties, direct economic 

costs, and loss of service costs. Loss of service costs may be the most 

important loss component to consider, especially for critical facilities 

such as schools. 

Select Performance 

Objectives

Develop Preliminary 

Design

Assess Performance 

Capability

Revised

Design and/or

Objectives

DONE

Does Performance 

Meet

Objectives?

NO YES

Figure 2-1: 

Performance-based 

design flow diagram 

SOURCE: HAMBURGER, 2003
PERFORMANCE-BASED DESIGN 2 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 2-5

Acceptable risks are typically expressed as acceptable losses for specific levels of hazard intensity 

and frequency. They take into consideration all 

the potential hazards that could affect the building and the probability of their occurrence during 

a specified time period. The overall analysis must 

consider not only the intensity and frequency of 

occurrence of hazard events, but also the effectiveness and reliability of the building systems to 

survive the event without significant interruption 

in the operation. 

2.4 Acceptable Risk and

Performance Levels

T he performance-based design process begins with establishing 

the acceptable risk and appropriate performance levels for the 

building and its systems. Acceptable risk is the maximum level of 

damage to the building that can be tolerated from a realistic risk event 

scenario or probability. The ICC PC formalizes four performance levels 

in terms of tolerable levels of damage to the building, its contents, and 

its occupants that apply to all types of hazards. Types of damage vary according to the hazard. The four performance levels are as follows: 

n Mild Impact. At the mild impact level, there is no structural damage 

and the building is safe to occupy. Injuries are minimal in number and minor in nature. Nonstructural systems needed for normal 

use and emergency operations are fully functional. Damage to contents is minimal in extent and minor in cost. Minimal hazardous 

materials are released to the environment. 

n Moderate Impact.  At the moderate level, moderate, repairable 

structural damage, and some delay in re-occupancy is expected. 

Nonstructural systems needed for building use are fully operational, 

although some cleanup and repair may be required. Emergency systems remain fully operational. Injuries may be locally significant, but 

are generally moderate in number and in nature; the likelihood of 

a single life loss is low and the likelihood of multiple life loss is very 

low. Some hazardous materials are released to the environment, but 

the risk to the community is minimal.

n High Impact. At the high impact level, significant damage to structural elements, but no large falling debris, is expected. Repair of 

structural damage is possible, but significant delays in re-occupancy 

can be expected. Nonstructural systems needed for normal building 

use are significantly damaged and inoperable. Emergency systems 

Hazard. A source of potential danger or 

adverse conditions. Natural hazards include events such as floods, earthquakes, 

tornadoes, tsunamis, coastal storms, landslides, and wildfires.

Risk. The estimated impact that a hazard 

event would have on people, services, 

facilities, and structures in a community, or 

the likelihood of a hazard event resulting in 

an adverse condition that causes injury or 

damage. 
2 PERFORMANCE-BASED DESIGN

2-6 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

may be significantly damaged, but remain operational. Injuries to 

occupants may be locally significant with a high risk to life, but are 

generally moderate in number and nature. The likelihood of a single life loss is moderate, and the likelihood of multiple life loss is low. 

Hazardous materials are released to the environment and localized 

relocation is required.

n Severe Impact. At the severe impact level, substantial structural damage is expected and repair may not be technically feasible, though 

all significant structural components continue to carry gravity load 

demands. The building is not safe for re-occupancy, because re-occupancy could cause collapse. Nonstructural systems for normal 

use may be inoperable, and emergency systems may be substantially 

damaged and inoperable. Injuries to occupants may be high in number and significant in nature. Significant hazards to life may exist. 

The likelihood of single life loss is high and the likelihood of multiple life loss is moderate. Significant amounts of hazardous materials 

may be released to the environment and relocation beyond the immediate vicinity is required.

The 2012 edition of the ICC PC will use the same system to classify performance groups that is used in ASCE 7-05 to classify structures. The 

groups are based on use or occupancy and each has different requirements. Prior to the 2010 edition, the ASCE 7 classification of structures 

included schools in Occupancy Category III and Occupancy Category 

IV, based on capacity. ASCE 7-10 categorizes buildings and structures 

into “risk categories” and no longer includes occupancy type. The risk 

categories are equivalent to the “performance groups” that are used in 

the ICC PC. The performance groups that apply to schools include:

n Performance Group IV (Risk Category IV) includes buildings and 

structures designated as essential facilities, and those for which failure could pose a substantial hazard to the community. Essential 

facilities are defined as those “intended to remain operational in 

the event of extreme environmental loading from wind, snow, or 

earthquakes.”

n Performance Group III (Risk Category III) includes buildings and 

structures for which failure could pose a substantial risk to human 

life and those not included in Risk Category IV with “potential to 

cause a substantial economic impact and/or mass disruption of dayto-day civilian life in the event of failure.” 
PERFORMANCE-BASED DESIGN 2 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 2-7

The ICC PC relates performance group and the maximum level of damage to be tolerated for different magnitudes of design events, as shown 

in Figure 2-2. Figure 2-3 relates the magnitude of design event to the 

mean return period (recurrence interval) for seismic, flood, and wind 

hazards. For example, consider a Performance Group III building that 

the stakeholders determine should be designed such that it will have 

a “moderate” level of performance (or moderate damage is the maximum level of damage to be tolerated). As indicated by Figure 2-2, to 

provide that level of performance, the building must be designed for 

large (or rare) events. And, based on Figure 2-3, if it is located in an area 

exposed to seismic risk, it should be designed for a seismic event that 

has a 475-year return period. To address flooding, the designers would 

have to determine the site-specific exposure (i.e., whether the location 

is exposed to flood hazards in addition to the 1-percent-annual-chance 

[100-year] flood, such as levee failure or dam failure). And to address 

high winds, the building should be designed for winds with a 100-year 

return period. MAGNITUDE OF DESIGN EVENT Increasing Magnitude of EventVery Large

(Very rare)

Large

(Rare)

Medium

(Less Frequent)

Small

(Frequent)

INCREASING LEVEL OF PERFORMANCE

Performance Groups

Performance

Group I

Performance

Group II

Performance

Group III

Performance

Group IV

Severe

Severe

Severe High

High

High

Moderate

Moderate Mild

Mild

Mild

Mild Mild

Moderate Mild

Moderate

Figure 2-2: Maximum 

level of damage to be 

tolerated based on 

performance groups and 

magnitude of design 

event 

SOURCE: ICC, 2009
2 PERFORMANCE-BASED DESIGN

2-8 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

2.5 Considerations For Achieving Continuous 

Operation Performance Level

After the preliminary design has been developed based on the 

selected performance level, the next step in the performancebased design process is to perform a series of simulations 

(analyses of building response to loading) to estimate the probable performance of the building under various design scenario events. Using 

fragility relationships (vulnerability functions defining the relationship 

between load and damage) developed through testing or calculation, 

building responses are equated to damage states expressed as levels of 

performance. If the simulated performance meets or exceeds the performance objectives, the design may be considered complete. If not, 

the design must be revised in an iterative process until the performance 

objectives are met. In some cases, meeting the stated objective at a reasonable cost will not be possible, in which case the team of designers, 

decisionmakers, and stakeholders may elect to modify some of the original performance objectives. 

Continued and uninterrupted operation is an important performance 

requirement for schools, regardless of the level of structural and nonstructural building damage, especially schools that are designated 

as community shelters. In other words, the acceptable performance 

is achieved as long as the structural and nonstructural damage to the 

building does not disrupt or impair the continued operation and 

functionality. In recent hurricanes, structures that did not sustain any 

Figure 2-3:

Relative magnitude 

and return period for 

seismic, flood, and wind 

events

SOURCE: ICC, 2009

MAGNITUDE OF DESIGN EVENT

Increasing Magnitude of Event

DESIGN EVENT

Seismic

(Mean Return Period) (Mean Return Period) (Mean Return Period)

Flood Wind

2,475 Years 125 Years Determined on

Site-Specific Basis

72 Years 500 Years 75 Years

25 Years 100 Years 50 Years

475 Years

(Not to Exceed 

Two-Thirds of the 

Intensity of Very Large)

100 Years

Determined on

Site-Specific Basis

Very Large

(Very rare)

Large

(Rare)

Medium

(Less Frequent)

Small

(Frequent)
PERFORMANCE-BASED DESIGN 2 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 2-9

structural damage were rendered inoperable as a result of nonstructural 

damage resulting in unacceptable performance (FEMA, 2006).

In terms of affecting the functionality and performance of a facility, the 

failure of nonstructural systems (roofing; exterior envelope; heating, 

ventilation, and air-conditioning [HVAC]; emergency systems) can be as 

significant as the failure of structural components. Performance-based 

design provides a framework for considering the potential hazards that 

can affect a facility or site, and for explicitly evaluating the performance 

capability of the facility and its components—including nonstructural 

systems and components. 

Designers must also consider the likelihood that at least a portion of 

the distribution systems of critical infrastructure services (e.g., electrical power, communications, potable water, and sanitary sewer) could be 

interrupted. The impact of interruptions in service should be assessed, 

and the time until service could be restored or supplemented should 

be estimated. To protect the continued operation of schools, especially 

those designated as community shelters, the most reliable approach is to 

provide alternative onsite systems in the form of: (1) emergency power 

generation capabilities; (2) local wireless communications; (3) potable 

water supplies; and (4) temporary onsite storage for sanitary waste.

While the practice of performance-based design is more advanced in the 

field of seismic design than the fields of flood and high-wind design, the 

theory of performance-based design is transferable to all hazards. The 

practice of performance-based design will prompt designers and owners 

of buildings in flood- or high-wind-prone regions to begin thinking in 

terms of a few basic objectives:

n Can the real probabilities and frequencies of flood and high-wind 

events during the useful life of the building be defined with an acceptable degree of accuracy?

n Can the extent and kinds of damage that can be tolerated be defined?

n Are there ways in which an acceptable level of performance can be 

achieved?

n Are there alternative levels of performance that can be achieved, 

and how much do they cost over the lifetime/ownership of the 

building compared to the benefits of reduced damage and improved 

performance?

n How do these levels compare to the performance levels of designs 

using the minimum requirements of the applicable building code?
2 PERFORMANCE-BASED DESIGN

2-10 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

2.6 Performance-Based Flood Design 

The performance levels and objectives for schools and other critical facilities exposed to flood hazards are:

n Mild Impact. The facility sustains no structural or nonstructural damage, emergency operations are fully functional, and the building is 

immediately operational. The site is not affected by erosion, but may 

have minor debris and sediment deposits. 

n Moderate Impact. The facility is affected by flooding above the lowest floor, but damage is minimal due to low depths and the short 

duration of flooding. Cleanup, drying, and minor repairs are required, especially of surface materials and affected equipment, but 

the building can be back in service in a short period of time.

n High Impact. The facility may sustain structural or nonstructural 

damage that requires repair or partial reconstruction, but the threat 

to life is minimal and occupant injuries are few and minor. Water 

damage to the interior of the facility requires cleanup, drying, and 

repairs, and may preclude occupancy of all or a portion of the facility for several weeks to several months.

n Severe Impact. The facility is severely damaged and likely requires 

demolition or extensive structural repair. Threats to occupants are 

substantial, and warning plans should prompt evacuation prior to 

the onset of this level of flooding. This performance level is applicable to facilities affected by all types of flooding, including those that 

result from failure of dams, levees, or floodwalls.

Planning and design to achieve an appropriate level of flood protection 

should include avoidance of flood hazard areas and the addition of a factor of safety (freeboard) to the anticipated flood elevation. Performance 

evaluation of a facility affected by flooding should consider the building 

response to the following load conditions (fragility functions must be developed to relate calculated response to actual damage states): 

n Lateral hydrostatic forces

n Vertical (buoyant) hydrostatic forces 

n Hydrodynamic forces

n Surge forces 

n Impact forces of floodborne debris 

n Breaking wave forces 

n Localized scour 
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DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 2-11

2.7 Performance-Based High-Wind Design 

The performance levels and objectives for schools and other critical facilities exposed to high-wind hazards are:

n Mild Impact. The facility is essentially undamaged and is immediately 

operational. 

n Moderate Impact. The facility is damaged and needs some repairs but 

can be functional and occupied after minor repairs to nonstructural 

components are complete. 

n High Impact. The facility may be structurally damaged but the threat 

to life is minimal and occupant injuries are few and minor. However, 

damage to nonstructural components (e.g., roofing, building envelope, exterior-mounted equipment) is great, and the cost to repair 

the damage is significant. If rain accompanies the windstorm, or if 

rain occurs prior to execution of emergency repairs, water damage 

to the interior of the facility may preclude occupancy of all or a portion of the facility for several weeks to several months.

n Severe Impact. The facility is severely damaged and will probably need 

to be demolished. Significant collapse may have occurred, and there is a 

great likelihood of occupant casualties unless the facility has a specially 

designed occupant shelter. This performance level is applicable to facilities struck by strong or violent hurricanes or tornadoes. For other types 

of windstorms, this performance level should not be reached.

The challenge with respect to performance-based high-wind design 

is assessing the wind resistance of the building envelope and exteriormounted equipment, and the corresponding damage susceptibility. 

Several factors make this assessment challenging:

n Analytical tools (i.e., calculations) are currently not available for 

many envelope systems and components, and realistic long-term 

wind resistance data is lacking. 

n Because of the complexity of their wind load responses, many envelope

systems and components require laboratory testing, rather than analytical evaluation, in order to determine their load-carrying capacities. 

n Eventually, finite element analysis will likely augment or replace 

laboratory testing, but substantial research is needed before finite element analysis can be used for the broad range of existing building 

envelope systems.

n Significant research is needed before design professionals can accurately assess the response of buildings and components to the effects 

of high winds.
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2-12 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

2.8 Performance-Based Seismic Design 

F or performance-based seismic design, the performance levels 

described in ASCE 41, Seismic Rehabilitation of Existing Buildings 

(2007), for both structural and nonstructural systems are the most 

widely-recognized characterizations. These performance levels are summarized in a matrix (see Table 2-1) and allow specification of an overall 

performance level by combining the desired structural performance 

with a desired nonstructural performance. 

Table 2-1: Combinations of structural and nonstructural seismic performance

Nonstructural 

Performance 

Levels

Structural Performance Levels and Ranges

S-1

Immediate 

Occupancy

S-2

Damage 

Control Range

S-3

Life 

Safety

S-4

Limited Safety 

Range

S-5

Collapse 

Prevention

S-6

Not 

Considered

N-A 

Operational

Operational 

1-A 2-A Not 

Recommended

Not 

Recommended

Not 

Recommended

Not 

Recommended

N-B 

Immediate 

Occupancy

Immediate 

Occupancy 1-B 2-B 3-B Not 

Recommended

Not 

Recommended

Not 

Recommended

N-C

Life Safety 1-C 2-C Life Safety 3-C 4-C 5-C 6-C

N-D

Hazards 

Reduced

Not 

Recommended 2-D 3-D 4-D 5-D 6-D

N-E

Not Considered

Not 

Recommended

Not 

Recommended

Not 

Recommended 4-E Collapse 

Prevention 5-E

No 

Rehabilitation

Four of the ASCE 41 performance levels identified in Table 2-1 are analogous to the ICC PC performance levels. “Mild” is similar to Operational 

(1-A); “Moderate” Is similar to Intermediate Occupancy (1-B); “High 

Impact” is similar to Life Safety (3-C); and “Severe” is similar to Collapse 

Prevention (5-C). These four performance levels are described below.

Operational Building Performance Level (1-A)

Buildings that meet this building performance level are expected to 

sustain minimal or no damage to their structural and nonstructural components. The building is able to continue its normal operations with only 

slight adjustments for power, water, or other utilities that may need to be 

provided from emergency sources. 
PERFORMANCE-BASED DESIGN 2 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 2-13

Under low levels of earthquake ground motion, most schools should be 

able to meet or exceed this target building performance level. However, 

designing buildings to achieve this performance level under very rare, intense ground shaking, may not be cost effective except for buildings that 

offer unique services or that contain exceptionally hazardous material.

Full functionality is normally considered difficult to achieve in the immediate aftermath of strong earthquake shaking. Offsite issues, such as staff 

availability and potential loss of utilities that are not under the control of 

the facility, may more seriously impair operations. In addition, relatively 

minor onsite damage to key components can significantly affect overall 

functionality. For example, failure of a single anchor point for a primary 

emergency generator could disrupt functionality at least for a short period of time. 

Immediate Occupancy Building Performance Level (1-B)

Buildings that meet this building performance level are expected to 

sustain minimal damage to their structural elements and only minor 

damage to their nonstructural components. While it is safe to reoccupy 

a building designed for this performance level immediately following a 

major earthquake, nonstructural systems may not function due to power outage or damage to fragile equipment. Consequently, although 

immediate occupancy is possible, some cleanup and repair and restoration of utility services may be necessary before the building can 

function in a normal mode. The risk of casualties at this target performance level is very low.

Many building owners may wish to achieve this level of performance 

when the building is subjected to moderate earthquake ground motion. In addition, some owners may desire such performance for very 

important buildings even if exposed to severe earthquake ground 

shaking. This level provides most of the protection obtained under the 

Operational Building Performance Level without the costs of standby 

utilities and rigorous seismic equipment performance.

Designing to the Immediate Occupancy Building Performance Level 

is more realistic than the Operational Building Performance Level 

for most buildings, and at a minimum, should be the design goal for 

all new school buildings. However, because even the smallest disruption of nonstructural systems may be too detrimental for continued 

operation of a school that is designated as a shelter, owners and designers should consider an even higher level of protection for critical 

functions associated with this use. For instance, stakeholders should 

consider providing for the independent operation of critical utilities 
2 PERFORMANCE-BASED DESIGN

2-14 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

for a minimum of 4 days. Critical utilities usually include electric power, 

water, sanitary sewer, and, depending on the local weather conditions, 

fuel for heating and cooling.

Life Safety Building Performance Level (3-C)

Buildings that meet this building performance level may experience extensive damage to structural and nonstructural components. Repairs 

may be required before re-occupancy, though in some cases extensive 

restoration or reconstruction may not be cost effective. The risk of casualties at this target performance level is low.

This building performance level allows somewhat more extensive 

damage than would be anticipated for new buildings designed and constructed for seismic resistance. The Life Safety Building Performance 

Level should prevent significant casualties among able-bodied school 

occupants.

Collapse Prevention Building Performance Level (5-E)

Although buildings that meet this building performance level may pose 

a significant hazard to life safety resulting from failure of nonstructural 

components, significant loss of life may be avoided by preventing collapse of the entire building. However, many buildings designed to meet 

this performance level may be complete economic losses.

Sometimes this performance level is selected as the basis for mandatory 

seismic rehabilitation ordinances enacted by regulatory authorities because it mitigates the most severe life-safety hazards at the lowest cost. 

The Collapse Prevention Building Performance Level is intended to prevent only the most egregious structural failures, and does not allow for 

continued occupancy and functionality or cost-effective damage repair 

of structural and nonstructural components.

2.9 References

American Society of Civil Engineers (ASCE), 2005. Minimum Design 

Loads for Buildings and Other Structures, ASCE 7-05, Structural Engineering 

Institute, Reston, VA.

ASCE, 2007. Seismic Rehabilitation of Existing Buildings, ASCE 41-06, 

Structural Engineering Institute, Reston, VA.

ASCE, 2010. Minimum Design Loads for Buildings and Other Structures, ASCE 

7-10, Structural Engineering Institute, Reston, VA.
PERFORMANCE-BASED DESIGN 2 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 2-15

Federal Emergency Management Agency (FEMA), 2006. Hurricane 

Katrina in the Gulf Coast: Mitigation Assessment Team Report, Building 

Performance Observations, Recommendations, and Technical Guidance, FEMA 

549, Washington, DC, July 2006.

Hamburger, R.O., 2003. “A Vision for Performance Based Earthquake 

Engineering,” Unpublished white paper for the ATC-58 Project, 

Framework for Performance-Based Design of Nonstructural Components, 

Applied Technology Council, Redwood City, CA, 2003.

International Code Council, Inc. (ICC), 2009. ICC Performance Code for 

Buildings and Facilities (ICC PC), Country Club Hills, IL, 2009.

National Fire Protection Association (NFPA), 2008. NFPA 101: Life Safety 

Code, 2009 Edition, Quincy, MA, 2008.

NFPA, 2009. Building Construction and Safety Code, NFPA 5000, Quincy, 

MA, 2009.

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 3-1

Multihazard 3Design 

3.1 Introduction

T his chapter compares the effects of three natural hazards that are 

the subject of this publication, in terms of their geographical locations, relative warning times, and how likely they are to occur. Fire 

and life safety considerations are discussed. The design methods used 

to resist the effects of each natural hazard are discussed in the context 

of the design methods for the other natural hazards. This integrated approach is a key aspect of multihazard design that must be reflected in a 

larger integrated approach to the whole building design. 

3.2 The Hazards Compared

T his section compares the three natural hazards together with issues relating to designing for fire protection, which is required for 

all school buildings. A general understanding of all hazards is necessary in order to develop an integrated approach which is important 

for locations subject to more than one hazard. Designs for two or more 

hazards may reinforce one another, thus reducing cost and improving 
3-2 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

3 MULTIHAZARD DESIGN

protection. They may also conflict with each other. This section presents 

a systematic analysis of these multihazard protection methods. The analysis takes the form of the matrices shown in Section 3.5. Facility planners 

and designers faced with the challenge of multihazard design requirements may find this section beneficial to stimulate discussion and to 

prompt analysis at the outset of project design. The threat of physical attack is covered in a companion publication, FEMA 428, Primer to Design 

Safe School Projects in Case of Terrorist Attacks.

3.2.1 Location: Where do Hazards Occur?

The common public perception of natural hazards is that earthquakes 

occur in California, floods involve major rivers, tornadoes strike the 

Midwest, and hurricanes affect the shorelines of the southern Atlantic 

and Gulf of Mexico. Although there is some truth to this perception as it 

relates to the highest probabilities, maps that show past disasters reveal 

that the entire United States is vulnerable to one or more of the three 

primary natural hazards: earthquakes, floods, or high winds. 

n Earthquakes are predominant in the West, but also threaten specific 

regions in the Midwest, Northeast, and Southeast, and the U.S. territories.1

 The great earthquakes centered on the little town of New 

Madrid, MO, in 1811 and 1812 caused little damage and only a few 

casualties; a recurrence of these earthquakes would impact some of 

the most populous cities of the Midwest. The worst earthquake in the 

eastern States occurred in Charleston, SC, in 1886; 60 people were 

killed and the modest sized city suffered the equivalent of about $25 

million damage in today’s dollars. 

n Riverine floods occur along rivers and streams of all sizes, and coastal 

flooding is associated with storm surges caused by high winds along 

the entire U.S. shoreline and Great Lakes. Flash floods caused by 

sudden, intense rainstorms may occur anywhere. Some of the worst 

floods in U.S. history have been caused by dam failures, often when 

rivers are already swollen by flood waters. 

n Extreme winds are regional (e.g., hurricanes along the Atlantic and 

Gulf coasts, the Caribbean, and the South Pacific; tornadoes typically 

in the Midwest; and downslope winds adjoining mountain ranges), 

but high winds can also occur anywhere. 

n Alaska, Hawaii, parts of the East Coast, and the U.S. territories may 

all be affected by earthquakes, floods, and high winds.

1 The U.S. territories include American Samoa, Guam, Northern Mariana Islands, Puerto Rico, 

and the U.S. Virgin Islands.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 3-3

MULTIHAZARD DESIGN 3

Figure 3-1 illustrates the areas where earthquakes are likely to occur on 

the U.S. mainland. The contour lines indicate the 2-percent probability 

of exceedance of ground motion accelerations within each contour area 

(or the “odds” [2 percent] that the accelerations will be exceeded in a 50-

year period). Figure 3-2 is the basic wind speed map from ASCE 7 that is 

cited in the model building codes and used to select design wind speeds. 

In addition to high wind regions around the Gulf and Atlantic Coasts, it 

identifies “special wind regions” in mountainous areas where high winds 

are likely. Locations where flooding is likely cannot be illustrated in a 

similar manner because flooding occurs along virtually every body of water, whether large or small. Flood hazard maps are available at the county 

and municipality level. Chapters 4, 5, and 6 provide information that will 

help establish the risk for each of these hazards (earthquakes, floods, 

and high winds) in a local region, respectively.

Figure 3-1: 

Areas where earthquakes are likely to occur on the U.S. mainland. The contour lines indicate the 2-percent 

probability of exceedance of ground motion accelerations within each contour area (or the “odds” [2-percent] 

that the accelerations will be exceeded in a 50-year period).
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3.2.2 Warning: How Much Warning is There? 

The warning times for the three primary natural hazards vary as a function of many variables: 

n Earthquakes are unique among the natural hazards because there is 

no warning at all, although new sensing devices can give a few seconds warning to locations far from the epicenter. Although much 

work has been done throughout the world to develop a scientific 

prediction methodology (based on characteristics such as changes in 

the dimensional or physical nature of the ground prior to an earthquake, detailed investigation of the geologic strata, or statistical data 

on the incidence of previous earthquakes), earthquakes must still be 

regarded as random events within a general envelope of probability.

n Riverine floods (except flash floods) can usually be predicted to give 

hours or days of warning. National and regional river monitoring 

Figure 3-2: 

Basic wind speed map from ASCE 7 for Risk Category III and IV buildings and other structures. ASCE 7 is cited 

in the model building codes and used to select design wind speeds.

SOURCE: ASCE 7-10
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MULTIHAZARD DESIGN 3

systems and numerous local weather and flood warning systems provide improved warning along many waterways. 

n Coastal flooding associated with hurricanes can be anticipated because tropical systems can be tracked for days before making landfall. 

Hurricanes are tracked by the National Hurricane Center and their 

movements are carefully and thoroughly reported although there 

are many variables that limit the precision of predictions. Other 

coastal storms, such as nor’easters and those that affect the Pacific 

and Great Lakes shorelines are less predictable.

n Tornadoes are localized, though sometimes visible from a distance. 

However, modern technology allows the National Weather Surface to 

identify conditions that are conducive to the formation of tornadoes. 

Typically, they hit a specific location with only a few minutes notice. 

3.2.3 Frequency: How Likely are They to Occur?

For all hazards, the probability that an event will occur within a region 

is much higher than the probability that an event will occur at a specific 

location. Extreme events are relatively rare for a given site. Some level of 

inundation in riverine floodplains and coastal shorelines occurs relatively frequently. Storms that produce sufficient rainfall-runoff to cause river 

and stream flooding can occur throughout the year, although are more 

prevalent during specific seasons in some areas of the country. Coastal 

nor’easter storms generally occur in the winter and early spring months, 

while hurricanes roam the Gulf Coast and Atlantic seaboard between 

June 1st and the end of November, bringing both high winds and storm 

surge flooding. 

Earthquakes are perhaps the most difficult to deal with, because of their 

complete lack of warning, their rarity, and their possible extreme consequences. Although an earthquake of a given magnitude is still, in 

practical terms, unpredictable, its probability of occurrence can reasonably be predicted as far higher in California or Alaska than in, for 

example, Massachusetts or Tennessee. Even in California, the rarity of 

a large earthquake is such that many people will not experience one in 

their lifetime. In less seismically active parts of the country, the probability of an event is even smaller.

Because the occurrence of natural hazards is only broadly predictable, 

the frequency of occurrence of future events can only be expressed as 

probabilities. The probability of occurrence of earthquakes, floods, and 

high winds is commonly expressed by the term “return period” or “mean 

recurrence interval,” which is defined as the average or mean time in 

years between the expected occurrence of events of specified intensity. 
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Prior to the 2000 International Building Code (IBC), the seismic maps in 

the model buildings codes used a level of shaking (an acceleration value) 

that corresponds to a 10-percent probability of exceedance in 50 years 

(or a probability that it would be exceeded one time in approximately 

475 years, a 475-year recurrence interval). More recently, research suggests that certain areas, such as the central and eastern United States and 

in particular the New Madrid Seismic Zone, may be vulnerable to much 

larger but less frequent quakes. More recent seismic hazard maps produced by the U.S. Geological Survey (USGS) and appearing in the 2000 

IBC and later editions show acceleration values for a 2-percent probability of exceedance in 50 years (e.g., a recurrence interval of 2,475 years). 

Designs based on this level are expected to provide significant protection in areas subject to large but less frequent earthquakes. Additional 

information about seismic maps appearing in the IBC can be found in 

FEMA 450, NEHRP Recommended Provisions for Seismic Regulations for New 

Buildings and Other Structures (2003a). 

Beginning with the 2010 edition of ASCE 7, for Risk Category III and IV 

buildings, the basic wind speed is associated with a return period of 1,700 

years, or an annual exceedance probability of 0.000588. The magnitude 

of flood event used as the minimum design value is the 1-percent-annualchance flood, which has a 100-year return period (often call the “100-year 

flood”). These return periods may seem very long (i.e., a business owner 

confronting small crises every day and large ones every month may not be 

worried about an event that might not occur for 500 years). And if the return period for an earthquake event in California is 500 years, the public 

may erroneously believe that it will be another 400 years before an event 

of the magnitude of the 1906 San Francisco earthquake occurs.

These expressions of frequency represent mean or average return periods over a very long period of time, but may be perceived as not pertinent 

in relation to the shorter time periods that most people are interested in 

(i.e., the next year or the next 10 years). Because floods and high winds 

occur relatively more frequently, the discrepancy between the actual occurrence experienced at a given location and the mean return period 

used to establish design loads is much more noticeable than the corresponding probabilities for earthquakes. 

3.3 A Comparison of Potential Losses

T he HAZUS-MH (Hazards U.S. Multi-Hazards) program is a 

Geographic Information System (GIS)-based program developed 

by FEMA to estimate future losses for use by Federal, State, regional, and local governments to plan for damage, to prepare emergency 

response and recovery programs, and to help examine options to reduce 
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 3-7

MULTIHAZARD DESIGN 3

future damage. The methodology covers nearly all aspects of the built 

environment and estimates a wide range of losses. Originally developed 

to assess risks from earthquakes, the methodology has been expanded 

to address floods throughout the United States and hurricanes in the 

Atlantic and Gulf Coast regions.

In order to obtain an indication of the magnitude of losses and their relative significance for the three hazards considered in this design guide, 

a “Level 1” HAZUS-MH analysis was conducted in 2003 for educational 

facilities in six areas of the United States. The Level 1 analysis uses the 

building inventory data that are packaged with the HAZUS-MH program 

and is intended to give a broad picture of damage and loss on a regional 

basis. Although prepared several years ago, the results remain useful to 

compare potential losses between different parts of the country.

The analyses were based on the building information for the EDU 1 

occupancy class (the HAZUS-MH designation for the school building 

inventory) in the general building stock module of HAZUS-MH. The 

regions chosen for this comparative example are each prone to two or 

more of the hazards addressed in HAZUS-MH, and are deemed to provide a useful geographic range. For each region and applicable hazard, 

probabilistic losses for a 100- and 500-year return period event (earthquake, flood, or high wind) were computed. The results are summarized 

in Table 3-1, in which the column “EDU 1 Exposure” refers to the total 

school inventory in each region.

The following regions were evaluated:

n Charleston County, SC (Charleston) (earthquake, flood, and 

hurricane)

n Shelby County, TN (Memphis) (earthquake and flood)

n Bexar County, TX (San Antonio) (hurricane and flood)

n Salt Lake County, UT (Salt Lake City) (earthquake and flood)

n Suffolk County, MA (Boston) (earthquake, flood, and hurricane)

n Hillsborough County, FL (Tampa) (hurricane and flood)

Table 3-2 shows the estimated losses expressed as a percentage of the 

total school inventory. It is instructive to note, in some cases, the wide disparity in losses between the 100-year and 500-year events, which supports 

the idea that school facilities should be designed to resist the impacts of 

events that have a lower probability of occurrence.
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Table 3-1: HAZUS-MH earthquake, hurricane, and flood losses (all values are in $1,000s—2002 valuation)

Charleston, SC Earthquake Hurricane Flood EDU 1 Exposure

100-yr 500-yr 100-yr 500-yr 100-yr 500-yr

Building Damage 31 3,449 5,802 22,290 1,378 1,554 63,787 Building

Contents and 

Inventory

4 1,365 3,690 16,897 392 557 63,787 Contents

Business Interruption 5 320 2,052 6,558 NE NE

TOTAL 40 5,134 11,544 45,745 1,770 2,111

Shelby, TN Earthquake Hurricane Flood EDU 1 Exposure

100-yr 500-yr 100-yr 500-yr 100-yr 500-yr

Building Damage 243 10,464 N/A N/A 4,184 6,784 137,927 Building

Contents and 

Inventory

53 3,723 N/A N/A 1,203 2,001 137,927 Contents

Business Interruption 29 916 N/A N/A NE NE

TOTAL 325 15,103 – – 5,387 8,786

Bexar, TX Earthquake Hurricane Flood EDU 1 Exposure

100-yr 500-yr 100-yr 500-yr 100-yr 500-yr

Building Damage N/A N/A 94 2,753 1,502 2,384 238,608 Building

Contents and 

Inventory

N/A N/A 5 1,259 487 727 238,608 Contents

Business Interruption N/A N/A 7 2,078 NE NE

TOTAL – – 106 6,090 1,989 3,111

Salt Lake, UT Earthquake Hurricane Flood EDU 1 Exposure

100-yr 500-yr 100-yr 500-yr 100-yr 500-yr

Building Damage 2,175 30,313 N/A N/A 15 204 177,728 Building

Contents and 

Inventory

881 9,016 N/A N/A 4 57 177,728 Contents

Business Interruption 259 2,488 N/A N/A NE NE

TOTAL 3,315 41,817 – – 19 261

Suffolk, MA Earthquake Hurricane Flood EDU 1 Exposure

100-yr 500-yr 100-yr 500-yr 100-yr 500-yr

Building Damage 0 1,544 4,837 58,640 254 907 268,311 Building

Contents and 

Inventory

0 484 2,258 40,665 70 305 268,311 Contents

Business Interruption 0 172 2,871 18,316 NE NE

TOTAL 0 2,200 9,966 117,621 324 1,212

Hillsborough, FL Earthquake Hurricane Flood EDU 1 Exposure

100-yr 500-yr 100-yr 500-yr 100-yr 500-yr

Building Damage N/A N/A 10,257 47,213 10,727 11,776 175,981 Building

Contents and 

Inventory

N/A N/A 6,045 39,016 4,329 4,624 175,981 Contents

Business Interruption N/A N/A 4,291 13,004 NE NE

TOTAL – – 20,593 99,233 15,056 16,400

NOTES: EDU 1 Exposure = total school and contents inventory in each region (2003).

NE = HAZUS did not estimate these losses. 

0 = Evaluated, but no losses.

N/A = hazard not present in the area.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 3-9

MULTIHAZARD DESIGN 3

Table 3-2: HAZUS-MH estimated losses by percentage of school building and contents inventory

Earthquake Hurricane Flood

County 100-yr 500-yr 100-yr 500-yr 100-yr 500-yr

Charleston, SC 0.20 17.30 4.54 17.50 1.38 1.65

Shelby, TN 0.12 5.47 N/A N/A 1.95 2.46

Bexar, TX N/A N/A 0.02 1.27 0.40 0.65

Salt Lake, UT 1.10 11.76 N/A N/A 0.01 0.07

Suffolk, MA 0 0.80 N/A N/A N/A N/A

Hillsborough, FL N/A N/A 5.85 28.20 4.27 4.65

NOTES: N/A = hazard not present in the area.

These HAZUS-MH results, though prepared in 2003, limited in scope, 

and based on limited school building inventory information, provide 

some interesting comparisons:

n Generally, the 100-year earthquake causes insignificant damage, except in Salt Lake City, UT ($3.3 million).

n The 500-year earthquake causes the most damage in Salt Lake City, 

UT ($41.8 million), followed by Shelby, TN ($15.1 million), and 

Charleston, SC ($5.1 million).

n The 100-year hurricane causes the most damage in Hillsborough, 

FL ($20.6 million), followed by Charleston, SC ($11.5 million), and 

Suffolk, MA ($10 million).

n The 500-year hurricane causes $117.6 million in damage in Suffolk, 

MA, $99.2 million in damage in Hillsborough, FL, and $45.7 million 

in damage in Charleston, SC.

n The 100-year flood causes by far the most damage in Hillsborough, 

FL ($15.1 million; however, the 500-year flood causes only another 

$1.3 million in damage). In Shelby, TN, the 100-year flood causes 

$5.4 million in damage and the 500-year flood causes another $3.3 

million. 

n Charleston, SC, has the greatest combined threat from earthquakes 

and hurricanes; Hillsborough, FL, has the greatest combined threat 

from hurricanes and floods. 
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3.4 Fire and Life Safety

Of the many hazards that can endanger a school, its occupants, and 

its service to the community, the most prevalent is fire. Structure 

fires occur more frequently than any of the hazards noted above. 

However, requirements to account for fire protection and safety have 

long been included in building codes in the form of requirements for 

approved materials, fire-resistant assemblies, exiting, the width and design of stairs, the dimensions of corridors, fire suppression systems, and 

many other issues. In fact, fire considerations are 

now so embedded in the design culture and regulation that some designers may not fully consider 

the fire hazard as a specific design issue.

Fires in older school buildings often result in a total 

loss of the building. This is due to a variety of factors, which include: delay of discovery and alarm, 

remote locations, lack of fire walls and/or compartmentation, lack of 

draft stopping in combustible attics, lack of automatic fire sprinkler 

systems, and inadequate water supplies for manual fire suppression activities. Losses in buildings without automatic fire alarm and detection 

systems are twice those in buildings with such systems. Additionally, fire 

losses in buildings without automatic fire sprinkler protection are five 

times higher than those in buildings protected by sprinklers.

Since the 1970s, the provisions of the various building codes have continued to improve the level of fire and life safety of new school facilities. 

The code requirements do not apply to existing buildings until renovations or additions are made, and then the requirements may apply only 

to the new work. Given that the average age of school facilities in the 

United States is more than 40 years, older buildings likely do not provide the same level of protection as newer buildings. In order to provide 

the level of protection achieved in newer buildings, the levels of fire and 

life safety of older facilities should be evaluated. After an evaluation has 

been conducted, solutions using prescriptive and/or performance approaches can be developed and undertaken.

The existing structures chapter of the IBC provides a method to evaluate 

the overall level of fire and life safety in an existing building. Although 

the method is generally intended to be applied to an existing building 

during changes in occupancy or renovation, it can provide the basis for 

the evaluation of any existing building. 

The evaluation method comprises three categories: fire safety, means of 

egress, and general safety. The fire safety evaluation includes structural 

Of the many hazards that can endanger 

a school, its occupants, and its service to 

the community, the most prevalent is fire. 

Structure fires occur more frequently than 

any of the hazards noted above. 
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MULTIHAZARD DESIGN 3

fire resistance, automatic fire detection, and fire alarm and fire suppression systems. Included within the means of egress portion are the 

configuration, characteristics, and support features for the means of 

egress. The general safety section evaluates various fire safety and means 

of egress parameters. The evaluation method generates a numerical 

score in the various areas, which can then be compared to mandatory safety scores. Deficiencies in one area may be offset by other safety 

features.

The provisions of NFPA 101 provide another method of evaluating and 

upgrading existing facilities. This document is intended to be applied 

retroactively to existing facilities and has a chapter specifically for existing educational occupancies. Even if this code is not adopted by the local 

jurisdiction, it can be used as the basis for an evaluation of any existing 

facility.

Upgrading an existing school facility can be costly. However, the cost of 

upgrades generally is less than the direct and indirect losses if a facility sustains major damage caused by fire. The most effective method of 

providing fire protection is through automatic fire sprinklers, but other 

lower cost methods can be utilized, including:

n Automatic fire alarm and detection

n Draft stopping in combustible attic spaces

n Smoke and fire compartmentation walls in occupied spaces

Upgrades in fire and life safety can often be coordinated with other 

building renovations or upgrades to help reduce costs. For instance, 

draft stopping could be installed in a wood framed attic during roof deck 

replacement. Fire sprinklers could be installed during asbestos abatement or ceiling replacement/upgrades for seismic concerns. 

3.5 Multihazard Design Interactions

A n integrated approach to designing for all hazards can help to 

identify potentially conflicting effects of certain mitigation measures and help to avoid aggravating the vulnerability of school 

systems and components. Table 3-3 summarizes the effects that design 

for more than one hazard may have on the performance of the building, addition, or repair. The columns show the five primary hazards. 

The rows show examples of methods of protection that have significant 

interaction (either beneficial, undesirable, or little to no significance). 

These methods are taken from the extended descriptions of risk reduction methods for the three primary natural hazards (see Chapters 4, 5, 
3-12 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

3 MULTIHAZARD DESIGN

and 6), together with the methods for security/blast protection presented in FEMA 428. In addition, the interactions of these four categories 

of risk protection with fire safety, where they occur, are also suggested. 

The suggested interactions are intended to provoke thought and design 

integration; they are not absolute restrictions nor are they recommendations. In general, beneficial conditions can be identified and undesirable 

conditions and conflicts can be avoided through coordinated design between the consultants, starting at the inception of design. The table can 

be used as a starting point for discussion relative to specific projects and 

to structure the benefits and conflicts of multihazard design depending 

on local hazards.

Table 3-3: Multihazard design system interactions 

Key

4 Indicates desirable condition or method for designated component/system 

8 Indicates undesirable condition or method for designated component/system 

m Indicates little or no significance for designated component/system

Split box indicates significance may vary, see discussion issues

Table 3-3: Multihazard design system interactions

Building System Protection Methods: Reinforcements and Conflicts

System 

ID

Existing Conditions 

or Proposed 

Protection Methods

The Hazards

Earthquake Flood Wind Security/ 

Blast Fire Discussion Issues

1 Site

1-1 Building elevated 

on fill

m 4 m m m Excellent solution for flood.

1-2 Two means of site 

access

4 4 4 4 4

1-3 In close proximity 

to other facilities 

that are high risk 

targets for attack 

m m m 8 m
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MULTIHAZARD DESIGN 3

Table 3-3: Multihazard design system interactions

Building System Protection Methods: Reinforcements and Conflicts

System 

ID

Existing Conditions 

or Proposed 

Protection Methods

The Hazards

Earthquake Flood Wind Security/ 

Blast Fire Discussion Issues

2 Architectural

2A Configuration

2A-1 Large roof 

overhangs 8 m 8 8 m

Possibly vulnerable to vertical 

forces in earthquake, uplift 

wind forces. The wall to roof 

intersection will tend to contain 

and concentrate blast forces if 

the point of detonation is below 

the eaves.

2A-2

Re-entrant corner 

(L-, U-shape, etc.) 

building forms

8 m 8 8 m

May concentrate wind or blast 

forces; may cause stress 

concentrations and torsion in 

earthquakes.

2A-3

Enclosed 

courtyard building 

forms

8 m 4 4 8 m

May cause stress 

concentrations and torsion in 

earthquake; courtyard provides 

protected area against high 

winds. Depending on individual 

design, they may offer 

protection or be undesirable 

during a blast event. If they 

are not enclosed on all four 

sides, the “U” shape or reentrant corners create blast 

vulnerability. If enclosed on all 

sides, they might experience 

significant blast pressures, 

depending on building and 

roof design. Because most 

courtyards have significant 

glazed areas, this could be 

problematic.

2A-4 Very complex 

building forms

8 8 8 8 8 May cause stress concentrations 

and torsion in highly stressed 

structures, and confusing 

evacuation paths and access for 

firefighting. Complicates flood 

resistance by means other than 

fill.

2B Planning and Function (No significant impact)

2C Ceilings (No significant impact)
3-14 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

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Table 3-3: Multihazard design system interactions

Building System Protection Methods: Reinforcements and Conflicts

System 

ID

Existing Conditions 

or Proposed 

Protection Methods

The Hazards

Earthquake Flood Wind Security/ 

Blast Fire Discussion Issues

2 Architectural (continued)

2D Partitions

2D-1 Block, hollow clay 

tile partitions 8 4 8 8 4

Wind and seismic force 

reactions would be similar 

for heavy unreinforced 

wall sections, with risk of 

overturning. Tile may become 

flying debris during a blast. It is 

possible, but difficult, to protect 

structures with blast walls, but 

a weak nonstructural wall has 

more chance of hurting people 

as debris. Desirable against 

fire and not seriously damaged 

by flood.

2D-2

Use of non-rigid 

connections for 

attaching interior 

non-load bearing 

walls to structure

4 m 4 4 8

Non-rigid connections are 

necessary to avoid partitions 

influencing structural response. 

However, gaps provided for 

this threaten the fire resistance 

integrity and special detailing 

is necessary to close gaps but 

retain ability for independent 

movement. 

2D-3 Gypsum board 

partitions 4 8 m 8 8

Although gypsum board 

partitions can be constructed 

to have a fire resistance rating, 

they can be easily damaged 

during fire operations. Such 

partitions can be more easily 

damaged or penetrated during 

normal building use.

2D-4

Concrete 

masonry units 

(CMUs), hollow 

clay tile around 

exit ways and exit 

stairs

8 m m 8 4 4

May create torsional structural 

response and/or stress 

concentration in earthquakes 

in frame structures unless 

separated and, if unreinforced, 

wall is prone to damage. 

Properly reinforced walls 

preserve evacuation routes in 

case of fire or blast.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 3-15

MULTIHAZARD DESIGN 3

Table 3-3: Multihazard design system interactions

Building System Protection Methods: Reinforcements and Conflicts

System 

ID

Existing Conditions 

or Proposed 

Protection Methods

The Hazards

Earthquake Flood Wind Security/ 

Blast Fire Discussion Issues

2 Architectural (continued)

2E Other Elements

2E-1 Heavy roof (e.g., 

slate, tile) 8 m 8 8 8 4

Heavy roofs are undesirable 

in earthquakes; slates and 

tiles may detach. Heavy roofs 

provide good protection from 

fire spread, but can also cause 

collapse of a fire-weakened 

structure. Almost always 

used on steep-sloped roofs; if 

wind-blown debris or a blast 

wave hits them, they become 

flying debris and dangerous to 

people outside the building.

2E-2 Parapet 8 4 m 8 8 4

Properly engineered parapet 

is acceptable for seismic; 

unbraced unreinforced 

masonry (URM) is dangerous. 

May assist in reducing the 

spread of fire.

3 Structural Systems

3-1

Heavy structure: 

reinforced 

concrete (RC) 

masonry, RC 

or masonry 

fireproofing of 

steel

8 4 4 4 4

Increases seismic forces, but 

generally beneficial against 

other hazards.

3-2 Light structure: 

steel/wood 4 8 8 8 8

Decreases seismic forces, but 

generally less effective against 

other hazards. 

3-3

URM exterior 

load bearing 

walls

8 8 8 8 8

3-4

Concrete or 

reinforced CMU 

exterior structural 

walls 

4 4 4 4 4

3-5 Soft/weak first 

story 8 8 4 8 8 8

Very poor earthquake 

performance, and vulnerable 

to blast. Generally undesirable 

for flood and wind. Elevated 

first floor is beneficial for flood 

if well constructed, but should 

not be achieved by a weak 

structure that is vulnerable to 

wind or flood loads.
3-16 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

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Table 3-3: Multihazard design system interactions

Building System Protection Methods: Reinforcements and Conflicts

System 

ID

Existing Conditions 

or Proposed 

Protection Methods

The Hazards

Earthquake Flood Wind Security/ 

Blast Fire Discussion Issues

3 Structural Systems (continued)

3-6 Indirect load path 8 m 8 8 8

Undesirable for highly stressed 

structures, and fire-weakened 

structure is more prone to 

collapse. Not critical for floods.

3-7 Discontinuities in 

vertical structure 8 m 8 8 8

Undesirable for highly stressed 

structures; causes stress 

concentrations, and fireweakened structure is more 

prone to collapse. Not critical 

for floods.

3-8 Seismic 

separation joints 4 m m m 8 Possible path for toxic gases to 

migrate to other floors. 

3-9

Ductile detailing 

and connections/

steel

4 m 4 4 m Provides a tougher structure that 

is more resistant to collapse.

3-10 Ductile detailing/

RC 4 m 4 4 m Provides a tougher structure that 

is more resistant to collapse.

3-11 Design for uplift 

(wind) 4 m 4 4 m

Necessary for wind; may assist 

in resisting seismic or blast 

forces.

3-12

Concrete 

masonry units, 

hollow clay tile 

around exit ways 

and exit stairs

8 m m 8 4

May create torsional structural 

response and/or stress 

concentration in earthquakes 

in frame structures unless 

separated, and if unreinforced 

wall is prone to damage. 

Properly reinforced walls 

preserve evacuation routes in 

the event of fire or blast.

4 Building Envelope

4A Wall Cladding

4A-1 Masonry veneer 

on exterior walls 8 8 8 8 m

In earthquakes, material may 

detach and cause injury. In 

winds and attacks, may detach 

and become flying debris 

hazard. Flood forces can 

separate veneer from walls.

4B Glazing

4B-1 Metal/glass 

curtain wall 4 m 8 8 8

Fire can spread upward behind 

the curtain wall if not properly 

fire-stopped. Not blast-resistant 

without special glass and 

detailing. Light weight reduces 

earthquake forces. 

4B-2 Impact-resistant 

glazing m m 4 4 8

Can cause problems during fire 

suppression operations, limiting 

access and smoke ventilation.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 3-17

MULTIHAZARD DESIGN 3

Table 3-3: Multihazard design system interactions

Building System Protection Methods: Reinforcements and Conflicts

System 

ID

Existing Conditions 

or Proposed 

Protection Methods

The Hazards

Earthquake Flood Wind Security/ 

Blast Fire Discussion Issues

5 Utilities (No significant impact)

6 Mechanical

6-1

HVAC system 

designed for 

purging in the 

event of fire

m m m 4 4

Can be effective in reducing 

chemical, biological, or 

radiological (CBR) threat if 

it has rapid shut-down and 

efficient dampers, and is 

located in an airtight building.

6-2

Large rooftopmounted 

equipment 

8 4 8 8 m

Vulnerable to earthquake and 

wind forces. Raises equipment 

above flood level.

7 Plumbing and Gas (No significant impact)

8 Electrical (No significant impact)

9 Fire Alarm (No significant impact)

10 Communications and Information Technology (IT) (No significant impact)

11 Equipment Operations and Maintenance (O&M) (No significant impact)

12 Security (No significant impact)

12A Perimeter Systems (No significant impact)

12B Interior Security (No significant impact)

12C Security System Documents (No significant impact)

13 Security Master Plan (No significant impact)

SOURCE: FEMA 426, REFERENCE MANUAL TO MITIGATE POTENTIAL TERRORIST ATTACKS AGAINST 

BUILDINGS, 2003

Notes:

The table refers to typical school structures: steel frame, concrete block or RC walls, wood frame, 

1-2 stories suburban, 2-4 stories urban.
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3 MULTIHAZARD DESIGN

3.6 References

American Institute of Architects (AIA), 1998. Buildings at Risk, MultiHazard Design for Earthquakes, Winds and Floods, Washington, DC.

AIA, 2007. AIA Handbook for Disaster Assistance Programs, AIA Communities 

by Design: Disaster Assistance Program, Revised August 24, 2007.

Arnold, C., 1993. Reconstruction After Earthquakes, Chapter V, “Tokyo, 

Japan 1923 and 1945,” Building Systems Development, Inc., Palo Alto, 

CA.

American Society of Civil Engineers (ASCE) 2005. Minimum Design Loads 

for Buildings and Other Structures, ASCE 7-05, Structural Engineering 

Institute, Reston, VA.

ASCE, 2010. Minimum Design Loads for Buildings and Other Structures, 

ASCE 7-10, Structural Engineering Institute, Reston, VA.

Bendimerad, F., 1996. “Earthquake Scenarios in Three Cities. San 

Francisco, Los Angeles and Tokyo,” Proceedings of the 11th World 

Conference on Earthquake Engineering, Acapulco, Mexico.

Federal Emergency Management Agency (FEMA), 2003a. Reference 

Manual to Mitigate Potential Terrorist Attacks Against Buildings, FEMA 426, 

Washington, DC.

FEMA, 2003b. The NEHRP Recommended Provisions for Seismic Regulation 

for New Buildings, FEMA 450, Washington, DC.

FEMA, 2003c. Primer to Design Safe School Projects in Case of Terrorist Attacks, 

FEMA 428, Washington, DC.

National Fire Protection Association (NFPA), 1989. Special Report on 

Educational Property Structure Fires in the United States.

NFPA, 2009a. NFPA 101: Life Safety Code, 2009 Edition, Quincy, MA, 2009.
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Making Schools Safe 4From Earthquakes

4.1 Introduction

T his chapter outlines the earthquake risk to schools and the processes and methods that can be used to reduce it. An explanation 

of the nature and probability of earthquakes is provided, together with procedures for determining the earthquake threat to specific 

locations and for evaluating the vulnerability of a school building. An 

assessment of the scope and effectiveness of seismic building codes is 

followed by a description of current methods of designing for seismic 

resistance in new buildings and upgrading existing buildings. Lastly, 

this chapter presents guidance for school districts, facility planners, and 

designers on determining acceptable risk and the use of performancebased design. 
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4.2 The Nature and Probability of Earthquakes

Although earthquakes cannot be prevented, modern science and 

engineering provide tools that can be used to reduce their effects. Science can now identify, with considerable accuracy, where 

earthquakes are likely to occur and what forces they will generate. This 

information is readily available and can be obtained for local geographic regions (see Section 4.2.3). 

4.2.1 Earthquakes and Other Geologic Hazards

Earthquakes have long been feared as one of nature’s most terrifying phenomena. Early in human history, the sudden shaking of the earth and the 

death and destruction that resulted were seen as mysterious and uncontrollable. We now understand the origin of earthquakes and know that they 

must be accepted as a natural environmental process. Scientific explanations, however, have not lessened the terrifying nature of the earthquake 

experience. Other types of phenomena sometimes accompany seismic 

ground shaking and are generally identified as geologic hazards:

n Liquefaction occurs when loose granular soils and sand in the presence of water change temporarily from a solid to a liquid state when 

subjected to ground shaking. Soils that are loose, not well graded, 

and saturated with water are prone to liquefaction. These conditions 

often occur near waterways such as rivers, lakes, and bays, but not always. In addition to the soil type, the probability of liquefaction also 

depends on the depth from the surface to the vulnerable soil layer, 

and the intensity of ground motion. Further, the results of liquefaction can vary from a small, uniform ground settlement across a site, 

to loss of foundation bearing, resulting in extreme ground settlement 

and horizontal movement of tens of feet (called lateral spreading). 

Lastly, the risk of liquefaction is directly dependent on the earthquake 

risk. Due to this complex set of conditions, damage potential from 

liquefaction is difficult to map. For all but the smallest projects, many 

building jurisdictions in seismic areas require that the liquefaction 

potential be assessed in a site-specific geotechnical report, particularly 

in areas of known potential vulnerability. On sites where liquefaction 

is more than a remote possibility, the likely results of liquefaction at 

the ground surface or at the building foundations is also estimated. 

Small settlements may be tolerated without mitigation. Larger potential settlements can be prevented by site remediation measures, 

if economically justified. Building on sites with potential massive liquefaction and lateral spreading may not be cost effective. Officials in 

some regions of high seismicity have developed maps of local areas 

that are potentially susceptible to liquefaction and require site-specific investigation before building/permitting begins.
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n Landslides, which involve the slipping of soil and rock on sloping 

ground, can be triggered by earthquake ground motion (see Figure 

4-1). The shaking from earthquakes can cause landslides, depending 

on the slope, type, and configuration of soil stratum. Landslides can 

cause damage to improvements built within the slide area or near 

the top of the slide, ranging from complete destruction to distortion from relatively small vertical or lateral movements. Sites can also 

be threatened by landslides occurring uphill, sometimes completely 

offsite and quite a distance away. 

Similar to liquefaction, accurate probability of land sliding is difficult to 

map on a regional or national scale, and this threat is normally identified in site-specific geologic hazard studies. Also similar to liquefaction, 

the largest portion of the risk may be a triggering event. In some cases, 

stabilizing small areas at risk of potential landslides may be possible 

and cost effective. Stabilizing larger areas at risk of landslides may not 

be feasible. Some regions of high seismicity have developed maps of 

the areas susceptible to landslides based on average slopes, geologic 

soil types, and the past history of sliding. Building jurisdictions require 

site-specific investigations for sites within these susceptible zones.

n Tsunamis are seismic wave movements in the ocean that travel at 

high speed and may result in large coastal waves of 30 feet or more. 

They are sometimes, and incorrectly, called tidal waves. Researchers 

have studied tsunamis for many years. Sites near large bodies of 

Figure 4-1: 

School in Anchorage, AK, 

1964, severely damaged 

by earthquake-induced 

landslide

SOURCE: NATIONAL 

INFORMATION SERVICE FOR 

EARTHQUAKE ENGINEERING, 

UNIVERSITY OF CALIFORNIA, 

BERKELEY
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water at elevations 50 feet or less above the water surface are susceptible. Although similar to storm surge, the height and the potential 

velocity of a tsunami wave represent a separate hazard and must be 

mapped separately. In addition to dependence on local conditions, 

quantification of the risk from tsunamis is difficult because not every 

earthquake generates such a wave. Studies considering the individual characteristics of the site and the facility are required to establish 

the risk and identify possible mitigating measures.

n Seiches are similar to tsunamis, but take the form of sloshing in 

closed lakes or bays; they have the potential to cause serious damage, although such occurrences have been very rare. 

For all of the above geologic hazards, the only truly effective defense 

is the application of good land-use practices that limit development in 

hazard-prone locations. Seismic design and construction is aimed at 

reducing the consequences of seismic ground shaking, which is the primary cause of damage and casualties from an earthquake. 

4.2.2 Earthquakes: A National Problem 

The U.S. Congress recognized earthquakes as a national problem in 1977 

when it passed legislation authorizing the National Earthquake Hazards 

Reduction Program (NEHRP) to reduce risks to life and property in the 

United States that result from earthquakes. NEHRP has supported considerable research and hazard mitigation efforts since that time. 

Most people now know that, although most frequent in California and 

Alaska, earthquakes are not restricted to just a few areas In the United 

States. In fact, two of the greatest earthquakes in U.S. history occurred 

not in California, but near New Madrid, Missouri, in 1811 and 1812. In 

the International Building Code (IBC) (ICC, 2009), the most common 

model building code in use in the United States and its territories, buildings on sites with a low enough seismic risk that specific design for seismic 

forces is not required are classified as Seismic Design Category (SDC) 

A. As shown in Figure 4-2, 37 of 50 States have regions with sufficient 

seismic risk to require designs more stringent than SDC A. The likelihood of a damaging earthquake occurring west of the Rocky Mountains, 

and particularly in California, Oregon, Washington, Alaska, and Utah, is 

much greater than it is in the East, Midwest, or South. However, the New 

Madrid, MO, and Charleston, SC, regions are subject to potentially more 

severe earthquakes with a lesser probability. According to the IBC design 

maps, and the USGS hazard maps, on which they are based, other locations should also plan for intermediate ground motions.
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Figure 4-2: States with seismic risk 

Records show that some seismic zones in the United States experience 

moderate to major earthquakes approximately every 50 to 70 years, while 

other areas have “recurrence intervals” for the same size earthquake of 

about 200 to 400 years. These frequencies of occurrence are simply statistical probabilities and one or several earthquakes could occur in a much 

shorter than average period. Based on current knowledge, schools to be 

located in earthquake-prone regions must be designed assuming that a 

large earthquake is likely to occur at any time. 

Moderate and even very large earthquakes may occur in areas of normally low seismicity. Even buildings in these regions are vulnerable to 

seismic damages if not constructed in accordance with building code requirements for seismic resistance. In high seismic regions, however, the 

earthquake threat is quite familiar. Schools in many areas of California 

and Alaska will be shaken by an earthquake perhaps two or three times 

a year and, since the early 20th century, have been built to incorporate 

some level of earthquake-resistant design. While the areas where earthquakes are likely to occur and the potential size or magnitude of these 

earthquakes are well identified, predicting the near-term occurrence of 

a damaging earthquake is not yet possible. Lacking useful predictions, it 

makes sense in any seismic region to take at least the minimum affordable 

prudent actions to save lives. Because most lives are lost in earthquakes 

when buildings collapse, U.S. seismic building code provisions require 

the minimum measures necessary to prevent building collapse.
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In California, schools are further protected by the Field Act of 1933, 

which mandated additional requirements relating to design qualifications, plan checking, and site inspection. The Field Act is discussed in 

more detail in Section 4.3.2.

The following graphics explain some earthquake terminology and characteristics of ground motion.

What Earthquakes Do

The Origin of Earthquakes

This diagram explains some of the common 

terms used in talking about earthquakes. 

Waves of vibration radiate out from the fault 

break.

Types of Seismic Waves

Four main types of waves radiate from a fault 

break. The P or Primary wave, a back-andforth motion, arrives first, followed by the S 

wave (secondary or shear) that is more of 

a rolling motion. These are deep waves that 

travel through the earth to the surface. The 

Love and Rayleigh waves, named after their 

discoverers, travel along the earth’s surface.

Motion at Site

Scratch left on a floor by a kitchen range in the 

1933 Long Beach earthquake that shows the 

random nature of earthquake motion.
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Acceleration Forces

Forces and Gravity

Because ground motion waves produce 

inertial forces within structures, these forces 

obey Newton’s Second Law of Motion. This 

fundamental equation establishes the forces 

for which buildings must be designed to resist 

earthquakes.

Acceleration

The acceleration, or the rate of change of the 

velocity of the waves that set the building in 

motion, is used in an equation, derived from 

Newton’s Second Law of Motion to estimate 

the percentage of the building mass or weight 

that must be dealt with as a horizontal force.

Acceleration

Some common examples of acceleration. 

The skydivers are falling under the action of 

gravity, 1g.
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Period and Resonance

Fundamental Period and Resonance

Every object has a fundamental period at 

which it vibrates if it is set in motion. 

It cannot vibrate at another period unless it 

is dragged back and forth. The ground also 

has a fundamental period. If an object is set 

in motion by an external force such as ground 

shaking, which is at the fundamental period of 

the object, the result will be “resonance” and 

the motion of the object will tend to increase. 

When you push a child on a swing, you 

instinctively give it a push at its fundamental 

period, which results in an enjoyable increase 

in the motion with very little force applied.

Similarly, if the ground pushes a building with the same period as the motion, the accelerations in 

the building will increase, perhaps four or five times.

Fundamental Period in Seconds

This shows typical periods for structures. 

The main determinant of period is building 

height and proportion; thus, a tall slender 

object will have a long period and sway back 

and forth quite slowly while the 40-story building will sway gently back and forth once every 

7 seconds.

SOURCE: ARNOLD AND ALEXANDER, 2001.

4.2.3 Common Measures of Earthquakes

Perhaps the most familiar measure of earthquakes is the Richter 

Magnitude, devised by Professor Charles Richter of the California 

Institute of Technology in 1935. Richter’s scale is based on the maximum 

amplitude of certain seismic waves recorded on a standard seismograph 

at a distance of 100 kilometers (km) from the earthquake epicenter. 

Because the instruments are unlikely to be exactly 100 km from the 

source, Richter devised a method to allow for the diminishing of wave 
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Magnitude is not a measure of damage, 

but a physical characteristic of an earthquake. An earthquake with magnitude 6.7 

that occurs in a remote area may cause 

no damage to manmade structures, but 

one with the same magnitude can cause 

considerable damage if it occurs close to 

an urban area.

amplitude with increased distance. The Richter 

scale is logarithmic, and each unit of magnitude indicates a ten-fold increase in wave amplitude. The 

energy level is multiplied by approximately 31 times 

for a unit increase in Richter magnitude scale. The 

scale is open-ended, but a magnitude of about 9.5 

represents the largest earthquake scientists now 

expect within the current understanding of movement in the earth’s crust. 

Among scientists, the Richter Magnitude has been replaced by the 

Moment Magnitude, a similar measure of energy that is based on the 

physical characteristics of the fault rupture, which is a more useful measure for large events. The Moment Magnitude scale produces values 

similar to the Richter scale, and for damaging earthquakes, values are 

normally in the 5.5 to 8.0 range, although magnitudes over 9.0 also occur.

The level of earthquake damage is often measured by intensity scales; 

one common scale used in the United States is the Modified Mercalli 

Intensity (MMI) scale, reported in Roman Numerals from I to XII. MMI 

is often incorrectly used to measure the size of an earthquake. In fact, the 

MMI is assigned to small areas, like zip codes, based on the local damage 

to structures or movements of soil. Many MMIs can be associated with a 

single earthquake because the shaking, and therefore the damage, diminishes as the distance to the epicenter increases. Although the MMI is 

useful for the purpose of comparing damage from one event to another 

(particularly events for which little or no instrumental measurements are 

available), it is very subjective, and scientists and engineers prefer instrumental measurements of the ground shaking to measure intensity.

Scientists and engineers need measures of the damaging characteristics 

of earthquakes to compare the inherent risk at different locations, and 

to develop design solutions to limit damage to acceptable levels. The universal characteristic of earthquakes, and the one that can be measured 

most precisely, is ground motion. Extensive networks of instruments are 

now employed on the ground and in buildings and other structures to 

record continuously the motions during an earthquake. The ever-growing database of earthquake recordings can be analyzed in various ways 

to develop appropriate measures of intensity that best predict potential 

damage to buildings and other structures, nonstructural systems, and the 

possibility of liquefaction and landslides. 

Table 4-1 shows significant earthquakes (Magnitude VI or over) that occurred in 47 of the 50 U.S. States between 1568 and 1989.
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Table 4-1: Known historic (1558–1989) earthquakes in 47 U.S. States

Number of Quakes with Reported Maximum 

Modified Mercalli Intensity (MMI) of:

State VIa VIIb VII+

Alabama 5 7 —

Alaska 41 21 13

Arizona 11 3 1

Arkansas 8 3 2

California 329 131 66

Colorado 19 1 —

Connecticut 2 1 —

Delaware — 1 —

Florida 2 — —

Georgia 5 — —

Hawaii 30 13 10

Idaho 12 4 2

Illinois 18 12 —

Indiana 5 2 —

Kansas 4 2 —

Kentucky 8 1 —

Louisiana 1 — —

Maine 7 2 —

Massachusetts 8 7 3

Michigan 1 1 1

Minnesota 3 — —

Mississippi 2 — —

Missouri 14 2 3

Montana 35 4 5

Nebraska 4 2 —

Nevada 28 10 8

New Hampshire 7 2 —

New Jersey 5 1 —

New Mexico 29 10 8

New York 16 6 2

North Carolina 5 2 —

North Dakota 1 — —
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Table 4-1: Known historic (1558–1989) earthquakes in 47 U.S. States

Number of Quakes with Reported Maximum 

Modified Mercalli Intensity (MMI) of:

State VIa VIIb VII+

Ohio 9 5 1

Oklahoma 9 2 —

Oregon 10 1 —

Pennsylvania 7 1 —

Rhode Island 1 — —

South Carolina 17 2 1

South Dakota 6 — —

Tennessee 12 2 —

Texas 7 1 —

Utah 31 8 5

Vermont 1 — —

Virginia 12 1 1

Washington 37 6 3

West Virginia 1 — —

Wyoming 8 1 —

Notes:

a. Felt by all. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.

b. Damage negligible in buildings of good design and construction; slight to moderate in wellbuilt ordinary structures; considerable damage in poorly built or badly designed structures; 

some chimneys broken.

4.2.4 Determination of Local Earthquake Hazards

Earthquake hazard maps are available in model codes, such as the IBC, 

and standards such as ASCE 7. Values representing ground shaking 

hazard are mapped for building periods of 0.2 second and 1.0 second. 

Examples of these maps are shown in Figure 4-3. Building codes and 

standards allow engineers to calculate the appropriate spectral response 

value for other building periods, as shown in Figure 4-4. Mapped values 

are for a hypothetical earthquake with a 2-percent probability of exceedance in 50 years. Site class, which is a measure of soil conditions at the 

building site, is also described in building codes and standards and influences the determination of ground shaking hazard at the building site. 

Site Class A represents hard rock, and Site Class E represents a very soft 

site with potential soil failure.
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More detailed information on the seismic hazard than is shown on the 

code maps, such as those in the IBC or ASCE 7, can be obtained from the 

USGS Earthquake Hazards Program Web site at http://earthquake.usgs.

gov/. The USGS provides more detailed earthquake hazard maps for 

general regions such as the western, central, and eastern United States. 

