Homeowner’s Guide

to Retrofitting

Six Ways to Protect Your Home From Flooding

FEMA P-312, 3rd Edition / June 2014

Homeowner’s Guide

to Retrofitting

Six Ways to Protect Your Home From Flooding

FEMA P-312, 3rd Edition / June 2014

HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING i

Preface

The Federal Emergency Management Agency (FEMA) has prepared this guide specifically for homeowners who 

want to know how to help protect their homes from flooding. As a homeowner, you need clear information about 

the options available to you and straightforward guidance that will help you make decisions. This guide gives you 

both, in a form designed for readers who have little or no experience with flood protection methods or building 

construction techniques.

HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING iii

Acknowledgments

Third Edition Authors and Key Contributors

Seth Frost-Tift, URS Group, Inc.

Amit Mahadevia, URS Group, Inc.

Deborah Mills, Dewberry

Adam Reeder, Atkins

Adrienne Sheldon, URS Group, Inc.

John Squerciati, Dewberry

Third Edition Reviewers and Contributors

Daniel Bass, FEMA Headquarters

William Coulbourne, URS Group, Inc.

Franki Coons, FEMA Headquarters

Jhun de la Cruz, FEMA Headquarters

John Grace, FEMA Region I

Karolyn Kiss, FEMA Headquarters 

John Ingargiola, FEMA Headquarters

John “Bud” Plisich, FEMA Region IV

Steven VanDyke, FEMA Headquarters

Gregory Wilson, FEMA Headquarters

Wallace Wilson, URS Group, Inc.

Third Edition Technical Editing, Layout, and Illustration

Young Cho, URS Group, Inc.

Julie Liptak, Stantec

Lee-Ann Lyons, URS Group, Inc.

Susan Patton, URS Group, Inc.

Ivy Porpotage, URS Group, Inc.

Billy Ruppert, URS Group, Inc.

Amy Siegel, URS Group, Inc.

HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING v

Table of Contents

Preface.................................................................................................................................................. i

Acknowledgments.............................................................................................................................. iii

Acronyms......................................................................................................................................... xiii

1.0 About this Guide .....................................................................................................................1-1

1.1 Who This Guide Is For.....................................................................................................................1-1

1.2 How This Guide Can Help You.........................................................................................................1-2

1.3 How To Use This Guide ...................................................................................................................1-2

2.0 Introduction to Retrofitting .....................................................................................................2-1

2.1 What Is Retrofitting? .......................................................................................................................2-3

2.2 Types of Flooding............................................................................................................................2-3

2.3 How Flooding Can Damage Your Home ..........................................................................................2-5

2.3.1 Depth/Elevation of Flooding..............................................................................................2-5

2.3.2 Flow Velocity......................................................................................................................2-8

2.3.3 Flood Frequency ................................................................................................................2-9

2.3.4 Rates of Rise and Fall........................................................................................................2-10

2.3.5 Duration...........................................................................................................................2-11

2.3.6 Debris Impact...................................................................................................................2-11

2.4 Other Hazards ...............................................................................................................................2-11

2.5 Federal, State, and Local Regulations .............................................................................................2-12

2.5.1 The Community Rating System........................................................................................2-13

2.5.2 Flood Insurance Rate Maps...............................................................................................2-14

2.6 Financial Assistance for Retrofitting...............................................................................................2-16

2.6.1 Federal Programs..............................................................................................................2-16

2.6.2 Non-Federal Help ............................................................................................................2-20
vi SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

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3.0 An Overview of the Retrofitting Methods................................................................................3-1

3.1 Cautions ..........................................................................................................................................3-2

3.1.1 Substantial Improvement / Substantial Damage .................................................................3-2

3.1.2 Basements ..........................................................................................................................3-3

3.1.3 Flood Protection Elevation and Risk ...................................................................................3-3

3.1.4 Freeboard and Flood Mapping Uncertainties .....................................................................3-6

3.1.5 Human Intervention ..........................................................................................................3-8

3.1.6 Other Considerations.........................................................................................................3-9

3.2 Construction Terminology.............................................................................................................3-10

3.2.1 Construction Type ............................................................................................................3-10

3.2.2 Foundation Type...............................................................................................................3-11

3.3 Retrofitting Methods and Costs .....................................................................................................3-12

3.3.1 Elevation ..........................................................................................................................3-12

3.3.2 Relocation and Demolition ..............................................................................................3-20

3.4 Floodproofing ...............................................................................................................................3-25

3.4.1 Wet Floodproofing...........................................................................................................3-25

3.4.2 Dry Floodproofing ...........................................................................................................3-28

3.4.3 Barrier Systems ................................................................................................................3-31

3.5 Summary.......................................................................................................................................3-36

4.0 Deciding Which Method Is Right for Your Home.....................................................................4-1

4.1 Making Your Decision......................................................................................................................4-2

4.1.1 Step 1 – Determine the Hazards to Your Home ..................................................................4-2

4.1.2 Step 2 – Inspect Your Home ...............................................................................................4-3

4.1.3 Step 3 – Check with Your Local Officials..........................................................................4-11

4.1.4 Step 4 – Consult a Design Professional and Retrofitting Contractor................................4-12

4.2 Decision-Making Matrices.............................................................................................................4-15

4.2.1 Evaluation Factors ............................................................................................................4-15

4.2.2 Substantial Improvement / Substantial Damage Matrix....................................................4-17

4.2.3 NOT Substantial Improvement / NOT Substantial Damage Matrix ..................................4-18

5.0 Elevating Your Home................................................................................................................5-1

5.1 Considerations.................................................................................................................................5-2

5.1.1 Amount of Elevation ..........................................................................................................5-2

5.1.2 Existing Foundation ...........................................................................................................5-4

5.1.3 Hazards..............................................................................................................................5-5

5.1.4 Access ................................................................................................................................5-5

5.1.5 Home Size, Design, and Shape ...........................................................................................5-6

5.1.6 Service Equipment .............................................................................................................5-6
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING vii

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5.2 The Elevation Techniques.................................................................................................................5-6

5.2.1 Elevating on Extended Foundation Walls............................................................................5-6

5.2.2 Alternative Elevation Techniques for Masonry Homes on Slab-on-Grade Foundations.....5-15

5.2.3 Elevating on an Open Foundation....................................................................................5-20

6.0 Relocation and Demolition ......................................................................................................6-1

6.1 Relocation .......................................................................................................................................6-1

6.1.1 Considerations ...................................................................................................................6-2

6.1.2 The Relocation Process.......................................................................................................6-3

6.2 Demolition ......................................................................................................................................6-9

6.2.1 Considerations .................................................................................................................6-10

6.2.2 The Demolition Process ...................................................................................................6-11

7.0 Floodproofing..........................................................................................................................7-1

7.1 Wet Floodproofing ..........................................................................................................................7-1

7.1.1 Design Flood Elevation.......................................................................................................7-2

7.1.2 Hazards..............................................................................................................................7-2

7.1.3 Post-Flood Cleanup ............................................................................................................7-3

7.1.4 Modifications Required for Wet Floodproofing..................................................................7-5

7.1.5 Installing Openings............................................................................................................7-5

7.1.6 Protecting the Underside of Elevated Buildings..................................................................7-7

7.1.7 Using Flood Damage-Resistant Materials ...........................................................................7-8

7.1.8 Protecting Service Equipment ............................................................................................7-9

7.2 Dry Floodproofing...........................................................................................................................7-9

7.2.1 Considerations .................................................................................................................7-10

7.2.2 Modifications Required for Dry Floodproofing................................................................7-12

8.0 Barriers....................................................................................................................................8-1

8.1 Levees..............................................................................................................................................8-2

8.2 Floodwalls.......................................................................................................................................8-3

8.3 Temporary Barriers..........................................................................................................................8-3

8.4 Technical Considerations.................................................................................................................8-4

8.4.1 Height of Barrier................................................................................................................8-4

8.4.2 Basement Foundations .......................................................................................................8-5

8.4.3 Soil Conditions...................................................................................................................8-5

8.4.4 Duration of Flooding .........................................................................................................8-5

8.5 Additional Considerations ...............................................................................................................8-6

8.5.1 Annual Maintenance ..........................................................................................................8-6

8.5.2 Housing of Occupants .......................................................................................................8-6

8.5.3 Access to Structure .............................................................................................................8-6
viii SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

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8.5.4 Human Intervention ..........................................................................................................8-6

8.5.5 Interior Drainage................................................................................................................8-7

9.0 Protecting Service Equipment ..................................................................................................9-1

9.1 Elevation..........................................................................................................................................9-2

9.1.1 Maintaining Horizontal and Vertical Clearances .................................................................9-4

9.1.2 Venting Considerations ......................................................................................................9-5

9.1.3 Unions, Fittings, and Valves................................................................................................9-5

9.2 Relocation .......................................................................................................................................9-5

9.2.1 Electrical Panels..................................................................................................................9-5

9.2.2 Electric Meters....................................................................................................................9-6

9.2.3 Electrical Wiring.................................................................................................................9-6

9.2.4 Mechanical Systems ...........................................................................................................9-6

9.2.5 Water Heaters.....................................................................................................................9-7

9.2.6 Washer/Dryer Units...........................................................................................................9-7

9.3 Protection in Place...........................................................................................................................9-7

9.3.1 Floodwalls and Shields.......................................................................................................9-8

9.3.2 Anchors and Tiedowns.......................................................................................................9-8

9.3.3 Backflow Valves ................................................................................................................9-10

Appendices

Appendix A Bibliography and Sources of Information

Appendix B Glossary

Appendix C FEMA Regional Offices

Appendix D NFIP State Coordinating Agencies

Appendix E State Historic Preservation Offices

Appendix F Professional Organizations

Appendix G Retrofitting Checklist

Figures 

Figure 2-1. This home in New Orleans was inundated by 4 feet of water during Hurricane Katrina.............2-1

Figure 2-2. This home, from Figure 2-1, was elevated in a manner that added to both its appearance and 

its value. As a result of its elevation, the home avoided major damage from Hurricane Isaac 

in 2012. .......................................................................................................................................2-2

Figure 2-3. These homes in Gays Mills, WI, were inundated by riverine flooding during the Midwest 

floods of 2008..............................................................................................................................2-4

Figure 2-4. The extreme impact of large, fast-moving waves, combined with the removal of supporting soil 

by erosion and scour, can have devastating effects on buildings exposed to coastal flooding. 

Hurricane Floyd destroyed this home along the coast of North Carolina in 1999. ......................2-4
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING ix

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Figure 2-5. In this example, the 1-percent-annual-chance flood elevation is 391.6 feet (10.1 feet above the 

benchmark elevation of 381.5 feet), and the elevation of the lowest floor of the home is 389.3 

feet (7.8 feet above the same benchmark). The flood depth above the lowest floor is therefore 

equal to 391.6 feet − 389.3 feet, or 2.3 feet during the 1-percent-annual-chance flood.............2-6

Figure 2-6. Hydrostatic pressure acts on walls and concrete slab floors. The weight of saturated soils adds 

to the pressure on basement walls. Figure 2-6a shows a home with a concrete slab floor. Figure 

2-6b shows a home with a basement...........................................................................................2-7

Figure 2-7. The walls of this basement in Wisconsin failed because of the pressure exerted by water and 

saturated soil. ...............................................................................................................................2-7

Figure 2-8. Once water enters the home, hydrostatic pressure is equalized. Figure 2-8a shows a home 

with a concrete slab floor. Figure 2-8b shows a home with a basement.......................................2-8

Figure 2-9. Moving water acts on the front, sides, and back of a home..........................................................2-9

Figure 2-10. Water moving at high velocity destroyed the wall of this home and caused the building to 

shift on its foundation..................................................................................................................2-9

Figure 2-11. Wind forces on a sealed building are less than wind forces on a building with an opening. .....2-12

Figure 2-12. Earthquake forces act in both horizontal and vertical directions.................................................2-12

Figure 2-13. This FIRM for riverine flooding shows the SFHA (Zone AE), floodway (hatch-marked Zone AE 

along centerline of river channel), and areas outside the SFHA (Zone X). The area between the 

limits of the base flood and 0.2-percent-annual-chance flood are delineated by shaded Zone X. 

Areas above the 0.2-percent-annual-chance flood are delineated by unshaded Zone X..............2-15

Figure 3-1. This graph shows the relationship between flood recurrence intervals and the probability of an 

event occurring within a 30-year period......................................................................................3-6

Figure 3-2. Portion of a paper FIRM showing coastal flood insurance rate zones. The icons on the right 

indicate the associated flood hazard zones for design and construction purposes. The LiMWA 

is not shown on older FIRMs, but is shown on newer FIRMs.......................................................3-7

Figure 3-3. Typical transect perpendicular to the shoreline showing the delineations between Zone V, the 

MoWA area, the LiMWA, Zone A, and the MiWA area..................................................................3-8

Figure 3-4. Ty pical cross-sections of three common construction types: frame, masonry veneer, and 

masonry. The foundation shown here for all three construction types consists of concrete 

blocks and a concrete footing. The same construction types are also found on basement and 

slab-on-grade foundations..........................................................................................................3-11

Figure 3-5. Home foundation types..............................................................................................................3-12

Figure 3-6. Typical cross-section of home elevated on continuous foundation walls....................................3-14

Figure 3-7. Before (left) and after (right) photos of a retrofitted home elevated on extended continuous 

foundation walls.........................................................................................................................3-14

Figure 3-8. Home elevated on reinforced concrete piers. .............................................................................3-15

Figure 3-9. Home elevated on posts .............................................................................................................3-16

Figure 3-10. Home elevated on piles. .............................................................................................................3-17
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Figure 3-11. Example of well-elevated and embedded pile foundation tested by Hurricane Katrina. 

Note adjacent building failures (Dauphin Island, AL, 2005). .....................................................3-17

Figure 3-12. The owner of this flood-prone home in south Florida decided to build a new wood-framed 

second story on top of the masonry first story. The new second story is well above the BFE......3-18

Figure 3-13. Many homes in the Town of Prattsville, NY, were slated for demolition during the recovery 

effort following Hurricane Irene................................................................................................3-23

Figure 3-14. A home with a wet floodproofed subgrade basement................................................................3-26

Figure 3-15. A home with a wet floodproofed enclosure. ..............................................................................3-27

Figure 3-16. A typical dry floodproofed home...............................................................................................3-30

Figure 3-17. A home protected by a levee (left) and a floodwall (right)........................................................3-33

Figure 3-18. A home protected by a levee. .....................................................................................................3-33

Figure 3-19. A home protected by a floodwall designed as a landscaping feature...........................................3-36

Figure 3-20. Example of floodwall and levee dimensions...............................................................................3-37

Figure 4-1. Peak gust wind speeds in the United States. Source: Minimum Design Loads for Buildings 

and Other Structures, ASCE/SEI 7-10. Used with permission from ASCE.....................................4-4

Figure 4-2. Seismic Design Categories Map of the United States for low-rise Occupancy Category I and II 

structures located on sites with average alluvial soil conditions....................................................4-6

Figure 4-3. Difference between flood level and lowest floor in homes on crawlspace and basement 

foundations. ...............................................................................................................................4-10

Figure 5-1. As shown in the cutaway view, the lowest floor is above the flood level. When at least 1 foot 

of freeboard is provided, only the foundation is exposed to flooding. .........................................5-3

Figure 5-2. This home in Cedar Falls, IA, was elevated one full story. The garage and storage area are at the 

home’s original elevation. ............................................................................................................5-4

Figure 5-3. With attention to detail and planning, homeowners have created attractive retrofitted homes.....5-5

Figure 5-4a through 5-4d. Elevating a basement or crawlspace foundation home on extended foundation 

walls.............................................................................................................................................5-8

Figure 5-5. Cross-section view of slab-on-grade foundation variations........................................................5-10

Figure 5-6. Building a new foundation for a slab-on-grade home................................................................5-11

Figure 5-7. Elevating a slab-on-grade home without the slab. ......................................................................5-11

Figure 5-8. House in Zone A was detached from its slab foundation (which remains) and elevated on 

masonry piers. The floor system is supported by new wood joists (Mandeville, LA)..................5-12

Figure 5-9a through 5-9d. Elevating a slab-on-grade home with the slab attached. ........................................5-13

Figure 5-10a through 5-10c. Elevating by extending the walls of a solid masonry home................................5-16

Figure 5-11. Elevation of the floor levels in a row house to maximize living area above the BFE in Zone A...5-18

Figure 5-12a through 5-12c. Home elevated by adding a new second story over an abandoned lowest floor. 5-18

Figure 5-13a through 5-13d. Elevating a basement or crawlspace foundation home on piers.........................5-21
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING xi

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Figure 5-14. Home elevated on post or column foundations..........................................................................5-22

Figure 5-15. Home elevated on piles. .............................................................................................................5-23

Figure 6-1. New foundation is being prepared...............................................................................................6-4

Figure 6-2. Clearing pathways beneath the structure for lifting supports. ......................................................6-5

Figure 6-3. Pathways for lifting beams............................................................................................................6-6

Figure 6-4. Beams supported by cribbing are placed at critical lift points. .....................................................6-6

Figure 6-5. Hydraulic jacks lift the structure, and the home is separated from existing foundation...............6-7

Figure 6-6. Trailer wheel sets are placed beneath the lifting beams................................................................6-7

Figure 6-7. The move to the new site begins..................................................................................................6-8

Figure 6-8. House is lowered and connected to the foundation after the foundation is fully constructed......6-8

Figure 6-9. Typical mitigation reconstruction project...................................................................................6-12

Figure 7-1. Typical wet floodproofing.............................................................................................................7-3

Figure 7-2. Wall openings must allow floodwaters not only to enter the home, but also to rise and fall 

at the same rate as floodwaters outside the home.........................................................................7-6

Figure 7-3. Sketch of foundation plan of home with multiple enclosed areas, each with flood openings. 

Typical enclosures with flood openings (Left). Flood opening in typical crawlspace foundation 

(Right). ........................................................................................................................................7-6

Figure 7-4. The lateral and buoyancy force resulting from the same depth of flooding is much less on a 

home without a basement (a) than on a home with a basement (b). The pressure on basement 

walls is caused by water and saturated soils................................................................................7-11

Figure 7-5. Example of an exterior application of a spray-applied asphalt membrane (left) and an interior 

application of a fiber reinforced polymer wrap (right)..............................................................7-13

Figure 7-6. A way to seal an existing brick-faced wall is to add an additional layer of brick with a seal in 

between. Please note that weep holes (drainage) and wick drains are moved up to prevent 

moisture from getting inside the walls.......................................................................................7-13

Figure 7-7. In the “wrapped home” method, the lower portion of the home is protected with a temporary 

layer of polyethylene film. As shown, a temporary drainage line is also required.......................7-14

Figure 7-8. Heavy-gauge metal shield over sliding glass door opening. .......................................................7-16

Figure 7-9. Light-gauge metal shield held in place by permanently installed tracks.....................................7-16

Figure 7-10. Low window raised approximately 2 feet and original opening filled with brick......................7-17

Figure 7-11. Drainage system for a dry floodproofed home...........................................................................7-18

Figure 8-1. Structure protected by levee (on left) and floodwall (on right). ..................................................8-1

Figure 8-2. Levee construction........................................................................................................................8-2

Figure 8-3. Structure protected by a floodwall with decorative stone finish...................................................8-3

Figure 8-4. Two-foot-high water-filled temporary barrier protecting a residence from flooding.. .................8-4
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Figure 8-5. The City of Boulder, CO, installed a “pop up” closure to this floodwall at a City office building 

subject to flash floods. The closure floats up into place automatically when the site is flooded....8-7

Figure 8-6. Small patio floodwall with sump pump........................................................................................8-7

Figure 9-1. Air conditioning/heat pump compressor mounted on a brick pedestal outside an elevated 

home............................................................................................................................................9-3

Figure 9-2. Air conditioning/heat pump compressor mounted on a cantilevered platform attached to a 

home elevated on an open foundation.........................................................................................9-3

Figure 9-3. Water heater and furnace protected by a concrete floodwall with opening and gasketed 

shield............................................................................................................................................9-8

Figure 9-4. Anchoring a fuel storage tank with a concrete slab.......................................................................9-9

Figure 9-5. Example of an exterior backflow valve installed in a valve pit....................................................9-10

Tables

Table 2-1. Eligible Retrofit Activities by Program........................................................................................2-19

Table 3-1. Advantages and Disadvantages of Elevation ................................................................................3-19

Table 3-2. Relative Costs of Elevating a Home.............................................................................................3-20

Table 3-3. Advantages and Disadvantages of Relocation..............................................................................3-22

Table 3-4. Relative Costs of Relocation .......................................................................................................3-22

Table 3-5. Relative Costs of Demolition and Rebuilding .............................................................................3-24

Table 3-6. Advantages and Disadvantages of Wet Floodproofing .................................................................3-28

Table 3-7. Relative Costs of Wet Floodproofing...........................................................................................3-29

Table 3-8. Advantages and Disadvantages of Dry Floodproofing.................................................................3-31

Table 3-9. Relative Costs of Dry Floodproofing...........................................................................................3-32

Table 3-10. Advantages and Disadvantages of Levees and Floodwalls............................................................3-35

Table 3-11. Relative Costs of Levees and Floodwalls .....................................................................................3-36

Table 3-12. Relative Costs of Various Retrofit Measures.................................................................................3-38

Table 4-1. Requirements for Design Professional and Contractor Services..................................................4-13

Table 4-2. Retrofitting Methods for Substantially Improved or Substantially Damaged Homes...................4-17

Table 4-3. Retrofitting Methods for Homes That are NOT Substantially Improved or Damaged..................4-18

Table 7-1. Flood Damage-Resistant Materials................................................................................................7-9

Table 8-1. Considerations for Using Barriers ................................................................................................8-2
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING xiii

Acronyms

ASCE American Society of Civil Engineers

ASFPM Association of State Floodplain Managers

AST aboveground storage tank

BFE base flood elevation

CDC Centers for Disease Control

CMU concrete masonry unit

CRS Community Rating System

DFE design flood elevation

DHS U.S. Department of Homeland Security

DRC Disaster Recovery Center

FEMA Federal Emergency Management Agency

FIRM Flood Insurance Rate Map

FIS Flood Insurance Study

FMA Flood Mitigation Assistance

fps feet per second

HMA Hazard Mitigation Assistance

HMGP Hazard Mitigation Grant Program

HUD U.S. Department of Housing and Urban Development

HVAC heating, ventilation, and air conditioning

IBC International Building Code

ICC Increased Cost of Compliance 

IEBC International Existing Building Code

IRC International Residential Code
xiv SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

ACRONYMS 

LAG lowest adjacent grade

LiMWA limit of moderate wave action

LOMA Letter of Map Amendment

MEP mechanical, electrical, and plumbing

MiWA Minimal Wave Action

MoWA Moderate Wave Action

mph miles per hour

MSC Map Service Center

msl mean sea level

NAVD North American Vertical Datum

NFIA National Flood Insurance Act

NFIP National Flood Insurance Program

NGVD National Geodetic Vertical Datum

NRCS National Resources Conservation Service

OSHA Occupational Safety and Health Administration

OSB oriented-strand board

PDM Pre-Disaster Mitigation

PNP private non-profit

RFC Repetitive Flood Claims

SBA Small Business Administration

SFHA Special Flood Hazard Area

SFIP Standard Flood Insurance Policy

SHMO State Hazard Mitigation Officer

SHPO State Historic Preservation Office

SRL Severe Repetitive Loss

UL Underwriters Laboratories

USACE U. S. Army Corps of Engineers

U.S.C. United States Code

USDA U.S. Department of Agriculture

UST underground storage tank
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 1-1

1.0 About This Guide

The Third Edition of FEMA P-312, Homeowner’s Guide to Retrofitting, has been prepared to update the state of art in 

residential flood protection methods and reflect changes made to the National Flood Insurance Program (NFIP). 

1.1 Who This Guide Is For

The Federal Emergency Management Agency (FEMA) has prepared this guide specifically for homeowners who want to 

protect their homes from flooding. It provides clear information 

about the options available to you and straightforward guidance 

that will help you make decisions. This guide is designed for 

readers who have little or no experience with flood protection 

methods or building construction techniques. 

If you are an engineer, an architect, a construction contractor, or 

someone with skills in those fields, you may want to ask FEMA 

for copies of technical manuals that cover design and construction in greater detail. For example, all flood protection methods 

described in this guide are discussed in depth in FEMA P-259, 

Engineering Principles and Practices for Retrofitting Flood-Prone Residential 

Structures, Third Edition (FEMA. 2012a). If you work in a coastal 

area, FEMA P-55, Coastal Construction Manual: Principles and Practices of 

Planning, Siting, Designing, Constructing, and Maintaining Residential Buildings in Coastal Areas, Fourth Edition (FEMA. 2011b), may also be useful. If you would like to obtain copies of these 

documents or other FEMA documents referred to in this guide free of charge, you can download them from the 

FEMA Web site (http://www.fema.gov/resource-document-library) or call the FEMA Publications Service Center 

at 1-800-480-2520. See Appendix A for a list of documents concerning flood protection prepared by FEMA and 

other agencies and organizations.

In addition to FEMA publications, architects and engineers may want to obtain literature from the American Society of Civil Engineers (ASCE). ASCE 24, Flood Resistant Design and Construction provides minimum requirements for 

flood-resistant design and construction of structures located in flood hazard areas. ASCE 7, Minimum Design Loads for 

Buildings and Other Structures, may also be useful since formulas for flood loads are described in this document. 

DEFINITION

FEMA is an agency within the 

Department of Homeland Security 

(DHS) that administers the NFIP. The 

NFIP is a Federal program, created by 

Congress in 1968. The NFIP makes 

flood insurance available to communities that adopt and enforce floodplain 

management ordinance, regulation, 

or provisions of the building code that 

meet the minimum requirements of 

the NFIP regulations.
1-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

1 ABOUT THIS GUIDE

1.2 How This Guide Can Help You

You should take steps to protect your home if it has been damaged by flooding or is in an area where flooding is likely to 

occur. But first, you need to know what methods are available, 

how they work, how much they may cost, and whether they 

will meet your specific needs. This guide covers all of those issues. It also explains flood hazards and how they can damage 

your home. 

Flooding is only one of several natural hazards that may threaten 

your home. This guide includes maps that will help you determine whether your home is in an area where earthquakes or 

high winds occur, and it also explains when your retrofitting 

project should include protection against these hazards.

Your state and local governments probably have adopted building codes and other rules and regulations that you will need to 

know about. This guide explains how your local officials can 

advise you on those codes, rules, and regulations. Regardless 

of the flood protection method you choose, you may wish to 

consult with a licensed architect, engineer, or contractor for assistance with some of the retrofitting measures 

described in this guide. This guide describes the types of services you can expect design professionals and contractors to provide.

1.3 How To Use This Guide

To get the most from this guide, you should first read Chapters 2, 3, and 4. Chapter 2 explains retrofitting and, by 

describing how flood, wind, and earthquake forces can damage your home, helps you understand how retrofitting 

works. Chapter 2 also provides a discussion of Federal, State, and local financial assistance programs that may help 

pay for your retrofitting project. Chapter 3 provides short descriptions of the six flood protection methods covered 

by this guide. It gives you the information you will need as you begin to think about how to protect your home, 

including the approximate costs, advantages, and disadvantages of each method. Chapter 4 leads you through four 

steps that will help you decide which method or methods will best meet your needs. Chapter 4 also explains how 

to work with local officials, design professionals, and contractors.

When you finish Chapter 4, you will be ready to focus on a specific retrofitting strategy. In some cases, a single 

method may adequately address your needs. In other cases, a combination of methods may be best. Then you can 

move to Chapter 5, 6, 7, 8, or 9, depending on the method or methods you’ve chosen. Those chapters describe the 

methods in greater detail and include photographs and illustrations that show how the methods are applied. Chapter 9 explains how you can protect service equipment (utility systems; heating, ventilating, and air conditioning 

[HVAC] systems; and large appliances) in conjunction with the retrofitting method you have chosen. 

As you read this guide, you will often find information in the margins of pages—definitions (such as the one on 

the previous page), notes, and warnings. Each is identified by a special symbol:

DEFINITION – The meaning of a technical or other special term. Where a term is first used in the 

text, it is shown in bold type and the definition is provided in the margin. You can also find these and 

other definitions in Appendix B.

DEFINITION

In this guide, the term local officials refers to the employees of your 

community who are responsible for 

floodplain management, zoning, permitting, building code enforcement, 

and building inspection. The responsibilities of local officials vary from one 

community to the next. In your community, you may need to work with 

one or more of the following: floodplain administrator, building official, 

city engineer, and planning and zoning administrator. 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 1-3

ABOUT THIS GUIDE 1

NOTE – Supplemental information you may find helpful, including things to consider as you plan 

your retrofitting project, suggestions that can make the retrofitting process easier, and the titles and 

sources of other publications related to flood protection and retrofitting.

CROSS REFERENCE – Reference to another relevant part of the text or another source of information.

WARNING – Critical information that will help you avoid mistakes that could result in dangerous 

conditions, violations of your community’s ordinances or regulations, and possibly delays and higher costs in your retrofitting project. Be sure to read these warnings. If you are unsure about what a 

specific warning means or what to do to avoid the problem it describes, consult your local officials. 

Chapter 4 provides information about working with local officials.

A final note before you begin Chapter 2: No guide or other 

document of this type can anticipate every retrofitting situation 

or every concern a homeowner may have about undertaking a 

retrofitting project. If you have questions that this guide does 

not answer, consult your local officials. Other resources include:

FEMA’s Building Science Helpline, a technical assistance hotline, 

can be reached at 1-866-927-2104 (phone) or FEMA-Buildingsciencehelp@dhs.gov (email).

If FEMA has set up a Disaster Recovery Center (DRC) in your 

area in response to a Presidential Declaration of a Major Disaster, members of the DRC Mitigation staff can answer questions 

and advise you on recovery strategies. Call the FEMA Helpline at 

1-800-621-3362 for the location of a DRC in your area. 

Appendix A of this guide lists helpful publications from FEMA and other organizations. The FEMA Web site, 

http://www.fema.gov, has information about all of these resources and more.

Appendix C lists the staff members of the FEMA Regional Office for your State.

Appendix D identifies your State NFIP Coordinator and State Hazard Mitigation Officer (SHMO).

NOTE

Many government agencies, including 

FEMA and non-profit organizations, 

maintain sites on the Internet where 

you can find information about flooding, high winds, earthquakes, and 

other hazards. Appendix A includes a 

partial list of available sites at the time 

this guide was prepared.

HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 2-1

2.0 Introduction to Retrofitting

Every year, flooding causes an average of over 90 percent of the disaster-related property damage in the United 

States and accounts for an average of over 75 percent of all Presidential Disaster Declarations. In fact, between 2003 

and 2013, the NFIP paid an average of over $3.5 billion a year in flood claims. In 2012, the year of Hurricane 

Sandy, the NFIP paid over $8 billion in flood claims. 

Although recent improvements in construction practices and regulations have made new homes less prone to 

flood damage, many existing homes continue to be repetitively damaged by flooding. In fact, repetitive loss 

records account for approximately 30 percent of all claim payments made in the history of the NFIP. Between 

1978 and 2014, over 186,000 homes were flooded more than once. These homes alone accounted for approximately $15 billion in flood damages, subjecting the owners to a cycle of flooding and repairing. 

The good news is that this cycle of repetitive flood damage can be broken. Homeowners across the country have 

protected their homes from flooding using the techniques described in this guide. One example can be found in 

New Orleans, where many residential neighborhoods were inundated by Hurricane Katrina in 2005 (Figures 2-1 

and 2-2).

Figure 2-1. This home in 

New Orleans was inundated 

by 4 feet of water during 

Hurricane Katrina. 
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2 INTRODUCTION TO RETROFITTING

Figure 2-2. This home, from 

Figure 2-1, was elevated in a 

manner that added to both its 

appearance and its value. As 

a result of its elevation, the 

home avoided major damage 

from Hurricane Isaac in 2012. 

One family decided to take action after their home flooded during Hurricane Katrina. They hired a contractor to elevate their 

home on concrete piers so that it would be above the level of 

future, similar floods (Figure 2-2).

At the outset of the project, the homeowners were concerned 

about how the home would look after it was elevated. But once 

construction was complete, their concerns were alleviated. 

Access to the front door is now provided by a well-designed 

double staircase that also serves as an architectural focal point. 

In addition to providing protection from future floods, elevating 

the home created a space below that could be used for parking 

and storage. 

In other areas where flooding has caused repeated damage, 

entire homes have been relocated outside the flood hazard area 

or protected by floodwalls and levees designed as attractive 

landscaping features. As you read this guide, you will see that it 

is possible to protect your home from flooding while preserving or even enhancing its attractiveness and value.

NOTE

Any retrofitting project you undertake 

must meet the legal requirements of 

your community, including the floodplain management ordinances your 

community adopted to participate 

in the NFIP. By enforcing these ordinances, your community helps reduce 

future flood damages. As explained 

later in this chapter, the ordinances 

are based on the 1-percent-annualchance flood, also referred to as the 

“base flood.” Remember this term; you 

will encounter it many times as you 

read this guide. For more information, 

see Section 2.3.3.
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INTRODUCTION TO RETROFITTING 2

2.1 What Is Retrofitting?

You may be wondering, “What is retrofitting and why is it necessary?” Retrofitting is making changes to an existing building to protect it from flooding or other hazards, such as high winds and earthquakes. You have already 

seen one example of retrofitting, and you’ll learn about more in the following chapters. 

Construction technologies, including both methods and materials, continue to improve, as does our knowledge of hazards 

and their effects on buildings. Many existing homes were built 

when little was known about where and how often floods and 

other hazardous events would occur or how buildings should 

be protected. As a result, retrofitting has become a necessary and 

important tool in hazard mitigation. 

In addition to any retrofit completed on your home, updated 

Flood Insurance Rate Maps (FIRMs) and new legislation may 

have implications for your insurance premiums. Before making 

any changes to your home, FEMA strongly recommends that 

you discuss retrofit options with your insurance agent and work 

closely with design professionals and State and local officials. 