The USGS provides more localized seismicity information for any location in the United States on the basis of latitude and longitude or zip 

code. This information can be obtained by downloading the Ground 

Motion Parameter Calculator at http://earthquake.usgs.gov/hazards/

designmaps/javacalc.php. The calculator provides the seismic design parameters generally needed to conform to current building codes. 

Figure 4-3: Examples of national seismic hazard maps

Figure 4-4:

Representative shapes of 

building code (or design) 

response spectra for 

different soils
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4.3 Vulnerability: What Earthquakes Can Do to 

Schools

Much of the information developed on what earthquakes can do 

to schools comes from California because of the prevalence of 

earthquakes in that State. In general, the seismic performance 

of newer buildings has been good, although considerable costly and 

dangerous nonstructural damage still occurs. California public school 

design and construction has been subject to strict regulation since 1933, 

which undoubtedly contributes to good performance. Many of the damage examples shown in this section are of older school buildings, which 

reflects the continued use of long-lived school buildings constructed in 

the early 20th century.

4.3.1 Vulnerability of Schools

Older unreinforced masonry school buildings present a very high seismic 

risk, and have been prohibited by law in California since the mid-1930s 

following severe damage to schools of this type in the 1933 Long Beach 

earthquake. Mid-rise nonductile reinforced concrete frame structures 

pose an even greater risk. “Nonductile” refers to the frame’s lack of ductility (flexibility), or ability to deform considerably before breaking (see 

Figure 4-5). Reinforced concrete frames are made ductile by introducing an appropriate, code-specified amount of specifically designed steel 

reinforcing. Unfortunately, the need for this ductility was not recognized 

in seismic codes until the mid-1970s, so a large inventory of nonductile 

structures is still in use (see Figure 4-6).

Bent metal

Broken 

plastic

brittle

Ductile

Nonductile

Nonductile materials

(like poorly reinforced concrete)

fail without warning in a brittle manner

Ductility is the characteristic of materials such as steel that fail 

only after considerable deformation 

has occurred.

Ductility Figure 4-5:

Ductility 

SOURCE: ARNOLD AND 

ALEXANDER, 2001
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Wood frame structures perform effectively, provided that they are well 

constructed with code-specified nailing of shear walls and properly detailed roof-to-wall connections. Good maintenance, ensuring continued 

protection against moisture and insects, is also critical to the performance of wood frame structures. Newer structures, employing frames 

and fewer walls, also perform effectively if well designed and constructed 

in accordance with building codes. Their response differs from that of 

shear wall structures, which are stiff and resistant to lateral forces. Frame 

structures can be more flexible than rigid shear wall structures because 

the forces on the structural members are reduced. 

Modular structures, often used as temporary classrooms, are liable to topple off their foundations during an earthquake, unless securely attached 

and braced. This damage is not life-threatening, but makes the building unusable; fractured power, gas, and waste lines may be a hazard (see 

Figure 4-7).

Figure 4-6: 

Collapse of portion of 

nonductile concrete 

frame school structure, 

Helena, MT, 1935

SOURCE: NATIONAL 

INFORMATION SERVICE FOR 

EARTHQUAKE ENGINEERING, 

UNIVERSITY OF CALIFORNIA, 

BERKELEY

Figure 4-7: 

Modular classrooms 

pushed off their 

foundations; note stairs 

at left, Northridge, CA, 

1994

SOURCE: GARY MCGAVIN,

REDLANDS, CA
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If the structure type employs long-span roof 

and floor members, seismic forces may cause 

excessive drift, or sway, which can damage nonstructural components, such as hung ceilings, 

light fixtures, light partitions, and contents. 

Storage units, filing cabinets, and library shelving 

in any type of structure can be hazardous if not 

properly braced (see Figure 4-8), as can heavy 

equipment (see Figure 4-9). Piping, ductwork, 

electrical conduits, and communication pathways (cable trays) may also be damaged. Broken 

pipes can create additional hazards in the form 

of flooding or loss of water for fire protection.

School occupants are particularly vulnerable to 

nonstructural damage. Although students and 

staff may duck under desks and be safe from falling objects such as lighting fixtures and ceiling 

tiles, ceiling components that fall in hallways 

and stairs can make movement difficult, particularly if combined with power failure and loss 

of lighting. Wall-mounted televisions or ceilingmounted liquid crystal display (LCD) projectors 

are common in schools and present additional 

falling hazards.

Pendant light fixtures may fall if they are not securely attached and not designed to swing freely 

(see Figure 4-10). Large glass walls and windows, 

not designed to accommodate inter-story drift 

due to seismic forces, present another hazard for 

Figure 4-8: 

Fallen filing cabinets and shelves, Northridge, CA, 

1994

SOURCE: GARY MCGAVIN, REDLANDS, CA

Figure 4-9: 

Fallen shop equipment, 

Coalinga, CA, 1983

SOURCE: GARY MCGAVIN, 

REDLANDS, CA
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densely occupied classrooms as demonstrated in 

California schools that have suffered from recent 

earthquakes. Incorporating glazing designed to 

resist wind-borne debris and physical attack, as 

well as glazing support systems that can accommodate inter-story drift, can reduce the hazards 

caused by earthquake motion. 

Heavy lath and plaster ceilings in older auditoriums (and assembly buildings) can also be 

dangerous depending on their attachment and 

materials (see Figure 4-11).

4.3.2 Earthquake Damage to Schools 

Most available information on earthquake damage to schools comes from California. Its high 

incidence of earthquake activity has led to the 

adoption of sophisticated seismic building codes 

for all buildings, and special plan checking and inspection requirements, enforced by the State, for 

school buildings. 

Considering the number of significant earthquakes in California since the early years of the 

20th century, severe structural damage to schools 

and casualties has been relatively limited, except 

in the Long Beach earthquake of 1933. No student has been killed or seriously injured in a California school during an 

earthquake since 1933. In the Long Beach earthquake, which struck at 

5:55 p.m. on March 10, 1933, damage to unreinforced masonry (URM) 

Figure 4-10: 

Fallen light fixtures, library, Coalinga, CA, 1983

SOURCE: GARY MCGAVIN, REDLANDS, CA

Figure 4-11: 

Fallen heavy lath and 

plaster ceiling across 

auditorium seating, 

Northridge, CA, 1994

SOURCE: GARY MCGAVIN, 

REDLANDS, CA
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school buildings was so severe that there would have been many casualties had they been occupied (see Figures 4-12, 4-13, and 4-14). As a 

result, the State passed the Field Act within a month of the earthquake.

The Field Act required that all public school buildings be designed by a California-licensed architect 

or structural engineer, that plans be checked by 

the then Department of General Services, and 

that construction be continuously inspected by 

qualified independent inspectors retained by the 

local school board. The Department of General 

Services set up a special division, staffed by structural engineers, to administer the provisions of 

the Act. The Field Act, which is still enforced today, has greatly reduced structural damage to 

California schools.

The earthquake also resulted in the passage of the 

Riley Act, which governed the design of all buildings, with a few exceptions. The Riley Act required 

all buildings in the State be designed to a specified 

lateral force, and effectively outlawed unreinforced masonry construction.

Figure 4-12: 

Damage to the John Muir 

School, Long Beach, CA, 

1933

SOURCE: NATIONAL INFORMATION 

SERVICE FOR EARTHQUAKE 

ENGINEERING, UNIVERSITY OF 

CALIFORNIA, BERKELEY

Figure 4-13: 

Damage to shop building, Compton Junior High School, 

Long Beach, CA, 1933

SOURCE: NATIONAL INFORMATION SERVICE FOR EARTHQUAKE 

ENGINEERING, UNIVERSITY OF CALIFORNIA, BERKELEY 
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In 1952, Kern County, in the Bakersfield region, some 70 miles north of 

Los Angeles, experienced a series of earthquakes. Two groups of earthquakes occurred; the first, in the last week of July, included one with 

a magnitude of 7.6 on the Richter scale. The second group occurred 

in late August, and one earthquake, near the city of Bakersfield, had a 

magnitude of 5.9 on the Richter scale. Ten deaths resulted from the July 

earthquake and two from the August earthquake.

The Bakersfield earthquakes are of particular interest because the 

incidence of school damage is comparable to that resulting from earthquakes striking today in regions where seismic codes have not been 

adopted and enforced due to the rarity of seismic events (see Figures 

4-15, 4-16, and 4-17).

Figure 4-14: 

A dangerous 

passageway between 

two buildings, 

Polytechnic High School, 

Long Beach, CA, 1933

SOURCE: NATIONAL 

INFORMATION SERVICE FOR 

EARTHQUAKE ENGINEERING, 

UNIVERSITY OF CALIFORNIA, 

BERKELEY

Figure 4-15: 

A heavy corridor lintel 

ready to fall, Emerson 

School, Bakersfield, 

Kern County, CA, 1952

SOURCE: NATIONAL 

INFORMATION SERVICE FOR 

EARTHQUAKE ENGINEERING, 

UNIVERSITY OF CALIFORNIA, 

BERKELEY
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Figure 4-16: 

Overturned shop equipment and failed light fixtures, Kern 

County, CA, 1952

SOURCE: NATIONAL INFORMATION SERVICE FOR EARTHQUAKE 

ENGINEERING, UNIVERSITY OF CALIFORNIA, BERKELEY

Figure 4-17: 

Destroyed exit corridor, 

Bakersfield, Kern 

County, CA, 1952

SOURCE: NATIONAL 

INFORMATION SERVICE FOR 

EARTHQUAKE ENGINEERING, 

UNIVERSITY OF CALIFORNIA, 

BERKELEY
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

There were no school-related casualties in 1952, as the earthquakes occurred outside school hours. At that time, the Field Act had been in 

force for nearly 20 years, and the newer schools had been constructed to 

conform to its requirements. Of the 58 masonry schools in the region, 18 

had been constructed after the Field Act. Of these, one school constructed of grouted reinforced brick and incurred approximately 1 percent, 

or moderate, damage. Of the 40 non-Field Act schools, 1 collapsed, 

15 suffered severe damage, and 14 suffered moderate damage. In the 

Bakersfield City School District, 175 classrooms and 6,500 students were 

displaced and only about 10 classrooms were quickly put back in service. 

Nonstructural damage to ceilings and light fixtures was considerable. 

Other States have experienced similar damage to URM and early reinforced concrete structures. Schools in Helena, MT, suffered considerable 

damage in 1935 (see Figure 4-18). In 1949, several URM schools in 

Seattle were severely damaged, resulting in one fatality (see Figures 4-19 

and 4-20). At Puyallup High School, three boys on a stage just managed 

to escape when the roof collapsed (see Figure 4-21). The furniture and 

contents also sustained widespread damage (see Figure 4-22). 

Figure 4-18: 

Typical school damage, 

Helena, MT, 1935

SOURCE: NATIONAL 

INFORMATION SERVICE FOR 

EARTHQUAKE ENGINEERING, 

UNIVERSITY OF CALIFORNIA, 

BERKELEY
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Figure 4-19: 

The student body president was killed here by falling 

brickwork, Seattle, WA, 1949

SOURCE: EARTHQUAKE ENGINEERING RESEARCH INSTITUTE, 

OAKLAND, CA. PHOTO FROM A.E. MILLER COLLECTION, UNIVERSITY OF 

WASHINGTON ARCHIVES

Figure 4-20: 

Another dangerous entry 

collapse, Seattle, WA, 1949

SOURCE: EARTHQUAKE 

ENGINEERING RESEARCH 

INSTITUTE, OAKLAND, CA. 

PHOTO FROM SEATTLE SCHOOL 

ARCHIVES
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

Figure 4-21: 

Collapse of roof over stage, Seattle, WA, 1949

SOURCE: NATIONAL INFORMATION SERVICE FOR EARTHQUAKE 

ENGINEERING, UNIVERSITY OF CALIFORNIA, BERKELEY

Figure 4-22: 

Damage to library 

shelving, Seattle, WA, 

1949

SOURCE: NATIONAL 

INFORMATION SERVICE FOR 

EARTHQUAKE ENGINEERING, 

UNIVERSITY OF CALIFORNIA, 

BERKELEY
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4.3.3 Significant School Damage in U.S. Earthquakes

In the Anchorage, AK, earthquake of 1964, which registered 8.4 on the 

Richter scale, a number of public schools were damaged, but none collapsed. The earthquake occurred on Good Friday at 5:36 p.m. when the 

schools were unoccupied. The most seriously damaged school (shown in 

Figure 4-1) was subsequently demolished. At the West Anchorage High 

School (see Figures 4-23 and 4-24), a two-story nonductile concreteframe and shear-wall classroom wing suffered severe structural damage 

and the near total failure of a number of columns. Structural distortion 

also created a number of severe glass breakages. The second floor was 

removed during reconstruction and the first floor was repaired and retained. In the San Fernando, CA, earthquake of 1971, there were no 

injuries and no schools collapsed; however, the earthquake caused $13.2 

million in damages (in 1971 dollars), and 100 pre-Field Act schools were 

demolished within 11⁄2 years after the earthquake. 

A survey of 1,544 public school buildings showed that only three schools 

sustained severe damage as a result of the magnitude 6.9 Loma Prieta 

(San Francisco Bay area) earthquake of 1989. A portable classroom near 

Santa Cruz was rocked off its unbraced and unanchored supports. An 

elementary school in Los Gatos was subjected to severe shaking, but damage was limited to nonstructural and contents shifting, except in one 

classroom wing, where ground heaving raised and cracked the floor slab, 

jamming a door and window shut. 

Figure 4-23: 

Severe structural damage 

to the West Anchorage High 

School, Anchorage, AK, 1964

SOURCE: NATIONAL INFORMATION 

SERVICE FOR EARTHQUAKE 

ENGINEERING, UNIVERSITY OF 

CALIFORNIA, BERKELEY
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

Figure 4-24: 

Brittle failure at nonductile concrete column, 

West Anchorage High School, 1964

SOURCE: NATIONAL INFORMATION SERVICE FOR EARTHQUAKE 

ENGINEERING, UNIVERSITY OF CALIFORNIA, BERKELEY

Tagging

A post-earthquake evaluation procedure has been developed in California that employs colored 

placards, or “tags,” affixed to buildings, that show that the building has been inspected and indicate 

the level of safety. The colors of the tags and their safety level classification follow:

A red tag indicates UNSAFE: Extreme hazard, may collapse. Imminent danger of collapse 

from an aftershock. Unsafe for occupancy or entry, except by authorities.

A yellow tag indicates LIMITED ENTRY: Dangerous condition believed to be present. Entry 

by owner permitted only for emergency purposes and only at own risk. No usage on continuous basis. Entry by public not permitted. Possible major aftershock hazard.

A green tag indicates INSPECTED: No apparent hazard found, although repairs may be 

required. Original lateral load capacity not significantly decreased. No restriction on use or 

occupancy.

SOURCE: ATC, 1995

A San Francisco High School suffered severe structural cracking from the 

Loma Prieta earthquake. The school was constructed in 1920 as an automobile manufacturing building and was structurally upgraded in 1947. 

Restoration costs after the earthquake were estimated at $10 million. 
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Total restorations for the San Francisco school district were estimated to 

be $30 million; for Oakland, the district losses were $1.5 million. Though 

undamaged, an elementary school in San Francisco was closed because 

of the potential collapse of a nearby elevated freeway structure, which 

was considered a hazard to the building and its occupants. Hazards from 

unbraced and unanchored nonstructural items were evident in many 

buildings, including pendant-mounted light fixtures, suspended acoustical ceilings, and unanchored furniture and contents such as filing 

cabinets and shelving.

In the Northridge, CA, earthquake of 1994, 17 school buildings were red 

tagged and 89 buildings were yellow-tagged. All of the public schools in 

this area, except for one, were capable of receiving students after postearthquake debris was cleared. In some schools, portions of the campus 

and certain structures needed to be closed to students until further evaluations could be performed, but the schools were able to open (McGavin 

1994). Examples of nonstructural damage are provided in Figures 4-25, 

4-26, and 4-27). If the schools had been in session, nonstructural damage could have caused injuries. In 1995, the California Seismic Safety 

Commission (CSSC) recommended that a percentage of future school 

bond proceeds be used to abate life-threatening nonstructural and 

building contents deficiencies in public schools (1995). In 1999, legislation was passed for public schools to address securing nonstructural 

elements, and in 2003 detailed guidelines were published to aid public 

schools in identifying and correcting nonstructural hazards (California 

Emergency Management Agency, 2003).

Figure 4-25: 

Ceiling damage, 

Northridge, CA, 1994

SOURCE: GARY MCGAVIN, 

REDLANDS, CA
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

Figure 4-27: 

Line of suspended light fixtures fallen on teacher’s 

station, Northridge, CA, 1994

SOURCE: EARTHQUAKE ENGINEERING RESEARCH INSTITUTE, 

OAKLAND, CA, AND GARY MCGAVIN, REDLANDS, CA

Figure 4-26: 

Damage to ceramic kiln, 

including fractured gas 

line, Northridge, CA, 

1994

SOURCE: GARY MCGAVIN, 

REDLANDS, CA
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

4.3.4 Consequences: Casualties, Financial Loss, and 

Operational Disruption

Casualties in California schools have been few, primarily due to regulation 

by the Field Act and by chance. Significant Alaskan and California earthquakes, from Santa Barbara (1925) to Northridge 

(1984) have all occurred outside of school hours. 

Consequently, the effects of a major earthquake 

when schools are fully occupied have not been 

experienced. In other regions, casualties have 

been few; in the Seattle earthquake of 1949, two 

school children died in Tacoma when bricks cascaded onto exit ways. The closure of other Seattle 

schools for spring vacation averted fatalities and 

serious injuries in similar building failures.

The impact of school closure as a result of damage 

is the loss of public service and severe disruption 

for students, faculty, and staff. Ultimately, the taxpayer bears the costs, but this is spread over the 

whole community, the State, and the Federal 

Government. Typically, schools are self-insured 

and do not purchase insurance on the private 

market. For a private school, closure means a serious loss of revenue; in addition to the costs of 

repair, the students may not return if the school is 

closed for a long time. Therefore, obtaining insurance may be a prudent measure. 

As with any of the natural hazards reviewed in this 

manual, an earthquake can close a school, keeping the school district from doing its main job 

(i.e., teaching students). The length of the closure 

will depend on the severity and types of damage. 

It may also depend on whether the building was 

fully insured or whether disaster assistance will be 

available quickly enough to allow speedy repairs 

and reconstruction. Sometimes repairs are put on 

hold, pending a decision on whether the building 

should be repaired or condemned.

School closures from natural disasters also result 

in social and psychological difficulties for students, 

parents, faculty, staff, and the administration during the time the school is not usable, as illustrated 

by the quotations. 

n “From the standpoint of children and 

families, after an impact is a particularly bad time for schools to be closed. 

Damaged homes and neighborhoods 

are dangerous and depressing places. 

Children are often left with no safe 

place to play when yards, playgrounds, 

and recreational programs are lost, no 

one to play with when playmates and 

friends are forced to relocate and parents are too busy dealing with survival 

and rebuilding issues to have much 

time for them.” 

n “The closing of a local school is highly 

disruptive to social networks and, 

if it becomes permanent, can rob a 

neighborhood of its identity and cohesion. One of the most dramatic effects 

that can occur to a severely impacted 

community is when a school is closed 

for a long time, maybe even permanently, due to regional depopulation 

after homes are destroyed.”

n “Getting schools reopened quickly has 

been found to be an important step 

toward rebuilding the community as a 

whole.”

n “An understudied area is the long-term 

effect of major disasters on the education and development of children.”

n “The shock of being uprooted and 

moved to a new school, even temporarily, can be very difficult for children. 

The effects can be particularly 

traumatic if they occur at a critical 

developmental time, such as the senior 

year with its preparation for college 

and graduation festivities.”

SOURCE: THE HEINZ CENTER, HUMAN LINKS TO 

COASTAL DISASTERS, H. JOHN HEINZ III CENTER 

FOR SCIENCE, ECONOMICS AND THE ENVIRONMENT, 

WASHINGTON, DC, 2002
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

4.4 Scope, Effectiveness, and Limitations of Codes

Seismic design is highly developed, complex, and strictly regulated by codes and standards. Seismic codes present criteria for the 

design and construction of new structures subject to earthquake 

ground motions in order to minimize the hazard to life and to improve 

the capability of essential facilities to function after an earthquake. To 

these ends, current building codes provide the minimum requirements 

necessary for reasonable and prudent life safety. 

Seismic code requirements include:

n A methodology for establishing the design ground motion at any site 

based on seismicity and soil type

n Procedures for the seismic analysis of the building structure and key 

nonstructural components and systems

n Some detailed design requirements for materials, systems, and 

components

n Definitions of irregular building configurations and limitations on 

their use

n Building height limitations related to structural type and level of 

seismicity

Building codes and seismic design practices evolved rapidly as the result 

of intensive research and development in the United States and elsewhere during the second half of the 20th century. 

Building codes for cities, States, or other jurisdictions throughout the 

United States are typically based on the adoption, sometimes with more 

restrictive local modification, of a model building code. Up until the 

mid-1990s, there were three primary model building code organizations: 

Building Officials and Code Administrators International, Inc. (BOCA), 

International Conference of Building Officials (ICBO), and Southern 

Building Code Congress International, Inc. (SBCCI). In 1994, these 

three organizations united to found the ICC, a nonprofit organization 

dedicated to developing a single set of comprehensive and coordinated 

national model construction codes. The first code published by ICC was 

the 2000 IBC, which reflected the NEHRP Recommended Provisions for Seismic 

Regulations for New Buildings and Other Structures (NEHRP Provisions) 

(2000a). Later editions of the IBC reference ASCE 7 for its seismic provisions. Some jurisdictions in the country may still be using the Uniform 

Building Code (UBC) seismic provisions (its final update was in 1997), 

though most have adopted or are preparing to adopt the IBC. Provisions 

of the IBC are predominantly used throughout the United States.
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

4.4.1 The Background of Seismic Provisions in Building Codes

Building code provisions for seismic design have been available in 

the United States since the initial regulations for the protection of 

buildings against earthquakes first appeared in the UBC in California 

in 1927. Beginning in the 1950s, the earthquake-resistant design 

provisions of the three model codes used as the basis for building 

regulation in the United States were based on recommendations developed by the seismology committee of the Structural Engineers 

Association of California and contained in their publication known 

as the “Blue Book.” 

In the early 1980s, FEMA—one of the lead agencies in NEHRP—issued 

a contract to the Building Seismic Safety Council for the update and 

continued development of a seminal document, Tentative Provisions 

for the Development of Seismic Regulations for Buildings, ATC-3-06, originally published in 1978 by the ATC, a non-profit research foundation 

set up after the San Fernando earthquake of 1978 to recommend 

improvements in the seismic building code. Provisions of ATC-3-06 

subsequently provided the basis for the NEHRP Provisions (2000a), 

which was released in 1985 and continues to serve as the primary resource document for earthquake design requirements in ASCE 7. 

Building codes such as the IBC currently address seismic design primarily through reference to ASCE 7. 

4.4.2 Seismic Codes and Schools

Seismic codes are concerned primarily with types of structures and include few provisions that relate to specific occupancies. The IBC (2009) 

categorizes school buildings with occupant load greater than 250 as 

Type III: “...buildings and other structures that represent a substantial 

hazard to human life in the event of failure....” Type III buildings are 

assigned an Importance Factor of 1.25. This means that the seismic 

force calculated by use of the Equivalent Lateral Force (ELF) procedure would be multiplied by 1.25 so that schools are designed to a 

higher standard than ordinary buildings.

As previously mentioned, California K-12 schools are regulated by the 

Field Act, which singles out the design and construction of schools to 

resist earthquakes and is an important model for other States to consider. However, the Field Act is not a code; it requires that schools be 

designed by a licensed architect or structural engineer, that plans and 

specifications be checked by the Department of the State Architect, 

and that independent testing and inspection be conducted during 

construction.
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Implementing the nonstructural provisions of the seismic code will significantly reduce damage to nonstructural components and reduce the 

potential for school closings because of ceiling and lighting damage, partition failures, and loss of essential utilities. In the case of nonstructural 

provisions, the code goes somewhat beyond the structural objective of 

only reducing the risk of casualties. However, recent experience with 

earthquakes has shown that nonstructural damage to schools can be 

dangerous to the occupants, costly to repair, and operationally disruptive. Guidance on design to reduce nonstructural damage is provided 

in FEMA 74, Reducing the Risks of Nonstructural Earthquake Damage: A 

Practical Guide (1994). 

4.4.3 The Effectiveness of Seismic Codes

Building codes originated in the effort to reduce risk to health and safety, rather than reducing property loss, but as they evolved, they indirectly 

and directly assisted in reducing building damage. They establish the 

minimum standards for safety commensurate with affordability and other impacts such as measures that might create extreme inconvenience to 

occupants or seriously reduce the building’s functional efficiency.

Engineers generally agree that, based on California’s earthquake experience, regulation through a properly enforced seismic code has largely 

fulfilled the intent of ensuring an acceptable level of safety to avoid death 

and injury. The performance of school buildings in recent California 

earthquakes substantiates this; structural damage has been minimal in 

schools designed to the most recent seismic codes. Application of the 

Field Act ensures that schools are designed and constructed to more rigorous standards than most other buildings. 

However, the effectiveness of seismic codes is subject to some 

qualifications:

n The standards of code enforcement vary considerably, and smaller 

jurisdictions may not have trained engineering staff to conduct effective plan checks and inspections. 

n The nonstructural provisions of the seismic codes are often not adopted at the local level. Nonstructural components have not been 

regulated to the same level of care as structural components, and 

have been the cause of considerable economic loss and disruption 

of operation. 

n The code can be misinterpreted and design errors made due to inexperience of both designers and building officials.
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

4.5 Evaluating Existing Schools for Seismic Risk 

 and Specific Risk Reduction Methods

Several FEMA-sponsored publications are available to assist in the 

evaluation process. These guides, first developed in the 1980s, are 

used extensively. This section also provides a simple seismic evaluation checklist that focuses specifically on schools.

The procedures for seismic evaluation of schools are listed below in 

the order in which they would be used, starting with a simple screening 

process. 

4.5.1 Rapid Visual Screening

The Rapid Screening Procedure (RSP) published in FEMA 154, Rapid 

Visual Screening of Buildings for Potential Seismic Hazards: A Handbook 

(2002b), is intended as an initial step in identifying hazardous buildings 

and their deficiencies. Buildings identified by this procedure to be potentially hazardous must be examined in more detail by a professional 

engineer experienced in seismic design. Because this screening is aimed 

at providing a low-cost method of identifying large inventories of potentially hazardous buildings for public and private owners, and thus 

reducing the number of buildings that should be subject to a more detailed evaluation, it is designed to be performed from the street without 

benefit of entry into a building. 

The screening procedures can be completed in 20 to 30 minutes for each 

building. In some cases, hazardous details may not be visible, and seismically hazardous structures will not be identified as such. Nonstructural 

interior components are not evaluated. Conversely, buildings identified 

as potentially hazardous may prove to be adequate.

The RSP is most useful for large school districts, municipalities, or even 

States that wish to get an economical preliminary evaluation of the seismic risks faced by their school inventory. The procedure is not intended 

to provide a definitive evaluation of the individual buildings. 

The RSP is based on a visual survey of the building and a data collection 

form used to collect critical information. The collection form includes space 

for sketches and a photo of the building, as well as pertinent earthquakesafety related data. FEMA 154 provides the inspector with background 

information and data required to complete the form (see Figure 4-28). The 

procedure is designed to be performed by individuals with some knowledge 

of buildings who are not necessarily professional architects or engineers 

and are not familiar with seismic design. It has been successfully applied by 
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

architectural and engineering students. The 

methodology enables the inspector to identify significant seismic-related defects and 

to arrive at a numerical score, with a hazard 

ranking of 1–6.

Surveyed buildings are divided into two 

categories: those that are expected to 

have acceptable seismic performance, and 

those that may be seismically hazardous 

and should be studied further. A score of 2 

is suggested as a “cut-off” based on current 

seismic knowledge (i.e., if a building has 

a hazard ranking of 2 or less, it should be 

investigated by a structural engineer experienced in seismic design).

4.5.2 Systems Checklist for School 

Seismic Safety Evaluation

Table 4-2 represents a simplified version 

of ASCE 31, Seismic Evaluation of Existing 

Buildings (2003); also see Section 4.5.3. 

This simplified version focuses on structural and nonstructural systems and 

components found in schools. The evaluation questions are organized 

by system basis and are designed to establish whether the building is a 

potential seismic hazard and, if so, what its specific vulnerabilities are. 

Use of the checklist requires some seismic engineering knowledge, but 

the information can be obtained by visual inspection and no engineering 

calculations are necessary. The checklist can be used in conjunction with 

the RSP procedure, and augments the RSP analysis because it requires 

access to the building and review of design drawings, both of which are 

likely to be available to evaluate a public school building.

The checklist can also be useful in interdisciplinary discussions between 

consultants and school district personnel, and can assist consultants in 

fee negotiation with the client. 

Figure 4-28: 

Example of rapid visual 

screening information 

form
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Table 4-2: School seismic safety evaluation checklist

System

Identifier Evaluation Question

Evaluation

Y or N or 

comment

Guidance Data References

1 Site

Is there is an active fault 

on or adjacent to the site? 

If suspected, site-specific geologic 

investigations should be performed.

Local building 

department, State 

geologist, local 

university, or local 

geotechnical consultant

Does the site consist of 

stiff or dense soil or rock?

If softer soils that can lead to force 

amplification are suspected, sitespecific geologic investigations 

should be performed.

Local building 

department, State 

geologist, local 

university, or local 

geotechnical consultant 

Are post-earthquake 

site egress and access 

secured? 

Alternative routes, unlikely to be 

blocked by falling buildings, power 

lines, etc., are desirable.

Inspection by district 

personnel/architect

Are utility and 

communications lifelines 

vulnerable to disruption 

and failure?

Security of the entire utility and 

communications network is the 

issue: the school may be impacted 

by off-site failures.

Inspection on site by 

district personnel and 

Mechanical/Electrical/Plumbing (M/E/P) 

consultants; for off site, 

contact local power and 

communications providers

Are there alternate or 

backup sources for vital 

utilities?

Alternate sources increase the 

probability of the school remaining 

functional after an event, particularly 

if the school is used for postearthquake shelter.

Inspection personnel 

and district personnel, 

M/E/P consultants, and 

local utility suppliers

1 Site

Are building setbacks 

adequate to prevent 

battering from adjacent 

buildings?

Inadequate spaces between 

building walls are common in dense 

urban settings.

ASCE 31, Section 

4.3.1.2

Is there adequate space 

on the site for a safe and 

“defensible” area of refuge 

from hazards for building 

occupants?

Outside spaces can be used as 

safe post-earthquake assembly 

areas for school occupants and 

possibly the community. 

Inspection personnel 

and district personnel/

architect/local 

emergency staff

2 Architectural

 Configuration

Is the architectural/

structural configuration 

regular?

Irregular vertical and horizontal 

configurations, such as re-entrant 

corners and soft first stories, 

may lead to significant stress 

concentrations.

ASCE 31, Section 4.3.2
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Table 4-2: School seismic safety evaluation checklist

System

Identifier Evaluation Question

Evaluation

Y or N or 

comment

Guidance Data References

2 Architectural

 Planning and Function 

Are exit routes, including 

stairs, protected from 

damage and clear from 

nonstructural elements 

or contents that might fall 

and block exit ways? 

Schools sometimes have large 

unbraced lockers in hallways, or 

store other materials, such as tall 

filing cabinets or bookcases, that 

may fall and block exits.

Inspection by district 

personnel

ASCE 31, Section 

4.8.11.

 Ceilings

Are suspended ceilings 

braced and correctly 

attached at walls?

Suspended ceilings easily distort 

(particularly in light and flexible 

frame structures), thus causing 

ceiling panels to fall if not properly 

designed and constructed.

ASCE 31, Section 

4.8.2. 

Are heavy plaster 

suspended ceilings 

securely supported and 

braced?

Heavy lath and plaster ceilings in 

older schools are very dangerous if 

poorly supported. 

ASCE 31, Section 

4.8.2.

 Partitions and Space Division

Are partitions that 

terminate at a hung ceiling 

braced to the structure 

above? 

Partitions need support for outof-plane forces. Attachment to a 

suspended ceiling is inadequate. 

ASCE 31, Section 4.8.1.

Are masonry or hollow tile 

partitions reinforced or 

braced, particularly those 

surrounding exit stairs? 

Heavy partitions develop strong 

earthquake forces because of their 

stiffness and mass, and are prone 

to damage. They are particularly 

dangerous around stairs and exit 

ways and occupied classrooms.

ASCE 31, Section 4.8.1

 Other Elements

Are exterior entrance 

canopies and walkways 

engineered to ensure no 

collapse?

Post-earthquake safety of these 

structures is critical to ensure safe 

exit after an event. 

ASCE 31, Section 4.8.8

Are parapets, appendages, 

etc., securely attached 

and braced to the building 

structure?

Unreinforced masonry parapets are 

especially vulnerable, as are items 

such as cornices, signs, and large 

satellite communication dishes.

ASCE 31, Section 4.8.8

Are heavy lockers, library 

shelves, and vertical filing 

cabinets that could fall 

on people braced to the 

structure?

These can topple and injure 

occupants, and also block exit ways.

ASCE 31, Section 

4.8.11
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Table 4-2: School seismic safety evaluation checklist

System

Identifier Evaluation Question

Evaluation

Y or N or 

comment

Guidance Data References

3 Structural System

Is there a continuous load 

path from the foundation 

to the roof?

This is an important characteristic to 

ensure good seismic performance. 

This also sometimes relates to 

irregularity in configuration.

Engineer to check 

design of school 

structure

ASCE 31, Section 4.3.1.

Does the structure 

provide adequate 

redundancy in the event 

of the loss of some 

structural supports?

Typical characteristics of 

redundancy include multiple lines of 

resistance and multiple bays within 

each line to distribute lateral forces. 

ASCE 31, Section 

4.4.1.1.1 and Section 

4.4.2.1.1

Is all load-bearing 

structural masonry 

reinforced according to 

code?

Unreinforced masonry has limited 

ductility and cannot withstand large 

earthquake-induced repetitive 

displacements.

Engineer to check 

against local code 

requirements

Is the structure’s 

reinforced concrete 

designed to seismic code 

later than 1976?

The reinforced concrete codes 

changed in 1976, and structures 

designed before these codes were 

adopted may be inadequate.

Check date of design, 

and edition of code 

used

Is the structure’s wood 

frame well maintained, 

with little or no 

deterioration?

Wood framing is subject to attack 

by termites and water damage, both 

of which can seriously weaken the 

structure.

School district 

personnel to inspect

Are horizontal structural 

members securely 

connected to walls and 

columns?

Good connections between all 

structural members are very 

important for structural integrity.

Structural engineer to 

check

 ASCE 31, Section 

4.6.1

Are horizontal 

diaphragms correctly 

designed and constructed 

with necessary chords 

and collectors?

Large diaphragm openings and 

the edges of diaphragms must 

be designed to ensure forces are 

properly transmitted to walls and 

frames.

Structural engineer to 

check

ASCE 31, Section 4.5.1

4 Building Envelope

 Wall Cladding

Is the building cladding 

attached to structural 

frames so that it can 

accommodate drift?

Frames are flexible and cladding 

must be detailed to accommodate 

calculated drifts and deformations.

ASCE 31, Section 4.8.4

Are heavy veneer facing 

materials such as brick or 

stone securely attached to 

the structural walls?

Shear wall structures are very 

stiff and carry large earthquake 

forces; heavy attachments must be 

securely attached. 

Structural engineer to 

check design and field 

condition 

Are heavy roofing 

materials such as tile and 

slate securely attached to 

the structure?

Installation of these materials over 

points of egress may be dangerous, 

because they may fall off and hit 

someone exiting the building and 

may also litter the exit path with 

debris.

IBC Table 1507.3.7
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

Table 4-2: School seismic safety evaluation checklist

System

Identifier Evaluation Question

Evaluation

Y or N or 

comment

Guidance Data References

4 Building Envelope

 Glazing

Are glazing and other 

panels attached so that 

they can accommodate 

drift? 

Glazing must be installed with 

sufficient bite, and adequate space 

between glass and metal. 

ASCE 31, Section 4.8.4

Is the glazing material 

inserted into a 

surrounding structure that 

limits drift and racking?

Glazing is dependent on the 

surrounding structure to limit 

racking.

Structural engineer to 

inspect framing and 

structural conditions

5 Utilities

Are building utility 

distribution systems well 

supported and adequately 

braced?

Flexible connections may be 

necessary where utilities enter the 

building.

ASCE 31, Section 

4.8.13.

6 Mechanical

Is heavy mechanical 

equipment adequately 

secured and are isolators 

provided with snubbers? 

Spring-isolated equipment must be 

restrained from jumping off isolators. 

ASCE 31, Section 

4.8.12

Is the heating piping 

properly braced and 

provided with expansion 

joints? 

Bracing and expansion joints 

increase the likelihood of continued 

post-event function.

Inspection by school 

district personnel and 

M/E/P consultants

Is ductwork properly 

supported and braced? 

Proper support and bracing 

increase the likelihood of continued 

post-event function.

Inspection by school 

district personnel and 

M/E/P consultants

Are water heaters and 

other tanks securely 

braced?

Gas heaters or tanks with 

flammable or hazardous materials 

must be secured against toppling.

ASCE 31, Section 

4.8.12

7 Plumbing

Are plumbing lines 

adequately supported and 

braced? 

Protection of joints is especially 

important.

ASCE 31, Section 

4.8.13

Is fire protection piping 

correctly installed and 

braced?

Correct installation and bracing 

increase the likelihood of continued 

post-event function.

Inspection by school 

district personnel and 

M/E/P consultants

Are ducts and piping that 

pass through seismic 

joints minimized and 

provided with flexible 

connections?

Differential movement between 

sections of the building can cause 

breakage and leaks in pipes and 

ducts if no provision is made for 

movement. If walls at joint are firewalls, 

penetrations should be fireproofed.

ASCE 31, Section 

4.8.13.2
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Table 4-2: School seismic safety evaluation checklist

System

Identifier Evaluation Question

Evaluation

Y or N or 

comment

Guidance Data References

8 Electrical

Are suspended lighting 

fixtures securely attached, 

braced, or designed to 

sway safely?

Older suspended lighting fixtures have 

performed badly in earthquakes and 

are an injury hazard.

ASCE 31, Section 4.8.3

Are light fixtures 

supported in a ceiling, 

braced, and provided with 

safety wires?

Light fixtures within a grid often fall 

when the grid is distorted, unless 

the fixtures are secured with safety 

wires.

ASCE 31, Section 4.8.3

Is heavy electrical 

equipment adequately 

secured? 

Switch gear and transformers are 

heavy and failure can shut down the 

electrical system. 

ASCE 31, Section 

4.8.12

9 Fire Alarm

Is the fire alarm system 

connected to a secondary 

power supply? 

This is also necessary to support 

daily operational needs, including 

lighting, heating, communications, 

etc., and if the building is used as a 

post-earthquake shelter.

Inspection by district 

maintenance personnel 

and M/E/P consultants 

Is the fire alarm system 

provided with a battery 

backup system capable of 

operating the system for 24 

hours after power loss?

Required by code even if the 

building will not be used after an 

event so that the school can be 

evacuated.

Inspection by district 

maintenance personnel 

and M/E/P consultants

10 Communications and IT Systems

Are communications 

components adequately 

braced and supported?

Post-event communications are vital 

for issuing instructions to school administrators, students, faculty, and staff. 

Some components, such as large satellite dish antennas, are easily damaged 

if not properly supported.

ASCE 31, Section 

4.8.12

Are building intercom 

systems connected to 

a standby generator or 

battery? 

Necessary to enable continued communications, whether loss of power is 

caused by earthquake or not.

Inspection by 

maintenance personnel 

and M/E/P consultants

11 Equipment Operations and Maintenance

12 Security Systems

13 Security Master Plan

4.5.3 Seismic Evaluation of Existing Buildings

For those buildings that, as the result of a preliminary screening, are candidates for a more detailed investigation, the Building Seismic Safety Council 

(BSSC) developed a procedure for the systematic evaluation of any type 

of building (FEMA 178, The NEHRP Handbook for the Seismic Evaluation of 

Existing Buildings (1992), later updated as FEMA 310, Handbook for Seismic 

Evaluation of Buildings: A Prestandard (1998). FEMA 310 was subsequently 

superseded by ASCE 31 (2003), a standard of the American Society of 

Civil Engineers approved by the American National Standards Institute. 
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ASCE 31 can be used to evaluate the structural and nonstructural systems and components for any type or size of individual school building. 

However, the procedure focuses on evaluating whether the building or 

building components pose a potential earthquake-related risk to human 

life. The procedure does not address code compliance, damage control, 

or other aspects of seismic performance not related to life safety.

The ASCE 31 methodology involves answering two sets of questions: one 

set addresses the characteristics of 15 common structural types and the 

other set deals with structural elements, foundations, geologic site hazards, and nonstructural components and systems. These questions are 

designed to uncover the flaws and weaknesses of a building, and are in 

the form of positive evaluation statements describing building characteristics that are essential if the failures observed in past earthquakes are 

to be avoided. The evaluating architect or engineer should address each 

statement on the checklist and determine whether an item is compliant 

or non-compliant. Compliant statements identify conditions that are acceptable and non-compliant statements identify conditions in need of 

further investigation. The handbook also details a process for dealing 

with statements on the checklist that are found to be non-compliant. 

The evaluation requires some basic structural calculations and a site visit. Follow-up field work is also necessary. The primary product of the 

evaluation is the identification building vulnerabilities that could precipitate structural or component failure. Although the procedure provides 

guidance on structural deficiencies, it is not intended to identify appropriate seismic retrofit options. The design engineer must understand the 

overall deficiencies of the building before attempting to identify retrofit 

design approaches. The overall deficiencies may be due to a combination of component deficiencies, inherent adverse design, construction 

deficiencies, deterioration, or a serious weakness in the structural and 

nonstructural systems. 

4.6 Earthquake Risk Reduction Methods

Although the general principles of design are similar for new or 

existing schools, differences in code requirements and overall 

project delivery processes reflect the design freedoms for new 

buildings and the constraints for existing ones. 

Engineering of structural and nonstructural risk reduction methods is 

similar for new and existing schools. New school design offers the possibility of construction on a site subject to less ground motion because 

of better soil conditions or further proximity to a fault. New schools can 

be designed with the most appropriate structural system, using known 
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

and tested materials and a good building configuration. These possibilities are not available when retrofitting an existing school; the building 

may have been designed to an obsolete seismic code or no code at all, 

its materials may be questionable, and the building configuration and 

structural system may be inappropriate. Therefore, the protection of an 

existing school must start with a careful evaluation of its vulnerability. 

Seismic retrofitting is expensive and time consuming; however, an incremental retrofit procedure, as described in Section 4.6.2, can help to 

keep time and cost within reasonable limits by integrating retrofits into 

normal repairs and capital improvement projects. 

4.6.1 Risk Reduction for New Schools

Methods of design for earthquake protection involve three main characteristics of the school: its site, its structure, and its nonstructural 

components. 

In terms of risk reduction, the first priority is the implementation of measures that will reduce the risk of casualties to students, staff, and visitors. 

The second priority is the reduction of damage that leads to downtime 

and disruption. The third priority is the reduction of damage and repair 

costs.

Alternative measures to achieve these objectives are as follows, in ascending order of cost:

n New Schools Regulated by Seismic Codes

n Provide personal protection training.

n Evaluate code provisions against risk priorities. Evaluate whether 

design to current code will meet acceptable risk objectives for 

damage costs and reduction of downtime.

n Consider adopting California’s Field Act model for quality control of design and construction; it can be administered by a single 

district with specification provisions for inspection in contract 

documents. 

n Use performance-based design procedures if code-based design 

does not meet acceptable risk objectives.

n New Schools Not Regulated by Seismic Codes

n Provide personal protection training. 

n Design to appropriate code standards on a voluntary basis.

n Use performance-based design procedures to meet acceptable 

risk objectives.
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

n Consider adoption of seismic code; requires community-wide 

cooperation.

Damage reduction is common to all the objectives. The following sections give an overview of the design strategies that are used to achieve 

acceptable levels of protection in new schools.

School Sites. Protection of schools and their occupants from earthquakes 

depends on correct seismic design and construction to resist the estimated earthquake forces that the building could encounter at its specific site. 

Because ground motion from a single earthquake may vary considerably, 

depending on the nature of the soil and the distance of the building from known earthquake faults, 

careful site selection is a critical first step in reducing 

the forces on the building. School sites are generally 

selected based on factors such as availability, student population, cost, convenience of access for the 

school students and staff, and general demographic concerns rather than seismicity. However, a large 

district that is developing a multi-school plan of new 

facilities should include recognition of any natural 

hazard vulnerabilities as a factor in the evaluation of 

alternative sites. A school district can reduce its seismic vulnerability in several ways:

n Locate the building in an area of lower seismicity, where earthquakes 

occur less frequently or with typically smaller intensities. Although it 

would be very rare for a school district to make a site selection decision based solely on seismic risk, moving a school even a few miles in 

some cases can make a big difference to its seismic hazard.

n Locate the building on a soil type that reduces the hazard. Local soil 

profiles can be highly variable, especially near water, on sloped surfaces, or close to faults. In an extreme case, siting on poor soils can 

lead to damages caused by liquefaction, land sliding, or lateral spreading of the soil. Similar buildings located less than 1 mile apart have 

performed in dramatically different ways in earthquakes because of 

differing soil conditions. Even when soil-related geologic hazards are 

not present, earthquake motions that have to travel through softer 

soils will be amplified more than those traveling through firm soils or 

rock. If soil types at a site are a concern, the effects of soil hazard on 

risk should be determined by a geotechnical or engineer. A professional should assess the potential vulnerabilities associated with differing 

site conditions. These vulnerabilities should be weighed against the 

costs, both direct and indirect, of locating the facility on soils that will 

result in better performance.

In the late 1960s, the small school district 

of Portola Valley, CA, was faced with 

declining enrollment for its intermediate 

school, which was also outdated. In addition, the school was located very close 

to the San Andreas Fault. Concerned 

about seismic risk, the district deemed 

the site unsuitable for school purposes 

and sold the site to the city for $1. The city 

subsequently used the site for recreational 

purposes.
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

n Engineer the building site to increase building 

performance and reduce vulnerability. If building relocation to an area of lower seismicity or 

to an area with a better natural soil profile is 

not a cost-effective option, the soil at the designated site can sometimes be treated to reduce 

the hazard. For example, on a liquefiable site, 

the soil can be grouted or otherwise treated to 

reduce the likelihood of liquefaction. Soft soils 

can be excavated and replaced, or combined 

with foreign materials to make them stiffer. 

Alternatively, the building foundation itself 

can be modified to account for the potential 

effects of the soil, reducing the building’s susceptibility to damage even if liquefaction or limited land sliding 

does occur. The school district should weigh the additional costs of 

modifying the soil characteristics or the building foundation with 

the expected reduction in damage and loss. However, because most 

schools are one or two stories in height, site area usage is considerable, and site treatment is likely to be costly.

In most cases, a designated school site will be accepted. Proposed construction directly over a fault is probably the only siting characteristic 

that would lead to rejection of an otherwise suitable location. The forces a school must be designed to withstand increase if it is near a fault, 

which increases the structural cost. Sites are assigned to one of six categories, from A, which represents hard rock, to F, which represents soils 

vulnerable to potential failure or collapse such as liquefiable soils, sensitive clays, and weak soils and clays. Variations in soil type are addressed 

in design by increasing or decreasing the design forces by application 

of a coefficient within the calculation of the ELF equation, which is 

used to establish the design lateral forces on the building. 

Reducing Damage to School Structures. Minimum standards and criteria for structural design are defined in the building codes. The codes 

provide maps that show whether the location is subject to earthquakes 

and, if so, the probability of occurrence, expressed by varying levels of 

seismic forces for which a building must be designed. Seismic codes 

are adopted by State or local authorities, so a seismically-prone region 

could be exempt from seismic code regulations if the local community 

has chosen not to adopt a seismic building code. Although a seismic 

hazard exists, based on historic and scientific data, some communities 

choose to ignore the risk, because no one has experienced an earthquake in their lifetime. Such a policy should be of serious concern to 

school district officials, the local school board, and parents. 

The ELF equation in the IBC is V=Cs W, 

where V= the shear, or pushing, force at 

the base of the building, which represents 

the total earthquake force on the building, 

and Cs

 is a coefficient representing the estimated site acceleration (derived from maps 

provided in the code) and modified by 

factors related to the characteristics of the 

structure, the importance of the building, 

and the nature of the soil. W is the weight 

of the building. 
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How Buildings Resist Earthquakes

Lateral Force Resisting Systems – 

Basic Types

This figure shows the basic types of lateral 

force resisting structural systems. They tend to 

be mutually exclusive (i.e., it is desirable not to 

mix the systems in a single building because 

of the different strength and stiffness characteristics of the systems). Shear walls are very 

stiff while moment-resistant frames are flexible. 

Braced systems are in between. 

The systems have major architectural implications. Shear walls, which should run uninterrupted from 

foundation to roof, may impose major planning constraints on a building. Moment frames create 

unobstructed floors, but, because of their special connection requirements, are expensive. They are 

subject to more deformation that may result in costly damage to nonstructural components and systems. Braced frames are a common compromise.

Diaphragms

Together with the lateral force resisting 

system, diaphragms form a horizontal 

system that connects the vertical elements 

and carries their loads down to the foundation. Large openings in the diaphragm may 

limit its ability to be effective in transferring 

forces.

SOURCE: ARNOLD AND ALEXANDER, 2001
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Although the risk may appear to be minimal, the effects of a significant 

event could be catastrophic. Communities with minimal risk may have 

no history of design for earthquakes, leaving the building stock especially vulnerable. School buildings are an important community resource 

(along with other essential buildings such as hospitals and fire and police 

stations) that should not be gambled on the avoidance of a rare event. 

Reducing structural and nonstructural damage in earthquakes depends on:

n The correct application of code criteria and analytical methods. 

Seismic codes have become increasingly complex and a high standard of care and engineering judgment is necessary to ensure correct 

application. 

n The appropriate selection and application of structural systems and 

materials. Different structural systems have varied characteristics 

that must be matched to the nature and purpose of the school. The 

following two graphics show the basic types of structural lateral force 

resisting systems.

n The correct design of critical elements such as frames, shear walls, 

and diaphragms and their connections to one another: earthquake 

forces expose the weak links between structural members. Serious 

damage and collapse is often initiated by connection failure. These 

critical elements provide seismic resistance and must be correctly 

sized, located, and detailed. 

n Careful attention to key structural design principles such as provision of a direct load path and structural redundancy. 

n The correct design of the connections between structural elements 

and nonstructural components. 

n A simple and regular building configuration (its size and shape) as

planning and aesthetic requirements permit. Experience has shown 

that certain building shapes and architectural design elements contribute to poor seismic performance and are expensive to design and build. 

n A high level of quality assurance to ensure that the building is properly

constructed. Careful seismic design is pointless if not properly executed.

n A high level of maintenance to ensure that the building retains its 

integrity over time. Corrosion of steel and termite infestation or dry 

rot in wood can seriously affect structural integrity.

The following graphics show some problems caused by irregular building configurations.
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

Some Typical Design Problems

Torsional Forces

This figure shows how torsion occurs. If the 

center of mass and center of resistance do 

not coincide, the building tends to rotate 

around the center of resistance.

Stress Concentrations

Stress concentration is the excessive concentration of forces at one or a few points of the 

building, such as a particular set of beams, 

columns, or walls. These few members may 

fail and, by a chain reaction, bring down the 

whole building.

Soft Stories

This figure shows the failure mechanism of 

a soft or weak story. A regular building with 

equal floor heights distributes its drift equally 

to each floor so that each is subjected to 

manageable drift. In the soft story building, the 

overall drift is the same, but the second floor 

connections are subject to all, or almost all, 

the drift, creating a failure mechanism.

SOURCE: ARNOLD AND ALEXANDER, 2001
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Torsional Forces and Stress Concentration

Soft Stories

Typical examples of soft story-induced damage. 

Re-entrant Corners

Buildings with re-entrant corners (L-shape, 

U-shape, etc.) are subject to torsion and stress 

concentrations. Special design measures are 

necessary to counteract these tendencies. 

Where buildings are structurally separated to 

remove stress concentrations at corners, adequate separation distance must be provided 

to prevent damages caused by pounding (e.g., 

the buildings deflecting toward each other and 

making contact.

SOURCE: ARNOLD AND ALEXANDER, 2001

Reducing Damage to Nonstructural Components and Systems. Nonstructural 

components and systems are defined as those elements that do not contribute to the seismic resistance of the building (see Figures 4-29a and 

b). They typically comprise from 75 to 80 percent of the total school 

building value, and they provide weather protection, heating, cooling, 

lighting, and acoustic control for the structure. Damage to these components can be costly and render the building functionally useless even if 

the building structure performs in accordance with the intent of the seismic code. Nonstructural components are generally broadly classified as:

n Architectural

n Exterior envelope – opaque or glazed, roof and wall coverings

n Veneers
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n Interior partitions

n Ceilings

n Parapets and appendages (e.g., signs and decorative elements) 

n Canopies and marquees

n Chimneys and stacks

n Mechanical 

n Boilers and furnaces

n HVAC source equipment and distribution components

n Electrical and Electronic

n Source power equipment and distribution components

n Source communications equipment and distribution components

n Light fixtures 

n Plumbing

n Storage vessels and tanks

n Piping systems 

n Hazardous materials (HazMat) distribution

n Furnishings and Interior Equipment 

n Bookcases, filing cabinets, and other storage 

n Shop and art equipment 

n HazMat storage

Building Structure

Figure 4-29a:

Structural and 

nonstructural elements 

of a building
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Reduction of damage to nonstructural components depends on using 

methods of support and bracing the components to avoid failure (see 

examples in Figures 4-30, 4-31, 4-32, and 4-33). Seismic codes provide the 

design force for which the nonstructural components must be designed, 

together with a number of specific design requirements that must be 

followed. 

Figure 4-29b: Structural and nonstructural elements of a building

Main Runner

Cross Runner

Vertical Strut

Safety Wires

Ceiling Grid

Figure 4-30: Suspended ceiling and light fixture bracing and support
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Horizontal Bracing to Structure

Wall Attachments

Metal Strap

Open Cells

Reinforcing

Masonry

Parapet

Drilled 

and 

Grouted 

Bolt

Channel

Brace

Roof

Blocking

Figure 4-31: 

Bracing tall shelving to 

the structure

Figure 4-32: 

Connection of 

nonstructural masonry 

wall to structure to 

permit independent 

movement

Figure 4-33: 

Bracing for existing 

unreinforced masonry 

parapet wall
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

4.6.2 Risk Reduction for Existing Schools

Procedures and Design Strategies. Additions to an existing school must 

meet all of the code requirements for a new building. Currently, no 

seismic codes apply to the retrofit of existing schools. Typically, the standards to be applied are derived from the code for new buildings and 

negotiated with the applicable building department. Bringing an existing structure into full compliance with a current code is difficult and in 

some cases impossible, so some compromises have to be made; however, 

there is no general agreement on how to apply the code for new buildings to the retrofit design of existing ones. 

Reducing the seismic risk for an existing building requires the same 

general design principles as those necessary for a new building, but the 

architect and engineer are faced with existing structural and nonstructural systems and materials that may be far from ideal. 

The process should begin with an evaluation procedure such as those 

outlined in Section 4.5. If the evaluation results in a decision to retrofit 

an existing school, the school district can use ASCE 41 to select seismic protection criteria. ASCE 41 supersedes FEMA 356, Prestandard and 

Commentary for the Seismic Rehabilitation of Buildings (2000b), and FEMA 

273, NEHRP Guidelines for the Seismic Rehabilitation of Buildings (1997b) 

and FEMA 274, NEHRP Commentary on the Guidelines for the Seismic 

Rehabilitation of Buildings (1997a), and provides the latest generation of 

performance-based seismic rehabilitation methodology. 

ASCE 41 provides methods and design criteria to achieve several different levels and ranges of seismic performance (unlike a conventional code 

that implies, but does not define, a single performance level). “Seismic 

performance” refers to the nature and extent of damage that the building exhibits as a result of an earthquake. ASCE 41 provides a thorough 

and systematic approach to performance-based seismic design to achieve 

an acceptable level of risk based on stakeholders needs. 

The performance-based design approach outlined in ASCE 41 provides 

uniform protection criteria for the retrofit of existing buildings to attain 

a wide range of performance levels for earthquakes of varying severities 

and probabilities of occurrence. To start, school districts select specific 

performance goals as a basis for design, and then evaluate the design requirements, including complexity and cost, to meet those goals. 
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Typical design strategies for improving the protection of an existing 

school include (see Figure 4-34):

n Modifying and improving local components or materials, such as 

beam/column connections. This involves retrofitting connections 

and strengthening structural members by reinforcing or replacing 

them with new components.

n Removing or reducing configuration irregularities. This involves 

providing seismic separations in irregular configurations or adding 

shear walls or bracing to reduce torsional effects, thereby strengthening and/or stiffening the entire structural system. This is a major 

retrofit that involves adding bracing or shear walls, replacing many 

structural members. 

n Reducing the mass of the building (to reduce forces). This involves 

changing the location of heavy items (e.g., bookcases) within the 

building, but would not apply to a one-story building, except where 

a tile or slate roof covering might be replaced with a lightweight 

material. 

Retrofit Methods. Seismic (base) isolation (to reduce force on the building superstructure) is a technique that has been successfully used in 

the retrofit of large buildings, but it is not generally appropriate to 

the scale and nature of school buildings unless the school building is 

considered a historical building. A newer technique is passive energy 

dissipation, the insertion of supplemental energy devices (to reduce 

movement), which might be applicable to certain types of school 

structures (e.g., large gymnasiums, multiuse buildings, or auditoriums). Seismic retrofit at any large scale is expensive, both in design 

and construction, because of the more complex analyses that must be 

conducted and the construction constraints that must be overcome. 

In addition, closure of a school for an extended period (beyond that 

of the normal summer break) is usually unacceptable. Although rare, 

some major seismic retrofit projects have been completed, primarily 

with the goal of saving a building that is not only a place of learning, 

but a historic community resource. The retrofitting of the B.F. Day 

School in Seattle is one such project (see Figures 4-35 and 4-36). 
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Increased 

strength and drift 

limitation

Increased 

strength and drift 

limitation

Containment and

drift limitation

Containment and

drift limitation

High seismic 

capacity

conventional 

damage control

High seismic 

capacity

conventional 

damage control

Infill walls

Add braces

Add buttresses

Completely rebuild

Isolate building

Add frame;

interior or exterior

Strengthening Solution Result

Figure 4-34: 

Design strategies for 

seismic retrofit of 

existing buildings

SOURCE: BUILDINGS AT RISK: 

SEISMIC DESIGN BASICS FOR 

PRACTICING ARCHITECTS,

AIA/ACSA COUNCIL ON 

ARCHITECTURAL RESEARCH, 

WASHNIGTON, DC, 1994, ERIC 

ELSESSER
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Figure 4-35: 

Retrofit of B.F. 

Day Elementary 

School, Seattle, 

WA

SOURCE: 

EARTHQUAKE 

ENGINEERING 

RESEARCH 

INSTITUTE, 

OAKLAND, CA; B.F. 

DAY ELEMENTARY 

SCHOOL , SEATTLE, 

TODD W. PERBIX 

AND LINDA L. 

NOSON, 1996

Figure 4-36: 

Sections 

and plans of 

the B.F. Day 

School: existing 

at bottom, 

retrofitted at 

top. Note that 

the retrofit has 

also opened up 

the basement 

and first floor 

to provide large 

spaces suitable 

for today’s 

educational 

needs.

SOURCE: 

EARTHQUAKE 

ENGINEERING 

RESEARCH 

INSTITUTE, 

OAKLAND, CA; B.F. 

DAY ELEMENTARY 

SCHOOL , SEATTLE, 

TODD W. PERBIX 

AND LINDA L. 

NOSON, 1996
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 4-53

MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Incremental Seismic Rehabilitation. An approach that greatly improves the 

feasibility of retrofitting a school is “Incremental Seismic Rehabilitation.” 

The principles of this process are described below. A full description 

is presented in FEMA 395, Incremental Seismic Rehabilitation of School 

Buildings (K-12) (2003c). 

Whereas extensive single-stage seismic retrofitting of an existing school 

represents a significant cost, retrofit tasks can be divided into increments 

and integrated into normal repairs and capital improvement projects. 

Implementation of incremental seismic retrofit involves assessing the 

buildings, establishing retrofit priorities, and planning integration with 

other projects. Integration reduces the cost of the seismic work by sharing engineering design costs and some aspects of construction costs. An 

“integration opportunity” occurs when a seismic retrofit measure can be 

paired with other repair or replacement tasks or categories. Integration 

opportunities are a key consideration in determining the sequence of 

retrofit tasks.

School districts often categorize maintenance and capital improvement 

projects in the following eight categories:

n Reroofing

n Exterior wall and window replacement

n Fire and life safety improvements

n Modernization/remodeling/new technology accommodation

n Under floor and basement maintenance and repair

n Energy conservation/weatherizing/air-conditioning

n Hazardous materials abatement

n Accessibility improvements

FEMA 395 provides five matrices that show possible combinations of 

seismic improvement measures with typical work categories. Table 4-3 

represents a typical matrix from FEMA 395 and shows possible seismic 

improvements relating to roof maintenance and repair.
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

Table 4-3: Roofing maintenance and repair/re-roofing

Rank*

Level of 

Seismicity

Building 

Structural 

Element

Structural 

Subsystem

Seismic Performance 

Improvement

Wood Masonry1 Concrete Steel

L M H

Unreinforced MasonryReinforced MasonryWood DiaphragmConcrete DiaphragmWood DiaphragmConcrete Diaphragm

Nonstructural

1    n/a n/a

Bracing of Parapets, 

Gables, Ornamentation, 

and Appendages

n n n n n

2    n/a n/a Anchorage of Canopies 

at Exits n n n n n n n

3   n/a n/a Bracing or Removal of 

Chimneys n n n n n n n

10   n/a n/a Anchorage and Detailing 

of Rooftop Equipment n n n n n n n

Structural

n/a   All 

Elements Load Path and Collectors       

n/a   Horizontal 

Elements Diaphragms

Attachment and 

Strengthening at 

Boundaries

n n n n  n 

n/a   Horizontal 

Elements Diaphragms Strength/Stiffness n n n n  n 

n/a   Horizontal 

Elements Diaphragms Strengthening at Openings     

n/a   Horizontal 

Elements Diaphragms Strengthening at Re-entrant Corners       

n/a   Horizontal 

Elements Diaphragms Topping Slab for Precast Concrete    

n/a    Vertical 

Elements Load Path Lateral Resisting System to Diaphragm Connection n n n m n m

n/a    Vertical 

Elements

Out-of-Plane Anchorage 

of Concrete or Masonry 

Wall

n n n  n 

* Nonstructural improvements are ranked on the basis of engineering judgment of their relative impact on improving life safety in 

schools.

Structural improvements are not ranked, but are organized by structural element and subsystem.

 Work that may be included in the building rehabilitation/maintenance/repair project using little or no engineering.

 Work requiring detailed engineering design to be included in the project.

m Work requiring detailed engineering design and evaluation of sequencing requirements. Work could redistribute loads, 

overstressing some elements.

Note 1: Masonry buildings with a concrete roof deck should use the concrete building, concrete diaphragm for integration 

opportunities.

n/a = Not Applicable.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 4-55

MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Incremental seismic retrofit is an effective, affordable, and non-disruptive strategy to mitigate seismic risk. At the lower levels of protection, 

some effective construction measures (e.g., bracing nonstructural bookcases and filing cabinets, and anchoring key desktop equipment such as 

computers) can be implemented by school district maintenance personnel. As a last resort in cases of extreme risk and badly antiquated school 

buildings, demolition is the only solution. 

4.7 The School as a Post-Earthquake Shelter

I

n the aftermath of any damaging earthquake, there is an immediate need of shelter for people who have been displaced from their 

homes. In earthquake-prone regions, school sites are often used 

to provide immediate shelter (on the day or night of the earthquake). 

Schools are conveniently located in every community, with easy and 

known access to the local population that they serve. They also have 

suitable spaces (e.g., gymnasiums or multiuse rooms) in which large 

numbers of people can be accommodated for a few days. Food service 

is often available, as is ample space for assembly, processing, and delivery of goods and equipment. Because schools are public property, the 

costs using the facilities for a few weeks are minimal. Also, particularly 

in California, where schools are subject to the Field Act, schools are well 

constructed and among the most likely of all the community’s buildings 

to survive intact and in a usable condition.

No specific design decisions are necessary for this use, nor is it necessary 

to stockpile emergency supplies. The exact circumstances of the event 

and the number and types of people to be accommodated will determine 

the supplies that are necessary. Experience has shown that local and even 

regional manufacturers and suppliers are very effective in providing services after an event. Following the 1983 Coalinga earthquake, temporary 

shelter was provided in the high school gymnasium. A regional beer canning plant substituted drinking water for beer for a few shifts and rapidly 

delivered the chilled cans to the site.

The school district and the local emergency services agency should 

plan for an earthquake event. This includes determining what spaces 

will be available and how many people can be accommodated, signing a 

pre-contract with a local engineer or architect for immediate post-earthquake inspection to determine safety, examining strategies for continued 

operation in the event some spaces are occupied by refugees, and determining a means for providing food and sanitary supplies. 

Possible use of school buildings as a safe haven for the community in the 

event of chemical, biological, radiological, or explosive attack involves 
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

complex design and construction issues. This use of school property 

is discussed in FEMA 428, Primer to Design Safe School Projects in Case of 

Terrorist Attacks, Chapter 6 (2003b), and FEMA 453, Design Guidance for 

Shelters and Safe Rooms (2006). 

4.8 References and Sources of Additional 

Information

American Society of Civil Engineers (ASCE), 2003. Seismic Evaluation of 

Existing Buildings, ASCE 31-03, Structural Engineering Institute, Reston, 

VA.

ASCE, 2005. Minimum Design Loads for Buildings and Other Structures, 

ASCE 7-05, Structural Engineering Institute, Reston, VA.

ASCE, 2007. Seismic Rehabilitation of Existing Buildings, ASCE 41-07, 

Structural Engineering Institute, Reston, VA.

ASCE, 2010. Minimum Design Loads for Buildings and Other Structures, 

ASCE 7-10, Structural Engineering Institute, Reston, VA.

Applied Technology Council (ATC), 1978. Tentative Provisions for the 

Development of Seismic Regulations for Buildings, ATC-3-06, Washington, 

DC, June 1978.

ATC, 1995. ATC 20, Postearthquake Building Safety Evaluation Procedures, 

Washington, DC. 

Arnold, Chris, and Tony Alexander, 2001. BSSC: Presentations to the 

Architectural Community. 

California Emergency Management Agency, 2003. Guide and Checklist for 

Nonstructural Earthquake Hazards in California Schools. Governor’s Office 

of Emergency Services, Mather, CA, 56 pages.

California Seismic Safety Commission (CSSC), 1995. Northridge 

Earthquake: Turning Loss to Gain, Report No. CSSC 95-01, Sacramento, 

CA.

Federal Emergency Management Agency (FEMA), 1992. NEHRP 

Handbook for the Seismic Evaluation of Existing Buildings, FEMA 178, 

Building Seismic Safety Council, Washington, DC.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 4-57

MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

FEMA, 1994. Reducing the Risks of Nonstructural Earthquake Damage: 

A Practical Guide, FEMA 74, Wiss, Janney, Elstner Associates, Inc., 

Washington, DC.

FEMA, 1997a. NEHRP Commentary on the Guidelines for the Seismic 

Rehabilitation of Buildings, FEMA 274, prepared by the Building Seismic 

Safety Council and the Applied Technology Council for FEMA, 

Washington, DC.

FEMA, 1997b. NEHRP Guidelines for the Seismic Rehabilitation of Buildings,

FEMA 273, Building Seismic Safety Council, Washington, DC. 