2.2 Types of Flooding

This guide focuses primarily on retrofitting for flood protection. If you decide to retrofit your home, you’ll need 

to be aware of other potential hazards as well, such as high winds and earthquakes. They are discussed later, but 

first you must understand flooding—where and how it occurs, the nature of the threat it poses, and how it can 

affect your home.

Most of the flooding that occurs in the United States is either 

riverine or coastal flooding, although flooding also occurs 

around lakes and ponds, and in areas where storm drainage

systems are not adequate. Riverine flooding, as its name implies, 

occurs when rivers and streams overflow their banks (Figure 

2-3). Riverine floodwaters can move quite rapidly, as in a flash 

flood, or very slowly, as they often do where the land is gently 

sloping or flat. The primary causes of riverine flooding are rainfall and rapidly melting snow (and sometimes a combination 

of both). Water from rain and rapidly melting snow eventually 

finds its way into stream channels. When the amount of water 

being carried by a stream exceeds the capacity of the stream 

channel, it spreads out into the area along the stream, commonly referred to as the floodplain. Usually, the homes and other 

buildings at greatest risk from riverine flooding are those near 

the stream channel, where the depths and speed of floodwaters 

are often greatest. 

DEFINITION

Hazard mitigation is sustained action taken to reduce or eliminate 

long-term risk to people and property 

from hazards such as floods, hurricanes, earthquakes, and fires.

DEFINITION

Flash flood: A flood caused by heavy 

or excessive rainfall in a short period 

of time, generally less than 6 hours. A 

flash flood rises and falls very quickly 

and is usually characterized by high 

flow velocities.
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2 INTRODUCTION TO RETROFITTING

Figure 2-3. These homes 

in Gays Mills, WI, were 

inundated by riverine 

flooding during the Midwest 

floods of 2008.

Figure 2-4. The extreme 

impact of large, fast-moving 

waves, combined with the 

removal of supporting soil 

by erosion and scour, can 

have devastating effects on 

buildings exposed to coastal 

flooding. Hurricane Floyd 

destroyed this home along 

the coast of North Carolina 

in 1999.

Coastal flooding, which is caused by storm surge and wave 

action, primarily affects coastal areas, especially those along 

the beachfront, but it can also affect areas around bays and can 

back up along rivers and streams that empty into bays. Coastal 

flooding is most dangerous, and causes the most severe damage, 

where large waves are driven inland by the wind (Figure 2-4). 

These wind-driven waves occur primarily along the open coast, 

where they can destroy homes, wash away protective dunes, and 

erode the soil, often to the extent that the ground surface is lowered several feet. But they can also move inland where the land 

is flat and there are no large dunes or other obstacles to break 

them. In these areas, the level of damage can rival that along the 

open coast.

DEFINITION

Storm surge is the rise in the level of 

the ocean that results primarily from 

strong winds associated with hurricanes and other storms. Decreased 

atmospheric pressure from these 

storms also makes a small contribution to storm surge.
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INTRODUCTION TO RETROFITTING 2

Coastal flooding can also move inland into low-lying areas 

beyond the limit of wave action. The danger in these areas is 

primarily from inundation due to storm surge but, even here, 

fast-moving floodwaters can result in scour and erosion around 

building foundations.

Another cause of flooding, which can affect homes outside 

identified floodplains, is the limited capacity of local drainage 

systems, including storm sewers, culverts, and drainage ditches. 

These systems are usually designed to carry a specific amount of 

water, which is referred to as the “design capacity” of the system. When heavy rainfall over an area causes the design capacity 

of the system to be exceeded, water will begin to back up and 

fill low-lying areas near system inlets and along open ditches. 

Depending on the amount and intensity of rainfall, the floodwater may continue to rise and may eventually affect homes.

A similar problem occurs when drainage system inlets are 

plugged or obstructed by mud or other debris and when drainage system outlets are submerged by water during riverine or 

coastal floods. In the latter situation, water can flow backwards 

in the system and reach areas that otherwise might not have 

flooded.

2.3 How Flooding Can Damage Your 

Home

To understand how flooding can damage your home, you need 

to know about six important flood characteristics: depth/elevation, flow velocity, frequency, rates of rise and fall, duration, 

and debris impact. Most of these characteristics apply to both 

riverine and coastal flooding, and they can vary—sometimes 

greatly—from one place to another. The flood conditions at a 

particular site, such as the location of your home, are determined largely by the combination of these characteristics. The 

following paragraphs explain these characteristics. Section 2.3 

and Chapter 4 explain how you can determine the flood conditions at your home.

2.3.1 Depth/Elevation of Flooding

The depth and elevation of flooding are so closely related that, 

for the purposes of this discussion, they can be viewed as a single characteristic. Flood depth is the height of the floodwater 

above the surface of the ground or other feature at a specific point. Flood elevation is the height of the floodwater above 

an established reference datum. The standard datums used by 

DEFINITION

Wave action refers to the characteristics and effects of waves that move 

inland from an ocean, bay, or other 

large body of water. Large, fast-moving waves can cause extreme erosion 

and scour, and their impact on buildings can cause severe damage. 

During hurricanes and other highwind events, storm surge and wind 

increase the destructiveness of waves 

and cause them to reach higher elevations and penetrate further inland.

Scour refers to a localized loss of soil, 

often around a foundation element. 

Erosion refers to a general lowering of the ground surface over a wide 

area. 

Intensity of rainfall refers to the 

amount of rain that falls during a given 

amount of time. It is usually expressed 

in inches of rainfall per hour. The higher the number of inches per hour, the 

greater the intensity.

DEFINITION

An elevation datum is an arbitrary 

surface that serves as a common reference for the elevations of points 

above or below it. Elevations are 

expressed in terms of feet, meters, 

or other units of measure and are 

identified as negative or positive, depending on whether they are above or 

below the datum. Three common elevation datums are mean sea level 

(msl), NGVD, and NAVD.
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2 INTRODUCTION TO RETROFITTING

most Federal agencies and many State and local agencies are the 

National Geodetic Vertical Datum (NGVD) and the North American Vertical Datum (NAVD); however, other datums are also in 

use. The use of other datums is important because elevations of 

the ground, floodwaters, and other features cannot be meaningfully compared with one another unless they reference the same 

datum. If a survey has established a benchmark, this point can 

be used to determine the flood depth and elevation. When the 

elevation of the ground (or another surface such as the lowest 

floor of your home) and the elevation of the floodwaters both 

use the same datum or benchmark, the flood depth at any point 

is equal to the flood elevation at that point minus the elevation of the ground (or other surface) at that point. Figure 2-5 

illustrates this relationship. Ground elevations are established 

by surveys; flood elevations may be calculated or they may be 

known from water marks left by past floods.

The depth of flooding at your home is important primarily because floodwaters, even when they are not moving, 

exert pressure on structural components such as walls and concrete floor slabs. The pressure exerted by still water is called 

“hydrostatic pressure.” It is caused by the weight of the water, 

so it increases as the depth of the water increases. As shown in 

Figure 2-6, floodwater, including water that has saturated the soil 

under the home, pushes in on walls and up on floors. The 

upward force on floors is called “buoyancy.” 

DEFINITION

A benchmark is a reference point established by a survey with a precisely 

known relationship to a datum. 

Under the NFIP, the lowest floor of 

a building is the floor of the lowest 

enclosed area within the building, 

including the basement. The only exception is an enclosed area below an 

elevated building, but only when the 

enclosed area is used solely for parking, building access, or storage and 

is compliant with relevant regulations. 

The elevation of the lowest floor can 

be very important in retrofitting, as you 

will see in later chapters.

Buoyancy refers to the upward hydrostatic force that floodwater exerts 

on the floors of homes with enclosed 

spaces below the flood level.

Figure 2-5. In this example, 

the 1-percent-annual-chance 

flood elevation is 391.6 

feet (10.1 feet above the 

benchmark elevation of 381.5 

feet), and the elevation of the 

lowest floor of the home is 

389.3 feet (7.8 feet above the 

same benchmark). The flood 

depth above the lowest floor 

is therefore equal to 391.6 

feet − 389.3 feet, or 2.3 feet 

during the 1-percent-annualchance flood.

As shown in Figure 2-6b, water that has saturated the soil poses a special hazard for basement walls. Because 

hydrostatic pressure increases with the depth of the water, the pressure on basement walls is greater than the pressure on the walls of the upper floor, as indicated by the arrows in the figure. This pressure is made even greater by 

the weight of the saturated soil that surrounds the basement.
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INTRODUCTION TO RETROFITTING 2

Figure 2-6. Hydrostatic 

pressure acts on walls and 

concrete slab floors. The 

weight of saturated soils 

adds to the pressure on 

basement walls. Figure 

2-6a shows a home with a 

concrete slab floor. Figure 

2-6b shows a home with a 

basement.

The walls of homes built using standard wood-frame or 

masonry construction are not designed to resist this pressure. If 

the pressure exceeds the strength of the walls (including basement walls), it can push them in or out (Figure 2-7), cause 

extensive structural damage, and possibly cause the home to 

collapse. In some areas, the buoyant force of hydrostatic pressure on basement floors has pushed homes entirely out of the 

ground.

If water is allowed to enter, the hydrostatic pressures on both 

sides of the walls and floor become the same, or equalized 

(Figure 2-8), and the walls are much less likely to fail. As 

discussed in Chapters 3, 5, 7, and 8, this is an important consideration in some types of retrofitting methods.

ment as “any area of the building 

having its floor subgrade on all sides.” 

Note that the NFIP definition of basement does not include what is typically 

referred to as a “walkout-on-grade” 

basement, whose floor would be at or 

above the surface of the ground that 

touches the outside walls of the building on at least one side (see Section 

3.1.2). This ground surface is referred 

to as the “adjacent grade.”

DEFINITION

The NFIP regulations define a baseFigure 2-7. The walls of this 

basement in Wisconsin failed 

because of the pressure 

exerted by water and 

saturated soil.
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2 INTRODUCTION TO RETROFITTING

Figure 2-8. Once water 

enters the home, hydrostatic 

pressure is equalized. Figure 

2-8a shows a home with a 

concrete slab floor. Figure 

2-8b shows a home with a 

basement.

2.3.2 Flow Velocity

Flow velocity is the speed at which floodwaters move. It is usually measured in feet per second (fps). Flow velocities during riverine floods can easily reach 5 to 10 fps and, in some situations, may be even greater. Expressing 

velocities in fps is common in floodplain studies and engineering analyses. It may be helpful to relate fps to a more 

familiar unit of measure. For example, 10 fps is roughly equal to 7 miles per hour (mph). 

The velocity of riverine floodwaters depends on a number of factors; one of the most important is the slope of the 

stream channel and floodplain. As you might expect, floodwaters will generally move much faster along streams 

in steep mountainous areas than streams in flatter areas. However, even within the same floodplain, flow velocity 

can still vary. As water flows over the ground, its velocity depends largely on the roughness of the ground surface. 

For example, water will flow more swiftly over parking lots, roads, and other paved surfaces, and will flow more 

slowly over ground covered with large rocks, trees, dense vegetation, or other obstacles. Also, flow velocities in the 

floodplain will usually be higher nearer the stream channel than at the outermost fringes of the floodplain, where 

water may flow very slowly or not at all. In areas subject to coastal flooding, velocities depend largely on the speed 

of the wind and, like riverine flow velocities, on the slope and roughness of the ground surface.

If your home is in an area where floodwaters are flowing, especially if they are moving more than about 5 fps, the 

flow velocity is important for several reasons. Flowing water pushes harder on the walls of a building than still 

water. So instead of just the hydrostatic pressure caused by the weight of the floodwater resting against the walls 

of your home, you have the additional pressure of moving water, referred to as “hydrodynamic pressure” (Figure 

2-9). As water flows around your home, it pushes against the side of the home that faces the flow (the upstream 

side). As it flows past the sides of the home, it creates friction that can tear at wall coverings, such as siding. On 

the side of the home that faces away from the flow (the downstream side), the water creates a suction that pulls 

on walls. In some situations, the combination of these forces can destroy one or more walls (Figure 2-10), cause 

the home to shift on its foundation, or even sweep the home away.

Flowing water can also cause erosion and scour. As previously discussed, erosion refers to a general lowering of 

the ground surface over a wide area. Scour refers to a localized loss of soil, often around a foundation element. 

Both erosion and scour can weaken the structure of a home by removing supporting soil and undermining the 

foundation. In general, the extent and depth of erosion and scour increase as the flow velocity and size of the 

home increase. Also, keep in mind that any objects being carried by floodwaters will be moving at roughly the 

same speed as the water. The dangers associated with these objects are discussed in Section 2.3.6.
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INTRODUCTION TO RETROFITTING 2

Figure 2-9. Moving water acts on the front, sides, and back of a home.

Figure 2-10. Water moving at 

high velocity destroyed the 

wall of this home and caused 

the building to shift on its 

foundation.

2.3.3 Flood Frequency

You may have been told that your home is in “the 100-year” floodplain, or you may have heard that term used to 

describe a specific flood. You may also have heard similar terms used, such as “50-year flood” or “500-year flood.” 

These terms can be misleading. Flood frequencies are usually determined through statistics and engineering 

analyses performed by floodplain management agencies and other organizations responsible for implementation 

of flood control programs and floodplain regulation. The results of those analyses define the probability, expressed 

as a percentage, that a flood of a specific size on a specific stream will be equaled or exceeded in any year. 

For example, the flood that has a 1 percent probability (1 in 100) of being equaled or exceeded in any year is 

sometimes referred to as the 100-year flood. This term is simply a convenient way to express probability. It should 

not be interpreted to mean a flood that happens exactly once every 100 years. Nor does it imply that once a 
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2 INTRODUCTION TO RETROFITTING

100-year flood occurs there is little risk of another 100-year flood occurring in the near future. To the contrary, 

changes in climatic conditions, such as those caused by El Niño, often result in clusters of floods that occur over 

relatively short times at the same location. In this publication, the term 1-percent-annual-chance flood is used to 

describe the 100-year flood.

For most homeowners, the value of these terms is that they indicate relative frequencies and sizes. Over time, a 

1-percent-annual-chance (100-year) flood is expected to occur less often than a 2-percent-annual-chance (50-year) 

flood and more often than a 0.2-percent-annual-chance (500-year) flood. In addition, a 1-percent-annual-chance 

flood will be more severe than a 2-percent-annual-chance flood and less severe than a 0.2-percent-annual-chance 

flood. For example, if your home is in the 1-percent-annual-chance floodplain of a nearby stream or river, the 

1-percent-annual-chance flood elevation at your home will be lower than the 0.2-percent-annual-chance flood 

elevation, and the water from a 2-percent-annual-chance flood might not even reach your home. 

The 1-percent-annual-chance flood is particularly important for homeowners because it is the basis of NFIP flood 

insurance rates and regulatory floodplain management requirements. These requirements are discussed in detail in 

Section 2.5. In the NFIP, the 1-percent-annual-chance flood is referred to as the “base flood.” The elevation associated with the base flood is referred to as the “base flood elevation” (BFE), and the floodplain associated with the 

base flood is referred to as the “special flood hazard area” (SFHA). Other Federal agencies, such as the U.S. Army 

Corps of Engineers (USACE), use the 1-percent-annual-chance flood for planning and engineering design, as do 

many State and local agencies. These agencies often have their own names for the 1-percent-annual-chance flood. 

2.3.4 Rates of Rise and Fall

You may not have heard these terms before, but they describe important characteristics of flooding: how rapidly 

the elevation (and therefore the depth) of water increases and decreases during a flood. These rates are usually 

expressed in terms of feet or inches per hour. Floodwaters with high flow velocities, such as those in areas of steep 

terrain, and water released by the failure of a dam or levee, usually rise and fall more rapidly than slower-moving 

floodwaters, such as those in more gently sloping floodplains.

Rate of rise is important because it affects how much warning you will have of an impending flood. For example, 

homeowners in the floodplains of large rivers like the Mississippi and Missouri may know days in advance that 

flooding is occurring upstream and will eventually reach their homes. But in the floodplains of streams with rapid 

rates of rise, homeowners may have only a few hours’ notice of a coming flood or perhaps none at all. With adequate warning, you will be better prepared to take steps to protect yourself and your property. Warning time is 

particularly important for flood protection methods that depend on action you must take. Chapters 3, 4, 7, and 8 

further discuss this issue.

Rates of rise and fall are important also because of their effect on hydrostatic pressure. As explained in the 

discussion of flood depth/elevation, hydrostatic pressure is most dangerous for a home when the internal and 

external pressures are not equalized. This situation occurs when the level of water inside the home is significantly 

higher or lower than the level outside. When floodwaters rise rapidly, water may not be able to flow into a home 

quickly enough for the level inside the home to rise as rapidly as the level outside. Conversely, when floodwaters fall 

rapidly, water that has filled a home may not be able to flow out quickly enough, and the level inside will be 

higher than the level outside. In either situation, the unequalized hydrostatic pressures can cause serious structural 

damage, possibly to the extent that the home collapses.
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INTRODUCTION TO RETROFITTING 2

2.3.5 Duration

Duration is how long a flood lasts, or how long it takes for the creek, river, bay, or ocean to return to its normal 

level. As a homeowner, you may be more interested in how long floodwaters remain in or around your home 

or perhaps how long they block nearby streets. In many floodplains, duration is related to rates of rise and fall. 

Generally, water that rises and falls rapidly will recede more rapidly, and water that rises and falls slowly will recede 

more slowly. An example of this relationship is the extensive flooding that occurred in the broad, flat floodplains 

of the Midwest in 2008. In those areas, floodwaters rose slowly and remained high for many weeks or longer.

If your home is flooded, duration is important because it determines how long the structural members (such as 

the foundation, floor joists, and wall studs), interior finishes (such as drywall and paneling), service equipment 

(such as furnaces and hot water heaters), and building contents will be affected by floodwaters. Long periods of 

inundation are more likely to cause greater damage than short periods. Duration can also determine how long 

your home remains uninhabitable.

2.3.6 Debris Impact

Floodwaters can pick up and carry objects of all types—from small to large, from light to heavy—including trees, 

portions of flood-damaged buildings, automobiles, boats, storage tanks, mobile homes, and even entire homes. 

In cold climates, wintertime floods can also carry large pieces of ice. Dirt and other substances, such as oil, gasoline, sewage, and various chemicals, can also be carried by floodwaters. All of these types of debris add to the 

dangers of flooding. Even when flow velocity is relatively low, large objects carried by floodwaters can easily damage 

windows, doors, walls, and, more importantly, critical structural components of your home. As velocity increases, 

so does the danger of damage from debris. If floodwaters carrying large amounts of dirt or hazardous substances 

enter your home, damages may be greater. In addition, your cleanup costs are likely to be higher and your cleanup 

time longer.

As you read the remaining sections of this guide, keep these flood characteristics and their effects in mind. 

Section 2.3 and Chapter 4 explain how you can find out more about flooding in your area, including flood elevations near your home.

2.4 Other Hazards

Two more hazards you should be aware of are high winds (including hurricanes) and earthquakes. For homes 

in areas subject to these hazards, some retrofitting methods are more appropriate than others. Chapters 3 and 4 

further discuss this issue. But, regardless of the method you choose, if your home is in a high-wind or earthquake 

hazard area, your design professional or contractor must ensure that all structural changes made can withstand not 

only the expected flood forces, but the expected forces of winds or earthquakes as well. 

Wind is similar to flowing water in that it pushes against the 

side of the home that faces the wind and pulls on the side that 

faces away (Figure 2-11). Wind passing over a home can exert 

a lifting force on the home. The combination of push, pull, and 

lift acts on the home, including the foundation, and can result in extensive damage if the structural system and building 

envelope are not adequately designed and constructed. 

DEFINITION

The building envelope is the entire 

exterior surface of a building (including walls, doors, and windows) that 

encloses or envelopes the space 

within.
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2 INTRODUCTION TO RETROFITTING

The ability of the wind to damage a building is increased if the wind or windborne debris breaches the building 

envelope by breaking windows, collapsing doors, or puncturing walls. Once the envelope is breached, wind will 

enter the building and the pressure on the walls and roof will increase, as shown in Figure 2-11. Wind and flood 

forces can combine in different ways, depending on the directions of the wind and flood flow. When the wind and 

flood flow direction are the same, the load on the home is greater than the load from either wind or flood alone. 

Figure 2-11. Wind forces 

on a sealed building are 

less than wind forces on a 

building with an opening.

The movement of the ground during an earthquake can place 

large horizontal and vertical loads on a home (Figure 2-12). 

Like the loads that result from flood flow and wind, earthquake 

loads can cause extensive damage to a home if they have not 

been accounted for in the structural design.

High-wind and earthquake hazards vary throughout the United States. In Chapter 4, you will find maps that show the areas 

where these hazards are greatest. For more information on retrofitting for wind refer to FEMA P-804, Wind Retrofit Guide for 

Residential Buildings (FEMA.2010c), and for more information on 

retrofitting for earthquakes refer to FEMA 232, Homebuilders’ Guide 

to Earthquake-Resistant Design and Construction (FEMA. 2006). 

2.5 Federal, State, and Local Regulations

In most communities throughout the United States, construction in floodplains is governed by combinations of 

Federal, State, and local regulations; however, floodplain development can also be regulated wholly, or in part, by 

the International Codes (I-Codes). The I-Codes are a comprehensive, consensus-based set of model building codes 

that are often adopted at the State or local level. At the Federal level, FEMA administers the NFIP. Congress created 

the NFIP in 1968 when it passed the National Flood Insurance Act (NFIA). The NFIP is a voluntary program for 

communities. Its goal is to reduce the loss of life and the damage caused by flooding, to help the victims of floods, 

and to lower the costs of flood damage borne by the taxpayer. Communities participate in the NFIP in several ways:

n Guiding future development away from flood hazard areas

n Requiring that new buildings, Substantially Improved existing buildings, and repair of Substantially 

Damaged existing buildings in the SFHA be constructed in compliance with floodplain management 

ordinance, regulation, or provisions of the building code intended to reduce flood damage

Figure 2-12. Earthquake forces act in both 

horizontal and vertical directions. 

Earthquake

Motion

Earthquake Motion
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INTRODUCTION TO RETROFITTING 2

n Providing floodplain residents with financial assistance 

after floods

n Transferring the cost of flood losses from the taxpayer 

to the owners of flood-prone buildings by requiring 

the purchase of flood insurance for buildings in the 

SFHA

The NFIP operates through a partnership between the Federal Government, the States, and individual communities such as 

counties and incorporated cities, towns, and villages. 

A participating community adopts and enforces a floodplain 

management ordinance, regulation, or provisions of the building code to regulate development within that floodplain, 

including new construction, Substantial Improvement of existing buildings, and repair of Substantially Damaged buildings. 

In return, federally backed flood insurance is made available to 

property owners and renters who live in the community. 

A participating community’s floodplain management ordinance, regulation, or provisions of the building code must, at a 

minimum, meet the requirements of the NFIP regulations, but 

each community is free to establish additional or more stringent 

requirements to provide additional protection. For example, the 

regulatory floodplain defined by a community must include 

the entire SFHA, but it may also include other flood hazard 

areas within the community. Additionally, some States require 

communities to adopt and enforce floodplain management 

requirements that exceed the minimum requirements of the NFIP.

These points are particularly important because of their potential effect on your retrofitting project. In this guide, 

you will find many references to requirements included within your community’s floodplain management ordinance, regulation, or provisions of the building code. These are the minimum requirements that all communities 

must adopt and enforce in their floodplain management ordinance, regulation, or provisions of the building code 

to be compliant with the NFIP regulations. Remember that you must comply with your community’s requirements, 

which may be more stringent.

Usually, communities enforce other requirements that affect construction, both inside and outside of the regulatory floodplain. These requirements include those associated with building codes and land use regulations, such 

as zoning and subdivision ordinances. 

2.5.1 The Community Rating System

The NFIP Community Rating System (CRS) is a voluntary incentive program that recognizes and encourages community floodplain management actions that exceed the minimum NFIP requirements. Flood insurance premiums 

are discounted to reward community actions that meet the three goals of the CRS. The three goals of the CRS 

are to:

DEFINITION

Under the NFIP, an improvement of 

a building (such as reconstruction, 

rehabilitation, or an addition) is considered a Substantial Improvement

if its cost equals or exceeds 50 percent of the market value of the building 

before the start of construction of the 

improvement.

Similarly, damage to a building, regardless of the cause, is considered 

Substantial Damage if the cost of 

restoring the building to its beforedamage condition would equal or 

exceed 50 percent of the market value of the building before the damage 

occurred. Consult your local officials 

about determining the value of your 

home.

For more information, consult your 

local officials, or refer to FEMA P-758, 

Substantial Improvement/Substantial 

Damage Desk Reference (2010).
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2 INTRODUCTION TO RETROFITTING

n Reduce flood damage to insurable property

n Strengthen and support the insurance aspects of the NFIP

n Encourage a comprehensive approach to floodplain management 

When communities participate in the CRS, flood insurance rates for insured property owners and renters are 

discounted in increments of 5 percent to a maximum discount of 45 percent, based on 18 creditable activities. 

The activities are organized under four categories:

n Public information (e.g., offering references on flood insurance and flood protection at the public library)

n Mapping and regulations (e.g., guaranteeing that a portion of currently vacant floodplain will be kept free 

from development)

n Flood damage reduction (e.g., acquiring, elevating, and/or relocating flood-prone buildings so that they 

are out of the floodplain)

n Flood preparedness (e.g., providing early flood warnings to the public)

To apply for CRS participation, a community submits documentation of its floodplain management activities to 

the Insurance Services Office, which works on behalf of FEMA and the insurance companies. Specific information 

about CRS and the application process can be found at the CRS online resource center at http://training.fema.gov/

EMIWeb/CRS/. 

2.5.2 Flood Insurance Rate Maps

To provide communities with the information they need to enact and enforce floodplain management ordinance, 

regulation, or provisions of the building code, FEMA conducts floodplain studies for communities throughout 

the United States and publishes the results in Flood Insurance Studies (FISs) and FIRMs (Figure 2-13). The FIS 

for your community provides information about the names and locations of flood sources; historical flood data; 

flood elevations of varying frequency, including BFEs; areas inundated by the various magnitudes of flooding; and 

boundaries of the SFHA and floodway. This information is presented on FIRMs, which are used by FEMA and 

local communities to establish flood insurance rates. 

DEFINITION

The regulatory floodway is the channel of a river or other watercourse and the adjacent land areas that 

must be reserved in order to discharge the base flood without cumulatively increasing the water surface 

elevation more than a designated height (44 CFR §59.1). 

More simply put, the floodway is the portion of the SFHA where new development is strictly regulated to 

prevent flood elevations from increasing. The flood hazard is usually greater in the floodway than in the 

surrounding areas of the SFHA, referred to as the “floodway fringe.” Floodwaters in the floodway fringe 

are typically shallower and have less velocity. 

NFIP regulations do not prohibit development in all portions of the SFHA. Instead, the regulations require that residential buildings in the SFHA be elevated to or above the community’s BFE. But floodplain 

development can reduce the amount of space available to pass floodwaters, which can increase flood 

elevations. For this reason, the NFIP and local communities prohibit Substantial Improvement and new 

construction in the floodway. 
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INTRODUCTION TO RETROFITTING 2

Figure 2-13. This FIRM for riverine flooding shows the SFHA (Zone AE), floodway (hatch-marked Zone AE along centerline 

of river channel), and areas outside the SFHA (Zone X). The area between the limits of the base flood and 0.2-percentannual-chance flood are delineated by shaded Zone X. Areas above the 0.2-percent-annual-chance flood are delineated by 

unshaded Zone X.

FIRMs are available online at FEMA’s Map Service Center (MSC): http://www.msc.fema.gov. The site allows you to 

search for your flood map in one of four ways:

n Searching for your address

n Using the catalog, which allows you to select your State, county, community, and flood map from a list

n Using a map search, which allows you to zoom into your community from a map of the United States

n Searching for a map panel by ID Number

Once you find your FIRM, you can create a printable FIRMette using the MSC Viewer. A FIRMette is a full-scale 

section of a FEMA FIRM that you create for yourself online. There is no cost for making a FIRMette. FIRMettes are 

used by many different parties such as community officials, mortgage lenders, real estate agents, design professionals, insurers, land developers, engineers, and surveyors.

The MSC Viewer allows you to zoom to the area you want to be included in your FIRMette and format your printable map. You can save your FIRMette either as an Adobe PDF file or as a TIFF file. The Map Service Center offers a 

step-by-step tutorial on creating FIRMettes.
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Other Federal agencies, such as the USACE, U.S. Geological Survey, and Natural Resources Conservation Service 

(formerly U.S. Soil Conservation Service), also publish flood information, as do some State and local agencies. This 

information is often useful as a supplement to FISs and FIRMs. But, because it is developed to meet other needs, 

it is not used for the NFIP unless it has been reviewed and approved by FEMA.

If you have questions about flood hazards in your community, including the limits of the regulatory floodplain, 

flood elevations, or sizes and frequencies of past floods, check with your local officials. Usually, they will have 

copies of the FIS and FIRM for your community. They can also help you determine whether your home is in the 

regulatory floodplain and advise you about flood protection methods, including those described in this guide. 

Local officials can also advise you about floodplain management requirements, building codes, and other requirements that may determine the types of changes you can make to your home. See Chapter 4 for more information 

about working with local officials. You can also get help from your FEMA Regional Office (Appendix C) and the 

office of your NFIP State Coordinator (Appendix D).

2.6 Financial Assistance for Retrofitting 

2.6.1 Federal Programs 

FEMA and other Federal agencies have an array of financial assistance programs that assist States, communities, and 

individual property owners mitigate the negative effects of flood hazards. You may be eligible to receive financial 

assistance through one or more of these programs that will help pay for some of the retrofitting projects documented in this guide. Check with your local officials, the FEMA Regional Office for your State (Appendix C), your 

NFIP State Coordinator (Appendix D), or your State Historic Preservation Office (SHPO) (Appendix E).

If a Presidential Major Disaster Declaration has been issued for 

your area, you may want to seek information from FEMA and 

the State and local government representatives supporting the 

post-disaster recovery of your community. Keep in mind that 

funding for assistance programs is limited; often not everyone’s 

needs can be met. Many Federal assistance programs provide 

grants to State and local governments, who must then set priorities for the use of the grant funds, including any potential use 

by individual property owners. Additionally, not all methods of 

retrofitting are eligible for funding. 

Help from FEMA

Increased Cost of Compliance

One of the benefits provided by the NFIP is Increased Cost of 

Compliance (ICC) coverage. If your home is covered by a Standard Flood Insurance Policy (SFIP), is in an SFHA, and has been 

declared by your community to be Substantially Damaged or repetitively damaged by flood, ICC will help pay for certain types 

of retrofitting. ICC coverage is available for most SFIPs. 

NOTE

This section is not meant to be an 

all-inclusive description of Federal 

assistance. Following a Presidential 

Major Disaster Declaration, State 

and local officials will be briefed on 

the available types of post-disaster 

assistance.

NOTE

If a flood in your area is a federally declared disaster, you must register with 

FEMA to obtain assistance. The directions at http://www.fema.gov will walk 

you through the application process.
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INTRODUCTION TO RETROFITTING 2

If your home sustains a flood loss and the community has declared it Substantially Damaged or repetitively 

damaged, ICC will help pay the cost (up to $30,000 effective May, 2011) for the following retrofitting methods:

n Elevation: This raises your home to or above your community’s adopted design flood elevation (DFE) (see 

Chapters 3 and 5). 

n Relocation: This includes moving your home to another floodplain location on your lot and elevating it 

or moving it completely out of the regulatory floodplain (see Chapters 3 and 6).

n Demolition: This razes your home and restores the original property (see Chapters 3 and 6).

As noted earlier, your community’s floodplain management ordinance, regulation, or provisions of the building 

code must include a requirement for Substantial Damage. Substantial Damage as defined in Section 2.5. 

Some communities may have adopted a cumulative Substantial Damage or repetitive loss provision so that 

repetitively damaged buildings can qualify for an ICC claim payment. In order for buildings to qualify for a claim 

payment under ICC coverage as a “repetitive loss structure” the building must be covered by a contract for flood 

insurance and incur flood-related damages on two occasions during a 10-year period ending on the date of the 

event for which the second claim is made, in which the costs of repairing the flood damage, on the average, 

equaled or exceeded 25 percent of the market value of the building at the time of each such event. Note that ICC 

availability under this provision applies only if the community has adopted a cumulative Substantial Damage or 

repetitive loss provision in the floodplain management ordinance, regulation, or provisions of the building code. 

Also, note that under the NFIP, communities are not required to adopt a repetitive loss provision in their floodplain management ordinance, regulation, or provisions of the building code. 

Remember, communities with a more restrictive floodplain management ordinance, regulation, or provisions of 

the building code may require a greater level of protection. If for example, your community requires new and 

Substantially Improved or Substantially Damaged buildings to be elevated 1 or more feet above the BFE, ICC allows 

for an ICC claim payment up to the $30,000 limit of coverage. 

An ICC claim may also be paid for a combination of retrofitting actions. For example, ICC coverage allows for 

a claim payment for the cost of demolition and elevation at the same or another site within the SFHA. The ICC 

payment to demolish and elevate your home is limited to $30,000. 

To learn more about ICC coverage, review your SFIP and contact your insurance agent, your community floodplain 

management official, the FEMA Regional Office that serves your community (Appendix C), or the office of your 

NFIP State Coordinator (Appendix D). If a Presidential Declaration of Major Disaster has been issued for your area, 

you can get help from the Mitigation and Insurance Desk at the local DRCs. In many cases, the ICC payments are 

used to offset the non-Federal cost-share to participate in a disaster assistance program. 

Unified Hazard Mitigation Assistance Program

FEMA’s Hazard Mitigation Assistance (HMA) grant programs present a critical opportunity to reduce the risk to 

individuals and property from natural hazards while simultaneously reducing reliance on Federal disaster funds. 

Hazard mitigation is the only phase of emergency management specifically dedicated to breaking the cycle of 

damage, reconstruction, and repeated damage. HMA programs provide pre- and post-disaster funding to States, 

Territories, Indian Tribal governments, local governments, and eligible private non-profits (PNPs) for activities 

that are consistent with the National Mitigation Framework’s Long-term Vulnerability Reduction capability. Qualified private non-profits (PNPs) and individual homeowners are also eligible to receive HMA grant funds, but they must 

apply through a State agency or local government. 
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The statutory origins of each HMA program differ, but their goals are the same: reduce community vulnerability 

to disasters, promote individual and community safety and resilience, promote community vitality after an incident, and reduce response and recovery resource requirements in the wake of a disaster. Three grant programs are 

currently included in the Unified HMA program:

The Hazard Mitigation Grant Program (HMGP) is authorized by Section 404 of the Robert T. Stafford Disaster 

Relief and Emergency Assistance Act, as amended (the Stafford Act), Title 42, United States Code (U.S.C.) 5170c. 

The key purpose of HMGP is to ensure that the opportunity to take critical mitigation measures to reduce the risk 

of loss of life and property from future disasters is not lost during the reconstruction process following a disaster. HMGP is authorized by a Presidential Declaration of Major Disaster. A Governor may request HMGP funding 

be available throughout the State or only in specific jurisdictions. The amount of HMGP funding available to the 

Applicant is based upon the estimated total Federal assistance to be provided by FEMA for disaster recovery under 

the Presidential Declaration of Major Disaster.

The Pre-Disaster Mitigation (PDM) program is authorized by Section 203 of the Stafford Act, 42 U.S.C. 5133. 

The PDM program is designed to assist States, Territories, Indian Tribal governments, and local communities to 

implement a sustained pre-disaster natural hazard mitigation program to reduce overall risk to the population and 

structures from future hazard events, while also reducing reliance on Federal funding from future disasters. PDM 

provides funds on an annual basis. 

The Flood Mitigation Assistance (FMA) program is authorized 

by Section 1366 of the NFIA, 42 U.S.C. 4104c, with the goal of 

reducing or eliminating claims under the NFIP. FMA provides 

funds on an annual basis.

The National Flood Insurance Fund provides the funding for the 

FMA program. The PDM and FMA programs are subject to the 

availability of appropriation funding, as well as any programspecific directive or restriction made with respect to such funds. 

Table 2-1 provides a summary of eligible retrofit activities for each of the three programs in the Unified HMA 

Program. More information about each program can be 

found on the FEMA HMA Web site at https://www.fema.gov/

hazard-mitigation-assistance. 

CROSS REFERENCE

The Repetitive Flood Claims (RFC) 

program and the Severe Repetitive 

Loss (SRL) program have been eliminated and significant changes have 

been made to the FMA program. 

For more information, refer to the 

Unified Hazard Mitigation Assistance 

Guidance. 
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INTRODUCTION TO RETROFITTING 2

Table 2 1. Eligible Retrofit Activities by Program

Elibigle Activities HMGP FMA

Acquisition/Demolition (for purposes of open space) 4 4

Relocation 4 4

Elevation 4 4

Dry Floodproofing (historic residential structures) 4 4

Mitigation Reconstruction 4

Help from Other Federal Agencies

Several Federal agencies offer disaster assistance to communities and citizens. For a complete list of Federal assistance programs for which you are eligible, visit http://www.disasterassistance.gov. 

Small Business Administration (SBA)

SBA provides low interest disaster loans to homeowners, renters, businesses of all sizes, and PNP organizations to 

repair or replace real estate, personal property, machinery and equipment, inventory, and business assets that have 

been damaged or destroyed in a declared disaster. Visit http://www.sba.gov/services/disasterassistance/ for more 

information.

U.S. Department of Housing and Urban Development (HUD)

HUD provides flexible grants to help cities, counties, and States recover from Presidentially Declared Major Disasters, especially in low-income areas, subject to availability of supplemental appropriations. Visit http://www.hud.

gov/ for more information.

U.S. Army Corps of Engineers (USACE)

The USACE has the statutory authority to participate in flood protection projects that may include residential 

retrofitting (including elevating flood-prone homes and acquiring badly damaged flood-prone homes). Contact 

the appropriate USACE Division office for further information. You can find more information and contact information for your USACE Division office at http://www.usace.army.mil. 

Natural Resources Conservation Service (NRCS), U.S. Department of Agriculture (USDA)

The NRCS has the statutory authority to participate in small watershed flood protection projects that may include 

residential retrofitting. Contact your local Conservationist for further information. More information is available 

at http://www.nrcs.usda.gov. 

Other Assistance Programs

Other Federal programs intended to protect and improve the environmental quality of floodplains may offer 

financial assistance. 
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2 INTRODUCTION TO RETROFITTING

2.6.2 Non-Federal Help

Programs Sponsored by State and Local Governments

States, local governments, and flood control and drainage districts sometimes develop financial assistance programs to promote flood hazard retrofitting projects. Ask your local officials whether such a program exists in your 

community.

Voluntary Organizations

After floods and other major disasters, voluntary organizations often offer their services to support the rebuilding 

of homes. Occasionally, materials are donated and volunteers offer to provide labor that could be used to reduce 

the cost of a retrofitting project. Check with local officials, local service organizations, and homes of worship for 

information about such services. Note that you must obtain building permits and comply with all relevant regulations (including Substantial Damage requirements, if they apply), even if you receive assistance from voluntary 

organizations.

Environmental Interest Organizations, Including Land Trusts and Nature Conservancies

Numerous non-government, non-profit, and quasi-public organizations are dedicated to enhancing the environmental benefits of floodplains. Sometimes these organizations provide funds that can be used in the restoration or 

protection of the natural beneficial value of the floodplain.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-1

3.0 An Overview of the 

Retrofitting Methods

This guide describes six retrofitting methods for you to consider as you think about how to protect your home 

from flooding:

Elevation – Raising your home so that the lowest floor or lowest horizontal member is at or above the 

regulated flood level. You can accomplish this in several ways. (Chapter 5)

Relocation – Moving your home to higher ground where it will reduce the exposure to flooding. 

(Chapter 6)

Demolition – Tearing down your damaged home and either rebuilding on the same property or buying 

or building a home elsewhere. (Chapter 6)

Wet Floodproofing – Making portions of your home resistant to flood damage and allowing water to 

enter during flooding. (Chapter 7)

Dry Floodproofing – Sealing your home to prevent floodwaters from entering. (Chapter 7)

Barrier Systems – Building a floodwall or levee around your home to restrain floodwaters. (Chapter 8)

This chapter describes the six methods in detail. Keep in mind that only elevation, relocation, allowable wet 

floodproofing, and demolition can be used to meet the minimum requirements of the NFIP. Barrier systems, dry 

floodproofing, and some wet floodproofing may be used to minimize damages, but are not recognized as meeting 

the minimum requirements of the NFIP. Remember that purchasing flood insurance for your home is important, 

even if you mitigate using one of these methods.

While the aforementioned mitigation methods protect the actual structure, this guide also describes retrofitting 

options for equipment and utilities to consider as you think about how to protect your home from flooding:
3-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

3 AN OVERVIEW OF THE RETROFITTING METHODS

Equipment/Utilities – Equipment/Utilities – Retrofitting existing building equipment and utility systems may involve a combination of elevating and/or protecting in place. (Chapter 9)

For each method, you will find a section that explains how the method works and where it should 

and should not be used, lists its advantages and disadvantages, and provides a relative cost estimate. But first, you 

should be aware of some general cautions about retrofitting.

WARNING

In the areas listed below, the risks to lives and property are usually greater than in other flood-prone 

areas:

• Coastal High Hazard Areas (insurance Zone V, VE, and V1–V30) shown on a FIRM (Figure 2-13)

• Coastal A zones (portion of Zone A seaward of the limit of moderate wave action (LiMWA)) 

• Floodways shown on a FIRM (see Figure 2-13)

• Alluvial fan flood hazard areas (certain Zone AO with depths and velocities) shown on a FIRM

• Areas subject to flash floods

• Areas subject to ice jams

• Areas subject to extremely high-velocity flood flows

Modifying a home to protect it from flood damage in these areas requires extreme care and may also 

require complex, engineered designs. If your home is in one of these areas, relocation or demolition (as 

described later in this chapter and in Chapter 6) may be a more conservative option rather than any of 

the other retrofitting methods discussed in this guide. If you have any doubt about whether your home is 

in an area of unusually severe hazard, consult your local officials.

3.1 Cautions

3.1.1 Substantial Improvement/Substantial Damage

As noted in Chapter 2, your community’s floodplain management ordinance, regulation, or provisions of the building code 

includes restrictions on the types of changes that may be made 

to a home that is being Substantially Improved or that has sustained Substantial Damage. These restrictions prohibit or limit 

the use of some retrofitting measures. Two of the six methods 

described in this guide—dry floodproofing and levees/floodwalls—can reduce future damage but may not be used to bring 

a Substantially Improved or Substantially Damaged home into 

compliance with your community’sfloodplain management ordinance, regulation, or provisions of the building 

code. Instead, in accordance with your community’s requirements, you must do one of the following:

n Move the home out of the regulatory floodplain

n Elevate the home so that its lowest floor is at or above the BFE

n In conjunction with elevation, wet floodproof the areas of the home below the BFE and use them only 

for parking, building access, or storage

NOTE

Substantial Improvement and 

Substantial Damage are defined in 

Section 2.5 and Appendix B.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-3

AN OVERVIEW OF THE RETROFITTING METHODS 3

n Demolish the home and either rebuild or buy a home elsewhere

Additional requirements apply to the use of wet floodproofing. 

These are described later in this chapter and in Chapter 7. 

3.1.2 Basements

Another important floodplain management requirement concerns basements. If your home has a basement below the BFE 

and your local officials determine that it is being Substantially 

Improved or is Substantially Damaged, the basement must be eliminated. You can usually do this by backfilling it with compacted 

soil or other suitable material. For floodplain management purposes, the NFIP regulations define a basement as “any area of the 

building having its floor subgrade on all sides.” Your community’s floodplain management ordinance, regulation, or provisions 

of the building code may include a more restrictive definition 

of basement.

Note that the NFIP definition of “basement” does not include 

what is typically referred to as a “walkout-on-grade” basement, whose floor would be at or above adjacent grade on at 

least one side of the building. Depending on your community’s 

floodplain management ordinance, regulation, or provisions of 

the building code, the requirement to eliminate the basement in 

a Substantially Improved or Substantially Damaged home may not 

apply to a walkout-on-grade basement. Instead, you may be able 

to wet floodproof the area. However, a wet floodproofed walkout-on-grade basement may be used only for parking, building 

access, or storage.

Your local officials can tell you more about these requirements 

and others that may be specified by local building codes and ordinances (see Chapter 4).

3.1.3 Flood Protection Elevation and Risk

When you retrofit your home, one of the most important 

things you will do is choose a level of flood protection. In other words, will you protect your home from the base flood, the 

0.2-percent-annual-chance flood, or some other flood? In some 

instances, this decision will be entirely yours; in others, it will 

depend largely on the regulatory requirements of your community, your State, or both. If your retrofit project is being funded 

through a Federal, State, or local agency, you may also be subject to different regulatory requirements. For the purpose of this 

publication, the flood protection elevation is considered the 

flood protection level you choose for your home. 

DEFINITION

Walkout-on-grade is a term commonly used to describe a basement 

whose floor is at ground level on at 

least one side of a home. The term 

“walkout” is used because most basements of this type have an outside 

door or doors (entry door, garage 

door, or both) at ground level (see figure below). Note that if a basement 

floor is below grade on all sides (a 

basement as defined by the NFIP regulations) the basement may still have 

an outside door, but the door will be 

below ground level and stairs will be 

required for access.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

DEFINITION

Flood protection elevation – The elevation you choose to protect your home against the flood hazard. Although it is feasible for you to have a flood protection elevation less than the DFE, protecting your 

home to at least the DFE is recommended.

Design flood elevation (DFE) – The elevation of the design flood relative to the datum specified on the 

community’s FIRM or flood hazard map. The design flood is the greater of the following two flood events: 

(1) the base flood, affecting those areas identified as special flood hazard areas on the 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. The I-Codes, ASCE 7, and ASCE 24 use the term 

DFE. In many communities, the DFE is identical to the BFE. Communities may designate a design flood 

(or DFE) in order to regulate based on a flood of record, to account for future increases in flood levels 

based on upland development, or to incorporate freeboard.

Base flood elevation (BFE) – The elevation of the base flood relative to the datum specified on a community’s FIRM. The base flood has a 1 percent chance of being equaled or exceeded in any given year. 

BFEs are shown on FIRMs for many SFHAs. Relative to NFIP requirements, the BFE is the minimum 

elevation to which the lowest floor of a building must be elevated or floodproofed (Zone A). In Zone V, the 

bottom of the lowest horizontal structural member must be elevated to or above the BFE; floodproofing 

is not permitted in Zone V. Many SFHAs are shown on FIRMs without BFEs; in these areas, community 

officials and permit applicants are required to obtain and use information from other sources, or must 

estimate or develop BFEs at specific locations.

Freeboard – An added margin of safety, expressed in feet above a specific flood elevation, usually the 

BFE. In States and communities that require freeboard, buildings are required to be elevated or floodproofed to the higher elevation. For example, if a community adopts a 2-foot freeboard, buildings are 

required to be elevated or floodproofed to 2 feet above the BFE.

As you will see in this chapter, different retrofitting methods protect your home in different ways. For example, 

when you elevate your home, you protect it by raising its lowest floor to a specified elevation. When you dry 

floodproof your home, you use sealants, shields and other measures to protect the part of your home below a 

specified elevation by preventing water from entering the building. Because some seepage is anticipated, sump 

pumps are used to control the seepage and flood-damage-resistant materials are used to prevent damage where 

seepage is likely to occur. The home’s structural components must have the capacity to resist increased flood loads 

resulting from dry floodproofing. To wet floodproof, you allow floodwaters to enter your home, but prevent 

damage below a specified elevation by using flood-damage-resistant materials and construction techniques. When 

you protect your home with a levee or floodwall, the top of the levee or floodwall is constructed to a specified 

elevation. To meet the requirements of the NFIP and potentially reduce your flood insurance premium, FEMA 

recommends protecting your home to the DFE. 

If your home is being Substantially Improved or has been Substantially Damaged, your community’s floodplain 

management ordinance, regulation, or provisions of the building code will specify a DFE that is at least equal 

to the BFE (the elevation of the 1-percent-annual-chance flood). Communities may require a higher DFE if they 

wish, or they may be required to do so by State law. Some States and communities require a higher DFE by establishing freeboard requirements, as discussed in Section 3.1.4. Your local officials can advise you about this. 
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AN OVERVIEW OF THE RETROFITTING METHODS 3

On the other hand, if NFIP compliance is not required (the building does not have to meet the requirements of 

Substantial Improvement/Damage), then you may choose to have a flood protection level less than the DFE.

Although you cannot use a flood protection elevation lower than that required by your community, you are probably free to use a higher elevation if you wish to provide a greater level of flood protection. Depending on your 

situation, your choice of flood protection method and optimal elevation will be based largely on the cost to elevate to different elevations, the risk reduction provided by different elevations, and the annual cost of insurance 

premiums at different elevations.

In general, you will find that the cost of retrofitting increases as your flood protection elevation increases. For example, 

protecting your home to the elevation of the 2-percent-annualchance flood with one of the methods described in this guide 

will probably cost you less than protecting it to the BFE with the 

same method (although the additional cost to protect to the BFE 

may be small). Although using a lower flood protection elevation may result in a less expensive retrofitting project, it exposes 

your home to a greater risk of flood damage and higher insurance rates. So in choosing a flood protection elevation, you must 

consider not only how much you are willing to pay, but also the 

level of risk you are willing to accept, including the potential 

for damage, financial loss, and emotional distress. For example, 

recent studies have shown that adding 1 to 3 feet of freeboard 

above the BFE to an elevation project can pay for itself within a 

few years through a 25 to 60 percent annual reduction in flood 

insurance premiums. 

One way to see the relationship between your flood protection 

level and risk is to look at the probabilities associated with floods 

of various magnitudes during a period of 30 years, which is also 

the same length of a standard mortgage (Figure 3-1). The percentages shown along the vertical axis of the graph 

in Figure 3-1 are the probabilities that a flood will be equaled or exceeded during a 30-year period. This probability decreases as the magnitude of the flood increases. So the probability of a flood with an elevation equal to 

or greater than the flood protection elevation you choose decreases as your flood protection elevation increases. 

For example, compare the risks associated with the 2-percent-annual-chance (50-year) flood and the base flood. 

If you choose a flood protection elevation equal to the elevation of the 2-percent-annual-chance (50-year) flood, 

the probability that a flood as high as or higher than your flood protection elevation will occur during a 30-year 

period is 45 percent. But if you choose a flood protection elevation equal to the 1-percent-annual-chance flood 

(100-year flood or base flood), the probability drops to 26 percent. Although the base flood serves as the basis 

for NFIP insurance rates and regulatory floodplain management requirements, the relative frequency of any given 

flood (e.g., 2- year or 10-year) serves as a useful reference point when selecting a retrofitting option, evaluating 

cost effectiveness, and comparing relative risk.

Regardless of the flood protection elevation you choose or are required to use, you must realize that a larger flood 

is always possible and that there will always be some risk of damage. If you don’t have flood insurance, you should 

purchase a policy; if you have flood insurance, you should maintain your policy, even if you have protected your 

home to or above the BFE. Once a home has been retrofitted to meet the NFIP requirements for Substantially Improved structures, it will probably be eligible for a lower flood insurance rate depending on the level of protection 

NOTE

A single-story home that is valued 

at $150,000 and located in Zone AE 

can have differing insurance premiums based on the level of protection. 

If the home is elevated to the BFE 

and does not have an enclosure, the 

annual premium would be approximately $1,294. If the same home is 

elevated to 2 feet above the BFE, the 

annual premium would be approximately $389. The increase in the flood 

protection level would result in a 70 

percent savings in annual insurance 

premiums that would be passed onto 

the homeowner.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

of your flood retrofit. Note that dry floodproofing of residential structures is not permitted to meet NFIP requirements, and is not recognized for flood insurance premium reduction purposes. Also, unless a floodwall or levee is 

accredited, it is not recognized for flood insurance premium reduction purposes.

Figure 3-1. This graph shows 

the relationship between 

flood recurrence intervals 

and the probability of an 

event occurring within a 30-

year period.

3.1.4 Freeboard and Flood Mapping Uncertainties

If you are protecting your home by elevating it, dry floodproofing it, or building a levee or floodwall, you should 

include a minimum of 1 foot of freeboard in your flood protection elevation, even if your community does not 

require you to do so. For example, if you are elevating your home to protect it from the base flood, your flood 

protection elevation should be equal to the BFE plus 1 foot.

Freeboard is recommended because of uncertainties regarding 

expected flood elevations. These uncertainties exist for several 

reasons, but the two primary reasons are limitations of the analytical methods used in floodplain studies and potential effects 

of future watershed development, such as the construction of 

buildings and roads.

FEMA and other agencies that perform floodplain studies use 

a variety of standard engineering methodologies to determine 

flood frequencies and flood elevations. These methods involve the use of historical data, field measurements, 

and assumptions and judgments, all of which can affect the accuracy of the results. Some amount of uncertainty regarding the results is, therefore, unavoidable, and the potential for flood elevations higher than those 

expected should always be accounted for in retrofitting. For example, FEMA’s FIRMs include areas subject to the 

0.2-percent-annual-chance flood (designated on FIRMs as Zone B or shaded Zone X) and areas outside of the 

0.2-percent-annual-chance flood (designated on FIRMs as Zone C or unshaded Zone X). Homes constructed in 

Zones B, C, or X are not considered to have a high risk of flooding by the NFIP, but that does not mean that they 

DEFINITION

The watershed of a stream is the 

geographic area that contributes surface water, from rain or melting snow, 

to that stream. 
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AN OVERVIEW OF THE RETROFITTING METHODS 3

are not subject to flooding. In fact, 25 to 30 percent of all flood insurance claims are for flood damages that occur 

in one of these zones.

Another example of uncertainties in mapping exists in coastal areas. Coastal FIRMs show Coastal High Hazard Areas (designated on FIRMs as Zones V, VE, and V1–V30), which are subject to waves of 3 feet or higher. However, 

historic observations have shown that many coastal homes located outside of Zone V areas still experience significant damage from moderate wave heights of 1.5 to 3 feet. For this reason, FEMA is working to update many 

coastal FIRMs to include SFHAs seaward of the LiMWA, also known as Coastal A Zones. Zone A in coastal areas 

is divided by the LiMWA. The LiMWA represents the landward limit of the 1.5-foot wave. The area between the 

LiMWA and the Zone V limit is known as the Coastal A Zone for building code and standard purposes and as the 

Moderate Wave Action (MoWA) area by FEMA flood maps. Again, this area is subject to wave heights between 1.5 

and 3 feet during the base flood. The area between the LiMWA and the landward limit of Zone A due to coastal 

flooding is known as the Minimal Wave Action (MiWA) area and is subject to wave heights less than 1.5 feet during the base flood. Although not an NFIP requirement, FEMA recommends that homes located in Coastal A Zones 

meet the same requirements as homes constructed in Zone V areas. Figure 3-2 is a typical paper FIRM showing 

the delineations between Zone V, the MoWA area, the LiMWA, Zone A, and the MiWA area. Figure 3-3 is an example of a transect perpendicular to the shoreline showing the delineations between Zone V, the MoWA area, the 

LiMWA, Zone A, and the MiWA area. 

Figure 3-2. Portion of a 

paper FIRM showing coastal 

flood insurance rate zones. 

The icons on the right 

indicate the associated flood 

hazard zones for design 

and construction purposes. 

The LiMWA is not shown on 

older FIRMs, but is shown on 

newer FIRMs.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

Figure 3-3. Typical transect perpendicular to the shoreline showing the delineations between Zone V, the MoWA area, the 

LiMWA, Zone A, and the MiWA area.

Development in a watershed can increase the size and frequency of floods in that watershed. In general, watershed development reduces the amount of open ground available to absorb water from rain and melting snow and, 

therefore, increases the amount of water that makes its way into streams. As a result, in a developing watershed, 

an amount of rainfall that might have caused minor floods in the past may cause larger floods and higher elevations in the future.

FEMA’s floodplain studies are based on the watershed conditions existing at the time the studies are performed. 

They do not account for potential increases in watershed development or any other changes that might affect the 

sizes of future floods. The reason for this approach is that one of the primary purposes of FISs and FIRMs is to provide the technical basis for establishing flood insurance rates. Therefore, the flood hazards must be shown as they 

are, not as they might be. Also, attempting to predict the level of future watershed development in every study and 

determine the effects not only would be extremely difficult but also would require additional assumptions and 

judgments that could increase uncertainty. However, in many watersheds, some amount of development is inevitable. So, providing freeboard is a prudent means of protecting against the increased flood elevations that may result.

3.1.5 Human Intervention

Retrofitting methods fall into two general categories: those that 

depend on human intervention, which are referred to as “active” methods, and those that do not, which are referred to as 

“passive” methods. For example, elevating your home does not 

require human intervention to be effective. But what if you have 

a floodwall with an opening for your car? In addition to requiring interior drainage, a floodwall with an opening will protect 

your home only if you can close the opening before flooding 

occurs. So your floodwall will have to be fitted with a gate (or 

some other type of closure mechanism), and every time flooding threatens, you will have to be warned far enough in advance 

so that you can close the gate in time.

DEFINITION

Human intervention is any action 

that a person must take to enable a 

flood protection measure to function 

as intended. This action must be taken every time flooding threatens.
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AN OVERVIEW OF THE RETROFITTING METHODS 3

The need for adequate warning time and human intervention 

makes active methods less reliable than passive methods. You 

should try to avoid active methods when you choose a retrofitting method for your home, keeping in mind that active 

methods cannot be used to bring a home into compliance with 

the NFIP. If your retrofitting project includes active methods, 

you must have a plan that describes what actions you will take to 

make the measures work and when you will take those actions.

3.1.6 Other Considerations

The retrofitting measures discussed in this guide may be the best means of protection for a home in an area where 

a large flood control project or major waterway improvement, is not feasible, warranted, or appropriate. You 

should keep the following in mind whenever you consider a retrofitting project:

n Communities participating in the NFIP require permits for all development within the regulatory 

floodplain. Under your community’s floodplain ordinance or law, any changes to buildings and other 

structures are considered “development.” These changes include improvements and repairs of existing 

buildings and other structures. Also, communities usually require building permits for many of the 

activities associated with the retrofitting methods described in this guide. In communities that have 

adopted a floodplain ordinance or law, health code, and building code, the permits required by these 

ordinances, laws, and codes may be issued separately or as one combined permit. You may need a permit 

for the following:

o Modifying your existing home or building a new 

home on a flood-prone site. A floodplain permit 

and possibly a building permit will be required.

o Moving a home on public rights-of-way. If you 

relocate your home, you will probably need 

a permit, not only from your community but 

also from your State, as well as from any other 

communities through which the home will pass 

on its way to the new site. A relocation project may 

also require a permit for the foundation at the new 

site.

o Demolishing a damaged home and restoring the 

site after demolition, including grading, planting 

vegetative cover, capping and abandoning utilities, 

and removing or securing underground septic and 

fuel storage tanks.

You may wish to obtain the permits necessary for 

your retrofitting project yourself or arrange for your 

retrofitting contractor or design professional to obtain 

them. But remember, you must have the necessary 

permits in hand before you begin your project. As 

discussed in Chapter 4, your local officials are the best 

source of information about State and local permit 

requirements.

WARNING

Some communities may restrict or 

prohibit the use of active retrofitting 

methods for flood protection.

CROSS REFERENCE

Your design professional or contractor should review some or all of the 

applicable versions of the following nationally recognized codes and 

standards:

• International Code Council, 

International Building Code (IBC)

• International Code Council, 

International Existing Building 

Code (IEBC)

• International Code Council, 

International Residential Code 

(IRC)

• ASCE, Minimum Design 

Loads for Buildings and Other 

Structures (ASCE 7)

• ASCE, Flood Resistant Design 

and Construction (ASCE 24)

• See Appendix A for more 

information.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

n In addition to meeting the requirements of the floodplain management ordinance and building codes, 

you may need to comply with the requirements of other Federal, State, and local laws and ordinances, such as those 

dealing with zoning setbacks and wetlands. Again, your local officials are the best source of information about 

these requirements.

n If your retrofitting project will involve financial assistance from a Federal agency and your property is 50 

years old or older, you must work with that agency to ensure that your project complies with the National Historic 

Preservation Act (16 U.S.C. 470). The act requires that, before releasing any Federal assistance, the agency 

determine whether the property is eligible for inclusion in the National Register of Historic Places and if 

so, whether your project will have any effect on the historic character of the property. This requirement 

may not apply in some emergency situations or if the agency has made prior arrangements with historic 

preservation officials. For more information, contact your SHPO (Appendix E).

n Most retrofitting measures should be designed and constructed by experienced professionals, such as contractors, 

engineers, and architects. Using professionals helps you make sure that the work is done properly, that 

code and regulatory requirements are met, and that, once completed, the retrofitting measures will work.

n Most retrofitting measures cannot be simply installed and forgotten. You will need to periodically inspect 

and maintain them to be sure that they will continue to work over time, especially if they require human 

intervention or depend on certain materials.

n Even though retrofitting will help protect your home from flooding, you should never remain in your home during 

flooding. Stay informed about flooding conditions by monitoring local radio and television stations. Be 

prepared to evacuate when necessary.

n Elevating your home may reduce the cost of your NFIP flood insurance policy. Relocating a home to a 

site outside the regulatory floodplain eliminates the mandatory flood insurance purchase requirement 

and significantly reduces the cost of flood insurance for an owner who wishes to purchase a policy.

3.2 Construction Terminology

In the remainder of this guide, you will find many references to common types of home construction, such as 

frame or masonry, and common types of home foundations, such as slab-on-grade or crawlspace. Even if you are 

already familiar with these and other home construction terms, take a minute to review the following information 

before you move to the descriptions of the retrofitting methods.

3.2.1 Construction Type

The most common home construction types are (Figure 3-4):

Frame – walls constructed of wood or light-gauge metal studs, with wood, vinyl, or aluminum siding 

Masonry veneer – frame walls with a non-structural, decorative, exterior layer of brick, stone, or concrete block 

instead of siding

Masonry – walls constructed of brick, stone, or concrete block

Modular home – frame home assembled on site on a permanent foundation from separate sections manufactured 

elsewhere (subject to local building codes)
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AN OVERVIEW OF THE RETROFITTING METHODS 3

Manufactured home – prefabricated frame home constructed on a transportable frame that can be placed on a 

permanent or temporary foundation (subject to Federal and State standards)

Some homes consist of combinations of two or more of these construction types.

Figure 3-4. Typical cross-sections of three common construction types: frame, masonry veneer, and masonry. The 

foundation shown here for all three construction types consists of concrete blocks and a concrete footing. The same 

construction types are also found on basement and slab-on-grade foundations.

3.2.2 Foundation Type

Most homes of the construction types listed above are built on 

the following types of foundations (Figure 3-5):

Basement – with masonry or cast-in-place concrete walls

Crawlspace – with masonry or cast-in-place concrete walls

Slab-on-grade – either a slab with a masonry or concrete foundation or a thickened slab (see Figure 5-5 in Chapter 5)

Open foundation – usually concrete or masonry piers, but 

sometimes wood, concrete, or metal posts, columns, or piles

Some homes are built on more than one type of foundation. Various combinations of basement, crawlspace, and slab-on-grade 

foundations are common. Manufactured homes are occasionally 

installed on basement or crawlspace foundations but are more 

often supported either by stacks of concrete blocks or by foundation systems designed specifically for manufactured homes.

DEFINITION

Concrete poured into forms at the 

construction site is referred to as 

cast-in-place concrete.

WARNING

The relative costs in this chapter are 

provided only as examples of what to 

expect when choosing a retrofitting 

method. Be sure to get a complete, 

written cost estimate from your contractor and design professional before 

you begin any retrofitting project (see 

Chapter 4).
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Figure 3-5. Home foundation types.

3.3 Retrofitting Methods and Costs

The following sections give an overview of the six retrofitting 

methods, explain how they work and where they are appropriate, and list their advantages and disadvantages. With this 

information, you will be ready for Chapter 4, Deciding Which Method Is Right for Your Home.

3.3.1 Elevation 

Elevating a home to prevent floodwaters from reaching living areas is an effective retrofitting method. 

The goal of the elevation process is to raise the lowest 

floor to or above the DFE. You can do this by elevating 

the entire home, including the floor, or by leaving the home in 

its existing position and constructing a new raised floor within the home. The method used depends largely on construction 

type, foundation type, and flooding conditions. Chapter 5 presents more detailed information on elevation.

During the elevation process, most homes (including manufactured homes) are separated from their foundations, raised on 

hydraulic jacks, and held by temporary supports while a new or 

extended foundation is constructed below. This method works 

well for homes originally built on basement, crawlspace, and 

open foundations. As explained later in this section, the new or 

extended foundation can consist of continuous walls or separate 

piers, posts, columns, or piles.

CROSS REFERENCE

FEMA P-550, Recommended 

Residential Construction for Coastal 

Areas: Building on Strong and Safe 

Foundations (FEMA. 2009), offers 

more detail about these foundation 

types and elevation.

NOTE

When you elevate your home, the 

existing foundation will need to be extended or demolished and rebuilt. This 

decision will depend on the condition 

of the existing foundation and its ability to carry additional loads.
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AN OVERVIEW OF THE RETROFITTING METHODS 3

For homes with slab-on-grade foundations, elevation can be 

done in one of two ways. One approach is to leave the home 

attached to the slab foundation and lift both together. After the 

home and slab are lifted, a new foundation is constructed below 

the slab. The other approach is to detach the home from the slab 

and elevate the home, leaving the slab foundation in place. After 

the home is lifted, a new, elevated floor is constructed.

Unlike other types of construction in which elevation can be 

relatively straightforward, elevating slab-on-grade homes with 

the slab intact is technically challenging and often not feasible. 

When a slab-on-grade home is elevated with the slab intact, the 

slab, which was previously continuously supported by the soils 

beneath it, must function as a structural element. It must span 

the distance between the portions of the foundation that support the elevated home. Typically, these slabs often are either 

unreinforced or only lightly reinforced with welded wire fabric 

and are essentially non-structural. These slabs may not be able 

to support the loads of an elevated home. Consequently, the slab 

foundation should be thoroughly evaluated by a registered design professional before choosing this mitigation option. 

Alternative techniques are available for masonry homes on slabon-grade foundations. As described later in this section, these 

techniques do not require the lifting of the home. Instead, they 

involve raising the floor within the home or moving the living 

space to an upper story. Guidance for elevating slab-on-grade 

masonry homes can be found in FEMA P-347, Above the Flood: Elevating Your Floodprone House (FEMA. 2000).

Although elevating a home can help protect it from floodwaters, 

you need to consider other hazards before choosing this method. Elevating the home can make it more susceptible to damage 

from earthquakes. In addition, both continuous wall foundations and open foundations can fail as a result of damage caused 

by erosion and the impact of debris carried by floodwaters. If 

portions of the original foundation, such as the footings, are 

used to support new walls or other foundation members, or a 

new second story, they must be capable of safely carrying the 

additional loads imposed by the new construction and the expected flood, wind, and earthquake forces.

Method #1: Elevating on Continuous Foundation Walls

Although this method is usually used in flood hazard areas 

where the risks of wave action and high-velocity flow are low 

(Figures 3-6 and 3-7), continuous foundation walls in low-velocity flow areas with wave action can also be susceptible to structural damage. Open foundations should be considered as a reasonable mitigation option. After 

the home is detached from its foundation and raised on jacks, the existing foundation is often saved and the 

DEFINITION

A footing is the base of a foundation. 

Footings are usually made of concrete and may be reinforced with steel 

bars. Foundation walls are supported on continuous footings; separate 

foundation members, such as piers, 

are supported on individual footings. 

CROSS REFERENCE

FEMA has produced a videotape 

titled Best Build 3: Protecting a 

Flood-Prone Home, which illustrates 

the retrofitting methods described in 

this guide (see Appendix A).