FEMA, 1998. Handbook for the Seismic Evaluation of Existing Buildings, 

FEMA 310, Washington, DC. 

FEMA, 2000a. NEHRP Recommended Provisions for Seismic Regulation for 

New Buildings, 2000 Edition, 2 volumes and maps (FEMA 368) and commentary (FEMA 369).

FEMA, 2000b. Prestandard and Commentary for the Seismic Rehabilitation 

of Buildings, FEMA 356, prepared by the American Society of Civil 

Engineers for FEMA, Washington, DC. 

FEMA, 2002a. Handbook for the Seismic Evaluation of Existing Buildings, 

FEMA 310, Washington, DC. 

FEMA, 2002b. Rapid Visual Screening of Buildings for Potential Seismic 

Hazards: A Handbook, Second Edition, FEMA 154, prepared by the 

Applied Technology Council for FEMA, Washington, DC.

FEMA, 2003a. The NEHRP Recommended Provisions for Seismic Regulation 

for New Buildings, 2003 Edition, 2 volumes and maps (FEMA 450) and 

commentary (FEMA 451).

FEMA, 2003b. Primer to Design Safe School Projects in Case of Terrorist Attacks,

FEMA 428, Washington, DC.

FEMA, 2003c. Incremental Seismic Rehabilitation of School Buildings (K12), FEMA 395, Virginia Polytechnic Institute/Building Technology 

Incorporated, Silver Spring, MD/Melvyn Green & Associates, Inc., 

Torrance, CA, Washington, DC.

FEMA, 2006. Design Guidance for Shelters and Safe Rooms, FEMA 453, 

Washington, DC.
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Heinz Center, 2002. Human Links to Coastal Disasters, H. John Heinz III 

Center for Science, Economics, and the Environment, Washington, DC, 

2002.

International Code Council (ICC), 2000. International Building Code 

2000, Country Club Hills, IL.

ICC, 2009. International Building Code 2009, Country Club Hills, IL.

U.S. Geological Survey (USGS), 2010. Earthquake Hazards Program 

Web site, http://earthquake.usgs.gov/.

4.9 Glossary of Earthquake Terms

Acceleration. Rate of change of velocity with time.

Amplification. A relative increase in ground motion between one type 

of soil and another or an increase in building response as a result of 

resonance. 

Amplitude. Maximum deviation from mean of the center line of a wave.

Architectural Components. Components such as exterior cladding, ceilings, partitions, and finishes.

Building. Any structure that could be used for the shelter of human 

occupants.

Component (also Element). Part of an architectural, structural, electrical, 

or mechanical system.

Configuration. The size, shape, and geometrical proportions of a building.

Connection. A means by which different materials or components are 

joined to each other.

Damage. Any physical destruction caused by earthquakes.

Deflection. The state of being turned aside from a straight line, generally 

used in the horizontal sense; see also “Drift.”

Design Earthquake. In the International Building Code (IBC), the earthquake that produces ground motions at a site that are two/thirds those 

of the “Maximum Considered Earthquake.”
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MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Design Ground Motion. See “Design Earthquake.”

Diaphragm. A horizontal or nearly horizontal structural element designed to transmit lateral forces to the vertical elements of the seismic 

force resisting system.

Drift. Vertical deflection of a building or structure caused by lateral forces; see also “Story Drift.”

Ductility. Property of some materials, such as steel, to distort when subjected to forces while still retaining considerable strength.

Earthquake. A sudden motion or vibration in the earth caused by the 

abrupt release of energy in the earth’s lithosphere. 

Effective Peak Acceleration and Effective Peak Velocity Related Acceleration. Coefficients shown on maps in the IBC for determining prescribed 

seismic forces.

Elastic. Capable of recovering size and shape after deformation.

Epicenter. A point on the earth’s surface that is directly above the focus 

of an earthquake.

Exceedance Probability. The probability that a specified level of ground 

motion or specified social or economic consequences of earthquakes will 

be exceeded at a site or in a region during a specified exposure time.

Exposure. The potential economic loss to all or certain subsets of the 

built environment as a result of one or more earthquakes in an area; this 

term usually refers to the insured value of structures carried by one or 

more insurers.

Fault. A fracture in the earth’s crust accompanied by displacement of 

one side of the fracture with respect to the other in a direction parallel 

to the fracture.

Focus. The location of a fault break where an earthquake originates; also 

termed “Hypocenter.” 

Force. Agency or influence that tries to deform an object or overcome its 

resistance to motion.

Frame, Braced. Diagonal members connecting components of a structural frame to resist lateral forces.
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

Frame, Space. A structural system composed of interconnected members, 

other than bearing walls, that is capable of supporting vertical loads and 

that also may provide resistance to seismic forces.

Frame System, Building. A structural system with an essentially complete 

space frame providing support for vertical loads; seismic forces are resisted by shear walls or braced frames. 

Frame System, Moment. A frame in which members and joints are capable of resisting lateral forces by flexure as well as along the axis of 

the members; varying levels of resistance are provided by ordinary, intermediate, and special moment frames as defined in the IBC with special 

frames providing the most resistance.

“g”. The acceleration due to gravity or 32 feet per second.

Ground Failure. Physical changes to the ground surface produced by an 

earthquake, such as lateral spreading, landslides, or liquefaction. 

Hypocenter. See “Focus.”

Intensity. The apparent effect that an earthquake produces at a given 

location; in the United States, intensity generally is measured by the 

modified Mercalli intensity scale.

Irregular. Deviation of a building configuration from a simple symmetrical shape.

Joint. Location of connections between structural or nonstructural members and components.

Liquefaction. The conversion of a solid into a liquid by heat, pressure, or 

violent motion; sometimes occurs to the ground in earthquakes.

Loss. Any adverse economic or social consequences caused by 

earthquakes.

Mass. A constant quantity or aggregate of matter; the inertia or sluggishness that an object, when frictionlessly mounted, exhibits in response to 

any effort made to start it or stop it or to change in any way its state of 

motion.

Maximum Considered Earthquake Ground Motion. The most severe 

earthquake effects considered in the IBC. These are represented by 

the mapped spectral response accelerations at short and long periods, 
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 4-61

MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

obtained from maps in the IBC, adjusted for Site Class effects using site 

coefficients.

Mercalli Scale (or Index). A measure of earthquake intensity named after 

Giuseppe Mercalli, an Italian priest and geologist.

Nonbuilding Structure. A structure, other than a building, designed and 

constructed in a manner similar to buildings and having a basic lateral 

and vertical seismic-force-resisting system conforming to a type included 

in Chapter 14 of the IBC.

Occupancy Importance Factor. A factor, between 1.0–1.5, assigned to each 

structure according to its Seismic Occupancy Category.

Partition. See “Wall, Nonbearing.”

Period. The elapsed time (generally in seconds) of a single cycle of a 

vibratory motion or oscillation; the inverse of frequency.

P-Wave. The primary or fastest waves traveling away from a fault rupture 

through the earth’s crust and consisting of a series of compressions and 

dilations of the ground material.

Quality Assurance Plan. A detailed written procedure that establishes the 

systems and components subject to special inspection and testing.

Recurrence Interval. See “Return Period.”

Resonance. The amplification of a vibratory motion occurring when the 

period of an impulse or periodic stimulus coincides with the period of 

the oscillating body.

Return Period. The time period in years in which the probability is 63 

percent that an earthquake of a certain magnitude will recur.

Richter Magnitude (or Scale). A logarithmic scale expressing the magnitude of a seismic (earthquake) disturbance in terms of the maximum 

amplitude of the seismic waves at a standard distance from their focus; 

named after its creator, the American seismologist Charles R. Richter.

Rigidity. Relative stiffness of a structure or element; in numerical terms, 

equal to the reciprocal of displacement caused by unit force.

Seismic. Of, subject to, or caused by an earthquake or an earth vibration.
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4 MAKING SCHOOLS SAFE FROM EARTHQUAKES

Seismic Event. The abrupt release of energy in the earth’s lithosphere 

causing an earth vibration; an earthquake.

Seismic Force Resisting System. The part of the structural system that is 

designed to provide required resistance to prescribed seismic forces. 

Seismic Forces. The actual forces created by earthquake motion; assumed forces prescribed in the IBC that are used in the seismic design of 

a building and its components. 

Seismic Hazard. Any physical phenomenon such as ground shaking or 

ground failure associated with an earthquake that may produce adverse 

effects on the built environment and human activities; also the probability of earthquakes of defined magnitude or intensity affecting a given 

location.

Seismic Occupancy Category. A classification assigned to a structure based 

on its occupancy and use as defined in the IBC.

Seismic Risk. The probability that the social or economic consequences 

of an earthquake will equal or exceed specified values at a site during a 

specified exposure time; in general, seismic risk is vulnerability multiplied by the seismic hazard.

Seismic Waves. See “Waves, Seismic.”

Seismic Zone. Generally, areas defined on a map within which seismic 

design requirements are constant; in the IBC, seismic zones are defined 

both by contour lines and county boundaries.

Shear. A force that acts by attempting to cause the fibers or planes of an 

object to slide over one another.

Shear Wall. See “Wall, Shear.”

Speed. Rate of change of distance traveled with time irrespective of 

direction.

Stiffness. Resistance to deflection or drift of a structural component or 

system.

Story Drift. Vertical deflection of a single story of a building caused by 

lateral forces.

Strain. Deformation of a material per unit of the original dimension.
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 4-63

MAKING SCHOOLS SAFE FROM EARTHQUAKES 4 

Strength. The capability of a material or structural member to resist or 

withstand applied forces.

Stress. Applied load per unit area or internal resistance within a material 

that opposes a force’s attempts to deform it.

S-Wave. Shear or secondary wave produced essentially by the shearing or 

tearing motions of earthquakes at right angles to the direction of wave 

propagation.

System. An assembly of components or elements, such as a structural 

system, designed to perform a specific function.

Torsion. The twisting of a structural member about its longitudinal axis. 

Velocity. Rate of change of distance traveled with time in a given direction; in earthquakes, it usually refers to seismic waves and is expressed in 

inches or centimeters per second.

Vulnerability. The degree of loss to a given element at risk, or set of such 

elements, resulting from an earthquake of a given intensity or magnitude; 

expressed in a scale ranging from no damage to total loss; a measure of 

the probability of damage to a structure or a number of structures.

Wall, Bearing. An interior or exterior wall providing support for vertical 

loads.

Wall, Nonbearing. An interior or exterior wall that does not provide support for vertical loads other than its own weight as permitted by the 

building code; see also “Partition.”

Wall, Shear. A wall, bearing or nonbearing, designed to resist lateral forces parallel to the plane of the wall. 

Wall System, Bearing. A structural system with bearing walls providing 

support for all or major portions of the vertical loads; seismic resistance 

may be provided by shear walls or braced frames.

Waves, Seismic. Vibrations in the form of waves created in the earth by 

an earthquake.

Weight. Name given to the mutual gravitational force between the earth 

and an object under consideration; varies depending on location of the 

object at the surface of the earth.

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-1

Making Schools Safe 5From Flooding

5.1 General Design Considerations

T his chapter introduces the physical nature and mechanics of floods 

and explains how flood probabilities are determined and how 

flood hazard areas are identified. It describes the types of flood 

damage that can result when schools are located in flood hazard areas 

and are affected by flooding. A series of requirements and best practices are introduced that school districts, facility planners, and designers 

should consider for reducing the risks from flooding to new schools and 

to existing school campuses that are located in floodprone areas.

This chapter demonstrates why avoidance of flood hazard areas is the 

most effective way to minimize the life-safety risk to students, staff, and 

the citizens who rely on these facilities, as well as to minimize the potential for damage to buildings and other elements of schools and 

campuses. When an existing school building is exposed to flooding, or 

a new school building is proposed to be located in a flood hazard area, 

steps should be taken to minimize the risks. A well-planned, designed, 
5-2 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

5 MAKING SCHOOLS SAFE FROM FLOODING

constructed, and maintained school should be able 

to withstand damage and remain functional after a 

flooding event, even one of low probability. ASCE 

24, Flood Resistant Design and Construction, provides 

“minimum requirements for flood-resistant design 

and construction of structures” (2005). Design professionals should be familiar with this standard and 

exercise an appropriate level of care in any construction of school buildings in flood hazard areas.

5.1.1 The Nature of Flooding

Flooding is the most common natural hazard in 

the United States, affecting more than 21,000 local 

jurisdictions and representing more than 70 percent of Presidential disaster declarations. Several studies have estimated 

that 7 to 10 percent of the Nation’s land area is subject to flooding. 

Some communities have very little flood risk; others lie entirely within 

the floodplain.

Flooding is a natural process that may occur in a variety of forms: longduration flooding along rivers that drain large watersheds; flash floods 

that send a devastating wall of water down a mountain canyon; and coastal flooding that accompanies high tides and onshore winds, hurricanes, 

and nor’easters. When this natural process does not affect human activity, flooding is not a problem. In fact, many species of plants and animals 

that live adjacent to bodies of water are adapted to a regimen of periodic 

flooding. 

Flooding is only a problem when human development is located in areas 

prone to flooding. Such development exposes people to potentially lifethreatening situations and makes property vulnerable to serious damage 

or destruction. It also can disrupt the natural surface flow, redirecting 

water onto lands not normally subject to flooding. 

Flooding along waterways normally occurs as a result of excessive rainfall or snowmelt that exceeds the capacity of channels. Flooding along 

shorelines is usually a result of coastal storms that generate storm surges 

or waves above normal tidal fluctuations. Factors that can affect the frequency and severity of flooding and the resulting damage include:

n Channel obstructions caused by fallen trees, accumulated debris, 

and ice jams

n Channel obstructions caused by road and rail crossings where the 

bridge or culvert openings are insufficient to convey floodwaters

When new schools are being planned and 

constructed, and a site with a flood hazard 

must be used, it is important that:

n the school be placed on the portion of 

the site that is least vulnerable to the 

identified flood hazard

n the highest level of care be used for the 

design and construction of the school 

(i.e., the most stringent application of 

ASCE7, ASCE 24, and the local floodplain ordinance)
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-3

n Erosion of shorelines and stream banks, often 

with episodic collapse of large areas of land

n Deposition of sediment that settles out of floodwaters or is carried inland by wave action

n Increased upland development of impervious 

surfaces and manmade drainage improvements that increase rainfall-runoff volumes

n Land subsidence, which increases flood depths

n Failure of dams (resulting from seismic activity, lack of maintenance, flows that exceed the 

design, or destructive acts), which may suddenly and unexpectedly release large volumes of 

water

n Failure of levees (associated with flows that exceed the design, weakening by seismic activity, 

lack of maintenance, or destructive acts), which 

may result in sudden flooding of areas behind 

levees

n Failure of seawalls, revetments, bulkheads, or 

similar coastal structures, which can lead to 

rapid erosion and increased flooding and wave 

damage during storms

Each type of flooding has characteristics that represent important aspects of the hazard. These 

characteristics should be considered in the selection of school sites, the design of new school 

buildings and athletic facilities, and the expansion 

or rehabilitation of existing floodprone schools.

Riverine flooding results from the accumulation 

of runoff from rainfall or snowmelt, such that the 

volume of water exceeds the capacity of waterway 

channels and spreads out over the adjacent land. 

Riverine flooding flows downstream under the force 

of gravity. Its depth, duration, and velocity are functions of many factors, including watershed size and 

slope, degree of upstream development, soil types 

and nature of vegetation, topography, and characteristics of storms (or depth of snowpack and rate 

of melting). Figure 5-1 illustrates a cross-section of a 

generic riverine floodplain.

Four Examples of Schools Vulnerable to 

Flood Hazards

1. Two schools in Gurnee, IL, were damaged 

by floods in 1986. The school district’s 

actual costs were over $1.6 million to repair 

and replace the facilities, supplies, and 

materials. Not included in this figure are 

the costs for transportation and rental, and 

disruption of the school year for children 

who, for several months, attended school 

in a vacant department store 4 miles away. 

For an additional 2 years of renovation 

and reconstruction, the children attended 

school in another community 8 miles away. 

One school was later rebuilt as a floodprotected facility for a cost of $17 million, 

all of which was paid by local taxpayers. 

2. In April 2003, a dry floodproofed private 

school in Jackson, MS, was soaked when 

a sudden downpour dumped 9 inches 

of rain on the area. Because the event 

occurred in the pre-dawn hours when no 

one was on site to install the floodproofing measures (e.g., water-tight doors and 

special seals), water entered the building, 

causing damage to carpets, walls, furniture, and equipment.

3. In 1989, Hurricane Hugo vividly revealed 

the importance of knowing whether 

schools are prone to flooding. The local 

emergency manager’s records identified 

the McClellanville, SC, school as an approved hurricane shelter. Unfortunately, 

that designation was based on the erroneous information about the elevation 

of the building. When storm surge flooding 

inundated the school, people had to break 

through the ceiling and lift everyone up to 

the attic. 

4. Flooding in the spring of 2001 tested flood 

protection for the Oak Grove Lutheran 

High School in Fargo, ND (see Figure 

5-29). Prompted by the failure of temporary 

earth and sandbag dikes during the 1997 

Red River flood of record, which resulted in 

over $3.5 million in damage to the school, 

the city designed and constructed a brickfaced permanent floodwall. Five access 

points, wide enough for vehicles, were protected with an “invisible” closure that is an 

integral part of the floodwall. A crew of six 

installed the closures in less than 2 hours.
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5 MAKING SCHOOLS SAFE FROM FLOODING

Flood

Level

Normal Water 

Level

Stream

Channel

Floodway

Fringe Fringe

(100-Year Floodplain)

Flood Hazard Area

Coastal flooding is experienced along the Atlantic, Gulf, and Pacific 

coasts, and the Great Lakes. Coastal flooding is influenced by storm 

surges associated with tropical cyclonic weather systems (hurricanes, 

tropical storms, tropical depressions, typhoons), extratropical systems 

(nor’easters and other large low-pressure systems), seiches and tsunamis 

(surges induced by seismic activity). Coastal flooding is characterized by 

wind-driven waves that also may affect areas along the Great Lakes shorelines; winds blowing across the broad expanses of water generate waves 

that can rival those experienced along ocean shorelines. Some Great 

Lakes shorelines experience coastal erosion, in part because the erosion 

is associated with fluctuations in water levels. Figure 5-2 is a schematic of 

a generic coastal floodplain.

5.1.2 Probability of Occurrence or Frequency

The probability of occurrence, or frequency, is a statement of the likelihood that an event of a certain magnitude will occur in a given period 

of time. For many decades, floodplain management has been based on 

the flood that has a 1-percent chance of occurring in any given year, 

commonly called the “100-year flood.” For certain critical actions, such 

as planning or constructing schools and evacuation shelters, the basis of 

risk decisions should be the flood that has a 0.2-percent probability of 

occurring in any given year, commonly called the “500-year flood.” In 

most locations, the benefits of added protection to the 500-year level are 

greater than the added costs.

Figure 5-1:

The riverine floodplain
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-5

V Zone Coastal A Zone A Zone X Zone

Flood Level Including

Wave Effects

Stillwater Depth

Between 4 and 2 ft

100-Year 

Stillwater Elevation

Sea Level

Shoreline Sand Beach Overland Wind Fetch Limit of Flooding

and Waves

Wave Height or Wave Runup Depth ≥ 3 ft Wave Height 3.0 –1.5 ft Wave Height <1.5 ft

V Zone Coastal A Zone A Zone X Zone

and Waves

V Zone Coastal A Zone A Zone X Zone

The term “100-year flood” is often misunderstood because it conveys the 

impression that a flood of that magnitude will occur only once every 100 

years. Actually, the 1-percent-annual-chance flood has one chance in 100 

of occurring in any given year. The fact that a 1-percent-annual-chance 

flood is experienced at a specific location does not alter the probability 

that a flood of the same or greater magnitude could occur at the same 

location in the next year, or even multiple times in a single year. As the 

length of time considered increases, so does the probability that a flood 

of a specific magnitude or greater will occur. For example, Figure 5-3 illustrates that the probability a 100-year flood will occur is 26 percent during 

a 30-year period. And during a 70-year period (the potential useful life of 

many buildings), the probability increases to 50 percent. Similarly, a 500-

year flood has a 0.2-percent probability of being equaled or exceeded in 

any given year, a 6-percent probability of occurrence during a 30-year period, and an 18-percent probability of occurrence during a 70-year period. 

The assigned frequency of a flood (e.g., 100-year) is independent of 

the number of years between actual occurrences. Hurricane Camille 

hit the Mississippi coast in 1969 with storm surge flooding that far 

exceeded previous events, and Hurricane Katrina affected much the 

* Defined in Section 5.1.5.2 ** Defined in Section 5.1.5.3

Figure 5-2: The floodplain along an open coast

* ** * *
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5 MAKING SCHOOLS SAFE FROM FLOODING

same area in 2005. Although just 36 years apart, both storms produced 

flood levels that were significantly higher than the predicted 100-year 

flood. Similarly, the Mississippi River flooded large areas in Missouri in 

1993 with flooding that exceeded the predicted 100-year flood levels. 

Just 2 years later, many of the same areas were flooded again. 

Regardless of the flood selected for design purposes (the “design 

flood”), the designer must determine specific characteristics associated with that flood. Determining a flood with a specific probability of 

occurrence is done in a multi-step process that typically involves using computer models available in the public domain. If a sufficiently 

long record of flood information exists, the design flood may be determined by applying statistical tools to the data. 

Alternatively, water resource engineers sometimes 

apply computer models to simulate different rainfall events over watersheds to predict how much 

water will run off and accumulate in channels. 

Other computer models are used to characterize 

the flow of water down the watershed and predict 

how high the floodwaters will rise. 

The term “100-year flood” is often misunderstood because it conveys the impression 

that a flood of that magnitude will occur only 

once every 100 years. Actually, it has one 

chance in 100 of occurring in any given year.

Figure 5-3:

Probability and 

magnitude 

SOURCE: U.S. GEOLOGICAL 

SURVEY, GUIDELINES FOR 

DETERMINING FLOOD FLOW 

FREQUENCY, BULLETIN 17B 

(APPENDIX D).

Flood Magnitude

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

10-

Year

96%

71%

45%

26%

6%

25-

Year

50-

Year

100-

Year

500-

Year

Percent Chance of One or More Floods 

of a Given Magnitude Being Equalled or 

Exceeded in a 30-year Period
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Flood frequency analyses are performed using historical records, and 

the results are influenced by the length of the record. Such analyses 

do not account for recent changes to the land (upland development or 

subsidence) or future changes (additional development, greater subsidence, or climatic variations).

For coastal areas, both historical storms and simulated storm surge 

models can be used to predict the probability that floodwaters will 

rise to a certain level and be accompanied by waves of certain heights. 

Many coastal storms will produce storm surge flooding that, depending on local topography, may extend inland significantly farther than 

anticipated for a 1-percent-annual-chance flood. Other factors that 

influence the severity of hurricane storm surges include the forward 

speed of the storm, when during the tide cycle the storm comes onshore, and the near-shore bathymetry. Statistically, extreme storm 

surges occur less frequently than the 1-percent- or 0.2-percent-annualchance floods, but their consequences can be catastrophic.

School facility planners and designers should research the relationship 

between flood levels for different frequency events, including extreme 

events, especially in hurricane-prone communities. The difference in 

flood levels may be extreme in some situations, depending on local conditions and the source of flooding. In other areas flood levels of lower 

probability floods might not be much higher than a 1-percent-annualchance flood.

The National Flood Insurance Program (NFIP) is a Federal program that 

encourages communities to regulate flood hazard areas and, in return, 

offers property owners insurance protection against losses from flooding 

(see Sections 5.1.6.1 and 5.1.6.2). The NFIP uses the 1-percent-annualchance flood as the basis for flood hazard maps, for setting insurance 

rates, and for application of regulations in order to minimize future 

flood damage. 

The commentary of ASCE 24 provides additional information on addressing flood risk through the use of flood events other than the 

1-precent-annual-chance flood, including local 

“flood of record” events. Nearly every year, a very 

low probability flood occurs somewhere in the 

United States, often with catastrophic consequences. Therefore, use of a lower probability flood (at 

least the 0.2-percent-annual-chance, or 500-year) 

for design purposes is strongly recommended 

(and may be required by some States and local 

jurisdictions). 

ASCE 24 sets forth that a higher level of 

protection is required for critical facilities, 

essential facilities, and schools. This 

higher level of protection considers additional freeboard and designing for a 

lower probability flood event (e.g., the 

0.2-precent-annual-chance flood).”
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5 MAKING SCHOOLS SAFE FROM FLOODING

As noted in Section 5.1.6.3, the 500-year level of protection is required 

if Federal funds are involved in constructing critical facilities that are 

vital for emergency response and rapid recovery. This reinforces the 

importance of protecting both the functionality and financial investment in a school by applying stricter standards than those required for 

other buildings. Students and the community experience significant 

and long-term impacts if a damaged school is closed for an extended 

period of time. 

5.1.3 Flood Characteristics and Loads

A number of factors associated with riverine and coastal flooding are 

important in the selection of sites for schools, in site design, and in the 

determination of flood loads required as part of architectural and engineering design. 

Depth: The most apparent characteristic of any flood is the depth of the 

water. Depending on many factors, such as the shape of a river valley or 

the presence of obstructing bridges, riverine flooding may rise just a few 

feet or tens of feet above normal levels. The depth of coastal flooding is 

influenced by such factors as the tidal cycle, the duration of the storm, 

the elevation of the land, offshore bathymetry, and the presence of waves. 

Depth is a critical factor in building design because the hydrostatic forces on a vertical surface (such as a foundation wall) are directly related 

to depth, and because costs associated with protecting buildings from 

flooding increase with depth. Under certain conditions, hurricanes can 

produce storm surge flooding that is 20 to 30 feet above mean sea level 

or, in extreme cases along the Gulf Coast, 35 feet or higher above mean 

sea level.

Duration: Duration is the measure of how long the water remains above 

normal levels. The duration of riverine flooding is primarily a function 

of watershed size and the longitudinal slope of the valley (which influences how fast water drains away). Small watersheds are more likely to be 

“flashy,” a characteristic that refers to the rapidity with which floodwaters 

rise and fall. Areas adjacent to large rivers may be flooded for weeks or 

months. Most coastal flooding is influenced by the normal tidal cycle, as 

well as how fast coastal storms move through the region. Areas subject to 

coastal flooding can experience long periods of flooding where drainage 

is poor or slow as a result of topography or the presence of flood control 

structures. For example, water may be trapped in depressions in the land 

or behind a floodwall or levee with inadequate drainage. More commonly, coastal flooding is of shorter duration, on the order of 12 to 24 hours, 

especially if storms move rapidly. Flooding of large lakes, including those 

behind dams, can be of very long duration because the large volume of 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-9

water takes longer to drain. For building design, duration is important 

because it affects access, building usability, and saturation and stability of 

soils and building materials. Information about flood duration is sometimes available as part of a flood study or can be developed by a qualified 

engineer.

Local drainage problems create ponding and local flooding that is often not directly associated with a body of water such as a creek or river. 

Although such flooding is relatively shallow and not characterized by 

high velocity flows, considerable damage may result. Areas with poor 

drainage frequently experience repetitive damage. Some local drainage problems are exacerbated by old or undersized drainage system 

infrastructure. Flooding caused by drainage problems typically occurs 

as sheetflow or along waterways with small drainage areas. This type of 

flooding is generally not mapped or regulated.

Velocity: The velocity of floodwaters ranges from extremely high (associated with flash floods or storm surge) to very low or nearly stagnant 

(in backwater areas and expansive floodplains). Velocity is important in 

site planning because of the potential for erosion. In structural design, 

velocity is a factor in determining the hydrodynamic loads and impact 

loads. Even shallow, high-velocity water can threaten the lives of pedestrians and motorists. Accurate estimates of velocities are difficult to make, 

although information about mean velocities may be found in some 

floodplain studies.

Wave action: Waves contribute to erosion and scour, and also contribute 

significantly to design loads on buildings. The magnitude of wave forces 

can be 10 to more than 100 times greater than wind and other design 

loads, and thus may control many design parameters. The magnitude of 

wave forces can be 10 to more than 100 times greater than wind and other 

design loads, and thus may control many design parameters. Waves must 

be accounted for in site planning along coastal shorelines, in flood hazard 

areas that are inland of open coasts, and other areas where waves occur, 

including areas with sufficient fetch that winds can generate waves (such 

as lakes and expansive riverine floodplains). Waves on top of storm surges 

may be as much as 50 percent higher than the stillwater depth (flood 

depth without waves) of the surge. 

Impacts from debris and ice: Floating debris and ice contribute to the 

loads that must be accounted for in structural design. The methods and 

models used to predict and delineate flood hazard areas do not specifically incorporate the effects of debris. Thus, there are few sources to 

determine the potential effects of debris impact loads, other than past 

observations and judgment. 
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5 MAKING SCHOOLS SAFE FROM FLOODING

Erosion and scour: In coastal areas, erosion refers to the lowering of the 

ground surface as a result of a flood event, or the gradual recession of a 

shoreline as a result of long-term coastal processes. Along riverine waterways, erosion refers to undermining of channel banks, lateral movement 

of the channel, or cutting of new channels. Scour refers to a localized 

lowering of the ground surface due to the interaction of currents and/or 

waves with structural elements, such as pilings. Soil characteristics influence an area’s susceptibility to scour. Erosion and scour may affect the 

stability of foundations and earthen-filled areas, and may cause extensive 

site damage. 

5.1.3.1 Hydrostatic Loads

Hydrostatic loads occur when water comes into contact with a building 

or building component, both above and below the ground level. They 

act as lateral pressure or vertical pressure (buoyancy). Hydrostatic loads 

on inclined or irregular surfaces may be resolved into lateral and vertical 

loads based on the surface geometry and the distribution of hydrostatic 

pressure. 

Lateral hydrostatic loads are a direct function of water depth (see Figure 

5-4). These loads can cause severe deflection or displacement of buildings or building components if there is a substantial difference in water 

levels on opposite sides of the component (or inside and outside of the 

building). Hydrostatic loads are balanced on foundation elements of 

elevated buildings, such as piers and columns, because the element is 

surrounded by water. If not oriented parallel to the flow of water, shearwalls may experience hydrostatic loads due to a difference of water depth 

on either side of the wall. To reduce excessive pressure from standing 

water, floodplain management requirements in flood zones known as “A 

zones” call for openings in walls that enclose areas below the flood elevation (see description of continuous perimeter wall foundation in Section 

5.3.4 and description of flood zones in Section 5.1.5.2).

Buoyancy force resulting from the displacement of water is also of concern, especially for dry floodproofed buildings and aboveground and 

underground tanks. Buoyancy force is resisted by the dead load of the 

building or the weight of the tank. When determining buoyancy force, 

the weight of occupants or other live loads (such as the contents of a 

tank) should not be considered. If the building or tank does not weigh 

enough when empty, then additional stabilizing measures need to be 

taken to avoid flotation. This becomes a significant consideration for designs intended to dry floodproof a building (described in Section 5.3.5). 

Buoyancy force is slightly larger in saltwater, because saltwater weighs 

slightly more than fresh water.
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DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-11

5.1.3.2 Hydrodynamic Loads

Water flowing around a building or a foundation structural element below the flood level imposes hydrodynamic loads. The loads, which are a 

function of flow velocity and structure geometry, include frontal impact 

on the upstream face, drag along the sides, and suction on the downstream side (see Figure 5-5). Breaking waves also impart hydrodynamic 

loads. Ways to determine or estimate flood velocities are described in 

Section 5.1.4.3 (riverine) and Section 5.1.4.4 (coastal). 

Figure 5-4: Hydrostatic loads on buildings

Figure 5-5: Hydrodynamic loads on a building or building element

Drag Effect on Sides

Frontal Impact on

Upstream Side

Negative Pressure/Suction on Downstream Side

Building or

Building Element

Depth of Water

Drag Effect on Sides

Frontal Impact on

Upstream Side FLOW
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5 MAKING SCHOOLS SAFE FROM FLOODING

The most common computation methods for hydrodynamic loads are 

outlined in the design standard ASCE 7, produced by the American 

Society of Civil Engineers’ Structural Engineers Institute (ASCE/SEI). 

These methods assume that the flood velocity is constant (i.e., steady 

state flow) and the hydrodynamic loads are then determined according 

to the principles of fluid mechanics or hydraulic models. For practical 

applications, hydrodynamic loads become important when flow reaches 

moderate velocities of 5 feet per second. Drag coefficients for common 

building elements, such as columns and piers, can be found in a number 

of sources and ASCE 7 recommends values for a variety of conditions. 

Wave loads are another important component of hydrodynamic loads. 

As described in ASCE 7, “design and construction of buildings and other structures subject to wave loads shall account for the following loads: 

waves breaking on any portion of the building or structure; uplift forces 

caused by shoaling waves beneath a building or structure, or portion 

thereof; wave runup striking any portion of the building or structure; 

wave-induced drag and inertia forces; and wave-induced scour at the 

base of a building or structure, or its foundation.” 

Wave forces striking buildings and building elements can range from 10 

to more than 100 times wind or other forces. Forces of this magnitude 

can be substantial, even when acting over the relatively small surface area 

of the supporting structure of elevated buildings. Post-storm damage 

inspections show that breaking wave loads overwhelm virtually all woodframe and unreinforced masonry walls below the wave crest elevation. 

Only engineered or massive structural elements are capable of consistently withstanding breaking wave loads. 

The magnitude of wave forces provides the rationale for the floodplain 

management requirement that the bottom of the lowest horizontal 

structural member be at or above the design flood elevation (DFE) in 

environments where high-velocity wave action from storms or seismic 

sources is possible (called “V zones,” also referred to as Coastal High 

Hazard Areas). In V zones, breaking wave heights or wave runup depths 

are predicted to be 3 feet or higher. Because breaking waves as small as 

1.5 feet in height can impose considerable loads, there is a growing awareness of the value of accounting for waves in areas immediately landward of 

V zones, which are referred to as “Coastal A Zones” (see Section 5.1.5.3). 

Of the variety of wave forces described in ASCE 7—breaking waves, 

uplift, wave runup, wave-induced drag and inertia, and scour—breaking waves constitute the greatest hazard. Designers should therefore 

use breaking wave forces as the basis of the design load. Computation 

of breaking wave loads depends on the determination of wave height. 
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DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-13

For more information on estimating wave heights, see Section 5.1.4.1. 

Designers should refer to ASCE 7 for detailed discussion and computation procedures for determining breaking wave loads.

Breaking wave loads on vertical walls or supporting structural members 

reach a maximum when the direction of wave approach is perpendicular 

to the wall. It is common to assume that the direction of approach will be 

perpendicular to the shoreline, in which case the orientation of the wall 

to the shoreline will influence the direction of approach used in load 

calculations. ASCE 7 provides a method to reduce breaking wave loads 

on vertical walls when waves are expected to approach a building from a 

direction other than straight on. 

Breaking wave forces are much higher than typical wind pressures, even 

wind pressures that occur during a hurricane or typhoon. However, the 

duration of individual loads is brief, with peak pressures probably occurring within 0.1 to 0.3 seconds after the wave breaks. Structures are 

to be designed for repetitive impact loads that occur over the duration 

of a storm. Some storms may last just a few hours, as hurricanes move 

through the area, or several days, as during some winter coastal storms 

(nor’easters) that affect the Mid-Atlantic and northeastern States. 

5.1.3.3 Debris Impact Loads

Debris impact loads on a building or building element are caused by objects carried by moving water. Objects commonly carried by floodwaters 

include trees, trash containers, outdoor furniture, storage sheds, dislodged tanks, and remnants of manmade structures such as docks and 

buildings. Extreme impact loads result from less common sources, such 

as shipping containers, boats, and barges. The magnitude of these loads 

is very difficult to predict, yet some reasonable allowance for the possibility of debris impacts should be made during the design process. 

Impact loads are influenced by the location of the building in the potential debris stream. The potential for debris impacts is significant if a 

building is located immediately adjacent to, or downstream from, other 

buildings, among closely spaced buildings, or downstream of large floatable objects. While these conditions may be observable in coastal areas, 

estimating the potential for debris is more difficult in riverine flood hazard areas. Any riverine waterway, whether a large river or smaller urban 

stream, can carry large quantities of debris, especially uprooted trees 

and trash. 

The basic equation for estimating the magnitude of impact loads depends on the values of several variables, which must be determined by 

the designer. These variables include several coefficients, building or 
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5 MAKING SCHOOLS SAFE FROM FLOODING

building element stiffness, debris weight, debris velocity, and duration of 

impact. The latter three variables, described in more detail in ASCE 7, 

are briefly described below.

Debris weight:  Debris weight is one of the more difficult variables to 

estimate. Unless otherwise indicated by field conditions, ASCE 7 recommends using an average object weight of 1,000 pounds. This weight 

corresponds to a 30-foot long log that is 1 foot in diameter, which is 

relatively small compared to large trees that may be uprooted during a 

flood. In coastal areas, expected debris weights depend on the nature of 

the debris. In the Pacific Northwest, large trees and logs are common, 

with weights in excess of 4,000 pounds. In areas where piers and pilings 

are likely to become debris, 1,000 pounds is reasonable. In areas where 

most debris is likely to result from building damage (failed decks, steps, 

failed walls, propane tanks), the average debris weight may be less than 

500 pounds.

Debris velocity: The velocity of the debris when it strikes a building depends on the nature of the debris and the velocity of floodwaters. For 

the impact load computation, the velocity of the waterborne object is 

assumed to be the same as the flood velocity. Although this assumption 

is reasonable for smaller objects, it is considered conservative for large 

objects.

Debris impact duration: Duration of impact is the elapsed time during 

which the impact load acts on the building or building element. The 

duration of impact is influenced primarily by the natural frequency1

 of 

the building or element, which is a function of the building’s stiffness. 

Stiffness is determined by the properties of the material, the number 

of supporting members (columns or piles), the height of the building 

above the ground, and the height at which the element is struck. Despite all the variables that may influence duration of impact, an early 

approach suggested assuming a 1-second duration. A review of results 

from several laboratory tests that measured impacts yielded much briefer 

periods, and ASCE 7 currently recommends the duration of 0.03 second. 

5.1.3.4 Erosion and Local Scour

Strictly speaking, erosion and scour are not loads; however, they must be 

considered during site evaluation and load calculations because they increase the local flood depth, which in turn influences load calculations. 

Erosion may occur in riverine and coastal flood hazard areas. In coastal 

areas, storms can erode or completely remove sand dunes, which act as 

1 Natural frequency is the frequency at which an object will vibrate freely when set in motion.
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barriers to flooding and damaging waves. Erosion may also lower the 

ground surface or cause a short-term or long-term recession of the shoreline. In areas subject to gradual erosion of the ground surface, additional 

foundation embedment depth can mitigate the effects. However, where 

waterways are prone to changing channels and where shoreline erosion 

is significant, engineered solutions are unlikely to be effective. Avoidance 

of sites in areas subject to active erosion is usually the safest and most 

cost-effective course of action.

Local scour results from turbulence at the ground level around foundation elements. Scour occurs in both riverine and coastal flood hazard 

areas, especially in areas with erodible soils. Determining potential scour 

is critical in the design of foundations, to ensure that the bearing capacity or anchoring resistance of the soil around posts, piles, piers, columns, 

footings, or walls is not compromised. Scour determinations require 

knowledge of the flood depth, velocity, waves, soil characteristics, and 

foundation type. 

At some locations, soil at or below the ground surface can be resistant 

to local scour, and calculated scour depths based on unconsolidated surface soils below will be excessive. If the designer believes the underlying 

soil at a site may be scour-resistant, a geotechnical engineer or geologist 

should be consulted. 

5.1.4 Design Parameters

Flood hazards and characteristics of flooding must be identified to 

evaluate the impact of site development and to determine the design 

parameters necessary to calculate flood loads, to design floodproofing 

measures, and to identify and prioritize retrofit measures for existing 

schools. Table 5-3 in Section 5.6 outlines a series of questions to facilitate 

this objective.

5.1.4.1 Flood Depth

Flood depth is the most important factor required to compute flood 

loads because almost every other flood load calculation depends directly or indirectly on this factor. The first step in determining flood depth 

at a specific site is to identify the flood that is specified by the building 

code or floodplain management regulations enforced by the governing 

authority. The most common flood used for design is the “base flood” 

(see Section 5.1.4.2). ASCE 24 provides clear direction on identifying 

the regulatory flood. Local regulations and requirements should be 

compared to ASCE 24 and the most restrictive condition should be followed. The second step is to determine the expected elevation of the 

ground at the site. This expected ground elevation must account for any 
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5 MAKING SCHOOLS SAFE FROM FLOODING

erosion, scour, subsidence, or other ground eroding condition that 

occurs over time. Flood depth is computed by subtracting the ground 

elevation from the flood elevation. Since these data are usually obtained from different sources, determining whether they are based on 

the same datum is important. If not, standard datum corrections must 

be applied.

In coastal areas, the flood elevations shown on FEMA flood maps account for stillwater flooding plus local wave effects, including wave 

heights, wave runup, or wave overtopping over vertical walls. As shown 

in Figure 5-6, subtracting the ground elevation from the FEMA flood 

elevation results in the flood depth which is comprised of the stillwater 

component and the predicted wave contribution. 

Wave Crest 

Wave 

Height*

Wave Trough

Stillwater

Depth

Flood

Depth**

Ground (or Eroded Ground) Elevation

* Maximum wave height is 78 percent of stillwater depth

** Flood depth including waves is 55 percent greater than the stillwater depth

Figure 5-6:

Definition sketch – 

coastal wave height and 

stillwater depth

For design purposes, it is important to know that wave forces on buildings cause the most damage. FEMA has identified V zones (velocity 

zones) on coastal flood maps, where wave heights or wave runup depths 

are predicted to be 3 feet or greater (see Section 5.1.5.2). However, 

post-disaster assessments and laboratory studies have shown that waves 

heights as small as 1.5 feet can also cause significant damage. While 

FEMA flood maps do not specifically designate flood hazard areas subject to 1.5- to 3-foot waves, referred to as “Coastal A Zones” (see Section 

5.1.5.3), these smaller waves and their potential damaging effects on 

buildings should still be considered. 
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Figure 5-6 also illustrates the two main principles 

used to estimate wave heights at a particular site. 

Equations for wave height are based on the concept 

that waves are depth-limited, that is, waves propagating into shallow water will break when the wave 

height reaches a certain proportion of the underlying stillwater depth. For modeling wave heights 

during the base flood, FEMA utilizes the proportion first determined by the National Academy of 

Sciences (1977): the total wave height will reach a 

maximum of 78 percent of stillwater depth before 

breaking. At any given site, this proportion may be reduced because of 

obstructions between open water and the site, such as dense stands of 

vegetation or unelevated buildings. In V zones, 3-foot waves can be supported in only 4 feet of stillwater and 1.5-foot waves can be supported 

in only 2 feet of stillwater depth. The second principle is that the wave 

height extends from the trough, which is below the stillwater elevation, 

to the crest, which is above the stillwater elevation, and is equal to 55 percent of this stillwater depth. 

Using these two principles, some general rules of thumb are available 

to estimate wave heights. If the only information available is the base 

flood depth (i.e., the flood depth calculated using the FEMA flood 

map elevation minus the ground elevation), assume that flood depths 

between 3 and 6 feet can have an added wave-height component between 1.5 and 3 feet, while flood depths of 6 feet or more will likely 

have wave heights in excess of 3 feet. If only the stillwater flood depth 

is known (from an alternative surge map or other data source), the 

maximum flood depth (including wave height) will be approximately 

1.5 times the stillwater depth. 

In any area with erodible soils, whether coastal or 

inland site, designers must consider the effects 

of erosion where floodwaters lower the ground 

surface or cause local scour around foundation 

elements. The flood depth determined using 

flood elevation and ground elevation should be 

increased to account for changes in conditions 

during a flood event. Not only does lowering the 

ground surface effectively result in deeper water 

against the foundation, it may also remove supporting soil from the foundation, which must be 

accounted for in the foundation design. 

Waves and storm-induced erosion are 

most common in coastal areas. However, 

wide rivers and lakes may experience 

wind-driven waves and erodible soils are 

found throughout the United States. For 

more information about waves and erosion, 

refer to FEMA 55, Coastal Construction 

Manual (2000).

After Hurricane Katrina in 2005, FEMA 

expedited development of Flood Recovery 

Maps and Advisory Base Flood Elevations 

for the Mississippi coast; the new maps 

were delivered less than 3 months after 

the storm. 

In 2004, after widespread wildfires 

in California changed rainfall-runoff 

characteristics, FEMA developed Flood 

Recovery Maps to show increased riverine flood hazards.
5-18 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

5 MAKING SCHOOLS SAFE FROM FLOODING

5.1.4.2 Design Flood Elevation 

The DFE establishes the minimum level of flood protection that must be 

provided. For school buildings, the DFE will always be higher than the 

BFE. Communities may use a design flood that is higher than the base 

flood for a number of reasons. For example, a design flood may be used 

to account for future upland development, to recognize a historic flood, 

or to incorporate a factor of safety, known as freeboard. 

School districts, facility planners, and designers should check with the 

appropriate regulatory authority to determine the minimum flood elevation to be used in site planning and building 

design. If a regulatory authority does not enforce 

a building code that refers to the standard Flood 

Resistant Design and Construction (ASCE 24), planners and designers should examine the provisions 

of that standard and discuss with decisionmakers 

the merits of conforming with this engineering 

standard of care. 

Some State or local regulations cite the 0.2-percent-annual-chance flood (500-year flood) as the 

design requirement for essential and critical facilities such as schools, or the regulations may call for 

added freeboard above the minimum flood elevation. Even if there is no specific requirement to use 

the 0.2-percent-annual-chance flood for siting and 

design purposes, FEMA strongly recommends that 

decisionmakers take into consideration the flood conditions associated 

with this lower probability event.

If significant flood events have occurred since the effective date of the 

FIRM, these events may change the statistical analyses, which might 

prompt FEMA to update of the flood maps and produce revised elevations for the 1-percent-annual-chance flood. School districts, facility 

planners, and designers should contact appropriate community officials 

to determine whether any significant flood events have occurred or if 

other changes that might affect flood hazards have taken place since 

the effective date of the FIRM. The best available information should be 

used at all times. 

“Freeboard” is a factor of safety usually expressed in feet above a flood level. 

Freeboard compensates for the many unknown factors that could contribute to flood 

heights, such as wave action, constricting 

bridge openings, and the hydrological 

effect of urbanization of the watershed.

ASCE 24 requires that new schools with a 

population of 250 or more be constructed, 

at a minimum, to an elevation of the BFE + 

2 feet in V Zones and Coastal A Zones (depending upon the orientation of the lowest 

floor member).
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-19

5.1.4.3 Flood Velocity—Riverine

Few sources of information are readily available for estimating flood velocities at specific locations along riverine bodies of water. If a riverine 

source has been studied using detailed hydraulic methods, some information may be available in summary form in published flood studies. 

Studies prepared for the NFIP contain tables of data for waterways for 

which floodways were delineated (see Section 5.1.5.2). For specified 

cross-sections along the waterway, these Floodway Data Tables include 

mean velocities expressed in feet per second. These values are the average of all velocities across the floodway. Generally, velocities in the flood 

fringe (landward of the floodway) will be lower than in the floodway. 

For waterways without detailed studies, methods that are commonly used 

in civil engineering for estimating open channel flow velocities can be 

applied. 

5.1.4.4 Flood Velocity—Coastal

Estimating flood velocities in coastal flood hazard areas involves considerable uncertainty and there is little reliable historical information or 

measurements from actual coastal flood events. In this context, velocity does not refer to the motion associated with breaking waves, but the 

speed of the mass movement of floodwater over an area.

The direction and velocity of floodwaters can vary significantly throughout 

a coastal flood event. Floodwaters can approach a site from one direction 

as a storm approaches, then shift to another direction (or through several directions) as the storm moves through the area. Floodwaters can 

inundate some low-lying coastal sites from both the front (e.g., ocean) 

and the back (e.g., bay, sound, or river). In a similar manner, at any given site, flow velocities can vary from close to zero to very high. For these 

reasons, when determining flood loads for building design, velocities 

should be estimated conservatively, and floodwaters should be assumed 

to approach from the most critical direction. 

Despite the uncertainties, there are methods to approximate coastal flood velocities. One common 

method is based on the stillwater depth. Designers 

should consider the topography, the distance from 

the source of flooding, and the proximity to other buildings and obstructions before selecting the 

flood velocity for design. Those factors can direct 

and confine floodwaters, with a resulting acceleration of velocities. This increase in velocities is 

Upper bound velocities caused by 

Hurricane Katrina along the Mississippi 

coast, where storm surge depths neared 

25 feet deep (with waves, total flood depths 

approached 35 feet), have been estimated 

at nearly 30 feet per second (20 miles per 

hour).
5-20 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

5 MAKING SCHOOLS SAFE FROM FLOODING

described as the “expected upper bound.” The “expected lower bound” 

velocities are experienced in areas where those factors are not expected 

to influence the direction and velocity of floodwaters. 

Figure 5-7 shows the general relationship between velocity and stillwater depth. For design purposes, actual flood velocities are assumed to lie 

between the upper and lower bounds. Conservative designs will use the 

upper bound velocities.

1

0

5

10

15

20

25

2345 6 7 8

Stillwater Flood Depth (feet)

Velocity (ft/sec)

9 10 11 12 13 14 15

Upper-Bound Velocity

Lower-Bound Velocity

Figure 5-7:

Velocity as a function 

of stillwater flood depth

5.1.5 Flood Hazard Maps and Zones

Flood hazard maps identify areas of the landscape that are subject to 

flooding, usually flooding by the 1-percent-annual-chance flood. Maps 

prepared by the NFIP are the minimum basis of State and local floodplain regulatory programs. Some States and communities have prepared 

maps of a floodplain based on the assumption that the upper watershed 

area is fully developed according to existing zoning. Some communities 

base their regulations on a flood of record or a historically significant 

flood that exceeds the base flood shown on the NFIP maps.

The flood hazard maps used by the appropriate regulatory authority should be consulted during planning and site selection, site design, 

and architectural and engineering design (whether for the design of 

new buildings or rehabilitation of existing buildings). Regardless of the 

flood hazard data required for regulatory purposes, additional research 

should be conducted on past major floods and other factors that could 

lead to more severe flooding.
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-21

5.1.5.1 NFIP Flood Maps

The NFIP produces FIRMs for more than 20,000 

communities nationwide. Flood Insurance Studies 

(FISs) and FIRMs are prepared for each local jurisdiction that has been determined to have some 

degree of flood risk. The current effective maps 

are typically avail-able for viewing in community 

planning or permit offices.2

 Using the most recent 

flood hazard map is important when deter-mining 

site-specific flood hazard characteristics. Although 

many FIRMs are more than 15 years old, often 

one or more panels or portions of a map panel 

have been revised and republished. Communities 

must adopt revised maps to continue participating in the NFIP. 

Some FIRMs do not show the 0.2-percent-annual-chance flood hazard 

area (500-year floodplain), and many FIRMs do not provide detailed 

information about predicted flood elevations along every body of water, especially smaller streams and tributaries. Determining the 500-year 

flood is especially difficult when records of past flood events are limited. 

When existing data are insufficient, additional statistical methods and 

engineering analyses are necessary to determine the floodprone areas 

and the appropriate characteristics of flooding required for site layout 

and building design. If a proposed school site or existing school campus is affected by flooding, a site-specific topographic survey is critical 

to delineate the land that is below the flood elevation used for planning purposes. If detailed flood elevation information is not available, a 

floodplain study may be required to identify the important flood characteristics and data required for sound design. However, having flood 

hazard areas delineated on a map conveys a degree of precision that may 

be misleading. Flood maps have a number of limitations that should be 

taken into consideration, especially during site selection and building 

design. Some of the well-known limitations include:

n Flood hazard areas are approximations based on probabilities; the 

flood elevations shown and the areas delineated should not be taken 

as absolutes, in part because they are based on numerical approximations of the real world. 

n For the most part, floodplains along smaller streams and drainage 

areas (less than 1 square mile) are not shown.

2 Flood maps may also be viewed at FEMA’s Map Service Center at http://msc.fema.gov. For 

a fee, copies may be ordered online or by calling (800) 358-9616. The FIS and engineering 

analyses used to determine the flood hazard area may be ordered through the FEMA Web site.

The number of revised and updated 

FIRMs is increasing rapidly. During the 

last few years, FEMA, in partnership with 

many States and communities, has been 

implementing an initiative to modernize 

and update all maps that are determined 

to be out of date. The modernization process may involve an examination of flood 

experience in the period since the original 

flood studies were prepared, use of more 

detailed topographic and base maps, recomputation of flood discharges and flood 

heights, and re-delineation of flood hazard 

area boundaries.
5-22 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

5 MAKING SCHOOLS SAFE FROM FLOODING

n Especially for older maps, the topography used 

to delineate the flood boundary may have had 

contour intervals of 5, 10, or even 20 feet, which 

significantly affects the precision with which the 

boundary is determined. The actual elevation 

of the ground relative to the flood elevation is 

more critical to consider than whether an area 

is shown as being in or out of the mapped flood 

hazard area. 

n Maps are based on the data available at the time 

they were prepared, and, therefore, do not account for subsequent upland development that 

increases rainfall-runoff, which may increase 

flooding. 

n The scale of the maps may impede precise determinations (many older maps are 1 inch = 

2,000 feet).

n The land surface of the floodplain may have been 

altered by modifications after the maps were prepared, including fills, excavations, or levees.

n Local conditions are not reflected, especially 

conditions that change regularly, such as stream 

bank erosion and shoreline erosion.

n Areas exposed to very low probability flooding are not shown, such 

as flooding from extreme hurricane storm surges, extreme riverine 

flooding, dam failures, or overtopping or failure of levees.

5.1.5.2 NFIP Flood Zones

The flood hazard maps prepared by the NFIP show different flood zones 

to delineate different floodplain characteristics (see Figures 5-8, 5-9, and 

5-10). The flood zones shown on the NFIP maps, and some other designations, are described below.

A Zones: Also called “unnumbered A zones” or “approximate A zones,” 

this designation is used for flood hazard areas where engineering studies 

have not been performed to develop detailed flood elevations. BFEs are 

not provided. Additional engineering analyses and site-specific assessments usually are required to determine the BFE.

AE Zones or A1–A30 Zones:  Also called “numbered A zones,” these 

designations are used for flood hazard areas where engineering analyses have produced detailed BFEs and boundaries for the base flood 

In communities along the Gulf and Atlantic 

coasts, school districts, planners, and 

designers should check with emergency 

management offices or the U.S. Army 

Corps of Engineers for maps that estimate storm surge flooding from several 

hurricane scenarios. Local planning or 

engineering offices may have post-disaster 

advisory flood maps and documentation of 

past storm surge events. The FIRMs and 

regulatory BFEs do not reflect low probability/high magnitude flooding that may 

result from a hurricane making landfall at a 

specific location. 

Be aware that most storm surge maps 

report stillwater flood elevations only; local 

wave heights or wave runup are seldom 

included. If necessary, local wave effects 

should be estimated and added to the 

stillwater elevation when determining flood 

depths for design purposes (see Section 

5.1.4.1). 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-23

(1-percent-annual-chance flood). For riverine 

waterways with numbered A zones, FISs include 

longitudinal profiles showing water surface elevations for different frequency flood events.

Floodways:  The floodway includes the waterway 

channel and adjacent land areas that must be reserved in order to convey the discharge of the base 

flood without cumulatively increasing the water surface elevation above 

a designated height. Floodways are designated for most waterways that 

have AE zones or numbered A zones. FISs include data on floodway 

widths and mean floodway velocities. 

AO and AH Zones: These zones include areas of shallow flooding and are 

generally shown where the flood depth averages from 1 to 3 feet, where 

a clearly defined channel does not exist, where the path of flooding is 

unpredictable, and where velocity flow may be evident. These zones are 

characterized by ponding or sheetflow. BFEs may be provided for AH 

zones; flood depths may be specified in AO zones.

Shaded X (or B) Zones: These designations are used to show areas subject 

to inundation by the 500-year flood (0.2-percent-annual-chance flood), 

or areas protected by flood control levees. These zones are not shown on 

many NFIP maps, though the absence does not imply that flooding of 

this frequency will not occur. 

Base flood elevation (BFE) is the elevation above a datum to which floodwaters 

are predicted to rise during the 1-percentannual-chance flood (also called the “base 

flood” or the 100-year flood).

Figure 5-8: Riverine flood hazard zones 

Zone B (or shaded Zone X) is subject 

to flooding by the 500-year flood 

(0.2-percent-annual-chance), and is a 

moderate risk area.

Zone A, A Zones A1-A30, and Zone AE

are subject to flooding by the base of 

the 1-percent-annual-chance 

(100-year) flood, and are considered 

high-risk areas.

Base Flood Elevation (BFE) is the 

predicted water surface elevation of 

the base flood at specific locations 

(in feet above the datum).

Zone C (or Zone X) is all other areas, considered low-risk.
5-24 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

5 MAKING SCHOOLS SAFE FROM FLOODING

Figure 5-9: Coastal flood hazard zones

Zone X is all 

other areas.

Shaded Zone X (or Zone B) is subject to flooding by the 500-year flood 

(0.2-percent-annual-chance).

Base Flood Elevation (BFE) is the 

predicted water surface elevation 

(in feet above datum).

Zone V, V Zones V1-V30, and Zone VE 

are where waves are expected to be 

3 feet or more.

Zone A, A Zones A1-A30, and Zone AE

are subject to flooding by the base 

or100-year flood (1-percent-annualchance), and waves less than 3 feet.

Figure 5-10: Sample digital FIRM format used for modernized maps

ZONE

X

114

113

112

110

ZONE

X

Unshaded Zone X is the area of minimal flood risk outside the 500-year floodplain 

(formerly called Zone C).

Shaded Zone X is subject to flooding by

the 500-year flood (0.2-percent-annualchance), formerly called Zone B.

Zone AE is the 100-year (1-percentannual-chance) floodplain with BFEs 

(formerly called Zone A1- A30).

The Floodway is the cross-hatched area.

Base Flood Elevation (BFE) is the water 

surface elevation of the base flood at 

specific locations.

Cross Section location, where ground 

surveys determine the shape of the land

and how constrictions such as bridges 

and culverts affect the flow of 

floodwater.

Unshaded X (or C) Zones: These zones are all land areas that are outside of 

the mapped flood hazard area designated for the purposes of regulating 

development. These zones may still be subject to small stream flooding 

and flooding from local drainage problems.
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-25

V Zones (V, VE, and V1–V30): Also known as coastal high hazard areas or 

special flood hazard areas (SFHAs) subject to high-velocity wave action, 

V zones are relatively narrow areas along open coastlines and some large 

lake shores that are subject to high-velocity wave action from storms or 

seismic sources. V zones extend from offshore to the inland limit of primary frontal dunes, or to an inland limit where the predicted breaking 

wave height or wave runup depth drops below 3 feet.

5.1.5.3 Coastal A Zones 

Figure 5-9 shows that coastal floodplains are typically subdivided into 

A zones and V zones. V zones are areas where wave heights or runup 

depths exceed 3 feet or where primary frontal dunes occur. Most NFIP 

maps do not differentiate the portions of the A zone that will experience 

wave heights between 1.5 and 3 feet, which are capable of causing structural damage to buildings. These areas of special concern, called Coastal 

A Zones, can be identified through assessment of coastal flood hazard 

data. Beginning in 2008, when FEMA 

revises and updates FIRMs for coastal 

communities, the inland extent of the 1.5-

foot wave—called the Limit of Moderate 

Wave Action (LiMWA)—will be delineated 

(Figure 5-11).

Coastal A Zones are present where two conditions exist: where the expected stillwater 

flood depth is sufficient to support breaking waves 1.5 to 3 feet high, and where 

such waves can actually occur. The first 

condition occurs where stillwater depths 

(vertical distance between the stillwater 

elevation and the ground) are more than 

2 feet deep. The second condition occurs 

where there are few obstructions between 

the shoreline and the site. In these areas, 

the principal sources of flooding are tides, 

storm surges, seiches, or tsunamis, not riverine flooding. 

The stillwater depth requirement is necessary, but is not sufficient by itself to warrant 

designation as a Coastal A Zone. This is because obstructions in the area may block 

wind (limiting the initial growth of waves) 

or cause friction that attenuates wave 

Figure 5-11:

Illustration of the Limit of Moderate Wave Action, which 

delineates the inland limit of areas referred to as Coastal 

A Zones

Gulf of Mexico

Limit of Moderate Wave Action
5-26 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

5 MAKING SCHOOLS SAFE FROM FLOODING

energy. Obstructions can include buildings, locally high ground, and dense, continuous stands of 

vegetation (trees, shrubs, etc.). Designers should 

determine whether Coastal A Zone conditions are 

likely to occur at a school site because of the anticipated wave action and loads. This determination 

is based on an examination of the site and its surroundings, the actual surveyed ground elevations, and the estimated 

wave heights (calculated using predicted stillwater elevations found in 

the FIS or derived from elevations shown on the FEMA flood map; see 

Section 5.1.4.1).

When a decision is made to build a school in a Coastal A Zone, the 

characteristics of the site and the nature of the flood hazards must be examined prior to making important design decisions. Field observations 

and laboratory research have determined that flooding with breaking 

waves between 1.5 and 3 feet high produces more damage than flooding of similar depths without waves. Therefore, ASCE 24, Flood Resistant 

Design and Construction, specifically requires application of the NFIP’s V 

zone design requirements in Coastal A Zones. Designers are advised to 

pay special attention to two additional considerations:

n Debris loads may be significant in Coastal A Zones landward of V 

zones where damaged buildings, piers, and boardwalks can produce 

battering debris. Damage caused by debris can be minimized if foundations are designed to account for debris impact loads.

n Especially in high-wind regions, designers must pay special attention to the entire roof-to-foundation load path when designing and 

specifying connections. To meet V zone requirements, designs for 

buildings in Coastal A Zones should account for simultaneous wind 

and flood forces. Corrosion-resistant connections are especially important for the long-term integrity of the structure.

5.1.6 Floodplain Management Requirements and Building 

Codes 

The NFIP sets the minimum requirements included in model building 

codes and standards for design and construction methods to resist flood 

damage. The original authorizing legislation for the NFIP is the National 

Flood Insurance Act of 1968 (42 U.S. Code [U.S.C.] 4001 et seq.). In that 

Act, Congress expressly found that “a program of flood insurance can 

promote the public interest by encouraging sound land use by minimizing exposure of property to flood losses...” 

The current editions of the model building 

codes refer to two design standards, ASCE 

7 and ASCE 24. Both standards include 

requirements for Coastal A Zones.
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-27

The most convincing evidence of the effectiveness of 

the NFIP minimum requirements is found in flood 

insurance claim payment statistics. Buildings that 

pre-date the NFIP requirements are, by and large, 

not constructed to resist flood damage. Buildings 

that post-date the NFIP (i.e., those that were constructed after a community joined the program and 

began applying the minimum requirements) are 

designed to resist flood damage. The NFIP reports 

that aggregate loss data indicate that buildings that 

meet the minimum requirements experience 70 

percent less damage than buildings that pre-date 

the NFIP. There is ample evidence that buildings designed to exceed the 

minimum requirements are even less likely to sustain damage. 

5.1.6.1 Overview of the NFIP

The NFIP is based on the premise that the Federal government will make 

flood insurance available in communities that agree to recognize and 

incorporate flood hazard considerations in land use and development 

decisions. In some States and communities, this is achieved by guiding 

development to areas with a lower risk. When decisions result in development within flood hazard areas, application of the criteria set forth in 

Title 44 Code of Federal Regulations (CFR) Section 60.3 is intended to 

minimize exposure and flood-related damage. State and local governments are responsible for applying the provisions of the NFIP through 

the regulatory permitting processes. At the Federal level, the NFIP is 

managed by FEMA and has three main elements:

n Hazard identification and mapping, for which engineering studies are conducted and flood maps are prepared in partnership with 

States and communities. These maps delineate areas that are predicted to be subject to flooding under certain conditions. 

n Floodplain management criteria for development establish the minimum requirements to be applied to development within mapped 

flood hazard areas. The intent is to recognize 

and incorporate flood hazard considerations 

throughout the land development process. 

n Flood insurance, which provides some financial 

protection for property owners to cover floodrelated damage to buildings and contents.

Federal flood insurance is intended to shift some 

of the costs of flood disasters away from the taxpayer by providing property owners, including school 

Construction of public schools may be 

regulated by a State board, school district, 

or State agency and, thus, may not be subject to local permit requirements, including 

local floodplain management regulations. 

In these cases, the NFIP minimum requirements must still be satisfied, whether 

through regulation, Executive order, or a 

State building code. 

If completely destroyed by an event that 

the President declares a major disaster, 

schools in V zones are not eligible for 

post-disaster public assistance funds to 

rebuild on the same site (44 CFR §9.11(d)

(1)). This is another reason to select higher 

(more conservative) design criteria when 

designing and constructing schools in 

areas with a high flood risk.
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5 MAKING SCHOOLS SAFE FROM FLOODING

districts, an alternative to disaster assistance and disaster loans. Disaster 

assistance provides limited funding for repair and cleanup, and is available only after the President signs a major disaster declaration for the 

area. NFIP flood insurance claims are paid any time damage from a 

qualifying flood event3

 occurs, regardless of whether a major disaster is 

declared. Importantly, school districts should be aware that they may be 

subject to a mandated reduction in Federal disaster assistance payments 

if a public school building is damaged by flooding, but is not covered 

by flood insurance. The same restriction applies to private non-profit 

schools that are otherwise eligible for Federal disaster assistance. 

Another important objective of the NFIP is to break the cycle of flood 

damage. Many buildings have been flooded, repaired or rebuilt, and 

flooded again. Before the NFIP, in some parts of the country this cycle was repeated every couple of years, with reconstruction taking place 

in the same floodprone areas, using the same construction techniques 

that did not adequately resist flood damage. NFIP provisions guide development to lower-risk areas by requiring compliance with performance 

measures to minimize exposure of new buildings and buildings that undergo major renovation or expansion (called “substantial improvement” 

or repair of “substantial damage”). This achieves the long-term objective 

of building disaster-resistant communities. 

5.1.6.2 Summary of the NFIP Minimum 

 Requirements

The performance requirements of the NFIP are set 

forth in 44 CFR Part 60. The requirements apply to 

all development, which the NFIP broadly defines to 

include buildings and structures, site work, roads 

and bridges, and other activities. Buildings must be 

designed and constructed to resist flood damage, 

which is primarily achieved through elevation (or 

floodproofing). Additional specific requirements 

apply to existing development, especially existing 

buildings. Existing buildings that are proposed for 

substantial improvement, including restoration 

following substantial damage, are subject to the 

regulations. 

3 For the purpose of adjusting claims for flood damage, the NFIP defines a flood as “a general 

and temporary condition of partial or complete inundation of two or more acres of normally 

dry land area or of two or more properties (at least one of which is the policyholder’s 

property) from: overflow of inland or tidal waters; unusual and rapid accumulation or runoff of 

surface waters from any source; mudflow; or collapse or subsidence of land along the shore 

of a lake or similar body of water as a result of erosion or undermining caused by waves or 

currents of water exceeding anticipated cyclical levels that result in a flood as defined above.”

“Substantial damage” is damage of any 

origin sustained by a structure whereby the 

cost of restoring the structure to its beforedamage condition would equal or exceed 

50 percent of the market value of the structure before the damage occurred. 

“Substantial improvement” is any repair, 

reconstruction, rehabilitation, addition, or 

improvement of a building, the cost of 

which equals or exceeds 50 percent of 

the market value of the building before the 

improvement or repair is started (certain 

historic structures may be excluded). 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-29

Although the NFIP regulations primarily focus on how to build structures, one of the long-term objectives of the program is to guide 

development to less hazardous locations. Preparing flood hazard maps 

and making the information available to the public is fundamental in satisfying this objective. Armed with flood hazard information, people can 

make informed decisions about where to build, how to use site design to 

minimize exposure to flooding, and how to design buildings that will resist flood damage.

The NFIP’s broad performance standards for development sites in flood 

hazard areas include the following requirements:

n Building sites shall be reasonably safe from flooding.

n Adequate site drainage shall be provided to reduce exposure to 

flooding. 

n New and replacement sanitary sewage systems shall be designed to 

minimize or eliminate infiltration of floodwaters into the systems 

and discharges from the systems into floodwaters.

n Development in floodways shall be prohibited, unless engineering 

analyses show that the development will not increase flood levels. 