NOTE

Elevation on open foundations is required by the NFIP in Zone V areas 

(even when the ground elevation lies 

above the BFE) and is strongly recommended for Coastal A Zones. 

Some States and communities have 

formally adopted open foundation 

requirements for Coastal A Zone 

construction. 
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foundation walls are extended. The new portions of the walls are usually made of masonry block or cast-in-place 

concrete. Although this method may be the easiest way to elevate a home, it can involve some additional construction modifications or reinforcements. 

Figure 3-6. Typical crosssection of home elevated on 

continuous foundation walls.

Figure 3-7. Before (left) and after (right) photos of a retrofitted home elevated on extended continuous foundation walls.

Depending on the size of your home, the amount of elevation, and the magnitude of the potential environmental 

loads (such as those from floods, wind, earthquakes, and snow), your contractor may have to modify or reinforce 

the footings and foundation walls to ensure the structural stability of the home. The original footings may have to 

be replaced with ones that have a higher capacity for environmental loads. Both the footings and the foundation 

walls may need to be reinforced with steel bars.

This type of foundation creates what is referred to under the NFIP as an “enclosure.” The enclosure must be constructed of flood damage-resistant materials, have all service equipment elevated above the DFE, and be used only 

for parking, access, or storage. NFIP Technical Bulletin 2, Flood Damage-Resistant Materials Requirements (FEMA. 2008), 

defines a “flood [damage]-resistant material” as “any building product [material, component, or system] capable of withstanding direct and prolonged contact with floodwaters without sustaining significant damage.” 
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AN OVERVIEW OF THE RETROFITTING METHODS 3

“Prolonged contact” means at least 72 hours, and “significant damage” means any damage requiring more than 

cosmetic repair. Technical Bulletin 2 provides a detailed list of appropriate flood damage-resistant materials and 

also classifies flood damage-resistance of materials as acceptable or unacceptable based on water resistance and 

ability to be cleaned. 

The enclosure must also be constructed with openings to allow equalization of hydrostatic pressure to comply 

with NFIP and building code requirements. As explained in Chapter 2, unequalized hydrostatic pressure exerted 

by floodwaters can collapse walls, regardless of the construction materials used. The NFIP may require that openings be installed in the foundation walls so that water can flow into and out of any enclosed area below the newly 

elevated home. NFIP Technical Bulletin 1, Openings in Foundation Walls and Walls of Enclosures (FEMA. 2008), provides 

guidance on the NFIP regulations concerning openings in foundation walls. When the water levels on both sides 

of the foundation walls are the same, the hydrostatic pressure is equalized. If you are elevating your home as part 

of a Substantial Improvement or in connection with repairs of Substantial Damage, your community’s floodplain 

management ordinance, regulation, or provisions of the building code will require that you install openings in all 

areas below the BFE. Consult your local officials about local requirements for openings.

Method #2: Elevating on Open Foundations

Unlike continuous foundations, open foundations consist of individual vertical structural members that support 

the home only at key points. Because they present less of an obstacle to flood flows than continuous walls, open 

foundations can be used in areas where there are risks of wave action and high-velocity flood. Most open foundations consist of piers, posts, columns, or piles. 

Piers. Piers (or columns) are commonly built with 

masonry block or are made of cast-in-place concrete 

(Figure 3-8). Piers can be made from wood and steel as 

well. The bottom of each pier sits on a concrete footing. 

Pier foundations are used in conventional construction; 

they are not just a means of elevating a flood-prone 

home. In conventional use, they are designed primarily 

for vertical loading—to hold the weight of the home. 

They are not normally designed to resist large horizontal 

forces, such as those associated with moving floodwaters, waves, impacts from floodborne debris, wind, and 

earthquakes. As a result, pier foundations are generally 

used where the risks of wave action and high-velocity 

flow are low to moderate and the potential for earthquakes is low.

If you decide to elevate your home on a pier foundation, 

you should expect your contractor to reinforce the piers 

and footings with steel reinforcing bars and to connect 

the piers to the footings so they will not separate under 

flood or other forces. Adequate connections between the 

piers and the home are also necessary so that the home 

and foundation will resist lateral loads from floods, 

winds, and earthquakes, and uplift from buoyancy.

Figure 3-8. Home elevated on reinforced concrete piers.
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Posts. Posts are usually made of wood or steel (Figure 

3-9). They are generally square but may also be round. 

Posts are set in holes, and their ends are encased in concrete, or supported on concrete pads (as in the figure). 

After posts are set, the holes are filled with concrete, dirt, 

gravel, or crushed stone. 

Posts can be connected to each other with bracing made 

of wood, steel rods, or guy wires. The type is usually determined by cost, flood conditions, expected loads, the 

availability of materials, and local construction practice. 

Like piers, posts are generally used where the risks of 

wave action and high-velocity flow are low to moderate.

One primary difference between piers, and posts is the 

dimension of the element – piers are larger in cross section because they usually are CMU (concrete masonry 

unit) or concrete block and are usually shorter than 

posts. Posts are braced together because they are usually taller and more slender with less stability than piers. 

Piles. Piles are usually made of wood, but fiber-reinforced polymer, steel, or precast concrete piles are also common in some 

areas (Figure 3-10). Piles are similar to posts but, instead of being set in holes, they are driven into the ground or jetted in with 

streams of water. Also, piles are embedded deeper in the ground 

than either piers or posts. As a result, pile foundations are less 

susceptible to the effects of high-velocity flow, waves, debris 

impact, erosion, and scour than the other types of open foundations. Piles differ from piers and posts also in that they do not 

rest on footings. Instead they are driven until they rest on a solid 

support layer, such as bedrock, or until they are embedded deep 

enough that the friction between the ground and the piles will 

enable them to resist the loads that are expected to act on them.

Because driving and jetting piles requires bulky, heavy construction machinery, an existing home must normally be moved off 

its existing foundation and set on cribbing until the operation 

is complete. As a result, elevating a home by placing it on a pile 

foundation will usually require more space and cost more than 

elevating with another type of foundation. Pile foundations are used primarily in areas where other elevation 

methods are not feasible, such as where floodwaters are deep and the risks of wave action and high-velocity flow 

are great. For example, pile foundations are used extensively in oceanfront areas exposed to high-velocity flow, 

waves, and high winds (Figure 3-11).

Figure 3-9. Home elevated on posts

DEFINITION

Concrete materials such as posts, 

beams, and blocks that are brought to 

the construction site in finished form 

are referred to as precast. 

Jetting is a process in which the hole 

for the installation of a pile is made by 

a high-pressure stream of water from 

a nozzle attached to the bottom of the 

pile.

Cribbing usually consists of a framework of crisscrossed timbers that 

provides temporary structural support.
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AN OVERVIEW OF THE RETROFITTING METHODS 3

Figure 3-10. Home elevated on piles. 

Figure 3-11. Example of 

well-elevated and embedded 

pile foundation tested by 

Hurricane Katrina. Note 

adjacent building failures 

(Dauphin Island, AL, 2005).
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3 AN OVERVIEW OF THE RETROFITTING METHODS

Methods #3 and #4: Elevating by Extending the Walls of the Home or Moving the Living Space to 

an Upper Floor

For masonry homes on slab-on-grade foundations, two alternative elevation methods are available. One is to remove the roof, 

extend the walls of the home upward, replace the roof, and 

build a new, raised floor at the DFE (Figure 3-12). This technique works best where the floor needs to be raised less than 

4 feet to reach the DFE. The floor can be either a new slab or a 

new wood-framed floor. For a new slab, fill dirt is placed on top 

of the old slab and the new slab is built on top. If a new woodframed floor is built, the space between it and the old slab is left 

open and becomes a crawlspace (and must be retrofitted with 

openings to allow floodwaters in the crawlspace).

CROSS REFERENCE

As discussed in Section 2.6, the cost 

of elevating a Substantially Damaged 

home may be eligible for a flood insurance claim under ICC coverage.

Figure 3-12. The owner of 

this flood-prone home in 

south Florida decided to build 

a new wood-framed second 

story on top of the masonry 

first story. The new second 

story is well above the BFE.

The second technique is to abandon the entire lower floor, or lower enclosed area, of the home and move the 

living space to an existing or newly constructed upper story. This technique works best for multi-story homes 

where the DFE is more than 4 feet above the level of the lower floor. The abandoned lower floor or enclosed area 

is then used only for parking, building access, or storage.

These techniques, like the others, have their limitations. The portions of the home below the DFE will be exposed 

to flooding and must, therefore, be made of flood damage-resistant materials. That is why this method is applicable to masonry homes rather than frame homes, which would be much more easily damaged by flooding. The 

area below the DFE cannot be used for living space; it may be used only for parking, building access, or storage. In 

addition, all appliances and utilities must be moved to the upper floor. Also, openings must be cut into the walls 

of the lower floor to allow water to enter during flooding so that the hydrostatic pressure on the walls will be 

equalized. In essence, the lower floor is wet floodproofed (see Section 3.4.1). 

Adding a new second story to a single-story home may require that the foundation be strengthened so that it can 

support the additional load. You must consult an engineer if you plan to use this method. The second story can be 

frame or masonry (to match the lower floor). The method you choose will depend on the advice of your engineer, 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-19

AN OVERVIEW OF THE RETROFITTING METHODS 3

cost, appearance, the availability of materials and experienced contractors, and the risks of other natural hazards 

such as hurricanes and earthquakes.

Table 3-1 presents the advantages and disadvantages of elevation. 

The relative costs shown in Table 3-2 are for elevating frame, masonry veneer, and masonry homes of various 

foundation types. The costs for extending utilities and adding or extending staircases are included. The costs 

shown for elevating frame, masonry veneer, and masonry homes on existing slab-on-grade foundations are based 

on the assumption that the home is raised with the existing slab attached.

Table 3-1. Advantages and Disadvantages of Elevation

Advantages Disadvantages

• Brings a Substantially Damaged or Improved building 

into compliance with the NFIP if the lowest horizontal 

structural member of the lowest floor is elevated to the 

BFE

• Reduces flood risk to the structure and its contents

• Eliminates the need to relocate vulnerable items 

above the flood level during flooding

• Often reduces flood insurance premiums

• Uses established techniques

• Can be initiated quickly because qualified contractors 

are often readily available (unless project is implemented immediately after a disaster)

• Reduces the physical, financial, and emotional strains 

that accompany flood events

• Does not require the additional land that may be 

needed for floodwalls or levees

• May be cost-prohibitive

• May adversely affect the structure’s appearance

• May adversely affect access to the structure

• Cannot be used in areas with high-velocity water flow, 

fast-moving ice or debris flow, or erosion, unless special measures are taken

• May require additional costs to bring the structure up 

to current building codes for plumbing, electrical, and 

energy systems

• Requires consideration of forces from wind and seismic hazards and possible changes to building design

NFIP = National Flood Insurance Program; BFE = base flood elevation
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3 AN OVERVIEW OF THE RETROFITTING METHODS

Table 3-2. Relative Costs of Elevating a Home

Construction Type Existing Foundation Retrofit Relative Cost

Frame

Basement, crawlspace, 

or open foundation

Elevate on continuous foundation walls or 

open foundation Lowest 

Highest

Frame with masonry veneer Elevate on continuous foundation walls or 

open foundation

Load bearing masonry Extend existing walls and create new 

elevated living area

Frame

Slab-on-grade

Elevate on continuous foundation walls or 

open foundation

Frame with masonry veneer Elevate on continuous foundation walls or 

open foundation

Load bearing masonry Elevate on continuous foundation walls or 

open foundation

Occasionally, slab-on-grade homes are raised without the slab. 

Although this method can be less expensive than raising the 

home with the slab, it involves detaching the home from the 

slab and requires extensive alterations to interior and exterior 

walls. 

The cost of abandoning an existing lower level will depend on 

whether the home already has an upper level that can be used 

for living space. If an upper level is available, abandoning the 

lower floor would involve primarily elevating or relocating utilities, adding openings in the lower-level walls, and ensuring 

that all construction materials below the BFE are flood damage 

resistant. This method is well-suited to a home with a walkouton-grade basement, which can be wet floodproofed and used 

for parking, building access, or storage. The cost of adding a 

new frame upper level and raising the roof to accommodate the 

new level would vary, depending upon the amount of interior 

finishing and other factors. 

3.3.2 Relocation and Demolition

Relocation is the retrofitting measure that can offer the greatest security from future flooding. It involves moving an entire structure to another location, usually outside the floodplain. Relocation as a retrofitting measure not 

only relieves anxiety about future flooding, but also offers the opportunity to reduce future flood insurance premiums. Demolition is tearing down a damaged home. A new compliant home can be rebuilt on site, rebuilt on 

another property, or the owner can simply move in to another structure elsewhere. These retrofitting methods are 

discussed below.

DEFINITION

The footprint of a house is the land 

area it covers (see figure). This area 

is equal to the length of the house 

multiplied by its width. Note that the 

footprint is not necessarily equal to 

the total square footage of the house.
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AN OVERVIEW OF THE RETROFITTING METHODS 3

Relocation

Moving your home to high ground, outside the flood hazard area, is the most effective of the retrofitting methods described in this guide. Retrofitting literature commonly refers to this method as 

relocation. Chapter 6 presents more detailed information on relocation. When there is enough space 

and the ground is high enough, you may even be able to move your home to another location on the 

same piece of property.

Relocating a home involves detaching it from the foundation, raising it with jacks, and placing it on a wheeled 

vehicle that delivers it to the new site. The original foundation is demolished and a new foundation is built at the 

new site. The home is installed on the new foundation and all utility lines are connected. Relocation is particularly 

appropriate in areas where the flood hazard is severe, such as where flood conditions are characterized by one or 

more of the following:

n Deep water

n Rapid rates of rise and fall

n Short warning time

n Wave action

n High-velocity flow

n High debris potential

n Long duration

n Erosion

Relocation is also appropriate for homeowners who want to be free of worries about damage from future floods 

that may exceed a selected flood protection elevation.

Although similar to elevation, relocation requires additional steps that usually make it more expensive. These include moving the home, buying and preparing a new site (including building the new foundation and providing 

the necessary utilities), and restoring the old site (including demolishing the old foundation and capping and 

abandoning old utility lines).

Homes of all sizes and types can be relocated, either as a unit or in segments. One-story frame homes are usually 

the easiest to move, particularly if they are built on a crawlspace or basement foundation that provides easy access 

to the floor framing. Masonry homes can also be moved, but usually with more difficulty and at a higher cost.

Professional home movers can advise you about the things you need to consider when deciding whether to relocate. The structural integrity of your home will have to be checked. Also, you may need to find a place where 

you can store furniture and other belongings temporarily. However, in most instances, the contents of your home 

may remain in the home while it is being moved. Keep in mind that there must be a clear route to the new site. 

Narrow roads, restrictive overpasses, and bridges with low weight limits may make it impossible for your home 

to be moved to the new site. Also, many States and communities have requirements that govern the transport of 

homes and other buildings on public rights-of-way. For information about structural movers in your area, visit 

http://www.iasm.org. Table 3-3 presents the advantages and disadvantages of relocation.
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Table 3-3. Advantages and Disadvantages of Relocation

Advantages Disadvantages

• Allows Substantially Damaged or Improved structure 

to be brought into compliance with the NFIP

• Significantly reduces flood risk to the structure and its 

contents

• Uses established techniques

• Can be initiated quickly because qualified contractors 

are often readily available (unless project is implemented immediately after a disaster) 

• Can eliminate the need to purchase flood insurance or 

reduce the premium because the home is no longer in 

the floodplain

• Reduces the physical, financial, and emotional strains 

that accompany flood events

• May be cost-prohibitive

• Requires locating a new site 

• Requires addressing disposition of the flood-prone 

site

• May require additional costs to bring the structure up 

to current building codes for plumbing, electrical, and 

energy systems

• May take a long time, depending on time required to 

find desired property, purchase it, and develop it with 

desired utilities

• May be cost-prohibitive to relocate, as well as to develop the site with desired utilities (water, sewage, 

electrical, natural gas, cable, telephone etc.)

NFIP = National Flood Insurance Program

Table 3-4 shows the relative costs of relocating homes of different construction and foundation types. In addition to moving 

and construction costs, it is important to account for the additional relocation project costs of any new property that must be 

purchased. 

Table 3-4. Relative Costs of Relocation

Construction Type Existing Foundation Retrofit Relative Cost

Frame

Crawlspace, or open 

foundation

Relocate existing home and install the 

home on a new foundation at the new 

site, hook up utilities, and restore the old 

site

Lowest 

Highest

Frame with masonry veneer

Load bearing masonry

Frame

Frame with masonry veneer Basement

Load bearing masonry

Frame

Frame with masonry veneer Slab-on-grade

Load bearing masonry

WARNING

The relative relocation costs shown 

here are based on a small home. 

Because relocation costs do not increase proportionally with the size of 

a home, the cost per square foot of 

moving a larger home may be less 

than that shown here.
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AN OVERVIEW OF THE RETROFITTING METHODS 3

Demolition

Demolition is tearing down a damaged home. A new compliant home can be rebuilt on site, rebuilt 

on another property, or the owner can simply move in to another structure elsewhere. This retrofitting 

method may be the most practical of all those described in this guide when a home has sustained extensive damage, especially severe structural damage. Chapter 6 presents more detailed information on 

demolition.

Whether you intend to rebuild or move, you must tear down 

your damaged home and then restore the site. Site restoration 

usually involves filling in a basement, grading, and landscaping. As a result, you will need the services of a demolition 

contractor. The contractor will disconnect and cap all utility 

lines at the site and then raze the home with a bulldozer or 

other heavy equipment. If you decide to rebuild on the old 

site or somewhere else on the same property, your construction contractor may be able to do the demolition and site 

restoration work as part of the home construction.

Remember, all demolition, construction, and site restoration work must be done according to the regulatory requirements of your community. Permits may be required for all or part of this work. If you decide to rebuild on 

the site of your old home, you must rebuild in compliance with your community’s floodplain management ordinance or law and other ordinances and codes, which means ensuring that the lowest floor of your new home 

is at or above the DFE. You can do this by elevating your new home on an extended foundation as described in 

Section 3.3.1 or on compacted fill dirt if your property is located in Zone A. If your property is located in Zone V 

area, you must elevate your home on piles or columns. A better approach is to build your home on an alternative 

building site outside the regulatory floodplain, where you can use standard construction practices, including the 

construction of a basement. Remember, if you rebuild on the same site, within the regulatory floodplain, your 

community’s floodplain management ordinance, regulation, or provisions of the building code will not allow 

your new home to have a basement (as defined by the NFIP regulations) if it is located below the DFE. Figure 3-13 

shows a home damaged by Hurricane Irene that is slated for demolition. 

Figure 3 13. Many homes in 

the Town of Prattsville, NY, 

were slated for demolition 

during the recovery effort 

following Hurricane Irene.

CROSS REFERENCE

As discussed in Section 2.6, the 

cost of demolishing a Substantially 

Damaged home may be an eligible flood insurance claim under ICC 

coverage.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

The advantages and disadvantages of demolition vary depending on which of the following three options you choose:

1. Rebuilding on the existing site

2. Rebuilding on an alternative site on a different part of 

your property, which may be outside the regulatory 

floodplain

3. Moving to a home on another property, which may be 

outside the regulatory floodplain

The advantages and disadvantages of option 1 are similar to those listed in Table 3-1 for the elevation method. 

The advantages and disadvantages of options 2 and 3 are the same as those listed in Table 3-3 for the relocation 

method, with the following exceptions: If you choose option 2, you will avoid the need to buy another lot and 

dispose of your existing property.

If you decide to demolish your damaged home and rebuild somewhere on your existing property (option 1 or 

2 above), your costs will include tearing down the damaged home, building the new home to the community’s 

specified elevation, reconnecting utility lines, and restoring the site around the new home. If you decide to move 

to a home outside the regulatory floodplain (option 3), your costs will include tearing down the damaged home, 

buying or building a home elsewhere, capping and abandoning the old utility lines, and restoring the old site.

The cost of tearing a home down, which is not a complex or difficult job, will be almost entirely for the disposal 

of the resulting debris. This cost can vary widely, depending on the amount of debris and whether a dumping fee 

is required at the disposal site. The major costs associated with the demolition method will be for building or buying a home and will, therefore, depend on how and where you build or on the type of home you buy. Be sure to 

get a complete cost estimate before you begin a demolition project. Table 3-5 shows approximate costs for tearing 

down your home and rebuilding on the same site.

Table 3-5. Relative Costs of Demolition and Rebuilding

Construction Type Proposed Foundation Type Relative Cost

Frame

Closed Foundation Lowest

Highest

Open Foundation

Frame with Masonry Veneer

Closed Foundation

Open Foundation

Load bearing masonry

Closed Foundation

Open Foundation

CROSS REFERENCE

See Section 7.1.7 for a discussion of 

flood damage-resistant materials.
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AN OVERVIEW OF THE RETROFITTING METHODS 3

3.4 Floodproofing

Wet floodproofing allows floodwaters to enter your home while using various techniques to minimize flood damage and protect critical systems and contents. Wet floodproofing techniques include raising utilities and important 

contents to or above the flood protection level, installing and configuring electrical and mechanical systems to 

minimize disruptions and facilitate repairs, installing flood openings or other methods to equalize the hydrostatic 

pressure exerted by floodwaters, and installing pumps to gradually remove floodwater from basement areas after 

the flood. 

The purpose of dry floodproofing your home is to make it watertight (substantially impermeable) to floods of 

limited duration (a few hours) and depth (typically less than 2-3 feet). Dry floodproofing reduces the potential 

for flood damage by reducing the probability that your home’s interior will be inundated. It can be an appropriate 

alternative for flood mitigation when relocating or elevating buildings is not cost effective or technically feasible.

3.4.1 Wet Floodproofing

Wet floodproofing a home is modifying the uninhabited portions of the home (such as a crawlspace, 

basement, or other enclosure) so that floodwaters will enter but not cause significant damage to either the home or its contents. The purpose of allowing water into portions of the home is to ensure 

that the interior and exterior hydrostatic pressures will be equal. Allowing these pressures to equalize 

greatly reduces the likelihood of wall failures and structural damage. Wet floodproofing may be used when other 

retrofitting methods are either too costly or are not feasible. If you intend to wet floodproof your basement, a 

licensed engineer or design professional is needed to determine the structural integrity of the walls. Wet floodproofing is practical in only a limited number of situations. Chapter 7 presents more detailed information on wet 

floodproofing.

Because wet floodproofing allows floodwaters to enter the 

home, all construction and finishing materials below the DFE 

should be resistant to flood damage. For this reason, wet floodproofing is practical only for portions of a home that are not 

used for living space, such as a basement as defined by the NFIP 

regulations, an enclosure such as a walkout-on-grade basement 

or a crawlspace, or an attached garage. Figure 3-14 illustrates a 

home with a wet floodproofed subgrade basement. Wet floodproofing this home protects it from hydrostatic pressure, but 

not hydrodynamic pressure and floodborne debris. To minimize 

damages, service equipment must be elevated above the flood 

level and the walls of the basement must be built with flood 

damage-resistant materials. 

Figure 3-15 illustrates a home in which the lower level was 

modified to create an enclosure that is built with flood damageresistant materials, service equipment was elevated above the 

flood level, and the lower level is used solely for parking, access, 

and storage. As illustrated in Figure 3-15, openings must be 

placed in the walls to relieve hydrostatic pressure. If the lowest 

elevated floor is above the community’s DFE and the enclosure 

is protected as described above, the home would meet the minimum requirements of the NFIP. 

WARNING

Wet floodproofing mitigation methods 

can lead to NFIP compliance only if 

the area is limited to parking, access, 

or storage; designed to allow for automatic entry and exit of flood waters; 

and uses only flood damage-resistant materials below the DFE. If your 

home is being Substantially Improved 

or has been Substantially Damaged, 

your community’s floodplain management ordinance or law will restrict 

your use of wet floodproofing to attached garages and enclosed areas 

below the BFE that are used solely for 

parking, building access, or storage. 

For more information, consult your 

local officials. Note that basements 

(any area of the building having its 

floor subgrade on all sides) cannot 

be wet floodproofed to meet NFIP 

requirements.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

Wet floodproofing would not be practical for most slab-on-grade homes in which the living space is at or very 

near the ground level. Whether or not wet floodproofing is appropriate for your home will depend on the flood 

conditions, the flood protection elevation you have selected, the design and construction of your home, and 

whether you are required to bring your home into compliance because it is being Substantially Improved or has 

been Substantially Damaged.

Figure 3-14. A home with a 

wet floodproofed subgrade 

basement. Note: Wet 

floodproofing a basement is 

not permitted to achieve NFIP 

compliance. If Substantial 

Improvement or Substantial 

Damage requirements are 

triggered, the basement 

would need to be filled.

WARNING

After floodwaters recede from around a home with a wet floodproofed basement, you will need to pump out the water that 

filled the basement during the flood. However, you must take 

certain precautions before you pump out the water. If the soil 

surrounding the basement walls and below the basement 

floor is still saturated with water, removing the water in the 

basement too quickly can be dangerous. As the water level in 

the basement drops, the outside pressure on the basement 

walls and floor becomes greater than the inside pressure (see 

figure). As a result, the walls can collapse and the floor can be 

pushed up or cracked (see Section 2.3.1). If you are unsure 

whether pumping out your basement is safe, contact a licensed dewatering contractor. Note that basements (any area 

of the building having its floor subgrade on all sides) cannot 

be wet floodproofed to meet NFIP requirements.
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AN OVERVIEW OF THE RETROFITTING METHODS 3

Figure 3-15. A home with a 

wet floodproofed enclosure. 

Note: Interior grade must be 

at or above the exterior grade 

along the entire length of the 

lowest side to prevent being a 

basement.

If you are considering wet floodproofing, keep the following in mind:

n Your home should have space above the DFE in which you can temporarily or permanently store items 

that could be damaged by floodwaters.

n If your furnace, water heater, or other service equipment is below the DFE, it should be protected as well. 

You may be able to move the equipment to another floor, elevate it, or protect it in place (see Chapter 9).

n Any construction and finishing materials below the DFE that are not flood damage-resistant should be 

removed or replaced with materials that are flood damage-resistant.

n If a flood occurs, you will not be able to live in your home as long as floodwaters remain.

n Wet floodproofing does not alleviate the threat of damage from high-velocity flood flow and wave action.

n Your community’s floodplain management ordinance, regulation, or provisions of the building code 

will not allow you to wet floodproof your basement as defined under the NFIP if your home has been 

Substantially Damaged or is being Substantially Improved.
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Table 3-6. Advantages and Disadvantages of Wet Floodproofing

Advantages Disadvantages

• Reduces the risk of flood damage to a building and its 

contents, even with minor mitigation

• Greatly reduces loads on walls and floors due to 

equalized hydrostatic pressure

• May be eligible for flood insurance coverage of cost of 

relocating or storing contents, except basement contents, after a flood warning is issued 

• Costs less than other measures

• Does not require extra land

• Reduces the physical, financial, and emotional strains 

that accompany flood events

• Does not satisfy the NFIP requirement for bringing 

Substantially Damaged or Improved structures into 

compliance

• Usually requires a flood warning to prepare the building and contents for flooding

• Requires human intervention to evacuate contents 

from the flood-prone area

• Results in a structure that is wet on the inside and 

possibly contaminated by sewage, chemicals, and 

other materials borne by floodwaters and may require 

extensive cleanup 

• Does not eliminate the need to evacuate during floods

• May make the structure uninhabitable for some period 

after flooding

• Limits the use of the floodable area

• May require ongoing maintenance

• May require additional costs to bring the structure up 

to current building codes for plumbing, electrical, and 

energy systems

• Requires care when pumping out basements to avoid 

foundation wall collapse

NFIP = National Flood Insurance Program

Wet floodproofing is generally less expensive than the 

other flood protection methods described in this guide. Table 

3-7 shows the relative approximate costs of wet floodproofing 

homes on basement and crawlspace foundations to heights between 2 feet and 8 feet. In a home with a basement, this height is 

measured from the basement floor. In a home with a crawlspace, 

this height is measured from the lowest adjacent grade to the 

home. The relative costs include those for adding wall openings for the entry and exit of floodwaters, installing pumps, 

rearranging or relocating utility systems, moving large appliances, and making it easier to clean up after floodwaters recede. The relative costs shown for basements in Table 3-7 are valid only for unfinished basements. 

Wet floodproofing a finished basement would involve the removal of all non-flood damage-resistant materials and replacing finish materials with flood damage-resistant materials. As a result, wet floodproofing costs for 

finished basements would be higher and would vary, depending on the amount of finish material to be removed 

or replaced. 

DEFINITION

The lowest adjacent grade is the 

lowest ground surface that touches 

any of the exterior walls of your home.
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AN OVERVIEW OF THE RETROFITTING METHODS 3

Table 3-7. Relative Costs of Wet Floodproofing

Construction Type Existing Foundation Retrofit Relative Cost

Frame, frame with 

masonry veneer, or load 

bearing masonry

Crawlspace Wet floodproof crawlspace to a height of 2 ft 

to 4 ft above LAG*

Lowest 

Highest

Basement Wet floodproof unfinished basement to a 

height of 2 ft to 4 ft above the basement floor

Basement Wet floodproof unfinished basement to a 

height of 8 ft above the basement floor

* LAG – Lowest Adjacent Grade

3.4.2 Dry Floodproofing

In some situations, a home can be made watertight 

below the DFE, so that floodwaters cannot enter. This 

method is called “dry floodproofing.” Section 7.2 

presents more detailed information on dry floodproofing. Making the home watertight requires sealing the walls 

with waterproof coatings, impermeable membranes, or supplemental layers of masonry or concrete. Also, doors, windows, and 

other openings below the DFE must be equipped with permanent or removable shields, and backflow valves must be installed 

in sewer lines and drains. 

The flood characteristics that determine whether dry floodproofing is effective are flood duration, flow velocity, and the 

potential for wave action and floodborne debris. You should 

consult a design professional before undertaking a dry floodproofing project. Figure 3-16 shows a typical dry floodproofed 

home and Table 3-8 presents the advantages and disadvantages 

of dry floodproofing.

Flood protection elevation is important to know because of the 

hydrostatic pressure that floodwaters exert on walls and floors. 

Because water is prevented from entering a dry floodproofed 

home, the exterior pressure on walls and floors is not counteracted as it is in a wet floodproofed home (see the discussion on 

pages 3-26 and 3-27). The ability of a home’s walls to withstand 

the pressure exerted by floodwaters depends partly on how the 

walls are constructed. Typical frame and masonry veneer walls 

are likely to fail at lower flood depths, are more difficult to make 

WARNING

Dry floodproofing may not be used 

to bring a Substantially Improved or 

Substantially Damaged home into 

compliance with your community’s 

floodplain management ordinance 

or law unless the home is located in 

a community granted with a floodproofing exception.1

 Dry floodproofing 

residential buildings will not reduce 

flood insurance premiums.

WARNING

Even concrete block and brick walls 

should not be dry floodproofed above 

a height of 3 feet, unless an engineering analysis has been performed that 

shows that the walls will withstand the 

expected hydrostatic and hydrodynamic loads and debris impact forces. 

The effects of buoyancy on slab floors 

must also be considered.

1 Use FEMA Form 086-0-24, Residential Basement Floodproofing Certificate: This is a form that is provided to communities participating 

in the National Flood Insurance Program that have been granted an exception by FEMA to allow the construction of floodproofed 

residential basements in Special Flood Hazard Areas.
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watertight, and are more vulnerable to damage from moisture. 

As a result, dry floodproofing is not recommended for homes 

with frame and masonry veneer walls.

Even if frame and masonry veneer walls are reinforced to withstand the pressure of deeper water, the effects of buoyancy must 

be considered. The buoyancy force exerted by water may be 

enough to crack a slab floor or push it up.

Figure 3-16. A typical dry 

floodproofed home.

WARNING

Because dry floodproofing requires 

human intervention, you must be willing and able to install all flood shields 

and carry out all other activities required for the successful operation of 

the dry floodproofing system. As a result, not only must you be physically 

capable of carrying out these activities, you must be home or able to get 

home in time to do so before floodwaters arrive.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-31

AN OVERVIEW OF THE RETROFITTING METHODS 3

Table 3-8. Advantages and Disadvantages of Dry Floodproofing

Advantages Disadvantages

• Reduces the flood risk to the structure and contents if 

the design flood level is not exceeded

• May be less costly than other retrofitting measures

• Does not require the extra land that may be needed 

for floodwalls or reduced levees 

• Reduces the physical, financial, and emotional strains 

that accompany flood events

• Retains the structure in its present environment 

and may avoid significant changes in appearance

• Does not satisfy the NFIP requirement for bringing 

Substantially Damaged or Improved residential structures into compliance

• Requires ongoing maintenance

• Does not reduce flood insurance premiums for residential structures 

• Usually requires human intervention and adequate 

warning time for installation of protective measures

• May not provide protection if measures fail or the flood 

event exceeds the design parameters of the measure

• May result in more damage than flooding if design 

loads are exceeded, walls collapse, floors buckle, or 

the building floats

• Does not eliminate the need to evacuate during floods

• May adversely affect the appearance of the building if 

shields are not aesthetically pleasing

• May not reduce damage to the exterior of the building 

and other property

• May lead to damage of the building and its contents if 

the sealant system leaks

• Involves increased costs for a design professional

• At times, may require invasive retrofits 

• Does not minimize the potential for damage from 

high-velocity flood flow and wave action

NFIP = National Flood Insurance Program

Duration of flooding is critical because most sealing systems will begin to allow some seepage after prolonged 

periods of exposure to water. If your home is in an area where floodwaters remain high for 24 hours or longer, 

you should use a different retrofitting method. Dry floodproofing is not appropriate in areas with a risk of highvelocity flood flow, wave action, or both. Either condition may render dry floodproofing totally ineffective and 

cause severe damage.

Floodproofed homes are not meant to be occupied during a flood. Flood warning time should be adequate and 

evacuation plans should be developed to ensure that occupants are not stranded in the home during a flood. Dry 

floodproofing actually increases the risk to occupants if floodwaters rise higher than the floodproofing design 

level because severe structural damage can occur. Further, the interior of the home will likely be subject to inundation, which may occur rapidly.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

Dry floodproofing is not recommended for homes with basements. Saturated soils pressing against basement walls 

can damage them or cause them to fail. The buoyancy force exerted by saturated soils below the basement can 

cause the basement floor to fail or even push the entire home up.

Sealant systems, especially those that rely on membranes and coatings, can be punctured by ice and other types 

of debris. If your home is in an area where floodwaters are known to carry debris, you should select a different 

retrofitting method.

The total cost for dry floodproofing a home will depend largely on the size of the home, the type and condition 

of the wall system, the flood protection elevation, types of sealant and shield materials used, number of plumbing 

lines that have to be protected by check valves, and number of openings that have to be covered by shields. Table 

3-9 shows approximate costs for elements of a dry floodproofing project.

Table 3-9. Relative Costs of Dry Floodproofing

Component Height of Dry Floodproofing Relative Cost

Waterproof Membrane (above grade)1

3 Feet

Lowest 

Highest

Asphalt (two coats on foundation up to 2 feet below grade)1

Sprayed-on Cement (above grade)1

Wood Flood Shield

Lowest 

Highest

Metal Flood Shield

1 Cement, asphalt, and membrane are alternative sealant methods.

3.4.3 Barrier Systems

Levees and floodwalls are types of flood protection barriers. A levee is a compacted earthen structure; a 

floodwall is an engineered structure usually built of concrete, masonry, or a combination of both (concrete masonry unit [CMU]). When these barriers are built to protect a home, they are usually referred 

to as “residential,” “individual,” or “onsite” levees and floodwalls. The practical heights of these levees 

and floodwalls are usually limited to 6 feet and 4 feet, respectively. These limits are the result of the following considerations:

n As the height of a levee or floodwall increases, so does 

the depth of water that can build up behind it. Greater 

depths result in greater water pressures, so taller levees 

and floodwalls must be designed and constructed to 

withstand the increased pressures. Meeting this need 

for additional strength greatly increases the cost of the 

levee or floodwall, usually beyond what an individual 

homeowner can afford.

WARNING

Levees and floodwalls may not be 

used to bring a Substantially Improved 

or Substantially Damaged home into 

compliance with your community’s 

floodplain management ordinance or 

law and do not eliminate the insurance requirement on the home for 

federally backed mortgages.
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AN OVERVIEW OF THE RETROFITTING METHODS 3

n Because taller levees and floodwalls must be stronger, they usually require more space than is likely to be 

available on an individual lot. This is especially true of levees.

n Levees require a large land area for construction. For example, the levee in Figure 3-20 is 4 feet tall and 

about 27 feet wide.

Chapter 8 presents more detailed information on levees and floodwalls. Figure 3-17 shows a home protected by a 

levee and floodwall; Figure 3-18 shows a home protected by a levee. Remember that levees and floodwalls should 

be designed by a licensed engineer.

Figure 3-17. A home 

protected by a levee (left) 

and a floodwall (right).

Figure 3-18. A home 

protected by a levee.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

Both levees and floodwalls should provide at least 1 foot of freeboard. For example, if you are building a levee to 

protect your home from the base flood, the top of the levee should be at least 1 foot above the BFE. 

For a levee to be effective over time, it must be constructed of 

soils that cannot be easily penetrated by floodwaters, it must 

have proper side slopes for stability, and it must be periodically 

inspected and maintained. In areas where high-velocity flows 

could erode the surface of a levee, the side of the levee exposed 

to floodwater is usually protected with a covering of rock, referred to as riprap, or with other erosion-resistant material. 

Levees can surround a home, or they may be built only across 

low areas and tied into existing high ground.

A floodwall can surround a home or it can protect isolated 

openings, such as doors, windows, and walkout-on-grade basements, depending on flood depths, site topography, and design 

preferences. When built with decorative bricks or blocks or as 

part of garden areas, floodwalls can become attractive architectural or landscaping features. But they can also be built solely for 

utility, usually at a lower cost.

Because a floodwall is made of concrete or masonry rather than 

compacted earth, it is more resistant to erosion than a levee and 

generally requires less space than a levee to provide the same 

level of protection. But floodwalls are usually more expensive. 

As a result, floodwalls are normally considered only for sites 

where there is not enough room for a levee or where high-velocity flows may erode a levee. Also, some homeowners prefer 

floodwalls because they can be more aesthetically pleasing and 

allow for the preservation of existing site features, such as trees.

As shown in Figure 3-17, an interior drainage system, including a sump pump, must be installed in the area protected by a levee or floodwall. The purpose of the system is to remove rainwater trapped inside the protected area 

and, during flooding, to remove water that enters through seepage or infiltration. 

Including an opening in a levee or floodwall may also be necessary to provide access for a car or other vehicle. 

All openings must be equipped with closures similar to those used in dry floodproofing. Installing closures over 

openings in levees and floodwalls requires advance warning of flooding in most cases—in other words, levees 

and floodwalls generally require human intervention. One exception is a low, earthen levee that can be sloped to 

allow vehicle access.

Table 3-10 presents the advantages and disadvantages of levees and floodwalls. Figure 3-19 shows a home protected by a floodwall.

DEFINITION

Riprap refers to pieces of rock or 

crushed stone added to the surface of 

a fill slope, such as the side of a levee, 

to prevent erosion.

WARNING

Special design considerations are 

necessary when levees or floodwalls 

are built to protect a home with a 

basement. Even though the surface 

water is kept from coming into contact 

with the home, the soil below the levee or floodwall and around the home 

can become saturated, especially 

during floods of long duration. The resulting pressure on basement walls 

and floors can cause them to crack 

buckle, or collapse.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-35

AN OVERVIEW OF THE RETROFITTING METHODS 3

Table 3-10. Advantages and Disadvantages of Levees and Floodwalls

Advantages Disadvantages

• Protects the area around the structure from inundation 

without significant changes to the structure

• Eliminates pressure from floodwaters that would 

cause structural damage to the home or other structures in the protected area

• Costs less to build than elevating or relocating the 

structure

• Allows the structure to be occupied during 

construction

• Reduces flood risk to the structure and its contents

• Reduces the physical, financial, and emotional strains 

that accompany flood events

• Does not satisfy the NFIP requirements for bringing 

Substantially Damaged or Improved structures into 

compliance

• May fail or be overtopped by large floods or floods of 

long duration

• May be expensive

• Requires periodic maintenance

• Requires interior drainage 

• May affect local drainage, possibly resulting in water 

problems for others

• Does not reduce flood insurance premiums

• May restrict access to structure

• Requires considerable land (levees only)

• Does not eliminate the need to evacuate during floods

• May require warning and human intervention for 

closures

• May violate applicable codes or regulations

• Individual residential levees or floodwalls cannot be 

used to bring a home with a first floor elevation below 

the BFE into compliance with the NFIP

• May not be ideal for homes with basements because 

hydrostatic pressure on below-ground portions of the 

home can lead to structural failures 

• May require a professional determination that the BFE 

did not increase in the project area, which could make 

levees and floodwalls difficult and expensive to design

NFIP = National Flood Insurance Program

NOTE

The costs for levee construction can 

vary greatly, depending on the distance between the construction site 

and the source of the fill dirt used to 

build the levee. The greater the distance that fill dirt must be hauled, the 

greater the cost.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

Figure 3 19. A home 

protected by a floodwall 

designed as a landscaping 

feature.

Table 3-11 shows the relative costs for levees and floodwalls of various heights. Additional costs for erosion protection using seeding or riprap, interior drainage, and installation of closures may be required for levees and 

floodwalls. Figure 3-20 illustrates the dimensions of these structures.

Table 3-11. Relative Costs of Levees and Floodwalls

Construction Type Existing Foundation Retrofit Relative Cost

Frame, Masonry Veneer, or 

Masonry

Basement, Crawlspace, 

Open Foundation, or 

Slab-on-Grade

Levee constructed 2 feet above grade Lowest 

Highest

Levee constructed 4 feet above grade

Floodwall constructed 2 feet above grade

Levee constructed 6 feet above grade

Floodwall constructed 4 feet above grade
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 3-37

AN OVERVIEW OF THE RETROFITTING METHODS 3

Figure 3-20. Example of floodwall and levee dimensions. 

3.5 Summary

To protect your home from flooding, you may be able to use one or more of the retrofitting methods described in 

this chapter. However, some retrofitting methods are probably inappropriate for your home and some may not be 

allowed by your State or community. Also, if the Substantial Improvement and Substantial Damage requirements 

do not apply to your home, you may be faced with decisions about the level of protection you are willing to pay 

for and the level of risk you are willing to accept. Table 3-12 provides a comparison of the relative costs of each of 

the retrofitting methods listed in this chapter based on home construction type and foundation type.

Chapter 4 will help you decide on a method. Note that cost is not the only consideration when evaluating mitigation measures. Depending on your decision, you can move on to Chapter 5, 6, or 7 for a detailed look at your 

preferred method.
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3 AN OVERVIEW OF THE RETROFITTING METHODS

Table 3-12. Relative Costs of Various Retrofit Measures

Construction Type Existing Foundation Measure Retrofit Relative Cost

Frame, Masonry 

Veneer, or Masonry

Crawlspace or 

Basement

Wet 

Floodproofing Wet floodproof crawlspace to a 

height of 4 feet above lowest 

adjacent grade or wet floodproof 

unfinished basement to a height 

of 8 feet above basement floor

Lowest

Highest

Masonry Veneer or 

Masonry

Slab-on-Grade or 

Crawlspace

Dry Floodproofing

Dry floodproof to a maximum 

height of 3 feet above lowest 

adjacent grade

Frame, Masonry 

Veneer, or Masonry

Basement, 

Crawlspace, or Open 

Foundation

Barrier Systems

Levee constructed to 6 feet above 

grade or floodwall constructed to 

4 feet above grade

Frame, Masonry 

Veneer, or Masonry

Basement, 

Crawlspace, or Open 

Foundation

Elevation

Elevate on continuous foundation 

walls or open foundation

Frame, Masonry 

Veneer, or Masonry

Basement, 

Crawlspace, or Open 

Foundation

Relocation

Elevate on continuous foundation 

walls or open foundation

Frame, Masonry 

Veneer, or Masonry Slab-on-Grade

Elevation

Elevate on continuous foundation 

walls or open foundation

Frame, Masonry 

Veneer, or Masonry Slab-on-Grade

Relocation

Elevate on continuous foundation 

walls or open foundation

Frame, Masonry 

Veneer, or Masonry

Slab-on-Grade, 

Crawlspace, Basement, or Open 

Foundation

Demolition

Demolish existing building and 

buy or build a home elsewhere Varies
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-1

4.0 Deciding Which Method is 

Right for Your Home

With the information from Chapters 2 and 3, you are ready to decide which retrofitting method is right for your 

home. Your decision will be based primarily on hazards to your home, permit requirements, the technical limitations of the methods, and cost. Other considerations might include such things as the appearance of the home 

after retrofitting and any inconvenience resulting from retrofitting. Making a decision involves four steps:

The four steps are described in the next section. In Appendix G, you will find a retrofitting checklist that will 

help you work with local officials, design professionals, and retrofitting contractors. The checklist includes spaces 

where you can record the results of Steps 1 and 2, important questions you should ask, and decision-making matrices that will help you choose a retrofitting method. Before you go any further, you may want to make a copy of 

the checklist (see Appendix G) so that you can begin filling it out.
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4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME

4.1 Making Your Decision

4.1.1 Step 1 – Determine the Hazards to Your Home

If you are using this guide, your home has probably been damaged by flooding or you know that it is in a flood hazard area. 

Refer to Section 2.3 for descriptions of each of the hazards in 

the checklist. Information about flooding and other hazards in 

your area is available from local officials, as discussed later in 

Step 3. But if your home has been flooded, review what you already know. Look at the Step 1 section of the checklist. Answer 

as many of the questions as you can. Local officials, design professionals, and contractors can use the information you provide, 

along with the flood hazard information developed by FEMA 

and other agencies and organizations, to advise you about your 

retrofitting options. 

You also need to be aware of other hazards, such as high winds 

(Figure 4-1), earthquakes (Figure 4-2), fires, landslides, and 

tsunamis. If your home is in an area subject to one or more 

of these hazards, your retrofitting project should take the additional hazards into account. The foundation may need to be 

reinforced and the connections between the foundation, walls, 

and roof may need to be strengthened as part of the retrofitting project. Depending on the nature of the hazards and your 

choice of retrofitting methods, State and local regulations may 

require that additional changes be made to your home, beyond 

those necessary for flood protection. Your local officials can tell 

you if such requirements apply and can give you more information. General information for different hazards can be obtained 

as follows:

n Wildland fire: Wildland fire risk information is available 

from the U.S. Forest Service at http://www.fs.fed.us/

fire/

n Tsunami: Tsunami hazard maps are available from the 

NOAA Center for Tsunami Research at http://nctr.pmel.

noaa.gov/time/resources/

NOTE

The results of Steps 1 and 2 will help 

your local official to advise you and 

will also be useful when you consult 

a design professional or retrofitting 

contractor.

DEFINITION

A tsunami is a large, rapidly moving 

sea wave or series of waves produced 

by an undersea earth movement 

(earthquakes, crustal displacements, 

or landslides) or volcanic eruption. 

NOTE

The retrofitting checklist provided in 

Appendix G references Figure 4-1 

and Figure 4-2. If you are unable to interpret these maps, local officials and 

design professionals will be able to 

help you. Exposure to hazards quantified in Figure 4-1 and Figure 4-2 may 

limit the options available to safely 

retrofit your home. 

WARNING

If you are retrofitting a home that is being Substantially Improved or has been Substantially Damaged, 

your community’s floodplain management ordinance, regulation, or provisions of the building code will 

not allow you to have a basement, as defined by the NFIP, below the BFE. The NFIP regulations define 

a basement as “any area of the building having its floor subgrade on all sides.” If your home has such a 

basement, you will be required to fill it in as part of any elevation project. See Section 2.3.1 for the NFIP 

definition of a basement.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-3

DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4

n Landslide: Landslide risk information is available from the U.S. Geologic Survey at http://landslides.usgs.

gov/

4.1.2 Step 2 – Inspect Your Home

The discussion in Chapter 3 may have prompted you to begin thinking about your home, specifically how it is 

constructed and the type of foundation it has. Before you check with your local officials or consult a design professional and contractor, you should inspect your home and fill out the section of the checklist for Step 2. Four 

characteristics of your home that are particularly important in retrofitting are construction type, foundation type, 

lowest floor elevation, and condition. (When you fill out the portion of the checklist concerning construction and 

foundation type, you may want to refer to the descriptions in Chapter 3.)

Construction Type

As explained in Chapter 3, the construction type for most homes will be frame, masonry veneer, masonry, modular, manufactured, or a combination of two or more of these types. The following generalizations can be made 

about the effect of construction type on retrofitting:

n The most appropriate elevation technique for frame homes and manufactured homes usually is to elevate 

on extended foundation walls or open foundations. 

n Masonry homes are frequently elevated by extending the walls of the home upward and raising the 

lowest floor or by abandoning the lowest floor and moving the living area to an existing or new upper 

floor.

n Frame homes, masonry veneer homes, and manufactured homes are easier to relocate than masonry 

homes.

n Masonry and masonry veneer homes are usually easier to dry floodproof than other types of homes, 

because masonry is a more flood damage-resistant material than the materials used in frame homes.

Foundation Type

As explained in Chapter 3, most homes of the construction types listed above are built on a basement, crawlspace, 

slab-on-grade, or open foundation or on a combination of two or more of these types. The following generalizations can be made about the effect of foundation type on retrofitting:

n Homes on basement or crawlspace foundations are easier to elevate than slab-on-grade homes.

n Elevating homes on basement foundations normally involves elevating or relocating utility system 

components typically found in basements, such as furnaces and hot water heaters.

n Homes on basement foundations should not be dry floodproofed or protected by levees or floodwalls 

unless an engineering evaluation conducted by a design professional shows that it is safe to do so. This 

precaution is necessary because neither dry floodproofing nor the construction of levees or floodwalls 

prevents saturated soils from pressing on basement walls. This pressure, which is unequalized because 

water is not allowed to enter the basement, can damage basement walls or even cause them to fail.

n For some homes on basement foundations, an engineering evaluation is a necessary part of a wet 

floodproofing project. If the home is in an area where saturated soils begin to press on basement walls 

before water enters the basement, the unequalized pressure may damage walls or cause them to fail. If 

wet floodproofing is to be used in this situation, the engineering evaluation must show that the basement 

walls can resist the expected pressure.
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4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME

Figure 4-1. Peak gust wind speeds in the United States. Source: Minimum Design Loads for Buildings and Other Structures, 

ASCE/SEI 7-10. Used with permission from ASCE.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-5

DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4

Figure 4-1 continued. Peak gust wind speeds in the United States. Source: Minimum Design Loads for Buildings and Other 

Structures, ASCE/SEI 7-10. Used with permission from ASCE.
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Figure 4-2. Seismic Design Categories Map of the United States for low-rise Occupancy Category I and II structures 

located on sites with average alluvial soil conditions. Map prepared by U.S. Geological Survey in collaboration with the 

Federal Emergency Management Agency (FEMA)-funded Building Seismic Safety Council’s (BSSC) Code Resource Support 

Committee (CRSC).
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DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4

Figure 4-2 continued. Seismic Design Categories Map of the United States for low-rise Occupancy Category I and II 

structures located on sites with average alluvial soil conditions. Map prepared by U.S. Geological Survey in collaboration 

with the Federal Emergency Management Agency (FEMA)-funded Building Seismic Safety Council’s (BSSC) Code Resource 

Support Committee (CRSC). 
4-8 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME

Figure 4-2 continued. Seismic Design Categories Map of the United States for low-rise Occupancy Category I and II 

structures located on sites with average alluvial soil conditions. Map prepared by U.S. Geological Survey in collaboration 

with the Federal Emergency Management Agency (FEMA)-funded Building Seismic Safety Council’s (BSSC) Code Resource 

Support Committee (CRSC).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-9

DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4

Lowest Floor Elevation

As noted in Chapter 3, the “lowest floor” of your home, as defined by your community’s floodplain management 

ordinance, regulation, or provisions of the building code, is not necessarily the first or finished floor. For example, 

the lowest floor could be the floor of a basement or the floor of an attached garage. As shown in Figure 4-3, the 

location of your lowest floor can vary with foundation type. For homes that are to be elevated, wet floodproofed, 

or dry floodproofed, the difference between the elevation of the lowest floor and the DFE determines how high 

the home must be elevated or how high the wet or dry floodproofing protection must reach. In general, as the 

difference between the lowest floor elevation and the DFE increases, so does the cost of elevating, wet floodproofing, or dry floodproofing. This difference is particularly significant for dry floodproofing. As noted in Chapter 3, 

even masonry walls should not be dry floodproofed higher than 3 feet unless a structural evaluation by a design 

professional shows that it is safe to do so.

The elevation of your lowest floor can be established by a survey, which may be necessary as part of your retrofitting project. But even if you do not know your lowest floor elevation, you can estimate the difference between 

it and the flood protection elevation. Your conversations with your local officials, design professionals, and contractors will help you determine the level of flood protection you should provide. Remember, if your home is being 

Substantially Improved or has been Substantially Damaged according to your community’s floodplain management ordinance, regulation, or provisions of the building code, your flood protection elevation must be at least equal to the DFE. As explained in Step 3, your local officials 

can tell you about this requirement.

Elevation certificates are used to determine insurance premium 

rates under the NFIP. If your community participates in the NFIP, 

it must obtain the as-built elevation of the lowest floor for all 

new or Substantially Improved structures in SFHAs. Your community may use FEMA’s elevation certificates to keep track of 

lowest floor elevations for all of the new and Substantially Improved structures in flood zones. Communities that participate 

in the NFIP CRS are required to obtain and maintain elevation 

certificates. 

If an elevation certificate already exists for your home, it will 

provide information about your specific property, including:

n Property information, including address, building use, 

and foundation information

n FIRM information, including panel number and BFE

n Building elevation information determined by a survey

n Certification by an engineer, architect, or surveyor

n Photographs of the building

Elevation certificates must be completed by a land surveyor, engineer, or architect who is licensed in your State to perform 

surveys. Instructions on completing the elevation certificate and the form itself may be found on the FEMA Web site at 

http://www.fema.gov/media-library/assets/documents/160. 

NOTE

Occasionally, a small area is inadvertently shown to be within the SFHA on 

a FIRM, even though the ground is at 

or above the BFE. If this occurs, an 

individual property owner may submit survey information to FEMA and 

request that FEMA issue a document 

that officially removes a property from 

the SFHA, called a Letter of Map 

Amendment (LOMA).
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Figure 4-3. Difference between flood level and lowest 

floor in homes on crawlspace 

and basement foundations.

Condition

Your design professional or contractor should conduct a detailed inspection of your home before beginning 

any retrofitting work. You can help by first conducting your own assessment of the condition of your home and 

recording any information you have about past or current damage. This information may also be helpful to community officials who advise you about floodplain management and building code requirements and appropriate 

retrofitting methods.

If your home has been damaged by a flood, hurricane or other high-wind event, earthquake, fire, or other disaster, make a note of the extent of the damage, when it occurred, and whether it was repaired (the checklist 

provided in Appendix G can be used to list these damages). If repairs were made, make a note of who made them 

and describe what was done. Any structural damage and repairs 

to walls, floors, foundations, and roofs is particularly important. You should also describe any damage resulting from other 

causes, such as foundation settlement, dry rot, and termite damage. Your goal is to give your design professional and contractor 

as much information as possible so that they can determine how 

the condition of your home will affect your choice of a retrofitting method.

Other Considerations

In addition to construction type, foundation type, lowest floor 

elevation, and condition, you should make note of interior and 

exterior service equipment that must be protected as part of 

NOTE

A historic property is a resource 

(i.e., building, structure, site, object, 

or district) that is listed in or eligible 

for listing in the National Register of 

Historic Places or listed in a State or 

local inventory of historic places. For 

more information, visit your State’s 

SHPO Web site (see Appendix E). 
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DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4

your retrofitting project. Interior service equipment must be 

protected if you elevate or wet floodproof your home. This 

equipment includes furnaces, heating and air conditioning 

ductwork, hot water heaters, large appliances, and electrical system components, such as service panels, outlets, and switches. 

Exterior service equipment must be protected if you elevate, wet 

floodproof, or dry floodproof and, in some situations, if you 

build a levee or floodwall. This equipment includes air conditioning and heat pump compressors and electric and gas meters.

In a home that is dry floodproofed, all openings below the DFE should be sealed. These openings may include 

doors and windows as well as openings for water pipes, gas and electric lines, dryer vents, and sump pump discharge pipes. In a home that is wet floodproofed, dry floodproofed, or protected by a levee or floodwall, backflow 

valves must be installed on all water and sewer lines with openings below the DFE. These valves prevent floodwaters and wastewaters from backing up into your home. Chapter 9 describes how to protect interior and exterior 

service equipment.

4.1.3 Step 3 – Check with Your Local Officials

This is a particularly important step. While you can obtain information from your FIS and your FIRM online (Chapter 2 

discusses how to obtain FIRMs online), your local officials can 

help you to interpret that information. They will have hard 

copies of the FIS and FIRM published for your community by 

FEMA. Your officials will be able to tell you whether your home 

is in your community’s regulatory floodplain and, if so, the BFE 

at the location of your home. They may also have information 

about flood conditions near your home, including flow velocity, 

the potential for wave action and debris flow, rates of rise and 

fall, warning time, and duration of inundation.

Local officials will inform you of Federal, State, and local regulations, codes, and other requirements that can determine 

what retrofitting methods you will be allowed to use and how 

changes can be made to your home. They can also tell you about 

Federal, State, and local programs that provide financial assistance for homeowner retrofitting projects, and they can help 

you determine whether you are eligible for such assistance. 

With the information you recorded in Steps 1 and 2, local officials may also be able to advise you about the most appropriate 

retrofitting method for your home. The officials you need to talk 

to will depend on how your community has assigned responsibilities for floodplain management and construction permitting. 

If you do not know who has these responsibilities in your community, you should begin with an official such as a city clerk, 

mayor, or county administrator.

Remember that if your property is individually historic, potentially historic, or within the boundaries of a historic district and you are receiving Federal financial assistance for your retrofitting project, the Federal agency 

NOTE

Elevation of electric and gas meters 

is typically controlled by the utility 

company.

NOTE

Be sure to ask local officials about 

State or local freeboard requirements 

that may apply to your retrofitting 

project.

NOTE

In addition to meeting the minimum 

requirements laid out in your local 

floodplain ordinance, any retrofit activities should comply with the current 

building code. Talk to your design professional about applicable codes and 

standards.
4-12 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME

providing the assistance must first satisfy Federal historic preservation compliance requirements. Your local officials may not be aware of these requirements if they do not normally deal with federally assisted projects. Should 

historic preservation compliance be triggered, the Federal agency will need to consult with your SHPO. Remember that any compliance review must be completed before retrofitting work is initiated or the Federal assistance 

could be jeopardized.

When you talk to your local officials, be sure to do the following:

n Bring this guide with you.

n Bring your completed retrofitting checklist.

n Discuss what you already know about your home and the hazards that affect it.

n Work through the points listed in the section of the checklist for Step 3.

n Ask any other questions you may have.

n Work through the decision-making matrix provided in Section 4.2 with the official. Use the matrix 

that applies to your situation: Substantial Improvement / Substantial Damage or NOT Substantial 

Improvement / NOT Substantial Damage.

n Take notes about everything you discuss.

Remember that your goal is to find out what you can legally do to retrofit your home, identify the requirements 

you must comply with throughout the retrofitting process, and eliminate retrofitting methods that cannot be applied to your home or do not meet your needs. You may find that the restrictions and requirements of Federal, 

State, and local regulations will eliminate some retrofitting methods from consideration. Ultimately, your decision 

will be based on technical limitations of the methods, cost, and other considerations, such as the effect that retrofitting will have on the appearance of your home. The decision-making matrices will help guide you through 

this process.

Your next step, whether you have chosen one method or are considering two or more, is to consult a properly 

licensed, bonded, and insured design professional and retrofitting contractor. 

4.1.4 Step 4 – Consult a Design Professional and Retrofitting Contractor

To complete this step, you will need to know what types of services are required for your retrofitting project and 

how to evaluate and select design professionals and contractors.

You will probably need the services of a contractor regardless of the retrofitting method you select. The type of 

contractor you hire will depend on the method. You will likely also need to consult a design professional, such as 

an architect or a structural engineer. Alternatively, you can hire a general contractor who will arrange for all the 

necessary services, including those of a design professional. Table 4-1 shows the types of design professionals and 

contractors that may be required for each of the retrofitting methods.

Knowing the types of services required for your retrofitting project is important, but so is hiring a reputable and 

competent design professional and contractor.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-13

DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4

Table 4-1. Requirements for Design Professional and Contractor Services

Method Need for Design Professional 

and/or Contractor Primary Services

Elevation Design Professional Evaluating the condition, stability, and strength of the existing 

foundation to determine whether it can support the increased 

load of the elevated home, including any wind and seismic loads, 

or designing a new foundation 

Contractor: 

Home Elevation Contractor

Disconnecting utilities, jacking the home up, increasing the height 

of the foundation or building a new foundation, and connecting 

utilities

Wet 

Floodproofing

Design Professional Designing any necessary replacements of vulnerable structural 

materials and relocated utility systems

Contractor: 

General Construction Contractor

Replacing vulnerable structural and finish materials below the 

DFE with flood damage-resistant materials, raising utilities and 

appliances to a location above the DFE, and installing openings 

required to allow the entry of floodwaters

Relocation Design Professional Designing any new building, foundation, and site improvements 

that may be required, such as new utility systems

Contractor: 

Home Moving Contractor

Jacking the home up, moving it to the new site, and installing it 

on the new foundation

Contractor: 

General Construction Contractor

Preparing the new site (including grading, foundation construction, and utilities) and restoration of the old site (including 

demolition)

Dry 

Floodproofing

Design Professional For masonry walls to be dry floodproofed, evaluating the condition, stability, and strength of the existing walls to verify whether 

they can withstand the pressure from floodwaters at the DFE; 

designing or selecting flood shields for doors or other openings

Contractor: 

General Construction Contractor

Applying waterproof sealants and membranes, installing flood 

shields over openings below the DFE, installing backflow valves 

in sewer and water lines, and, if necessary, bracing or modifying 

walls so that they can withstand the pressure from floodwaters at 

the DFE

Levees and 

Floodwalls

Design Professional Assessing the adequacy of soils at the site, preparing the engineering design to ensure that the levee or floodwall, including any 

closures required, will be structurally stable under the expected 

flood loads and will be able to resist erosion, scour, and seepage

Contractor: 

General Construction Contractor

Constructing the levee or floodwall

Mitigation

Reconstruction

Design Professional Designing any new building, foundation, and site improvements 

that may be required, such as new utility systems

Contractor: 

Demolition Contractor

Disconnecting and capping utility lines, tearing down the 

damaged home, hauling away debris, and restoration of the site

Contractor:

General Construction Contractor

Building the new home on the restored site or new site; this 

contractor may also be able to do all demolition work

DFE = design flood elevation
4-14 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME

If you have used a licensed design professional and a licensed 

contractor in the past and were satisfied with the work, you 

might consider using them again. Even if they do not provide the types of services you now need, they may be able to 

recommend someone who can. Otherwise, you can search online or contact the professional association that represents the 

types of specialists you are looking for. Appendix F contains a 

list of the addresses and telephone numbers of several of these 

associations. They can usually give you a list of members in 

your area who specialize in the type of work you need. Before 

you hire a design professional or a contractor, check with your 

local Better Business Bureau, consumer protection agency, or 

licensing authorities. These organizations can tell you whether 

there have been any complaints about the quality of the design 

professional’s or contractor’s past work, including whether the 

work was completed on time.

Next, you will need to meet with the design professional and 

contractor to discuss your project. At the meeting, be sure you 

do the following:

n Provide the information you collected in Steps 1, 2, 

and 3.

n Ask the questions listed on the retrofitting checklist 

located in Appendix G, as well as any others you may 

have.

n Verify that the design professional is licensed and 

registered in the State in which the work will be done.

n Verify that the contractor is licensed, bonded, and 

insured as required by State and local laws.

n Ask for proof of insurance. If the design professional 

or contractor does not have disability and worker’s 

compensation insurance, you may be liable for 

accidents that occur on your property.

n Ask for references. Reputable design professionals and 

contractors should be willing to give you the names of previous customers. Call some of them and ask 

how satisfied they were with the work. Ask if they would hire the design professional or contractor again.

n If you are trying to decide between two or more retrofitting methods, discuss your preferences and ask 

for more information.

Any design professional or contractor you hire will need to conduct a site visit to inspect your home and determine how the work should be carried out. During the site visit, you should expect your design professional or 

contractor to assess the structural condition of your home and determine what changes will be required by the 

retrofitting method you choose. If you agree on a method and decide to proceed with the project, be sure to do 

the following:

WARNING

Areas recovering from floods are 

often prime targets for less-thanhonest business activities. Here are 

some pointers that can help you avoid 

problems:

Check with your local Better Business 

Bureau, consumer protection agency, 

or licensing authorities before you hire 

a contractor.

Beware of “special deals” offered 

after a disaster by contractors you 

don’t know.

Beware of unknown contractors who 

offer to use your home as a “model 

home” for their work.

Do not sign any contract under pressure by a salesperson. Federal law 

requires a 3-day cooling-off period for 

unsolicited door-to-door sales of more 

than $25.

Beware if you are asked to pay cash 

on the spot instead of with a check 

made out to the name of a business.

Ask contractors for references. A 

reputable contractor should be able to 

give you a list of past clients in your 

area who can comment on the quality 

of the contractor’s work.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-15

DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4

n Get a written, signed, and dated estimate. It should cover everything you expect to be done. (Some 

design professionals and contractors will charge a fee to prepare the estimate.)

n Get signed and stamped building plans that show details of the proposed retrofitting measure. 

n Decide whether you, the design professional or contractor will obtain the necessary permits.

n Ask for a warranty or guarantee. Any warranty or guarantee from the design professional or contractor 

should be written into the contract. The contract should clearly state the terms of the warranty or 

guarantee, who is responsible for honoring it (such as a manufacturer or the contractor), and how long 

it will remain valid.

n Get a written contract. It should be complete and clearly state all work to be done, the estimated cost, the 

payment schedule, and the expected start and completion dates for the work.

Note that, if a project is funded by a FEMA HMA grant, starting construction prior to FEMA’s approval or award 

of the grant can jeopardize grant funding.

4.2 Decision-Making Matrices

This section provides two matrices that can help you decide which retrofitting method will best meet your needs. 

If your home is either being Substantially Improved or has been Substantially Damaged, the NFIP regulations limit 

your choice of retrofitting methods to elevation, relocation, or demolition (Table 4-2). If your home is NOT being 

Substantially Improved or has NOT been Substantially Damaged, additional retrofitting methods may be considered, such as dry floodproofing, wet floodproofing, and construction of levees or floodwalls (Table 4-3). 

You may require guidance while using the matrix. Local officials, design professionals, and contractors can help 

you evaluate factors you are unsure about, so take the matrix with you when meeting with them. This will be helpful to determine which methods are cost prohibitive or are not technically feasible.

After you have identified the appropriate matrix to use, identify any methods eliminated by regulations, ordinances, 

or laws established by State or other agencies and organizations. Also, you may have already decided that one or 

more methods will not meet your needs. Mark each eliminated method by placing an “X” in the box directly below the name of the method (on the line labeled “Prohibited by Federal, State, or Local Regulations or Eliminated 

by Homeowner”). An “X” in this row means that the method is eliminated and will not be considered further. 

The next step is to evaluate the remaining methods. Your evaluation will be based on the factors listed on the left 

hand side of the matrix. The factors are explained below. For each evaluation factor under each method, discuss 

your concerns with your local official, design professional, and contractor. If your concerns cannot be resolved, 

place an “X” in the appropriate box. After you have worked through the entire matrix, add the number of “Xs” 

under each method and show the sum on the Total “Xs” line. Remember, each “X” is based on your preferences 

and the input of local officials, design professionals, and contractors. So, although not all factors are equally critical, the method with the lowest total “Xs” will probably best meet your needs.