The NFIP’s broad performance standards for new 

buildings proposed for flood hazard areas (and 

substantial improvement of existing floodprone 

buildings) include the following requirements:

n Buildings shall be designed and adequately 

anchored to prevent flotation, collapse, or lateral movement resulting from hydrodynamic 

and hydrostatic loads, including the effects of 

buoyancy.

n Building materials used below the DFE shall be resistant to flood 

damage.

n Buildings shall be constructed by methods and practices that minimize flood damage (primarily by elevating to or above the DFE, or 

by specially designed and certified floodproofing measures).

n Buildings shall be constructed with electrical, heating, ventilation, 

plumbing, and air-conditioning equipment and other service facilities that are designed and/or located to prevent water from entering 

or accumulating within the components.

School planners and designers should determine whether there are 

any applicable State-specific requirements for floodplain development. 

The IBC and ASCE 24 contain several 

requirements that exceed or are more specific than the NFIP minimum requirements. 

The most notable is the requirement that 

schools and certain other buildings and 

structures be elevated to the higher of the 

DFE or the BFE plus 1 or 2 feet.
5-30 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

5 MAKING SCHOOLS SAFE FROM FLOODING

Some States require that local jurisdictions apply standards that exceed 

the minimum requirements of the NFIP. In particular, some States require that schools be located outside of the floodplain (including the 

500-year floodplain). Some states require that schools are designed and 

constructed to resist conditions associated with the 500-year flood or other higher standards, and some States have direct permitting authority 

over public school construction. 

As participants in the NFIP, States are required to ensure that development activities that are not subject to local regulations, such as the 

development of State-owned properties, comply with the same performance requirements as those enforced by local jurisdictions. If schools 

are exempt from local permits, this may be accomplished through a State 

building permit, a governor’s executive order, or other mechanisms that 

apply to entities not subject to local authorities.

5.1.6.3 Executive Order 11988 and Critical Facilities 

When Federal funding is provided for the planning, design, and construction of new critical facilities, or for the repair of existing critical 

facilities that are located within the 500-year floodplain, the funding 

agency is required to address additional considerations. Executive Order 

11988, Floodplain Management, requires Federal agencies to apply a 

decisionmaking process to avoid, to the extent possible, the long- and 

short-term adverse impacts associated with the occupancy and modification of floodplains, and to avoid the direct or indirect support of 

floodplain development whenever there is a practicable alternative. If 

there is no practicable alternative, the Federal agency must take steps to 

minimize any adverse impacts to life, property, and the natural and beneficial functions of floodplains. 

The Executive order establishes the BFE as the 

minimum flood elevation that must be used by 

all Federal agencies. Implementation guidance 

specifically addresses “critical actions,” which are 

described as those actions for which even a slight 

chance of flooding would be too great. The construction or repair of critical facilities, such as 

schools, hospitals and clinics, fire stations, emergency operations centers, and facilities for storage 

of hazardous wastes or storage of critical records, 

are examples of critical actions. 

After determining that a site is in a mapped flood 

hazard area, and after giving public notice, the 

States often use governors’ executive 

orders to influence State-constructed and 

State-funded critical facilities, requiring 

location outside of the 500-year floodplain 

where feasible, or protection to the 500-

year flood level if avoiding the floodplain 

is not practical. In 2004, a review of State 

and local floodplain management programs determined that Alabama, Illinois, 

Michigan, New York, North Carolina, Ohio, 

and Virginia have requirements for critical 

facilities (ASFPM, 2004). Although not 

identified in that review, other States may 

have similar restrictions.
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Federal funding agency is required to identify and evaluate practicable alternatives to locating a critical facility in a 500-year floodplain. If 

the Federal agency has determined that the only practicable alternative is to proceed, then the impacts of the proposed action must be 

identified. If the identified impacts are harmful to 

people, property, and the natural and beneficial 

functions of the floodplain, the Federal agency is 

required to minimize the adverse effects on the 

floodplain and the funded activity.

Having identified the impacts of the proposed action and the methods to minimize these impacts, 

the Federal agency is required to re-evaluate the 

proposed action. The re-evaluation must consider whether the action 

is still feasible, whether the action can be modified to relocate the facility or eliminate or reduce identified impacts, or whether a “no action” 

alternative should be chosen. If the finding results in a determination 

that there is no practicable alternative to locating a critical facility in 

the floodplain, or otherwise affecting the floodplain, then a statement 

of findings and a public explanation must be provided. 

5.1.6.4 Model Building Codes and Standards

The IBC and NFPA 5000 were the first model codes to include comprehensive provisions that address flood hazards. Both codes are consistent 

with the minimum provisions of the NFIP that pertain to the design and 

construction of buildings and structures. The NFIP requirements that 

pertain to site development, floodways, coastal setback lines, erosionprone areas, and other environmental constraints 

are found in other local ordinances.

The IBC and NFPA 5000 incorporate by reference 

a number of standards that are developed through 

a formal or accredited consensus process. The 

best known is ASCE 7. The model building codes 

require designers to identify and design for anticipated environmental loads and load combinations 

including wind, seismic, snow and flood loads, 

as well as the soil conditions. The designer must 

identify the pertinent, site-specific characteristics 

and then use ASCE 7 to determine the specific 

loads and load combinations. In effect, the process is similar to a local floodplain ordinance that 

requires determination of the environmental condition (in/out of the mapped flood hazard area, 

DFE/depth of water), and then specifies certain 

FEMA’s eight-step decisionmaking process 

for complying with Executive Order 11988 

must be applied before Federal disaster 

assistance is used to repair, rehabilitate, or 

reconstruct damaged existing critical facilities in the 500-year floodplain.

ASCE 7 outlines methods to determine 

design loads and load combinations in 

flood hazard areas, including hydrostatic 

loads, hydrodynamic loads, wave loads, 

and debris impact loads. In order to compute the loads and load combinations the 

designer must identify site-specific characteristics, including flood depths, velocities, 

waves, and the likelihood that debris 

impacts need to be considered. 

ASCE 24 addresses design and construction requirements for structures in flood 

hazard areas, including coastal highhazard areas (V Zones), “Coastal A Zones,” 

and other flood hazard areas (A Zones).
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conditions that must be met during design and construction. The 1998 

edition of ASCE 7 was the first version of the standard to include flood 

loads explicitly, including hydrostatic loads, hydrodynamic loads (velocity and waves), and debris impact loads. 

The IBC and NFPA 5000 also incorporate ASCE 24 by reference. ASCE 

24 is a standard that was first published by ASCE in 1998 and revised in 

2005. Developed through a consensus process, ASCE 24 addresses specific topics pertinent to designing and constructing buildings in flood 

hazard areas, including floodways, coastal high-hazard areas, and other high-risk flood hazard areas, such as alluvial fans, flash flood areas, 

mudslide areas, erosion-prone areas, and high-velocity areas. 

Prior to the 2010 edition, ASCE 7 and the model building codes classified structures into four categories based on use or occupancy, each 

with different requirements, and schools were classified based on capacity. The 2010 edition of ASCE 7 categorizes buildings and structures 

into “risk categories” and no longer includes lists of specific facilities 

under each category. Schools are expected to be designated as Risk 

Category III or Risk Category IV in ASCE 7-10:

n Risk Category III – Buildings and structures the failure of which 

could pose a substantial risk to human life and those not included 

in Risk Category IV with “potential to cause a substantial economic impact and/or mass disruption of day-to-day civilian life in the 

event of failure.” 

n Risk Category IV – Buildings and structures designated as essential facilities, and those for which failure could pose a substantial 

hazard to the community. Essential facilities are defined as those 

“intended to remain operational in the event of extreme environmental loading from wind, snow, or earthquakes.”

ASCE 24 incorporates the ASCE 7 building classifications (occupancy categories) and establishes elevation requirements for each risk 

category. Table 5-1 summarizes these elevation requirements, which 

exceed the NFIP minimum requirements for schools. 
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Table 5-1: ASCE/SEI 24 provisions related to the elevation of schools

Occupancy Category III Occupancy Category IV

Elevation of Lowest Floor or Bottom of Lowest Horizontal Structural Member

A Zone: elevation of lowest floor BFE + 1 foot or DFE, 

whichever is higher

BFE + 2 feet or DFE, 

whichever is higher

V Zone and Coastal A Zone: where the lowest horizontal 

structural member is parallel to direction of wave approach

BFE + 1 foot or DFE, 

whichever is higher

BFE + 1 foot or DFE, 

whichever is higher

V Zone and Coastal A Zone: where the lowest horizontal 

structural member is perpendicular to direction of wave 

approach

BFE + 2 feet or DFE, 

whichever is higher

BFE + 2 feet or DFE, 

whichever is higher

Elevation Below which Flood Damage-Resistant Materials Shall be Used

A Zone BFE + 1 foot or DFE, 

whichever is higher

BFE + 2 feet or DFE, 

whichever is higher

V Zone and Coastal A Zone: where the lowest horizontal 

structural member is parallel to direction of wave approach

BFE + 2 feet or DFE, 

whichever is higher

BFE + 2 feet or DFE, 

whichever is higher

V Zone and Coastal A Zone: where the lowest horizontal 

structural member is perpendicular to direction of wave 

approach

BFE + 3 feet or DFE, 

whichever is higher

BFE + 3 feet or DFE, 

whichever is higher

Minimum Elevation of Utilities and Equipment

A Zone BFE + 1 foot or DFE, 

whichever is higher

BFE + 2 feet or DFE, 

whichever is higher

V Zone and Coastal A Zone: where the lowest horizontal 

structural member is parallel to direction of wave approach

BFE + 2 feet or DFE, 

whichever is higher

BFE + 2 feet or DFE, 

whichever is higher

V Zone and Coastal A Zone: where the lowest horizontal 

structural member is perpendicular to direction of wave 

approach

BFE + 3 feet or DFE, 

whichever is higher

BFE + 3 feet or DFE, 

whichever is higher

Dry Floodproofing

A Zone: elevation to which dry floodproofing extends BFE + 1 foot or DFE, 

whichever is higher

BFE + 2 feet or DFE, 

whichever is higher

V Zone and Coastal A Zone: dry floodproofing not allowed Not allowed Not allowed

5.2 Schools Exposed to Flooding

5.2.1 Identifying Flood Hazards at School Sites

School districts, facility planners, and designers of schools and 

school campuses should investigate site-specific flood hazards and 

characteristics as part of site selection to understand the risks of 

locating new buildings and other improvements on a site. Where practical, buildings and athletic fields should be located outside of known 

flood hazard areas. The best available information should be examined, 

including flood hazard maps, records of historical flooding, storm surge 

maps, and advice from local experts and others who can evaluate flood 

risks. Table 5-3 in Section 5.6 outlines questions that should be answered 

prior to initiating site layout and design work.
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This same investigation should be undertaken when examining existing 

schools and when planning improvements or rehabilitation work. 

5.2.2 Vulnerability: What Flooding Can Do to Existing Schools

Existing schools that are located in flood hazard areas are exposed to 

flood damage. The nature and severity of damage are functions of sitespecific flood characteristics. As described below, damage may include: 

site damage; structural and nonstructural building damage; destruction 

or impairment of service equipment; loss of contents; and health and 

safety threats due to contaminated floodwater.

Regardless of the nature and severity of damage, flooded schools are 

typically not functional while cleanup and repairs are undertaken. The 

length of closure, and thus the impact on the ability of the school district 

to provide instruction, depends on the severity of the damage and lingering health hazards. It may also depend on whether the building was fully 

insured or whether disaster assistance is made available quickly to allow 

speedy repairs and reconstruction. Sometimes, repairs are put on hold 

pending a determination of whether a school should be rebuilt on the 

same site. When damage is substantial, rehabilitation or reconstruction is 

allowed only if full compliance with flood-resistant design requirements 

is achieved (see Section 5.1.6.2).

5.2.2.1 Site Damage

The degree of site damage associated with flooding is a function of several variables related to the characteristics of the flood, as well as the site 

itself.

Erosion and scour: All parts of a school site that are subject to flooding by 

fast-moving water could experience erosion, and local scour could occur 

around any permanent obstructions to flow. Graded areas, filled areas, 

and cut or fill slopes are especially susceptible. Stream and channel bank 

erosion, and erosion of coastal shorelines, are natural phenomena that 

may, over time, threaten site improvements and buildings. 

Debris and sediment: Even when buildings are not subject to water damage, floods can deposit large quantities of debris and sediment that can 

damage a site and be expensive to remove, especially from athletic fields. 

Landscaping: Grass, trees, and plants suffer after floods, especially longduration flooding that prevents oxygen uptake, and coastal flooding that 

stresses plants that are not salt-tolerant. Fast-moving floodwaters and 

waves can also uproot plants and trees.
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Fences: Some types of fences that are relatively solid 

can significantly restrict the free flow of floodwaters 

and trap floating debris. Fences can be damaged or 

knocked down by the pressure of flowing water, or 

by the buildup of debris, which can result in significant loads. 

Playing field surfaces: In addition to damage by erosion and scour, graded grass fields and applied track surfaces can be damaged by standing 

water and deposited sediments.

Accessory structures: Accessory structures, such as storage sheds, bleachers, restrooms, and refreshment stands, can sustain both structural and 

nonstructural damage. Such structures may be designed and built using 

techniques that minimize damage potential, without requiring elevation 

above the DFE. 

Access roads:  Access roads that extend across 

floodprone areas can be damaged by erosion, 

washout of drainage culverts, failure of fill and 

bedding materials, and loss of road surface (see 

Figure 5-12). Road damage could prevent uninterrupted access to a school and thus impair its 

functionality. 

Parking lots: Paved parking lots can be damaged 

by failure of bedding materials and loss of driving 

surface. 

Stormwater management facilities and site drainage:  Site improvements such as swales and 

stormwater basins can be eroded, filled with sediments, or clogged by debris.

Vehicles: If left in floodprone areas, vehicles may 

not be functional and available for service immediately after a flood, and must be replaced or 

cleaned to be serviceable (see Figure 5-13).

Damage to other site elements, such as 

water supply, sewer lines, underground 

and aboveground tanks, and emergency 

power generators, is discussed in Section 

5.2.2.5.

Figure 5-12:

Flooding caused the failure of this road bed

SOURCE: U.S. ARMY CORPS OF ENGINEERS
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Figure 5-13: 

School bus washed 

away by storm surge 

5.2.2.2 Structural Damage

Structural damage includes all damage to the load-bearing portions 

of a building. Local drainage systems around school buildings may be 

inadequate to handle high volume runoff from large expanses of pavement, sometimes resulting in water entering the buildings. Damage to 

other components of buildings is described below, including nonstructural components (Section 5.2.2.3), utility system equipment (Section 

5.2.2.4), and contents (Section 5.2.2.5). 

Depth: The hydrostatic load against a wall or foundation is directly related to the depth of water. Standard studs and siding, or unreinforced 

brick veneer walls, may collapse under hydrostatic loads associated with 

relatively shallow water. Reinforced masonry walls perform better than 

unreinforced masonry walls (see Figure 5-14); however, an engineering analysis is required to determine performance. Walls and floors of 

below-grade areas (basements) are particularly susceptible to damage by 

buoyancy forces. When soils are saturated, pressures against below-grade 
MAKING SCHOOLS SAFE FROM FLOODING 5 

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Figure 5-14: 

Interior unreinforced masonry walls of the 

Port Sulphur High School in Louisiana were 

damaged by hydrostatic loads associated with 

Hurricane Katrina’s storm surge (2005) 

walls are a function of the total depth of water, including the depth below-grade, and the weight of the saturated soils.

Buoyancy and uplift:  If below-grade areas are essentially watertight, 

buoyancy or uplift forces can float a building out of the ground or rupture concrete slabs-on-grade (see Figure 5-15). Buildings that are not 

adequately anchored can also be floated or pushed off foundations. Although rare for large and heavy school buildings, this is a concern for 

outbuildings and portable (temporary) classrooms. Buoyancy is a significant concern for underground and aboveground tanks, especially those 

used for emergency generator fuel.

Duration: By itself, saturation is unlikely to result in significant structural 

damage to masonry construction, although water infiltration through 

the masonry walls is likely even during short periods of inundation. 

Saturation of soils, a consequence of long-duration flooding, increases 

pressure on below-grade foundation walls. 
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Velocity, wave action, and debris impacts:  Each of these components 

of dynamic loads can result in structural damage if buildings are not 

designed to resist overturning, repetitive pounding by waves, or shortduration impact loads generated by floating debris. 

Erosion and scour: Structural damage is associated with foundation failure 

when erosion or scour results in partial or complete removal of supporting soil (see Figure 5-16). Erosion of slopes, especially unprotected slopes, 

can lead to slope failures and loss of soils required to support foundations.

Figure 5-15: 

Concrete slab ruptured 

by hydrostatic pressure 

(buoyancy) induced 

by the floodwaters of 

Hurricane Katrina (2005)

Figure 5-16: 

Scour undermined the 

foundation of St. Paul 

Catholic School, Pass 

Christian, LA. 
MAKING SCHOOLS SAFE FROM FLOODING 5 

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5.2.2.3 Nonstructural Damage

Many floodprone buildings are exposed to floodwaters that are not fast moving, or that may be 

relatively shallow and not result in structural 

damage. Simple inundation and saturation of 

the building and finish materials can result in 

significant and costly damage, including longterm health complications associated with mold. 

Floodwaters often are contaminated with chemicals, petroleum products, and sewage. Under such 

circumstances, recovery generally involves removal of nonstructural materials and finishes because 

cleanup and decontamination are expensive and 

time-consuming. Damage to contents is described 

in Section 5.2.2.5. 

Saturation damage can vary as a function of the duration of exposure. 

Some materials are not recoverable even after very brief inundation, 

while others remain serviceable if in contact with water for only a few 

hours. Use of water-resistant materials will help to minimize saturation 

damage and reduce the costs of cleanup and restoration to service. (For 

more information, see FEMA NFIP Technical Bulletin 2, Flood DamageResistant Materials Requirements [2008].)

Wall finishes: Painted concrete and concrete masonry walls usually resist 

water damage, provided the paint used can be readily cleaned. Tiled 

walls may resist water damage depending on the type of adhesive and 

foundation (gypsum board substrate and wood-framed walls with tile 

do not typically remain stable). 

Flooring:  Most schools have durable floors that resist water damage. 

Ground floors are often slab-on-grade and finished with tile or sheet 

products. Flooring adhesives that have been in use since the early 1990s 

are often latex-based and tend to break down when saturated (see Figure 5-17). Most carpeting, even the indoor-outdoor kind, is difficult to 

clean. Wood floors are particularly susceptible to saturation damage. 

Short duration inundation may not cause permanent deformation of 

some wood floors, such as may be present in older buildings. However, 

because of low tolerance for surface variations, gymnasium floors are 

particularly sensitive and tend to warp after flooding of any duration.

EPA’s Mold Remediation in Schools and 

Commercial Buildings (2001) offers guidelines for the remediation/cleanup of mold 

and moisture problems in schools and 

include measures designed to protect the 

health of building occupants and remediators. Designed primarily for use by school 

managers and custodians, it provides a 

basis for making judgments as to whether 

the remediation should be handled 

in-house. The guidance outlines mold 

remediation plans, whether developed by 

school personnel or by outside contractors. 
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5 MAKING SCHOOLS SAFE FROM FLOODING

Wall and wood components: When soaked for long periods of time, some 

materials change composition or shape. Most types of wood swell when 

wet and, if dried too quickly, will crack, split, or warp. Plywood can delaminate and wood door and window frames may swell and become unstable. 

Gypsum wallboard, wood composition panels, other wall materials, and 

wood cabinetry not intended for wet locations can fall apart. The longer these materials are wet, the more moisture, sediment, and pollutants 

they absorb and the more likely that mold growth will develop. Some 

materials, such as the paper facing on gypsum wallboard, “wick” standing 

water, resulting in damage above the high-water line (see Figure 5-18). 

Metal components: Metal structural components are unlikely to be permanently damaged by short-term inundation. However, hollow metal 

partitions are particularly susceptible when in contact with water because 

they cannot be thoroughly dried and cleaned. Depending on the degree 

of corrosion protection on the metal, repetitive flooding by saline coastal 

waters may contribute to long-term corrosion.

Figure 5-17: 

This parquet wood gymnasium floor was 

damaged by dimensional changes due to 

saturation (Hurricane Katrina 2005)
MAKING SCHOOLS SAFE FROM FLOODING 5 

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Metal connectors and fasteners: Depending on the composition of the 

metal, repetitive flooding, especially by saline coastal waters, may contribute to long-term corrosion. Connectors and fasteners are integral to 

the structural stability of buildings; therefore, failure caused by accelerated corrosion would jeopardize the building. 

5.2.2.4 Utility System Damage

Utility system service equipment that is exposed to flooding is vulnerable 

to damage. Damage may result in a total loss, or may require substantial 

cleaning and restoration efforts. The degree of damage varies somewhat 

as a function of the characteristics of flooding. Certain types of equipment and installation measures will help minimize damage and reduce 

the costs of cleanup and restoration to service.

Equipment and appliances:  Installation below the flood level exposes 

equipment and appliances to flood forces, including drag resulting from 

flowing water and buoyancy. Gas-fired appliances are particularly dangerous. flotation can separate appliances from gas sources, resulting in 

fires and explosive situations. Displaced equipment may dislodge lines 

from fuel oil tanks, contributing to the threat of fire and causing water 

pollution and environmental damage.

Elevators: If located in areas subject to flooding, elevator components, 

equipment, and controls will be damaged, and movement between floors 

will be impaired.

Figure 5-18: 

Saturation damage 

extends above the water 

line in this grade school 

in Gurnee, IL. 
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5 MAKING SCHOOLS SAFE FROM FLOODING

Metal components: Corrosion of metal components, whether from inundation or salt aerosols in coastal areas, may not be apparent immediately 

but can increase maintenance demand and shorten the useful life of 

some equipment and appliances. 

Electrical systems and components: Electrical systems and components, 

and electrical controls of heating, ventilation, and air-conditioning 

systems, are subject to damage simply by getting wet, even for short durations. Unless specifically designed for wet locations, switches and other 

electrical components can short out due to deposits of sediment, or otherwise not function, even when allowed to dry before operation. Wiring 

and components that have been submerged may be functional, though 

it is generally more cost-effective to discard flooded outlets, switches, and 

other less-expensive components than to attempt a thorough cleaning.

Communications infrastructure: Critical communications infrastructure, 

such as control panels and wiring for warning systems, 911 systems, and 

regular telephone and wireless networks, are most susceptible to failure 

during emergencies if located in below-grade basements. 

Ductwork:  Ductwork is subject to two flood-related problems. Flood 

forces can displace ductwork, and saturated insulation can overload the 

ductwork support straps, causing failure.

Mold and dust: Furnaces, air handlers, and ductwork that have been submerged must be thoroughly cleaned and sanitized. Otherwise, damp 

conditions contribute to the growth of mold and accumulated sediment 

can be circulated throughout the school, causing respiratory problems. 

Fiberglass batt or cellulose insulation that has been submerged cannot 

be sanitized and must be replaced. In sensitive environments, ductwork 

should be replaced rather than cleaned.

Gas-fired systems: Waterborne sediment can impair safe functioning of 

jets and controls in gas-fired furnaces and water heaters, necessitating 

professional cleaning and inspection prior to restoration of service. Control equipment (valves, electrical switches, relays, temperature sensors, 

circuit breakers, and fuses) that has been submerged may pose an explosion and fire hazard and should be replaced.

Emergency power generators: Generators installed at-grade are susceptible to inundation and will be out of service after a flood (see Figure 

5-19). Even if fuel tanks are located above flood level, truck access for 

refueling would be impaired if the site is flooded for any length of time.
MAKING SCHOOLS SAFE FROM FLOODING 5 

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Tanks (underground): Underground storage tanks are subjected to significant buoyant forces and can be displaced, especially when long-duration 

flooding occurs and the surrounding soils become saturated. 

Tanks (aboveground): Permanently installed aboveground storage tanks 

are subject to buoyant forces and displacement caused by moving water. 

Standard strapping of propane tanks may be inadequate for the anticipated loads. 

Public utility service:  Damage to public utility service (potable water 

supply and wastewater collection) can affect operations and may cause 

damage to schools:

n Potable water supply systems may become contaminated if distribution lines or treatment facilities are damaged, or if wellheads are 

submerged.

n During heavy rains, sewers back up from infiltration and inflow of 

stormwater into the sewer lines and manholes, cross connections between storm and sanitary sewers, and flooded wastewater treatment 

plants. Sewer backup into a school poses a major health hazard. 

Even when the water has receded, exposed building components, 

finish materials, and contents are contaminated, and usually must be 

removed because adequate cleaning is difficult, if not impossible. 

Figure 5-19: 

Although it was 

anchored and 

not displaced by 

floodwaters, this 

generator was out of 

service after being 

submerged (Hurricane 

Katrina, 2005)
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5 MAKING SCHOOLS SAFE FROM FLOODING

5.2.2.5 Contents Damage

Schools contain equipment and contents that can be damaged and unrecoverable when exposed to flooding. For the purpose of this description, 

the term “contents” includes items such as furniture, kitchen goods and 

equipment, computers, laboratory equipment and materials, records, 

and library materials. The following types of contents are often total losses after flooding.

Furniture: Porous woods become saturated and swollen, and joints may 

separate. Generally, furniture with coverings or pads cannot be restored. 

Metal furniture is difficult to thoroughly dry and clean, is subject to corrosion, and is typically discarded. Depending on the type of wood, some 

wood furniture may be recoverable after brief inundation. 

Computers: Flood-damaged computers and peripheral equipment cannot be restored after inundation (see Figure 5-20), but special recovery 

procedures may be able to recover information on hard drives.

School records: When offices are located in floodprone spaces, valuable 

school records may be lost. Although expensive, some recovery of computerized and paper records may be possible with special procedures.

Library books and collections: Recovery of library materials and special 

collections that are saturated by floodwaters is generally difficult and 

expensive. 

Figure 5-20: 

Destroyed computers 

and peripheral 

equipment, Nichols 

Elementary School, 

Biloxi, MS 
MAKING SCHOOLS SAFE FROM FLOODING 5 

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Laboratory materials and equipment: Depending on the nature of laboratory materials, cleanup may require special procedures. Generally, 

equipment is difficult to restore to safe functioning.

Kitchen goods and equipment:  Stainless steel equipment and surfaces 

generally have cleanable surfaces that can be disinfected and restored to 

service. Because of contamination, all food stuffs and perishables must 

be discarded. 

5.3 Requirements and Best Practices in Flood 

Hazard Areas

5.3.1 Evaluating Risk and Avoiding Flood Hazards

Flood hazards are very site-specific. When a flood hazard map is prepared, lines drawn on the map appear to define the hazard area 

precisely. Land that is on one side of the line is “in” the mapped 

flood hazard area, while the other side of the line is “out.” Although the 

delineation may be an approximation, having hazard areas shown on a 

map facilitates avoiding such areas to the maximum extent practical. If 

those areas are unavoidable, school districts should carefully evaluate 

all of the benefits and all of the costs in order to determine long-term 

acceptable risks, and to develop appropriate plans for design and construction of new schools.

When a decision is made to build a new school on a site that is affected by 

flooding, the characteristics of the site and the nature of flooding must 

be examined prior to making several design decisions. The most important consideration is location of the buildings.

Risks and certain costs associated with flood-resistant construction are 

minimized by putting principal buildings on the highest available ground. 

Siting decisions for buildings, parking lots, and athletic fields should consider all site constraints, which may include the presence of flood hazard 

areas (see Table 5-3 in Section 5.6), wetlands, poor soils, steep slopes, sensitive habitats, mature tree stands, and other environmental factors as 

required by all applicable regulatory authorities. It should be possible to 

avoid siting new schools in riverine floodways and coastal areas subject to 

significant waves (V zones).

Section 5.2 describes the damage sustained by existing buildings exposed to flood hazards. Physical damage and loss of function are avoided 

if schools are located away from flood hazard areas.
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Flood hazard areas designated as V zones on FIRMs 

are relatively narrow areas along open coasts and 

lake shores where the base flood conditions are 

expected to produce 3-foot or higher waves. V 

zones, sometimes called coastal high hazard areas 

or SFHAs subject to high-velocity wave action, are 

found on the Pacific, Gulf, and Atlantic coasts, and 

around the Great Lakes. Every effort should be 

made to locate schools outside of V zones, because 

the destructive nature of waves makes it difficult to 

design a building to be fully functional during and 

after a flood event. This is particularly true in coastal areas subject to hurricane surge flooding. 

5.3.2 Benefits and Costs: Determining Acceptable Risk

Many decisions made with respect to schools are, in part, based on a 

determination of acceptable risk. Risk includes the potential losses associated with a hazard. Ideally, risks can be defined in terms of expected 

probability and frequency of the hazard occurring, the people and property exposed, and the potential consequences. 

Choosing a site or accepting donated land that is affected by flooding is 

a decision to accept some degree of risk. Although the floodprone land 

may have a lower initial cost, the incremental costs of construction, plus 

the likely increased costs of maintenance, repair, and replacement, may 

be significant. Another cost of locating a school in a floodprone area 

is related to access problems if streets and access 

roads are impassable. The building may be elevated 

and protected, but if access is restricted periodically, then the use of the school is affected.

In communities with expansive flood hazard areas, 

there may be no practical alternatives to using a 

floodprone site. In these situations, an evaluation 

of acceptable risk should lead to selection of design 

measures that exceed the minimum requirements 

to mitigate the impacts of flooding. 

The school district’s planning team and the design 

team can influence the degree of risk (e.g., the frequency and severity of flooding that may affect the 

site). They control it through the selection of the site design and the 

building design measures. Fundamentally, this process is a balancing of 

the benefits of an acceptable level of disaster resistance with the costs of 

Schools should not be located in V zones if 

alternate locations are available. Because 

of the effects of waves and potential for 

erosion and scour, construction in V zones 

must meet certain design and construction 

requirements that are different from those 

required in A zones. This section identifies 

these differences. 

Extreme hurricane storm surge flooding 

may be a very low-probability event, but 

the flood depths and wave heights may be 

much more severe than the conditions of 

the base flood shown on the FIRMs. The 

potential impacts on a school must be 

carefully considered in order to make an 

informed decision regarding acceptable 

risk and potential damage. If possible, 

areas subject to extreme storm surge 

flooding should be avoided when locating 

schools. 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-47

achieving that degree of protection. With respect to mitigation of future 

hazard events:

n Benefits are characterized and measured as future damage avoided 

if mitigation measures (including avoiding flood hazard areas) are 

implemented.

n Costs are the costs associated with implementing measures to eliminate or reduce exposure to hazards.

Benefits other than avoided physical damage are difficult to measure. 

They are associated with future damage that does not occur because of the 

mitigation activity, cleanup that is not required because of the mitigation 

activity, and continued education of children because flooding does not 

shut down a school. In addition, benefits accrue over long periods of time, 

making it difficult to make a direct comparison of the benefits with the upfront costs of mitigation. Mitigation costs can be more readily expressed 

in terms of the higher costs of a flood-free site, or the initial capital costs 

of work designed to resist flood damage. Thus, without full accounting of 

both benefits and costs, decisionmakers may not be able to make fully informed decisions. Some questions that should be answered include:

n If the site is floodprone and the building is out of the flood hazard area or is elevated on fill, what are the average annual cleanup 

costs associated with removal of sand, mud, and debris deposited by 

floods of varying frequencies?

n If the school is elevated by means other than fill, will periodic inundation of the exposed foundation elements cause higher average 

annual maintenance costs?

n If the school is protected with floodproofing measures, what are the 

costs of annual inspection, periodic maintenance and replacement 

of materials, and staff training and drills?

n If the school meets only the minimum elevation requirements, what 

are the average annual damages and cleanup costs over the anticipated useful life of the building, including the occurrence of floods 

that exceed the design flood elevation?

n How do long-term costs associated with periodic inundation compare to up-front costs of selecting a different site or building to a 

higher level of protection?

n If a site outside of the flood hazard area is available but less than 

optimal in terms of access by the community, are the trade-offs 

acceptable?
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5 MAKING SCHOOLS SAFE FROM FLOODING

n If the school is located in a hurricane-prone community, how should 

the school design account for low-probability, but high-impact, storm 

surge flooding?

n If access to the school is periodically restricted by flooding, especially 

long-duration flooding, what are the resulting cost effects? How often would the school district have to provide an alternate location to 

continue classes?

5.3.3 Site Modifications

When sites being considered for schools are determined to be prone to 

flooding, facility planners and designers may want to evaluate the feasibility of certain site modifications in order to provide an increased level 

of protection to buildings. The evaluations involve engineering analyses 

to determine whether the desired level of protection is cost effective, and 

whether the proposed site modifications alter the floodplain in ways that 

could increase flooding. The effectiveness of typical site modifications 

and their ramifications must be examined for each specific site. 

Earthen fill: Fill can be placed in the flood hazard area to elevate an entire site above the DFE. If the fill is placed and compacted to be stable 

during the rise and fall of floodwaters, and if the fill is protected from 

erosion, then modifying a site with fill to elevate a school is preferred 

over other methods of elevation. Not only will buildings be less exposed 

to flood forces, but, under some circumstances (such as long-duration 

floods), schools may be able to continue to function. Whether nonstructural fill is placed solely to modify the site, or structural fill is placed to 

elevate buildings, placement of fill can change flooding characteristics, 

including increased flooding on other properties. Engineering analyses 

can be conducted to determine whether eliminating floodplain storage 

by filling will change the direction of the flow of water, create higher 

flow velocities, or increase the water surface elevation in other parts of 

the floodplain.

In Coastal A Zones, back bays, and along the banks of wide rivers where 

wave action is anticipated, fill is a less-effective site modification method 

because wave action may erode the fill, and adequate armoring or other, 

protection methods can be expensive. 

In V zones, structural fill is not allowed as a method of elevating buildings. Beachfront areas with sand dunes pose special problems. Manmade 

alterations of sand dunes are not allowed unless analyses indicate that 

such modifications will not increase potential flood damage. 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-49

Excavation: Excavation on a given parcel of land alone rarely results in 

significant alteration of the floodplain. Excavation that modifies a site is 

more commonly used in conjunction with fill in order to offset or compensate for the adverse impacts of fill.

Earthen levee: A levee is a specially designed barrier that modifies the 

floodplain by keeping the water away from certain areas (see Figure 

5-21a). Levees are significant structures that require detailed, site-specific geotechnical investigations; engineering analyses to identify whether 

flooding will be made worse on other properties; structural and site design to suit existing constraints; design of interior drainage (on the land 

side); and long-term commitment for maintenance, inspection, and repairs. Areas behind levees are protected only up to a certain design flood 

level—once overtopped or breeched, most levees fail and catastrophic 

flooding results. Levees that protect schools and other critical facilities 

usually are designed for at least the 0.2-percent-annual-chance flood 

(500-year) and have freeboard to increase the factor of safety. Depending on the site layout and duration of flooding, access for vehicles can be 

problematic. Low levees can be designed with road access; higher levees 

can be designed with vehicle access points that require special closures 

when flooding is predicted.

Floodwall: Floodwalls are similar to levees in that they provide protection 

to certain areas (see Figure 5-21b). Failure or overtopping of a floodwall 

can result in catastrophic flooding. A floodwall is a significant structure 

designed to hold back water of a certain depth based on the design flood 

for the site. Generally, floodwalls are most effective in areas with relatively shallow flooding and minimal wave action. As with levees, designs 

must accommodate interior drainage on the land side, and maintenance 

Levee

5'

5'

6'

Levee Flood Level

Ground

38'

Figure 5-21a: 

Schematic of typical 

earthen levee
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5 MAKING SCHOOLS SAFE FROM FLOODING

and operations are critical for adequate performance. Floodwalls that 

protect buildings that provide essential services usually are designed for 

the 0.2-percent-annual-chance flood (500-year) and have freeboard to 

increase the factor of safety. If a protected school is intended to remain 

operational during long-duration flooding, vehicle access to the site and 

pedestrian access to the building are required.

5.3.4 Elevation Considerations

The selection of the appropriate method of elevating a school building 

in a SFHA depends on many factors, including type of flood zone, costs, 

level of safety and property protection determined as acceptable risk, and 

others. Another consideration is the elevation of the lowest floor relative 

to the flood elevation. Table 5-1 in Section 5.1.6.4 summarizes the elevation requirements in ASCE 24. Given the importance of schools, elevation 

of the lowest floor to or above the 0.2-percent-annual-chance flood (500-

year) elevation should be considered the minimum. Various methods 

used to elevate buildings in flood hazard areas are described below. 

In A zones, the minimum requirement is that the lowest floor (including 

the basement) be at or above the DFE (plus freeboard, if desired or required). For building elevation methods other than 

fill, the area under elevated buildings in A zones 

may be used only for limited purposes. parking, 

building access, and limited storage (crawlspaces 

are treated as enclosures, see below). Facility planners and designers are cautioned that enclosures 

below the DFE are exposed to flooding and the 

contents will be damaged or destroyed by floodwaters. The walls surrounding an enclosure must 

have flood openings that are intended to equalize 

Figure 5-21b: 

Schematic of typical 

permanent floodwall

4' 3'

Floodwall Flood Level Ground

Floodwall

Footing

 “Lowest floor” is the floor of the lowest 

enclosed area (including the basement). 

An unfinished or flood-resistant enclosure, 

usable solely for parking of vehicles, building access, or storage in an area other 

than a basement, is not the lowest floor, 

provided the enclosure is built in compliance with applicable requirements. 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-51

interior and exterior water levels in changing flood conditions, to prevent differential hydrostatic pressures leading to structural damage. The 

enclosed area must not contain utilities and equipment (including ductwork) below the required elevation. 

In V zones, the minimum requirement is that the 

elevation of the bottom of the lowest horizontal 

structural member of the lowest floor (including 

basement) be at or above the DFE (plus freeboard, 

where required). (Use of structural fill to achieve 

elevation is not allowed and dry floodproofing is 

not allowed.) Given the importance of schools, elevation to or above the 0.2-percent-annual-chance 

flood (500-year) elevation is appropriate and 

strongly recommended. The V zone requirements 

are recommended in Coastal A Zones.

The area under elevated buildings in V zones may 

be used only for parking, building access, and limited storage. The areas may be open or enclosed by 

lattice walls or screening. If areas are enclosed by 

solid walls, the walls must be specifically designed 

to break away under certain flood loads to allow 

the free passage of floodwaters under the building. 

Breakaway walls are non-load-bearing walls, i.e., 

they do not provide structural support for the building. They must be 

designed and constructed to collapse under the pressure of floodwaters 

in such a way that the supporting foundation system and the structure 

are not affected. 

Coastal communities along the Atlantic and Gulf coasts are subject 

to storm surge flooding generated by hurricanes and tropical storms. 

Depending on a number of variables, storm surge flood depths may 

significantly exceed the BFE. In addition, waves are likely to be higher 

than predicted for the base flood, and will occur farther inland in areas where significant wave action during the base flood is not expected. 

Application of the minimum requirements related to elevation of the 

lowest floor and foundation design does not result in flood resistance 

for such extreme conditions. Foundations for schools in areas subject to 

storm surge should be designed to elevate the building so that the lowest 

horizontal structural members are higher than the minimum required 

elevation. Additional elevation not only reduces damage that results 

from lower probability events, but the cost of Federal flood insurance is 

usually lower. Facility planners and designers should plan to use the lowest elevated floor for non-critical uses that, even if exposed to flooding 

Communities that participate in the NFIP 

require that a registered professional 

engineer or architect develop or review 

the structural design, specifications, and 

plans, and certify that the dry floodproofing 

design and methods of construction to 

be used are in accordance with accepted 

standards of practice. The standards of 

practice require that the building, together 

with attendant utility and sanitary facilities, 

be designed so that it is watertight, with 

walls substantially impermeable to the 

passage of water and with structural components having the capability of resisting 

hydrostatic and hydrodynamic loads and 

effects of buoyancy associated with the 

design flood event.
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5 MAKING SCHOOLS SAFE FROM FLOODING

more severe than the design flood, will not impair critical functioning 

during post-flood recovery.

Storm surge flooding and waves can cause scour and erosion, even at locations that are some distance from the shoreline. Foundation designs 

for schools in coastal communities should account for some erosion and 

local scour of supporting soil during low-probability surge events. Storm 

surge flooding can also produce large quantities of floating debris, even 

at locations that are some distance from the shoreline. Debris can damage nonstructural building components and, in some cases of prolonged 

battering, can lead to structural failure. Foundation designs for schools 

in coastal communities should account for debris loads. This is especially 

important where damage to other buildings in the area may generate additional debris, thereby increasing the loads. 

Notes on continuous load path: In coastal communities and other areas 

exposed to high winds, designers should pay special attention to the 

entire roof-to-foundation load path when designing and specifying connections. Connections must be capable of withstanding simultaneous 

wind and flood forces. Poorly connected buildings may fail or float off 

foundations when floodwaters and waves are higher than the design 

flood elevation. Corrosion-resistant connections are critical for the longterm integrity of the structure, and should be inspected and maintained 

regularly. 

Slab-on-grade foundation on structural fill: This is considered to be the 

safest method to elevate a building in many flood hazard areas, except 

those where waves and high velocity flows may cause erosion. Consequently, this foundation type is not allowed in V zones. Structural fill can be 

placed so that even if water rises up to the DFE, the building (see Figure 

5-22) and building access would still be protected from flooding. The fill 

must be designed to minimize adverse impacts, such as increasing flood 

elevations on adjacent properties, increasing erosive velocities, and causing local drainage problems. To ensure stability, especially as floodwaters 

recede and the soils drain, fill must be designed for the anticipated water 

depths and duration. A geotechnical engineer or soil scientist may need 

to examine underlying soils to determine if the bearing capacity is sufficient to carry the added weight of fill, or if consolidation over time may 

occur. In addition, the effects of long-term compaction of the fill should 

be considered, and may prompt additional elevation as a factor of safety. 

The horizontal extent of the fill, away from the foundation, should be 

designed to facilitate access by emergency vehicles, with a minimum 25-

foot width recommended. Engineered concrete slabs supported by piers 

should have sufficient resistance to erosion and scour if designed for anticipated flood conditions. Designers are cautioned to avoid excavating 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-53

a basement into fill without added structural protection (and certification that the design meets the requirements for dry floodproofing), due 

to the potential for significant hydrostatic loads and uplift on basement 

floors.

Stem wall foundations: Stem wall foundations have a continuous perimeter grade beam, or perimeter foundation wall, that is backfilled with 

compacted earth to the underside of the concrete floor slab (see Figure 

5-23). This foundation type is not allowed in V zones. Stem wall foundations are designed to come in contact with floodwaters on the exterior. 

They are more stable than perimeter wall foundations with crawlspaces, 

but could experience structural damage if undermined by local scour 

and erosion. Designs must account for anticipated debris and ice impacts, 

and incorporate methods and materials to minimize impact damage.

Columns or shear wall foundations (open foundations): Open foundations 

consist of vertical load-bearing members (columns, piers, pilings, and 

shear walls) without solid walls connecting the vertical members. Open 

foundations minimize changes to the floodplain and local drainage patterns, and the area under the building can be used for parking or student 

activities (see Figure 5-24). The design of the vertical members must also 

account for hydrodynamic loads and debris and ice impact loads. Flood 

loads on shear walls are reduced if they are oriented parallel to the anticipated direction of flow. If erodible soils are present and local scour 

is likely, both conditions must be taken into account when determining 

embedment depth of the vertical foundation members. Depending on 

the total height of the elevated school, the design may need to take into 

consideration the increased exposure to wind and uplift, particularly 

where loads are expected from breaking waves. 

Figure 5-22: 

High school in 

Bloomsburg, PA, 

elevated on fill
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5 MAKING SCHOOLS SAFE FROM FLOODING

Figure 5-23:

A stemwall foundation 

elevates the Marion 

T. Academy above 

the flood level in 

Wilmington, DE. 

Figure 5-24: 

School elevated on 

columns 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-55

In V zones, buildings must be elevated using open foundations, which 

consist of vertical load-bearing members (columns, piers, pilings, and 

shear walls) without solid walls connecting the vertical members. The design of the vertical members must also account for hydrodynamic loads 

and debris impact loads. Flood loads on shear walls are reduced if the 

walls are oriented parallel to the anticipated direction of flow. Erodible 

soils may be present and local scour may occur; both must be accounted 

for in designs by extending the load-bearing members and foundation 

elements well below the expected scour depth. 

Continuous perimeter walls (enclosed foundations with crawlspace): Unlike stem wall foundations, continuous perimeter walls enclose an open 

area or crawlspace (see Figure 5-25). The perimeter walls must have flood 

openings, also called vents) that are intended to equalize interior and 

exterior water levels automatically during periods of rising and falling 

flood levels, to prevent differential hydrostatic pressures that could lead 

to structural damage. Flood openings may be engineered and certified 

for the required performance, or they must meet prescriptive requirements (notably, the opening must provide at least 1 square inch of net 

open area for each square foot of area enclosed). Perimeter wall design 

must also account for hydrodynamic loads, and debris and ice impact 

loads. Enclosed crawlspaces must not contain utilities or equipment 

Figure 5-25:

Typical crawlspace with 

flood openings

Footing Depth per

Building Code

Exterior Grade

Interior Grade

Flood Opening

Crawl

Space

Joist Exterior

Wall

12"
5-56 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

5 MAKING SCHOOLS SAFE FROM FLOODING

(including ductwork) below the required elevation. Designers must 

provide adequate under-floor ventilation and subsurface drainage to 

minimize moisture problems after flooding. This foundation type is not 

allowed in V zones.

Pier supports for manufactured and portable units: Manufactured buildings and portable units must be elevated above the DFE (plus freeboard, 

if required). Pier supports must account for hydrodynamic loads and 

debris and ice impact loads, and units must be anchored to resist wind 

loads. Although written specifically for manufactured housing units, 

FEMA P-85, Protecting Manufactured Homes from Floods and Other Hazards. 

A Multi-Hazard Foundation and Installation Guide (2009b), has useful information that is applicable to portable units. 

5.3.5 Dry Floodproofing Considerations

Dry floodproofing involves a combination of design and special features 

that are intended both to prevent water infiltration and resist flood forces. 

It involves structural reinforcement so that exterior walls are sufficiently 

robust to withstand the loads described in Section 5.1.3 (hydrostatic pressure, hydrodynamic loads, wave loads, and debris impact loads). Exterior 

walls must also be designed to prevent infiltration and seepage of water, 

whether through the wall itself or through any openings, including where 

utility lines penetrate the envelope. Floodproofing techniques are considered to be permanent measures if they are always in place and do not 

require occupants to take any specific actions to be effective. An alternative to reinforcement of a structure’s walls involves 

the installation of a permanent floodwall that is 

slightly offset from the exterior of the structure, but 

designed to be integral to the foundation. 

According to the model building codes and the 

NFIP regulations, non-residential buildings and 

nonresidential portions of mixed-use buildings in 

A zones may be dry floodproofed. Although floodproofing is allowed, careful consideration must be 

given to the possible risks to occupants and additional physical damage before a decision is made to 

construct a new school using floodproofing methods. Dry floodproofing is not allowed in V zones. 

All flood protection measures are designed for certain flood conditions. Considering the possibility 

that the design conditions can be exceeded (i.e., water can rise higher than the protective structures), 

Communities that participate in the NFIP 

require that a registered professional 

engineer or architect develop or review 

the structural design, specifications, and 

plans, and certify that the dry floodproofing 

design and methods of construction to 

be used are in accordance with accepted 

standards of practice. The standards of 

practice require that the building, together 

with attendant utility and sanitary facilities, 

be designed so that it is watertight, with 

walls substantially impermeable to the 

passage of water and with structural components having the capability of resisting 

hydrostatic and hydrodynamic loads and 

effects of buoyancy associated with the 

design flood event.
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-57

a dry floodproofed building may, in such circumstances, sustain catastrophic damage. As a general rule, dry floodproofing is a poor choice 

for new schools when avoidance of the floodplain or elevation methods 

to raise the building above the flood level can be applied. Floodproofing 

may be acceptable for retrofitting existing buildings under very limited 

circumstances (see Section 5.4.5). 

A number of dry floodproofing limitations and requirements are specified in ASCE 24:

n Dry floodproofing is limited to areas where flood velocities at the site 

are less than or equal to 5 feet per second.

n If human intervention is required to deploy measures to protect 

doors and windows, the flood warning time shall be a minimum of 

12 hours unless the community operates a flood warning system and 

implements a notification procedure that provides sufficient time to 

undertake these measures.

n At least one door satisfying building code requirements for an exit 

door or primary means of escape must be provided above the level 

of protection.

n An emergency plan, approved by the community and posted in at 

least two conspicuous locations, is required in floodproofed buildings; the plan is intended to specify the location of panels and 

hardware, methods of installation, conditions that activate deployment, a schedule for routine maintenance of any aspect that may 

deteriorate over time, and periodic practices and drills. 

Windows, doors, and other openings that are below the flood level used 

for dry floodproofing design present significant potential failure points. 

They must be specially designed units (see Figure 5-26) or be fitted with 

gasketed, mountable panels that are designed for the anticipated flood 

conditions and loads. Generally speaking, protecting window and door 

openings from water more than a few feet deep is difficult. The framing 

and connections must be specifically designed for these protective measures, or water pressure may cause window and door frames to separate 

from the building. 

Dry floodproofing is required to extend to 1 or 2 

feet above the DFE (see Table 5-1). For the purpose 

of obtaining NFIP flood insurance, the floodproofing must extend at least 1 foot above the BFE, or 

the premiums will be very high. A higher level of 

protection is recommended. 

Although dry floodproofing of facilities in 

Coastal A Zones is allowed by the NFIP, 

designs that comply with the IBC must take 

into consideration the additional forces 

associated with wave impacts, which may 

make dry floodproofing a less feasible 

alternative. 
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5 MAKING SCHOOLS SAFE FROM FLOODING

Floodproofing techniques are considered to be permanent measures if 

they are always in place and do not require any specific human intervening action to be effective. Use of contingent floodproofing measures 

that require installation or activation, such as 

window shields or inflatable barriers, may significantly reduce the certainty that floodproofing 

will be effective. Rigorous adherence to a periodic maintenance plan is critical to ensure proper 

functioning. If these measures are used to protect 

schools, the school’s management must have a formal, written plan, and the people responsible for 

implementing the measures must be informed and trained. These measures also depend on the timeliness and credibility of the warning. In 

addition, floodproofing devices often rely on flexible seals that require 

periodic maintenance and that, over time, may deteriorate and become 

ineffective. Therefore, a maintenance plan must be developed and a rigorous annual inspection and training must be conducted. 

Safety of occupants is a significant concern with dry floodproofed buildings, because failure or overtopping of the floodproofing barriers is likely 

to cause catastrophic structural damage. When human intervention is required for deploying of barriers, those responsible for implementing the 

measures remain at risk while at the school, even if a credible warning 

system is in place, because of the many uncertainties associated with predicting the onset of flood conditions. 

Dry floodproofed schools must never be 

considered safe for occupancy during 

periods of high water; floodproofing measures are intended only to reduce physical 

damage. 

Figure 5-26: 

Specially designed 

panels are mounted to 

block doors, windows, 

and other openings 

to keep water from 

entering the building. 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-59

5.3.6 Flood Damage-Resistant Materials

All structural materials, nonstructural materials, and connectors that are 

used below certain elevations (see Table 5-1) are to be flood resistant. 

Flood-damage-resistant materials have sufficient strength, rigidity, and 

durability to adequately resist flood loads and damage due to saturation. 

They are building materials that are capable of withstanding direct and 

prolonged contact with floodwaters without sustaining any damage that 

requires more than cosmetic repair. As defined in ASCE 24, the term 

“prolonged contact” means partial or total inundation by floodwaters for 

72 hours for non-coastal areas (fresh water) or 12 hours for coastal areas. 

In general, materials that are exposed to floodwaters are to be capable 

of resisting damage, deterioration, corrosion, or decay. Typical construction materials range from highly resistant to not at all resistant to water 

damage. FEMA NFIP Technical Bulletin 2 contains tables with building 

materials, classified based on flood resistance (Table 5-2).

Table 5-2: Classes of flood damage-resistant materials

NFIP Class Class Description Acceptable

5

Highly resistant to floodwater1 damage, including damage caused by moving water.2 These 

materials can survive wetting and drying and may be successfully cleaned after a flood to render them 

free of most harmful pollutants.3 Materials in this class are permitted for partially enclosed or outside uses 

with essentially unmitigated flood exposure.

4

Resistant to floodwater1 damage from wetting and drying, but less durable when exposed to 

moving water.2 These materials can survive wetting and drying and may be successfully cleaned after 

a flood to render them free of most harmful pollutants.3

 Materials in this class may be exposed to and/or 

submerged in floodwaters in interior spaces and do not require special waterproofing protection.

Unacceptable

3

Resistant to clean water4 damage, but not floodwater damage. Materials in this class may be 

submerged in clean water during periods of flooding. These materials can survive wetting and drying, but 

may not be able to be successfully cleaned after floods to render them free of most3

 harmful pollutants.

2

Not resistant to clean water4 damage. Materials in this class are used in predominantly dry spaces 

that may be subject to occasional water vapor and/or slight seepage. These materials cannot survive the 

wetting and drying associated with floods.

1

Not resistant to clean water4 damage or moisture damage. Materials in this class are used in spaces 

with conditions of complete dryness. These materials cannot survive the wetting and drying associated 

with floods.

Notes:

1. Floodwater is assumed to be considered “black” water; black water contains pollutants such as sewage, chemicals, heavy 

metals, or other toxic substances that are potentially hazardous to humans. 

2. Moving water is defined as water moving at low velocities of 5 feet per second (fps) or less. Water moving at velocities greater 

than 5 fps may cause structural damage to building materials. 

3. Some materials can be successfully cleaned of most of the pollutants typically found in floodwater. However, some individual 

pollutants such as heating oil can be extremely difficult to remove from uncoated concrete. These materials are flood damageresistant except when exposed to individual pollutants that cannot be successfully cleaned.

4. Clean water includes potable water as well as “gray” water; gray water is wastewater collected from normal uses (laundry, 

bathing, food preparation, etc.).

SOURCE. FLOOD DAMAGE-RESISTANT MATERIALS REQUIREMENTS, FEMA-TB-2, AUGUST 2008.
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5 MAKING SCHOOLS SAFE FROM FLOODING

In coastal areas, airborne salt aerosols and inundation with saline water increase the potential for 

corrosion of some metals. Structural steel and other metal components that are exposed to corrosive 

environments should be stainless steel or hotdipped galvanized after fabrication.

In areas away from the coast, exposed structural 

steel should be primed, coated, plated, or otherwise protected against corrosion. Secondary components such as angles, 

bars, straps, and anchoring devices, as well as other metal components 

(plates, connectors, screws, bolts, nails angles, bars, straps, and the like) 

should be stainless steel or hot-dipped galvanized after fabrication. 

Concrete and masonry that are designed and constructed in compliance 

with applicable standards are generally considered to be flood resistant. 

However, masonry facings are undesirable finishes unless extra anchoring is added to prevent separation (see Figure 5-27). Wood and timber 

members exposed to floodwaters should be naturally decay-resistant species, or should be pressure treated with appropriate preservatives. 

Figure 5-27:

Brick facing separated from masonry wall 

(Hurricane Katrina, 2005)

FEMA NFIP Technical Bulletin 2, 

Flood Damage-Resistant Materials 

Requirements (2008), provides some additional information. Many types of materials 

and application products are classified by 

degrees of resistance to flood. 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-61

5.3.7 Access Roads

Roads and entrances leading to schools should be designed to provide 

safe access at all times, to minimize impacts on flood hazard areas, to 

minimize damage to the road itself, and to minimize exposing vehicles to 

dangerous situations. Even if the school is elevated and protected from 

flood damage, when access is impaired, functionality is also impaired. 

Facility planners and designers should take the following factors into 

consideration.

Safety factors: Although a school’s access road off the primary surface 

street may not be required to carry regular traffic like other streets, a 

floodprone road always presents a degree of risk to public safety. To 

minimize those risks, some State or local regulatory authorities require 

that access roads be designed so that the driving surface is at the DFE, 

or no more than 1 to 2 feet below the DFE. At a minimum, a school’s 

access road should be at least as high as the adjacent public road, so 

that the same level of access is provided during conditions of flooding. 

To maximize evacuation safety, two separate access roads to different 

feeder roads are recommended. In some circumstances, especially longduration flooding where a school is built on fill, access roads designed to 

be above flood levels would help the school to continue its operations. 

Floodplain impacts: Engineering analyses may be required to determine 

the effects on flood elevations and flow patterns if large volumes of fill 

are required to elevate a road to minimize or eliminate flooding above 

the driving surface.

Drainage structure and road surface design: The placement of multiple 

drainage culverts, even if not needed for local drainage, can facilitate the passage of floodwaters and minimize the potential for a road 

embankment to act as a dam. Alternatively, an access road can be designed with a low section over which rising floodwater can flow without 

washing out the roadbed. Embankments should be designed to remain 

stable during high water and as waters recede. They should be sloped 

and protected to resist erosion and scour. Similarly, the surface and 

shoulders of roads that are intended to flood should be designed to resist erosion. The increased resistance to erosion may be accomplished 

by increasing the thickness of the road base.

5.3.8 Utility Installations

Utilities associated with new schools in flood hazard areas must be protected either by elevation or special designs and installation measures. 

Utilities subject to this provision include all systems, equipment, and fixtures, including mechanical, electrical, plumbing, heating, ventilating, 
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and air-conditioning. Potable water systems (wellheads and distribution 

lines) and wastewater collection lines are addressed in Section 5.3.9. 

Utility systems and equipment are best protected when elevated above 

the DFE (plus freeboard, if required). Equipment that is required for 

emergency functioning during or immediately after an event, such 

as emergency generators and fuel tanks, is best 

installed well above the DFE. In some cases, equipment can be located inside protective floodproofed 

enclosures, although if flooding exceeds the design 

level of the enclosure, the equipment would be adversely affected (see Figure 5-28). Designers should 

pay particular attention to under-floor utilities and 

ductwork to ensure that they are properly elevated. 

Plumbing conduits, water supply lines, gas lines, 

and electric cables that must extend below the 

DFE should be located, anchored, and protected to resist the effects of 

flooding. Equipment that is outside of an elevated building also must be 

elevated:

n In A zones, equipment may be affixed to raised support structures or 

mounted on platforms that are attached to or cantilevered from the 

primary structure. 

Figure 5-28:

Equipment room with 

watertight door

SOURCE: PRESRAY 

CORPORATION

For more information on utility installations, see FEMA 348, Protecting Building 

Utilities from Flood Damage: Principles 

and Practices for the Design and 

Construction of Resistant Building Utility 

Systems (1999).
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-63

n In V zones and Coastal A Zones, equipment may be affixed to raised 

support structures designed for the flood conditions (waves, debris 

impact, erosion, and scour) or mounted on platforms that are attached to or cantilevered from the primary structure. If an enclosure 

is constructed under the elevated building, the designer must take 

care that utilities and attendant equipment are not mounted on or 

do not pass through walls that are intended to break away. 

Although it is difficult to achieve, the model building codes and NFIP 

regulations provide an alternative that allows equipment to be located 

below the DFE. This alternative requires that such equipment be designed, constructed, and installed to prevent floodwaters from entering 

or accumulating within the components during flood events. 

5.3.9 Potable Water and Wastewater Systems

New installations of potable water systems and wastewater collection 

systems are required to resist flood damage, including damage associated with infiltration of floodwaters and discharge of effluent. Health 

concerns arise when water supply systems are exposed to floodwaters. 

Contamination from flooded sewage systems poses additional health and 

environmental risks. Onsite water supply wellheads should be located on 

land elevated from the surrounding landscape to allow contaminated 

surface water and rainfall-runoff to drain away. Well casings should extend above the DFE, and casings should be sealed with a tight-fitting, 

floodproof, and vermin-proof well cap. The space between the well casing and the side of the well must be sealed to minimize infiltration and 

contamination by surface waters. 

Sewer collection lines should be located and designed to avoid infiltration and backup due to rising floodwaters. Devices designed to prevent 

backup are available and are recommended to provide an added measure of protection. 

Onsite sewage systems usually are not used as the primary sewage disposal systems for new schools. However, facility planners and designers 

should consider a backup onsite system if a school’s functionality can be 

impaired when the public system is affected by flooding. Local or State 

health departments may impose constraints that limit or prevent locating 

septic fields in floodplain soils or within a mapped flood hazard area. If 

allowed, septic fields should be located on the highest available ground 

to minimize inundation and damage by floodwaters. An alternative to a 

septic field is installation of a holding tank that is sized to contain wastewater for a period of time, perhaps a few days, while the municipal system 

is out of service.
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5.3.10 Storage Tank Installations

Aboveground and underground storage tanks located in flood hazard areas must be designed to resist flotation, collapse, and lateral movement. 

ASCE 24 specifies that aboveground tanks be elevated or constructed, 

installed, and anchored to resist at least 1.5 times the potential buoyant and other flood forces under design flood conditions, assuming the 

tanks are empty. Similarly, underground tanks are to be anchored to resist at least 1.5 times the potential buoyant forces under design flood 

conditions, assuming the tanks are empty. In all cases, designers are cautioned to address hydrodynamic loads and debris impact loads that may 

affect tanks that are exposed to floodwaters. Vents and fill openings or 

cleanouts should be elevated above the DFE or designed to prevent the 

inflow of floodwaters or outflow of the contents of tanks. 

5.3.11 Accessory Structures

Many school campuses have multiple buildings. All buildings, including 

those that are accessory to the primary building, must be designed and 

constructed in full compliance with floodplain management regulations. 

Portable classrooms are not accessory structures. Bleachers are allowed 

provided they are anchored to resist flood forces.

In flood hazard areas designated as A zones, some minor accessory structures used only for storage and parking need not fully comply, but may 

be “wet floodproofed” using techniques that allow them to flood while 

minimizing damage. Accessory structures must be anchored to resist flotation, collapse, and lateral movement. Flood-resistant materials must be 

used and utilities must be elevated above the DFE (plus freeboard, if required). If fully enclosed by walls, the walls must have flood openings to 

allow the free inflow and outflow of floodwaters to minimize the hydrostatic loads. Because wet floodproofed accessory buildings are designed 

to flood, school staff must be aware that contents will be damaged. 

Accessory structures on school campuses that are located in V zones must 

be elevated and otherwise comply with the applicable requirements. 

5.4 Risk Reduction for Existing Schools

5.4.1 Introduction

Section 5.2 describes damage that can be sustained by schools that 

already are located in flood hazard areas. The vulnerability of 

these facilities can be reduced if they can be made more resistant 

to flooding. School districts may take such action when flood hazards 

are identified and there is a desire to undertake risk reduction measures 
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-65

proactively. Interest may be prompted by a flood or 

by the requirement to address flood resistance as 

part of a proposed addition or substantial improvement of the existing building. The checklist in 

Section 5.6 includes some questions and guidance 

intended to help identify building characteristics 

of importance when considering risk reduction 

measures for existing facilities. 

Work performed on existing school buildings and 

outbuildings is subject to codes and regulations, 

and the appropriate regulatory authority with jurisdiction should be consulted. With respect to 

reducing flood risks, work generally falls into the 

categories described in the following subsections.

5.4.2 Site Modifications

Modifying the site of an existing school property that is subject to flooding 

requires careful examination by an experienced professional engineer. 

Determining the suitability of a specific measure requires a complex evaluation of many factors, including the nature of flooding and the nature 

of the site. The first part of Table 5-3 in Section 5.6 identifies elements 

that influence the choice of mitigation measures applicable to existing 

sites. Some flood characteristics may make it infeasible to apply site modification measures to existing schools (e.g., depths greater than 3 to 4 

feet, very high velocities, insufficient warning because of flash flooding 

or rapid rate of rise, and very long duration). In Coastal A Zones, wave 

conditions must be accounted for in design of site modifications. Such 

modifications are not allowed in V zones. 

A common problem with all site modifications is the matter of access. 

Depending on the topography of the site, construction of barriers to 

floodwaters may require special access points. Access points may be protected with manually installed stop-logs or designed gates that drop in, 

slide, or float into place. Whether activated by automatic systems or manually operated, access protection requires sufficient warning time.

Other significant constraining factors include 

poor soils and insufficient land area, which can 

make site modifications either infeasible or very 

costly. For any type of barrier, rainfall that collects on the dry side must be accounted for in the 

design, whether through adequately sized stormwater storage basins set aside for this purpose, or 

School districts should be aware of the 

importance of flood insurance coverage 

for structures that are located in the flood 

hazard areas shown on NFIP maps. If not 

insured for flood peril, the amount of flood 

insurance that should have been in place 

will be deducted from any Federal disaster 

assistance payment that would otherwise 

have been made available. A district may 

have to absorb up to $1 million in un-reimbursable flood losses per building, because 

the NFIP offers $500,000 in building coverage and $500,000 in contents coverage for 

nonresidential buildings (coverage limits as 

of early 2010). 

Schools protected by local berms, levees, 

and floodwalls should never be occupied 

during flood conditions. The consequences 

of failure or flood levels overtopping these 

measures can be catastrophic and create 

high-risk conditions. 
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5 MAKING SCHOOLS SAFE FROM FLOODING

by providing large-capacity pumps to move collected drainage to the 

water side of the barrier.

Each of the site modification measures described below has limitations, 

including the fact that floods larger than the design flood will exceed the 

level of protection.

Site regrading (berm): Regrading of the site, or the construction of an 

earthen berm, may provide adequate protection for situations in which a 

school is exposed to relatively shallow flooding, and sufficient land area 

is available.

Earthen levee:  Earthen levees are engineered structures that are designed to keep water away from certain areas and buildings. Hydraulic 

analyses and geotechnical investigations are required to determine their 

feasibility and effectiveness. The use of earthen levees to protect existing schools is constrained by the availability of land (levees have a large 

“footprint” and require large land areas), cost (including availability of 

suitable fill material and long-term maintenance), and access difficulties. 

Locating levees and floodwalls within a designated floodway is generally 

not allowed. Rapid onset flooding makes it impractical to design a flood 

levee with access points that require installation of a closure system. Additionally, high velocity flows can cause erosion and reduce the stability 

of earthen levees. 

Permanent floodwall: Floodwalls are freestanding, permanent engineered 

structures designed to prevent encroachment of floodwaters. Typically, 

a floodwall is located some distance from a building, so that structural 

modification of the existing building is not required. Depending on the 

topography of the site, floodwalls may protect only the low side (in which 

case they must “tie” into high ground) or completely surround a site 

(which may affect access because special closure structures are required 

and must be installed before the onset of flooding, see Figure 5-29).

Mobilized floodwall: This category of flood protection measures includes 

fully engineered flood protection structures that have permanent features (foundation and vertical supports) and features that require human 

intervention when a flood is predicted (horizontal components called 

planks or stop-logs). Mobilized floodwalls have been used to protect entire sites, or to tie into permanent floodwalls or high ground. Because of 

the manpower and time required for proper placement, these measures 

are better suited to conditions that allow long warning times.
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-67

Figure 5-29: 

A masonry floodwall 

with multiple engineered 

openings in Fargo, ND, 

during flooding in 2001

SOURCE: FLOOD CONTROL 

AMERICA, LLC

5.4.3 Additions

Model building codes generally treat additions as new construction, and 

thus additions to schools in flood hazard areas should be elevated or dry 

floodproofed to minimize exposure to flooding. However, full compliance with the code and NFIP requirements is only required if an addition 

is a substantial improvement (i.e., the cost of the addition plus all other 

costs associated with the work equal or exceed 50 percent of the market 

value of the building, see Section 5.1.6.1 and Section 5.1.6.2). Designers 

are cautioned that even the existing buildings may be required to comply 

with the flood-resistant provisions of the code or local ordinances, if the 

addition is structurally connected to the existing building and is determined to be a substantial improvement. 

Section 5.3.4 outlines foundation methods used to elevate buildings that 

also are applicable to additions. Elevation of an addition on fill may not 

be feasible unless structural fill can be placed adjacent to the existing 

building. Utility service equipment for additions must meet the requirements for new installations (see Section 5.3.8).