4.2.1 Evaluation Factors

Federal, State, and Local Restrictions – Federal, State, and local regulations may restrict the homeowner’s choice 

of retrofitting measures. Such regulations may include State and local building codes, floodplain management 

ordinance, regulation, or provisions of the building code, zoning ordinances, Federal regulations concerning 

the alteration of buildings classified as historic structures, deed restrictions, and the covenants of homeowners’ 
4-16 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME

associations. The homeowner and the homeowner’s design professional or contractor should check with community officials to determine whether any such restrictions apply.

Appearance – The final appearance of a home and property after retrofitting will depend largely on the retrofitting method used and the DFE. For example, elevating a home several feet will change its appearance much more 

than elevating only 1 or 2 feet, and wet floodproofing will change its appearance very little. However, a change in 

appearance will not necessarily be a change for the worse (see photographs in Chapter 3). The homeowner should 

discuss the potential effects of each method with local officials and with the design professional or contractor.

Cost – The cost of retrofitting will depend largely on the retrofitting method used and the flood protection elevation. For some methods, the construction type (frame, masonry, etc.) and foundation type (crawlspace, slab, etc.) 

will also affect the cost. In general, costs will increase as the flood protection elevation increases, but there may 

be tradeoffs between alternative methods. For example, elevating may be less expensive than relocating when a 

home is raised only 1 or 2 feet, but may become more expensive at greater heights. Other costs include those for 

both routine and long-term maintenance and insurance premiums. Adding additional freeboard to an elevation 

project will generally increase the project’s cost; however, the additional freeboard may produce significant savings 

on insurance premiums. The annual savings on insurance premiums may quickly return the investment required 

to add freeboard. 

Accessibility – Accessibility refers to how easy or difficult it is to routinely reach and enter the home after the 

retrofitting project is completed. The retrofitting methods described in this guide affect accessibility in different 

ways. For example, elevating a home will usually require the addition of stairs, which may be unacceptable to 

some homeowners. In these cases, homeowners may have to consider installing small elevators or using an entirely different retrofit method. Levees and floodwalls can make access more difficult unless they are equipped with 

openings, which require human intervention (see below). Wet floodproofing will have little if any effect on accessibility. Dry floodproofing openings can be very expensive; often points of access are sealed off to control project 

costs. The effect of relocation on accessibility will depend on the location and configuration of the new site.

Code-Required Upgrades – State and local regulations may require that a retrofitted home be upgraded to meet 

current code requirements that were not in effect when the home was built. Portions of the electrical, plumbing, 

and HVAC systems could be affected. For example, the electrical panel might have to be upgraded from fuses to 

circuit breakers. These changes are required for the safety of the homeowner. Other code-required upgrades include those for increased energy efficiency. Any required upgrade can add to the scope and cost of the retrofitting 

project. The homeowner and the homeowner’s design professional or contractor should check with community 

officials to determine whether such regulations apply.

Human Intervention – For retrofitting methods that require human intervention, homeowners must be willing, 

able, and prepared to take the necessary action, such as operating a closure mechanism in a floodwall or placing flood barriers across the doors of a dry floodproofed home. Also, the homeowner must always have adequate 

warning of a coming flood and must be at home or near enough to be able to reach the home and take the necessary action before floodwaters arrive. If these conditions cannot be met, retrofitting methods that require human 

intervention should be eliminated from consideration.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 4-17

DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME 4

4.2.2 Substantial Improvement / Substantial Damage Matrix

Table 4-2. Retrofitting Methods for Substantially Improved or Substantially Damaged Homes

Retrofitting Methods

Substantially Improved or Substantially Damaged Homes

Evaluation 

Factors

Elevation1

Relocation Demolition

Elevation on

Extended 

Foundation Walls 

Elevation 

on Open 

Foundation 

New Living Area 

over Abandoned 

First Floor 

Prohibited by 

Federal, State, or 

Local Regulations 

or Eliminated by 

Homeowner

Appearance

Cost

Accessibility

Code-Required 

Upgrades

Human 

Intervention

Other

Total “Xs”

1

 Note that if you elevate a Substantially Improved or Substantially Damaged home, you can still wet floodproof an 

enclosed area under the home below the BFE, provided that: (1) the area is only used for parking, building access, and 

storage, (2) the area is designed to allow for automatic entry and exit of flood waters through the use of openings, and (3) 

the area is constructed with flood damage-resistant materials. 
4-18 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

4 DECIDING WHICH METHOD IF RIGHT FOR YOUR HOME

4.2.3 NOT Substantial Improvement / NOT Substantial Damage Matrix

Table 4-3. Retrofitting Methods for Homes That are NOT Substantially Improved or Damaged

Retrofitting Methods

for Homes NOT Substantially Improved or Substantially Damaged

Evaluation 

Factors

Elevation

 Relocation Dry 

Floodproofing

Wet 

Floodproofing

Levees or 

Floodwalls Demolition

Elevation on 

Extended 

Foundation 

Walls

Elevation 

on Open 

Foundation

New Living 

Area over 

Abandoned 

First Floor 

Prohibited by 

Federal, State, or 

Local Regulations 

or Eliminated by 

Homeowner

Appearance

Cost

Accessibility

Code-Required 

Upgrades

Human 

Intervention

Other

Total “Xs”
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 5-1

5.0 Elevating Your Home

One of the most common retrofitting methods for homes is elevation. When a home is properly 

elevated, the living area should be above most flood levels. Several elevation techniques are available. In general, they involve lifting the home and building a new foundation or extending the 

existing foundation below it, or leaving the home in place and either building a new elevated floor 

system within the home or adding a new upper story and converting the ground level to a compliant 

enclosure. 

During the elevation process, most frame, masonry veneer, and masonry homes are separated from their foundations, raised on hydraulic jacks, and held by temporary supports while a new or extended foundation is constructed 

below. The living area is raised so that only the foundation remains exposed to flooding. This technique works well 

for homes originally built on basement, crawlspace, and open foundations. When homes are lifted with this technique, the new or extended foundation can consist of continuous walls or separate piers, posts, columns, or piles. 

Masonry homes are more difficult to lift, primarily because of their design, construction, and weight, but lifting 

these homes is possible. In fact, numerous contractors throughout the United States regularly perform this work. 

A variation of this technique is used for frame, masonry 

veneer, and masonry homes built on slab-on-grade foundations. 

In these homes, the slab forms both the floor of the home and 

either all or a major part of the foundation. Although elevating 

these homes with the walls and slab attached and lifting them 

together may appear easier, this may not be a viable option. A 

slab-on-grade home should be inspected by a structural engineer to determine whether the slab is sufficient to support the 

house without being continuously supported by the soil it was 

designed to sit on top of. If the slab isn’t strong enough to be 

lifted, the walls can be elevated and a new wood floor system 

constructed. 

For masonry homes on slab-on-grade foundations, an alternative mitigation technique in which the home is left 

on its original foundation may be easier. This technique involves removing the roof and raising the living space, 

either by extending the walls of the home and raising the floor or by abandoning the lower level and moving the 

living space to an existing or newly constructed upper floor. Another alternative for homes with high ceilings may 

be to shift the floor system on the upper floors reducing the ceiling height, but creating space above the BFE to 

construct a new first floor. The abandoned lower enclosed area is then converted to a compliant enclosure that is 

used only for parking, building access, or storage. See Section 5.2.2 for more information. 

NOTE

Always use a licensed, bonded, and 

insured contractor for elevation projects. Be sure that your contractor has 

experience with elevation projects 

and understands the considerations 

discussed in Section 5.1. Prior to 

hiring a contractor, be sure to check 

references.
5-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

5 ELEVATING YOUR HOME

In both of these techniques, portions of the original walls will be below the DFE. This approach is appropriate for 

masonry construction, but not for frame construction, because of potential code compliance issues and flood insurance implications for wood-frame foundations. 

This chapter describes and illustrates various elevation methods and discusses the most important considerations 

regarding elevation. Remember, you should never attempt an elevation project without the help of experienced 

design and construction professionals. 

5.1 Considerations 

Prior to elevating a home, a number of factors, such as how high to elevate, whether to incorporate the existing 

foundation, other hazards (wind, earthquake, etc.), how access to the house will be accomplished, and which 

elevation technique is appropriate, should all be considered. Some common factors to consider in elevating your 

home are described in the sections that follow.

5.1.1 Amount of Elevation 

The amount of elevation required is determined by the flood 

protection elevation you have chosen. The minimum elevation 

should be determined based on various sources of information. 

Decisions need to be made based on the effective date of the 

FIRM and whether any additional data, such as changes to the 

flood source around the building site or flooding events since 

the FIRM, may make is necessary to elevate higher. Homeowners 

should also consider that potential future changes to the factors 

that influence floods may result in higher flood events. Resources such as Hurricane Sandy Recovery Advisory No. 5, Designing 

for Flood Levels Above the BFE After Hurricane Sandy (FEMA.2013b), may 

provide some helpful guidance on how to determine your flood 

protection elevation. Consider whether the locally enforced 

elevation requirements are sufficient or whether you should 

consider elevating even higher. For example, if your house is located in Zone A, you may only be required to 

elevate your home to the BFE so that the top of the lowest floor is at or above that elevation (see Figure 5-1). 

However, elevating 1 or 2 feet higher will provide increased protection and result in lower annual flood insurance 

premiums.

As explained previously, if your home is being Substantially Improved or has been Substantially Damaged, your 

community’s floodplain management ordinance, regulation, or provisions of the building code will require that 

your lowest floor be elevated to or above the BFE. If Substantial Improvement and Substantial Damage requirements 

do not apply, you may be able to elevate to any height you wish. Keep in mind that raising your home to an elevation 

below the BFE not only provides less protection, but will not provide the lower insurance premiums that come with 

elevation to or above the BFE. If you decide to raise your home to an elevation below the BFE, the community is required to evaluate the cost of all improvements, including the cost to elevate your home to determine whether your 

proposed project is a Substantial Improvement. Regardless of whether your home is being Substantially 

Improved or has been Substantially Damaged, you should consider incorporating at least 1 foot of freeboard into 

your flood protection elevation (as shown in Figure 5-1). Often this will ensure that at a minimum, the floor 

framing will be elevated above the floodwaters.

NOTE

FEMA HMA grants will only support 

elevation projects to the flood protection elevation stipulated by the 

engineering standard ASCE 24, Flood 

Resistant Design and Construction, 

or higher. In most instances, the minimum elevation will be the BFE plus at 

least 1 foot of freeboard.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 5-3

ELEVATING YOUR HOME 5

Elevating a home to 3 or 4 feet above the existing ground level usually will not have a great effect on its appearance and will require only minimal landscaping and regrading. If you plan to elevate more than 4 feet above the 

existing grade, you should consider elevating your home a full story. Not only will your home be protected against 

deeper floods, but you can use the space below for parking, building access, or storage (Figure 5-2). If you decide 

to incorporate parking under a living area, verify that any necessary code requirements have been addressed in 

the retrofit. This could include providing a fire-rated floor assembly between the parking area and the living area 

above. Hurricane Isaac Recovery Advisory 1, Minimizing Wind and Water Intrusion by Covering the Underside of Elevated Buildings

(FEMA. 2012c), provides some guidance on such assemblies. 

Figure 5-1. As shown in the 

cutaway view, the lowest 

floor is above the flood 

level. When at least 1 foot of 

freeboard is provided, only 

the foundation is exposed to 

flooding.
5-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

5 ELEVATING YOUR HOME

WARNING

If your home is being Substantially Improved or has been Substantially Damaged and is in a Coastal 

High Hazard Area (Zone V, VE, or V1–V30 on the FIRM for your community), your community’s floodplain management ordinance, regulation, or provisions of the building code requires that the bottom of 

the lowest horizontal structural member (rather than the lowest floor) be elevated to or above the BFE. In 

many homes, the lowest horizontal structural member is a beam that supports the framing of the lowest 

floor. With the exception of Elevating on an Open Foundation (Section 5.2.3), the elevation techniques 

presented in this guide are not appropriate for homes in Coastal High Hazard Areas. If you have any 

doubt about the type of flood hazards that may affect your home, check with your local officials.

Figure 5-2. This home in 

Cedar Falls, IA, was elevated 

one full story. The garage 

and storage area are at the 

home’s original elevation.

5.1.2 Existing Foundation 

In general, the most economical approach to elevating a 

home is to use as much of the existing foundation as possible. 

Although some elevation methods do not allow this approach, 

most do. If you choose one of the latter, a design professional 

must evaluate the capacity of your existing foundation to support the loads that will be imposed by the elevated home and, 

as discussed in the next section, the loads expected to result 

from flooding and other hazards at the site. If changes must 

be made to the foundation to increase its strength and stability, 

they can be made as part of your retrofitting project. A design 

professional may determine that an older foundation constructed of mortared rock, masonry, or even poured concrete 

needs to be completely replaced or the local building code may 

require that it be replaced.

CROSS REFERENCE

Fill used for structural support and elevation is prohibited in Coastal High 

Hazard Areas. Check with your local officials about State and local 

requirements considering the use of 

fill. NFIP Technical Bulletin 5, Freeof-Obstruction Requirements (2008), 

offers further guidance about using fill 

in Zone V.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 5-5

ELEVATING YOUR HOME 5

The type of foundation on which your home was originally built (basement, crawlspace, slab-on-grade, piers, 

posts, piles) also can affect the elevation process. This issue is discussed in Section 5.2.3. 

5.1.3 Hazards 

Because so many elevation techniques are available, elevation is practical for most flood situations, but the flooding 

conditions and other hazards at the home site must be examined so that the most suitable technique can be determined. Regardless of the elevation technique used, the foundation of the elevated home must be able to withstand 

all the necessary loads (wind, seismic, snow, etc.) on the house, which also should include the expected flood 

loads from buoyancy, hydrostatic pressure, hydrodynamic pressure, and debris impact. It must also be able to resist 

undermining by any expected erosion and scour. 

If you are elevating a home in an area subject to high winds, earthquakes, or other hazards, a design professional should determine whether the elevated home, including its foundation, will be able to withstand all of the 

horizontal and vertical forces expected to act on it. In making this determination, the design professional must 

consider a number of factors, including the structure and condition of the home, the soil conditions at the site, 

the proposed elevation technique, and the hazards at the site. The conclusion may be that additional modifications 

must be made during the retrofitting project. In some flooding conditions, another alternative, such as relocation, 

may be a better option. High wave loads, swift currents, or unstable soil may make relocation necessary. Sometimes the condition of the house and the necessary retrofits may also indicate that reconstruction of the entire 

house is a more cost-effective option.

5.1.4 Access 

Elevating a home usually requires that new means of access be provided. For example, if your entry doors were 

originally at ground level, new staircases, elevators, or ramps will have to be built. When an attached garage is 

elevated, providing access for vehicles may require changes to portions of your lot, such as building a new, elevated driveway that ties into high ground elsewhere. This solution can be practical when the amount of elevation 

required is no more than 2 or 3 feet. As noted earlier, when the amount of elevation reaches 4 or more feet, you 

should consider elevating your home a full story so that you can use the lower level for parking and avoid the 

need for an elevated driveway. Constructing a means of access can be a considerable cost and should be included 

in the price for the elevation.

Figure 5-3. With attention 

to detail and planning, 

homeowners have created 

attractive retrofitted homes.
5-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

5 ELEVATING YOUR HOME

The need to provide a new means of access is often the main objection that homeowners have to elevating. But 

functional and attractive solutions to this problem can usually be developed, as shown in Figures 2-2 and 5-3.

5.1.5 Home Size, Design, and Shape 

In general, the larger the home and the more complex its design and shape, the more difficult it will be to lift on 

jacks. Multistory homes are more difficult to stabilize during the lifting process and, as the dimensions and weight 

of a home increase, so do the required numbers of jacks and other pieces of lifting equipment. Exterior wall coverings such as stucco and brick veneer complicate the lifting process because they must either be removed or braced 

so that they will stay in place when the home is lifted. Homes with simple square or rectangular shapes are easier 

to lift than those with attached garages, porches, wings, or additions, which often must be detached and lifted 

separately, especially if they are built on separate foundations. Features such as chimneys can also add to the cost 

of lifting a house because they must be either braced or removed during the lifting process. Older properties may 

also include features such as cisterns, which may create access issues and result in higher lifting costs.

Before a home is lifted, a design professional should inspect it to verify its structural soundness. All the structural 

members and their connections must be able to withstand the stresses imposed by the lifting process. Lifting an 

unsound home can lead to potentially expensive damage. 

5.1.6 Service Equipment 

Before your home is elevated, all utility lines (water, sewer, gas, 

electric, telephone, etc.) must be disconnected. At the end of 

the project, the lines will be reconnected and any landscaping 

that may be necessary will be completed. Adjustments may be 

required for any overhead electrical service lines to ensure they 

maintain all appropriate vertical and horizontal clearances. If 

you elevate your home on an open foundation, utility lines that 

enter the home from below may be exposed to damage from 

flooding and below-freezing temperatures. Protecting utility 

lines in these situations usually involves anchoring them securely to vertical foundation members and, if necessary, insulating them. All service equipment outside the home, 

such as air conditioning and heat pump compressors, and gas and electric meters, must be elevated to or above the 

flood protection elevation. In homes with basements, any service equipment originally installed in the basement 

must be raised above the flood protection elevation, which may require relocation to an upper floor or a small 

addition to house the equipment. Chapter 9 discusses the protection of service equipment. Moving or relocating 

utility meters, such as natural gas or electric meters, may be at the discretion of the utility service provider. Providers may require meters to stay at elevations below the BFE. 

5.2 The Elevation Techniques

The elevation techniques and their applications to different types of homes are discussed in the following sections. 

5.2.1 Elevating on Extended Foundation Walls

Frame, masonry veneer, and masonry homes can all be elevated on extended foundation walls. As discussed in the 

following sections, the technique used for homes on basements, crawlspaces, and open foundations differs from 

that used for homes on slab-on-grade foundations. The potential for an elevated slab-on-grade foundation to fail 

DEFINITION

Service equipment includes utility systems, heating and cooling 

systems, and large appliances in a 

retrofitted home.
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ELEVATING YOUR HOME 5

either during the lifting process, or even worse once the house is occupied, makes this elevation technique one 

that should be carefully scrutinized by a design professional familiar with the calculation of building loads and 

the design of concrete slabs.

Homes on Basement Foundations and Crawlspace Foundations

The elevation process is the same for frame, masonry veneer, and masonry homes on basement and crawlspace 

foundations. Figures 5-4a through 5-4d illustrate the process.

First, holes are made at intervals in the foundation wall so that a series of steel I-beams can be installed at critical points under the floor framing (Figure 5-4a). If the foundation walls are made of concrete blocks, the lifting 

contractor can remove individual blocks to create the required holes. If the walls are made of poured concrete, 

the holes will be cut out. The I-beams are placed so that they run perpendicular to the floor joists. A second set 

of beams is then placed below and perpendicular to the first set (Figure 5-4a). The two sets of beams extend the 

width and length of the home and form a cradle that supports the home as it is being raised. 

In Figure 5-4a, the foundation walls are shown extending far 

enough above the ground surface to provide easy access to the 

area below the floor framing. However, in some homes, the 

foundation walls will not be this high. To lift such a home, the 

contractor must first dig trenches at intervals around the foundation. The I-beams are then lowered into the trenches and 

inserted below the floor framing. The contractor may also have 

to dig holes for the lifting jacks, as shown in the figure. The 

number of jacks needed will depend on the size, shape, and type 

of home being lifted.

Once the beams and jacks are in place, the elevation process begins. The jacks will extend only so high; so at intervals during 

the process, the home and jacks are supported temporarily on 

cribbing while the jacks are raised (Figure 5-4b). After the home is elevated high enough, it is again supported 

on cribbing while the foundation walls are extended to the desired height with concrete blocks or poured concrete (Figure 5-4c). The home is then lowered onto the extended foundation walls, the I-beams are removed, and 

the holes where the beams passed through are filled. An important part of the project is installing flood openings 

in the foundation walls (your building permit should specify the size and location of these openings), no higher 

than 1 foot above the ground, so that floodwaters can enter and equalize the internal and external hydrostatic 

pressures. As shown in Figure 5-4c, the contractor may be able to create these openings by only partially filling 

the I-beam holes.

CROSS REFERENCE

For more information about openings 

requirements, refer to FEMA Technical 

Bulletin 1, Openings in Foundation 

Walls and Walls of Enclosures (2008), 

and FEMA P-259, Engineering Principles and Practices for Retrofitting 

Flood-Prone Residential Structures

(FEMA. 2012a).
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5 ELEVATING YOUR HOME

Figure 5-4a through 5-4d. 

Elevating a basement or 

crawlspace foundation home 

on extended foundation 

walls.

5-4a

5-4b
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ELEVATING YOUR HOME 5

Figure 5-4a through 5-4d continued. Elevating a basement or crawlspace foundation home on extended foundation walls.

5-4c 5-4d

Homes on Slab-on-Grade Foundations

Frame, masonry veneer, and masonry homes on slab-on-grade foundations are also lifted with hydraulic jacks and 

a network of steel I-beams. However, slab-on-grade homes present special difficulties and require a different lifting technique. An alternative is to leave the existing slab and extend the walls (see Section 5.2.2), or convert the 

ground level of the home and build a new upper floor (see Figures 5-12a through 5-12c). See Hurricane Sandy 

Recovery Advisory No. 7, Reducing Flood Risk and Flood Insurance Premiums for Existing Residential Buildings in Zone A (FEMA. 

2013e) for more information on doing such conversions.

The importance of evaluating the slab

To determine the best approach, the slab must be evaluated by a structural engineer. The engineer can determine 

which elevation method is suitable for the house. Often the slab will not be of sufficient strength to span the distances necessary to use the standard interior pier spacings associated with wood-framed floor systems.

The floor of a home on a slab-on-grade foundation is formed by the slab rather than the wood joist and beam 

framing found in homes on crawlspace and basement foundations. The slab is usually 31⁄2 to 6 inches thick and is 

often reinforced only with wire mesh. As shown in the cross-section view in Figure 5-5, the slab can be supported 

by foundation walls and footings or by a thickened edge created when the slab is poured. Slabs are almost never 

designed to be lifted and supported on a wall and pier system but rather to rest on the ground. If the slab is not 

designed to be supported it could fail during elevation as a result of the loads. The wire mesh is often insufficient 

to provide adequate reinforcing in the slab and is only intended to prevent the slab from cracking.

Because the slab forms the floor of the home, and occasionally the foundation as well, elevating a slab-on-grade 

home is more difficult than elevating a house with a wood-framed floor system regardless of the lifting method 

used. Because this process is more difficult than that used for homes on basement and crawlspace foundations, it 

should be performed only by a highly skilled contractor with extensive experience in lifting slab-on-grade homes. 

In lifting the slab, the contractor must take extreme care during the lifting process to avoid breaking the slab and 

compromising the structural integrity of the home. 
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5 ELEVATING YOUR HOME

Although the slab can be lifted while still attached to the walls, the slab may be dangerously weak once the house 

is occupied. A more practical method may be to separate the walls from the slab and lift the house leaving the slab 

in place. A new wood-framed floor can be constructed and the existing slab can remain in place. 

Figure 5-5. Cross-section view of slab-on-grade foundation variations.

Elevating with the slab remaining in place

If a design professional determines that the original slab is strong enough to support the elevated home under the 

expected flood, wind, earthquake, and other loads, the slab may be left in place and the new foundation walls built 

on top of it. Otherwise, the slab must be cut back and a completely new foundation constructed, as shown in Figure 5-6. The lift is accomplished by cutting openings into the walls and inserting I-beams through the openings. 

To enable the beams to lift the home, the contractor attaches horizontal wood bracing to the interior and exterior 

walls at the tops of the openings (Figure 5-7). Figure 5-8 shows an example of a retrofitted slab-on-grade house 

where the house was detached from the slab and a new floor system was constructed.

When the beams are jacked up, they push against the bracing, which distributes the lifting force equally across 

the walls. The bracing also supports the walls, which lack the structural stability that would otherwise be provided when the walls and floor are left attached. Without bracing, the walls could twist, bend, or collapse when 

the home is lifted. 

Another option for elevations that do not exceed more than a few feet may be to construct a new elevated concrete 

slab. Building a new slab floor involves placing fill dirt on top of the old slab and pouring a new slab on top of the 

fill. Although the old slab is left in place, it is usually broken up so that it will not be forced up by the buoyant effect of floodwaters or saturated soil.

The primary advantage of lifting the home without the slab is that the home is lighter and, therefore, easier to lift. 

This benefit applies mainly to frame and masonry veneer homes. However, this method has several disadvantages:

n Cutting holes in the interior and exterior walls of the home and attaching wood bracing is invasive and 

must be repaired before the elevated home is habitable.
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ELEVATING YOUR HOME 5

n Because of the invasive lifting techniques, the habitable parts of the first floor may not be available for 

use for an extended period of time during the project.

n The contents of the first floor must be removed before the elevation process can begin.

Figure 5-6. Building a new 

foundation for a slab-ongrade home.

Figure 5-7. Elevating a slabon-grade home without the 

slab.
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5 ELEVATING YOUR HOME

Figure 5-8. House in Zone A 

was detached from its slab 

foundation (which remains) 

and elevated on masonry 

piers. The floor system is 

supported by new wood 

joists (Mandeville, LA).

Elevating with the slab attached

When the slab is determined to be of sufficient thickness and reinforced such that it can be supported on piers, the 

slab can be lifted while still attached to the walls. The elevation process (Figures 5-9a through 5-9d) is similar to 

that used for homes on basement and crawlspace foundations, except that the I-beams must be placed below the 

slab, which is at ground level. Therefore, the contractor must dig trenches at intervals around the foundation, and 

tunnel under the slab. The I-beams are lowered into the trenches and moved into place beneath the slab through 

the tunnels (Figure 5-9a). 

The contractor must also dig holes for the lifting jacks because they have to be placed below the beams. Once the 

beams and jacks are in place, the lifting process begins. As shown in Figures 5-9b and 5-9c, the home is lifted and 

a new foundation is constructed beneath it.

Some slab-on-grade houses are constructed on what are called stemwalls. These systems consist of a concrete footing with a short perimeter wall made of poured concrete or masonry block. If the slab was originally supported 

by foundation walls and footings (see left and middle illustrations in Figure 5-5), the contractor may be able to 

leave them in place and extend the existing walls upward. This approach is possible only when a design professional determines that the original foundation walls and footings are strong enough to support the elevated home 

and slab under the expected flood, wind, earthquake, and other loads. If the slab was originally supported on the 

ground by its own thickened edge (see right illustration in Figure 5-5), a completely new foundation must be 

constructed.

In both situations, the contractor must construct not only foundation walls under the perimeter of the slab, but 

also additional vertical foundation members, such as piers, at several locations under the slab. These additional 

foundation members are necessary because slabs are designed to rest directly on the ground, not to support the 

weight of the home. 
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ELEVATING YOUR HOME 5

Figure 5-9a through 5-9d. 

Elevating a slab-on-grade 

home with the slab attached.

5-9a

5-9b
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5 ELEVATING YOUR HOME

Figure 5-9a through 5-9d 

continued. Elevating a slabon-grade home with the slab 

attached.

5-9c

5-9d
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ELEVATING YOUR HOME 5

The primary advantage of lifting the home with the slab still attached to the walls is that the home can remain 

intact and many of the contents can remain inside during the lifting process. However, this method has several 

disadvantages:

n Most slabs were constructed to be continuously supported by the ground underneath them and are 

minimally reinforced. Insufficiently supporting such a slab can result in cracking or catastrophic failures 

that could potentially injure the occupants.

n Retrofitting slabs with insufficient thickness or reinforcement can be expensive.

n If the house is not lifted evenly, the slab could crack during the elevation process.

n If uneven settlement occurs, the weight of the elevated slab may exceed the capacity of the masonry piers 

commonly used for elevation projects.

Do not consider elevating a slab-on-grade house without seeking the help of a structural engineer. Although many 

elevation contractors have experience elevating slab-on-grade houses, concrete has the potential to catastrophically fail and appropriately assessing the strength of the slab may be difficult for most contractors. Slabs cast on 

the ground can have wide variations in thickness and the pier spacing may need to be adjusted once the bottom 

of the slab becomes visible. Structural engineers familiar with the design requirements for slabs can properly address the risk of a slab failure.

5.2.2 Alternative Elevation Techniques for Masonry Homes on Slab-on-Grade 

Foundations

Elevating by Extending the Walls of the Home 

An alternative technique for elevating a masonry home on a slab-on-grade foundation is to extend the existing 

walls of the home upward and then build a new raised floor above the old slab. This technique is illustrated in 

Figures 5-10a through 5-10c.

First the roof framing and roof are removed so that the tops of the walls will be accessible. The contractor can then 

extend the walls upward with additional courses of either concrete block (as shown in Figure 5-10b) or brick or 

with wood or metal framing. The choice of materials is based on several considerations, including cost, the final 

appearance of the home, the strength of the existing foundation, and the design requirements associated with the 

identified hazards, including high winds and earthquakes.

The final height of the extended walls will depend on how high the lowest floor must be elevated. For example, 

if the lowest floor must be elevated 3 feet to reach the flood protection elevation, the height of the walls must be 

increased by the same amount if the original ceiling heights in the home are to be maintained.

The new raised floor can be either a wood-framed floor system or an elevated concrete slab similar to the original 

slab (referred to as a stemwall). When a new wood-framed floor system is installed, the area below the floor becomes a crawlspace (as in Figure 5-10c) or other enclosed area that may be used for parking, building access, or 

storage. Flood openings must be installed in the foundation walls to allow external and internal water pressures 

to equalize. Additional openings may be needed for ventilation. 

For a new elevated slab floor, fill dirt is placed on top of the old slab and compacted as required. Then a new slab 

is poured on top of the fill. When this method is used, openings in the foundation walls are not required because 

the entire area under the new slab is completely filled with dirt and is therefore protected from the pressure of 

floodwaters. 
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5 ELEVATING YOUR HOME

5-10a

Figure 5-10a through 5-10c. Elevating by extending the walls 

of a solid masonry home.

5-10b

5-10c
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ELEVATING YOUR HOME 5

Elevating by Abandoning the Lower Enclosed Area 

Another alternative for a masonry home on a slab-on-grade 

foundation is to abandon the existing lower enclosed area of the 

home (the area with the slab floor) and allow it to remain below the flood protection elevation. This technique requires that 

the living area be restricted to upper floors of the home and 

that the lower enclosed area be used only for parking, building access, or storage. Because this technique leaves the original 

floor and walls below the flood protection elevation exposed to 

flooding, it is best suited to masonry homes on slab-on-grade 

foundations. In these homes, both the walls and floor are made 

of concrete or masonry, which are not easily damaged by contact with floodwaters. Only materials resistant to flood damage 

should be used on portions of the building below the flood protection elevation.

The amount of work required for this technique depends largely on whether the home already has an upper floor 

that can be used for living space. When an upper floor exists, abandoning the lower enclosed area involves removing any interior finishing materials below the flood protection elevation (including interior wall sheathing and 

insulation unless required by code) and elevating or relocating vulnerable appliances (such as furnaces, washing 

machines, and freezers) and utility system components (such as electrical wiring and service boxes). These modifications are the same as those required for wet floodproofing, as described in Chapter 7. 

This elevation measure may be the most practical for town houses or row houses. In an attached dwelling at least 

one wall and usually two are common or “party” walls. These walls make lifting the actual walls impossible. 

Shifting the elevation of the floor joists may be the only practical solution in these situations. This technique requires significant alterations to the front and back walls of the unit or any walls that are not common to the other 

units. These walls typically have the windows and exterior doors, which must be relocated (shifted up) as the 

floor framing is shifted. Interior walls also must be removed and replaced with these projects. Although this is an 

invasive method, the flood risk and potential financial implications of flood insurance premiums may make it a 

palatable mitigation option. Figure 5-11 illustrates how this could be done for a row house with high ceilings. 

This method also makes it possible to convert the ground floor to an NFIP-compliant enclosure and make adjustments to the upper floors, such as moving utilities and mechanical equipment to higher floors. Uses appropriate 

for areas below the BFE are described in Chapter 7.

For one-story homes, abandoning the lower enclosed area requires the construction of a new second story as 

shown in Figures 5-12a through 5-12c. The required steps are similar to those described in Section 5.2.1. The roof 

and roof framing are removed, a new second story is built on top of the existing walls, the roof and roof framing 

are replaced, and openings are added for floodwaters. The construction options are the same: frame or masonry. 

Again, the choice is based primarily on the considerations of cost, final appearance, the strength of the existing 

foundation, and the need to address other natural hazards, such as high winds and earthquakes.

CROSS REFERENCE

For more information about flood openings, refer to FEMA Technical Bulletin 

1, Openings in Foundation Walls 

and Walls of Enclosures (2008), and 

FEMA P-259, Engineering Principles 

and Practices for Retrofitting FloodProne Residential Structures (FEMA. 

2012a).
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5 ELEVATING YOUR HOME

Figure 5-11. Elevation of 

the floor levels in a row 

house to maximize living 

area above the BFE in 

Zone A (Source: Hurricane 

Sandy Recovery Advisory 3 

(FEMA. 2013f)).

Figure 5-12a through 5-12c. 

Home elevated by adding a 

new second story over an 

abandoned lowest floor.

5-12a
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ELEVATING YOUR HOME 5

Figure 5-12a through 5-12c 

continued. Home elevated by 

adding a new second story 

over an abandoned lowest 

floor.

5-12b

5-12c
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5 ELEVATING YOUR HOME

Mitigation Reconstruction

Mitigation reconstruction is the construction of an improved, elevated building on the same site where an existing building and/or foundation has been demolished. There may be reasons why elevating your home may not be 

feasible. If physical or economic obstacles are too great, you may want to consider demolishing your home and 

rebuilding a code-compliant home that is elevated above the flood level (see Chapter 6).

For FEMA HMA grants, mitigation reconstruction is only permitted if traditional structure elevation cannot be 

implemented. Activities that result in the construction of new living space at or above the BFE will only be considered when consistent with the mitigation reconstruction requirements. 