If an evaluation determines that dry floodproofing is appropriate, additions may be floodproofed (see Section 5.3.5). To provide adequate 

protection for the addition, floodproofing must be applied to all exterior walls and the wall adjoining the existing building. Openings, 

including doors between the addition and existing building, must also 

be protected.
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With respect to code compliance and designing 

additions to resist flood damage, one of the more 

significant issues to be considered is ease of access. 

If the lowest floor of the existing school building is 

below the DFE, steps, ramps, or elevators will be required for the transition to the new addition. Some 

jurisdictions may contemplate allowing variances to the requirement that additions be elevated. 

However, because alternative means of access are 

available, such as ramps and elevators it would be difficult for an applicant to demonstrate that there are unique limitations of the site and 

hardship that make compliance with the regulation infeasible. 

5.4.4 Repairs, Renovations, and Upgrades

Every school considered for upgrades and renovations, or being repaired 

after substantial damage from any cause, must be examined for structural integrity and stability to determine compatibility with structural 

modifications that may be required to achieve acceptable performance. 

When an existing school is located in a flood hazard area, that examination should include consideration of measures to improve resistance to 

flood damage and to reduce risks. 

The model building codes and the NFIP regulations require that work 

constituting “substantial improvement” of an existing building be in compliance with the flood-resistant provisions of the code. Non-substantial 

improvements should take into account measures to reduce future flood 

damage, such as those described in Section 5.3, emergency measures 

(see Section 5.4.10), and wet floodproofing measures that allow water to enter the building to avoid 

structural damage. 

Compliance with flood-resistant provisions means 

that the existing building must be elevated or dry 

floodproofed. Both options can be difficult for 

existing schools, given the typical use, size, and 

complexity of many school buildings. Retrofit dry 

floodproofing (described in Section 5.4.5) is generally feasible only in areas where flood depths of 

3 feet or less are expected, provided an assessment 

by a qualified design professional determines that 

the building is capable of resisting the anticipated 

loads, or can be modified to provide that level of 

performance. 

For more information on additions and substantial improvements, see FEMA P-758, 

Substantial Improvement/Substantial 

Damage Desk Reference (2010) and 

FEMA 213, Answers to Questions About 

Substantially Damaged Buildings (1991).

Additional information on rehabilitation 

of existing buildings is provided in: Flood 

Proofing: How to Evaluate Your Options 

(USACE, 1993), FEMA 102, Floodproofing 

Non-Residential Structures (1986), FEMA 

TB-3, Floodproofing—Requirements 

and Certification (1993), and FEMA 259, 

Engineering Principles and Practices for 

Retrofitting Flood Prone Buildings (2001). 

Although written primarily for homes, this 

last reference contains very detailed 

checklists and worksheets that can be 

modified. They also provide some guidance for evaluating the costs and benefits 

of various measures.
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-69

Elevating an existing building presents an entirely different set of challenges and also requires detailed structural engineering analyses. It 

involves the same equipment and methods used to move other types of 

buildings; expert building movers have successfully moved large, heavy, 

and complex buildings, sometimes by segmenting them. A building that 

is elevated in-place must meet the same performance standards set for 

new construction.

5.4.5 Retrofit Dry Floodproofing

Modification of an existing building may be required or desired in order 

to address exposure to design flood conditions. Modifications that may 

be considered include construction of a reinforced supplementary wall, 

measures to counter buoyancy (especially if there is below-grade space), 

installation of special watertight door and window 

barriers and watertight seals around the points of 

entry of utility lines. The details of structural investigations and structural design of such protection 

measures are beyond the scope of this manual. 

Retrofit dry floodproofing is difficult to apply to existing buildings and, 

in general, is limited to situations where the anticipated flood depths are 

only 3 or 4 feet. Because of the tremendous flood loads that may be exerted on a building not originally designed to keep water out, detailed 

structural engineering evaluations are required to determine whether an 

existing building can be dry floodproofed. The following elements must 

be examined:

n The strength of the structural system

n Whether non-load bearing walls can resist anticipated flood loads; 

secondary walls can be constructed immediately adjacent to existing 

walls, with a waterproof membrane, to provide adequate strength

n The effects of hydrostatic pressures on the walls and floors of belowgrade areas

n Effective means to install watertight doors and windows, or mountable panels

n Protection where utilities enter the building

n Methods to address seepage, especially where long-duration flooding is anticipated

n Whether there is sufficient time for deployment of measures that require human intervention, given the availability of official warnings 

of predicted flood conditions

“Dry floodproofing” refers to measures 

and methods to render a building envelope 

substantially impermeable to floodwater. 
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5 MAKING SCHOOLS SAFE FROM FLOODING

Application of waterproofing products or membranes directly to exterior walls may minimize infiltration of water; although there are concerns 

with durability and limitations on use (this measure is most effective 

for shallow, short-duration flooding). Some protection can be achieved 

using emergency measures that are not designed to be integral to the 

building (see Section 5.4.10). 

5.4.6 Utility Installations

Some features of utility systems in existing schools that are prone to 

flooding may need to be modified to reduce damage. The effectiveness 

of such measures depends not only on the nature of the flooding, but 

the type of service and the degree of exposure. Table 5-3 in Section 5.6 

lists some questions to help school facility planners and designers examine risk reduction measures. 

Even if a school building is unlikely to sustain extensive structural damage from flooding, significant recovery costs and delayed re-occupancy 

may result if utility systems are damaged. The damage reduction measures described below can be applied, whether undertaken as part of 

large-scale retrofits of existing buildings or as separate projects.

Relocate from below-grade areas:  The most vulnerable utility installations are those located below grade, and the most effective protection 

measure is to relocate them to higher floors or platforms that are at 

least 2 feet above the DFE. The complexity of rerouting pipes, conduits, 

ductwork, electrical service, lines, and connections will depend on building- and site-specific factors.

Elevate components: Whether located inside or outside of the building, 

some components of utility systems can be elevated in place on platforms, including electric transformers, communication switch boxes, 

water heaters, air-conditioning compressors, generators, furnaces, boilers, and heat pumps (see Figure 5-30). 

Anchor tanks and raise openings: Existing tanks can be elevated or anchored, as described in Section 5.3.10. If anchored below the DFE, tank 

inlets, vents, fill pipes, and openings should be elevated above the DFE, 

or fitted with covers designed to prevent the inflow of floodwaters or 

outflow of the tank’s contents.

Protect components:  If utility components cannot be elevated, it may 

be feasible to construct watertight enclosures, or enclosures with watertight seals that require human intervention to install when flooding is 

predicted.
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DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-71

Figure 5-30: 

Utility component elevated above flood 

level

Elevate control equipment:  Control panels, gas meters, and electrical 

panels can be elevated, even if the equipment they service cannot be 

protected.

Separate electrical controls: Where areas within an existing school are 

floodprone, separation of control panels and electrical feeders will facilitate shutdown before floodwaters arrive, and help protect workers 

during cleanup.

Protect against electrical surges: Current fluctuations and service interruptions are common in areas affected by flooding. Equipment and 

sensitive electrical components can be protected by installing surge protection and uninterruptible power supplies.

Connections for portable generators:  Prewired portable generator connections allow for quick, failure-free connection and disconnection of 

the generators when needed for continued functionality.
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5.4.7 Potable Water and Wastewater Systems

All plumbing fixtures connected to the potable water system may become 

weak points in the system if they allow floodwaters to contaminate the 

system. Relocating the fixtures and services that require plumbing to elevated floors and removing the fixtures that are below the DFE provides 

protection. Wellheads can be sealed with watertight casings or protected 

within sealed enclosures.

Wastewater system components become sources of contamination during floods. Rising floodwaters may force untreated sewage to backup 

through toilets. Specially designed devices that prevent backflow can be 

installed, or restrooms below the DFE can be provided with overhead 

piping that may require specially designed pumps to operate properly. 

Septic tanks can be sealed and anchored. 

5.4.8 Other Damage Reduction Measures

A number of steps can be taken to make existing facilities in flood hazard 

areas more resistant to flood damage, which also facilitates rapid recovery, cleanup, and re-occupancy. Whether these measures can be used for 

a specific school depends, in part, on the characteristics of the flood hazard and the characteristics of the building itself. School facility planners 

and designers should consider the following measures:

n Rehabilitate and retrofit the building envelope with openings specifically designed to allow floodwaters to flow in and out to minimize 

hydrostatic pressure on walls (called wet floodproofing). Although it 

allows water to enter the building, this measure minimizes the likelihood of major structural damage. Walls that enclose interior spaces 

should also be retrofitted with openings. Note that this approach is 

not acceptable when full compliance is required, such as when an 

existing building is substantially improved or when a new addition is 

constructed. 

n Replace interior walls that have cavities with flood-resistant construction or removable panels to facilitate cleanup and drying.

n Abandon the use of below-grade areas (basements) and fill them in 

to prevent structural damage.

n Permanently relocate high-value or sensitive functions that are often 

found on the ground floor of schools (e.g., offices, school records, 

libraries, and computer laboratories) to higher floors or elevated 

additions.

n Install backflow devices in sewer lines.
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DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-73

n Preplan actions to move damageable furniture and high-value contents from the lower floors to higher floors when a flood warning is 

issued.

n Replace wall, flooring, and finish materials with flood-resistant materials. Concrete floors with a sealed, polished, or terrazzo finish have 

few maintenance requirements, but tend to be slippery when wet.

n Use epoxy or other impervious paints on concrete and other permeable surfaces to minimize contamination. 

n Install separate electric circuits and ground fault circuit interrupter 

protection in areas that will flood. Emergency measures should be 

provided so that electrical service can be shut down to avoid electrocution hazards.

n Relocate chemicals to storage areas not subject to flooding.

5.4.9 Drainage Improvements

Although drainage improvements will not alleviate flooding caused by 

rising waters that surround a building, such improvements will help to 

minimize water damage that can be caused by heavy rainfall. The flow of 

rainfall-runoff depends on the shape of the land around a school building and the adequacy of the drainage system. Rainfall-runoff will either 

follow pre-determined paths (above-ground gutters and swales and underground pipes) to intended outfalls, or it may overwhelm the drainage 

system and enter buildings. Significant damage can be attributed to undersized, poorly planned, or inadequately maintained drainage systems. 

Local grading ordinances and stormwater management regulations often require drainage systems to handle the runoff that is associated with 

the 10-year frequency, 24-hour rainfall event. When heavier rainfall occurs or storms last longer, those systems are expected to overflow or back 

up. As a result, sometimes storm runoff can enter buildings, creating the 

same types of damage that are caused by general conditions of flooding. 

Existing school campuses should be evaluated to determine whether the 

drainage system is adequate and whether significant damage could occur 

if the design is overwhelmed by heavier runoff volumes. In particular, close 

attention should be given to the large paved areas that are often close to 

school buildings. All of the rain that falls on impervious paved surfaces 

runs off. If paved areas are sloped towards buildings, the likelihood of 

damage to the building is increased. How the landscaping is maintained 

and whether drainage paths, gutters, and storm drain grates are kept clear 

of debris will also affect the efficiency of the drainage system.
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5.4.10 Emergency Measures

Emergency response to flooding is outside the scope of this manual. 

However, feasible emergency measures may provide some protection. 

The following description pertains only to emergency measures that have 

been used to reduce flood damage to older buildings that are already 

located in flood hazard areas. They may not provide protection to occupants and they can experience a high frequency of failure depending on 

human factors related to deployment. These measures do not achieve 

compliance with building and life-safety codes for new construction. 

Emergency barriers are measures of last resort, and should be used only 

when a credible flood warning with adequate lead time is available and 

dependable. These measures have varying degrees of success, depending on the available manpower, skill required for installation, long-term 

maintenance of materials and equipment, suitability for site-specific 

flood conditions, and amount of advanced warning. Complete evacuation of protected buildings is appropriate, because emergency measures 

do not provide adequate protection for the safety of occupants. 

Sandbag walls: Unless emergency placement is planned well in advance 

or under the direction of trained personnel, most sandbag barriers are 

not constructed in accordance with proper practices, leading to leakage and failures. Because of the intensive work effort and length of time 

required for protection even from relatively shallow water, sandbag walls 

are not a reliable protection measure. To be effective, sandbags and sand 

should be stockpiled and checked regularly to ensure that sandbags have 

not deteriorated. Sandbags have some other drawbacks, including high 

disposal costs and their tendency to absorb pollutants from contaminated floodwaters, which necessitates disposal as hazardous waste.

Water- or sand-filled barriers: A number of vendors make barriers that 

can be assembled with relative ease and filled with water or sand (see 

Figure 5-31). The barriers must be specifically sized for the site. Training 

and annual drills are important so that personnel know how to place 

and deploy the barriers. Proper storage, including cleaning after deployment, is necessary to protect the materials over long periods of time.

Panels for doors: For shallow and short-duration flooding, panels of sturdy 

material can be made to fit doorways to minimize the entry of floodwaters, although failure is common. Effectiveness is increased significantly 

if a flexible gasket or sealant is provided, and the mounting hardware is 

designed to apply even pressure. Personnel must know where the materials are stored and be trained in their deployment. A number of vendors 

make special doors for permanent installation and drop-in panels or barriers that are designed to be watertight.
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-75

Figure 5-31: 

Gravel-filled containers 

form a barrier to protect 

the University of Iowa 

(2008)

5.5 Schools as Emergency Shelters and Safe 

Rooms

E mergency managers regularly identify schools to serve as shortterm and/or long-term community shelters. They are attractive 

sites for community shelters because they are designed for many 

people, with kitchen facilities, restroom and shower facilities, and 

open space gymnasiums, cafeterias, and wide corridors for cots and 

general gathering.

New schools that are intended to be used as emergency shelters are 

appropriately designed as essential or critical facilities that warrant a 

higher degree of protection than other schools. If located in or adjacent to flood hazard areas, it is appropriate to 

provide protection for the building and utility 

systems to at least the 0.2-percent-annual-chance 

(500-year) flood level or, at a minimum, 2 to 3 

feet above the DFE. 

Starting with the 2009 edition of the IBC, the 

design and construction of community shelters are governed by 

both the provisions of the code and ICC 500, ICC/NSSA Standard on 

the Design and Construction of Storm Shelters (2008). In addition to requirements related to resistance to high winds, ICC 500 specifies 

Additional guidance on hazard-resistant 

shelters can be found in FEMA 361, 

Design and Construction Guidance for 

Community Safe Rooms (2008).
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that the minimum lowest floor elevation is the higher of four elevations: (1) the 0.2-percent-annual-chance flood (500-year) level; 

(2) the 1-percent-annual-chance flood level plus 2 feet (BFE + 2 feet); 

(3) 2 feet above the highest recorded flood elevation (if the area is not 

in a mapped SFHA); or (4) the maximum inundation elevation associated with a Category 5 hurricane event in an area subject to storm 

surge inundation. 

The highest level of protection for sheltering is set forth in FEMA 361, 

Design and Construction Guidance for Community Safe Rooms (2008). The 

elevation criteria specified in FEMA 361 are equivalent to the criteria in 

the ICC 500 with one notable exception: to be designated a safe room, 

some special flood hazard areas must be avoided because the flood risk 

is too great. FEMA 361 guidance, which applies when the protection 

levels for safe rooms are desired, must be followed when Federal funding is being used to construct the safe room portion of a school. When 

designing an area of a school to provide the “near absolute” protection from tornadoes and hurricanes that are afforded by safe rooms, 

other criteria with respect to travel time to the safe room, the population to be protected, and the location of the safe room with respect 

to mapped flood hazard areas must all be considered. For additional 

information, please refer to the FEMA safe room policy MRR-2-09-1, 

Hazard Mitigation Assistance for Safe Rooms (2009c).

School districts and designers should also consider the following if 

schools are intended to be used as emergency shelters or safe rooms:

n Wastewater service must be functional during flooding conditions. 

n Emergency power service must be provided.

n Dry-ground access is important even if flooding exceeds design 

levels. 

n Mechanical and electrical equipment supporting the safe room or 

shelter must also be elevated as identified in FEMA 361 or ICC 500, 

respectively
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5.6 Checklist for Vulnerability of Floodprone Sites 

and Schools

T he Checklist for Building Vulnerability of Floodprone Schools 

(Table 5-3) is a tool that can be used to help assess site-specific 

flood hazards and building vulnerability. The checklist is useful 

during site selection, preliminary design of a new building, or when considering rehabilitation of an existing school. In addition to examining 

building design issues that affect vulnerability, the checklist also helps 

users to examine the functionality of the critical systems upon which 

most schools depend. The checklist is organized into separate sections, 

so that each section can be assigned to a subject expert for greater accuracy of the examination. The results should be integrated into a master 

vulnerability assessment to guide the design process and the choice of 

appropriate mitigation measures.

Table 5-3: Checklist for building vulnerability of floodprone schools

Vulnerability Sections Guidance Observations

Site Conditions

Is the site located near a body of water 

(with or without a mapped flood hazard 

area)? 

Is the site in a flood hazard area shown 

on the community’s map (FIRM or other 

adopted map)? If so, what is the flood 

zone?

Is the site affected by a regulatory 

floodway?

All bodies of water are subject to flooding, but 

not all have been designated as a floodplain on 

FIRMs. 

Flood hazard maps usually are available for 

review in local planning and permit offices. 

Electronic versions of the FIRMs may be available 

online at www.fema.gov. Paper maps may be 

ordered by calling (800) 358-9616.

Development in floodways, where floodwaters 

typically are faster and deeper, must be 

supported by engineering analyses that 

demonstrate no rise in flood levels.

Is the site located in a storm surge 

inundation zone (or tsunami inundation 

area)?

In coastal communities, even sites at some 

distance inland from the shoreline may be 

exposed to extreme storm surge flooding. Storm 

surge maps may be available at State or local 

emergency management offices.
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Table 5-3: Checklist for building vulnerability of floodprone schools

Vulnerability Sections Guidance Observations

Site Conditions

What is the DFE (or does an analysis 

have to be done to determine the DFE)? 

What is the minimum protection level 

required by regulatory authorities?

Does the FIS or other study have 

information about the 500-year flood 

hazard area?

Has FEMA issued post-disaster advisory 

flood elevations and maps?

What are the expected depths of flooding 

at the site (determined using flood 

elevations and ground elevations)?

Reference the FIS for flood profiles and data 

tables. Site-specific analyses should be 

performed by qualified engineers. 

Check with regulatory authorities to determine the 

required level of protection.

If a major flood event has affected the community, 

FEMA may have issued new flood hazard 

information, especially if areas not shown on 

the FIRMs have been affected. Sometimes 

these maps are adopted and replace the FIRMs; 

sometimes the new data are advisory only.

Has the site been affected by past flood 

events? What is the flood of record? 

Records of actual flooding augment studies 

that predict flooding, especially if historic 

events resulted in deeper or more widespread 

flooding. Information may be available from 

local planning, emergency management, and 

public works agencies, or State agencies, the 

U.S. Army Corps of Engineers, or the Natural 

Resources Conservation Service.

The flood of record is often a lower probability 

event (with higher flood elevations) than the 100-

year flood.

What is the expected velocity of 

floodwaters on the site?

Velocity is a factor in computing loads associated 

with hydrodynamic forces, including drag on 

building surfaces. Approximations of velocity may 

be interpolated from data in the FIS Floodway 

Data Table if the waterway was studied using 

detailed methods, application of approximation 

methods based on continuity, local observations 

and sources, or site-specific studies. 

Are waves expected to affect the site? Waves can exert considerable dynamic forces 

on buildings and contribute to erosion and scour. 

Wind-driven waves occur in areas subject to 

coastal flooding and where unobstructed winds 

affect wide floodplains (large lakes and major 

rivers). Standing waves may occur in riverine 

floodplains where high velocities are present.

Is there information on how quickly 

floodwaters may affect the site?

What is the expected duration of 

flooding?

Warning time is a key factor in the safe and 

orderly evacuation of critical facilities. Certain 

protective measures may require adequate 

warning so that actions can be taken by skilled 

personnel.

Duration has bearing on the stability of earthen 

fills, access to a site and emergency response, 

and durability of materials that come into contact 

with water. Records of actual flooding are the 

best indicator of duration as most floodplain 

analyses do not examine duration. 
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Table 5-3: Checklist for building vulnerability of floodprone schools

Vulnerability Sections Guidance Observations

Site Conditions

Is there a history of flood-related debris 

problems or erosion on the site?

Site design should account for deposition of 

debris and sediment, as well as the potential for 

erosion-related movement of the shoreline or 

waterway. Buildings exposed to debris impact 

or undermining by scour and erosion should be 

designed to account for these conditions. 

Is the site within an area predicted to 

flood if a levee or floodwall fails or is 

overtopped? 

Is the site in an area predicted to be 

inundated if an upstream dam were to 

fail?

Flood protection works may be distant from 

sites and not readily observable. Although a 

low probability event, failure or overtopping can 

cause unexpected and catastrophic damage 

because the protected lands are not regulated 

as flood hazard areas.

The effects of an upstream dam failure are 

not shown on the FIRMs or most flood hazard 

maps prepared locally. Although dam failure 

generally is considered an unlikely event, the 

potential threat should be evaluated due to the 

catastrophic consequences. (Note: Owners of 

certain dams should have emergency action 

plans geared toward notification and evacuation 

of vulnerable populations and critical facilities.)

Does the surrounding topography 

contribute to the flooding at the site? Is 

there a history of local surface drainage 

problems due to inadequate site 

drainage?

If areas with poor local drainage and frequent 

flooding cannot be avoided, filling, regrading, 

and installation of storm drainage facilities may 

be required.

Given the nature of anticipated flooding 

and soils, is scour around and under the 

foundation likely?

Scour-prone sites should be avoided, in part due 

to likely long-term maintenance requirements. 

Flooding that is high velocity or accompanied by 

waves is more likely to cause scour, especially 

on fills, or where local soils are unconsolidated 

and subject to erosion.

Has water from other sources entered 

the building (i.e., high groundwater, water 

main breaks, sewer backup, etc.)? Is 

there a history of water intrusion through 

floor slabs or well-floor connections? 

Are there underground utility systems 

or areaways that can contribute to 

basement flooding? Are there stormwater 

sewer manholes upslope of window 

areas or openings that allow local 

drainage to enter the basement/lower 

floor areas? 

These questions pertain to existing facilities that 

may be impaired by water from sources other 

than the primary source of flooding. The entire 

building envelope, including below-grade areas, 

should be examined to identify potential water 

damage.
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Table 5-3: Checklist for building vulnerability of floodprone schools

Vulnerability Sections Guidance Observations

Site Conditions

Is at least one access road to the site/

building passable during flood events? 

Are at-grade parking lots located in 

floodprone areas?

Are below-grade parking areas 

susceptible to flooding?

Access is increasingly important as the 

duration of flooding increases. For the safety of 

occupants, most critical facilities should not be 

occupied during flood events.

Areas where vehicles could be affected should 

have signage to warn users, including bus 

drivers, of the risk. Emergency response plans 

should include notification of car owners.

Architectural

Are any critical building functions 

occupying space that is below the 

elevation of the 500-year flood or the 

DFE?

Can critical functions be relocated to 

upper levels that are above predicted flood 

elevations?

If critical functions cannot be relocated, is 

floodproofing feasible?

If critical functions must continue during 

a flood event, have power, supplies, and 

access issues been addressed?

New critical facilities built in flood hazard areas 

should not have any functions occupying 

floodprone spaces (other than parking, building 

access, and limited storage). 

Existing facilities in floodplains should be 

examined carefully to identify the best options for 

protecting functionality and the structure itself.

Have critical contents (files, computers, 

servers, equipment, research, and data) 

been located on levels of the facility above 

the flood elevations? 

Are critical records maintained offsite?

For existing facilities that are already located 

in flood hazard areas, the nature of the facility 

may require continued use of floodprone space. 

However, the potential for flooding should be 

recognized and steps taken to minimize loss of 

expensive equipment and irreplaceable data. If 

critical contents cannot be permanently located 

on higher floors, a flood response plan should 

take into account the time and attention needed 

to move such contents safely.

Structural Systems

What is the construction type and the 

foundation type and what is the load 

bearing capacity?

Has the foundation been designed to 

resist hydrostatic and hydrodynamic 

flood loads?

If siting in a floodplain is unavoidable, new 

facilities are to be designed to account for all 

loads and load combinations, including flood 

loads. 
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Table 5-3: Checklist for building vulnerability of floodprone schools

Vulnerability Sections Guidance Observations

Structural Systems

If the building has below-grade areas 

(basements), are the lower floor slabs 

subject to cracking and uplift?

Below-grade spaces and their contents are 

most vulnerable to flooding and local drainage 

problems. Rapid pump out of below-grade 

spaces can unbalance forces if the surrounding 

soil is saturated, leading to structural failure. 

If below-grade spaces are intended to be dry 

floodproofed, the design must account for 

buoyant forces.

Building spaces below the design flood level 

can be dry floodproofed, although it must be 

recognized that higher flood levels will overtop 

the protection measures and may result in 

severe damage. Dry floodproofing creates large 

unbalanced forces that can jeopardize walls and 

foundations that are not designed to resist the 

hydrostatic and hydrodynamic loads.

Are any portions of the building below 

the DFE?

Has the building been damaged in 

previous floods?

For existing buildings, it is important to 

determine which portions are vulnerable in 

order to evaluate floodproofing options. If flood 

depths are expected to exceed 2 or 3 feet, dry 

floodproofing may not be feasible. Alternatives 

include modifying the use of floodprone areas.

If the building is elevated on a 

crawlspace or on an open foundation, are 

there any enclosed areas?

New buildings may have enclosures below 

the flood elevation, provided the use of the 

enclosures is limited (crawlspace, parking, 

building access, and limited storage). In addition, 

the enclosures must have flood openings to 

automatically allow for inflow and outflow of 

floodwaters to minimize differential hydrostatic 

pressure. 

Existing buildings that are elevated and have 

enclosures below the flood elevation can be 

retrofit with flood openings.

For an existing building with high-value 

uses below the flood elevation, is the 

building suitable for elevation-in-place, or 

can it be relocated to higher ground? 

Elevating a building provides better protection 

than dry floodproofing. Depending on the type 

and soundness of the foundation, even large 

buildings can be elevated on a new foundation 

or moved to a site outside of the floodplain.

Building Envelope

Are there existing floodproofing 

measures in place below the expected 

flood elevation? What is the nature of 

these measures and what condition are 

they in? Is there an annual inspection 

and maintenance plan?

Is there an “action plan” to implement 

floodproofing measures when flooding 

is predicted? Do the building operators/

occupants know what to do when a flood 

warning is issued?

Floodproofing measures are only as good as 

the design and their condition, especially if 

many years have passed since initial installation. 

Floodproofing measures that require human 

intervention are entirely dependent on the 

adequacy of advance warning, and the 

availability and ability of personnel to properly 

install the measures. 
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Table 5-3: Checklist for building vulnerability of floodprone schools

Vulnerability Sections Guidance Observations

Building Envelope

For existing buildings, what types of 

openings penetrate the building envelope 

below the 500-year flood elevation or 

the DFE (doors, windows, cracks, vent 

openings, plumbing fixtures, floor drains, 

etc.)?

For dry floodproofing to be effective, every 

opening must be identified and measures 

taken to permanently seal or to prepare special 

barriers to resist infiltration. Sewage backflow 

can enter through unprotected plumbing fixtures.

Are flood-resistant materials used for 

structural and nonstructural components 

and finishes below the 500-year elevation 

or the DFE?

Flood-resistant materials are capable of 

withstanding direct and prolonged contact with 

floodwaters without sustaining damage that 

requires more than cosmetic repair. Contact is 

considered to be prolonged if it is 72 hours or 

longer in freshwater flooding areas, or 12 hours 

or longer in areas subject to coastal flooding.

Utility Systems

Is the potable water supply for the facility 

protected from flooding? If served by a 

well, is the wellhead protected? 

Operators of critical facilities that depend on 

fresh water for continued functionality should 

learn about the vulnerability of the local water 

supply system, and the system’s plans for 

recovery of service in the event of a flood.

Is the wastewater service for the building 

protected from flooding? 

Are any manholes below the DFE? Is 

infiltration of floodwaters into sewer 

lines a problem? If the site is served 

by an onsite system that is located in a 

floodprone area, have backflow valves 

been installed?

Most waste lines exit buildings at the lowest 

elevation. Even buildings that are outside of the 

floodplain can be affected by sewage backups 

during floods. 

Are there any aboveground or 

underground tanks on the site in flood 

hazard areas? Are they installed and 

anchored to resist flotation during the 

design flood? Are tank openings and 

vents elevated above the 500-year 

elevation or the DFE, or otherwise 

protected to prevent entry of floodwater 

or exit of product during a flood event?

Dislodged tanks become floating debris that 

pose special hazards during recovery. Lost 

product causes environmental damage. 

Functionality may be impaired if tanks for 

heating fuel, propane, or fuel for emergency 

generators are lost or damaged. 

Mechanical Systems

Are air handlers, HVAC systems, 

ductwork, and other mechanical 

equipment and systems located above 

the 500-year elevation or the DFE? 

Are the vents and inlets located above 

flood level, or sealed to prevent entry of 

floodwater?

In existing buildings, utility equipment that is 

critical for functionality should be relocated to 

higher floors or into elevated additions. 

Plumbing and Gas Systems

Are plumbing fixtures and gas-fired 

equipment (meters, pilot-light devices/

burners, etc.) located above the 500-year 

elevation or the DFE?

In existing buildings, utility equipment that is 

critical for functionality should be relocated to 

higher floors or into elevated additions.
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Table 5-3: Checklist for building vulnerability of floodprone schools

Vulnerability Sections Guidance Observations

Plumbing and Gas Systems

Is plumbing and gas piping that extends 

below flood levels installed to minimize 

damage?

Piping that is exposed could be impacted by 

debris.

Electrical Systems

Are electrical systems, including backup 

power generators, panels, and primary 

service equipment, located above the 

500-year elevation or the DFE? 

Are pieces of electrical stand-by 

equipment and generators equipped with 

circuits to turn off power?

Are the switches and wiring required for 

safety (minimal lighting, door openers) 

located below the flood level designed 

for use in damp locations?

In existing buildings, utility equipment that is 

critical for functionality should be relocated to 

higher floors or into elevated additions.

Fire Alarm Systems

Is the fire alarm system located above the 

500-year elevation or the DFE?

In existing buildings, utility equipment that is 

critical for functionality should be relocated to 

higher floors or into elevated additions.

Communications and IT Systems

Are the communication/IT systems 

located above the 500-year elevation or 

the DFE? 

5.7 References and Sources of Additional 

Information

American Society of Civil Engineers (ASCE), 2005a. Flood Resistant Design 

and Construction, ASCE/SEI 24-05, Structural Engineering Institute, 

Reston, VA.

ASCE, 2005b. Minimum Design Loads for Buildings and Other Structures, 

ASCE 7-05, Structural Engineering Institute, Reston, VA.

ASCE, 2010. Minimum Design Loads for Buildings and Other Structures, 

2010 Edition, ASCE 7-10, Structural Engineering Institute, Reston, VA.

Association of State Floodplain Managers, Inc. (ASFPM), 2004. Floodplain 

Management 2003. State and Local Programs, Madison, WI.
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Executive Order 11988. Floodplain Management, May 24, 1977, 42 F.R. 

26951.

Federal Emergency Management Agency (FEMA), 1986. Floodproofing 

Non-Residential Structures, FEMA 102, Washington, DC, May 1986.

FEMA, 1991. Answers to Questions about Substantially Damaged Buildings,

FEMA 213, Washington, DC, May 1991.

FEMA, 1999. Protecting Building Utilities From Flood Damage. Principles and 

Practices for the Design and Construction of Flood Resistant Building Utility 

Systems, FEMA 348, Washington, DC, November 1999. 

FEMA, 2000. Coastal Construction Manual, FEMA 55CD (3rd Edition), 

Washington, DC.

FEMA, 2001. Engineering Principles and Practices for Retrofitting Flood-prone 

Residential Buildings, FEMA 259, Washington, DC, June 2001.

FEMA, 2008. Design and Construction Guidance for Community Shelters,

FEMA 361, Washington, DC, November 2008. 

FEMA, 2009a. Answers to Questions about the National Flood Insurance 

Program, FEMA F-084, September 2009. 

FEMA, 2009b. Protecting Manufactured Homes from Floods and Other 

Hazards. A Multi-Hazard Foundation and Installation Guide, FEMA P-85, 

Washington, DC.

FEMA 2009c. Hazard Mitigation Assistance for Safe Rooms, FEMA 

Mitigation Interim Policy, MRR-2-09-1, April 30, 2009

FEMA, 2010. Substantial Improvement/Substantial Damage Desk Reference, 

FEMA P-758, Washington, DC.

FEMA and American Red Cross (ARC), 1992. Repairing Your Flooded 

Home, FEMA 234/ARC 4477. Washington, DC. (available at http://www.

redcross.org, local Red Cross chapters, and FEMA).

FEMA publications may be obtained at no cost by calling (800)480-2520, 

faxing a request to (240) 699-2520, or downloaded from the library/publications sections online at http://www.fema.gov. 
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DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-85

Federal Emergency Management Agency, NFIP Technical Bulletins.

n User’s Guide to Technical Bulletins, FIA-TB-0, March 2009. 

n Openings in Foundation Walls and Walls of Enclosures, FEMA-TB-1, 

August 2008.

n Flood Damage-Resistant Materials Requirements, FEMA-TB-2, August 

2008.

n Non-Residential Floodproofing—Requirements and Certification, FIATB-3, April 1993. 

n Elevator Installation, FIA-TB-4, April 1993. 

n Free-of-Obstruction Requirements, FEMA-TB-5, August 2008. 

n Below-Grade Parking Requirements, FIA-TB-6, April 1993.

n Wet Floodproofing Requirements, FIA-TB-7, December 1993.

n Corrosion Protection for Metal Connectors in Coastal Areas, FIA-TB-8, 1996.

n Design and Construction Guidance for Breakaway Walls Below Elevated 

Coastal Buildings, FEMA-TB-9, August 2008.

n Ensuring That Structures Built on Fill In or Near Special Flood Hazard 

Areas Are Reasonably Safe From Flooding, FIA-TB-10, 2001. 

n Crawlspace Construction for Buildings Located in Special Flood Hazard 

Areas, FIA-TB-11, 2001.

International Code Council (ICC), 2008. ICC/NSSA Standard on the 

Design and Construction of Storm Shelters, ICC 500, August 2008, Country 

Club Hills, IL.

ICC and FEMA, 2008, Reducing Flood Losses Through the International 

Codes, Meeting the Requirements of the National Flood Insurance Program

(2006 I-Codes), Country Club Hills, IL.

ICC, 2009. International Building Code 2009, Country Club Hills, IL.

National Academy of Sciences, 1977. Methodology for Calculating Wave 

Action Effects Associated with Storm Surges, Washington, DC.

National Fire Protection Association (NFPA), 2009. Building Construction 

and Safety Code, NFPA 5000, Quincy, MA.

U.S. Army Corps of Engineers (USACE), 1993. Flood Proofing – How To 

Evaluate Your Options, National Flood Proofing Committee, Washington, DC, 

July 1993.
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USACE, 1995. Flood Proofing Regulations, EP 1165-2-314, Washington, DC.

USACE, 1996. Flood Proofing Techniques, Programs, and References, Washington, DC.

USACE, 1998. Flood Proofing Performance – Successes & Failures, Washington, DC.

U.S. Environmental Protection Agency (EPA), 2001, Mold Remediation 

in Schools and Commercial Buildings, EPA 402-K-01-001, Washington, DC.

Organizations and Agencies

Federal Emergency Management Agency: 10 regional offices (www.fema.

gov) can be contacted for advice and guidance on NFIP mapping and 

regulations. 

NFIP State Coordinating offices help local governments to meet their 

floodplain management obligations and may provide technical advice 

to others; the offices are listed by the Association of State Floodplain 

Managers, Inc., (www.floods.org/stcoor.htm). 

State departments of education or agencies that coordinate State funding and guidelines for schools may have State-specific requirements.

U.S. Army Corps of Engineers. District offices offer Flood Plain 

Management Services (www.nap.usace.army.mil/cenap-op/regulatory/

districts.html). 

5.8 Glossary of Flood Protection Terms

Advisory Base Flood Elevation. Flood elevation that is determined by a 

reassessment of base flood elevations conducted after significant flood 

events.

Base flood. The flood having a 1-percent chance of being equaled or 

exceeded in any given yea, commonly referred to as the “100-year flood.” 

The base flood is the national standard used by the NFIP and all Federal 

agencies for the purpose of regulating development.

Base flood elevation (BFE). The height of the base (1-percent or 100-year) 

flood in relation to a specified datum, usually the National Geodetic Vertical Datum of 1929 or the North American Vertical Datum of 1988. 
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Coastal High Hazard Area. An area of special flood hazard extending from 

offshore to the inland limit of a primary frontal dune along an open 

coast and any other area subject to high velocity wave action from storms. 

Coastal high hazard areas also are referred to as “V Zones” and are designated on Flood Insurance Rate Maps (FIRMs) as zones VE or V1-30.

Design flood. The greater of the following two flood events. (1) the base 

flood, affecting those areas identified as special flood hazard areas on 

a community’s FIRM; or (2) the flood corresponding to the area designated as a flood hazard area on a community’s flood hazard map or 

otherwise legally designated.

Design flood elevation (DFE). The elevation of the design flood, including wave height, relative to the datum specified on a community’s flood 

hazard map.

Dry floodproofing. Any combination of structural and nonstructural additions, changes, or adjustments to structures, or combinations thereof 

that eliminate or reduce the potential for flood damage by resisting flood 

loads, sealing walls, and closing openings to keep water from entering a 

building. 

Federal Emergency Management Agency (FEMA). The Federal agency that, 

among other functions, administers the National Flood Insurance Program (NFIP).

Flood Insurance Rate Map (FIRM). The official map of a community on 

which FEMA has delineated both special flood hazard areas (SFHA) and 

flood zones. Some FIRMs include base flood elevations, 500-year floodplain boundaries, and regulatory floodway boundaries.

Flood Insurance Study (FIS). An engineering study performed by FEMA to 

identify flood hazard areas, flood insurance risk zones, and other flood 

data in a community; used in the development of the FIRM.

Flood profile. A graph of computed flood elevations at points located 

along a riverine waterway. Flood profiles typically are available for waterways that have BFEs shown on FIRMs, and are found in FISs. 

Flood zone. A designation for areas that are shown on Flood Insurance 

Rate Maps.

Floodplain. Any land area, including a watercourse and the land adjacent 

to it, that is susceptible to being inundated by water from any source.
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Floodplain management regulations. Zoning ordinances, subdivision regulations, building codes, health regulations, or special-purpose ordinances 

that set flood-resistant standards for construction and development.

Floodway. The channel of a river or other watercouse and the adjacent 

land areas that must be reserved in order to discharge the base flood 

without cumulatively increasing the water surface elevation by more than 

a designated height. 

Freeboard. A factor of safety, usually expressed in feet above a flood level, 

for purposes of floodplain management. Freeboard also compensates 

for unknown factors that could contribute to flood heights greater than 

the height calculated for a selected frequency flood and floodway conditions, such as wave action, blockage of bridge openings, and the effects 

of upland urbanization. A freeboard of from 1 to 3 feet is often applied 

to critical facilities. 

Human intervention. Actions that must be taken by one or more persons 

in order for a building to be floodproofed prior to the onset of flooding. 

Hydrodynamic load. The load imposed by water flowing against and 

around an object or structure, including the impact of debris and waves. 

Hydrostatic load. The load (pressure) imposed on an object or structure 

by a standing or slowly moving mass of water; the deeper the water, the 

greater the hydrostatic load or pressure. 

Limit of Moderate Wave Action. The inland limit of the area affected by 

waves greater than 1.5 feet.

Lowest floor. The lowest floor of the lowest enclosed area (including a 

basement) of a building. An unfinished or flood-resistant enclosure, usable solely for parking of vehicles, building access, or storage, in an area 

other than a basement, is not considered a building’s lowest floor, provided that the enclosure is compliant with flood-resistant requirements.

National Flood Insurance Program (NFIP). The Federal program, administered by FEMA, that identifies flood-prone areas nationwide and makes 

flood insurance available for properties in communities that participate 

in the program. 

Scour. Removal of soil or fill material from the channel cross-section or 

land surface by the flow of floodwaters.
MAKING SCHOOLS SAFE FROM FLOODING 5 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 5-89

Sheetflow. Rainfall-runoff that flows over relatively flat land without concentrating into streams or channels.

Special flood hazard area. An area delineated on a FIRM as being subject 

to inundation by the base flood and designated as Zone A, AE, A1–A30, 

AR, AO, AH, A99, V, VE, or V1–V30. 

Stillwater elevation. The elevation that the surface of coastal floodwaters 

would assume in the absence of waves, referenced to a datum.

Substantial damage. Damage of any origin sustained by a structure, whereby the cost of restoring the structure to its pre-damage condition equals 

or exceeds 50 percent of the market value of the structure before the 

damage occurred (or smaller percentage if established by the authority 

having jurisdiction). Structures that are determined to be substantially 

damaged are considered to be substantial improvements, regardless of 

the actual repair work performed. 

Substantial improvement. Any reconstruction, rehabilitation, addition, or 

other improvement of a structure, the cost of which equals or exceeds 

50 percent of the market value of the structure (or smaller percentage 

if established by the authority having jurisdiction) before the start of the 

improvement. 

Wave runup. Rush of wave water running up a slope or structure.

Wet floodproofing. Permanent or contingent measures applied to a building and/or its contents to minimize flood damage by modifying interior 

finishes, removing damageable items from lower areas, and allowing water into the building.

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-1

Making Schools Safe 6From High Winds

6.1 General Design Considerations

Wind with sufficient speed to cause damage to weak schools can 

occur anywhere in the United States and its territories.1

 Even 

a well-designed, constructed, and maintained school may be 

damaged by a wind event much stronger than one the building was designed for. However, except for tornado damage, this scenario is a rare 

occurrence. Rather, most damage occurs because various building elements have limited wind resistance due to inadequate design, poor 

installation, or material deterioration. Although the magnitude and 

frequency of strong windstorms vary by locale, all schools should be designed, constructed, and maintained to minimize wind damage (other 

than that associated with tornadoes—see Section 6.5). 

1 The U.S. territories include American Samoa, Guam, Northern Mariana Islands, Puerto Rico, 

and the U.S. Virgin Islands. ASCE 7 provides basic wind speed criteria for all but Northern 

Mariana Islands.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-1: 

Large portions of the roof 

coverings blew off of this 

school. Estimated wind 

speed: Approximately 

125 to 130 miles per 

hour (mph).2

 Hurricane 

Katrina (Louisiana, 2005)

This chapter discusses structural, building envelope, and nonstructural 

building systems, and illustrates various types of wind-induced damage 

that affect them. Numerous examples of best practices pertaining to new 

and existing schools are presented as recommended design guidelines. 

Incorporating those practices applicable to specific projects will result in 

greater wind-resistance reliability and will, therefore, decrease expenditures for repair of wind-damaged facilities, provide enhanced protection 

for occupants, and avoid school disruption (see Figure 6-1).2

The recommendations presented in this design guide are based on field 

observation research conducted on a large number of schools that were 

struck by hurricanes.3

 The recommendations are also based on numerous investigations of other types of critical and non-critical facilities 

exposed to hurricanes, tornadoes, and straight-line winds, and on literature review. Some of the schools were exposed to extremely high wind 

speeds, while others experienced moderate speeds. 

2 Estimated speeds given in this chapter are for a 3-second gust at a 33-foot elevation for 

Exposure C (as defined in ASCE 7). In most instances, the buildings for which estimated 

speeds are given are located in Exposure B. Hence, in most cases, the actual wind speed 

was less than the wind speed given for Exposure C conditions. For example, a 130-mph 

Exposure C speed is equivalent to 110 mph in Exposure B.

3 The research on the schools was conducted by a team from Texas Tech University (Hurricane 

Hugo, Charleston, SC, 1989), a team under the auspices of the Wind Engineering Research 

Council—now known as the American Association for Wind Engineering (Hurricane Andrew, 

South Florida, 1992), and teams deployed by FEMA (Hurricane Marilyn, U.S. Virgin Islands, 

1995; Typhoon Paka, Guam, 1997; Hurricane Charley, Port Charlotte, FL, 2004; Hurricane 

Frances, east coast of Florida, 2004; Hurricane Ivan, Pensacola, FL, 2004; Hurricane Katrina, 

Louisiana and Mississippi, 2005; and Hurricane Ike, Texas, 2008).
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-3

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.1.1 Nature of High Winds

A variety of windstorm types occur in different areas of the United States. 

The characteristics of the types of storms that can affect the site should 

be considered by the design team. The primary storm types are straightline winds, down-slope winds, thunderstorms, downbursts, northeasters 

(nor’easters), hurricanes, and tornadoes. For information on these 

storm types, refer to Section 3.1.1 in FEMA 543.4

Of all the storm types, hurricanes have the greatest potential for devastating a large geographical area and, hence, affect the greatest number of 

people. See Figure 6-2 for hurricane-prone regions.

4 Available at the FEMA Web site. See www.fema.gov/library/viewRecord.do?id=2441

ASCE 7-10 Boundary Between Hurricane

and Non-Hurricane Winds

ASCE 7-05 Hurricane-Prone Region

Special Wind Region

Figure 6-2: Hurricane-prone regions and special wind regions

SOURCE: ADAPTED FROM ASCE 7-10
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

6.1.2 Probability of Occurrence 

When designing a school, design professionals should consider the following types of winds:

Routine winds: In many locations, winds with low to moderate speeds occur daily. Damage is not expected to occur during these events.

Stronger winds: At a given site, stronger winds (i.e., winds with a speed in 

the range of 70- to 80-mph peak gust, measured at 33 feet in Exposure 

C—refer to Section 6.1.3) may occur from several times a year to only 

once a year or even less frequently. This is the threshold at which damage 

normally begins to occur to building elements that have limited wind resistance due to problems associated with inadequate design, insufficient 

strength, poor installation, or material deterioration. 

Design level winds: At a given site, the probability of design level winds occurring in a given year is very low. Schools exposed to design level events 

and events that are somewhat in excess of design level should experience 

little, if any, damage. Actual storm history, however, has shown that design level storms frequently cause extensive building envelope damage. 

Structural damage also occurs, but less frequently. Damage incurred in 

design level events is typically associated with inadequate design, poor 

installation, or material deterioration. The exceptions are wind-driven 

water infiltration and wind-borne debris (missiles) damage. Water infiltration is discussed in Sections 6.3.3.1, 6.3.3.2, and 6.3.3.4. 

Tornadoes:  Although more than 1,200 tornadoes typically occur each 

year in the United States, the probability of a tornado occurring at any 

given location is quite small. The probability of occurrence is a function 

of location. As described in Section 6.5, only a few areas of the country 

frequently experience tornadoes, and tornadoes 

are very rare in the west. Figure 6-3 shows the top 

20 tornado-prone States in the United States. The 

Oklahoma City area is the most active location, 

with 123 recorded tornadoes between 1890 and 

2008 (Edwards, 2009). Well-designed, constructed, 

and maintained schools should experience little 

if any damage from weak tornadoes, except for 

window breakage. However, weak tornadoes often cause building envelope damage because of 

wind-resistance deficiencies. Most schools experience significant damage if they are in the path of a 

strong or violent tornado because they typically are 

not designed for this type of storm. 

Missile damage is very common during 

hurricanes and tornadoes. Missiles can 

puncture roof coverings, many types of exterior walls, and glazing. The IBC does not 

address missile-induced damage, except 

for glazing in wind-borne debris regions. 

(Wind-borne debris regions are limited 

to portions of hurricane-prone regions.) 

In hurricane-prone regions, significant 

missile-induced building damage should be 

expected, even during design level hurricane events, unless special enhancements 

are incorporated into the building’s design 

(discussed in Section 6.3).
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

In the classroom wing shown in Figure 6-4, all of the exterior windows 

were broken, and virtually all of the cementitious wood-fiber deck panels 

were blown away during a tornado. Much of the metal decking over the 

band and chorus area also blew off. The gymnasium collapsed, as did a 

portion of the multi-purpose room. The school was not in session at the 

time the tornado struck. See Section 6.5 for recommendations pertaining to tornadoes. 

Figure 6-3:  Average number of tornadoes per year (1953–2005)

26

22

22

22

22

23

29

46

56

56

137

19

54

28 26

27

25

30

37

34
6-6 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

6 MAKING SCHOOLS SAFE FROM HIGH WINDS

6.1.3 Wind/Building Interactions

When wind interacts with a building, both positive and negative (i.e., 

suction) pressures occur simultaneously. Schools must have sufficient 

strength to resist the applied loads from these pressures to prevent windinduced building failure. Loads exerted on the building envelope are 

transferred to the structural system, where in turn 

they must be transferred through the foundation 

into the ground. The magnitude of the pressures 

is a function of the following primary factors: exposure, basic wind speed, topography, building height, 

internal pressure, and building shape. General information on exposure and basic wind speed is 

presented below. For general information on topography, building height, and internal pressure, 

refer to Section 3.1.3 in FEMA 543. A description 

of key issues follows. 

ASCE 7 specifies procedures for calculating wind 

pressures and forces based on the primary factors 

listed above. The IBC refers to ASCE 7 for wind 

load determination. 

Exposure: The characteristics of the terrain (i.e., ground roughness and 

surface irregularities in the vicinity of a building) influence the wind 

loading. ASCE 7 defines three exposure categories, Exposures B, C, and 

D. Exposure B is the roughest terrain category and Exposure D is the 

In the 2005 and earlier editions of ASCE 

7, Exposure C included areas adjacent to 

water surfaces in hurricane-prone regions 

because earlier research indicated that 

wave conditions generated by hurricanes 

resulted in roughness that approximated 

Exposure C conditions. However, subsequent research showed that the surface 

roughness over the ocean during a hurricane is consistent with that of Exposure D. 

Consequently, the 2010 edition of ASCE 7 

requires use of Exposure D along the hurricane coastline.

Figure 6-4: 

This high school was 

damaged by a strong 

tornado (Plainfield, IL 

1990)
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-7

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

smoothest. Exposure B includes urban, suburban, 

and wooded areas. Exposure C includes flat open 

terrain with scattered obstructions and grasslands. 

Exposure D includes areas adjacent to water surfaces, mud flats, salt flats, and unbroken ice. 

The smoother the terrain, the greater the wind 

load; therefore, schools (with the same basic wind 

speed) located in Exposure D would receive higher 

wind loads than those located in Exposure C. 

Wind speed:  ASCE 7 specifies the basic (design) 

wind speed for determining design wind loads. The 

basic wind speed is measured at 33 feet above grade 

in Exposure C (flat open terrain). If the building 

is located in Exposure B or D, rather than C, an 

adjustment for the actual exposure is made in the 

ASCE 7 calculation procedure.

Since the 1995 edition of ASCE 7, the basic wind 

speed measurement has been a 3-second peak gust 

speed. Prior to that time, the basic wind speed was 

a fastest-mile speed (i.e., the speed averaged over 

the time required for a mile-long column of air to 

pass a fixed point). Because the measuring time for 

peak gust versus fastest-mile is different, peak gust 

speeds are greater than fastest-mile speeds. 

In the 2005 and earlier editions of ASCE 7, one 

map was used to determine the basic wind speed. 

However, in the 2010 edition of ASCE 7, three maps 

based on building risk provide the basic wind speed. 

One map is for Risk Category I buildings, another 

for Risk Category II buildings, and another for Risk 

Category III and IV buildings. All three are strength 

design wind speed maps. Hence, a load factor of 1.0 

is used, rather than 1.6 as used in the 2005 edition. 

To account for the degree of hazard to human life 

and damage to property, the 2005 and earlier editions of ASCE 7 used an importance factor in the 

load calculation equation. In the 2010 edition, the importance factor was 

eliminated because the degree of hazard to human life and property damage is accounted for by the wind speeds in the appropriate map. Figure 6-5 

shows the map for Risk Category III and IV, which as discussed in Section 

6.3.1.2 are the Categories that this manual recommends for all schools. 

Because the ASCE 7-10 maps are strength 

design wind speeds, the speeds are substantially greater than the speeds given in 

the 2005 and earlier editions. However, because of the load factor change, pressures 

calculated in accordance with the 2010 edition should be similar to those calculated in 

accordance with the 2005 edition.

For additional exposure information, 

see the Commentary of ASCE 7, which 

includes several aerial photographs that 

illustrate the different terrain conditions associated with Exposures B, C, and D.

Although the ASCE 7-10 maps provide 

strength design wind speeds, for the design 

of hurricane and tornado safe rooms/shelters, the design wind speeds given in FEMA 

361 and ICC 500 are recommended (see 

Section 6.5). The FEMA 361 and ICC 500 

speeds are based on a much greater mean 

recurrence interval than the ASCE 7 speeds.

Refer to Section 5.1.6.4 for a discussion of 

Risk Category III and IV.

Applied Technology Council wind speed 

Web site: A site-specific basic wind speed 

can be obtained at the following Web site 

by entering the site location. The Web site 

provides speeds based on ASCE 7-93, 7-05, 

and 7-10. http://windspeed.atcouncil.org
6-8 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

6 MAKING SCHOOLS SAFE FROM HIGH WINDS

As shown on Figure 6-5, for Risk Category III and IV buildings, most of 

the United States has a basic wind speed (peak gust) of 120 mph, but 

much higher speeds occur in Alaska and in hurricane-prone regions. 

The highest speed, 210 mph, occurs in Guam. 

Hurricane-prone regions include Atlantic and Gulf coastal areas (where 

the basic wind speed is greater than 120 mph on the map shown in 

Figure 6-5), Hawaii, and the U.S. territories in the Caribbean and South 

Pacific. The boundary of the Atlantic and Gulf coast hurricane-prone region shifted towards the coast in the 2010 edition of ASCE 7 because of 

improvements in the hurricane simulation model 

(see Figure 6-2). 

In the ASCE 7 formula for determining wind pressures, the basic wind speed is squared. Therefore, 

as the wind speed increases, the pressures are exponentially increased, as illustrated in Figure 6-6. 

This figure also illustrates the relative difference in 

pressures exerted on the main wind-force resisting 

system (MWFRS) and the components and cladding (C&C) elements. 

The MWFRS is an assemblage of structural elements assigned to provide support 

and stability for the overall structure. The 

system generally receives wind loading 

from more than one surface. The C&C are 

elements of the building envelope that do 

not qualify as part of the main wind-force 

resisting system.

Figure 6-5: Basic wind speeds for Risk Category III and IV buildings and other structures

SOURCE: ASCE 7-10
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-9

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Building shape: The highest uplift pressures occur at roof corners because 

of building aerodynamics (i.e., the interaction between the wind and the 

building). The roof perimeter has a somewhat lower load compared to 

the corners, and the field of the roof has still lower loads. Exterior walls 

typically have lower loads than the roof. The ends (edges) of walls have 

higher suction loads than the portion of wall between the ends. However, 

when the wall is loaded with positive pressure, the entire wall is uniformly 

loaded. Figure 6-7 illustrates these aerodynamic influences. The negative 

values shown in Figure 6-7 indicate suction pressure acting upward from 

the roof surface and outward from the wall surface. Positive values indicate positive pressure acting inward on the wall surface. 

Aerodynamic influences are accounted for by using external pressure coefficients in load calculations. The value of the coefficient is a function of 

the location on the building (e.g., roof corner or field of roof) and building shape as discussed below. Positive coefficients represent a positive 

(inward-acting) pressure, and negative coefficients represent negative 

(outward-acting [suction]) pressure. External pressure coefficients for 

MWFRS and C&C are listed in ASCE 7.

Building shape affects the value of pressure coefficients and, therefore, 

the loads applied to the various building surfaces. For example, the uplift 

loads on a low-slope roof are larger than the loads on a gable or hip roof. 

The steeper the slope, the lower the uplift load. Pressure coefficients for 

monoslope (shed) roofs, sawtooth roofs, and domes are all different from 

those for low-slope and gable/hip roofs.

250.0

200.0

150.0

100.0

50.0

0.0

90 100 110 120 130 140 150 160 170

Pressure (psf – presented as absolute values)

Velocity – mph (3-second gust)

Note: The pressure increase on a 

portion of a roof designed for 

Componentsand Cladding (C&C) 

versus the Main Wind Force-Resisting 

System (MWFRS) is approximately 

327 percent. 

Roof Corner Pressures – C&C

Roof Corner Pressures – MWFRS

Figure 6-6: 

Wind pressure as a 

function of wind speed
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Building irregularities, such as re-entrant corners, bay window projections, a stair tower projecting out from the main wall, dormers, and 

chimneys can cause localized turbulence. Turbulence causes wind 

speed-up, which increases the wind loads in the vicinity of the building 

irregularity, as shown in Figures 6-8 and 6-9. Figure 6-8 shows the aggregate ballast on a building’s single-ply membrane roof blown away at the 

re-entrant corner and in the vicinity of the corners of the wall projections 

at the window bays. The irregular wall surface created turbulence, which 

led to wind speed-up and loss of aggregate in the turbulent flow areas.

Figure 6-7: 

Relative roof uplift 

pressures as a function 

of roof geometry, roof 

slope, and location 

on roof, and relative 

positive and negative 

wall pressures as a 

function of location 

along the wall

Flat or gable, up to 7o roof 

slope, no overhang

Gable, >7o to 45o roof slope, 

overhang all sides

Hip or gable, 7o to 27o roof 

slope, overhang all sides

–51.5 psf at perimeter, corners, and ridge line                   

–48.2 psf at perimeter

–80.9 psf at corners

Note: Design pressures all assume an enclosed Category III or IV building with the same basic 

wind speed of 120 mph, exposure B, and 30' roof height, based on ASCE 7-10. 

–41.3 psf at hip and ridge lines

–25.9 psf

–43.5 psf

–28.1 psf

–34.7 psf

–34.7 psf

+25.9 psf

–25.9 psf

–65.4 psf

–23.7 psf
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-11

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Figure 6-9 shows a building stair tower that caused turbulence resulting in wind speed-up. The speed-up increased the suction pressure on 

the base flashing along the parapet behind the stair tower. The built-up 

roof’s base flashing was pulled out from underneath the coping because 

its attachment was insufficient to resist the suction pressure. The base 

flashing failure propagated and caused a large area of the roof membrane to lift and peel. Some of the wall covering on the stair tower was 

also blown away. Had the stair tower not existed, the built-up roof would 

likely not have been damaged. To avoid damage in the vicinity of building 

irregularities, attention needs to be given to the attachment of building 

elements located in turbulent flow areas. 

Figure 6-8: 

Aggregate blow-off 

associated with building 

irregularities. Hurricane 

Hugo (South Carolina, 

1989)

Figure 6-9: 

The irregularity created 

by the stair tower 

(covered with a metal 

roof) caused turbulence 

resulting in wind speedup and roof damage. 

Hurricane Andrew 

(Florida, 1992)
6-12 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

6 MAKING SCHOOLS SAFE FROM HIGH WINDS

To avoid the roof membrane damage shown in 

Figure 6-9, it would be prudent to use corner uplift 

loads in lieu of perimeter uplift loads in the vicinity 

of the stair tower, as illustrated in Figure 6-10. Wind 

load increases due to building irregularities can be 

identified by wind tunnel studies; however, wind 

tunnel studies are rarely performed for schools. 

Therefore, identification of wind load increases 

due to building irregularities is normally based on 

the designer’s professional judgment. Usually load 

increases only need to be applied to the building envelope, and not to 

the MWFRS. 

6.1.4 Building Codes

The IBC is the most extensively used model code. However, in some jurisdictions, one of the earlier model building codes, or a specially written 

State or local building code, may be used. The specific scope and/or effectiveness and limitations of these other building codes are somewhat 

different from those of the IBC. It is incumbent upon the design professionals to be aware of the specific code (including the edition of the code 

and local amendments) that has been adopted by the authority having 

jurisdiction over the location of the school. 

Figure 6-10: 

Plan view of a portion 

of the building in Figure 

6-9 showing the use of 

a corner uplift zone in 

lieu of a perimeter uplift 

zone on the low-slope 

roof in the vicinity of the 

stair tower

Information pertaining to load calculations is presented in Section 6.3.1.2. For 

further general information on the nature 

of wind and wind-building interactions, see 

Buildings at Risk: Wind Design Basics for 

Practicing Architects (American Institute of 

Architects, 1997).
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.1.4.1 Scope of Building Codes

With respect to wind performance, the scope of the model building 

codes has greatly expanded since the mid-1980s. Some of the most significant improvements are discussed below.

Recognition of increased uplift loads at the roof perimeter and corners: Prior to the 1982 edition of the Standard Building Code (SBC) and the 

Uniform Building Code (UBC), and the 1987 edition of the National 

Building Code (NBC), these model codes did not account for the increased uplift at the roof perimeter and corners. Therefore, schools 

designed in accordance with earlier editions of these codes are very susceptible to blow-off of the roof deck and/or roof covering. 

Adoption of ASCE 7 for design wind loads: Although the SBC, UBC, and 

NBC permitted use of ASCE 7, the 2000 edition of the IBC was the first 

model code to require ASCE 7 for determining wind design loads on all 

buildings. ASCE 7 has been more reflective of the current state of the 

knowledge than the earlier model codes, and use of this procedure typically has resulted in higher design loads. 

Roof coverings: Several performance and prescriptive requirements pertaining to wind resistance of roof coverings have been incorporated into 

the model codes. The majority of these additional provisions were added 

after Hurricanes Hugo (1989) and Andrew (1992). Poor performance 

of roof coverings was widespread in both of those storms. Prior to the 

1991 edition of the SBC and UBC, and the 1990 edition of the NBC, 

these model codes were essentially silent on roof covering wind loads 

and test methods for determining uplift resistance. Code improvements 

continued to be made through the 2006 edition of 

the IBC, which added a provision that prohibits aggregate roof surfaces in hurricane-prone regions.

Glazing protection: The 2000 edition of the IBC was 

the first model code to address wind-borne debris 

(missile) requirements for glazing in buildings located in hurricane-prone regions (via reference to 

the 1998 edition of ASCE 7). The 1995 edition of 

ASCE 7 was the first edition to address wind-borne 

debris requirements.

ASCE 7 requires impact-resistant glazing in 

wind-borne debris regions within hurricaneprone regions. Impact-resistant glazing can 

either be laminated glass, polycarbonate, 

or shutters tested in accordance with standards specified in ASCE 7. The wind-borne 

debris load criteria were developed to 

minimize property damage and to improve 

building performance. The criteria were not 

developed for occupant protection. Where 

occupant protection is a specific criterion, 

the more conservative wind-borne debris 

criterion given in FEMA 361, Design and 

Construction Guidance for Community 

Shelters, is recommended. 
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Parapets and rooftop equipment: The 2003 edition of the IBC was the first 

model code to address wind loads on parapets and rooftop equipment 

(via reference to the 2002 edition of ASCE 7, which was the first edition 

of ASCE 7 to address these elements).

High-wind shelters: The 2009 edition of the IBC was the first model code 

to adopt the new ICC 500. See Section 6.5 for further discussion of ICC 

500.

6.1.4.2 Effectiveness and Limitations of Building Codes

A key element of an effective building code is for a community to have 

an effective building department. Building safety depends on more than 

the codes and the standards they reference. Building safety results when 

trained professionals have the resources and ongoing support they need 

to stay on top of the latest advancements in building safety. An effective 

building safety system provides uniform code interpretations, product 

evaluations, and professional development and certification for inspectors 

and plan reviewers. Local building departments play an important role in 

helping to ensure buildings are designed and constructed in accordance 

with the applicable building codes. Meaningful plan review and inspection by the building department are particularly important for schools.

General limitations to building codes include the following:

n Because codes are adopted and enforced on the local or State level, 

the authority having jurisdiction has the power to eliminate or modify wind-related provisions of a model code, or write its own code 

instead. In places where important wind-related provisions of the 

current model code are not adopted and enforced, schools are more 

susceptible to wind damage. Additionally, a significant time lag often 

exists between the time a model code is updated and the time it is implemented by the authority having jurisdiction. Buildings designed 

to the minimum requirements of an outdated code are, therefore, 

not taking advantage of the current state of the knowledge. These 

buildings are prone to poorer wind performance compared to buildings designed according to the current model code.

n Adopting the current model code alone does not ensure good wind 

performance. The code is a minimum that should be used by knowledgeable design professionals in conjunction with their training, 

skills, professional judgment, and the best practices presented in this 

manual. To achieve good wind performance, in addition to good 

design, the construction work must be effectively executed, and the 

building must be adequately maintained and repaired.

n Schools need to perform at a higher level than required by codes 

and standards. 
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-15

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Figure 6-11: 

The single-ply roof 

membrane on this 

school was torn by a 

missile. The tear was 

still unprotected 6 days 

after it was damaged. 

A substantial amount 

of water can enter the 

building through such a 

tear, unless the deck is 

water tight (see Figure 

6-13) or a secondary 

roof membrane is used 

as discussed in Section 

6.3.3.7. Estimated wind 

speed: 105 to 115 mph. 

Hurricane Ivan (Florida, 

2004)

IBC 2009: The 2009 edition of the IBC is believed to be a relatively effective code, provided that it is properly followed and enforced. However, 

with respect to hurricanes, the IBC provisions pertaining to building envelopes and rooftop equipment do not adequately address the special 

needs of schools. For example, the following is a list of items that need to 

be addressed through the use of best practices: 

n They do not account for water infiltration due to puncture of the 

roof membrane by missiles (see Figure 6-11)

n They do not adequately address the vulnerabilities of brittle roof 

coverings (such as tile) to missile-induced damage and subsequent 

progressive failure

n For schools used as hurricane recovery centers after a hurricane, 

they do not account for interruption of water or sewer service or 

prolonged interruption of electrical power. 

Addressing the first two elements is important for ensuring that the 

buildings are in suitable condition for school to resume within a couple 

of weeks after a hurricane. The last element is important for schools 

that will be used for recovery centers. Guidance for addressing these elements where they are not adequately addressed in IBC is provided in 

Sections 6.3 and 6.4.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

n	 The 2000, 2003, 2006, and 2009 IBC rely on several referenced standards and test methods developed or updated in the last two decades. 

Prior to adoption, most of these standards and test methods had not 

been validated by actual building performance during design level 

wind events. The hurricanes of 2004, 2005, and 2008 provided an opportunity to evaluate the actual performance of buildings designed 

and constructed to the minimum provisions of the IBC. Building 

performance evaluations conducted by FEMA revealed the need for 

further enhancements to the 2009 IBC pertaining to some of the test 

methods used to assess wind and wind-driven rain resistance of building envelope components. For example, there is no test method to 

assess wind resistance of gutters. Further, the test method to evaluate the resistance of windows to wind-driven rain is inadequate for 

high wind events. However, before testing limitations can be overcome, research needs to be conducted, new test methods need to 

be developed, and some existing test methods need to be modified. 

Guidance to address shortcomings in standards and test methods is 

provided in Sections 6.3 and 6.4.

n	 The 2009 IBC Section 1614 is a new provision that addresses structural integrity (i.e., requirements for continuity, redundancy, or 

energy-dissipating capability [ductility] to limit the effects of local 

collapse, and to prevent or minimize progressive collapse after the 

loss of one or two primary structural members, such as a column). 

However, the Section only pertains to Category III and IV high-rise 

buildings. Although schools are not required to comply with this 

Section, this manual recommends that school designers consider 

the criteria in Section 1614. 

n	 Except for storm shelters, the 2009 IBC does not account for tornadoes; therefore, except for weak tornadoes, it is ineffective for this 

type of storm.5

 Guidance to overcome this shortcoming is given in 

Section 6.5.

5 Except for glass breakage, code-compliant buildings should not experience significant 

damage during weak tornadoes.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Figure 6-12: 

Constructed in 1995, 

this school was used 

as a hurricane shelter. 

The large number of 

occupants moved from 

one area of the school 

to another as water 

entered various areas 

of the building due 

to envelope failures. 

Estimated wind 

speed: 105 to 115 mph. 

Hurricane Ivan (Florida, 

2004)

6.2 Schools Exposed to High Winds

6.2.1 Vulnerability: What High Winds Can Do to Schools

This section provides an overview of the common types of wind damage 

and their ramifications.

6.2.1.1 Types of Building Damage

When damaged by wind, schools typically experience a variety of building component damage. For example, at the school shown in Figure 

6-12, the roof covering was severely damaged, metal wall panels were 

blown off, and rooftop equipment was blown away. Water entered the 

building at all of these envelope breaches. The most common types of 

damage are discussed below in descending order of frequency. 

Roof: Roof covering damage (including rooftop mechanical, electrical, 

and communications equipment) is the most common type of wind damage, as illustrated by Figure 6-13. At this school, a portion of the built-up 

membrane lifted and peeled after the metal edge flashing lifted. The 

cast-in-place concrete deck kept most of the water from entering the 

building. Virtually all of the loose aggregate blew off the roof and broke 

many windows in nearby houses. This school was used as a hurricane 

shelter at the time of the blow-off.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Glazing: Exterior glazing damage is very common during hurricanes and 

tornadoes, but is less common during other storms. The glass shown in 

Figure 6-14 was broken by the aggregate from a built-up roof. The inner panes had several impact craters. In several of the adjacent windows, 

both the outer and inner panes were broken. The aggregate flew more 

than 245 feet. 

Figure 6-14: 

The outer window 

panes were broken by 

aggregate from a builtup roof. Estimated 

wind speed: 104 mph. 

Hurricane Hugo (South 

Carolina, 1989)

Figure 6-13: 

Extensive roof covering 

and rooftop equipment 

damage occurred on this 

school. However, the 

cast-in-place concrete 

deck kept most of the 

water from entering 

the school. Hurricane 

Andrew (Florida, 1992)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Wall coverings, soffits, and large doors: Exterior wall covering, soffit, and 

large door damage is common during hurricanes and tornadoes, but is 

less common during other storms. At the school shown in Figure 6-15, 

metal wall panels were blown off the gable end wall, thereby allowing 

wind-driven rain to enter the building.

Wall collapse:  Collapse of non-load-bearing exterior walls is common 

during tornadoes, but is less common during other storms. At the school 

shown in Figure 6-16, the unreinforced CMU wall collapsed during a 

hurricane. 

Figure 6-15: 

Blow-off of metal wall 

panels allowed winddriven rain to enter 

this school. Hurricane 

Frances (Florida, 2004)

Figure 6-16: 

Collapsed unreinforced 

CMU wall. Hurricane 

Marilyn (U.S. Virgin 

Islands, 1995)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-17: 

The roof and all of the 

walls of a wing of this 

elementary school were 

blown away by a violent 

tornado. (Oklahoma City, 

1999)

Figure 6-18: 

This elementary 

school was composed 

of several buildings. 

The building in the 

foreground collapsed 

and several others 

experienced significant 

structural damage. The 

buildings further up the 

hillside are residences. 

Hurricane Marilyn (U.S. 

Virgin Islands, 1995)

Structural system: Structural damage (e.g., roof deck blow-off, blow-off 

or collapse of the roof structure, collapse of exterior bearing walls, or 

collapse of the entire building or major portions thereof) is the principal 

type of damage that occurs during strong and violent tornadoes (see 

Figure 6-17). Structural damage occasionally occurs during hurricanes 

(Figures 6-18, 6-21, 6-24, 6-26, and 6-34). Portable classrooms are also 

sometimes severely damaged or overturned as shown in Figure 6-19. 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.2.1.2 Ramification of Damage

The ramifications of building component damage on schools are described below.

Property damage:  Property damage requires repairing/replacing the 

damaged components (or replacing the entire facility), and may require 

repairing/replacing interior building components, furniture, and other 

equipment, books, and mold remediation. As illustrated by Figures 6-11, 

6-12, 6-13, and 6-20, even when damage to the building envelope is limited, 

such as blow-off of a portion of the roof or wall covering or broken glazing, 

substantial water damage frequently occurs because heavy rains often accompany strong winds (particularly in the case of thunderstorms, tropical 

storms, hurricanes, and tornadoes). 

Wind-borne debris such as roof aggregate, gutters, rooftop equipment, 

and siding blown from buildings can damage vehicles and other buildings in the vicinity. Debris can travel well over 300 feet in high-wind 

events.

Ancillary buildings (such as storage or shop buildings) adjacent to schools are also vulnerable to 

damage. Although loss of these buildings may not 

be crippling to the operation of the school, debris 

from ancillary buildings may strike and damage the 

school (Figure 6-21).

Figure 6-19: 

This portable classroom 

was blown up against 

the main school 

building. Depending 

upon the type of exterior 

wall, an impacting 

portable classroom 

may or may not cause 

wall collapse. Hurricane 

Marilyn (U.S. Virgin 

Islands, 1995)

Modest wind speeds can drive rain into 

exterior walls. Unless adequate provisions 

are taken to account for water infiltration 

(see Sections 6.3.3.1–6.3.3.5), damaging 

corrosion, dry rot, and mold can occur 

within the walls.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Portable classrooms are often particularly vulnerable to significant 

damage because they are seldom designed to the same wind loads as 

permanent school buildings. Portable classrooms are frequently blown 

over during high-wind events because of the inexpensive techniques typically used are inadequate to anchor the units to the ground (see Figures 

6-19 and 6-22). Wind-borne debris from portables or an entire portable 

classroom may impact the permanent school building and cause serious 

damage (Figure 6-19).

Figure 6-21: 

The entire metal 

deck and steel joist 

roof structure at this 

school’s auto shop blew 

off. Estimated wind 

speed: 105 to 115 mph. 

Hurricane Ivan (Florida, 

2004)

Figure 6-20: 

This newly-constructed 

gymnasium had a 

structural metal roof 

panel (3-inch trapezoidal 

ribs at 24 inches on 

center) applied over 

metal purlins. The 

panels detached from 

their concealed clips. 

A massive quantity of 

water entered the school 

and buckled the wood 

gym floor. Typhoon Paka 

(Guam, 1997)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Injury or death:  Although infrequent, school occupants or people outside schools have been injured 

and killed when struck by collapsed building components (such as exterior masonry walls or the 

roof structure) or wind-borne debris. The greatest 

risk of injury or death is during strong hurricanes 

and strong/violent tornadoes. The old school 

shown in Figure 6-23 was used as a hurricane shelter, even though it was not originally designed or 

subsequently retrofitted (i.e., mitigated) to serve 

as a shelter. The roof structure was composed of 

cementitious wood-fiber panels over steel joists. In 

the era when this building was constructed, these 

types of panels typically had very limited uplift resistance in perimeter and corner areas. Also, steel 

joists in that era typically offered limited uplift resistance. Structural failure was avoided not because 

of the strength of the building, but rather, because 

winds at the site were not as strong as they reasonably could have been expected to be. 

Figure 6-22: 

The metal straps 

between this portable 

classroom and the 

ground anchors were 

not taut. This classroom 

is susceptible to being 

blown off the piers and 

to overturning. See 

Figure 6-27 for a robust 

anchoring system.

People are not usually outside a school 

during hurricanes. However, when schools 

are used as hurricane shelters, it is 

common for people to arrive at schools 

during very high winds. Missiles such as 

roof aggregate or tile shedding from a 

school could injure or kill late arrivals to the 

shelter. 

Also, students arriving at or departing 

from a school could be vulnerable. A 1967 

tornado killed 13 students at the Belvedere 

High School in northern Illinois and seriously injured many others. School had 

been dismissed shortly before the tornado 

struck and many students were in school 

buses as the tornado approached the 

school. Although an attempt was made to 

get the students back inside the school, 

12 of the buses were thrown about by the 

tornado before the students could seek 

shelter within the school. Aggregate from 

the school’s built-up roof penetrated the 

flesh of several students. 
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Interrupted use: Depending upon the magnitude of wind and water damage, it can take days, months, or more than a year to repair the damage 

or replace a facility (see Figure 6-24). In addition to the costs associated 

with repairing/replacing the damage, other social and financial costs 

can be even more significant. Additional costs related to interrupted use 

of schools can include the cost of bussing students to alternative schools 

and/or rental of temporary facilities, and can be quite substantial. 

There are also social and psychological factors, such as difficulties imposed on students, parents, faculty, and the administration during the 

time the school is not usable.

Figure 6-23: 

This old school was 

used as a hurricane 

shelter. Structural failure 

did not occur during 

this hurricane. However, 

portions of the roof 

covering were blown 

off, rooftop equipment 

was damaged, and 

many windows were 

broken by aggregate 

from the built-up roof 

(red arrow). Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.2.2 Priorities, Costs, And Benefits: New Schools

Priorities, costs, and benefits of potential risk reduction measures should 

be evaluated before beginning the risk reduction design process. These 

factors, as discussed below, should be considered within the context of 

performance-based wind design as discussed in Section 2.7. 

6.2.2.1 Priorities

The first priority in risk reduction is the implementation of measures 

that will reduce risk of casualties to students, faculty, staff, and visitors. 

The second priority is the reduction of damage that leads to downtime 

and disruption. The third priority is the reduction of damage and repair costs. To realize these priorities, the school should be designed and 

constructed, as a minimum, in accordance with the latest edition of a 

current model building code such as the IBC unless the local building 

code has more conservative wind-related provisions, in which case the local building code should be used as the basis for design. In addition, the 

school should be adequately maintained and repaired.

Figure 6-24: 

A portion of the roof structure blew off this school, and 

a portion of it collapsed into classrooms. Extensive 

water damage can cause such a school to be out of 

operation for a considerable period of time. Hurricane 

Marilyn (U.S. Virgin Islands, 1995)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

For schools that will be used for emergency response after a storm and/or those schools that will 

be used for hurricane shelters, measures beyond 

those required by the IBC should be given high 

priority (see Section 6.5).

For schools located in tornado-prone regions, the 

incorporation of specially designed occupant shelters within the school (see Section 6.5) should be 

given priority. The decision to incorporate occupant shelters should be based on the assessment 

of risk (see Section 6.5). 

For schools located in areas where the basic wind 

speed is greater than 120 mph, the incorporation 

of design, construction, and maintenance enhancements should be given priority.6

 The degree 

of priority given to these enhancements increases 

as the basic wind speed increases (see Step 4: Peer 

Review in Section 6.3.1.2 and Sections 6.3.2, 6.3.3 

and 6.3.4 for enhancement examples).7

6.2.2.2 Cost, Budgeting, and Benefits

The cost to comply with the IBC should be considered as the minimum baseline cost.

For schools that will be used for emergency response after a storm and/or schools that will be 

used for hurricane shelters, the additional cost for 

implementing measures beyond those required by 

the 2009 edition of the IBC will typically add only a 

small percentage to the total cost of construction. 

Sections 6.3, 6.3.4, 6.4, and 6.5 discuss additional 

measures that should be considered. 

6 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph. 

7 FEMA 361 is a manual for architects and engineers. It presents detailed guidance concerning 

the design and construction of safe rooms that provide “near-absolute protection” from 

tornadoes and hurricanes (see Section 6.5 for the distinction between shelters and safe 

rooms). FEMA 361 discusses safe room location, design loads for wind pressure and 

wind-borne debris, performance criteria, and human factor criteria. It is accompanied by a 

benefit-cost model.

The benefit-cost ratio of incorporating 

specially designed tornado safe rooms 

within schools can be assessed using 

software that accompanies the FEMA BCA 

Toolkit and the FEMA BCA Software (version 4.5.4). Tornado shelters have been 

constructed in several schools in Kansas, 

Oklahoma, and a few other States. An architect involved with several of the Kansas 

schools reports that the additional cost to 

incorporate a shelter ranges from about 

$40.50 to $51.50 per square foot (psf) of 

shelter space (year 2010 costs). Oftentimes 

as the safe room is small compared to 

the entire school, this results in only a 1 

to 3 percent increase to total project cost. 

FEMA 361 recommends using a minimum 

of 5 square feet per person for sheltering; 

therefore, the $40.50 to $51.50 psf equates 

to about $200 to $260 per student and staff 

for “near absolute protection” (i.e., protection from injury or death) from a violent 

tornado. Tornado safe rooms and shelters 

are discussed in Section 6.5. 

The increase in costs to construct a safe 

room for the hurricane hazard has a much 

more significant variation. This is because 

of the great variation of basic wind speeds 

in hurricane-prone regions. Hence, the incremental costs in the highest wind speed 

areas are much less than the costs in the 

lower wind speed areas. See FEMA 361, 

Chapter 2.7
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

For all other schools, the additional cost for implementing enhancements will typically add only a very small percentage to the total cost of 

construction. Sections 6.3 to 6.4 discuss additional measures that should 

be considered.

The yearly cost of periodic maintenance and repair is greater than the 

alternative of not expending any funds for periodic maintenance (i.e., 

deferred maintenance and repair). The extent and cost of the deferred 

maintenance and repair is typically much greater over the long term. 

Also, if a windstorm causes damage that would have otherwise been 

avoided had maintenance or repairs been performed, the resulting costs 

can be significantly higher. (Note: Maintenance and repair costs are reduced when more durable materials and systems are used; see Section 

6.3.1.2, under Step 3, Durability.)

Budgeting:  School districts should give consideration to wind enhancement costs early in the development of a new school project. If 

enhancements, particularly those associated with schools used as hurricane shelters, for emergency response after a storm, and as tornado 

shelters, are not included in the initial project budget, often it is very difficult to find funds later during the design of the project. If the additional 

funds are not found, the enhancements may be eliminated because of 

lack of forethought and adequate budgeting. 

Benefits: If strong storms do not occur during the life of a school, money 

and effort spent on wind resistance provide little benefit. However, considering the long life of most schools (hence, the greater probability of 

experiencing a design level event) and the importance of schools to the 

community, investing in adequate wind resistance is prudent. The potential for loss of life and injuries can be significantly reduced or virtually 

eliminated. Investing in wind resistance also minimizes future expenditures for repair or replacement of wind-damaged schools and avoids 

costly interruptions to building use.

Fortunately, most of the enhancements for increased wind resistance 

are relatively inexpensive compared to the benefits that they provide. 

Enhancements that provide greater performance reliability at a lower 

cost should be considered. For the building shown in Figure 6-25, a 

few inexpensive fasteners would have prevented costly repairs and interrupted use of a portion of the building. After the HVAC unit blew 

off the roof curb and landed in the parking lot, a substantial amount 

of water entered the building before a temporary covering could be 

placed over the opening. The blow-off was caused by a load path discontinuity; no provisions had been made to anchor the unit to the 

curb. The insignificant cost of a few fasteners would have prevented 
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

repairs costing several thousand dollars and also prevented interrupted use of a portion of the building. 

Wind resistance enhancements may also result in decreased insurance 

premiums. School districts should consult their insurer to see if premium reductions are available, and to see if special enhancements are 

required in order to avoid paying a premium for insurance. For those 

school districts that self-insure, enhanced wind resistance should result 

in a reduction of future payouts.

6.2.3 Priorities, Costs, and Benefits: Existing Schools

Priorities, costs, and benefits of potential risk reduction measures should 

be evaluated before beginning the risk reduction design process. These 

factors, as discussed below, should be considered within the context of 

performance-based wind design as discussed in Section 2.7. 

6.2.3.1 Priorities

School districts should assess schools for all applicable hazards to determine which schools are vulnerable to damage and most in need of 

remedial work. The highest priority work may or may not be related to 

wind. In some instances, the same remedial work may mitigate multiple 

hazards. For example, strengthening a roof deck attachment can improve both wind and seismic resistance.

Figure 6-25: 

Lack of fasteners 

resulted in blow-off of 

the HVAC unit, which 

caused extensive 

interior water damage 

and interrupted facility 

use. Hurricane Marilyn 

(U.S. Virgin Islands, 

1995)
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School districts located in the following areas (listed in descending order 

of priority) are at the greatest risk for wind damage: hurricane-prone regions and school districts outside of hurricane-prone regions that have 

schools that will be used for emergency response after a storm; tornado-prone regions; areas where the basic wind speed is in excess of 120 

mph (the priority increases as the basic wind speed increases); and areas 

where the basic wind speed is 120 mph or less.8

For school districts in hurricane-prone regions, schools that will be used 

as hurricane shelters should be the highest priority. Other priorities are 

as discussed at the beginning of Section 6.2.2.1. For school districts in 

tornado-prone regions, occupant protection (see Section 6.5) should be 

the highest priority. Other priorities are as discussed at the beginning of 

Section 6.2.2.1. For all other school districts, the priorities are the same 

as discussed at the beginning of Section 6.2.2.1.

In some instances, all the available funds for remedial work may be spent 

at one school. In other instances, the available funds may be used for remedial work at several schools.

See Section 6.4 for specific remedial work guidance.

6.2.3.2 Cost, Budgeting, and Benefits

Wind-resistance improvements should ideally address all elements in 

the load path from the building envelope to the structural system and 

into the ground (Load path is discussed in Section 6.3.1.2 under Step 

3, Detailed Design). However, this approach can be very expensive if 

there are many inadequacies throughout the load path. The maximum 

return on investment for wind-resistance improvements is typically for 

enhancements to the building envelope. Obviously if there are serious 

structural deficiencies that could lead to collapse during strong storms, 

these types of deficiencies should receive top priority; however, this scenario is infrequent. 

Because elements of the building envelope are the building components 

most likely to fail in the more common moderate wind speed events, 

strengthening these elements will avoid damage during those storms. 

In a storm approaching a design level event, the building envelope will 

remain attached to the structure, but a structural element may fail. For 

example, if the connections between the roof joists and bearing walls are 

the weak link, the roof covering will remain attached to the roof deck 

and the deck will remain attached to the joists, but the entire roof structure will blow off because the joists will detach from the wall. Although 

8 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

loss of the entire roof structure is more catastrophic than the loss of just 

the roof covering, much stronger events are typically required to cause 

structural damage. Hence, on a school district-wide level, strengthening 

building envelopes will likely result in the maximum return for windresistance improvements. Of course, for a specific school, the scope of 

wind-resistance work should be tailored to each school, commensurate 

with the findings from the hazard assessment (as discussed in Section 

6.2.4.2) and the benefit-cost analysis (discussed below).

Costs can be minimized if wind-resistance improvements are executed as 

part of planned repairs or replacement. For example, if the roof deck is 

inadequately attached in the perimeter and corners (see Figure 6-26), and 

the roof covering has another 10 years of remaining service life, it would 

typically be prudent to postpone performing deck attachment upgrade 

until it is necessary to replace the roof covering. Then, as part of the reroofing work, the existing roof system could be torn off, the deck reattached 

or replaced, and the new membrane installed.9

 This approach provides 

the cost benefit of utilizing the full service life of the roof membrane.

Budgeting: As with new construction, school districts should give consideration to wind enhancement costs early in the development of a major 

repair/renovation project (see discussion in Section 6.2.2.2).

9 In some cases, reattaching the decking from below the deck may be more economical, but 

typically this approach is more costly.

Figure 6-26: 

The cementitious woodfiber deck panels blew 

off the overhangs and 

caused a progressive 

lifting and peeling of 

the roof membrane. 

Strengthening (or 

replacing) inadequately 

attached roof decks 

during a reroofing 

project is both 

prudent and relatively 

economical. Estimated 

wind speed: 120 mph. 

Hurricane Katrina 

(Mississippi, 2005)
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Benefits: The benefits of money and effort spent on wind resistance for 

existing schools are the same as described for new schools in Section 

6.2.2.2.

6.2.4 Evaluating Schools for Risk from High Winds

This section describes the process of hazard risk assessment. Although 

no formal methodology for risk assessment has been adopted, prior 

experience provides sufficient knowledge upon which to base a recommended procedure for risk assessment of schools. The procedures 

presented below establish guidelines for evaluating the risk to new and 

existing buildings from windstorms other than tornadoes. These evaluations will allow development of a vulnerability assessment that can be 

used along with the site’s wind regime to assess the risk to schools.

In the case of tornadoes, neither the IBC nor ASCE 7 requires buildings (including schools) to be designed to resist tornado forces; nor 

are occupant shelters required in buildings located in tornado-prone 

regions.10 Constructing tornado-resistant schools is extremely expensive because of the extremely high pressures and missile impact loads 

that tornadoes can generate. Therefore, when consideration is voluntarily given to tornado design, the emphasis is typically on occupant 

protection, which is achieved by “hardening” portions of a school for 

use as safe havens. FEMA 361 includes a comprehensive risk assessment procedure that designers can use to assist building owners in 

determining whether a tornado shelter should be included as part of 

a new school. See Section 6.5 for recommendations pertaining to best 

practices for incorporating safe rooms in schools in hurricane- and 

tornado-prone regions.

6.2.4.1 New Buildings

When designing new schools, a two-step procedure is recommended for 

evaluating the risk from windstorms (other than tornadoes).

Step 1: Determine the basic wind speed from ASCE 7. As the basic wind 

speed increases beyond 120 mph, the risk of damage increases.11 Design, 

construction, and maintenance enhancements are recommended to 

compensate for the increased risk of damage (see Section 6.3).

10 The 2009 edition of the IBC references ICC 500 for the design and construction of hurricane 

and tornado shelters. However, as discussed in Section 6.5, while ICC 500 specifies shelter 

criteria, it does not require shelters.

11 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Step 2: For schools not located in hurricane-prone 

regions, determine if the school will be used for 

emergency response after a storm (e.g., temporary 

housing, food or clothing distribution, or a place 

where people can fill out forms for assistance). If 

so, refer to the design, construction, and maintenance enhancements recommended for schools 

in hurricane-prone regions (see Sections 6.3.1.5, 

6.3.2.2, 6.3.3.3, 6.3.3.5, 6.3.3.7, 6.3.4.2, 6.3.4.4, 

6.3.5, and 6.3.6).

Step 3: For schools in hurricane-prone regions, refer to the design, construction, and maintenance 

enhancements recommended in Sections 6.3.1.5, 

6.3.2.2, 6.3.3.3, 6.3.3.5, 6.3.3.7, 6.3.4.2, 6.3.4.4, 

6.3.5, and 6.3.6

6.2.4.2 Existing Buildings

The resistance of existing buildings is a function of their original design and construction, various additions or modifications, and the 

condition of building components (which may have weakened due to 

deterioration or fatigue). For existing buildings, a two-step procedure 

for evaluating the risk from windstorms (other than tornadoes) is also 

recommended.

Step 1: Calculate the wind loads on the building using the current edition of ASCE 7, and compare these loads with the loads for which the 

building was originally designed. The original design loads may be 

noted on the contract drawings. If not, calculate the loads using the 

code or standard to which the building was designed and constructed. 

If the original design loads are significantly lower than current wind 

loads, upgrading the load resistance of the building envelope and/or 

structure should be considered (see Section 6.2.4.2). An alternative to 

comparing current loads with original design loads is to evaluate the 

resistance of the existing facility as a function of the current wind loads 

to determine what elements are highly overstressed.

Step 2: Perform a field investigation to evaluate the primary building 

envelope elements, rooftop equipment, and structural system elements, 

to determine if the school was generally constructed as indicated on the 

original contract drawings. As part of the investigation, the primary elements should be checked for deterioration. Load path continuity should 

also be checked.

As part of Steps 2 and 3, consider the 

availability of other schools or buildings 

in the community that could be used for 

educational purposes (and emergency 

response if the school is so designated) in 

the event that the school is damaged. For 

example, in an isolated community, the 

school may be the only facility available 

for education and/or emergency response, 

in which case loss of school use would 

be very serious. In this scenario, the 

enhancements given in Sections Sections 

6.3.1.5, 6.3.2.2, 6.3.3.3, 6.3.3.5, 6.3.3.7, 

6.3.4.2, 6.3.4.4, 6.3.5, and 6.3.6 should be 

followed and some of the enhancements 

should be even more robust.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

The above evaluations will allow development of a vulnerability assessment that can be used along with the site’s wind characteristics to assess 

the risk. If the results of either step indicate the need for remedial work, 

see Section 6.4. 

6.2.4.3 Portable Classrooms

Unless portable classrooms are designed and constructed (including anchorage to the ground—see Figure 6-27) to meet the same wind loads 

as the main school building, students and faculty should be considered 

at risk during high winds. Therefore, portable classrooms should not be 

occupied when high winds are forecast (even though the forecast speeds 

are well below design wind conditions for the main building). Also, during winds that are well below design wind conditions, wind-borne debris 

from disintegrating portable classrooms could impact and damage the 

main school building and/or nearby residences (Figure 6-28).

Figure 6-27: 

Unlike the portable 

classroom shown in 

Figure 6-22, with the 

thick T-shaped plates 

and taut turnbuckles, 

this portable classroom 

has a robust anchorage 

to the ground. Hurricane 

Francis (Florida, 2004)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-28: 

Asphalt shingles and 

vinyl siding blew off of 

this portable classroom. 

This type of windborne debris can break 

unprotected glazing. 

Hurricane Francis 

(Florida, 2004)

6.3 Requirements and Best Practices in 

High-Wind Regions

T he performance of schools in past wind storms indicates that the 

most frequent and the most significant factor in the disruption of 

the operations of these facilities has been the failure of nonstructural building components. While acknowledging the importance of the 

structural systems, Chapter 6 emphasizes the building envelope components and the nonstructural systems. According to National Institute 

of Building Sciences (NIBS), the building envelope includes the belowgrade basement walls and foundation and floor slab (although these are 

generally considered part of the building’s structural system). The envelope includes everything that separates the interior of a building from the 

outdoor environment, including the connection of all the nonstructural elements to the building structure. The nonstructural systems include 

all mechanical, electrical, electronic, communications, and lightning 

protection systems. Historically, damage to roof coverings and rooftop 

equipment has been the leading cause of building performance problems 

during windstorms. Special consideration should be given to the problem 

of water infiltration through failed building envelope components, which 

can cause severe disruptions in the functioning of schools. 

The key to enhanced wind performance is paying sufficient attention to 

all phases of the construction process (including site selection, design, 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

and construction) and to post-occupancy maintenance and repair. Of 

course, the school district must first budget sufficient funds for these efforts (see Sections 6.2.2.2 and 6.2.3.2). 

School Design Considerations In Hurricane-Prone Regions 

Following the general design and construction recommendations, this 

manual presents recommendations specific to schools located in hurricane-prone regions. These recommendations are additional to the 

ones presented for schools located outside of hurricane-prone regions, and in many cases supersede 

those recommendations. Schools located in hurricane-prone regions require special design and 

construction attention because of the unique characteristics of this type of windstorm. Hurricanes 

can bring very high winds that last for many hours, 

which can lead to material fatigue failures. The 

variability of wind direction increases the probability that the wind will approach the building at the most critical angle. 

Hurricanes also generate a large amount of wind-borne debris, which 

can damage various building components and cause injury and death. 

In order to ensure continuity of service during and after hurricanes, the 

design, construction, and maintenance of schools should be very robust 

to provide sufficient resiliency to withstand the effects of hurricanes.

6.3.1 General School Design Considerations

6.3.1.1 Site

When selecting land for a school, sites located in Exposure D (see ASCE 

7 for exposure definitions) should be avoided if possible. Selecting a site 

in Exposure C or preferably in Exposure B decreases the wind loads. 

Also, where possible, avoid selecting sites located on an escarpment or 

the upper half of a hill, where the abrupt change in the topography 

would result in increased wind loads.12

Trees with trunks larger than 6 inches in diameter, poles (e.g., light 

fixture poles, flagpoles, and power poles), or towers (e.g., electrical transmission and large communication towers) should not be placed near the 

building. Falling trees, poles, and towers can severely damage a school 

and injure the occupants. Large trees can crash through pre-engineered 

metal buildings and wood frame construction (see Figure 6-29). Falling 

trees can also rupture roof membranes and break windows.

12 When selecting a site on an escarpment or the upper half of a hill is necessary, the ASCE 

7 design procedure accounts for wind speed-up associated with this abrupt change in 

topography.

Designing a portion of a school to be used 

as a safe room requires the designer to 

consider additional design criteria beyond 

what is presented in this chapter. To find the 

design criteria for a safe room in a school, 

refer to FEMA 361 and Section 6.5 of this 

document.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Street signage should be designed to resist the design wind loads so that 

toppled signs do not block access roads or become wind-blown debris. 

AASHTO LTS-4-5 provides guidance for determining wind loads on 

highway signs. 

Providing at least two means of site egress is prudent for all schools, but 

is particularly important for schools in hurricane-prone regions. If one 

route becomes blocked by trees or other debris, or by floodwaters, the 

other access route may still be available.

To the extent possible, site portable classrooms so that, if they disintegrate during a storm that approaches from the prevailing wind direction, 

debris will avoid impacting the main school building and residences. 

Debris can travel in excess of 300 feet. Destructive winds from hurricanes 

and tornadoes can approach from any direction. These storms can also 

throw debris much farther.

Figure 6-29: 

This fallen tree caused 

minor damage to these 

portable classrooms. 

However, had the 

tree landed on the 

classroom at the left of 

the photograph, it could 

have caused injuries if 

the building had been 

occupied. Although 

portable classrooms 

are not occupied during 

hurricanes, they are 

frequently occupied 

during thunderstorms, 

which often topple 

trees. Estimated wind 

speed: 105 to 115 mph. 

Hurricane Ivan (Florida, 

2004)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.3.1.2 School Design

Good wind performance depends on good design 

(including details and specifications), materials, installation, maintenance, and repair. A significant 

shortcoming in any of these five elements could 

jeopardize the performance of a school against 

wind. Design, however, is the key element to achieving good performance of a building against wind 

damage. Design inadequacies frequently cannot 

be compensated for with other elements. Good 

design, however, can compensate for other inadequacies to some extent. The following steps should 

be included in the design process for schools.

Step 1: Calculate Loads

Calculate loads on the MWFRS, the building envelope, and rooftop equipment in accordance with 

the latest edition of ASCE 7 or the local building 

code, whichever procedure results in the highest 

loads. In calculating wind loads, design professionals should consider the following items. 

Risk Category:  This manual recommends that 

all schools be classified as Risk Category III or IV 

buildings.

Wind directionality factor:  The ASCE 7 wind load 

calculation procedure incorporates a wind directionality factor (Kd). The directionality factor 

accounts for the reduced probability of maximum 

winds coming from any given direction. By applying the prescribed value of 0.85, the loads are 

reduced by 15 percent. Because hurricane winds 

can come from any direction, and because of 

the historically poor performance of building 

envelopes and rooftop equipment, this manual 

recommends a more conservative approach for 

schools in hurricane-prone regions. A directionality factor of 1.0 is recommended for the building 

envelope and rooftop equipment (a load increase 

over what is required by ASCE 7). For the MWFRS, 

a directionality factor of 0.85 is recommended 

(hence, no change for MWFRS).

For assistance in applying the provisions 

of ASCE 7, refer to the Applied Technology 

Council’s (ATC) Design Guide 2, Basic 

Wind Engineering for Low-Rise Buildings. 

Topics include how to determine mean roof 

height for various building shapes, how to 

determine the building exposure, how to 

determine a building’s enclosure category, 

and how to apply loads using the three analytical methods given in ASCE 7 in order 

to help the user understand the differences 

in and the sensitivities to these methods. 

This Guide is based on the 2005 edition of 

ASCE 7. A future edition of the Guide will 

be based on the 2010 edition of ASCE 7.

In the past, design professionals seldom 

performed load calculations on the building envelope (i.e., roof and wall coverings, 

doors, windows, and skylights) and rooftop 

equipment. These building components 

are the ones that have failed the most 

during past wind events. In large part, they 

failed because of the lack of proper load 

determination and inappropriate design of 

these elements. It is imperative that design 

professionals determine the loads for the 

building envelope and rooftop equipment, 

and design them to accommodate such 

loads.

The design wind loads for a Risk Category 

III or IV building are 15 percent greater 

than for Category II building. This load 

increase is intended to make Category III 

and IV buildings more capable of resisting 

the wind pressures induced by stronger, 

rarer hurricanes than Category II buildings.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Step 2: Determine Load Resistance 

When using allowable stress design, after loads 

have been determined, it is necessary to determine a reasonable safety factor in order to select 

the minimum required load resistance. For building envelope systems, a minimum safety factor of 2 

is recommended. For anchoring exterior-mounted mechanical, electrical, and communications 

equipment (such as satellite dishes), a minimum 

safety factor of 3 is recommended. When using 

allowable stress design, refer to the load combinations specified in ASCE 7. When using strength 

design, load combinations and load factors specified in ASCE 7 are used. 

For structural members and cladding elements 

where strength design can be used, load resistance 

can be determined by calculations. For other elements where allowable stress design is used (such 

as most types of roof coverings), load resistance is 

primarily obtained from system testing. 

The load resistance criteria need to be provided in 

contract documents. For structural elements, the 

designer of record typically accounts for load resistance by indicating the material, size, spacing, and 

connection of the elements. For nonstructural elements, such as roof coverings or windows, the load 

and safety factor can be specified. In this case, the 

specifications should require the contractor’s submittals to demonstrate that the system will meet the 

load resistance criteria. This performance specification approach is necessary if, at the time of the 

design, it is unknown who will manufacture the 

system. 

Regardless of which approach is used, it is important that the designer of record ensure that it can 

be demonstrated, via calculations or tests, that the 

structure, building envelope, and nonstructural 

systems (exterior-mounted mechanical, electrical, 

and communications equipment) have sufficient 

strength to resist design wind loads. 13

13 If the 2005 or earlier edition of ASCE 7 is used, the design wind load prior to application of 

Uplift loads on roof assemblies can also 

be determined from FM Global (FMG) 

Data Sheets (dates vary). If the school is 

FMG insured, and the FMG-derived loads 

are higher than those derived from ASCE 

7 or the building code, the FMG loads 

should govern. However, if the ASCE 7 or 

code-derived loads are higher than those 

from FMG, the ASCE 7 or code-derived 

loads should govern (whichever procedure 

results in the highest loads).

When using allowable stress design, a 

safety factor is applied to account for 

reasonable variations in material strengths, 

construction workmanship, and conditions 

when the actual wind speed somewhat 

exceeds design wind speed. For design 

purposes, the ultimate resistance an assembly achieves in testing is reduced by 

the safety factor. For example, if a roof 

assembly resisted an uplift pressure of 100 

pounds per square foot (psf), after applying 

a safety factor of 2, the assembly would 

be suitable where the design load after application of the load combination reduction 

factor was 50 psf or less.13 Conversely, if 

the design load after application of the load 

combination is known, multiplying it by the 

safety factor equals the minimum required 

test pressure (e.g., 50 psf design load 

multiplied by a safety factor of 2 equals a 

minimum required test pressure of 100 psf).

Even if a school (or portion thereof) is 

hardened for improved wind resistance 

and damage reduction, the facility will not 

provide hurricane or tornado life-safety 

protection unless it has been designed and 

constructed to meet the criteria in FEMA 

361 or the ICC 500. See Section 6.5.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Step 3: Detailed Design

It is vital to design, detail, and specify the structural system, building envelope, and exterior-mounted mechanical, electrical, and communications 

equipment to meet the factored design loads (based on appropriate analytical or test methods). It is also vital to respond to the risk assessment 

criteria discussed in Section 6.2.4, as appropriate.

As part of the detailed design effort, load path continuity should be 

clearly indicated in the contract documents via illustration of connection 

details. Load paths need to accommodate design uplift, racking, and 

overturning loads. Load path continuity obviously applies to MWFRS elements, but it also applies to building envelope elements. Figure 6-30 

shows load path discontinuities within a roof covering system. In this system, metal roof panels were attached to plywood, which was attached to 

4x4 nailers running cross-slope. These top nailers were attached to 4x4 

nailers that ran up-slope. The top nailers were inadequately attached to 

the bottom nailers and the bottom nailers were inadequately attached 

to the roof structure. To effectively attach the top nailer to the bottom 

nailer, high-strength connectors such as metal framing connectors are 

needed. To effectively attach the bottom nailers, a variety of fasteners 

may be used, provided a sufficient number are used.

the load combination factor is used.

Connections are a key aspect of load path continuity between various structural and nonstructural 

building elements. In a window, for example, the glass must be strong enough to resist the wind 

pressure and must be adequately anchored to the window frame, the frame adequately anchored to 

the wall, the wall to the foundation, and the foundation to the ground. As loads increase, greater load 

capacity must be developed in the connections.

Figure 6-30: 

In most of the areas on 

this roof, the connection 

of the top nailer to the 

bottom nailer was the 

weakest link. However, 

in a few locations, 

the connection of the 

bottom nailer to the roof 

structure was the weak 

link (three of the blownoff bottom nailers are 

shown by the red lines). 
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-31 illustrates the load path concept. Members are sized to accommodate the design loads. Connections are designed to transfer uplift 

loads applied to the roof, and the positive and negative loads applied to 

the exterior bearing walls, down to the foundation and into the ground. 

The roof covering (and wall covering, if there is one) is also part of the 

load path. To avoid blow-off, the nonstructural elements must also be adequately attached to the structure.

Figure 6-31: 

Illustration of load path 

continuity
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

As part of the detailed design process, special consideration should be 

given to the durability of materials and water infiltration.

Durability: Because some locales have very aggressive atmospheric corrosion (such as areas near oceans), special attention needs to be given to 

the specification of adequate protection for ferrous metals, or to specify 

alternative metals such as stainless steel. FEMA TB-8, Corrosion Protection 

for Metal Connectors in Coastal Areas (1996), contains information on corrosion protection. Attention also needs to be given to dry rot avoidance, 

for example, by specifying preservative-treated wood or developing details that avoid excessive moisture accumulation. Appendix J of FEMA 

55, Coastal Construction Manual (2000), presents information on wood 

durability. Note: An updated version of FEMA 55 is expected to be released in 2011.

Durable materials are particularly important for components that are 

inaccessible and cannot be inspected regularly (such as fasteners used 

to attach roof insulation). Special attention also needs to be given to details. For example, details that do not allow water to stand at connections 

or sills are preferred. Without special attention to material selection and 

details, the demands on maintenance and repair will be increased, along 

with the likelihood of failure of components during high winds.

Water infiltration (rain):  Although prevention of building collapse and 

major building damage is the primary goal of wind-resistant design, 

consideration should also be given to minimizing water damage and subsequent development of mold from the penetration of wind-driven rain. 

To the extent possible, non-load-bearing walls and door and window 

frames should be designed in accordance with rain-screen principles. 

With this approach, it is assumed that some water will penetrate past the 

face of the building envelope. The water is intercepted in an air-pressure 

equalized cavity that provides drainage from the cavity to the outer surface of the building. See Sections 6.3.3.1 and 6.3.3.4, and Figure 6-52 for 

further discussion and an example. 

In conjunction with the rain-screen principle, it is desirable to avoid using sealant as the first or only line of defense against water infiltration. 

When sealant joints are exposed, obtaining long-lasting watertight performance is difficult because of the complexities 

of sealant joint design and installation (see Figure 

6-52, which shows the sealant protected by a removable stop).

Further information on the rain-screen principle can be found in the National Institute 

of Building Sciences’ Building Envelope 

Design Guide (www.wbdg.org/design/

envelope.php).
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Step 4: Peer Review 

If the design team’s wind expertise and experience is limited, wind design 

input and/or peer review should be sought from a qualified individual. 

The design input or peer review could be arranged for the entire building, or for specific components such as the roof or 

glazing systems, that are critical and beyond the design team’s expertise. 

Regardless of the design team’s expertise and experience, peer review should be considered when 

a school:

n is located in an area where the basic wind speed is greater than 120 

mph (peak gust)14

n will be used for emergency response after a storm

n will be used for a hurricane shelter

n will incorporate a hurricane or tornado safe room or shelter 

6.3.1.3 Construction Contract Administration

After a suitable design is complete, the design team should endeavor to 

ensure that the design intent is achieved during construction. The key 

elements of construction contract administration are submittal reviews 

and field observations, as discussed below.

Submittal reviews:  The specifications need to stipulate the submittal 

requirements. This includes specifying what systems require submittals 

(e.g., windows) and test data (where appropriate). Each submittal should 

demonstrate the development of a load path through the system and 

into its supporting element. For example, a window submittal should 

show that the glazing has sufficient strength, its attachment to the frame 

is adequate, and the attachment of the frame to the wall is adequate.

During submittal review, it is important for the designer of record to 

be diligent in ensuring that all required documents are submitted and 

that they include the necessary information. The submittal information 

needs to be thoroughly checked to ensure its validity. For example, if an 

approved method used to demonstrate compliance with the design load 

has been altered or incorrectly applied, the test data should be rejected, unless the contractor can demonstrate the test method was suitable. 

Similarly, if a new test method has been developed by a manufacturer or 

the contractor, the contractor should demonstrate its suitability.

14 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. 

If ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph.

When a room or portion of a school has 

been design per FEMA 361 to function 

as a safe room with an occupancy of 50 

persons or more, a peer review must be 

performed for the safe room.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Field observations:  It is recommended that the design team analyze 

the design to determine which elements are critical to ensuring highwind performance. The analysis should include the structural system 

and exterior-mounted electrical equipment, but it should focus on the 

building envelope and exterior-mounted mechanical and communications equipment. After determining the list of critical elements to be 

observed, observation frequency and the need for special inspections 

by an inspection firm should be determined. Observation frequency 

and the need for special inspections will depend on the magnitude of 

the results of the risk assessment described in Section 6.2.4, the complexity of the facility, and the competency of the general contractor, 

subcontractors, and suppliers.

6.3.1.4 Post-Occupancy Inspections, Periodic Maintenance, Repair, 

and Replacement

The design team should advise the school administration of the importance of periodic inspections, 

maintenance, and timely repair. It is important 

for the administration to understand that a facility’s wind resistance will degrade over time due to 

exposure to weather unless it is regularly maintained and repaired. The goal should be to repair 

or replace items before they fail in a storm. This 

approach is less expensive than waiting for failure 

and then repairing the failed components and 

consequential damage. 

The building envelope and exterior-mounted equipment should be 

inspected once a year by persons knowledgeable of the systems/materials they are inspecting. Items that require maintenance, repair, or 

replacement should be documented and scheduled for work. For example, the deterioration of glazing is often overlooked. After several 

years of exposure, scratches and chips can become extensive enough 

to weaken the glazing. Also, if an engineered film was surface-applied 

to glazing for wind-borne debris protection, the film should be periodically inspected and replaced before it is no longer effective.

Prior to hurricane landfall, a special roof inspection is recommended. Remove debris 

and other items that are not anchored so 

that they do not become wind-borne debris. 

Also, clean roof drains and sumps so that 

their drainage capacity is not impaired (see 

Figure 6-32). Lack of debris maintenance 

can lead to clogging. If overflow drains or 

scuppers are also clogged, roof collapse 

may occur. 
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

A special inspection is recommended following unusually high winds 

(such as a thunderstorm with wind speeds of 70 mph peak gust or 

greater). The purpose of the inspection is to assess whether the storm 

caused damage that needs to be repaired to maintain building strength 

and integrity. In addition to inspecting for obvious signs of damage, 

the inspector should determine if cracks or other openings have developed that may allow water infiltration, which could lead to corrosion 

or dry rot of concealed components.

6.3.1.5 Site and General Design Considerations in Hurricane-Prone

Regions 

Via ASCE 7, the 2009 edition of the IBC has only two special wind-related provisions pertaining to schools in hurricane-prone regions. One 

pertains to glazing protection within wind-borne debris regions (as defined in ASCE 7). The other provision pertains to schools that will be 

used as hurricane evacuation shelters. If used as shelters, schools must 

be designed as Risk Category IV buildings. These are the only hurricanerelated school requirements currently in the IBC. These two additional 

requirements do not provide adequate protection of occupants of a 

school during a hurricane, nor do they ensure a school will be functional after a hurricane. Further, a school may comply with IBC, but still 

remain vulnerable to water and missile penetration through the roof 

or walls. To mitigate this water and missile vulnerability, see Sections 

6.3.2.2, 6.3.3.3, 6.3.3.5, and 6.3.3.7.

Figure 6-32: 

Dirt and vegetation 

surrounded this roof 

drain (red arrow) and 

impeded drainage. 

Roof drains should 

be checked at least 

annually and cleaned of 

debris if found. Drains 

should also be checked 

prior to hurricane 

landfall. Hurricane Ike 

(Texas, 2008)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

During the design phase, the architect should determine from the school 

district whether or not the school will be designated or used as a hurricane evacuation shelter. If it will be used as a shelter, see Section 6.5 for 

design recommendations. 

The following recommendations are made regarding siting:

n Locate poles, towers, and trees with trunks larger than 6 inches in diameter away from primary site access roads so that they do not block 

access to, or hit, the facility if toppled.

n Determine if existing buildings within 1,500 feet of the new facility have aggregate surfaced roofs. If roofs with aggregate surfacing 

are present, it is recommended that the aggregate be removed to 

prevent it from impacting the new facility. Aggregate removal may 

necessitate reroofing or other remedial work in order to maintain 

the roof’s fire or wind resistance.

n In cases where a building on a school campus will be used as a hurricane safe room or shelter, if there are multiple buildings on campus, 

it is recommended that enclosed walkways be designed to connect 

the buildings. The enclosed walkways (aboveor below-grade) are particularly important for 

protecting people moving between buildings 

during a hurricane if it becomes necessary to 

evacuate occupants from one building to another (see Figure 6-33).

Publication 4496 by the American Red 

Cross (ARC, 2002), Standards for 

Hurricane Evacuation Shelter Selection, 

provides information regarding assessing 

existing buildings for use as hurricane shelters. Unless a school has been specifically 

designed for use as a safe room or shelter, 

it should only be used as a last resort and 

only if the school meets the criteria given 

in ARC 4496.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

6.3.2 Structural Systems

6.3.2.1 Design Parameters for Structural Systems

Based on post-storm damage evaluations, with the exception of canopies 

and strong and violent tornado events, the structural systems (i.e., MWFRS 

and structural components such as roof decking) of schools have typically performed quite well during design wind events. There have, however, 

been notable exceptions; in these cases, the most common problem 

has been blow-off of the roof deck, but instances of collapse have also 

been documented (Figures 6-18, 6-21, 6-24, 6-26, and 6-34). The structural problems have primarily been caused by lack of an adequate load 

path, with connection failure being a common occurrence. Problems 

have also been caused by reduced structural capacity due to termites, 

workmanship errors (commonly associated with steel decks attached by 

puddle welds), and limited uplift resistance of deck connections in roof 

perimeters and corners (due to lack of code-required enhancement in 

older editions of the model codes).

Figure 6:33: 

Open walkways do not 

provide protection from 

wind-borne debris. 

Hurricane Katrina 

(Mississippi, 2005).
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

With the exception of strong and violent tornado events, structural 

systems designed and constructed in accordance with the IBC should 

typically offer adequate wind resistance, provided attention was given to 

load path continuity and to the durability of building materials (with 

respect to corrosion and termites). However, the greatest reliability is 

offered by cast-in-place concrete. There are no known reports of any castin-place concrete buildings experiencing a significant structural problem 

during wind events, including the strongest hurricanes (Category 5) and 

tornadoes (EF5). 

The following design parameters are recommended for structural 

systems:

n If a pre-engineered metal building is being contemplated, special 

steps should be taken to ensure the structure has more redundancy than is typically the case with pre-engineered buildings.15 Steps 

should be taken to ensure the structure is not vulnerable to progressive collapse in the event a primary bent (steel moment frame) is 

compromised or bracing components fail.

n Exterior load-bearing walls of masonry or precast concrete should 

be designed to have sufficient strength to resist external and internal loading when analyzed as C&C. CMU walls should have 

vertical and horizontal reinforcing and grout to resist wind loads. 

15 The structural system of pre-engineered metal buildings is composed of rigid steel frames, 

secondary members (including roof purlins and wall girts made of Z- or C-shaped members), 

and bracing.

Figure 6-34: 

The structure on 

this school was 

composed of light 

gauge metal framing, 

with a proprietary 

composite deck system 

composed of light gauge 

corrugated metal deck 

and gypsum board. 

In addition to the 

gable end wall failure, 

the asphalt shingles 

and underlayment 

were blown off at the 

corner of the eave and 

ridge. Estimated wind 

speed: 140 to 160 

mph. Hurricane Charley 

(Florida, 2004)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

The connections of precast concrete wall panels should be designed 

to have sufficient strength to resist wind loads.

n For roof decks, concrete, steel, plywood, or oriented strand board 

(OSB) is recommended. 

n For steel roof decks, it is recommended that a screw attachment be

specified, rather than puddle welds or powder-driven pins. Screws are 

more reliable and much less susceptible to workmanship problems, as 

illustrated by Figure 6-35. These roof joists and decking blew off and 

landed several feet from the building. The decking was attached with 

closely-spaced screws. Because of the strength and reliability of the 

screwed connections, the decking remained attached to the joists. 

Figure 6-36 shows decking that was attached with puddle welds. At most 

of the welds, there was only superficial bonding of the metal deck to 

the joist. Only a small portion of the deck near the center of the weld 

area (as delineated by the circle) was well fused to the joist. Figures 6-37 

and 6-38 show problems with acoustical decking attached with powderdriven pins. The pin shown on the left of Figure 6-38 is properly seated. 

However, the pin at the right did not penetrate far enough into the steel 

joist below. 

Figure 6-35: 

Even though the 

roof structure blew 

off, because of the 

strength and reliability 

of the screwed deck 

connections, the decking 

remained attached to 

the joists. Hurricane 

Charley (Florida, 2004)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

n For attaching wood-sheathed roof decks, screws, ring-shank, or 

screw-shank nails are recommended in the corner regions of the 

roof. Where the basic wind speed is greater than 120 mph, these 

types of fasteners are also recommended for the perimeter regions 

of the roof.16

16 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph.

Figure 6-36: 

View looking down at 

the top of a steel joist 

after the metal decking 

blew away. Only a small 

portion of the deck was 

well fused to the joist 

(circled area). Tornado 

(Oklahoma, 1999)

Figure 6-37: 

Looking down at a sidelap of a deck attached with 

powder-driven pins. The washer at the top pin blew 

through the deck.

Figure 6-38: 

View looking along a sidelap of a deck attached 

with powder-driven pins. The right pin does not 

provide adequate uplift and shear resistance.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

n For precast concrete decks it is recommended that the deck connections be designed to resist the design uplift loads because the deck 

dead load itself is often insufficient to resist the uplift. The deck in 

Figure 6-39 had bolts to provide uplift resistance; however, anchor 

plates and nuts had not been installed. Without the anchor plates, the 

dead load of the deck was insufficient to resist the wind uplift load.

n For precast Tee decks, it is recommended that the reinforcing be 

designed to accommodate the uplift loads in addition to the gravity loads. Otherwise, large uplift forces can cause member failure 

due to the Tee’s own pre-stress forces after the uplift load exceeds 

the dead load of the Tee. This type of failure occurred at one of the 

roof panels shown in Figure 6-40, where a panel lifted because of the 

combined effects of wind uplift and pre-tension. Also, because the 

connections between the roof and wall panels provided very little 

uplift load resistance, several other roof and wall panels collapsed.

n For buildings that have mechanically attached single-ply or modified 

bitumen membranes, designers should refer to the decking recommendations presented in the Wind Design Guide for Mechanically 

Attached Flexible Membrane Roofs, B1049 (National Research Council 

of Canada, 2005).

If an FMG-rated roof assembly is specified, the roof deck also needs to 

comply with the FMG criteria. See text box about FM Global in Section 

6.3.3.6.

Figure 6-39: 

Portions of this waffled 

precast concrete roof 

deck were blown off. 

Typhoon Paka (Guam, 

1997)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Walkway and entrance canopies are often damaged during high winds 

(see Figure 6-41). Wind-borne debris from damaged canopies can damage nearby buildings and injure people; hence, these elements should 

also receive design and construction attention. 

Figure 6-40: 

Twin-Tee roof panel 

lifted as a result of 

the combined effects 

of wind uplift and 

pre-tension. Tornado 

(Missouri, May 2003) 

Figure 6-41: 

The wind speed was 

sufficient to collapse 

this school’s canopy, 

but the speed was not 

high enough to blow 

the canopy debris very 

far. Hurricane Francis 

(Florida, 2004) 
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

6.3.2.2 Design Parameters for Structural Systems in Hurricane-Prone 

Regions

Because of the exceptionally good wind performance and wind-borne 

debris resistance that reinforced cast-in-place concrete structures offer, 

a reinforced concrete roof deck and reinforced concrete or reinforced 

and fully grouted CMU exterior walls are recommended as follows: 

Roof deck: A minimum 4-inch thick cast-in-place reinforced concrete 

deck is the preferred deck. Other recommended decks are minimum 4-inch thick structural concrete topping over steel decking, 

and precast concrete with an additional minimum 4-inch structural 

concrete topping. With these deck types, deck 

blow-off or penetration by wind-borne debris is highly unlikely, thus avoiding water 

infiltration (when combined with the roof system recommendations given in Section 6.3.3.7). 

Figure 6-42 illustrates the type of damage that can 

occur to other types of decks impacted by large 

momentum debris. 

Exterior load-bearing walls: A minimum 6-inch thick, cast-in-place concrete wall reinforced with #4 rebars at 12 inches on center each way is the 

preferred wall. Other recommended walls are a minimum 8-inch thick, 

fully grouted CMU reinforced vertically with #4 rebars at 16 inches on 

center, and precast concrete that is a minimum 6-inches thick and reinforced equivalent to the recommendations for cast-in-place walls.

ASCE 7-05 provides pressure coefficients for open canopies of various slopes (referred to as “free 

roofs” in ASCE 7). The free roof figures for MWFRS in ASCE 7-05 (Figures 6-18A to 6-18D) include 

two load cases, Case A and Case B. While there is no discussion describing the two load cases, 

they pertain to fluctuating loads and are intended to represent upper and lower limits of instantaneous wind pressures. Loads for both cases must be calculated to determine the critical loads. 

Figures 6-18A to 6-18C are for a wind direction normal to the ridge. For wind direction parallel to 

the ridge, use Figure 6-18D in ASCE 7-05. 

In ASCE 7-10, Commentary Section C27.4.3 was revised to include discussion of the two load 

cases. The Commentary was also expanded to include discussion about “clear wind flow” and 

“obstructed wind flow,” which pertains to storage of goods or materials under the free roof (which 

restrict wind flow).

If precast concrete is used for the roof 

or wall structure, the connections should 

be carefully designed, detailed, and 

constructed.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.3.3 Building Envelope

The following section highlights the design considerations for building 

envelope components that have historically sustained the greatest and 

most frequent damage in high winds.

The design considerations for building envelope components of schools 

in hurricane-prone regions include a number of additional recommendations. The principal concern that should be addressed is the additional 

risk from wind-borne debris and water leakage. Design considerations 

specific to hurricane-prone regions are discussed in Sections 6.3.3.3, 

6.3.3.5, and 6.3.3.7. Design guidance for building envelope components 

of safe rooms within schools is addressed in Section 6.5.

6.3.3.1 Exterior Doors

This section addresses primary and secondary egress doors, sectional 

(garage) doors, and rolling doors. Although blow-off of personnel doors 

is uncommon, it can cause serious problems. Blown-off doors allow entrance of rain and tumbling doors can damage buildings and cause 

injuries. 

Figure 6-42: 

At the school shown 

in Figure 6-34, windborne debris ruptured 

the proprietary 

composite deck system 

composed of light 

gauge corrugated 

metal deck and gypsum 

board. Estimated wind 

speed: 140 to 160 

mph. Hurricane Charley 

(Florida, 2004)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Although many schools do not have sectional or 

rolling doors, blow-off of these types of doors is 

quite common. These failures are typically caused 

by the use of door and track assemblies that have 

insufficient wind resistance, or by inadequate attachment of the tracks or nailers to the wall. 

Loads and Resistance

The IBC requires that the door assembly (i.e., door, hardware, frame, 

and frame attachment to the wall) be of sufficient strength to resist the 

positive and negative design wind pressure. Design 

professionals should require that doors comply 

with wind load testing in accordance with ASTM E 

1233. Design professionals should also specify the 

attachment of the door frame to the wall (e.g., type, 

size, spacing, and edge distance of frame fasteners). 

For sectional and rolling doors attached to wood 

nailers, design professionals should also specify the 

attachment of the nailer to the wall.

Water Infiltration

Heavy rain that accompanies high winds (e.g., thunderstorms, tropical 

storms, and hurricanes) can cause significant wind-driven water infiltration problems. The magnitude of the problem increases with the wind 

speed. Leakage can occur between the door and its frame, the frame and 

the wall, and between the threshold and the door. When wind speeds 

approach 165 mph, some leakage should be anticipated because of the 

very high wind pressures and numerous opportunities for leakage path 

development.17

The following recommendations should be considered to minimize infiltration around exterior doors. 

Vestibule:  Adding a vestibule allows both the inner and outer doors 

to be equipped with weatherstripping. The vestibule can be designed 

with water-resistant finishes (e.g., concrete or tile) and the floor can 

be equipped with a drain. In addition, installing 

exterior threshold trench drains can be helpful 

(openings must be small enough to avoid trapping high-heeled shoes). Note that trench drains 

do not eliminate the problem, since water can still 

penetrate at door edges.

17 The 165-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 120 mph.

For further general information on doors, 

see “Fenestration Systems” in the National 

Institute of Building Sciences’ Building 

Envelope Design Guide (www.wbdg.org/

design/envelope.php).

For design guidance on attachment of 

door frames, see Technical Data Sheet 

#161, Connecting Garage Door Jambs 

to Building Framing, published by the 

Door & Access Systems Manufacturers 

Association, 2003 (revised May 2008). 

Available at www.dasma.com.

Where corrosion is problematic, anodized 

aluminum or galvanized doors and frames, 

and stainless steel frame anchors and 

hardware are recommended. 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Door swing:  Out-swinging doors have weatherstripping on the interior side of the door, where 

it is less susceptible to degradation, which is an 

advantage when compared to in-swinging doors. 

Some interlocking weatherstripping assemblies 

are available for out-swinging doors.

The successful integration of the door frame and 

the wall is a special challenge when designing 

doors. See Section 6.3.3.2 for discussion of this 

juncture. 

ASTM E 2112 provides information pertaining to 

the installation of doors, including the use of sill 

pan flashings with end dams and rear legs (see 

Figure 6-43). It is recommended that designers 

use ASTM E 2112 as a design resource.

Weatherstripping

A variety of pre-manufactured weatherstripping 

components is available, including drips, door 

shoes and bottoms, thresholds, and jamb/head 

weatherstripping. 

Drips: These are intended to shed water away from the opening between 

the frame and the door head, and the opening between the door bottom and the threshold (see Figures 6-44 and 6-45). Alternatively, a door 

sweep can be specified (see Figure 6-45). For high-traffic doors, periodic 

replacement of the neoprene components will be necessary.

Rear leg End dam

Turned down

front leg

Figure 6-43: 

Door sill pan flashing with end dams, rear leg, and 

turned-down front leg

Drip

Door Door

Drip

with 

hook

Figure 6-44: 

Drip at door head and 

drip with hook at head

For primary swinging entry/exit doors, 

exit door hardware is recommended to 

minimize the possibility of the doors being 

pulled open by wind suction. Exit hardware 

with top and bottom rods is more secure 

than exit hardware that latches at the jamb.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Door shoes and bottoms: These are intended to minimize the gap between 

the door and the threshold. Figure 

6-45 illustrates a door shoe that incorporates a drip. Figure 6-46 illustrates an 

automatic door bottom. Door bottoms 

can be surface-mounted or mortised. 

For high-traffic doors, periodic replacement of the vinyl or neoprene 

components will be necessary.

Thresholds: These are available to suit 

a variety of conditions. Thresholds 

with high (e.g., 1-inch) vertical offsets 

offer enhanced resistance to wind-driven water infiltration. However, the 

offset is limited where the thresholds are required to comply with the 

Americans with Disabilities Act (ADA), or at high-traffic doors. At other 

doors, high offsets are preferred. 

Thresholds can be interlocked with the door (see Figure 6-47), or thresholds can have a stop and seal (see Figure 6-48). In some instances, the 

threshold is set directly on the floor. Where this is appropriate, setting 

the threshold in butyl sealant is recommended to avoid water infiltration 

between the threshold and the floor. In other instances, the threshold 

is set on a pan flashing (as previously discussed in this section). If the 

threshold has weep holes, specify that the weep holes not be obstructed 

during construction (see Figure 6-47).

Figure 6-45: 

Door shoe with drip 

and vinyl seal (left); 

neoprene door sweep 

(right)

Door Door

Neoprene

Door

Neoprene

Figure 6-46: 

Automatic door bottom
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Adjustable jamb/head weatherstripping:  This type of weatherstripping 

is recommended because the wide 

sponge neoprene offers good contact with the door (see Figure 6-49). 

The adjustment feature also helps to 

ensure good contact, provided the 

proper adjustment is maintained.

Meeting stile:  At the meeting stile of 

pairs of doors, an overlapping astragal 

weatherstripping offers greater protection than weatherstripping that does 

not overlap. 

6.3.3.2 Windows and Skylights

This section addresses general design considerations for exterior windows and skylights. For additional information on windows and skylights 

located in hurricane-prone regions, see Section 6.3.3.3.

Loads and Resistance

The IBC requires that windows, curtain walls, and 

skylight assemblies (i.e., the glazing, frame, and 

frame attachment to the wall or roof) have sufficient strength to resist the positive and negative 

design wind pressure (see Figure 6-50). Design 

professionals should specify that these assemblies 

Figure 6-47: 

Interlocking threshold with drain pan

Sweep

The threshold

should be set in

butyl sealant. If a 

drain pan exists

underneath the 

threshold, weep

holes should not 

be blocked with 

sealant or debris.

Neoprene 

Seal

Door

Weep

Weep

Drip

Pan

The threshold

should be set in

butyl sealant. If a 

drain pan exists

underneath the 

threshold, weep

holes should not 

be blocked with 

sealant or debris.

Door

Figure 6-48: 

Threshold with stop and seal

Door

Adjustable 

Jamb

Weatherstrip

Figure 6-49: 

Adjustable jamb/head 

weatherstripping

For further general information on windows, see the National Institute of Building 

Sciences’ Building Envelope Design Guide 

(www.wbdg.org/design/envelope.php).
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

comply with wind load testing in accordance with ASTM E 1233. It is 

important to specify an adequate load path and to check its continuity 

during submittal review.

Where water infiltration protection is particularly demanding and important, it is recommended that on-site water infiltration testing in 

accordance with ASTM E 1105, be specified.

Water Infiltration 

Heavy rain accompanied by high winds can cause wind-driven water infiltration problems. The magnitude of the problem increases with the 

wind speed. Leakage can occur at the glazing/frame interface, the frame 

itself, or between the frame and wall. When the basic wind speed is greater than 165 mph, because of the very high design wind pressures and 

numerous opportunities for leakage path development, some leakage 

should be anticipated when the design wind speed 

conditions are approached.18

The successful integration of windows and curtain 

walls into exterior walls is a challenge in protecting 

against water infiltration. To the extent possible, 

when detailing the interface between the wall and 

the window or curtain wall units, designers should 

rely on sealants as the secondary line of defense against water infiltration, rather than making the sealant the primary protection. If a sealant 

18 The 165-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 120 mph. 

Figure 6-50: 

Two complete windows, 

including frames, blew 

out as a result of an 

inadequate number of 

fasteners. Typhoon Paka 

(Guam, 1997)

Where corrosion is problematic, anodized 

aluminum or galvanized window frames, 

and stainless steel frame anchors and hardware are recommended. 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

joint is the first line of defense, a second line of 

defense should be designed to intercept and drain 

water that drives past the sealant joint.

When designing joints between walls and windows 

and curtain wall units, consider the shape of the sealant joint (i.e., a square joint is typically preferred) 

and the type of sealant to be specified. The sealant 

joint should be designed to enable the sealant to 

bond on only two opposing surfaces (i.e., a backer rod or bond-breaker tape should be specified). 

Butyl is recommended as a sealant for concealed 

joints, and polyurethane for exposed joints. During 

installation, cleanliness of the sealant substrate is 

important (particularly if polyurethane or silicone 

sealants are specified), as is the tooling of the sealant. ASTM E 2112 provides guidance on the design 

of sealant joints, as well as other information pertaining to the installation of windows, including the 

use of sill pan flashings with end dams and rear legs 

(see Figure 6-51). Windows that do not have nailing 

flanges should typically be installed over a pan flashing. It is recommended that designers use ASTM E 

2112 as a design resource. 

Sealant joints can be protected with a removable 

stop, as illustrated in Figure 6-52. The stop protects 

the sealant from direct exposure to the weather 

and reduces the possibility of wind-driven rain penetration. 

The maximum test pressure used in the 

current ASTM test standard for evaluating 

resistance of window units to wind-driven 

rain is well below design wind pressures. 

Therefore, units that demonstrate adequate 

wind-driven rain resistance during testing 

may experience leakage during actual wind 

events.

Rear Leg

Front

End Dam

End Dam

Figure 6-51: 

View of a typical window sill pan flashing with 

end dams, rear leg, and turned-down front leg.

SOURCE: ASTM E 2112

Removable Stop

Air Space 

Behind Stop

Glazing

Wall

Window Frame

Sealant

Backer Rod

Figure 6-52: 

Protecting sealant 

retards weathering and 

reduces the exposure 

to wind-driven rain
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

6.3.3.3 Windows and Skylights in Hurricane-Prone Regions

Exterior glazing that is not impact-resistant (such as laminated glass 

or polycarbonate) or protected by shutters is extremely susceptible to 

breaking if struck by wind-borne debris. Even small, low-momentum missiles can easily break glazing that is not protected. At the building shown 

in Figure 6-53, approximately 400 windows were broken. Most of the 

breakage was caused by wind-blown aggregate from the building’s aggregate-ballasted single-ply membrane roofs, and aggregate from built-up 

roofs. With broken windows, a substantial amount of water can be blown 

into a building, and the internal air pressure can be greatly increased, 

which may damage the interior partitions and ceilings.19

In order to minimize interior damage, the IBC, through ASCE 7, 

prescribes that exterior glazing in wind-borne debris regions be impact-resistant, or be protected with an impact-resistant covering 

(shutters). ASCE 7 refers to ASTM E 1996 for missile loads and to ASTM E 1886 for the test method 

to be used to demonstrate compliance with the 

E 1996 load criteria. In addition to testing impact 

resistance, the window unit is subjected to pressure 

cycling after test missile impact to evaluate whether 

the window can still resist wind loads. If wind-borne 

debris glazing protection is provided by shutters, 

19 Glass spandrel panels are opaque glass. They are placed in curtain walls to conceal the area 

between the ceiling and the floor above.

Figure 6-53: 

Plywood panels (black 

continuous bands) 

installed after the 

glass spandrel panels 

were broken by roof 

aggregate.19 Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005)

Protection of glazing for safe rooms must 

meet debris impact criteria that is more 

restrictive (significant) than that presented 

in the building codes and the ICC 500. See 

Chapter 3 of FEMA 361 for the design 

criteria for debris impact resistance for safe 

rooms.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

the glazing is still required by ASCE 7 to meet the 

positive and negative design air pressures. 

For Category III and IV buildings in areas with a basic wind speed of 130 mph or greater, the glazing or 

shutter is required to resist a larger momentum test 

missile than would Category II, III, and IV buildings in areas with basic wind speeds less than 130 

mph. (Note: The 2009 edition of ASTM E 1996 references 130 mph based on ASCE 7-05. When using 

ASCE 7-10, a basic wind speed of 175 mph applies 

for Risk Category III and IV buildings).

Although the ASCE 7 wind-borne debris provisions 

only apply to glazing within a portion of hurricaneprone regions, it is recommended that all schools 

located where the basic wind speed is 135 mph or greater comply with 

the following recommendation:20

n To avoid interior wind and water damage, it is recommended that 

exterior glazing be designed to resist the test Missile D load (unless 

the E test missile is required as previously discussed) specified in 

ASTM E 1996 (see text box on the following page). 

20 The 135-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 100 mph. 

Window assemblies with laminated glass 

that have passed ASTM E 1886 can also 

be easily broken by low-momentum debris. 

However, unlike other types of glass, when 

laminated glass breaks, it is expected to 

remain in the frame and prevent entrance 

of wind and water. Cost will be incurred 

to replace the broken laminated glass, 

but that cost is significantly less than the 

cost of repairing interior wind and water 

damage, and the costs associated with 

loss of use of the school during repair work. 

Figure 6-54 shows laminated glass that 

was broken, but protected the building’s 

interior as intended.

Figure 6-54: 

The red arrow shows 

a piece of laminated 

glass that was broken, 

but remained in the 

frame to protect the 

building’s interior. 

The blue arrow shows 

unbroken laminated 

glass. The yellow 

arrows show granite 

wall panels. Estimated 

wind speed: 105 mph. 