5.2.3 Elevating on an Open Foundation

Frame, masonry veneer, and masonry homes on basement, 

crawlspace, and slab-on-grade foundations can also be elevated on open foundations consisting of piers, posts, columns, or 

piles. Homes originally constructed on open foundations can 

also be elevated this way. 

Piers

Figures 5-13a through 5-13d show how a home on a basement 

or crawlspace foundation can be elevated on masonry piers. The 

lifting process is the same as that shown in Figure 5-4 for elevating on extended foundation walls. Once the home is lifted high 

enough, new masonry piers may be built on the existing foundation, if it is adequate. If the existing foundation 

is not adequate to support the elevated home, it will have to be either modified or removed and replaced by separate footings for the individual piers.

An existing basement must be filled in with dirt and graded. An old basement slab can be left in place and covered with fill dirt. A basement slab does not need to be removed, but it should be broken up in place so that it will 

allow water to seep through it and reduce buoyancy forces before being covered with fill dirt. The home in Figure 

5-13d has been elevated approximately one full story, and a new concrete slab has been poured at ground level 

below it. The open area below the home can be used for parking, building access, or storage.

Piers can be constructed of cast-in-place concrete as well as fully grouted masonry blocks. However, regardless of 

the construction materials used, piers are designed primarily for vertical loading imposed by the weight of the 

home, including its contents and any exterior loads, such as those imposed by snow. Because the forces associated 

with flooding, wind, and earthquakes can impose horizontal loads, piers used in retrofitting must be adequately 

reinforced with properly sized and placed steel bars. The connections between the piers and the original foundation and elevated home also must be able to resist the expected horizontal and vertical loads on the home so the 

home does not shift off the foundation.

NOTE

Open foundations are required for elevations in Coastal High Hazard Areas 

(Zones V, VE, and V1–V30) and are 

recommended for elevations in riverine floodplains where flow velocities 

are greater than 5 fps.
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ELEVATING YOUR HOME 5

Figure 5-13a through 5-13d. 

Elevating a basement or 

crawlspace foundation home 

on piers.

5-13a

5-13b 5-13c

5-13d
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5 ELEVATING YOUR HOME

Posts or Columns

For posts or columns, the home elevation process is the same as that described for piers; however, the existing 

foundation usually must be removed so that the posts or columns and their concrete encasements or pads can be 

installed. Posts are usually placed in drilled or excavated holes. Each post or column is either encased in concrete 

or anchored to a concrete footing. 

Figure 5-14 shows a home elevated on two types of post or column foundations. Because an elevated house sits 

higher off the ground on a slender foundation, the lateral (sideways) loading on the house becomes a more important factor than a house sitting only a few feet off the ground on a continuous foundation. Large lateral loads 

can be exerted on the house by forces such as wind, earthquakes, or floodwaters. Simple wooden posts will not 

likely be able to resist these lateral loads and would require a formal design by a structural engineer. Lateral bracing can be used to prevent movement of the building for occupant comfort, but it should not be used to provide 

lateral support to prevent foundation failure. Additionally, bracing in two directions is only recommended in areas 

of low velocity flooding—areas with high-velocity flooding should only be braced in one direction (as shown in 

Figure 5-14). Depending on the potential lateral loads that the house must resist, a metal framing system may be 

a more practical approach than simple wooden posts. This system may also require an extensive concrete footing 

system so that the loads can be transferred down the posts or columns and into the ground. Although this elevation technique may appear simple, you should retain the services of a structural engineer who understands how 

loads are transferred.

Figure 5-14. Home elevated on post or column foundations.
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ELEVATING YOUR HOME 5

Piles

Elevating on piles is a more involved process than elevating on piers, posts, and columns. Piles are usually driven 

or vibrated into the ground or jetted in with a high-pressure stream of water. They are not supported by concrete 

footings or pads. Unlike the construction of wall, pier, or post or column foundations, the pile-driving operation, 

which requires bulky, heavy construction machinery, cannot be carried out under a home that has been lifted on 

jacks. Instead, the home is usually lifted and moved aside until the piles have been installed. Because the existing 

foundation is not used, it must be removed. Figure 5-15 shows a home elevated on a pile foundation.

More information on elevating homes on open foundations can be found in Hurricane Sandy Fact Sheet No. 2, 

Foundation Requirements and Recommendations for Elevated Homes (FEMA. 2013c). This fact sheet addresses many of the common issues associated with elevating homes on open foundations, and also addresses elevating a home on an open 

foundation that is confined by narrow lot lines.

Figure 5-15. Home elevated 

on piles.

HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-1

6.0 Relocation and Demolition

This chapter describes two mitigation alternatives: relocation and demolition.

Relocation Demolition

These mitigation options can be more effective than other mitigation methods because they provide the opportunity to relocate or rebuild in an area outside of the floodplain. If rebuilding outside the floodplain is not possible, 

then moving to less vulnerable locations (i.e., from Zone V to a Zone A) on the same property or on a new property is also an option. If neither rebuilding outside the floodplain or in a less vulnerable location is feasible, elevation 

may be your best option. Elevation is described in detail in Chapter 5. This chapter addresses relocation outside 

of the floodplain.

Because relocation and demolition are both complex, you 

should consult design and/or construction professionals to help 

with your mitigation project.

NOTE

Always use a licensed, bonded, and 

insured contractor for relocation projects. Be sure that your contractor has 

experience with relocation projects 

and understands the considerations 

discussed in Section 6.1.1. Checking 

the contractor’s references is very 

important.

For information about home relocation 

companies, contact the International 

Association of Structural Movers at 

P.O. Box 2104, Neenah, WI 54956-

2104 (803) 951-9304, http://www.

iasm.org/.

6.1 Relocation

Relocation, or moving your home out of the flood 

hazard area, offers the best protection from flooding. It 

also can free you from anxiety about future floods and 

lower your flood insurance premiums. However, relocation usually is the most expensive of the retrofitting methods.

The relocation process involves lifting a home off its foundation, placing it on a heavy-duty flatbed trailer, hauling it to a 

new site outside the flood hazard area, and lowering it onto a 

new conventional foundation. The process sounds straightforward, but a number of considerations require careful planning.
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6 RELOCATION AND DEMOLITION

6.1.1 Considerations

Condition of Home

For a home to be picked up and moved successfully, it must be structurally sound. All the structural members and 

their connections must be able to withstand the stresses imposed when the home is lifted and moved. Before the 

home is lifted, the home moving contractor must inspect it to verify its structural soundness. A home that is in 

poor condition, especially one that has been damaged by flooding, may need so much structural repair and bracing that relocation is not be practical (see Section 6.2 for demolition).

Home Size, Design, and Shape

In general, the types of homes that are the easiest to elevate (as discussed in Section 5.1.5) are also the easiest 

to relocate: single-story, wood-frame homes over a crawlspace or basement foundation, especially those with a 

simple rectangular shape. These homes are relatively light, and their foundation design allows the home moving 

contractor to install lifting equipment with relative ease. Multistory homes and solid masonry homes are more 

difficult to relocate because their greater size and weight requires additional lifting equipment and makes them 

more difficult to stabilize during the move. Slab-on-grade foundations complicate the relocation process because 

they make the installation of lifting more difficult.

The relocation process is also more complicated for homes with 

brick or stone veneer, which can crack and peel off when disturbed. Removing the veneer before the home is moved and 

replacing it once the home is on the new foundation at the new 

site may be less expensive. For the same reason, chimneys may 

need to be removed before the move and rebuilt afterwards. 

If they are to be moved with the home, they must be braced 

extensively.

Moving Route Between Old and New Sites

Restrictions along the route to the new site can complicate a 

relocation project, especially for large homes. Narrow roads, restrictive load capacities on roads and bridges, and low clearances 

under bridges and power lines can make finding an alternative 

route necessary. When no practical alternatives are available, the 

home moving contractor may have to cut the home into sections, move them separately, and reassemble the home at the 

new site. Experienced home movers can make the cuts and reassemble the home in such a way that it will not appear to have 

ever been apart.

Disruption of Occupants

Among all the retrofitting methods, relocation is the most disruptive for the occupants of the home. Before the home can be 

lifted, all utility systems must be disconnected, and the home 

becomes uninhabitable. You cannot move back into the home 

until it has been installed at the new site and all utility systems 

NOTE

Relocation is sometimes used as an 

alternative to demolition (as described 

in Section 6.2) when a home has been 

damaged. Instead of demolishing the 

home, the owner may be able to sell 

it for salvage to a contractor, who will 

then move the home to another site, 

renovate it, and sell it. Relocation is 

also used after a community acquires 

a flood-prone property from the owner. Instead of leaving the home to be 

demolished, the owner may decide to 

keep the home and move it to property outside the flood hazard area.

CROSS REFERENCE

See Section 4.1.3 for information 

about working with local officials 

regarding flood hazards and permitting requirements in your community.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-3

RELOCATION AND DEMOLITION 6

reconnected. In the interim, you will need temporary lodgings and a place to store your furniture and other 

belongings.

6.1.2 The Relocation Process

The relocation process consists of more than lifting and moving the home. You must work with your contractor 

to select a new site for the home, and the contractor must plan the moving route, obtain the necessary permits, 

prepare the new site, and restore the old site.

Selecting the New Site

Selecting a new site for your relocated home is similar to selecting a site on which to build a new home. You need to consider 

the following:

Natural Hazards – Remember that the goal of relocating is to 

move your home to a site that will be safe from flooding and 

other natural hazards. Before buying new property, check with 

local officials about the flood, wind, and earthquake hazards at 

any new site you may be considering (see Section 4.1.3).

Utilities – Determine what steps you need to take to install new 

utility systems and to have utility lines extended to your new 

site. Consider electrical, gas, water and sewer, telephone, and cable TV services. Your community will probably require that your 

new utility systems meet current code requirements. Regardless 

of these requirements, you should consider upgrading one or 

more of your utility systems to provide more energy-efficient 

service.

Accessibility – Your new site must be accessible to the home movers and to the construction crews that will prepare the site and build the new foundation for your home. The more difficult it is for contractors to reach and 

work at your new site, the more expensive your relocation project is likely to be. If extensive grading and clearing 

are necessary for adequate access, some of the characteristics that made the site attractive to you may be diminished. Your existing site may also present some accessibility issues if your home has a cistern or septic tank system 

installed on the property. If these need to be detached from your home and installed at the new project site, additional time and cost may be involved. 

Another important consideration regarding accessibility is the difficulty of moving the home to the new site. 

In determining the best route between the old and new sites, the moving contractor must anticipate potential 

problems. For example, the routing of the home may be impeded by narrow bridges and road cuts, bridges with 

low weight limits, low-hanging utility lines and traffic signals, low underpasses, tight turns, road signs, and fire 

hydrants.

The moving contractor should also coordinate any special services that may be required to deal with obstacles, 

such as raising traffic lights, relocating signs, and constructing temporary bridges. Utility lines can usually be 

raised temporarily during the move, but utility companies often charge for this service. In some cases, it may be 

possible to avoid some obstacles by choosing an overland (non-road) travel route.

WARNING

Regardless of the age of your home, 

you may be required by local regulations to bring it up to current code 

when you move it to a new site. This 

requirement could affect not only the 

home but also its utility systems. You 

should check with your local officials 

about such requirements before you 

decide to relocate.
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6 RELOCATION AND DEMOLITION

Permitting

You or your moving contractor must obtain permits to move the home on public roads or other rights-of-way. 

These permits may be required by local governments, highway departments, and utility companies, not only in 

the jurisdiction from which your home is being moved, but also any jurisdiction through which the home will 

pass. If the moving route crosses or affects private land, you may need to obtain the approval of the landowner.

Obtaining the necessary permits and approvals may be a lengthy and complex process, and you may find that the 

requirements vary from jurisdiction to jurisdiction and agency to agency. So it is extremely important that you, 

your design professional, and your moving contractor investigate the need for permits and approvals before you 

make a final decision to relocate.

You or your design professional should check with local officials to make sure that, when your home is moved to 

the new site, it will conform to all zoning requirements and building codes in effect at the time of the relocation. 

The design professional should also determine the local design standards and permitting requirements that govern 

the development of your new site. All permits required for construction at the new site, moving your home, and 

restoring the old site after the home is moved should be obtained before the relocation project begins.

Preparing the New Site

Before the home is moved, the new foundation must be designed and is usually partially constructed. The foundation will 

be completed after the home is brought to the site. Clearing, 

excavation, and grading are necessary to allow construction 

to begin and to ensure that the home can be maneuvered on 

the site. Also, unless already available, utility service must be 

brought into the site so that there will be no delay in connecting them to the home and making it habitable. Figure 6-1 shows 

a new slab-on-grade foundation that is being constructed for a 

relocation project.

CROSS REFERENCE

Refer to Section 5.2 for a description of 

how homes on various types of foundations are lifted off their foundations.

Figure 6-1. New foundation 

is being prepared (photo 

courtesy of Wolfe House 

Movers).
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RELOCATION AND DEMOLITION 6

Lifting the Home

In general, the steps required to lift a home off its foundation are the same as those described in Section 5.2.1 for 

elevating a home on extended foundation walls. As described in Section 5.2.2, the steps to lift homes on basement 

and crawlspace foundations differ from those for homes on slab-on-grade foundations.

Homes on basement and crawlspace foundations are separated from their foundations and lifted on steel I-beams 

that pass through the foundation walls directly below the floor framing. The lifting is done with hydraulic jacks 

placed directly under the I-beams. The process for homes on slab-on-grade foundations is similar. However, because these homes are lifted with the concrete floor slab attached, the I-beams are inserted below the slab. Figures 

6-2 through 6-5 show the basic steps for lifting a home.

Figure 6-2. Clearing 

pathways beneath the 

structure for lifting supports 

(photo courtesy of Wolfe 

House Movers).
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6 RELOCATION AND DEMOLITION

Figure 6-3. Pathways for 

lifting beams (photo courtesy 

of Wolfe House Movers).

Figure 6-4. Beams supported 

by cribbing are placed at 

critical lift points (photo 

courtesy of Wolfe House 

Movers).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-7

RELOCATION AND DEMOLITION 6

Figure 6-5. Hydraulic jacks 

lift the structure, and the 

home is separated from 

existing foundation (photo 

courtesy of Wolfe House 

Movers).

Moving the Home

After the home is lifted, the moving contractor performs the grading and excavation necessary to create a temporary roadway that will allow the home to be moved to the street. The area beneath the home must be leveled and 

compacted so that trailer wheel sets can be placed under the home (Figure 6-6). The wheel sets and lifting beams 

form the trailer on which the home will be moved.

Figure 6-6. Trailer wheel sets 

are placed beneath the lifting 

beams (photo courtesy of 

Wolfe House Movers).
6-8 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

6 RELOCATION AND DEMOLITION

After the wheels are attached, a tractor or bulldozer tows the home to the street. As the home is being moved, 

workers continually block the wheels to prevent sudden movement. At the street, the home is stabilized, the trailer 

is attached to a truck, and the move to the new site begins (Figure 6-7).

Figure 6-7. The move to 

the new site begins (photo 

courtesy of Wolfe House 

Movers).

At the new site, the moving contractor positions the home over the partially completed foundation and supports 

the home on cribbing so the trailer wheels can be removed. As in the home elevation process described in Chapter 

5, the home is lifted on hydraulic jacks to the desired height and the foundation is completed below it. The home 

is then lowered onto the foundation, all utilities are connected, and any necessary backfilling and landscaping is 

completed (Figure 6-8).

Figure 6-8. House is 

lowered and connected 

to the foundation after 

the foundation is fully 

constructed (photo courtesy 

of Wolfe House Movers).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-9

RELOCATION AND DEMOLITION 6

Restoring the Old Site

After the home is moved, the old site must be restored according to the local regulations. Restoring the site usually involves 

demolishing and removing the old foundation and any pavement, such as a driveway or patio; backfilling an old basement; 

removing all abandoned utility systems; grading to restore areas 

disturbed by demolition; and stabilizing the site with new vegetation. Permits are normally required for demolition, grading, 

and vegetative stabilization.

If your old site included a septic tank or fuel storage tank, you 

may have to meet the requirements of environmental regulations 

aimed at preventing contamination of groundwater. Depending 

on the age and condition of the tank, you may be required to 

drain and remove it. If it is an underground tank, you may have 

to drain it and anchor it to prevent flotation. You may also be 

required to test the soil around an underground fuel tank to 

determine whether leakage has occurred. As the homeowner, 

you will usually be responsible for cleaning contaminated soil if 

there has been any leakage from the tank. In this situation, you 

will need the services of a qualified geotechnical or environmental engineer.

Local utility companies or regulatory officials can inform you 

about requirements concerning capping, abandoning, or removing various utility system components.

6.2 Demolition

Demolition is tearing down a damaged home and either rebuilding a compliant home on the same 

property, rebuilding a compliant home on new property, or moving into another structure. This 

retrofitting method may be the most practical of all those described in this guide when a home has sustained extensive damage, especially severe structural damage. 

If a flood-prone home has been severely damaged, because of 

flooding or any other cause, demolition can be practical and 

effective. Demolition may also be practical for an undamaged 

home that, because of deterioration over time or for other reasons, is not worth retrofitting with any of the other methods 

described in this guide. If you choose demolition, you will tear 

down your damaged home and either rebuild a compliant home 

on the same property or elsewhere outside the floodplain. If you 

decide not to rebuild, your State or local government may buy 

or acquire your property. Depending on your choice of a site 

for your new home, this method can lower or even eliminate 

your flood insurance premiums. If you decide to rebuild, your 

NOTE

Always use a licensed, bonded, and 

insured contractor for demolition 

projects and for reconstruction projects. Be sure that your contractor has 

experience with demolition (and construction for mitigation reconstruction) 

and understands the considerations 

discussed in Section 6.2.1.

NOTE

Many homeowners have sold or 

deeded vacated flood-prone properties to local municipalities for use as 

parkland or open space.

DEFINITION

Acquisition is the process by which 

your State or local government purchases your flood-prone property, 

demolishes the building, and maintains the land as an open space.
6-10 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

6 RELOCATION AND DEMOLITION

mitigation reconstruction project may be eligible for FEMA 

grant money (see Section 2.6.1).

The demolition process involves disconnecting and capping 

utility lines at the damaged home, tearing the home down, 

removing debris and otherwise restoring the old site, and building or buying a new home. The most important considerations 

relate to how badly your home has been damaged and your options of building or buying a new home.

6.2.1 Considerations

Amount of Damage

Demolition is more practical for severely damaged homes than for those with little or no damage. If a flood, fire, 

earthquake, hurricane, or other disaster has caused extensive damage to the interior and exterior of your home 

or left it structurally unsound, you will probably find that demolishing the home and rebuilding it is easier than 

making all of the necessary repairs. Also, remember that a severely damaged home in the regulatory floodplain will 

almost surely be considered Substantially Damaged under your community’s floodplain management ordinance, 

regulation, or provisions of the building code. Salvaging such a home would require repairing the damage and 

elevating the home (including backfilling a basement); wet floodproofing areas used only for parking, building 

access, or storage; or relocating the home as described in Section 6.1.

Rebuilding or Buying Another Home

After demolishing your home, you may buy or build a home elsewhere or, in some cases, rebuild on your existing 

property at an elevation above the BFE. Regardless of your decision, your goal is to greatly reduce or eliminate the 

potential for damage from floods, earthquakes, high winds, and other hazards. If you buy or build a home elsewhere, you’ll want to find a site that is outside the regulatory floodplain, ideally one that is well above the BFE. You 

should also check with your local officials about other hazards before you make your final decision.

If you demolish your existing house and plan to relocate elsewhere, you will need to think about what to do with 

the existing property (land). Property that is entirely within the regulatory floodplain may be difficult to sell because of restrictions on its use. Your community may be interested in acquiring your property and then converting 

it to a public use, open space area. If you receive a FEMA grant to buy out your property then the land will most 

likely be deeded to the community and its use will be restricted to open space. As explained in Section 2.6, some 

Federal programs provide grants to States and communities that they can use to buy flood-prone homes and properties. State and local programs may also provide financial assistance. Check with your local officials about these 

programs.

When buying or building a home elsewhere is too expensive, you may be able to rebuild on your existing property, either on the site of your old home or, preferably, on a portion of your property that is outside the regulatory 

floodplain. If you rebuild on the site of your old home, your community’s floodplain management ordinance, 

regulation, or provisions of the building code will require that the lowest floor be at or above the BFE. How you 

meet this requirement depends on the flood zone and code requirements of your community. An important disadvantage of this approach is that you may not have access to your home during floods. 

If your existing property includes a large enough area outside the regulatory floodplain, a better choice is to rebuild there. Building outside the floodplain gives you greater freedom to build the type of home you want. Also, 

DEFINITION

Mitigation reconstruction is the 

construction of an improved, elevated building on the same site where 

an existing building and/or foundation 

has been demolished.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 6-11

RELOCATION AND DEMOLITION 6

because both the home and property are outside the floodplain, restricted access during flooding is less likely 

to be a problem. Remember that floods do not follow the lines on FIRMs, so although building outside of the 

floodplain may not involve insurance implications, building high is safer and smarter. Property owners outside of 

high-risk flood areas file over 20 percent of NFIP claims and receive one-third of disaster assistance for flooding. 

Disruption of Occupants

Like relocation, demolition can be disruptive for the occupants of the home. Unless you decide to buy an existing 

home elsewhere, you must find a place to live and to store your furniture and belongings while your new home 

is being built.

Permitting

You or your design professional or contractor must check with local officials regarding permitting requirements 

for the necessary work. All permits for demolition should be obtained before the demolition process begins, including disconnecting and capping utilities, disposing of debris, new construction, and restoration of the old site.

6.2.2 The Demolition Process

Tearing Down the Old Home

Your utility companies must first turn off all services to the home. Your demolition contractor will then disconnect the utility lines. If you do not plan to rebuild on the same site, the contractor will cap the lines permanently 

or remove them according to the requirements of the utility companies. Before demolition begins, environmental hazards, such as asbestos, must be abated in accordance with Federal, State, and local requirements. Typically, 

the demolition contractor will bulldoze the home and then dispose of the resulting debris as required by Federal, 

State, and local regulations. 

Restoring the Old Site 

If you are not rebuilding on the old site, it must be restored according to the requirements of local regulations. 

Site restoration usually involves demolishing and removing not only the home, but also any pavement, such as a 

driveway or patio; grading to restore areas disturbed by the demolition; and stabilizing the site with grass.

If your old site included a septic tank or fuel storage tank, you may have to meet the requirements of environmental regulations aimed at preventing contamination of groundwater. You may be required to drain and remove 

aboveground and underground storage tanks, or you may have to anchor them to resist flotation. You may also be 

required to test the soil around an underground tank to determine whether leakage has occurred. As the homeowner, you will usually be responsible for cleaning contaminated soil if there has been any leakage from the tank. 

In this situation, you will need the services of a qualified geotechnical or environmental engineering firm.

Local utility companies or regulatory officials can inform you about requirements concerning capping, abandoning, or removing various utility system components.
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6 RELOCATION AND DEMOLITION

Rebuilding – Mitigation Reconstruction

Your construction contractor will prepare the site and build 

your new home according to the local building code, floodplain management, and zoning requirements. The lowest floor 

of your new home must be at or above the BFE, so your new 

home cannot include a basement. Figure 6-9 shows a mitigation 

reconstruction project that was recently completed in Louisiana 

following Hurricane Katrina.

Depending on where you decide to rebuild, local utility companies may have to extend new lines onto the site 

of your new home. This is usually done before construction is completed and your contractor will hook up the 

utility lines as part of construction. You may need the services of a design professional if specialized utility 

systems are required because of the location of your site, the type of home you decide to build, or the nature of 

the hazards at the site.

WARNING

If you rebuild on the site of your old 

home, your community’s floodplain 

management ordinance, regulation, 

or provisions of the building code will 

not allow you to have a basement below the BFE.

Figure 6-9. Typical mitigation 

reconstruction project. 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 7-1

7.0 Floodproofing

This guide describes two types of floodproofing: wet and dry. As 

its name implies, wet floodproofing allows floodwaters to enter the enclosed areas of a home. In contrast, dry floodproofing 

prevents the entry of floodwaters. Because both approaches rely 

on varying philosophies of managing flood waters, this chapter 

separates the approaches and mitigation methods. 

7.1 Wet Floodproofing

The benefit of wet floodproofing is that, if floodwaters 

are allowed to enter the enclosed areas of the home 

and to quickly reach the same level as the floodwaters 

outside, the effects of hydrostatic pressure, including 

buoyancy, are greatly reduced. As a result, there are equalized 

loads imposed on the home during a flood and the likelihood 

of structural damage may be greatly reduced. Wet floodproofing 

is generally used to limit damages to enclosures below elevated 

buildings, walkout-on-grade basements, below-grade basements, crawlspaces, or attached garages. It is not practical for 

these areas to be used as living space, and, if the home is being 

Substantially Improved or has been Substantially Damaged, wet 

floodproofing can lead to NFIP compliance only if (1) the area 

is limited to parking, access, or storage, (2) designed to allow 

for automatic entry and exit of flood waters through the use of 

flood openings, and (3) uses only flood damage-resistant materials below the DFE.

Successful wet floodproofing involves the following:

n Ensuring that floodwaters enter and exit the home’s 

enclosed area (for NFIP compliance, floodwaters must 

exit the enclosed area automatically, without the use of 

pumps)

WARNING

If your home is being Substantially 

Improved or has been Substantially 

Damaged, your community’s floodplain management ordinance or 

regulations will restrict the use of wet 

floodproofing to attached garages and 

enclosed areas below the BFE that 

are used solely for parking, building 

access, or storage. For more information, refer to NFIP Technical Bulletin 

7, Wet Floodproofing Requirements 

(1993).

WARNING

Non-compliant wet floodproofing a 

residence will not reduce the flood insurance premium.

NOTE

Flood damage-resistant materials are 

discussed later in this chapter.
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7 FLOODPROOFING

n Ensuring that floodwaters inside the home rise and fall at the same rate as floodwaters outside the home

n Reducing damage caused by contact with floodwaters to areas of the home that are below the flood level 

n Protecting service equipment inside and outside the home 

n Relocating high-value contents stored below the DFE

This chapter describes the modifications that must be made to a home as part of a wet floodproofing project and 

the most important considerations for this retrofitting method. Protection of service equipment is discussed in 

Chapter 9.

7.1.1 Design Flood Elevation

All construction and finish materials in the areas of the home that 

will be allowed to flood should be resistant to damage caused by 

direct, and possibly prolonged, contact with flood-water. Areas 

used for living space typically contain floor and wall coverings 

and other finishing materials, furniture, appliances, and items 

that could be easily damaged by floodwater and expensive to 

clean, repair, or replace. Therefore, wet floodproofing is practical 

only for portions of a home that are not used for living space, 

such as a basement, walkout-on-grade basement, crawlspace, 

non-air-conditioned porch, or attached garage. As shown 

in Figure 7-1, the lowest floor should be at or above the DFE 

(including freeboard) for wet floodproofing.

If your DFE is above the elevation of your lowest finished floor, you should consider one or more of the other retrofitting methods described in this guide, such as elevation (Chapter 5). As you review Chapter 5, note that most 

of the elevation methods incorporate the principles of wet floodproofing. Elevation raises the living space above 

the flood level and allows floodwaters to enter the enclosed areas of the home below the living space if those areas 

have been retrofitted for compliance.

7.1.2 Hazards

Wet floodproofing protects a home from the effects of hydrostatic pressure but not from other flood hazards, such 

as the hydrodynamic force of flowing water, erosion and scour, saturation of building elements, damage to contents, the impact of ice and other floodborne debris, and damage from floodborne contaminants. If you have seen 

evidence of these hazards in past floods in your area, or if your community officials confirm that your home may 

be affected by these hazards, you should consider an alternative retrofitting method, such as relocation (Chapter 

6) or elevation on an open foundation (Chapter 5). Wet floodproofing a home does not change its vulnerability 

to damage from high winds or earthquakes. 

NOTE

Always consult a licensed, bonded, 

and insured contractor before initiating a wet floodproofing project. Be 

sure that your contractor has experience with wet floodproofing and 

understands the considerations discussed in Section 7.1.
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FLOODPROOFING 7

7.1.3 Post-Flood Cleanup

Remember that floodwater is rarely clean and may pose other 

safety hazards to occupants and contractors. Use caution when 

entering a recently flooded home; watch for structural instability or shifted contents as well as displaced animals. There are 

three important principles to follow when you first return to a 

flooded home before beginning repairs:

1. Personal Safety

Flooded buildings pose a number of health and safety risks, for 

both individuals who wish to maintain occupancy and those 

who work to repair the buildings. Eliminating hazards is the 

best way to protect occupants and workers; until conditions can 

NOTE

If more than 10 square feet are affected by mold, you should contact a 

mold cleanup professional. For more 

information about mold prevention 

and remediation, visit the Center for 

Disease Control’s (CDC’s) mold Web 

site at http://www.cdc.gov/mold.

Figure 7-1. Typical wet 

floodproofing.
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7 FLOODPROOFING

be returned to normal, anyone working in a flooded building should use appropriate personal safety equipment 

and take appropriate safety precautions. 

Mold: The Occupational Safety and Health Administration (OSHA) Fact Sheet, Hurricane Sandy Cleanup PPE Matrix 

(OSHA-FS-3612, 2012), provides information on personal protective equipment. Anyone entering a house with 

visible mold growth should wear a disposable suit, rubber gloves or other hand protection, and respiratory protection. The OSHA Fact Sheet, Mold Hazards During Hurricane Sandy Cleanup (OSHA-FS-3619, 2012), provides information 

on mold.

Asbestos and Lead Paint: Asbestos in floor tile, pipe and boiler installation, and electrical wiring is common in 

many homes built before 1980. Breathing asbestos fibers released from building products can increase the risk of 

cancer and cause a number of serious lung diseases. Paint in homes constructed prior to 1978 may contain lead. 

If asbestos or lead paint is suspected, obtain the services of a specialist to perform material testing, and do not 

disturb the material until testing has been completed. If testing confirms the presence of lead, remediation should 

be conducted by a licensed professional in accordance with State and Federal regulations. 

2. Cleaning Flood Damaged Homes to Prepare for Repair and Reconstruction

All objects that came into contact with the floodwater should be 

cleaned and sanitized. Water-damaged porous materials are difficult to properly clean and should be discarded.

Move out: Remove salvageable contents that were not affected 

by the water; dispose of all saturated porous materials, such as 

mattresses or upholstery.

Tear out: Remove all water-damaged interior finishes, including wet carpet and padding, curled vinyl tiles and linoleum, 

saturated drywall and plaster, saturated wall insulation, flooded 

electrical receptacles, and swollen wall paneling.

Barriers: Place plastic barriers between affected and unaffected 

areas of the building (typically between the first and second 

floors at the base of the stairs) to reduce the potential of mold 

spores spreading to unaffected areas. 

Application of Cleaners: Cleaners are most efficiently applied using a combination of foam cleaning processes 

and brush cleaning, followed by pressure washing. Foam cleaning processes allow the product to stay on the 

surface long enough for the chemicals to kill the mold or bacteria and makes drying easier. Brushes improve decontamination of wooden studs and other surfaces by scrubbing the foam into affected surfaces. Water-damaged 

porous materials should be removed. Care should be taken to inspect both the front and back side of the nonflooded gypsum wall board and plaster walls for remaining dirt and mold to ensure all affected areas are cleaned. 

Pressure Washing: The fastest and most efficient rinse tool, which minimizes the amount of water used to remove residual foam from wall studs, floor joists, and other surfaces, is a residential-type pressure washer set at low 

pressure so that the spray is a light mist. 

WARNING

Although bleach is an inexpensive 

and convenient cleaning agent, it has 

many serious drawbacks when used 

to clean flood-impacted materials. It is 

not effective on porous materials, such 

as gypsum wall board or as a disinfectant on surfaces with residual dirt 

and can corrode electrical and metal 

components of mechanical systems. 

Do NOT combine chlorine bleach 

and ammonia, as the combination of 

chemicals will release vapors that can 

be extremely toxic or even fatal.
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FLOODPROOFING 7

Cleaning Crawlspaces: Removing the flooring is the simplest way to enter crawlspaces to decontaminate these 

areas. Solid contaminants should be removed from under the building, along with any remaining water. All exposed sides of floor joists, foundation walls, and remaining structural elements should be cleaned with cleaning 

foam and brushing. 

Cleaning in Weather Extremes: Although cold weather poses challenges for restoring flooded buildings, it also has some 

advantages. Cooler weather slows down the spread of mold. 

However, buildings need to be warmed to 50° to 75°F to provide for worker comfort, improve the effectiveness of cleaning 

and sanitizing agents, and allow commercial drying equipment 

to operate efficiently. Mold and bacteria spread more quickly in 

hot and humid weather, slowing natural drying of flooded and 

contaminated building elements; in such circumstances, the use 

of drying equipment is critical to lower the moisture content of 

structural materials prior to rebuilding or repair. 

3. Proper Drying Prior to Rebuilding

After the cleaning process has been completed, the building 

and any salvageable contents need to dry. Failure to allow adequate drying prior to reconstruction can trap moisture in the 

building, which can cause fungal growth and potential health 

problems. Once the electrical and HVAC systems have been restored and sanitized, the moisture content of wetted salvageable 

building materials should be checked to determine whether 

drying equipment, such as fans and dehumidifiers, is necessary. 

For more information about restoring flooded buildings or initial precautions to be taken when entering flooded buildings, 

refer to the Hurricane Sandy Recovery Fact Sheet Number 1, 

Cleaning Flooded Buildings (FEMA. 2013a)1

. 

FEMA P-942, Hurricane Sandy in New Jersey and New York (FEMA. 2013d) provides a comprehensive assessment of building material performance and mitigation actions appropriate to flooded homes, other structures, and infrastructure. 

7.1.4 Modifications Required for Wet Floodproofing

Wet floodproofing requires a variety of modifications to your home, including its walls, construction and finishing materials, and service equipment. Consult with a design professional or licensed contractor before you make 

any modifications.