Hurricane Katrina 

(Louisiana, 2005)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

n For those facilities where glazing resistant to bomb blasts is desired, 

the windows and glazed doors can be designed to accommodate wind 

pressure, missile loads, and blast pressure. However, the window and 

door units need to be tested for missile loads and cyclic air pressure, 

as well as for blast. A unit that meets blast criteria will not necessarily 

meet the ASTM E 1996 and ASTM E 1886 criteria, and vice versa. 

With the advent of building codes requiring glazing 

protection in wind-borne debris regions, a variety of 

shutter designs have entered the market. Shutters 

typically have a lower initial cost than laminated 

glass. However, unless the shutter is permanently 

anchored to the building (e.g., an accordion shutter), storage space will be needed. Also, when a 

hurricane is forecast, costs will be incurred each 

time shutters are installed and removed. The cost 

and difficulty of shutter deployment and demobilization on upper-level 

glazing may be avoided by using motorized shutters, although laminated 

glass may be a more economical solution. For further information on 

shutters, see Section 6.4.2.1. 

6.3.3.4 Non-Load-Bearing Walls, Wall Coverings, 

and Soffits

This section addresses exterior non-load-bearing 

walls, exterior wall coverings, and soffits, as well 

as the underside of elevated floors, and provides 

guidance for interior non-load-bearing masonry 

For further information on designing glazing to resist blast, see the “Blast Safety” 

resource pages of the National Institute 

of Building Sciences’ Building Envelope 

Design Guide (www.wbdg.org/design/

envelope.php).

For further general information on nonload-bearing walls and wall coverings, see 

the National Institute of Building Sciences’ 

Building Envelope Design Guide (www.

wbdg.org/design/envelope.php).

ASTM E 1996 specifies five missile categories, A through E. The missiles are of various weights 

and fired at various velocities during testing. Building type (critical or non-critical) and basic wind 

speed determine the missiles required for testing. Of the five missiles, the E missile has the greatest momentum. Missile E is required for critical facilities located where the basic wind speed is 

greater than or equal to 130 mph. Missile D is permitted where the basic wind speed is less than 

130 mph. FEMA 361 also specifies a missile for shelters. The shelter missile has much greater 

momentum than the D and E missiles, as shown below:

Missile Missile Weight Impact Speed Momentum

ASTM E 1996—D 9 pound 2x4 lumber 50 feet per second 

(34 mph) 14 lbf

 -s*

ASTM E 1996—E 9 pound 2x4 lumber 80 feet per second

(55 mph) 22 lbf

 -s*

FEMA 361 (Shelter Missile) 15 pound 2x4 lumber 147 feet per second 

(100 mph) 68 lbf

 -s*

*lbf -s = POUNDS FORCE PER SECOND
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

walls. See Section 6.4.3.5 for additional information pertaining to non-load-bearing walls, exterior 

wall coverings, and soffits for schools located in 

hurricane-prone regions. 

Loads and Resistance 

The IBC requires that soffits, exterior non-loadbearing walls, and wall coverings have sufficient 

strength to resist the positive and negative design 

wind pressures.

Soffits:  Depending on the wind direction, soffits 

can experience either positive or negative pressure. 

Besides the cost of repairing the damaged soffits, wind-borne soffit debris 

can cause property damage and injuries. Failed soffits may also provide a 

convenient path for wind-driven rain to enter the building, as illustrated 

by Figure 6-55. This school had a steep-slope roof with a ventilated attic 

space. The exterior CMU/brick veneer wall stopped just above the soffit (red arrows at Figure 6-55). Wind-driven rain entered the attic space 

where the soffit had blown away. This and other storm-damage research 

has shown that water blown into attic spaces after the loss of soffits can 

cause significant damage and the collapse of ceilings. Even in instances 

where soffits remain in place, water can penetrate through soffit vents 

and cause damage. 

Where corrosion is a problem, stainless 

steel fasteners are recommended for wall 

and soffit systems. For other components 

(e.g., furring, blocking, struts, and hangers), 

nonferrous components (such as wood), 

stainless steel, or steel with a minimum of 

G-90 hot-dipped galvanized coating are 

recommended. Additionally, access panels 

are recommended so components within 

soffit cavities can be periodically inspected 

for corrosion or dry rot. 

Figure 6-55: 

The exterior wall stopped just above the soffit (red arrows). After the metal soffit panels blew away, winddriven rain blew into the attic space, which saturated the fiberglass batt insulation and caused the ceiling 

boards to collapse. Estimated wind speed: 130 mph. Hurricane Katrina (Mississippi, 2005)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

The 2010 edition of ASCE 7 added loading criteria for soffits. Section 30.9.3 states that pressures 

on soffits (referred to as “overhangs”) are equal to 

the adjacent wall pressures. At this time, the only 

known test standard pertaining to soffit wind and 

wind-driven rain resistance is the Florida Building 

Code’s Testing Application Standard (TAS) No. 100(A)-

95. With this method, wind pressure testing is 

conducted to a maximum test speed of 140 mph, and wind-driven rain 

testing is conducted to a maximum test speed of 110 mph. The results 

of laboratory research have shown the need to develop an improved test 

method to evaluate the wind pressure and wind-driven rain resistance of 

soffits, but an improved test method has not yet been standardized. 

Exterior non-load-bearing masonry walls: Particular care should be given 

to the design and construction of exterior non-load-bearing masonry 

walls. Although these walls are not intended to carry gravity loads, they 

should be designed to resist the external and internal loading for components and cladding in order to avoid collapse. 

When these types of walls collapse, they represent 

a severe risk to life because of their great weight. 

Interior non-load-bearing masonry walls:  Special 

consideration should also be given to interior 

non-load-bearing masonry walls. Although these 

walls are not required by building codes to be designed to resist wind loads, if the exterior glazing 

is broken, or the exterior doors are blown away, 

the interior walls could be subjected to significant 

loads as the building rapidly becomes fully pressurized. To avoid casualties, it is recommended that 

interior non-load-bearing masonry walls adjacent 

to occupied areas be designed to accommodate 

loads exerted by a design wind event, using the 

partially enclosed pressure coefficient (see Figure 

6-56). By doing so, wall collapse may be prevented 

if the building envelope is breached. This recommendation is applicable to schools that will be 

used as hurricane evacuation shelters, to schools 

located in areas with a basic wind speed greater 

than 165 mph,21 and to schools in tornado-prone 

regions that do not have shelter space designed in 

accordance with FEMA 361.

21 The 165-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 120 mph.

Figure 6-56: 

The red arrows show the original location of a 

CMU wall that nearly collapsed following a rolling 

door failure. Estimated wind speed: 140–160 mph. 

Hurricane Charley (Florida, 2004)

For soffit design and application recommendations, see FEMA P-499, Fact Sheet 

7.5, Minimizing Water Intrusion Through 

Roof Vents in High-Wind Regions, (2010), 

available at http://www.fema.gov/library/

viewRecord.do?id=2138. 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Wall Coverings

There are a variety of exterior wall coverings. 

Brick veneer, exterior insulation finish systems 

(EIFS), stucco, metal wall panels, and aluminum 

and vinyl siding have often exhibited poor wind 

performance. Veneers (such as ceramic tile and 

stucco) over concrete, stone veneer, and cementfiber panels and siding have also blown off. Wood 

siding and panels rarely blow off. Although tiltup precast walls have failed during wind storms, 

precast wall panels attached to steel or concrete 

framed buildings typically offer excellent wind 

performance. The elevated school shown in 

Figure 6-57 had precast wall panels. The panels performed well, but 

portions of the roof covering blew off. Rooftop equipment also blew 

off. A gas line to one of the rooftop units was ruptured and displaced. 

Brick veneer: Brick veneer is frequently blown off walls during high 

winds. When brick veneer fails, wind-driven water can enter and damage buildings, and building occupants can be vulnerable to injury from 

wind-borne debris (particularly if the walls are sheathed with plastic 

foam insulation or wood fiberboard in lieu of wood panels). Pedestrians in the vicinity of damaged walls can also be vulnerable to injury 

from falling veneer. Common failure modes include tie (anchor) fastener pull-out, failure of masons to embed ties into the mortar (Figure 

6-58), poor bonding between ties and mortar, a mortar of poor quality, 

and tie corrosion.

Most schools do not have elevator 

penthouses. But for those that do, the penthouse walls must possess adequate wind 

and water resistance in order to ensure 

continuity of elevator service. If the walls 

blow away or water leaks through the wall 

system, the elevator controls and/or motors 

can be destroyed. Loss of elevators may 

affect facility operations. The restoration of 

elevator service can take weeks, even with 

expedited work.

Figure 6-57: 

Although uncommon for 

schools, precast wall 

panels were attached 

to the structural frame 

of this school. This 

type of wall typically 

offers excellent wind 

performance. Note the 

roof covering damage 

and displaced gas 

line. Estimated wind 

speed: Approximately 

125–130 mph. Hurricane 

Katrina (Louisiana, 2005)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-58: 

The four ties shown by 

the red arrows were 

not embedded into 

the mortar. Estimated 

wind speed: 105 mph. 

Hurricane Katrina, 

(Mississippi, 2005)

Ties are often installed before brick laying begins. When this is done, ties are often improperly 

placed above or below the mortar joints. When 

misaligned, the ties must be angled up or down to 

be embedded into the mortar joints. Misalignment 

not only reduces the embedment depth, but also 

reduces the effectiveness of the ties, because wind 

forces do not act parallel to the ties themselves. 

Corrugated ties typically used in residential veneer construction provide little resistance to compressive loads. The use of compression struts 

would likely be beneficial, but off-the-shelf devices do not currently exist. Two-piece adjustable ties provide significantly greater compressive 

strength than corrugated ties, and are therefore recommended. 

To avoid water leaking into the building, it is important that weep holes 

be adequately spaced and not be blocked during brick installation, and 

that through-wall flashings be properly designed and installed. When 

the base of the brick veneer occurs near grade, the grade should be designed so that it occurs several inches below the weeps so that drainage 

from the weeps is not impeded. Also, landscaping should be kept clear 

of weeps so that vegetation growth does not cause blockage of weeps. 

At the building shown in Figure 6-59, water leaked into the building 

along the base of many of the brick veneer walls. When high winds accompany heavy rain, a substantial amount of water can be blown into 

the wall cavity. 

For brick veneer design and application 

recommendations, see FEMA P-499, Fact 

Sheet 5.4, Attachment of Brick Veneer in 

High-Wind Regions, (2010), available at 

http://www.fema.gov/library/viewRecord.

do?id=2138. 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

EIFS: Figure 6-60 shows typical EIFS assemblies. Figure 6-61 shows EIFS blow-off. In this case, the molded 

expanded polystyrene (MEPS) was attached to gypsum board, which in turn was attached to metal studs. 

The gypsum board detached from the studs, which 

is a common EIFS failure mode. When the gypsum 

board on the exterior side of the studs is blown away, 

it is common for gypsum board on the interior side 

to also be blown off. The opening allows the building 

to become fully pressurized and allows the entrance 

of wind-driven rain. Other common types of failure 

include wall framing failure (see Figure 6-63), separation of the MEPS from its substrate, and separation of 

the synthetic stucco from the MEPS. 

When EIFS is applied over a concrete or CMU wall, 

the concrete/CMU substrate normally prevents wind 

and water from entering a building. But if the EIFS 

debonds from the concrete/CMU, EIFS debris can 

break unprotected glazing. 

Figure 6-59: 

Water leaked inside along the base of the brick 

veneer walls (red arrow). Estimated wind speed: 115 

mph. Hurricane Katrina (Louisiana, 2005)

Figure 6-60: Typical EIFS assemblies
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-61: 

EIFS blow-off near a 

wall corner. At one area, 

the metal fascia was 

also blown in.

SOURCE: FEMA 342, 

OKLAHOMA AND KANSAS 

MIDWEST TORNADOES OF MAY 

3, 1999 (1999B)

Reliable wind performance of EIFS is very demanding on the designer and installer. It is 

particularly important to attach the gypsum board 

with a sufficient number of properly located fasteners and to properly apply the adhesive. At 

the newly constructed building shown in Figure 

6-62, several of the gypsum boards blew off because of an inadequate number of screws. Also, 

at the gypsum board joint, there was insufficient 

fastener edge distance. Although not the primary failure mode, the adhesive between the MEPS 

and gypsum board was applied in rows, rather 

than continuously over the entire substrate with 

a notched trowel. 

Figure 6-62: 

At this EIFS failure, the screws attaching the gypsum 

board (yellow colored material) were too far apart (red 

circle). Additionally, at the board joint, the screws were too close to the board edge (blue circle). In this area, 

the screws were spaced at 41⁄2, 4, 6, 6, 9, and 91⁄2 inches on center. Also, the adhesive between the gypsum 

board and MEPS was applied in rows rather than continuously over the gypsum board. Estimated wind 

speed: 120 mph. Hurricane Katrina (Mississippi, 2005) 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Maintenance of EIFS and associated sealant joints in order to minimize 

the reduction of EIFS’ wind resistance due to water infiltration is also 

important. It is strongly recommended that EIFS be designed with a 

drainage system that allows for the dissipation of water leaks. For further 

information on EIFS performance during high winds and design guidance, see FEMA 489 and 549.

Another issue associated with EIFS is the potential for judgment errors. 

EIFS applied over studs is sometimes mistaken for a concrete wall, which 

people may seek shelter behind. However, instead of being protected by 

several inches of concrete, only two layers of gypsum board (i.e., one layer on each side of the studs) and a layer of MEPS separate the occupants 

from the impact of wind-borne debris that can easily penetrate such a 

wall and cause injury. 

Stucco over studs: Wind performance of traditional stucco walls is similar 

to the performance of EIFS, as shown in Figure 6-63. In several areas 

the metal stud system failed, in other areas the gypsum sheathing blew 

off the studs, and in other areas, the metal lath blew off the gypsum 

sheathing. The failure shown in Figure 6-63 illustrates the importance of 

designing and constructing wall framing (including attachment of stud 

tracks to the building and attachment of the studs to the tracks) to resist 

the design wind loads.

Figure 6-63: 

The stucco wall 

failure was caused by 

inadequate attachment 

between the stud tracks 

and the building’s 

structure. All of the 

metal stud framing 

within the red oval 

blew away. The arrow 

shows a bottom stud 

track that detached and 

pulled away from the 

building. Estimated wind 

speed: 110–125 mph. 

Hurricane Ivan (Florida, 

2004) 
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Metal wall panels: Wind performance of metal wall panels is highly variable. Performance depends on the strength of the specified panel (which 

is a function of material and thickness, panel profile, panel width, and 

whether the panel is a composite) and the adequacy of the attachment 

(which can be by either concealed clips or exposed fasteners). Excessive 

spacing between clips/fasteners is the most common problem. Clip/fastener spacing should be specified, along with the specific type and size of 

fastener. Figure 6-64 illustrates metal wall panel problems. At this school 

(which is also shown in Figure 6-12), the metal panels were attached 

with concealed fasteners. The panels unlatched at the standing seams. 

In addition to generating wind-borne debris, loss of panels allowed winddriven rain to enter the building. Water entry was facilitated by lack of 

a moisture barrier and solid sheathing behind the metal panels (as discussed below).

Metal wall panel performance also depends on adequacy of the framing to which it is attached. At the school shown in Figure 6-65, the metal 

fascia panels were attached to wood furring that was inadequately attached to CMU. Unlike the condition at the school shown at Figure 6-64, 

with the CMU behind the metal panels, water was prevented from entering the school. However, wind-borne fascia debris can cause damage or 

cause injury.

Figure 6-64: 

The loss of metal 

wall panels allowed 

a substantial amount 

of wind-driven rain 

to penetrate into the 

classroom. Estimated 

wind speed: 105–115 

mph. Hurricane Ivan 

(Florida, 2004)
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-71

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

To minimize water infiltration at metal wall panel joints, it is recommended that sealant tape be specified at sidelaps when the basic wind 

speed is in excess of 120 mph.22 However, endlaps should be left unsealed so that moisture behind the panels can be wicked away. Endlaps 

should be a minimum of 3 inches (4 inches where the basic wind speed 

is greater than 165 mph23 ) to avoid wind-driven rain infiltration. At the 

base of the wall, a 3-inch (4-inch) flashing should also be detailed, or the 

panels should be detailed to overlap with the slab or other components 

by a minimum of 3 inches (4 inches).

Siding: Vinyl siding blow-off is typically caused by nails spaced too far 

apart and/or the use of vinyl siding that has inadequate wind resistance. 

Vinyl siding is available with enhanced wind resistance features, such as 

an enhanced nailing hem, greater interlocking area, and greater thickness. In high wind regions, fiber cement siding blow-off is typically caused 

by the use of blind nails rather than face nails (see Figure 6-66). Where 

the design wind speed is low enough to use blind nailing, if blow-off occurs, it is typically caused by nails spaced too far apart and/or too close 

to the edge of the siding. Wood siding generally performs well in high 

wind events. 

22 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph. 

23 The 165-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 120 mph. 

Figure 6-65: 

Blow-off of metal 

fascia panels due to 

inadequate attachment 

of wood furring to the 

CMU wall. Estimated 

wind speed: 85–95 mph. 

Hurricane Ivan (Florida, 

2004)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-66: 

This cement fiber siding was attached with blind nails (red 

circle). Because of the high design wind speed, face nails should 

have been used (blue circle). Hurricane Francis (Florida, 2004)

Secondary line of protection: Almost all wall coverings permit the passage of some water past the exterior surface of 

the covering, particularly when the rain is wind-driven. 

For this reason, most wall coverings should be considered 

water-shedding, rather than waterproofing coverings. To 

avoid moisture-related problems, it is recommended that a 

secondary line of protection with a moisture barrier (such as housewrap 

or asphalt-saturated felt) and flashings around door and window openings be provided. Designers should specify that horizontal laps of the 

moisture barrier be installed so that water is allowed to drain from the 

wall (i.e., the top sheet should lap over the bottom sheet so that water 

running down the sheets remains on their outer surface). The bottom 

of the moisture barrier needs to be designed to allow drainage. Had the 

metal wall panels shown in Figure 6-64 been applied 

over a moisture barrier and sheathing, the amount 

of water entering the school would have likely been 

eliminated or greatly reduced, as is the case with 

the school shown in Figure 6-65.

For siding design and application recommendations, see FEMA P-499, Fact Sheet 

5.3, Siding Installation in High-Wind 

Regions, (2010), available at http://www.

fema.gov/library/viewRecord.do?id=2138. 
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-73

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

In areas that experience frequent wind-driven rain, incorporating a pressure-equalized rain screen design, by installing vertical furring strips 

between the moisture barrier and siding materials, will facilitate drainage of water from the space between the moisture barrier and backside 

of the siding. (For further information on rain screen wall systems, see 

the Siding Advisory.) In areas that frequently experience strong winds, 

enhanced flashing is recommended. Enhancements include use of flashings that have extra-long flanges, and the use of sealant and tapes. Flashing 

design should recognize that wind-driven water could be pushed up vertically. The height to which water can be pushed increases with wind 

speed. Water can also migrate vertically and horizontally by capillary 

action between layers of materials (e.g., between a flashing flange and 

housewrap). Use of a rain screen design, in conjunction with enhanced 

flashing design, is recommended in areas that frequently experience 

wind-driven rain or strong winds. It is recommended that designers attempt to determine what type of flashing details have successfully been 

used in the area where the facility will be constructed.

Underside of Elevated Floors

n If sheathing is applied to the underside of joists or trusses elevated 

on piles (e.g., to protect insulation installed between the joists/trusses), its attachment should be specified in order to avoid blow-off. 

Stainless steel or hot-dip galvanized nails or screws are recommended. Since ASCE 7 does not provide guidance for load determination, 

professional judgment in specifying attachment is needed. 

6.3.3.5 Non-Load-Bearing Walls, Wall Coverings, and Soffits in 

Hurricane-Prone Regions

To minimize long-term problems with exterior wall coverings and soffits, 

it is recommended that they be avoided to the maximum extent possible. 

Exposed or painted reinforced concrete or CMU offers greater reliability 

(i.e., they have no coverings that can blow off and become wind-borne 

debris). 

For interior non-load-bearing masonry walls in schools located where the 

basic wind speed is greater than 165 mph, see the recommendations given in Section 6.3.3.4.24

24 The 165-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 120 mph
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

6.3.3.6 Roof Systems

Because roof covering damage has historically been 

the most frequent and the costliest type of wind 

damage, special attention needs to be given to roof 

system design. See Section 6.3.3.7 for additional 

information pertaining to schools located in hurricane-prone regions.

Code Requirements 

The IBC requires the load resistance of the roof assembly to be evaluated by one of the test methods listed in IBC’s Chapter 15. Design 

professionals are cautioned that designs that deviate from the tested 

assembly (either with material substitutions or change in thickness or 

arrangement) may adversely affect the wind performance of the assembly. The IBC does not specify a minimum safety factor. However, for the 

roof system, a safety factor of 2 is recommended. To apply the safety 

factor, divide the test load by 2 to determine the allowable design load. 

Conversely, multiply the design load by 2 to determine the minimum required test resistance.

For structural metal panel systems, the IBC requires test methods UL 580 or ASTM E 1592. It 

is recommended that design professionals specify 

use of E 1592, because it gives a better representation of the system’s uplift performance capability. 

At the building shown in Figure 6-67, three of the 

standing seams opened up (unlatched). In the 

opened condition, the panels were very susceptible to progressive failure, and they were no longer 

in a watertight condition. At other roof areas, several panels were blown off. ASTM E 1592 is more 

suitable than UL 580 for assessing the potential for 

panels to unlatch. Note the air terminal (“lightning 

rod”) shown by the red arrow. The lightning protection system (LPS) conductor ran underneath 

the ridge flashing. By being concealed underneath 

the ridge flashing, the conductor was shielded from 

the wind, (as recommended in Section 6.3.4.4) and 

was therefore not susceptible to blow-off. 

For further general information on roof systems, see the National Institute of Building 

Sciences’ Building Envelope Design Guide

(www.wbdg.org/design/envelope.php).

The roof of the elevator penthouse must 

possess adequate wind and water resistance to ensure continuity of elevator 

service. It is recommended that a secondary roof membrane, as discussed 

in Section 6.3.3.7, be specified over the 

elevator penthouse roof deck. 

The Design Load when using allowable 

stress design: 

When using ASCE 7-05 and earlier editions, 

the design load is the load derived from the 

calculation procedure given in Chapter 6. 

When using ASCE 7-10, the design load 

is the load derived from the calculation 

procedure given in Chapter 30, which is 

then multiplied by 0.6 (the load combination 

factor given in Section 2.4.1).
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Load Resistance

Load resistance is commonly specified by a Factory 

Mutual Research (FMR) rating, such as FM 1-75. 

The first number (1) indicates that the roof assembly passed the FMR tests for a Class 1 fire rating. The 

second number (75) indicates the uplift resistance 

in pounds per square foot (psf) that the assembly 

achieved during testing. With a safety factor of two 

this assembly would be suitable for a maximum design uplift load of 37.5 psf. 

The highest uplift load occurs at the roof corners 

because of building aerodynamics as discussed in 

Section 6.1.3. The perimeter has a somewhat lower 

load, while the field of the roof has the lowest load. 

FMG Property Loss Prevention Data Sheets (dates 

vary) are formatted so that a roof assembly can be 

selected for the field of the roof. For the perimeter 

and corner areas, FMG Data Sheet 1-29 provides 

three options: 1) use the FMG Approval Guide listing if it includes a perimeter and corner fastening 

method; 2) use a roof system with the appropriate 

FMG Approval rating in the field, perimeter, and 

corner, in accordance with Table 1 in FMG Data 

Sheet 1-29; or 3) use prescriptive recommendations given in FMG Data Sheet 1-29. 

Figure 6-67: 

Three of the panel ribs 

opened up (one to the 

right of the blue arrow 

and two to the left). The 

LPS conductor serving 

the air terminal (red 

arrow) ran underneath 

the ridge flashing. 

Estimated wind 

speed: 105–115 mph. 

Hurricane Ivan (Florida, 

2004)

FM Global (FMG) is the name of the 

Factory Mutual Insurance Company and its 

affiliates. One of FMG’s affiliates, Factory 

Mutual Research (FMR) provides testing 

services, produces documents that can be 

used by designers and contractors, and 

develops test standards for construction 

products and systems. FMR evaluates roofing materials and systems for resistance to 

fire, wind, hail, water, foot traffic, and corrosion. Roof assemblies and components are 

evaluated to establish acceptable levels of 

performance. Some documents and activities are under the auspices of FMG and 

others are under FMR.

Although other test labs can test systems 

using FMG test methods, in order to 

achieve FMG approval, system testing must 

be conducted by FMG. Roof assemblies 

that meet FMG requirements can be found 

at https://roofnav.fmglobal.com/RoofNav/

Login.aspx. 

FMG’s Loss Prevention Data Sheets can be 

downloaded from the above Web site. The 

Data Sheets are not updated on a regular 

basis. Refer to the Web site to ensure that 

the current edition is being used.
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When perimeter and corner uplift resistance values are based on a prescriptive method rather than testing, the field assembly is adjusted to 

meet the higher loads in the perimeter and corners by increasing the 

number of fasteners or decreasing the spacing of adhesive ribbons by 

a required amount. However, this assumes that the failure is the result 

of the fastener pulling out from the deck, or that the failure is in the 

vicinity of the fastener plate, which may not be the case. Also, the increased number of fasteners required by FMG may not be sufficient to 

comply with the perimeter and corner loads derived from the building 

code. Therefore, if FMG resistance data are specified, it is prudent for 

the design professional to specify the resistance for each zone of the 

roof separately. Using the example cited above, if the field of the roof 

is specified as 1-75, the perimeter would be specified as 1-130 and the 

corner would be specified as 1-190. 

If the roof system is fully adhered, it is not possible to increase the uplift 

resistance in the perimeter and corners. Therefore, for fully adhered 

systems, the uplift resistance requirement should be based on the corner load rather than the field load.

Roof System Performance 

Storm-damage research has shown that sprayed polyurethane foam 

(SPF) and liquid-applied roof systems are very reliable high-wind performers. If the substrate to which the SPF or liquid-applied membrane 

is applied does not lift, it is highly unlikely that these systems will blow 

off. Both systems are also more resistant to leakage after missile impact 

damage than most other systems. Built-up roofs (BURs) and modified bitumen systems have also demonstrated good wind performance 

provided the edge flashing/coping does not fail (which happens frequently). The exception is aggregate surfacing, which is prone to 

blow-off (see Figures 6-14, 6-23, and 6-53). Modified bitumen applied 

to a concrete deck has demonstrated excellent resistance to progressive 

peeling after blow-off of the metal edge flashing. Metal panel performance is highly variable. Some systems are very wind resistant, while 

others are quite vulnerable. 

Of the single-ply attachment methods, the paver-ballasted and fully 

adhered methods are the least problematic. Systems with aggregate ballast are prone to blow-off, unless care is taken in specifying the size of 

aggregate and the parapet height (see Figures 6-8 and 6-53). The performance of protected membrane roofs (PMRs) with a factory-applied 

cementitious coating over insulation boards is highly variable. When 

these boards are installed over a loose-laid membrane, it is critical that 

an air retarder be incorporated to prevent the membrane from ballooning and disengaging the boards. ANSI/SPRI RP-4 (which is referenced 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

in the IBC) provides wind guidance for ballasted 

systems using aggregate, pavers, and cementitiouscoated boards. 

When fully adhering boards to concrete decks, it is 

recommended that a planar flatness of a maximum 

of 1⁄4-inch variation over a 10-foot length (when 

measured by a straightedge) be specified. Prior 

to installation of the roof insulation, it is recommended that the planar flatness be checked with 

a straightedge. If the deck is outside of the 1⁄4-inch 

variation, it is recommended that the high spots be 

ground or the low spots be suitably filled.

The Wind Design Guide for Mechanically Attached 

Flexible Membrane Roofs, B1049 (National Research 

Council of Canada, 2005) provides recommendations related to mechanically attached single-ply 

and modified bituminous systems. B1049 is a comprehensive wind design guide that includes discussion on air retarders. 

Air retarders can be effective in reducing membrane flutter, in addition 

to being beneficial for use in ballasted single-ply systems. When a mechanically attached system is specified, careful coordination with the 

structural engineer in selecting deck type and thickness is important. 

When fully adhering insulation boards, it 

is recommended that the boards be no 

larger than 4 feet by 4 feet. It is also recommended that the board thickness not 

exceed 2 inches (11⁄2 inches is preferable). 

Use of small thin boards makes it easier for 

the contractor to conform the boards to the 

substrate. At the building shown in Figure 

6-68, 4-foot by 8-foot insulation boards 

were set in hot asphalt over a concrete 

deck. A few of the boards detached from 

the deck. The boards may have initiated 

the membrane blow-off, or the membrane 

blow-off may have been initiated by lifting 

and peeling of the metal edge flashing, in 

which case, loss of the insulation boards 

was a secondary failure. 

Figure 6-68: 

The blown off insulation 

(red arrow) may have 

initiated blow-off of 

the roof membrane. 

Estimated wind 

speed: 105–115 mph. 

Hurricane Ivan (Florida, 

2004)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

When specifying a mechanically attached single-ply 

membrane, if a steel deck is selected, it is critical 

to specify that the membrane fasteners be attached 

in rows perpendicular to the steel flanges to avoid 

overstressing the attachment of the deck to the 

deck support structure. At the school shown in 

Figure 6-69, the fastener rows of the mechanically 

attached single-ply membrane ran parallel to the 

top flange of the steel deck. The deck fasteners were overstressed and 

a portion of the deck blew off and the membrane progressively tore. 

When membrane fasteners run parallel to the flange, the flange with 

membrane fasteners essentially carries the entire uplift load because of 

the deck’s inability to transfer any significant load to adjacent flanges. 

Hence, at the joists shown in Figure 6-68, the deck fasteners on either 

side of the flange with the membrane fasteners are the only connections 

to the joist that are carrying substantial uplift load.

Edge Flashings and Copings

Roof membrane blow-off is almost always a result of lifting and peeling 

of the metal edge flashing or coping, which serves to clamp down the 

membrane at the roof edge. Therefore, it is important for the design professional to carefully consider the design of metal edge flashings, copings, 

and the nailers to which they are attached. The metal edge flashing on 

the modified bitumen membrane roof shown in Figure 6-70 was installed 

For metal panel and metal shingle roof 

system design and application recommendations, FEMA P-499, Fact Sheet 7.6,

Metal Roof Systems in High-Wind Regions,

(2010), is available at http://www.fema.gov/

library/viewRecord.do?id=2138.

Figure 6-69: 

The orientation of the 

membrane fastener 

rows led to blow-off 

of the steel deck. 

Hurricane Marilyn 

(U.S. Virgin Islands, 

1995)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

underneath the membrane, rather than on top of it, and then stripped 

in. In this location, the edge flashing was unable to clamp the membrane 

down. At one area, the membrane was not sealed to the flashing. An ink 

pen was inserted into the opening prior to photographing to demonstrate 

how wind could catch the opening and lift and peel the membrane. 

ANSI/SPRI ES-1 provides general design guidance including a methodology for determining the outward-acting load on the vertical flange of 

the flashing/coping (ASCE 7 does not provide this guidance). ANSI/

SPRI ES-1 is referenced in the IBC. ANSI/SPRI ES-1 also includes test 

methods for assessing flashing/coping resistance. This manual recommends a minimum safety factor of 3 for edge flashings, copings, and 

nailers for schools. For FMG-insured facilities, FMR-approved flashing 

should be used and FM Data Sheet 1-49 should also be consulted.

The traditional edge flashing/coping attachment method relies on 

concealed cleats that can deform under wind load and lead to disengagement of the flashing/coping (see Figure 6-71) and subsequent lifting 

and peeling of the roof membrane. When a vertical flange disengages 

and lifts up, the edge flashing and membrane are very susceptible to failure. Normally, when a flange lifts, the failure continues to propagate and 

the metal edge flashing and roof membrane blows off. 

Figure 6-70: 

The ink pen shows an 

opening that the wind 

can catch to cause 

lifting and peeling of the 

membrane.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

At the building shown in Figure 6-72, the cleat nailing provided very little 

resistance to outward deflection of the cleat and coping. While most of 

the continuous inner and outer cleats remained on the building, several 

sections of coping and at least one cleat blew off once the amount of deflection was sufficient for the coping to disengage from the cleat. In this 

case, the roof membrane did not lift and peel as often happens when the 

coping blows off. However, the coping debris did gouge the roof membrane. Note that the base flashing was stopped at the top of the parapet. 

It should have been run across the top of the nailer and turned down 

and nailed so as to provide greater watertight protection in the event of 

coping leakage or coping blow-off.

Figure 6-71: 

The metal edge 

flashing on this building 

disengaged from the 

continuous cleat and 

the vertical flange lifted. 

Hurricane Hugo (South 

Carolina, 1989)

Figure 6-72: 

The coping blew off 

because of inadequate 

attachment of the 

cleats. Estimated 

wind speed: 92 mph. 

Hurricane Ike (Texas, 

2008)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Storm-damage research has revealed that, in lieu of cleat attachment, 

the use of exposed fasteners to attach the vertical flanges of copings and 

edge flashings is a very effective and reliable attachment method. The 

coping shown in Figure 6-73 was attached with 1⁄4-inch diameter stainless 

steel concrete spikes at 12 inches on center. When the fastener is placed 

in wood, #12 stainless steel screws with stainless steel washers are recommended. The fasteners should be more closely spaced in the corner 

areas (the spacing will depend upon the design wind loads). ANSI/SPRI 

ES-1 provides guidance on fastener spacing and thickness of the coping 

and edge flashing.

Gutters and Downspouts

Storm-damage research has shown that gutters are seldom designed and 

constructed to resist wind loads. At the school shown in Figure 6-74, the 

gutter brackets were attached with a fastener near the top and bottom 

of the bracket. Hence, the fasteners prevented the brackets from rotating out from the wall. However, because the gutter was not attached to 

the brackets, the gutter blew away. When a gutter lifts, it typically causes 

the edge flashing that laps into the gutter to lift as well. Frequently, this 

results in a progressive lifting and peeling of the roof membrane. The 

membrane blow-off shown in Figure 6-75 was initiated by gutter uplift. 

The gutter was similar to that shown in Figure 6-74. The membrane blowoff caused significant interior water damage.

Figure 6-73: 

Both vertical faces 

of the coping were 

attached with exposed 

fasteners instead of 

concealed cleats. 

Typhoon Paka (Guam, 

1997)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Special design attention needs to be given to attaching gutters to prevent 

uplift, particularly for those in excess of 6 inches in width. Currently, 

there are no design guides or standards pertaining to gutter wind resistance. It is recommended that the designer calculate the uplift load on 

gutters using the overhang coefficient from ASCE 7. There are two approaches to resist gutter uplift.

n Gravity-support brackets can be designed to resist uplift loads. In these

cases, in addition to being attached at its top, the bracket should also 

be attached at its low end to the wall (as was the case for the brackets 

shown in Figure 6-74). The gutter also needs to be designed so it is attached securely to the bracket in a way that will effectively transfer the 

gutter uplift load to the bracket (see Figure 6-76). Bracket spacing 

Figure 6-74: Because 

this gutter was not 

attached to the bracket, 

wind lifted the gutter 

along with the metal 

edge flashing that 

lapped into the gutter. 

Bracket fasteners are 

indicated by the red 

arrows. Hurricane 

Francis (Florida, 2004)

Figure 6-75: The original 

modified bitumen 

membrane was blown 

away after the gutter 

lifted in the area shown 

by the red arrow (the 

black membrane is 

a temporary roof). 

Hurricane Francis 

(Florida, 2004)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

will depend on the gravity and uplift load, the bracket’s strength, 

and the strength of connections between the gutter/bracket and the 

bracket/wall. With this option, the bracket’s top will typically be attached to a wood nailer, and that fastener will be designed to carry 

the gravity load. The bracket’s lower connection will resist the rotational force induced by gutter uplift. Because brackets are usually 

spaced close together to carry the gravity load, developing adequate 

connection strength at the lower fastener is generally not difficult. 

Screws rather than nails are recommended to attach brackets to the 

building because screws are more resistant than nails to dynamically 

induced pull-out forces.

Figure 6-76: 

At this gutter, a fastener 

connected the bracket 

to the gutter. Note: To 

avoid leakage at the 

fasteners between the 

bracket and gutter, the 

bracket should extend 

near or to the top of 

the gutter so that the 

fastener would be above 

the waterline. Estimated 

wind speed: 95 mph. 

Hurricane Ike (Texas, 

2008)

n The other option is to use gravity-support brackets only to resist gravity loads, and use separate sheet-metal straps at 45-degree angles to 

the wall to resist uplift loads (Figure 6-77). Strap spacing will depend 

on the gutter uplift load and strength of the connections between 

the gutter/strap and the strap/wall. Note that FMG Data Sheet 1-49 

recommends placing straps 10 feet apart. However, at that spacing 

with wide gutters, fastener loads induced by uplift are quite high. 

When straps are spaced at 10 feet, it can be difficult to achieve sufficiently strong uplift connections.

When designing a bracket’s lower connection to a wall or a strap’s 

connection to a wall, designers should determine appropriate screw 

pull-out values. With this option, a minimum of two screws at each 

end of a strap is recommended. At a wall, screws should be placed 

side by side, rather than vertically aligned, so the strap load is carried 

equally by the two fasteners. When fasteners are vertically aligned, 

most of the load is carried by the top fastener.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Since the uplift load in the corners is much higher than the load between 

the corners, enhanced attachment is needed in corner areas regardless 

of the option chosen. ASCE 7 provides guidance about determining a 

corner area’s length.

Storm damage research has also shown that downspouts are seldom designed and constructed to resist wind loads (see Figure 6-78). Special 

design attention needs to be given to attaching downspouts to prevent 

blow-off. Currently there are no design guides or standards pertaining 

to downspout wind resistance. The keys to achieving successful performance include providing brackets that are not excessively spaced, 

bracket strength, and the strength of the connections between the brackets and wall. 

Parapet Base Flashings 

Information on loads for parapet base flashings was first introduced 

in the 2002 edition of ASCE 7. The loads on base flashings are greater 

than the loads on the roof covering if the parapet’s exterior side is airpermeable. When base flashing is fully adhered, it has sufficient wind 

resistance in most cases. However, when base flashing is mechanically 

fastened, typical fastening patterns may be inadequate, depending on 

design wind conditions (see Figure 6-79). Therefore, it is imperative that 

the base flashing loads be calculated, and attachments be designed to accommodate these loads. It is also important for designers to specify the 

attachment spacing in parapet corner regions to differentiate them from 

the regions between corners.

Figure 6-77: 

Sheet metal straps 

were attached to an 

existing gutter that 

lacked sufficient uplift 

resistance. 
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-85

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Figure 6-78: 

Blow-off of this 

downspout resulted 

in glazing breakage. 

Estimated wind 

speed: 105–115 mph. 

Hurricane Ivan (Florida, 

2004)

Figure 6-79: 

If mechanically attached 

base flashings have 

an insufficient number 

of fasteners, the base 

flashing can be blown 

away. Hurricane Andrew 

(Florida, 2004)

When the roof membrane is specified to be adhered, it is recommended that fully adhered base flashings be specified in lieu of mechanically 

attached base flashings. Otherwise, if the base flashing is mechanically 

attached, ballooning of the base flashing during high winds can lead to 

lifting and progressive peeling of the roof membrane.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Steep-Slope Roof Coverings 

For a discussion of wind performance of asphalt shingle (see Figure 6-12) 

and tile roof coverings (see Figure 6-83), see FEMA 488, FEMA 489, FEMA 

549, and FEMA P-757. For recommendations pertaining to asphalt shingles and tiles, see Fact Sheets 

7.1, 7.2, and 7.3 in FEMA P-499. 

6.3.3.7 Roof Systems in Hurricane-Prone Regions

The following types of roof systems are recommended for schools in hurricane-prone regions, 

because they are more likely to avoid water infiltration if the roof is hit by wind-borne debris, and also because these 

systems are less likely to become sources of wind-borne debris:

n In tropical climates where insulation is not needed above the roof 

deck, specify either liquid-applied membrane over cast-in-place 

concrete deck, or modified bitumen membrane torched directly to 

primed cast-in-place concrete deck.

n Install a secondary membrane over a concrete deck (if another type 

of deck is specified, a cover board may be needed over the deck). 

Seal the secondary membrane at perimeters and penetrations. 

Specify rigid insulation over the secondary membrane. Where the 

basic wind speed is up to 150 mph,25 a minimum 2-inch thick layer 

of insulation is recommended. Where the speed is between 150 and 

175 mph,26 a total minimum thickness of 3 inches is recommended 

(installed in two layers). Where the speed is greater than 175 mph, 

a total minimum thickness of 4 inches is recommended (installed 

in two layers). A layer of 5

/8-inch thick glass mat gypsum roof board 

is recommended over the insulation, followed by a modified bitumen membrane. A modified bitumen membrane is recommended 

for the primary membrane because of its somewhat enhanced resistance to puncture by small missiles compared with other types of 

roof membranes.

25 The 150-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 110 mph. 

26 The 150- to 175-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV 

buildings. If ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 

between 110 and 130 mph. 

For design and application recommendations pertaining to roof vents, see FEMA 

P-499, Fact Sheet 7.5, Minimizing Water 

Intrusion Through Roof Vents in High-Wind 

Regions, (2010), available at http://www.

fema.gov/library/viewRecord.do?id=2138. 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

The purpose of the insulation and gypsum roof board is to absorb 

missile energy. If the primary membrane is punctured or blown off 

during a storm, the secondary membrane should provide watertight 

protection unless the roof is hit with missiles of very high momentum 

that penetrate the insulation and secondary membrane. Figure 6-80 

illustrates the merit of specifying a secondary membrane. Although 

the copper roof blew off, fortunately there was a very robust underlayment (a built-up membrane) that remained in place. The minor 

leakage that occurred did not impair building operations. 

For an SPF roof system over a concrete deck (if another type of deck is 

specified, a cover board may be needed over the deck), where the basic 

wind speed is less than 175 mph,27 it is recommended that the foam be 

a minimum of 3 inches thick to avoid missile penetration through the 

entire layer of foam. Where the speed is greater than 175 mph, a 4-inch 

minimum thickness is recommended. It is also recommended that the 

SPF be coated, rather than protected with an aggregate surfacing.

With respect to wind-borne debris, SPF behaves quite differently than 

other types of roof coverings. Except for paver-ballasted systems, other 

types of coverings (including tough membranes such as modified bitumen and metal panels) can be easily penetrated by debris. When these 

other types of coverings are punctured, water enters the roof system and 

typically leaks into the building unless there is a secondary membrane. 

27 The 175-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 130 mph. 

Figure 6-80: 

The secondary 

membrane prevented 

significant leakage 

into the building after 

the copper roof blew 

off. Hurricane Andrew 

(Florida, 1992)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

With SPF, missiles can gouge the foam (as shown in Figure 6-81), but it is 

rare for missiles to completely penetrate through the foam. When a quality SPF is gouged, only an insignificant amount of moisture is absorbed 

into the foam cells at the gouged area, even if the gouge is not repaired 

for several months. 

n For a PMR, it is recommended that pavers weighing a minimum of 22 

psf be specified. In addition, base flashings should be protected with 

metal (such as shown in Figure 6-88) to provide debris protection. 

Parapets with a 3-foot minimum height (or higher if so indicated 

by ANSI/SPRI RP-4) are recommended at roof edges. This manual 

recommends that PMRs not be used for schools in hurricane-prone 

regions where the basic wind speed exceeds 175 mph.28

n For structural metal roofs, it is recommended that a roof deck be 

specified, rather than attaching the panels directly to purlins as 

is commonly done with pre-engineered metal buildings. If panels 

blow off buildings without roof decking, wind-borne debris and 

rain are free to enter the building. 

Structural standing seam metal roof panels with concealed clips 

and mechanically seamed ribs spaced at 12 inches on center are 

recommended. If the panels are installed over a concrete deck, 

a modified bitumen secondary membrane is recommended if the 

deck has a slope less than 1⁄2:12. If the panels are installed over 

28 The 175-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 130 mph. 

Figure 6-81: 

Although a missile cut 

into the SPF, the roof 

was still watertight. 

The ink pen (blue 

arrow) shows the 

relative size of the 

impact area. Estimated 

wind speed: 110 mph. 

Hurricane Ike (Texas, 

2008)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

a steel deck or wood sheathing, a modified bitumen secondary 

membrane (over a suitable cover board when over steel decking) is recommend, followed by rigid insulation and metal panels. 

Where the basic wind speed is up to 150 mph,29 a minimum 2-inch 

thick layer of insulation is recommended. Where the speed is between 150 and 175 mph,30 a total minimum thickness of 3 inches is 

recommended. Where the speed is greater than 175 mph, a total 

minimum thickness of 4 inches is recommended. Although some 

clips are designed to bear on insulation, it is recommended that 

the panels be attached to wood nailers attached to the deck, because nailers provide a more stable foundation for the clips. 

If the metal panels are blown off or punctured during a hurricane, the 

secondary membrane should provide watertight protection unless the 

roof is hit with missiles of very high momentum. At the roof shown in 

Figure 6-82, the structural standing seam panel clips bore on rigid insulation over a steel deck. Had a secondary membrane been installed 

over the steel deck, the membrane would have likely prevented significant interior water damage and facility disruption.

29 The 150-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 110 mph.

30 The 150- to 175-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV 

buildings. If ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 

between 110 and 130 mph. 

Figure 6-82: Significant 

interior water damage 

and facility interruption 

occurred after the 

standing seam roof blew 

off. Hurricane Marilyn 

(U.S. Virgin Islands, 

1995)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Based on field performance of architectural metal panels in hurricaneprone regions, exposed fastener panels are recommended in lieu of 

architectural panels with concealed clips. For panel fasteners, stainless 

steel screws are recommended. A secondary membrane protected with 

insulation is recommended, as discussed above for structural standing 

seam systems. 

In order to avoid the possibility of roofing components blowing off and 

causing damage to other portions of the school or striking people arriving at a school shelter during a storm, the following roof systems are 

not recommended: aggregate surfacings, either on BUR, single-plies, or 

SPF; lightweight concrete pavers; cementitious-coated insulation boards; 

slate; and tile (see Figures 6-83 and 6-84). Even when slates and tiles are 

properly attached to resist wind loads, their brittleness makes them vulnerable to breakage as a result of wind-borne debris impact. The tile and 

slate fragments can be blown off the roof, and fragments can damage 

other parts of the roof causing a cascading failure. 

The tiles shown in Figure 6-83 were attached with the foam-adhesive (adhesive-set) method. The tiles shown in Figure 6-84 were attached with 

the wire-tied method (an uncommon method in the eastern portion of 

the United States). In addition to the wire attachments, the tiles were 

also attached with stainless steel clips at the first three rows from the 

eave. All of the tiles had tail hooks, and adhesive was used between the 

tail and head of all tiles. Except for the three perimeter rows which were 

clipped, the wires did not prevent the tiles from lifting a short distance 

above the concrete deck. The failure was attributed to tiles lifting and 

then slamming back down on the deck, where upon they broke and the 

tile fragments blew away. 

Figure 6-83: 

Brittle roof coverings, 

like slate and tile, can 

be broken by missiles, 

and tile debris can break 

other tiles. Estimated 

wind speed: 140–160 

mph. Hurricane Charley 

(Florida, 2004)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Mechanically attached and air-pressure equalized single-ply membrane 

systems are susceptible to massive progressive failure after missile impact, 

and are therefore not recommended for schools in hurricane-prone 

regions. At the school shown in Figure 6-85, a missile struck the fully 

adhered low-sloped roof and slid into the steep-sloped reinforced mechanically attached single-ply membrane in the vicinity of the red arrow. 

A large area of the mechanically attached membrane was blown away 

as a result of progressive membrane tearing. Fully adhered single-ply 

membranes are very vulnerable to missile puncture and are not recommended unless they are ballasted with pavers. 

Figure 6-84 

These wire-tied tiles 

were installed over 

a concrete deck. The 

failure was attributed 

to lack of vertical 

restraint, which allowed 

the tiles to lift and then 

be broken when they 

slammed back down 

onto the deck. Typhoon 

Paka (Guam, 1997)

Figure 6-85: This 

mechanically attached 

single-ply membrane 

progressively tore after 

being cut by windborne debris. Hurricane 

Andrew (Florida, 1992)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Edge flashings and copings: If cleats are used for attachment, it is recommended that a “peel-stop” bar be placed over the roof membrane 

near the edge flashing/coping, as illustrated in Figure 6-86. The purpose 

of the bar is to provide secondary protection against membrane lifting 

and peeling in the event that edge flashing/coping fails. A robust bar 

specifically made for bar-over mechanically attached single-ply systems is 

recommended. The bar needs to be very well anchored to the parapet 

or the deck. Depending on design wind loads, spacing between 4 and 12 

inches on center is recommended. A gap of a few inches should be left 

between each bar to allow for water flow across the membrane. After the 

bar is attached, it is stripped over with a stripping ply.

Walkway pads: Roof walkway pads are frequently blown off during hurricanes (Figure 6-87). Pad blow-off does not usually damage the roof 

membrane. However, wind-borne pad debris can damage other building components and injure people. Currently there is no test standard 

to evaluate uplift resistance of walkway pads. Walkway pads are therefore 

not recommended in hurricane-prone regions.

Parapets: For low-sloped roofs, minimum 3-foot high parapets are recommended. With parapets of this height or greater, the uplift load in 

the corner region is substantially reduced (ASCE 7 permits treating the 

corner zone as a perimeter zone). Also, a high parapet (as shown in 

Figure 6-106) may intercept wind-borne debris and keep it from blowing off the roof and damaging other building components or injuring 

people. To protect base flashings from wind-borne debris damage and 

subsequent water leakage, it is recommended that metal panels on furring strips be installed over the base flashing (Figure 6-88). Exposed 

stainless steel screws are recommended for attaching the panels to the 

furring strips, because using exposed fasteners is more reliable than 

using concealed fasteners or clips (as were used for the failed panels 

shown in Figure 6-64). 

Continuous peel-stop

bar over membrane

Membrane

Membrane

Continuous peel-stop bar over membrane

Metal Edge Flashing Detail Coping Detail

Additional peel-stop bar 

over membrane if parapet 

heights exceeds 12 inches

Roof

parapet

Figure 6-86: 

A continuous peelstop bar over the 

membrane may 

prevent a catastrophic 

progressive failure if the 

edge flashing or coping 

is blown off. (Modified 

from FEMA 55, 2000)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Figure 6-87: 

Several rubber walkway pads were blown 

off the single-ply membrane roof. Estimated 

wind speed: 130 mph. Hurricane Katrina 

(Mississippi, 2005)

Figure 6-88: 

Base flashing protected 

by metal wall panels 

attached with exposed 

screws. Estimated 

wind speed: 120 mph. 

Hurricane Katrina 

(Mississippi, 2005)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

6.3.4 Nonstructural Systems and Equipment

Nonstructural systems and equipment include all components that are 

not part of the structural system or building envelope. Exterior-mounted 

mechanical equipment (e.g., exhaust fans, HVAC units, relief air hoods, 

rooftop ductwork, and boiler stacks), electrical equipment (e.g., light 

fixtures and LPSs), and communications equipment (e.g., antennae and 

satellite dishes) are often damaged during high winds. Damaged equipment can impair the operation of the facility, the equipment can detach 

and become wind-borne missiles, and water can enter the facility where 

equipment was displaced (see Figure 6-89). The most common problems typically relate to inadequate equipment anchorage, inadequate 

strength of the equipment itself, and corrosion.

Exterior-mounted equipment is especially vulnerable to hurricane-induced damage, and special attention should be paid to positioning and 

mounting of these components in hurricane-prone regions. See Sections, 

6.3.4.2 and 6.3.4.4 for additional information pertaining to schools located in hurricane-prone regions.

6.3.4.1 Exterior-Mounted Mechanical Equipment

This section discusses loads and attachment methods, as well as the problems of corrosion and water infiltration.

Loads and Attachment Methods

Information on loads on rooftop equipment was first introduced in 

the 2002 edition of ASCE 7. For guidance on load calculations, see 

Calculating Wind Loads and Anchorage Requirements for Rooftop Equipment 

Figure 6-89: 

This gooseneck was 

attached with only 

two small screws. 

Emergency repairs had 

not been made at the 

time this photograph 

was taken, which was 5 

days after the hurricane 

struck. A substantial 

amount of water was 

able to enter the school. 

Hurricane Francis 

(Florida, 2004) 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

(ASHRAE, 2006). A minimum safety factor of 3 is 

recommended for schools. Loads and resistance 

should also be calculated for heavy pieces of equipment since the dead load of the equipment is often 

inadequate to resist the design wind load. The 30-

foot by 10-foot by 8-foot 18,000-pound HVAC unit 

shown in Figure 6-90 was attached to its curb with 

16 straps (one screw per strap). Although the wind 

speeds were estimated to be only 85 to 95 miles per 

hour (peak gust), the HVAC unit blew off the building. The inset at Figure 6-90 shows the curb upon 

which the unit was attached. A substantial amount of water entered the 

building at the curb openings before the temporary tarp was placed.

Figure 6-90: 

Although this 18,000-pound HVAC unit was attached to 

its curb with 16 straps, it blew off the building during 

Hurricane Ivan. (Florida, 2004) 

To anchor fans, small HVAC units, and relief air hoods, the minimum 

attachment schedule provided in Table 6-1 is recommended. The attachment of the curb to the roof deck also needs to be designed and 

constructed to resist wind loads. The cast-in-place concrete curb shown 

in Figure 6-91 was cold-cast over a concrete roof deck. Dowels were 

not installed between the deck and curb, hence a weak connection 

occurred.

Mechanical penetrations through the elevator penthouse roof and walls must possess 

adequate wind and water resistance to 

ensure continuity of elevator service (see 

Section 6.3.3.4). In addition to paying special attention to equipment attachment, air 

intakes and exhausts should be designed 

and constructed to prevent wind-driven 

water from entering the penthouse.
6-96 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Table 6-1: Number of #12 screws for base case attachment of rooftop equipment

Case 

No Curb Size and Equipment Type Equipment Attachment

Fastener Factor for 

Each Side of Curb 

or Flange

1 12" x 12" Curb with Gooseneck Relief 

Air Hood Hood Screwed to Curb 1.6

2 12" x 12" Gooseneck Relief Air Hood 

with Flange 

Flange Screwed to 22 Gauge Steel 

Roof Deck 2.8

3 12" x 12" Gooseneck Relief Air Hood 

with Flange

Flange Screwed to 15/32" OSB Roof 

Deck 2.9

4 24" x 24" Curb with Gooseneck Relief 

Air Hood Hood Screwed to Curb 4.6

5 24" x 24" Gooseneck Relief Air Hood 

with Flange

Flange Screwed to 22 Gauge Steel 

Roof Deck 8.1

6 24" x 24" Gooseneck Relief Air Hood 

with Flange

Flange Screwed to 15/32" OSB Roof 

Deck 8.2

7 24" x 24" Curb with Exhaust Fan Fan Screwed to Curb 2.5

8 36" x 36" Curb with Exhaust Fan Fan Screwed to Curb 3.3

9 5'-9" x 3'- 8" Curb with 2'- 8" high 

HVAC Unit HVAC Unit Screwed to Curb 4.5*

10 5'-9" x 3'- 8" Curb with 2'- 8" high 

Relief Air Hood Hood Screwed to Curb 35.6*

Notes to Table 6-1: 

1. The loads are based on ASCE 7-05. The resistance includes equipment weight. When using ASCE 7-10, convert the 7-10 Category 

III / IV basic wind speed to a 7-05 basic wind speed as follows: 7-10 speed divided by the square root of (1.15 x 1.6) = 7-05 speed.

2. The Base Case for the tabulated numbers of #12 screws (or 1⁄4 pan-head screws for flange-attachment) is a 90-mph basic wind 

speed, 1.15 importance factor, 30' building height, Exposure C, using a safety factor of 3. The 7-05 Base Case is equivalent to 120 

mph for 7-10 Risk Category III and IV buildings.

3. For other basic wind speeds, multiply the tabulated number of #12 screws by to determine the required number 

of #12 screws (or 1⁄4 pan-head screws) required for the desired basic wind speed, VD (mph). 

4. For other roof heights up to 200', multiply the tabulated number of #12 screws by (1.00 + 0.003 [h - 30]) to determine the required 

number of #12 screws or 1⁄4 pan-head screws for buildings between 30’ and 200’.

Example A: 24" x 24" exhaust fan screwed to curb (table row 7), Base Case conditions (see Note 1): 2.5 screws per side; therefore, 

round up and specify 3 screws per side.

Example B: 24" x 24" exhaust fan screwed to curb (table row 7), Base Case conditions, except 120 mph: 1202 x 1 ÷ 902 = 1.78 x 2.5 

screws per side = 4.44 screws per side; therefore, round down and specify 4 screws per side.

Example C: 24" x 24" exhaust fan screwed to curb (table row 7), Base Case conditions, except 150' roof height: 1.00 + 0.003 (150' - 

30') = 1.00 + 0.36 = 1.36 x 2.5 screws per side = 3.4 screws per side; therefore, round down and specify 3 screws per side.

* This factor only applies to the long sides. At the short sides, use the fastener spacing used at the long sides.

( ) V2

D

902
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Fan cowling attachment: Fans are frequently blown off their curbs because 

they are poorly attached. When fans are well attached, the cowlings frequently blow off during high winds (see Figure 6-92). Blown-off cowlings 

can tear roof membranes and break glazing. Unless the fan manufacturer 

specifically engineered the cowling attachment to resist the design wind 

load, cable tie-downs (see Figure 6-93) are recommended to avoid cowling blow-off where the basic 

wind speed is greater than 120 mph.31 For fan cowlings less than 4 feet in diameter, 1/8-inch diameter 

stainless steel cables are recommended. For larger 

cowlings, use 3/16-inch diameter cables. When the 

basic wind speed is 165 mph or less, specify two cables.32 Where the basic wind speed is greater than 

165 mph, specify four cables. To minimize leakage 

potential at the anchor point, it is recommended that the cables be adequately anchored to the 

equipment curb (rather than anchored to the roof 

deck). The attachment of the curb itself also needs 

to be designed and specified. 

31 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph.

32 The 165-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 120 mph. 

Figure 6-91: 

The gooseneck on 

this building remained 

attached to the curb, but 

the curb detached from 

the deck. Typhoon Paka 

(Guam, 1997)

To avoid corrosion-induced failure (Figure 

6-105), it is recommended that exteriormounted mechanical, electrical, and 

communications equipment be made of 

nonferrous metals, stainless steel, or steel 

with minimum G-90 hot-dip galvanized 

coating for the equipment body, stands, 

anchors, and fasteners. When equipment 

with enhanced corrosion protection is not 

available, the designer should advise the 

building owner that periodic equipment 

maintenance and inspection is particularly 

important to avoid advanced corrosion and 

subsequent equipment damage during a 

windstorm.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-92: 

Cowlings blew off 

two of the three fans. 

Note also the loose 

LPS conductors and 

missing walkway pad 

(red arrow). Estimated 

wind speed: 140–160 

mph. Hurricane Charley 

(Florida, 2004)

Figure 6-93: 

Cables were attached 

to prevent the cowling 

from blowing off. 

Typhoon Paka (Guam, 

1997)

Ductwork: To avoid wind and wind-borne debris damage to rooftop ductwork, it is recommended that ductwork not be installed on the roof (see 

Figure 6-138). If ductwork is installed on the roof, it is recommended 

that the ducts’ gauge and the method of attachment be able to resist the 

design wind loads. 

Condenser attachment: In lieu of placing rooftop-mounted condensers 

on wood sleepers resting on the roof (see Figure 6-94), it is recommended that condensers be anchored to equipment stands. The attachment of 

the stand to the roof deck also needs to be designed to resist the design 

loads. In addition to anchoring the base of the condenser to the stand, 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

two metal straps with two side-by-side #12 screws or bolts with proper end 

and edge distances at each strap end are recommended where the basic 

wind speed is greater than 120 mph (see Figure 6-95).33

33 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph. 

Figure 6-94: 

These condensers 

were blown off their 

sleepers. Displaced 

condensers can rupture 

roof membranes and 

refrigerant lines. 

Estimated wind 

speed: 120 mph. 

Hurricane Katrina 

(Mississippi) 

Figure 6-95: 

This condenser 

had supplemental 

attachment straps (see 

red arrows). Typhoon 

Paka (Guam, 1997)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Vibration isolators: If vibration isolators are used to mount equipment, 

only those able to resist design uplift loads should be specified and installed, or an alternative means to accommodate uplift resistance should 

be provided (see Figure 6-96).

Boiler and exhaust stack attachment: To avoid wind damage to boiler 

and exhaust stacks, wind loads on stacks should be calculated and guywires should be designed and constructed to resist the loads. Toppled 

stacks, as shown at the building in Figure 6-97, 

can allow water to enter the building at the stack 

penetration, damage the roof membrane, and 

become wind-borne debris. The designer should 

advise the building owner that guy-wires should 

be inspected annually to ensure they are taut.

Figure 6-96: 

Failure of vibration isolators that provided lateral resistance but no uplift 

resistance caused equipment damage. A damaged vibration isolator is 

shown in the inset. Estimated wind speed: 120 mph. Hurricane Katrina 

(Mississippi, 2005)

Three publications pertaining to seismic 

restraint of equipment provide general information on fasteners and edge distances:

n FEMA 412, Installing Seismic 

Restraints for Mechanical Equipment 

(2002)

n FEMA 413, Installing Seismic 

Restraints for Electrical Equipment

(2004b)

n FEMA 414, Installing Seismic 

Restraints for Duct and Pipe (2004a) 
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-101

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Figure 6-97: 

Guyed flue blew over 

(red arrow indicates one 

of the guys). Estimated 

wind speed: 92 mph. 

Hurricane Ike (Texas, 

2008)

Figure 6-98: 

The school shown in 

Figure 6-65 also had 

an access panel blow 

off. Blown-off panels 

can puncture roof 

membranes, break 

glazing, and cause 

injury. Estimated wind 

speed: 85–95 mph. 

Hurricane Ivan (Florida, 

2004)

Access panel attachment: Equipment access panels frequently blow off 

(see Figure 6-98). Unless the equipment manufacturer specifically engineered the panel attachment to resist the design wind load, job-site 

modifications, such as attaching hasps and locking devices like carabiners, are recommended. The modification details need to be customized. 

Detailed design may be needed after the equipment has been delivered 

to the job site. Modification details should be approved by the equipment manufacturer.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-99: 

The school shown in 

Figures 6-65 and 6-98 

also experienced gas 

line rupture (shown 

by the lines dangling 

over the side of the 

building). Estimated 

wind speed: 85–95 mph. 

Hurricane Ivan (Florida, 

2004)

Natural gas and condensate drain lines: Natural gas lines and condensate 

drain lines serving rooftop HVAC units are seldom anchored to resist 

wind loads. Gas line rupture can be due to lack of line anchorage or 

due to HVAC unit blow-off (see Figures 6-57 and 6-99). Where the basic 

wind speed is greater than 120 mph,34 it is recommended that gas line 

supports be designed and constructed to resist the design wind load (see 

Figure 6-100). 

34 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph.

Figure 6-100: 

At a periodic gas line 

support on this roof, a 

steel angle was welded 

to a pipe that was 

anchored to the roof 

deck. A strap looped 

over the gas line and 

was bolted to the 

support angle. Such a 

connection provides 

resistance to lateral and 

uplift loads.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Although blow-off of condensate drain lines is not as potentially catastrophic as rupture of gas lines, blown off condensate drain lines can 

puncture roof membranes, break glazing, and cause injury (see Figure 

6-101). Where the basic wind speed is greater than 120 mph,35 it is 

recommended that condensate drain line supports be designed and constructed to resist the design wind load. 

Equipment screens:  Screens around rooftop equipment are frequently 

blown away (see Figure 6-102). Screens should be designed to resist the 

wind load derived from ASCE 7. Since the effect of screens on equipment 

wind loads is unknown, the equipment attachment behind the screens 

should be designed to resist the design load. 

Water Infiltration

During high winds, wind-driven rain can be driven through air intakes 

and exhausts unless special measures are taken. Louvers should be designed and constructed to prevent leakage between the louver and wall. 

The louver itself should be designed to avoid water being driven past 

the louver. However, it is difficult to prevent infiltration during very high 

winds. Designing sumps with drains that will intercept water driving past 

louvers or air intakes should be considered. ASHRAE 62.1 provides some 

information on rain and snow intrusion. The Standard 62.1 User’s Manual 

(2007a) provides additional information, including examples and illustrations of various designs.

35 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph. 

Figure 6-101: 

These two condensate 

drain lines detached 

from their HVAC 

units. They had not 

been anchored to 

the roof. Estimated 

wind speed: 125 mph. 

Hurricane Katrina 

(Mississippi, 2005)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

6.3.4.2 Nonstructural Systems and Mechanical Equipment in 

Hurricane-Prone Regions

Mechanical Penthouses:  By placing equipment in mechanical penthouses rather than leaving them exposed on the roof, equipment can 

be shielded from high-wind loads and wind-borne debris (see Figure 

6-103). Although screens (such as shown in Figure 6-102) could be designed and constructed to protect equipment from horizontally flying 

debris, they are not effective in protecting equipment from missiles that 

have an angular trajectory. It is therefore recommended that mechanical equipment be placed inside mechanical penthouses. The penthouse 

itself should be designed and constructed in accordance with the recommendations given in Sections 6.3.2.2, 6.3.3.5, and 6.3.3.7.

If rooftop ductwork is exposed on the roof, and if there are flexible connectors between the ducts and fans, the connectors may be punctured 

by wind-borne debris. If equipment is not protected by a penthouse, the 

following is recommended:

n Because of their small size, the potential for a flexible connector to 

be punctured by wind-borne debris is typically very 

low. However, if site-specific conditions present an 

unusually high potential for debris damage, it is 

recommended that the flexible connectors be protected by equipment screens or a custom-designed 

shield.

Figure 6-102:

Equipment screen 

panels can puncture 

roof membranes, break 

glazing, and cause 

injury. Estimated wind 

speed: 105–115 mph. 

Hurricane Ivan (Florida, 

2004) 

As part of annual roof inspections prior to 

hurricane season, it is recommended that 

all flexible connectors be inspected. Those 

found to be in a weathered condition (e.g., 

cracked, torn, or embrittled) should be immediately replaced.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Roof drainage:  Roof drains and scuppers have the potential to be 

blocked by leaves, tree limbs, and other wind-borne debris during a 

hurricane (see Figure 6-104). If primary and overflow drains/scuppers 

become blocked, development of deep ponding water may inundate 

base flashings and cause leakage problems or lead to roof collapse. 

To avoid problems with blocked drains and scuppers, the following are 

recommended:

n Scuppers – Only a relatively small scupper is 

needed to drain a large roof area, provided 

the scupper opening is not blocked by debris. 

However, since small openings are more easily 

blocked than larger openings, it is recommended that scupper openings be much larger than 

normal. It is recommended that scupper openings be a minimum of 24 inches wide and 16 

inches high. In addition, it is recommended 

that the distance between scuppers be such that, in the event a scupper becomes blocked, the adjacent scuppers have sufficient capacity 

to drain the roof.

n Roof drains – Avoiding blockage of drains is more problematic than 

avoiding blockage of scuppers. Drain lines need to be protected 

by domes to prevent debris from flowing into the lines and blocking them. For domes to be effective in protecting drain lines from 

Figure 6-103: 

This exhaust fan 

was impacted by 

wind-borne debris. 

Although it is often 

impractical to place 

all equipment such as 

fans in penthouses, 

doing so to the extent 

possible avoids debris 

damage. Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005) 

As part of pre-storm preparations, drains, 

scuppers, and gutters should be cleaned of 

debris in order to maximize their effectiveness in draining the roof and minimize the 

potential for their blockage during a hurricane (see Figure 6-32).
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

blockage, the dome openings must be relatively small. To provide 

overflow protection, it is recommended that overflow scuppers be 

provided. Where drainage patterns necessitate that overflow protection be provided by overflow drains (rather than, or in addition 

to, overflow scuppers), it is recommended that additional overflow 

drains be installed. By doing so, if both a main drain and its nearby 

overflow drain become blocked, the additional overflow drain in the 

vicinity can provide drainage and avoid roof collapse.

6.3.4.3 Exterior-Mounted Electrical and Communications Equipment

Damage to exterior-mounted electrical equipment is infrequent, mostly 

because of its small size (e.g., disconnect switches). Exceptions include 

communication towers, surveillance cameras, electrical service masts, 

satellite dishes, and LPSs. The damage is typically caused by inadequate 

mounting as a result of failure to perform wind load calculations and 

anchorage design. Damage is also sometimes caused by corrosion (see 

Figure 6-105 and text box in Section 6.3.4.1 regarding corrosion).

Figure 6-104: 

Leaf debris and ponding 

near a scupper (red and 

blue arrows). The yellow 

arrow indicates a piece 

of coping that blew off 

an upper roof shown in 

Figure 6-72. Estimated 

wind speed: 92 mph. 

Hurricane Ike (Texas, 

2008)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Communication towers and poles:  NFPA 70 provides guidance for determining wind loads on 

power distribution and transmission poles and 

towers. AASHTO LTS-4-5 provides guidance for 

determining wind loads on light fixture poles 

(standards).

Both ASCE 7 and ANSI/TIA-222-G contain wind load provisions for 

communication towers (structures). The IBC allows the use of either approach. The ASCE wind load provisions are generally consistent with 

those contained in ANSI/TIA-222-G. ASCE 7, however, contains provisions for dynamically sensitive towers that are not present in the ANSI/

TIA standard. ANSI/TIA classifies towers according to their use (Class I, 

Class II, and Class III). This manual recommends that towers (including 

antennae) that are mounted on, located near, or serve schools be designed as Class III structures.

Collapse of both large and small communication towers is quite common 

during high-wind events (see Figure 6-106). These failures often result in 

complete loss of communication capabilities. In addition to the disruption of communications, collapsed towers can puncture roof membranes 

and allow water leakage into the school, unless the roof system incorporated a secondary membrane (as discussed in Section 6.3.3.7). At the 

tower shown in Figure 6-106 the anchor bolts were pulled out of the 

deck, which resulted in a progressive peeling of the fully adhered singleply roof membrane. Tower collapse can also injure or kill people. 

Figure 6-105: 

Collapsed light fixtures 

caused by severe 

corrosion (see inset). 

Estimated wind 

speed: 105–115 mph. 

Hurricane Ivan (Florida, 

2004)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

See Sections 6.3.1.1 and 6.3.1.5 regarding site considerations for light 

fixture poles, power poles, and electrical and communications towers.

Electrical service masts: Service mast failure is typically caused by collapse 

of overhead power lines, which can be avoided by using underground 

service. Where overhead service is provided, it is recommended that the 

service mast not penetrate the roof. Otherwise, a downed service line 

could pull on the mast and rupture the roof membrane. 

Satellite dishes: For the satellite dish shown in Figure 6-107, the dish mast 

was anchored to a large metal pan that rested on the roof membrane. 

CMU was placed on the pan to provide overturning resistance. This anchorage method should only be used where calculations demonstrate 

that it provides sufficient resistance. In this case, the wind approached 

the satellite dish in such a way that it experienced very little wind pressure. In hurricane-prone regions, use of this anchorage method is not 

recommended (see Figure 6-108). 

Lightning protection systems (LPS): For attachment of building LPS located where the basic wind speed is in excess of 120 mph,36 see the following 

section on attaching LPS in hurricane-prone regions.

36 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph. 

Figure 6-106: 

The collapse of the 

antenna tower at 

this school caused 

progressive peeling of 

the roof membrane. Also 

note that the exhaust fan 

blew off the curb, but 

the high parapet kept 

it from blowing off the 

roof. Hurricane Andrew 

(Florida, 1992)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.3.4.4 Lightning Protection Systems in Hurricane-Prone Regions

LPSs frequently become disconnected from rooftops during hurricanes. 

Displaced LPS components can puncture and tear roof coverings, thus 

allowing water to leak into buildings (see Figures 6-109 and 6-110). 

Prolonged and repeated slashing of the roof membrane by loose conductors (“cables”) and puncturing by air terminals (“lightning rods”) 

can result in lifting and peeling of the membrane. Also, when displaced, 

the LPS is no longer capable of providing lightning protection in the vicinity of the displaced conductors and air terminals. 

Figure 6-107: Common 

anchoring method for 

satellite dish. Estimated 

wind speed: 85–95 mph. 

Hurricane Ivan (Florida, 

2004) 

Figure 6-108: 

A satellite dish anchored 

similarly to that shown 

in Figure 6-107 was 

blown off this five-story 

building. Estimated 

wind speed: 140–160 

mph. Hurricane Charley 

(Florida, 2004)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Lightning protection standards such as NFPA 780 and UL 96A provide 

inadequate guidance for attaching LPSs to rooftops in hurricane-prone 

regions, as are those recommendations typically provided by LPS and 

roofing material manufacturers. LPS conductors are typically attached to 

the roof at 3-foot intervals. The conductors are flexible, and when they 

are exposed to high winds, the conductors exert dynamic loads on the 

conductor connectors (“clips”). Guidance for calculating the dynamic 

loads does not exist. LPS conductor connectors typically have prongs 

to anchor the conductor. When the connector is well-attached to the 

Figure 6-109: 

An air terminal (red 

arrow) debonded from 

the roof. Even though 

the school had a tough 

membrane (modified 

bitumen), the displaced 

air terminal punctured 

the membrane in two 

locations (blue arrows). 

Hurricane Charley 

(Florida, 2004)

Figure 6-110: 

View of an end of a 

conductor that became 

disconnected. Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005) 
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

roof surface, during high winds the conductor frequently bends back 

the malleable connector prongs (see Figure 6-111). Conductor connectors have also debonded from roof surfaces during high winds. Based 

on observations after Hurricane Ike and other hurricanes, it is apparent 

that pronged conductor connectors typically have not provided reliable 

attachment. 

To enhance the wind performance of LPS, the following are recommended: 

Parapet attachment: When the parapet is 12 inches high or greater, it 

is recommended that the air terminal base plates and conductor connectors be mechanically attached with #12 screws that have minimum 

11⁄4-inch embedment into the inside face of the parapet nailer and be 

properly sealed for watertight protection. Instead of conductor connectors that have prongs, it is recommended that mechanically attached 

looped connectors be installed (see Figure 6-112). 

Figure 6-111: 

This conductor 

connector was adhered 

to the coping. The 

conductor deformed 

the connector prongs 

under wind pressure, 

and pulled away from 

the connector. Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Attachment to built-up, modified bitumen, and single-ply membranes: For 

built-up and modified bitumen membranes, attach the air terminal base 

plates with asphalt roof cement. For single-ply membranes, attach the air 

terminal base plates with pourable sealer (of the type recommended by 

the membrane manufacturer). 

In lieu of attaching conductors with conductor connectors, it is recommended that conductors be attached with strips of membrane installed 

by the roofing contractor. For built-up and modified bitumen membranes, use strips of modified bitumen cap sheet, approximately 9 inches 

wide at a minimum. If strips are torch-applied, avoid overheating the 

conductors. For single-ply membranes, use self-adhering flashing strips, 

approximately 9 inches wide at a minimum. Start the strips approximately 3 inches from either side of the air terminal base plates. Use strips that 

are approximately 3 feet long, separated by a gap of approximately 3 

inches (see Figures 6-113 and 6-114).

Figure 6-112: 

This conductor was 

attached to the 

coping with a looped 

connector. Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005)

Figure 6-113: Plan showing conductor attachment
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

As an option to securing the conductors with stripping plies, conductor 

connectors that do not rely on prongs could be used (such as the one 

shown in Figure 6-115). However, the magnitude of the dynamic loads 

induced by the conductor is unknown, and there is a lack of data on the 

resistance provided by adhesively attached connectors. For this reason, 

attachment with stripping plies is the preferred option, because the plies 

shield the conductor from the wind. If adhesive-applied conductor connectors are used, it is recommended that they be spaced more closely 

than the 3-foot spacing required by NFPA 780 and UL 96A. Depending 

on wind loads, a spacing of 6 to 12 inches on center may be needed in 

the corner regions of the roof, with a spacing of 12 to 18 inches on center 

at roof perimeters (see ASCE 7 for the size of corner regions).

Mechanically attached single-ply membranes:  It is recommended that 

conductors be placed parallel to, and within 8 inches of, membrane fastener rows. Where the conductor falls between or is perpendicular to 

membrane fastener rows, install an additional row of membrane fasteners 

where the conductor will be located, and install a membrane cover-strip 

over the membrane fasteners. Place the conductor over the cover-strip 

and secure the conductor as recommended above.

By following the above recommendations, additional rows of membrane fasteners (beyond those 

needed to attach the membrane) may be needed 

to accommodate the layout of the conductors. The 

additional membrane fasteners and cover-strip 

should be coordinated with, and installed by, the 

roofing contractor.

Figure 6-114: 

Use of intermittent 

membrane flashing 

strips to secure an LPS 

conductor, as illustrated 

in Figure 6-113 

PHOTO COURTESY 

OF: MACGREGOR ASSOCIATES 

ARCHITECTS.

Figure 6-115: 

Adhesively attached 

conductor connector that 

does not use prongs

It is recommended that the building designer advise the building owner to have 

the LPS inspected each spring, to verify 

that connectors are still attached to the roof 

surface, that they still engage the conductors, and that the splice connectors are still 

secure. Inspections are also recommended 

after high-wind events.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Standing seam metal roofs: It is recommended that pre-manufactured, 

mechanically attached clips that are commonly used to attach various 

items to roof panels be used. After anchoring the clips to the panel ribs, 

the air terminal base plates and conductor connectors are anchored 

to the panel clips. In lieu of conductor connectors that have prongs, it 

is recommended that mechanically attached looped connectors be installed (see Figure 6-112). 

Conductor splice connectors: In lieu of pronged splice connectors (see 

Figure 6-116), bolted splice connectors are recommended because they 

provide a more reliable connection (see Figure 6-117). It is recommended that strips of flashing membrane (as recommended above) be placed 

approximately 3 inches from either side of the splice connector to minimize conductor movement and to avoid the possibility of the conductors 

becoming disconnected. To allow for observation during maintenance 

inspections, do not cover the connectors.

Figure 6-116: 

If conductors detach 

from the roof, they 

are likely to pull out 

from pronged splice 

connectors. Estimated 

wind speed: 90–100 

mph. Hurricane Charley 

(Florida, 2004)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.3.5 Municipal Utilities In Hurricane-Prone Regions

Hurricanes typically disrupt municipal electrical service, and often they 

disrupt telephone (both cellular and land-line), water, and sewer services. These disruptions may last from several days to several weeks. 

Electrical power disruptions can be caused by damage to power generation stations and by damaged lines, such as major 

transmission lines and secondary feeders. Water 

disruptions can be caused by damage to water treatment or well facilities, lack of power for pumps or 

treatment facilities, or by broken water lines caused 

by uprooted trees. Sewer disruptions can be caused 

by damage to treatment facilities, lack of power for 

treatment facilities or lift stations, or broken sewer 

lines. Phone disruptions can be caused by damage 

at switching facilities and collapse of towers. 

For schools that will be used as hurricane evacuation shelters, provisions 

should be made to accommodate disruption of municipal utilities, as discussed in 6.3.5.1, 6.3.5.2, and 6.3.5.3. 

For schools that will be used as recovery centers after a hurricane, it is recommended that the schools be equipped with an emergency generator 

or have pre-hurricane arrangements for delivery of a portable generator to the school prior to the recovery center becoming operational (see 

Figure 6-118). (Note: It could take a few or several days for a portable generator to be delivered.) If a portable generator rather than a permanent 

Figure 6-117: 

Bolted splice connectors 

are recommended 

to prevent free ends 

of connectors from 

being whipped around 

by wind. Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005)

When a portion of a school is designed to 

function as a safe room, additional design 

criteria for backup or emergency power for 

the safe room portion of the school must 

meet additional performance criteria set 

forth in FEMA 361. In addition to backup 

power criteria, the safe room guidance identifies lighting, sewer, and water services.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

on-site generator will be relied upon for power, it is recommended that 

an exterior box for single pole cable cam locking connectors be provided 

so that the portable generator can be quickly connected. The generator 

should be capable of providing power to items listed in Section 6.3.5.1. 

To provide for back-up water and sewer service, either the provisions discussed in 6.3.5.2 and 6.3.5.3, or pre-hurricane arrangements for delivery 

of water and portable toilets to the school prior to the recovery center 

becoming operational, are recommended.

For schools that will not be used as hurricane evacuation shelters or recovery centers, in lieu of spending money to incorporate provisions to 

accommodate disruption of municipal utilities, school re-opening could 

be delayed until municipal utilities are operational. (Note: In many instances, schools can’t re-open for a couple of weeks after a hurricane 

because of various issues [such as debris removal from roads and school 

grounds] unrelated to utilities.) 

6.3.5.1 Electrical Power 

It is recommended that schools that will be used as hurricane evacuation shelters be provided with an emergency generator to supply power 

for lighting, exit signs, fire alarm system, fire sprinkler pump, public address system, and for mechanical ventilation. The emergency generator 

should be rated for prime power (continuous operation). 

Generators should be placed inside wind-borne debris resistant buildings (see recommendations in Sections 6.3.2.2, 6.3.3.5, and 6.3.3.7) so 

Figure 6-118: 

In lieu of permanent 

on-site emergency 

generators, portable 

generators can be 

an economical way 

to provide electrical 

power to schools used 

as hurricane recovery 

centers. Estimated 

wind speed: 108 mph. 

Hurricane Ike (Texas, 

2008)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

that they are not susceptible to damage from debris or tree fall. Locating 

generators outdoors or inside weak enclosures (see Figure 6-119) is not 

recommended. 

It is recommended that wall louvers for generators 

be capable of resisting the test Missile E load specified in ASTM E 1996. Alternatively, wall louvers can 

be protected with a debris-resistant screen wall so 

that wind-borne debris is unable to penetrate the 

louvers and damage the generators. If a screen wall 

is used, it should be designed to allow adequate air 

flow to the generator in order to avoid overheating 

the generator. 

It is recommended that sufficient on-site fuel storage be provided to 

allow the facility’s emergency generator to operate at full capacity for 

a minimum of 72 hours (3 days). It is recommended that fuel storage 

tanks, piping, and pumps be placed inside wind-borne debris resistant 

buildings, or underground. If the site is susceptible to flooding, refer to 

Chapter 5 recommendations. 

6.3.5.2 Water Service 

It is recommended that schools that will be used as hurricane evacuation shelters be provided with an independent water supply via a 

well or on-site water storage for drinking water, fire sprinklers (if they 

Figure 6-119: 

The tree shown by 

the red line nearly 

fell on the emergency 

generator (red arrow). 

Estimated wind 

speed: 110 mph. 

Hurricane Ike (Texas, 

2008)

Generators fired by natural gas are available. Use of natural gas alleviates various 

potential problems associated with on-site 

storage of diesel fuel (such as adequate 

quantity of fuel for prolonged outages). 

However, if the natural gas supply is shut 

down by the gas supplier, the school will 

be left without power.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

exist), and water-operated toilets. If water is needed for cooling towers, the independent water supply should be sized to accommodate the 

system. 

It is recommended that pumps for wells or on-site storage be connected 

to an emergency power circuit, that a valve be provided on the municipal service line, and that on-site water treatment capability be provided 

where appropriate.

6.3.5.3 Sewer Service 

It is recommended that schools that will be used as hurricane evacuation shelters be provided with portable chemical toilets or an alternative 

means of waste disposal, such as a temporary storage tank that can be 

pumped out by a local contractor. It is also recommended that back-flow 

preventors be provided in the sewage discharge lines.

6.3.6 Post-Design Considerations in Hurricane-Prone Regions

In addition to adequate design, proper attention must be given to construction, post-occupancy inspections, and maintenance. 

6.3.6.1 Construction Contract Administration 

It is important for school districts in hurricane-prone regions to obtain 

the services of a professional contractor who will execute the work described in the contract documents in a diligent and technically proficient 

manner. The frequency of field observations and extent of special inspections and testing should be greater than those employed on schools 

that are not in hurricane-prone regions. The frequency of field observations and extent of special inspections and testing should be even greater 

for schools that will be used as hurricane evacuation shelters.

6.3.6.2 Periodic Inspections, Maintenance, and Repair 

The recommendations given in Section 6.3.1.4 

for post-occupancy and post-storm inspections, 

maintenance, and repair are crucial for schools in 

hurricane-prone regions. Failure of a building component that was not maintained properly, repaired, 

or replaced, can present a considerable risk of injury or death to occupants if the school is used as 

a hurricane evacuation shelter, and the continued 

operation of the facility can be jeopardized.

Refer to the two text boxes in Sections 

6.3.4.2 that addresses inspection of flexible connectors at ducts and inspection of 

drains, scuppers, and gutters. Also refer 

to the text box in Section 6.3.4.4 that addresses inspection of lightning protection 

systems.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.4 Remedial Work on Existing Facilities 

Many existing schools need to strengthen their structural or 

building envelope components. The reasons for this are the 

deterioration that has occurred over time, or inadequate facility strength to resist current design level winds. It is recommended that 

school districts have a vulnerability assessment performed by a qualified 

architectural and engineering team. A vulnerability assessment should 

be performed for all facilities older than 5 years. An assessment is recommended for all facilities located in areas where the basic wind speed 

is greater than 120 mph37 (even if the facility is younger than 5 years—

see Figure 6-120). It is particularly important to perform vulnerability 

assessments on schools located in hurricane-prone and tornado-prone 

regions.

Components that typically make buildings constructed before the early 1990s vulnerable to high winds are weak non-load-bearing masonry 

walls, poorly connected precast concrete panels, long-span roof structures with limited uplift resistance, inadequately connected roof decks, 

weak glass curtain walls, building envelope, and exterior-mounted 

equipment. Although the technical solutions to these problems are not 

difficult, the cost of the remedial work is typically quite high. If funds 

are not available for strengthening or replacement, it is important to 

minimize the risk of injury and death by evacuating areas adjacent to 

37 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. 

If ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph. 

Figure 6-120: 

The roof and a portion 

of the EIFS on this 

5-year-old building blew 

off. Water leaked into 

the floor below. The 

floor was taken out of 

service for more than 

a month. Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

weak non-load-bearing walls, weak glass curtain walls, and areas below 

long-span roof structures when winds above 60 mph are forecast. 

As a result of building code changes and heightened awareness, some 

of the common building vulnerabilities have generally been eliminated for facilities constructed in the mid-1990s or later. Components that 

typically remain vulnerable to high winds are the building envelope 

and exterior-mounted mechanical, electrical, and communications 

equipment. Many failures can be averted by identifying weaknesses 

and correcting them. 

By performing a vulnerability assessment, items that need to be 

strengthened or replaced can be identified and prioritized. A proactive 

approach in mitigating weaknesses can save significant sums of money 

and decrease disruption or total breakdown in school operations after 

a storm. For example, a vulnerability assessment on a building such as 

that shown in Figure 6-120 may identify weakness 

of the roof membrane and/or EIFS. Replacing 

weak components before a storm is much cheaper 

than replacing them and repairing consequential 

damages after a storm, and proactive work avoids 

the loss of use while repairs are made. 

If budget constraints prohibit timely evaluation 

of all schools in the district, then facility evaluation should be prioritized, commensurate with 

district’s needs and the perceived vulnerabilities 

of the facilities. For example, schools that will be 

used as hurricane evacuation shelters, recovery 

centers after a hurricane, and facilities constructed before the early 

1990s would normally be evaluated first. Upon completion of the evaluations of the district’s facilities, the order in which remedial work will 

be scheduled should be prioritized.

For those schools that will be used as hurricane evacuation shelters or as 

recovery centers after a hurricane, the vulnerability assessment should 

also evaluate the facility’s capability of coping with loss of municipal 

utilities (i.e., electrical power, water, sewer, and communications).

A comprehensive guide for performing a vulnerability assessment 

and for remedial work on existing facilities is beyond the scope of this 

manual. However, the checklist in Section 6.6 provides a guide for 

vulnerability assessment, and the remainder of this Section provides 

examples of mitigation measures that are often applicable. 

Before beginning remedial work, it is necessary to understand all significant aspects 

of the vulnerability of a school with respect 

to wind and wind-driven rain. If funds are 

not available to correct all identified deficiencies, the work should be systematically 

prioritized so that the items of greatest 

need are corrected first. Mitigation efforts 

can be very ineffective if they do not address all items that are likely to fail.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.4.1 Structural Systems

As discussed in Section 6.1.4.1, roof decks on many facilities designed 

prior to the 1982 edition of the SBC and UBC and the 1987 edition of 

the NBC are very susceptible to failure. Poorly attached decks that are 

not upgraded are susceptible to blow-off, as shown in Figure 6-121. Decks 

constructed of cementitious wood-fiber, gypsum, and lightweight insulating concrete over form boards were commonly used on schools built in 

the 1950s and 1960s. In that era, these types of decks, as well as precast 

concrete decks, typically had very limited uplift resistance due to weak 

connections to the support structure. Steel deck attachment is frequently not adequate because of an inadequate number of welds, or welds of 

poor quality. Older buildings with overhangs are particularly susceptible 

to blow-off, as shown in Figure 6-121, because older codes provided inadequate uplift criteria.

A vulnerability assessment of the roof deck should include evaluating the 

existing deck attachment, spot checking the structural integrity of the 

deck (including the underside, if possible), and evaluating the integrity 

of the beams/joists. If the deck attachment is significantly overstressed 

under current design wind conditions or the deck integrity is compromised, the deck should be replaced or strengthened as needed. The 

evaluation should be conducted by an investigator experienced with the 

type of deck used on the building. 

Figure 6-121 

The cementitious 

wood-fiber deck panels 

blew off of much of 

the overhang at this 

school. Deck panel 

failure resulted in 

lifting and peeling of 

the roof system over 

a large area, exposure 

of the decking in 

the area shown by 

the blue arrows, and 

extensive interior water 

infiltration. Estimated 

wind speed: 105–115 

mph. Hurricane Ivan 

(Florida, 2004)

PHOTO COURTESY OF RICOWI, 

INC. PHOTO #:PD02-047 4-08-

4. PHOTOGRAPHER: PHIL 

DREGGER, TECHNICAL ROOF 

SERVICES, INC.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

The vulnerability assessment should also include evaluating the structural integrity of canopies, for as shown in Figure 6-41, these elements often 

lack sufficient wind resistance.

If a low-slope roof is converted to a steep-slope roof, the new support 

structure should be engineered and constructed to resist the wind loads 

and avoid the kind of damage shown in Figure 6-122.

6.4.2 Building Envelope

Because of the lack of field diagnostic equipment and test methods, it is 

quite difficult to accurately assess the wind and wind-driven rain vulnerability of the building envelope and rooftop equipment. Review of existing 

drawings (if available) often times reveal vulnerabilities. However, it is 

frequently necessary to perform selective destructive observation as part 

of the assessment. A successful assessment is dependent upon the school 

district budgeting sufficient funds for the assessment and upon the expertise, experience, and judgment of design professionals performing 

the assessment. The following recommendations apply to building envelope components of existing schools.

Figure 6-122: 

The steel truss 

superstructure installed 

on this school as 

part of a steep-slope 

conversion blew away 

because of inadequate 

attachment. Hurricane 

Marilyn (U.S. Virgin 

Islands, 1995)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

6.4.2.1 Windows and Skylights

Windows in older facilities may possess inadequate resistance to wind 

pressure. Window failures are typically caused by wind-borne debris, 

however, glazing or window frames may fail as a result of wind pressure 

(see Figure 6-123). Failure can be caused by inadequate resistance of the 

glazing, inadequate anchorage of the glazing to the frame, failure of the 

frame itself, or inadequate attachment of the frame to the wall. For older 

windows that are too weak to resist the current design pressures, window 

assembly replacement is recommended. 

Some older window assemblies have sufficient strength to resist the design pressure, but are inadequate to resist wind-driven rain. If the lack 

of water resistance is due to worn glazing gaskets or sealants, replacing 

the gaskets or sealant may be viable. In other situations, replacing the 

existing assemblies with new, higher-performance assemblies may be 

necessary. On-site testing in accordance with ASTM E 1105 can be used 

to evaluate wind-driven rain resistance of suspect windows (see Figure 

6-124). (Note: Shutters placed over windows to provide wind-borne debris protection should not be relied upon to protect against wind-driven 

rain. If existing windows are susceptible to debris and leakage, the windows should be replaced with new assemblies.)

Figure 6-123: 

Wind pressure caused 

the window frames on 

the upper floors to fail 

(red arrow). Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

It is recommended that all non-impact-resistant, exterior glazing located in hurricane-prone regions (with a basic wind speed of 135 mph or 

greater)38 be replaced with impact-resistant glazing or be protected with 

shutters, as discussed in Section 6.3.3.3. Shutters are typically a more 

economical approach for existing facilities. There are a variety of shutter types, all illustrated by Figures 6-125 to 6-128. Accordion shutters are 

permanently attached to the wall (Figure 6-125). When a hurricane is 

forecast, the shutters are pulled together and latched into place. Panel 

shutters (Figures 6-126 and 6-127) are made of metal or polycarbonate. 

When a hurricane is forecast, the shutters are taken from storage and inserted into metal tracks that are permanently mounted to the wall above 

and below the window frame as shown in Figure 6-126 (or fastened to the 

building as shown in Figure 6-127). The panels are locked into the frame 

with wing nuts or clips. Track designs that have permanently mounted studs for the nuts have been shown to be more reliable than track 

designs using studs that slide into the track. A disadvantage of panel shutters is the need for storage space. Roll-down shutters (Figure 6-128) can 

be motorized or pulled down manually. Motorized shutters are available 

with toggles that allow the shutter to be manually raised. The advantage 

of being able to open the shutter without electrical power is that if water 

leaked into the building and if the door or window protected by the shutter is operable, the shutter can be manually raised in order to facilitate 

venting (drying of the interior). 

38 The 135-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 100 mph. 

Figure 6-124: 

On-site water-spray 

testing in accordance 

with ASTM E 1105 can 

be used to evaluate 

wind-driven rain 

resistance. Older 

window assemblies 

such as the ones at 

this school are often 

quite susceptible to 

leakage. Estimated 

wind speed: 125 mph. 

Hurricane Katrina 

(Mississippi, 2005)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Figure 6-125:

This school has 

accordion shutters. 

Estimated wind 

speed: 105–115 mph. 

Hurricane Ivan (Florida, 

2004)

Figure 6-126: 

A metal panel shutter. 

Hurricane Georges 

(Puerto Rico, 1998) 
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Figure 6-127: 

Polycarbonate shutters 

were temporary 

screwed to the doors 

and wall adjacent to 

the window opening. 

An advantage of 

polycarbonate is its 

translucence, which 

allows daylight to enter 

the building without 

removing the shutters. 

Hurricane Francis 

(Florida, 2004)

Figure 6-128: 

This school has rolldown shutters. The 

toggle in the red circle 

allows the shutter to 

be manually raised. 

Estimated wind 

speed: 130–140 mph. 

Hurricane Charley 

(Florida, 2004)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

Deploying accordion or panel shutters a few stories above grade is expensive. Although motorized shutters have greater initial cost, their 

operational cost should be lower. Other options for providing missile 

protection on upper levels include replacing the existing assemblies 

with laminated glass assemblies, or installing permanent impact resistant screens. Engineered films are also available for application to 

the interior of the glass. The film needs to be anchored to the frame, 

and the frame needs to be adequately anchored to the wall. The film 

degrades over time and requires replacement (approximately every 

decade). Use of laminated glass or shutters/screens is recommended 

in lieu of engineered films.

6.4.2.2 Non-Load-Bearing Walls, Wall Coverings, and Soffits

Non-load-bearing walls, wall coverings, and soffits on existing schools 

should be carefully examined and evaluated for wind and wind-driven 

rain resistance. 

If the parapet is constructed of masonry, it is recommended that its wind 

resistance be evaluated and strengthened if found to be inadequate. The 

masonry parapet shown in Figure 6-129 fell onto the roof. Had it fallen 

in the other direction, it would have blocked the entry and would have 

had the potential to cause injury.

To identify weak EIFS systems so that corrective action can be taken to 

avoid the type of damage shown in Figures 6-61 and 6-62, on-site testing in 

accordance with ASTM E 2359 can be conducted. (Note: This test method 

is not capable of evaluating the wind resistance of the wall framing.) 

Figure 6-129: 

Collapsed unreinforced 

masonry parapet. 

Greensburg Tornado 

(Kansas, 2007)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

6.4.2.3 Roof Coverings

On-site testing in accordance with ASTM E 907 can be used to evaluate 

the uplift resistance of roof systems that have fully adhered membranes 

(see Figure 6-130). (Note: This test method is not capable of evaluating 

the uplift resistance of the roof deck.) 

For roofs with weak metal edge flashing or coping attachment, faceattachment of the edge flashing/coping (as shown in Figure 6-73) is a 

cost-effective approach to greatly improve the wind-resistance of the roof 

system. To improve the wind resistance of weak gutters, a cost-effective 

approach is to install straps as shown in Figure 6-77. Alternatively, if the 

gutter bracket attachment is sufficient to resist rotational force (as discussed in Section 6.3.3.6), but the gutter is not anchored to the brackets, 

fasteners can be installed to anchor the gutter to the bracket as shown in 

Figure 6-76.

The vulnerability assessment of roofs ballasted with aggregate, pavers, 

or cementitious-coated insulation boards, should determine whether 

the ballast complies with ANSI/SPRI RP-4. Corrective action is recommended for non-compliant, roof coverings. It is recommended that roof 

coverings with aggregate surfacing, lightweight pavers, or cementitiouscoated insulation boards on buildings located in hurricane-prone regions 

be replaced to avoid blow-off (see Figures 6-8, 6-13, 6-23, and 6-53). 

Figure 6-130: 

View of a 5-foot by 

5-foot negative pressure 

chamber used to 

evaluate roof system 

uplift resistance.
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

When planning the replacement of a roof covering, it is recommended that all existing roof covering be removed down to the deck rather 

than simply re-covering the roof. Tearing off the covering provides an 

opportunity to evaluate the structural integrity of the deck and correct deck attachment and other problems. For example, if a roof deck 

was deteriorated due to roof leakage (see Figure 6-131), the deterioration would likely not be identified if the roof was simply re-covered. 

By tearing off down to the deck, deteriorated decking like that shown 

in Figure 6-131 can be found and replaced. In addition, it is recommended that the attachment of the wood nailers at the top of parapets 

and roof edges be evaluated and strengthened where needed, to avoid 

blow-off and progressive lifting and peeling of the new roof membrane 

(see Figure 6-132). 

Figure 6-131: 

The built-up roof on this school was blown off after a 

few of the rotted wood planks detached from the joists. 

Estimated wind speed: 120 mph. Hurricane Katrina 

(Mississippi, 2005)
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

If the roof has a parapet, it is recommended that the inside of the parapet be properly prepared to receive the new base flashing. In many 

instances, it is prudent to re-skin the parapet with sheathing to provide 

a suitable substrate. Base flashing should not be applied directly to brick 

parapets because they have irregular surfaces that inhibit good bonding of the base flashing to the brick (see Figure 6-133). Also, if moisture 

drives into the wall from the exterior side of the parapet with base flashing attached directly to brick, the base flashing can inhibit drying of the 

wall. Therefore, rather than totally sealing the parapet with membrane 

base flashing, the upper portion of the brick can be protected by metal 

panels (as shown in Figure 6-88), which permits drying of the brick.

Figure 6-132: 

The nailer (red arrow) 

blew off an upper roof 

and landed on the roof 

below. The nailer was 

anchored to a brick wall. 

Some of the anchors 

pulled out of the brick, 

and some of the bricks 

blew away with the 

nailer. Estimated wind 

speed: 105–115 mph. 

Hurricane Ivan (Florida), 

2004

Figure 6-133: 

Failed base flashing 

adhered directly to the 

brick parapet. Estimated 

wind speed: 105 mph. 

Hurricane Katrina 

(Louisiana, 2005)
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MAKING SCHOOLS SAFE FROM HIGH WINDS 6

When reroofing a steep-sloped roof, if it does not have a continuous 

ridge vent, but one will be installed as part of the reroofing work, the following are recommended: 

n If the decking is intended to act as a diaphragm and the diaphragm 

loads are high, the typical technique of cutting a slot through the 

decking (as shown in Figure 6-134) can compromise the integrity 

of the diaphragm by interrupting the transfer of diaphragm load 

from one side of the ridge to the other. For guidance on cutting vent 

openings that do not compromise diaphragm integrity, see Section 

12.7.6 in FEMA 55. Note: An updated version of FEMA 55 is expected 

to be released in 2011.

n To prevent weakening of joists or trusses (as occurred at Figure 

6-134), prior to slotting the deck, the depth of the saw should be adjusted so that the blade is only slightly below the bottom of the deck.

6.4.3 Exterior-Mounted Equipment

Exterior-mounted equipment on existing schools should be carefully examined and evaluated. 

6.4.3.1 HVAC Units, Condensers, Fans, Exhaust Stacks, and Ductwork 

Where HVAC units are inadequately anchored to their curbs, or where 

the curb is inadequately attached, cables with turnbuckles should be attached to pipe anchors attached to the deck (see Figure 6-135). The 

pipe anchors should be stiff so that the top of the anchor is not pulled 

towards the unit by the cable (otherwise, the unit may lift and shift off 

the curb). 

Figure 6-134:

During a reroofing 

project a slot was cut 

in the plywood deck in 

order to allow air to flow 

from the attic to a new 

continuous ridge vent. 

The cutting depth of the 

saw was not adjusted 

for the thickness of the 

deck. The top 11⁄2 inch of 

each truss and a portion 

of the metal nailing 

plate was inadvertently 

cut.
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6 MAKING SCHOOLS SAFE FROM HIGH WINDS

If HVAC units have inadequately attached sheet metal hoods (see Figure 

6-136), sheet metal straps can be economically installed between the top 

of the hood and the side of the unit. Equipment access panels may also 

need to be modified to resist wind loads as discussed in Section 6.3.4.1. 

Besides avoiding damage to the unit, these types of retrofits can prevent 

blown-off hoods and panels from causing injury and damaging the roof 

membrane or other building components. 

Figure 6-135: 

To strengthen 

attachment of this HVAC 

unit, robust pipe anchors 

were attached to the 

deck and cables with 

turnbuckles installed.

Figure 6-136: 

At this school, the hood 

on this HVAC unit was 

inadequately attached. 

A strap between the 

hood and unit can 

be economically 

installed to avoid this 

problem. Estimated 

wind speed: 110 mph. 

Hurricane Ike (Texas, 

2008)
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Where condensers are mounted to curbs that are adequately anchored 

to the deck, straps can be installed as shown in Figure 6-95 if the condenser attachment is inadequate. If condensers are mounted on sleepers 

(see Figure 6-137), then the condensers should be re-mounted and anchored to curbs or stands that are anchored to the roof deck. 

If exhaust stacks such as those shown in Figure 6-137 are inadequately 

anchored, guys attached to pipe anchors such as those shown in Figure 

6-135 should be installed. To avoid blow-off of rain caps as shown in 

Figure 6-137, additional straps or screws may need to be installed. 

To avoid blow-off of fan cowlings, installation of cables is recommended 

as discussed in Section 6.3.4.1.

If rooftop ductwork exists, its wind resistance should 

be carefully evaluated. As shown in Figure 6-138, 

blown-off ducts can allow a substantial amount of 

rain to enter a building.

Figure 6-137: 

These condensers 

were simply mounted 

on wood sleepers 

that rested on the 

roof surface. Note the 

damaged exhaust stacks 

and missing rain caps 

(red oval). Estimated 

wind speed: 105 mph. 

Hurricane Katina 

(Mississippi, 2005)

Fastening rooftop equipment to curbs, as 

discussed in Section 6.3.4.1, is a cost-effective approach to minimize wind-induced 

problems.
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6.4.3.2 Antenna (Communications Mast)

Antenna collapse is very common. Besides loss of communications, collapsed masts can puncture roof membranes or cause other building 

damage as shown in Figure 6-139. This case also demonstrates the benefits of a high parapet. Although the roof still experienced high winds 

that blew off this penthouse door, the parapet prevented the door from 

blowing off the roof (red arrow in Figure 6-139).

6.4.3.3 Lightning Protection Systems

Adhesively attached conductor connectors and pronged splice connectors typically have not provided reliable attachment during hurricanes. 

To provide more reliable attachment for LPSs located in hurricaneprone regions where the basic wind speed is 135 mph39 or greater, it 

is recommended that attachment modifications based on the guidance 

given in Section 6.3.4.4 be used. 

39 The 135-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If 

ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 100 mph. 

Figure 6-138: 

Two large openings (red 

rectangle and inset) 

through the roof were 

left after the ductwork 

blew away. Estimated 

wind speed: 130 mph. 

Hurricane Katrina 

(Mississippi, 2005)
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6.5 Occupant Protection Best Practices in 

Tornado- and Hurricane-Prone Regions 

Strong and violent tornadoes may reach wind speeds substantially greater than those recorded in the strongest hurricanes. 

The wind pressures that these tornadoes can exert on a building are tremendous, and far exceed the minimum pressures derived 

from building codes. The same can be said, but to a lesser extent for 

Category 4 and 5 hurricanes that may make landfall with wind speeds 

that exceed the basic (design) wind speed by 50 mph or more. 

Strong and violent tornadoes can generate very powerful missiles. 

Experience shows that large and heavy objects, including vehicles (see 

Figure 6-140), can be hurled into buildings at high speeds. The missile sticking out of the school roof in the foreground of Figure 6-141 is 

a double 2-inch by 6-inch wood member. The portion sticking out of 

the roof is 13 feet long. It penetrated a ballasted ethylene propylene 

diene monomer (EPDM) membrane, approximately 3 inches of polyisocyanurate 

roof insulation, and the steel roof deck. 

The missile lying on the roof just beyond 

is a 2-inch by 10-inch by 16-foot long wood 

member. 

Figure 6-139: 

The antenna collapsed 

and was whipped back 

and forth across the roof 

membrane. Hurricane 

Andrew (Florida, 1992)

Terrorist threat: If it is desired to incorporate a tornado safe room, and if it is also 

desired for the safe room to provide protection from terrorism, refer to FEMA 428 and 

453 for additional shelter enhancements.
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Figure 6-141: 

A violent tornado 

showered the roof with 

missiles (Oklahoma, 

1999)

Figure 6-140: 

Greensburg Tornado 

(Kansas, 2007)

For schools located in tornado-prone regions (as defined in the text box 

on the following page) and for schools that will be used for hurricane 

shelters, it is recommended that a safe room be incorporated within the 

school to provide occupant protection. For safe room design, see FEMA 

361. 

Note: The 2009 edition of the IBC references ICC 500 for the design and 

construction of hurricane and tornado shelters. However, while ICC 500 

specifies shelter criteria, it does not require shelters. ICC 500 is available 

to those who voluntarily desire to use it and to jurisdictions for adoption. 

FEMA 361 references much of the ICC 500 Standard. 
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Figure 6-142: Frequency of recorded EF3, EF4, and EF5 tornadoes (1950–2006)

In this manual, the term “tornado-prone regions” refers to those areas of the United States where the 

number of recorded EF3, EF4, and EF5 tornadoes per 2,470 square miles is 5 or greater per year (see 

Figure 6-141). However, a school district may decide to use other frequency values (e.g., 1 or greater, 

11 or greater, or greater than 15) in defining whether a school is in a tornado-prone area. In this manual, 

a tornado safe room is recommended for all schools in tornado-prone regions.

Where the frequency value is 1 or greater, and the school does not have a tornado safe room or shelter, 

the best available refuge areas should be identified, as discussed at the end of this Section.

Existing Schools without Tornado Shelters

Where the number of recorded EF3, EF4, and EF5 tornadoes per 2,470 

square miles is one or greater (see Figure 6-142), the best available refuge areas should be identified if the school does not have a tornado 

safe room. FEMA 431 provides useful information for building owners, 

architects, and engineers who perform evaluations of existing facilities.
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To minimize casualties in schools, it is very important that the best available refuge areas be identified 

by a qualified architect or engineer.40 Once identified, those areas need to be clearly marked so that 

occupants can reach the refuge areas without delay. 

Building occupants should not wait for the arrival 

of a tornado to try to find the best available refuge 

area in a particular facility; by that time, it will be too 

late. If refuge areas have not been identified beforehand, occupants will take cover wherever they can, 

frequently in very dangerous places. Corridors and 

other refuge areas sometimes provide protection, 

but they can also be death traps. The school shown 

in Figure 6-143 did not have a safe room. However, 

it did have a best available refuge area, which was 

occupied during a tornado. Unfortunately, collapsing occurred and eight students died.

Retrofitting a shelter space inside an existing school 

can be very expensive. An economical alternative 

is an addition that can function as a safe room as 

well as serve another purpose. This approach works 

well for many schools. For very large schools, constructing two or more safe room additions should 

be considered in order to reduce the time it takes 

to reach the safe room (often there is ample warning time, but sometimes an approaching tornado 

is not noticed until a few minutes before it strikes). 

40 The occupants of a “best available refuge area” are still vulnerable to death and injury if the 

refuge area was not specifically designed as a tornado safe room.

Hurricane safe room and evacuation 

shelters: In addition to providing criteria for 

the design and construction of tornado safe 

rooms, FEMA 361 provides criteria for hurricane safe rooms. Because of differences 

between wind and wind-borne debris loads 

induced by tornadoes versus hurricanes, 

and because of the time difference that the 

safe room is occupied during these storms, 

some of the hurricane safe room criteria are 

different. It is recommended that schools 

that will be used as hurricane evacuation 

shelters be designed and constructed 

in accordance with hurricane safe room 

guidance given in FEMA 361. In addition, 

see the recommendations in Section 6.3.5 

regarding electrical power, water, and sewer.

Publication 4496 by the American Red 

Cross (ARC, 2002) provides information regarding assessing existing buildings for use 

as hurricane evacuation shelters. Unless a 

school has been specifically designed for 

use as a shelter, it should only be used as 

a last resort and only if the school meets 

the criteria given in ARC 4496.

“Safe room” and “shelter” are two terms that have been used interchangeably in past publications, 

guidance documents, and other shelter-related materials. However, with the release of the ICC 500 

standard, there is a need to identify or describe shelters that meet the FEMA criteria that provide 

near-absolute life-safety protection and those that meet the ICC 500 standard (which is simply lifesafety protection). To help clarify the difference between shelters designed to the ICC 500 standard 

and the FEMA 361 guidance, FEMA 361 refers to all shelters constructed to meet the FEMA criteria 

as safe rooms. These two documents are quite similar and both utilize the same wind speed maps 

to define the tornado and hurricane hazards. Further, all safe room criteria in FEMA 361 meet the 

shelter requirements of the ICC 500. However, a few design and performance criteria in FEMA 361 

are more restrictive than some of the requirements found in the ICC 500.
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Figure 6-143 : 

Unreinforced masonry 

walls and hollow-core 

concrete roof planks 

collapsed. Enterprise 

Tornado (Alabama, 2007)

6.6 Checklist For Building Vulnerability of Schools 

Exposed to High Winds 

T he Building Vulnerability Assessment Checklist (Table 6-2) is a 

tool that can help in assessing the vulnerability of various building components during the preliminary design of a new building, 

or the rehabilitation of an existing building. In addition to examining 

design issues that affect vulnerability to high winds, the checklist also examines the potential adverse effects on the functionality of the critical 

and emergency systems upon which most schools depend. The checklist 

is organized into separate sections, so that each section can be assigned 

to a subject expert for greater accuracy of the examination. The results 

should be integrated into a master vulnerability assessment to guide the 

design process and the choice of appropriate mitigation measures.

Portable Classrooms: Portable classrooms should not be occupied during times when a tornado 

watch has been issued by the National Weather Service (a watch means that conditions are favorable 

for tornado development). Do not wait for issuance of a tornado warning (i.e., a tornado has been 

spotted) by the National Weather Service to seek refuge in the main school building. If a tornado is 

nearby, students could be caught outdoors.
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Table 6-2: Checklist for building vulnerability of schools exposed to high winds

Vulnerability Sections Guidance Observations

General

What is the age of the facility, and what 

building code and edition was used for 

the design of the building?

Substantial wind load improvements were 

made to the model building codes in the 1980s. 

Many buildings constructed prior to these 

improvements have structural vulnerabilities. 

Since the 1990s, several additional changes 

have been made, the majority of which pertain 

to the building envelope. 

Older buildings, not designed and constructed in 

accordance with the practices developed since 

the early 1990s, are generally more susceptible 

to damage than newer buildings.

Is the school older than 5 years, or is it 

located in a zone with basic wind speed 

greater than 120 mph?†

In either case, perform a vulnerability 

assessment with life-safety issues as the first 

priority, and property damage and interruption of 

service as the second priority.

Site

What is the design wind speed at the 

site? Are there topographic features that 

will result in wind speed-up?

ASCE 7 

What is the wind exposure on site? Avoid selecting sites in Exposure D, and avoid 

escarpments and hills.

Are there trees or towers on site? Avoid trees and towers near the facility. If the site 

is in a hurricane-prone region, avoid trees and 

towers near primary access roads.

Road access Provide two separate means of access.

Is the site in a hurricane-prone region? ASCE 7. If yes, follow hurricane-resistant design 

guidance.

If in a hurricane-prone region, are there 

aggregate-surfaced roofs within 1,500 

feet of the facility?

Remove aggregate from existing roofs. If the 

buildings with aggregate are owned by other 

parties, attempt to negotiate the removal of the 

aggregate. 

Architectural 

Will the facility be used as a shelter? If yes, refer to FEMA 361.

Are there interior non-load-bearing 

masonry walls?

Design for wind load. See Section 6.3.3.4.

Are there multiple buildings on site in a 

hurricane-prone region?

Provide enclosed walkways between buildings 

that will be occupied during a hurricane.

Structural Systems Section 6.3.2

Is a pre-engineered building being 

considered?

If yes, ensure the structure is not vulnerable 

to progressive collapse. If a pre-engineered 

building exists, evaluate to determine if it is 

vulnerable to progressive collapse.

† The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. If ASCE 7-05 or an earlier version is 

used, the equivalent wind speed trigger is 90 mph. 
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Table 6-2: Checklist for building vulnerability of schools exposed to high winds

Vulnerability Sections Guidance Observations

Structural Systems (cont.) Section 6.3.2

Is precast concrete being considered? If yes, design the connections to resist wind 

loads. If precast concrete elements exist, verify 

that the connections are adequate to resist the 

wind loads.

Are exterior load-bearing walls being 

considered?

If yes, design as MWFRS and C&C. 

Is an FM Global-rated roof assembly 

specified?

If yes, comply with FM Global deck criteria.

Is there a covered walkway or canopy? If yes, use “free roof” pressure coefficients 

from ASCE 7. Canopy decks and canopy 

framing members on older buildings often have 

inadequate wind resistance. Wind-borne debris 

from canopies can damage adjacent buildings 

and cause injury. 

Is the site in a hurricane-prone region? A reinforced cast-in-place concrete structural 

system, and reinforced concrete or fully grouted 

and reinforced CMU walls, is recommended.

Is the site in a tornado-prone region? If yes, provide occupant protection. See FEMA 

361. For existing schools that do not have safe 

rooms, see FEMA 431. 

Do portions of the existing facility 

have long-span roof structures (e.g., a 

gymnasium)?

Evaluate structural strength, since older 

long-span structures often have limited uplift 

resistance.

Is there adequate uplift resistance of 

the existing roof deck and deck support 

structure?

The 1979 (and earlier) SBC and UBC, and 1984 

(and earlier) BOCA/NBC, did not prescribe 

increased wind loads at roof perimeters and 

corners. Decks (except cast-in-place concrete) 

and deck support structures designed in 

accordance with these older codes are quite 

vulnerable. The strengthening of the deck 

attachment and deck support structure is 

recommended for older buildings. 

Are there existing roof overhangs that 

cantilever more than 2 feet?

Overhangs on older buildings often have 

inadequate uplift resistance.

Building Envelope Section 6.3.3

Exterior doors, walls, roof systems, 

windows, and skylights.

Select materials and systems, and detail, to 

resist wind and wind-driven rain.

Are soffits considered for the building? Design to resist wind and wind-driven water 

infiltration. If there are existing soffits, evaluate 

their wind and wind-driven rain resistance. If 

the soffit is the only element preventing winddriven rain from being blown into an attic space, 

consider strengthening the soffit.

Are there elevator penthouses on the roof? Design to prevent water infiltration at walls, roof, 

and mechanical penetrations.

Is a low-slope roof considered on a site in 

a hurricane-prone region?

A minimum 3-foot parapet is recommended on 

low-slope roofs.
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Table 6-2: Checklist for building vulnerability of schools exposed to high winds

Vulnerability Sections Guidance Observations

Building Envelope (cont.) Section 6.3.3

Are there existing sectional or rolling 

doors?

Older doors often lack sufficient wind resistance. 

Does the existing building have large 

windows or curtain walls?

If an older building, evaluate their wind 

resistance.

Does the existing building have exterior 

glazing (windows, glazed doors, or 

skylights)?

If the building is in a hurricane-prone region, 

replace with impact-resistant glazing, or protect 

with shutters.

Does the existing building have operable 

windows?

If an older building, evaluate its wind-driven rain 

resistance via ASTM E 1105.

Are there existing exterior non-loadbearing masonry walls?If the building is in a hurricane- or tornado-prone 

region, strengthen or replace.

Are there existing brick veneer, EIFS, or 

stucco exterior coverings?

If the building is in a hurricane-prone region, 

evaluate attachments. To evaluate wind 

resistance of EIFS, see ASTM E 2359.

Are existing exterior walls resistant to 

wind-borne debris?

If the building will be used as a hurricane 

evacuation shelter, but was not designed and 

constructed in accordance with FEMA 361, 

consider enhancing debris resistance.

Does the existing roof have a fully 

adhered membrane?

To evaluate uplift resistance, see ASTM E 907.

Are there existing ballasted single-ply 

roof membranes?

Determine if they are in compliance with ANSI/

SPRI RP-4. If non-compliant, take corrective 

action.

Does the existing roof have aggregate 

surfacing, lightweight pavers, or 

cementitious-coated insulation boards?

If the building is in a hurricane-prone region, 

replace the roof covering to avoid blow-off.

Does the existing roof have edge 

flashing, coping, or gutters?

Evaluate the adequacy of the attachment. 

Does the existing roof system incorporate 

a secondary membrane?

If not, and if the building is in a hurricane-prone 

region, reroof and incorporate a secondary 

membrane into the new system. 

Does the existing building have a brittle 

roof covering, such as slate or tile?

If the building is in a hurricane-prone region, 

consider replacing with a non-brittle covering, 

particularly if the building will be used as a 

hurricane evacuation shelter.

Exterior-Mounted Mechanical Equipment Section 6.3.4.1

Is there mechanical equipment mounted 

outside at grade or on the roof?

Anchor the equipment to resist wind loads. 

If there is existing equipment, evaluate 

the adequacy of the attachment, including 

attachment of cowlings, access panels, ducts, 

and gas lines.

Are there penetrations through the roof? Design intakes and exhausts to avoid water 

leakage.

Is the site in a hurricane-prone region? If yes, place the equipment in a penthouse, 

rather than exposed on the roof.
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Table 6-2: Checklist for building vulnerability of schools exposed to high winds

Vulnerability Sections Guidance Observations

Exterior-Mounted Electrical and Communications Equipment Section 6.3.4.3 

Are there antennae (communication 

masts) or satellite dishes?

If there are existing antennae or satellite dishes 

and the building is located in a hurricane-prone 

region, evaluate wind resistance. For antennae 

evaluation, see Chapter 15 of ANSI/TIA-222-G.

Does the building have an LPS? See Sections 6.3.4.3 and 6.3.4.4 for LPS 

attachment. For existing LPSs, evaluate wind 

resistance (Section 6.4.3.3)

Municipal Utilities

Will the facility be used as a hurricane 

evacuation shelter?

See Section 6.3.5 for emergency power, water, 

and sewer recommendations.

Is the emergency generator housed in a 

wind- and debris-resistant enclosure?

If not, build an enclosure to provide debris 

protection.

Is the emergency generator’s wall louver 

protected from wind-borne debris?

If not, install a louver or screen wall to provide 

debris impact protection.

6.7 References and Sources of Additional 

Information 

Note: FEMA publications may be obtained at no cost by calling (800) 

480-2520, or by downloading from the library/publications section online at http://www.fema.gov. 

American Association of State Highway and Transportation Officials 

(AASHTO), 2009. Standard Specifications for Structural Supports for Highway 

Signs, Luminaires and Traffic Signals, LTS-4-5.

American Institute of Architects (AIA), 1997. Buildings at Risk:  Wind 

Design Basics for Practicing Architects. 

American National Standards Institute (ANSI), 2003. Wind Design 

Standard for Edge Systems Used in Low Slope Roofing Systems, ANSI/SPRI 

ES-1. 

ANSI, 2008. Wind Design Standard for Ballasted Single-Ply Roofing Systems, 

ANSI/SPRI RP-4.

ANSI/Telecommunications Industry Association (TIA), 2009. Structural 

Standard for Antenna Supporting Structures and Antennas, ANSI/TIA222-G, Addendum 2, December 2009.
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American Red Cross (ARC), 2002. Standards for Hurricane Evacuation 

Shelter Selection, Publication 4496, July 1992, rev. January 2002. 

American Society of Civil Engineers (ASCE), 2005. Minimum Design Loads 

for Buildings and Other Structures, ASCE 7-05, Structural Engineering 

Institute, Reston, VA.

ASCE, 2010. Minimum Design Loads for Buildings and Other Structures, 

2010 Edition, ASCE 7-10, Structural Engineering Institute, Reston, VA.

American Society for Testing and Materials (ASTM), 2004. Standard 

Test Method for Field Testing Uplift Resistance of Adhered Membrane Roofing 

Systems, ASTM E 907-96.

ASTM, 2005a. Standard Test Method for Performance of Exterior Windows, 

Curtain Walls, Doors, and Impact Protective Systems Impacted by Missile(s) and 

Exposed to Cyclic Pressure Differentials, ASTM E 1886. 

ASTM, 2005b. Standard Test Method for Structural Performance of Sheet Metal 

Roof and Siding Systems by Uniform Static Air Pressure Difference, ASTM E 1592. 

ASTM, 2006a. Standard Test Method for Structural Performance of Exterior 

Windows, Curtain Walls, and Doors by Cyclic Static Air Pressure Differential, 

ASTM E 1233.

ASTM, 2006b. Test Method for Field Pull Testing of an In-Place Exterior 

Insulation and Finish System Clad Wall Assembly, ASTM E 2359. 

ASTM, 2007. Standard Practice for Installation of Exterior Windows, Doors 

and Skylights, ASTM E 2112.

ASTM, 2008. Standard Test Method for Field Determination of Water Penetration 

of Installed Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform 

or Cyclic Static Air Pressure Difference, ASTM E 1105-00.

ASTM, 2009a. Standard Specification for Performance of Exterior Windows, 

Curtain Walls, Doors and Impact Protective Systems Impacted by Windborne 

Debris in Hurricanes, ASTM E 1996.

American Society of Heating, Refrigerating and Air Conditioning 

Engineers (ASHRAE), 2006. Calculating Wind Loads and Anchorage 

Requirements for Rooftop Equipment.

ASHRAE, 2007a. Standard 62.1 User’s Manual.

ASHRAE, 2007b. Ventilation for Acceptable Indoor Air Quality, Standard 

62.1.
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Baskaran, B, and T.L. Smith, 2005. A Guide for the Wind Design of 

Mechanically Attached Flexible Membrane Roofs, Institute for Research in 

Construction, National Research Council of Canada. 

Door and Access Systems Manufacturers Association, 2008. Connecting 

Garage Door Jambs to Building Framing, Technical Data Sheet #161, 

December 2003, revised May 2008.

Edwards, Roger, 2009. The Online Tornado FAQ, Storm Prediction 

Center, NOAA. www.spc.noaa.gov/faq/tornado/#History, last modified 

December 31, 2009.

Factory Mutual Research, Approval Guide, Norwood, MA, updated 

quarterly. 

Federal Emergency Management Agency (FEMA), 1992. Building 

Performance: Hurricane Andrew in Florida, FEMA FIA-22, Washington, DC, 

December 1992.

FEMA, 1993. Building Performance: Hurricane Iniki in Hawaii, FEMA FIA23, Washington, DC, January 1993.

FEMA, 1996. Corrosion Protection for Metal Connectors in Coastal Areas, 

FEMA Technical Bulletin 8-96, Washington, DC, August 1996. 

FEMA, 1998. Typhoon Paka: Observations and Recommendations on Building 

Performance and Electrical Power Distribution System, FEMA-1193-DR-GU, 

Washington, DC, March 1998.

FEMA, 1999a. Hurricane Georges in Puerto Rico, FEMA 339, Washington, 

DC, March 1999.

FEMA, 1999b. Oklahoma and Kansas Midwest Tornadoes of May 3, 1999, 

FEMA 342, Washington, DC, October 1999.

FEMA, 2000. Coastal Construction Manual, FEMA 55, CD (3rd Edition).

FEMA, 2002. Installing Seismic Restraints for Mechanical Equipment, FEMA 

412, Washington, DC, December 2002. 

FEMA, 2003a. Primer to Design Safe School Projects in Case of Terrorist Attacks, 

FEMA 428, December 2003.

FEMA, 2003b. Tornado Protection, Selecting Safe Areas in Buildings, FEMA 

431, Washington, DC, October 2003. 
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FEMA, 2004a. Installing Seismic Restraints for Duct and Pipe, FEMA 414, 

Washington, DC, January 2004. 

FEMA, 2004b. Installing Seismic Restraints for Electrical Equipment, FEMA 

413, Washington, DC, January 2004. 

FEMA, 2005a. MAT Report:  Hurricane Charley in Florida, FEMA 488, 

Washington, DC, April 2005.

FEMA, 2005b. MAT Report: Hurricane Ivan in Alabama and Florida, FEMA 

489, Washington, DC, August 2005.

FEMA, 2006a. Design Guidance for Shelters and Safe Rooms, FEMA 453, 

Washington, DC.

FEMA, 2006b. MAT Report:  Hurricane Katrina in the Gulf Coast, FEMA 

549, Washington, DC, July 2006. 

FEMA, 2007. Design Guide for Improving Critical Facility Safety from Flooding 

and High Winds, FEMA 543, Washington, DC, January 2007.

FEMA, 2008a. Design and Construction Guidance for Community Safe Rooms, 

FEMA 361, Washington, DC, November 2008. 

FEMA, 2008b. Taking Shelter From the Storm: Building a Safe Room Inside 

Your House, FEMA 320, Washington, DC, August 2008. 

FEMA, 2009. MAT Report:  Hurricane Ike in Texas and Louisiana, FEMA 

P-757, Washington, DC, April 2009. 

FEMA, 2010. Home Builder’s Guide to Coastal Construction Technical Fact 

Sheet Series, FEMA P-499, December 2010.

FM Global, dates vary. Loss Prevention Data for Roofing Contractors, 

Norwood, MA. 

Institute of Electrical and Electronics Engineers, Inc. (IEEE), 2008. 

National Electrical Code, NFPA 70.

International Code Council (ICC), 2008. ICC/NSSA Standard on the Design 

and Construction of Storm Shelters, ICC 500-2008, Country Club Hills, IL.

ICC, 2009. 2006 International Building Code, ICC IBC-2009, February 

2009. 

National Research Council of Canada, 2005. Wind Design Guide for 

Mechanically Attached Flexible Membrane Roofs, B1049. 
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6.8 Glossary of High Wind Protection Terms

Astragal. The center member of a double door, which is attached to the 

fixed or inactive door panel.

Basic wind speed. A 3-second gust speed at 33 feet above the ground in 

Exposure C. (Exposure C is flat open terrain with scattered obstructions 

having heights generally less than 30 feet.) Note: Since 1995, ASCE 7 

has used a 3-second peak gust measuring time. A 3-second peak gust 

is the maximum instantaneous speed with a duration of approximately 

3 seconds. A 3-second peak gust speed could be associated with a given windstorm (e.g., a particular storm could have a 40-mph peak gust 

speed), or a 3-second peak gust speed could be associated with a design 

level event (e.g., the basic wind speed prescribed in ASCE 7).

Building, enclosed. A building that does not comply with the requirements for open or partially enclosed buildings.

Building, open. A building having each wall at least 80 percent open. This 

condition is expressed by an equation in ASCE 7.

Building, partially enclosed. A building that complies with both of the 

following conditions:

1. The total area of openings in a wall that receives positive external 

pressure exceeds the sum of the areas of openings in the balance of the building envelope (walls and roof) by more than 10 

percent.

2. The total area of openings in a wall that receives positive external 

pressure exceeds 4 square feet, or 1 percent of the area of that 

wall, whichever is smaller, and the percentage of openings in the 

balance of the building envelope does not exceed 20 percent. 

These conditions are expressed by equations in ASCE 7.

Building, simple diaphragm. An enclosed or partially enclosed building in 

which wind loads are transmitted through floor and roof diaphragms to 

the vertical main wind-force resisting system.

Components and cladding (C&C). Elements of the building envelope that 

do not qualify as part of the main wind-force resisting system.

Coping. The cover piece on top of a wall exposed to the weather, usually 

made of metal, masonry, or stone, and sloped to carry off water.
6-148 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

6 MAKING SCHOOLS SAFE FROM HIGH WINDS

Downburst. Also known as a microburst. A powerful downdraft associated with a thunderstorm. 

Down-slope wind. A wind blowing down the slope of mountains (frequently occurs in Alaska and Colorado).

Escarpment. Also known as a scarp. With respect to topographic effects, a 

cliff or steep slope generally separating two levels or gently sloping areas. 

Exposure. The characteristics of the ground roughness and surface irregularities in the vicinity of a building. ASCE 7 defines three exposure 

categories—Exposures B, C, and D. 

Extratropical storm. A cyclonic storm that forms outside of the tropical 

zone. Extratropical storms may be large, often 1,500 miles (2,400 kilometers) in diameter, and usually contain a cold front that extends toward 

the equator for hundreds of miles.

Flashing. Any piece of material, usually metal or plastic, installed to prevent water from penetrating a structure.

Glazing. Glass or a transparent or translucent plastic sheet used in windows, doors, and skylights.

Glazing, impact-resistant. Glazing that has been shown, by an approved 

test method, to withstand the impact of wind-borne missiles likely to be 

generated in wind-borne debris regions during design winds.

Hurricane-prone regions. Areas vulnerable to hurricanes; in the United 

States and its territories defined as:

1. The U.S. Atlantic Ocean and Gulf of Mexico coasts, where the 

basic wind speed is greater than 120 miles per hour.41

2. Hawaii, Puerto Rico, Guam, U.S. Virgin Islands, and American 

Samoa.

Impact-resistant covering. A covering designed to protect glazing, which 

has been shown by an approved test method to withstand the impact of 

wind-borne missiles likely to be generated in wind-borne debris regions 

during design winds.

Importance factor, I. A factor that accounts for the degree of hazard to 

human life and damage to property. Importance factors are given in 

41 The 120-mph basic wind speed is based on ASCE 7-10, Risk Category III and IV buildings. 

If ASCE 7-05 or an earlier version is used, the equivalent wind speed trigger is 90 mph. 
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS 6-149

MAKING SCHOOLS SAFE FROM HIGH WINDS 6

ASCE 7. Note: In ASCE 7-10, the importance factor was eliminated for 

wind loads because the degree of hazard to human life and property 

damage is accounted for by the proper map selection.

Main wind-force resisting system. An assemblage of structural elements 

assigned to provide sup-port and stability for the overall structure. The 

system generally receives wind loading from more than one surface.

Mean roof height, h. The average of the roof eave height and the height 

to the highest point on the roof surface, except that, for roof angles of 

less than or equal to 10 degrees, the mean roof height shall be the roof 

eave height.

Missiles. Debris that could become propelled into the wind stream. 

Nor’easter. Nor’easters are non-tropical storms that typically occur in 

the eastern United States, any time between October and April, when 

moisture and cold air are plentiful. They are known for dumping heavy 

amounts of rain and snow, producing hurricane-force winds, and creating high surfs that cause severe beach erosion and coastal flooding. A 

nor’easter is named for the winds that blow in from the northeast and 

drive the storm along the east coast and the Gulf Stream, a band of warm 

water that lies off the Atlantic Coast. 

Openings. Apertures or holes in the building envelope that allow air to 

flow through the building envelope. A door that is intended to be in the 

closed position during a windstorm would not be considered an opening. 

Glazed openings are also not typically considered openings. However, if 

the building is located in a wind-borne debris region and the glazing is 

not impact-resistant or protected with an impact-resistant covering, the 

glazing is considered an opening.

Racking. Lateral deflection of a structure resulting from external forces, 

such as wind or lateral ground movement in an earthquake.

Ridge. With respect to topographic effects, an elongated crest of a hill 

characterized by strong relief in two directions.

Straight-line wind. A wind blowing in a straight line with wind speeds 

ranging from very low to very high (the most common wind occurring 

throughout United States and its territories). 

Wind-borne debris regions. Areas within hurricane-prone regions, as defined in ASCE 7. 

DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS A-1

AAcronyms

AASHTO  American Association of State Highway and 

Transportation Officials

ADA  Americans with Disabilities Act

ARC  American Red Cross

ASCE  American Society of Civil Engineers

ASFPM  Association of State Floodplain Managers

ASHRAE  American Society of Heating, Refrigerating and Air 

Conditioning Engineers

ASTM  American Society for Testing and Materials

ATC  Applied Technology Council

BFE  Base flood elevation

BOCA  Building Officials and Code Administrators 

International, Inc.

BSSC  Building Seismic Safety Council

BUR  Built-up roof

CBR  Chemical, biological, or radiological

C&C  Components and cladding

CFR  Code of Federal Regulations

CMU  Concrete Masonry Unit
A-2 DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS

A ACRONYMS

CSSC  California Seismic Safety Commission

DFE  Design flood elevation

EIFS  Exterior insulation finish system

ELF  Equivalent Lateral Force

EPDM  Ethylene propylene diene monomer

FEMA  Federal Emergency Management Agency

FIRM  Flood Insurance Rate Map

FIS  Flood Insurance Study

FMG  FM Global

FMR  Factory Mutual Research

GIS  Geographic Information System

HazMat  Hazardous Materials

HAZUS-MH  Hazards U.S. Multi-Hazards

HVAC  Heating, ventilation, and air conditioning

IBC  International Building Code

ICBO  International Conference of Building Officials

ICC  International Code Council

ICC PC  International Code Council Performance Code

IT  Information Technology

LCD  Liquid crystal display

LiMWA  Limit of Moderate Wave Action

LPS  Lightning protection system

M/E/P  Mechanical/Electrical/Plumbing

MEPS  Molded expanded polystyrene

MMI  Modified Mercalli Intensity

MWFRS  Main wind-force resisting system

NBC  National Building Code 

NEHRP  National Earthquake Hazards Reduction Program

NFPA  National Fire Protection Association

NFIP  National Flood Insurance Program
DESIGN GUIDE FOR IMPROVING SCHOOL SAFETY IN EARTHQUAKES, FLOODS, AND HIGH WINDS A-3

AN OVERVIEW OF THE SCHOOL DESIGN AND CONSTRUCTION PROCESS ACRONYMS A1

NIBS  National Institute of Building Sciences

O&M  Operations and Maintenance

OSB  Oriented strand board

PMR  Protected membrane roof

RC  Reinforced concrete

RSP  Rapid Screening Procedure

SBC  Standard Building Code

SBCCI  Southern Building Code Congress International, Inc.

SDC  Seismic Design Category

SEI  Structural Engineering Institute

SFHA  Special flood hazard area

SPF  Sprayed polyurethane foam

SPRI  Single Ply Roofing Industry

TAS  Testing Application Standard

TIA  Telecommunications Industry Association

UBC  Uniform Building Code

UL  Underwriters Laboratories

URM  Unreinforced mansonry

USACE  U.S. Army Corps of Engineers

U.S.C.  U.S. Code

USGS  U.S. Geological Survey


FEMA P-424

Catalog No: XXXXX-X