7.1.5 Installing Openings

The most important part of a wet floodproofing project is installing wall openings that allow the entry and exit of 

floodwaters. The openings must be installed in foundation walls and in garage walls as appropriate, below the expected flood level (Figure 7-2). The goal is not simply to allow the entry and exit of floodwaters, but also to ensure 

1 The fact sheet is part of FEMA’s Hurricane Sandy Recovery Advisory and Fact Sheet technical series and can be downloaded at 

http://www.fema.gov/hurricane-sandy-building-science-activities-resources

CROSS REFERENCE

For more information about openings 

requirements for wet floodproofing, 

refer to NFIP Technical Bulletin 1, 

Openings in Foundation Walls and 

Walls of Enclosures (2008), and 

FEMA P-259, Engineering Principles 

and Practices for Retrofitting FloodProne Residential Structures (FEMA. 

2012a).

WARNING

Failure to allow adequate drying prior 

to reconstruction can trap moisture in 

the building, which can cause future 

fungal growth and potential health 

problems. 
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7 FLOODPROOFING

that the water level inside the home rises and falls at roughly 

the same rate as the water level outside so that hydrostatic pressures inside and outside are continuously equalized. As shown 

in Figure 7-2, large differences in the interior and exterior water levels allow unequalized hydrostatic pressures and, therefore, 

defeat the purpose of wet floodproofing. Figure 7-3 illustrates 

typical enclosures with flood openings.

For equal water levels to be maintained, both the size and number of openings must be adequate. Otherwise, when floodwaters 

are rising and falling, water will not be able to flow into or out 

of the home fast enough. The number of openings required and 

their size will depend on the rate of rise and the rate of fall of 

the floodwaters (see Chapter 2) and on the size of the area that 

is being allowed to flood. In general, the faster the rates of rise 

and fall and the larger the flooded area within the home, the 

greater the number and size of openings required.

NOTE

If you cover wall openings with louvers or screens, keep in mind that, 

the more restrictive they are, the more 

likely they are to become clogged 

with debris during floods and prevent 

the flow of floodwaters. Make sure 

that any screens or louvers allow the 

passage of water that contains suspended sediment and other small 

debris. After floodwaters have receded, screens and louvers must be 

cleaned of any debris that may have 

accumulated.

Figure 7-2. Wall openings 

must allow floodwaters not 

only to enter the home, but 

also to rise and fall at the 

same rate as floodwaters 

outside the home.

Figure 7-3. Sketch of foundation plan of home with multiple enclosed areas, each with flood openings. Typical enclosures 

with flood openings (Left). Flood opening in typical crawlspace foundation (Right).
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FLOODPROOFING 7

If you are wet floodproofing areas below the BFE in a Substantially Improved or Substantially Damaged home, 

your community’s floodplain management ordinance or regulation will require you to install openings in the exterior walls of all enclosed areas below the BFE (see Section 3.1.1). The minimum requirements are:

n You must provide at least two wall openings for each enclosed area—one in each of two different walls. 

In other words, you cannot put both openings in the same wall.

n If your home has more than one enclosed area, you must install openings in the exterior walls of each enclosed 

area so that floodwaters can enter directly from the outside.

n The total area (size) of all openings for each enclosed area must equal at least 1 square inch for every 

square foot of floor space in the enclosed area. For example, if the enclosed area is 25 feet by 40 feet 

(1,000 square feet), the total net area of the openings must be at least 1,000 square inches, or roughly 

7 square feet. In this example, you could meet the size requirement by providing two 31⁄2-square-foot 

openings or several smaller openings whose total net area equals 7 square feet.

n The bottom of each opening must be no higher than 1 foot above the higher of the exterior grade or 

interior grade directly below the opening.

n Floodwaters must be able to flow in and out of enclosed areas automatically. If you place louvers, screens, 

or other types of covers over the openings (which many homeowners do to prevent animals from 

entering the enclosed areas), they must not block the flow of water. Note that the area of any screens 

or louvers covering the openings must be subtracted from the gross opening area. Because the need 

for human intervention reduces the reliability of wet floodproofing, you may not install any type of 

electrical-, mechanical-, or manual-operated cover.

n Flood openings must be entirely below the BFE.

FEMA developed these requirements to provide homeowners with a straightforward means of determining where 

and how to install wall openings without the aid of an engineer or design professional. The requirements provide 

a margin of safety for wet floodproofed homes subject to flooding with rates of rise and fall as high as 5 feet per 

hour. If you wish to install openings that do not meet one or more of the requirements listed above, your design must be certified by a registered engineer or other licensed design professional and approved by your local 

officials. See FEMA’s NFIP Technical Bulletin 1, Openings in Foundation Walls and Walls of Enclosures (2008), for more information about openings requirements.

7.1.6 Protecting the Underside of Elevated Buildings

The undersides of elevated coastal buildings are typically covered with vinyl or aluminum soffits or plywood 

sheathing to protect insulation and metal floor system connectors. The undersides of these buildings are often 

damaged by high hurricane force winds, allowing water to be driven into the building. Lost paneling or sheathing can become wind-borne debris, increasing the risk of damage. How the space below the building is designed 

and built is determined by local floodplain regulations and building codes, which may include fire resistant-rated 

building materials, depending on the use of the underneath space (parking, storage areas). 

Underside materials should meet flood damage-resistant requirements outlined in NFIP Technical Bulletin 2, Flood 

Damage-Resistant Materials Requirements (2008), and local code requirements, including fire resistance requirements 

where applicable. In coastal areas, make sure to use corrosion-resistant fasteners to secure the underside materials. 

Wind loads based on wind speed maps for the area where the building is located must be included in the underbuilding wind protection assembly design. To ensure the assembly is effective, a licensed engineer or architect 

should prepare the design in accordance with Hurricane Isaac Recovery Advisory 1 (see Cross Reference). 
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7 FLOODPROOFING

7.1.7 Using Flood Damage-Resistant Materials

In the areas below the anticipated flood level, any construction 

and finishing materials that could be damaged by floodwaters 

must be either removed or replaced with flood damage-resistant 

materials as required by your community’s floodplain management ordinance or regulations. Vulnerable materials include 

gypsum wall board (also called dry wall), blown-in and fiberglass batt insulation, carpeting, and non-pressure-treated wood 

and plywood. Flood damage-resistant materials are those that 

can be inundated by floodwaters with little or no damage. They 

include such materials as concrete, stone, masonry block, ceramic and clay tile, pressure-treated and naturally decay-resistant 

lumber, epoxy-based paints, and metal. In addition to resisting 

damage from floodwaters and their contaminants, these materials are relatively easy to clean after floodwaters recede. 

Table 7-1 lists materials that are acceptable and unacceptable 

for use in wet floodproofing projects. NFIP Technical Bulletin 

2, Flood Damage-Resistant Materials Requirements (2008), offers more 

complete guidance on materials that can and cannot be used to 

wet floodproof an area below the DFE. Consult a design professional before selecting materials to wet floodproof any areas in 

your home.

CROSS REFERENCE

For more information about flood damage-resistant materials, refer to NFIP 

Technical Bulletin 2, Flood DamageResistant Materials Requirements

(2008). This bulletin includes a detailed list of common floor, wall, and 

ceiling materials categorized according to their applicability for use in areas 

subject to inundation by floodwaters.

CROSS REFERENCE

For more information about openings 

protecting the underside of elevated buildings, refer to Hurricane Isaac 

Recovery Advisory 1, Minimizing 

Wind and Water Intrusion by Covering 

the Underside of Buildings (FEMA. 

2012c).
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FLOODPROOFING 7

Table 7-1. Flood Damage-Resistant Materials

Material Type Acceptable Unacceptable

Structural Flooring Materials • Concrete

• Naturally decay-resistant lumber

• Pressure-treated plywood

• Engineered wood or laminate 

flooring

• Oriented-strand board (OSB)

Finish Flooring 

Materials

• Clay tile

• Ceramic or porcelain tile

• Terrazzo tile

• Vinyl tile or sheets

• Engineered wood or laminate 

flooring

• Carpeting

• Wood flooring

Structural Wall and Ceiling Materials • Brick face, concrete, or concrete 

block

• Cement board / fiber-cement board

• Pressure-treated plywood

• Solid, standard structural lumber 

(2x4)

• Non-paper-faced gypsum board

• Fiberglass insulation

• Paper-faced gypsum board

• OSB

Finish Wall and Ceiling Materials • Glass blocks

• Metal cabinets or doors

• Latex paint

• Wood cabinets and doors

• Non-latex paint

• Particleboard cabinets and doors

• Wallpaper

7.1.8 Protecting Service Equipment

When you wet floodproof a home, you should also protect the service equipment below the anticipated flood 

level, both inside and outside the home in accordance with NFIP requirements. Service equipment includes utility 

lines, heating ventilation and air conditioning (HVAC) equipment, ductwork, hot water heaters, and large appliances. Chapter 9 describes a variety of methods you can use to protect interior and exterior service equipment.

7.2 Dry Floodproofing

Dry floodproofing involves completely sealing the exterior of a building to prevent the entry of floodwaters. Unlike wet floodproofing (Section 7.1), which allows water to enter the building through 

wall openings, dry floodproofing seals all openings below the flood level and relies on the walls of 

the building to keep water out. Even if your home is dry floodproofed, water can still seep through 

small openings in the sealant system or through the gaskets of shields that are protecting openings (doors and 

windows). Internal drainage systems, utilizing sump pumps, are required to remove any water that has seeped 

through and to remove water collected from any necessary underdrain systems in the below-grade walls and floor 

of the home. 
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7 FLOODPROOFING

Because the walls are exposed to floodwaters and the pressures 

they exert, dry floodproofing is practical only for homes with 

walls constructed of masonry or poured concrete and only 

where flood depths are low (typically no more than 2 to 3 feet). 

Successful dry floodproofing involves the following:

n Sealing the exterior walls of the home

n Covering openings below the flood level

n Protecting the interior of the home from seepage

n Protecting service equipment outside the home

The following sections discuss the most important considerations 

regarding dry floodproofing and describe the modifications that 

must be made to a home as part of a dry floodproofing project. 

Protection of service equipment is discussed in Chapter 9.

7.2.1 Considerations

Flood Depth

The primary consideration in dry floodproofing, and the one 

that imposes the greatest limitations on the application of this 

method, is the effect of hydrostatic pressure. Because dry floodproofing prevents water from entering the home, the external 

hydrostatic pressure exerted by floodwaters is not countered by 

an equal force from water inside the home (see Chapter 2). 

This external pressure results in two significant problems: heavy 

unequalized loads on the walls of the home and buoyancy, or 

uplift force, which acts on the entire home.

When water rises against a wall, it pushes laterally against the 

wall. As the depth of water increases, so does this force, as indicated by the arrows in Figure 7-4. Tests performed by the USACE2

indicated that, on a test subject, the maximum allowable flood 

depth for masonry and masonry veneer walls was approximately 3 feet. In these tests, walls exposed to greater depths of water 

either collapsed or suffered serious structural damage. These 

tests only addressed flood loads on the house and did not expose the house to wind loads. Additionally, the tests represented 

one flood event and the test procedures did not address the impact of similar flood loads on the longevity of the house or its ability to resist future flood events. Masonry veneer 

is not allowed by design standards to be considered as a material to resist lateral loads, such as flood loads. Houses 

should not be considered resistant to increased or high loads (such as lateral loads from floodwaters) because of 

the presence of a masonry veneer alone.

2 The test results are documented in the following reports published by the USACE National Flood Proofing Committee: Flood 

Proofing Tests – Tests of Materials and Systems for Flood Proofing Structures, August 1988; Systems and Materials to Prevent 

Floodwaters from Entering Buildings, May 1985; Structural Integrity of Brick-Veneer Buildings, 1978; Tests of Brick-Veneer Walls 

and Closures for Resistance to Floodwaters, May 1978.

WARNING

Dry floodproofing cannot be used 

to bring a Substantially Improved or 

Substantially Damaged home into 

compliance with the requirements 

of your community’s floodplain management ordinance or regulation. In 

addition, dry floodproofing measures 

can fail during larger flood events.

WARNING

The flood depth limits discussed 

here are provided as general guidelines only. Before you attempt to dry 

floodproof your home, a design professional, such as a structural engineer, 

must inspect it to determine whether 

it is structurally sound and able to resist increased flood loads expected as 

a result of dry floodproofing. Design 

professionals familiar with dry floodproofing techniques and technologies 

should design the dry floodproofing 

system so that the building’s load capacities can be properly addressed. 
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FLOODPROOFING 7

Hydrostatic pressure is exerted not only by floodwater, but also 

by soils saturated by floodwaters. As a result, basement walls can 

be subjected to pressures much greater than that from 3 feet of 

water alone (Figure 7-4). These pressures can easily cause basement walls to buckle inward or collapse (Figure 2-8). For this 

reason, dry floodproofing in basements is strongly discouraged. In fact, your community’s floodplain management ordinance or regulation does not allow basements 

in Substantially Improved or Substantially Damaged homes to be dry floodproofed.

As shown in Figure 7-4, water and saturated soils also push up 

from below the home. The buoyancy force resulting from flood 

depths of over 3 feet can separate a dry floodproofed home 

from its foundation and buckle concrete slab floors in dry floodproofed slab-on-grade homes.

The degree of danger posed by buoyancy depends on the flood depth, the type of soil at the home site, how saturated the soil is, the duration of the flood, whether the home has a drainage collection and disposal system, and 

how well that system works. Only an experienced engineer can evaluate these factors.

CROSS REFERENCE

For additional information about dry 

floodproofing techniques, refer to NFIP 

Technical Bulletin 3, Non-Residential 

Floodproofing – Requirements and 

Certification (1993), and FEMA 

P-259, Principles and Practices for 

Retrofitting Flood-Prone Residential 

Structures (2012).

Figure 7-4. The lateral and 

buoyancy force resulting 

from the same depth of 

flooding is much less on a 

home without a basement 

(a) than on a home with a 

basement (b). The pressure 

on basement walls is caused 

by water and saturated soils.

Flow Velocity, Erosion and Scour, Debris Impact, and Wave Action

Dry floodproofing does not protect a home from the hydrodynamic force of flowing water, erosion and scour, 

the impact of ice and other floodborne debris, or wave action. If your home is located in an area subject to any 

of these hazards, consider an alternative retrofitting method, such as elevation on an open foundation (Section 

5.2.3) or relocation (Section 6.1). Dry floodproofing a home does not change its vulnerability to damage from 

high winds or earthquakes.

Flood Duration

Flood duration is an important consideration because the potential for seepage through and deterioration of the 

materials used to seal the home increase with the length of time that the home is exposed to flooding. Also, the 

longer the duration, the greater the likelihood that the soil beneath and adjacent to the home will become fully 

saturated and add to the loads on the walls and floor (Figure 7-4). Additionally, most dry floodproofing methods 

depend on sump pumps to address water that has leaked into the house, and those pumps require electricity to 
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7 FLOODPROOFING

run. Although some sump pumps have battery backups, these backups typically only last a few hours, so a generator system may also be required for long-duration flooding. If your home is in an area where floodwaters remain 

high for days, weeks, or even months at a time, consider an alternative retrofitting method, such as elevation or 

relocation.

Human Intervention

Dry floodproofing systems almost always include components that have to be installed or activated each time 

flooding threatens. One example is a flood shield placed across a doorway. For this reason, dry floodproofing is not 

an appropriate retrofitting method in areas where there is little or no flood warning or where, for any other reason, the homeowner will not be able or willing to install shields or other components before floodwaters arrive.

Post-Flood Cleanup

Remember that floodwaters are rarely clean. They usually carry sediment, debris, and even corrosive or hazardous 

materials, such as solvents, oil, sewage, pesticides, fertilizers, and other chemicals. The walls of a dry floodproofed 

home will be exposed to whatever is in the floodwaters. Cleaning up a dry floodproofed home after a flood may, 

therefore, involve not only removing mud and debris from around the home, but also decontaminating or disinfecting walls and other exterior surfaces. Hurricane Sandy Fact Sheet 1, Cleaning Flooded Buildings (FEMA. 

2013a), provides some guidance on cleaning up following a flood. 

7.2.2 Modifications Required for Dry Floodproofing

Dry floodproofing involves the use of sealants and shields, the installation of a drainage system, and the protection of service equipment.

Sealants

Except for some types of high-quality concrete, most wall materials are not impervious to water. Therefore, 

sealants must be applied to the walls of a dry floodproofed home to prevent leakage. Prior to applying a sealant, a 

structural engineer must determine whether the walls can resist the loads. Flexible sealants are compounds (such 

as asphalt coatings) or materials (such as polyethylene film) that are applied directly to the outside surface of the 

home walls. Sealants must also be applied to all structural joints, such as the joint between the walls and a slab 

floor, and to any other openings below the flood level, such as those where utility lines enter the home through 

the walls or floor. Some of these sealants are designed to be applied to the outside of the wall, while others can be 

applied to the inside of the walls. Which sealant is appropriate will depend on the manufacturer’s recommendations and the access to the wall surfaces or structural joints.

Sealants that can be applied to outside walls include cement- and asphalt-based coatings and clear coatings, such as 

epoxies and polyurethanes. Cement- and asphalt-based coatings are often the most effective, but they can change 

the appearance of the wall (Figure 7-5). The aesthetic advantage of many exterior treatments is lost when these 

coatings are applied over them. Clear coatings do not change the appearance of the wall, but are less effective

Figure 7-6 shows one method of sealing masonry walls with an asphalt-based coating that does not detract from 

their appearance. In this method, a new masonry veneer is added to the existing veneer after the coating is applied. 

An alternative to using coatings is to temporarily wrap the entire lower part of the home in polyethylene film 

when flood conditions threaten. This alternative is sometimes referred to as the “wrapped home” technique. The 

cross-section view in Figure 7-7 shows how this technique works. There must be at least several hours of warning time in order to properly deploy this method. The use of a flood wrapping system should be considered 

temporary and largely an emergency solution to a flooding problem.
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FLOODPROOFING 7

Figure 7-5. Example of an exterior application of a spray-applied asphalt membrane (left – courtesy of GMX, inc.) and an 

interior application of a fiber reinforced polymer wrap (right).

Figure 7-6. A way to seal an 

existing brick-faced wall is 

to add an additional layer of 

brick with a seal in between. 

Please note that weep holes 

(drainage) and wick drains 

are moved up to prevent 

moisture from getting inside 

the walls. 
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7 FLOODPROOFING

Polyethylene film is not a strong material; it cannot withstand water pressure on its own and can be punctured 

fairly easily. As a result, the following requirements must be met when the wrapped home technique is used:

n The manufacturer’s literature must demonstrate applicability of the film to the home’s building materials. 

Rely on actual test results, if available.

n The installation must be carried out very carefully. Even a small hole in the film will leak under the 

pressure of floodwaters.

n The film must be applied directly against the walls of the home so that the walls, rather than the film, 

provide the resistance to water pressures. This may require strengthening the walls of the home and 

openings, such as doors.

n Where the film covers doorways and other openings, it must be backed by framed plywood panels that 

are braced to resist water pressures.

n A temporary drainage system must be provided to collect and dispose of any water that leaks through 

holes in the film. (Drainage systems are discussed later in this section.)

n The duration of flooding should be less than 12 hours and the flood depth adjacent to the home should 

not exceed 1 foot. 

Home wrap systems require secure connections at both the top and bottom of the wrap. The actual loads imposed 

vertically on the wrap are difficult to determine because they can vary depending on the quality of the installation. 

Voids or weak spots left from poor construction may force the wrap to carry the weight of the water and should 

be avoided. 

Figure 7-7. In the “wrapped 

home” method, the lower 

portion of the home is 

protected with a temporary 

layer of polyethylene film. As 

shown, a temporary drainage 

line is also required.
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FLOODPROOFING 7

The following should be considered in the selection of a top-ofwall connection system:

n A clamping system that uniformly supports the wrap. 

A small spacing on the connections and a connection 

system with some rigidity on the outside of the wrap 

can provide this needed support.

n The existing wall construction can vary widely. Part of 

the connection may need to be a permanent part of the 

wall.

Anchoring a wrap into the ground at the base of a wall is the most important link in the wrap system (see Figure 

7-7). The following recommendations should be followed during selection of a system:

n A drain line between the wrap and the building is usually required to remove any water that leaks 

through the wrap or seeps through the soil under the anchor.

n As with the top-of-wall connection, wrap forces are difficult to determine. Details that have worked in 

the past and that are compatible with the building and the selected wrapping system should be followed.

n The end of the wrap should be buried at least below the topsoil layer. Additional ballast may be needed 

(e.g., sandbags, stone) to prevent wrap movement in a saturated and/or frozen soil condition.

n The product literature for the wrap material and applicable codes and standards should be reviewed and 

followed.

Before selecting a wrapping system, make sure that the manufacturer’s literature addresses the following issues.

n Are any chemicals used or stored around the home or onsite that could damage the wrapping system? 

Evaluate adjacent properties to identify any potential chemicals that could damage a wrap system.

n How should the wrapping system be repaired and approximately how much additional wrapping 

material is required for each repair? Understanding whether the wrapping material can be repaired 

under flood conditions or if it must be dry for a proper repair to be made is important.

Shields

Shields are flood barriers placed over openings in walls such as doorways and windows. Shields can be made of 

several materials, depending on the size of the opening to be covered, and should include gaskets along their 

edges. When flood depths are expected to reach the maximum allowable 2 to 3 feet, shields for openings wider 

than approximately 3 feet must be made of strong materials such as heavy-gauge aluminum or steel plates (Figure 7-8); shields for lesser depths and smaller openings can be made of lighter materials. Because of the potential 

risk of a shield failing, a structural engineer must assist with the design of the shields and evaluate the entire dry 

floodproofing system. The engineer may also determine that the walls to which the shield is attached need to be 

strengthened to carry the flood loads associated with the shield.

Because permanently blocking all doors and other openings would be impractical, shields are usually placed temporarily, after flood warnings are issued. Most residential shields are light enough that they can be stored in the 

home and, when needed, brought out and bolted in place or secured in permanently installed brackets or tracks 

(Figure 7-9). Although rare for residential applications, some larger, heavier shields may have to be permanently 

installed on hinges or rollers so that they can be opened and closed easily.

WARNING

Wrap systems may be affected by 

freeze-thaw cycles. Careful installation in accordance with manufacturer 

instructions and evaluation of performance in frozen climates is advisable.
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7 FLOODPROOFING

Figure 7-8. Heavy-gauge 

metal shield over sliding 

glass door opening.

Figure 7-9. Light-gauge

metal shield held in place by 

permanently installed tracks.

Companies that specialize in flood protection devices can provide custom-fitted flood shields. Usually, these commercial shields are made of heavy-duty materials, and some are equipped with inflatable or other types of gaskets 

that help eliminate leaks. Gaskets left exposed to the elements can rapidly decay. Gasket materials should be stored 

indoors and checked periodically for tears or decay. A faulty gasket can allow floodwaters to get past the gasket, 

nullifying any of the other floodproofing techniques.

An alternative to using shields is to permanently seal openings. For example, a low-level window can be removed 

or raised and the opening bricked up or filled with glass block (Figure 7-10).
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FLOODPROOFING 7

Figure 7-10. Low window 

raised approximately 2 feet 

and original opening filled 

with brick.

DEFINITION

Underseepage is water that migrates 

downward along the sealed walls of a 

home and then under the foundation.

Drainage Systems

Sealants and shields provide the bulk of the protection in dry 

floodproofing, but they may permit some leakage, especially 

during floods of longer duration and when damaged by debris. 

They also do not protect against “underseepage,” water that 

migrates downward along the sealed wall and then under the 

foundation. For these reasons, a dry floodproofed home must 

have a drainage system that will remove any water that enters 

the home through leaks in sealants and shields and any water 

that accumulates at the base of the foundation. Depending on 

the permeability of the soils around and under the home, the 

drainage system may also have to be designed to reduce buoyancy forces.

An adequate drainage system includes drains along the base of the foundation and under the floor. The drains 

consist of perforated pipe surrounded by crushed stone. The pipes collect water that seeps through the ground 

and channel it to a central collection point equipped with a sump pump. This system is shown in Figure 7-11. 

The sump pump must have sufficient capacity to handle the inflow of water and must have an emergency power 

source, such as a portable generator, so that it will continue to operate if conventional electric service is disrupted. 

Depending on soil conditions, seepage rates may exceed the maximum discharge rates of standard sump pumps.

Drainage systems should be designed and laid out based upon several factors, such as the design flood depth, soil 

conditions, and the construction methods and materials of the area to be protected. These factors will also affect 

the size of the sump pump and the requirements for a backup power source. Because of the complexity of these 

designs and the potential consequences of a system failure, seek the input of a design professional familiar with 

dry floodproofing systems.
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7 FLOODPROOFING

Figure 7-11. Drainage system 

for a dry floodproofed home.

Protecting Service Equipment

Dry floodproofing a home will not protect service equipment outside the home. Examples of service equipment 

typically found outside the home are utility lines, air conditioning compressors, heat pumps, and fuel storage 

tanks. Chapter 9 discusses the protection of service equipment.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 8-1

8.0 Barriers

Levees and floodwalls are types of flood protection 

barriers. A levee is typically a compacted earthen 

structure; a floodwall is an engineered structure usually built of concrete, masonry, or a combination 

of both (Figure 8-1). Barriers can be built to protect a single 

structure or multiple structures. Types of barriers include levees, 

floodwalls, and temporary barriers.

Table 8-1 includes a summary of advantages and disadvantages 

for using barriers as a mitigation measure.

WARNING

Floodwalls and levees are not permitted to address Substantial 

Improvement/Damage and do not 

bring new buildings into compliance 

with NFIP regulations unless they are 

accredited per 44 CFR § 65.10.

Furthermore, the floodwalls and 

levees described in this chapter will 

not lower your flood insurance premium cost.

Figure 8-1. Structure 

protected by levee (on left) 

and floodwall (on right).

NOTE

For more information about barriers refer to FEMA 511, Reducing Damage from Localized Flooding. 

USACE’s Floodproofing – How to Evaluate your Options (FEMA.2005) document is also a good source for 

barrier options.
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8 BARRIERS

Table 8-1. Considerations for Using Barriers

Advantages Disadvantages

• Floodwaters cannot reach the structure(s) in the protected area and, therefore, will not cause damage through 

inundation, hydrodynamic pressure, erosion, scour, or 

debris impact. 

• The structure and the area around it will be protected 

from inundation, and no significant changes to the structure will be required. 

• Barriers may not be used to bring a Substantially 

Damaged or Substantially Improved structure into compliance with the community’s floodplain management 

ordinance or regulation.

• Cost may be prohibitive, as a large area may be required 

for construction. 

• Periodic maintenance is required.

• Local drainage can be affected, possibly creating or 

worsening flood problems for others.

8.1 Levees

Levees are embankments or structures constructed of compacted 

earthen materials. Construction of a levee begins with excavating and inspecting the cutoff trench. This gives the designer a 

better look at the subsurface soil conditions, so that the presence 

of roots, utility lines, and animal burrows, or changes in soil 

conditions can be considered during the design process. The interior of the levee is composed of an impermeable core, usually 

clay. The lifts of impervious clay fill are placed in 6-inch layers, 

with each lift compacted to the density specified by the designer 

(Figure 8-2). As with large floodwalls, a licensed Professional 

Engineer should perform the levee design and certification.

DEFINITION

A cutoff trench is a core located 

below the base of a dam or levee 

structure. The trench is filled with an 

impervious material, such as clay, to 

form a watertight barrier to prevent 

under-levee seepage.

Figure 8-2. Levee 

construction.

Levees can be used to completely circle a building. However, they require a lot of space and a large quantity of 

earthen fill. Unless the fill is readily available nearby, hauling it to the site may prove to be cost-prohibitive. Integrating parts of the new levee into existing ground that is close to or above the levee’s design elevation can help 

reduce construction costs. 
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BARRIERS 8

8.2 Floodwalls

A floodwall is an engineered structure made of reinforced concrete or reinforced concrete block. A typical residential floodwall usually varies from 1 foot to 4 feet in height and can surround a structure or, depending on flood 

depths, site topography, and design preferences, protect building openings, such as doors, windows, and basement entrances, including entry doors and garage doors. When built with decorative bricks or blocks or as part 

of garden areas, floodwalls can be attractive architectural or landscaping features. They can also be built solely for 

utility, usually at a much lower cost.

Because a floodwall is made of concrete or masonry rather than compacted earth, it is more resistant to erosion 

than a levee and requires less space than a levee that provides the same level of protection. However, floodwalls 

are often more expensive. As a result, floodwalls are normally considered only for sites where there is not enough 

space for a levee or where high-velocity flows may erode a levee. Also, some property owners prefer floodwalls 

because they can be more aesthetically pleasing and allow for the preservation of existing site features, such as 

landscaping and trees, or covered with a decorative stone finish (Figure 8-3).

Figure 8-3. Structure 

protected by a floodwall with 

decorative stone finish.

8.3 Temporary Barriers

Several types of temporary barriers are available to address typical flooding problems. They work with the same 

principles as permanent barriers, such as floodwalls or levees, but can be removed, stored, and reused in subsequent flood events. Most of these barriers are meant to take the place of sandbag floodwalls and may also be used 

to reinforce existing permanent barriers such as levees (Figure 8-4).

Temporary barrier products are designed so that they can be used numerous times. The Association of State Floodplain Managers (ASFPM) worked with the USACE and Underwriters Laboratories (UL) to establish a testing/

certification program for temporary flood barriers. ASFPM, UL, and USACE initiated program development, and 

FM Approvals (a division of FM Global) developed an approval system for recognizing temporary barriers as flood 
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8 BARRIERS

abatement equipment for their policyholders. In 2006, FM Approvals published FM Standard 2510, Approval Standard for Flood Abatement Equipment (2006). The current FM Approvals test protocols are for self-supporting, temporary 

barriers designed to protect against riverine flood depths up to 3 feet. These barriers are not tested for coastal 

flooding applications, where the presence of saltwater may hinder their performance. Because saltwater is denser 

than freshwater, a barrier filled with freshwater in a coastal location may float instead of providing protection 

against flooding.

Figure 8-4. Two-foot-high 

water-filled temporary barrier 

protecting a residence from 

flooding ( 2010 – Courtesy of 

Hydrological Solutions, Inc.).

8.4 Technical Considerations

The factors discussed in the following sections affect the type of a barrier best suited for your home and should 

be considered before making a barrier selection. 

8.4.1 Height of Barrier

When barriers are built to protect a single structure, they are referred to as “residential,” “individual,” “on-site,” 

or “local” levees and floodwalls. Levees and floodwalls should be built to protect the residence from predicted 

flood heights as depicted on FEMA FIRMs, in FISs, or local flood vulnerability analyses. If the height of the levee 

or floodwall would make the project cost-prohibitive, then elevation or relocation of the residence should be considered. The practical, cost-effective heights of these levees and floodwalls are usually limited to 6 feet and 4 feet, 

respectively. These limits are the result of the following considerations:

n The higher the levee or floodwall, the greater the depth of water that builds behind it and the greater the 

water pressure exerted on the barrier. Taller levees and floodwalls must be designed and constructed to 

withstand the increased pressures. Meeting this need for additional strength greatly increases the cost of 

the levee or floodwall, usually beyond what an individual property owner can afford.

n Because taller levees and floodwalls must be stronger, they must also be more massive, so they usually 

require more space than is likely to be available on an individual lot. This is especially true of levees.

n Local zoning and building codes may also restrict the use, size, and location. 
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BARRIERS 8

Local floodplain management ordinances and regulations may require a “no-rise” study to prove that the barrier 

system will not increase flood heights downstream of the barrier structure. 

If the flood depth at the project site is above the practical height limits of available barriers, an alternative mitigation method, such as elevation, should be considered. The levee or floodwall can always be overtopped by a 

higher-than-expected flood regardless of the height of the barrier. Overtopping is a greater concern for a levee 

than a floodwall because a small amount of overtopping can cause erosion at the top of the levee and cause it to 

fail.

8.4.2 Basement Foundations

Special design considerations are necessary when levees or floodwalls are built to protect a structure with a basement. Even though the surface water is kept from coming into contact with the structure, the soil below the levee 

or floodwall and around the structure can become saturated, especially during floods of long duration. The resulting pressure on basement walls and floors can cause them to crack, buckle, or even collapse. An analysis by a 

qualified soils engineer can help to determine a sufficient distance for the floodwall or barrier from the structure 

to lessen or alleviate this pressure. 

8.4.3 Soil Conditions

The type of soils encountered may have a significant impact on the choice of barriers as a flood protection option. 

This is true regardless of the choice of a permanent barrier or a temporary barrier. The following soil characteristics must be considered:

n Bearing capacity. This is the capacity of a soil to support applied loads. Permanent barriers such as 

levees and floodwalls, as well as many temporary barriers, are very heavy. If the soil type has low bearing 

capacity, the barrier may either fail structurally or begin to sink, losing its design protection height and 

capability. In this instance, alternative mitigation, such as elevation, relocation, or floodproofing should 

be considered.

n Permeability. Barriers should be deployed on tight, impermeable soils. If the soils are permeable, such 

as sand or sandy loam, steps need to be taken to counteract the seepage of water under or through the 

barriers. These steps include installing an impervious core for a levee and a cutoff trench filled with 

impermeable bentonite clay soil. Bentonite clay should also line the levee surface. A cutoff trench is a 

below-grade core of bentonite clay that prevents movement of pervious materials, such as loose sand and 

gravel, which can compromise the levee’s performance.

8.4.4 Duration of Flooding

All barriers exposed to floodwaters for an extended period of time will be subject to seepage or leakage. If the duration of flooding is relatively short (less than 1 day) and the depth of flooding is relatively low (less than 1 foot), 

many barriers will at least slow down the effects of inundation. Longer exposures require barriers that are better 

engineered and more carefully constructed or deployed. Likewise, deeper flood depths also need to be considered 

as a result of the extremely high forces exerted on the barriers by the weight of the floodwaters.
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8 BARRIERS

8.5 Additional Considerations

The factors discussed in the following sections involve practical considerations affecting barrier selection.

8.5.1 Annual Maintenance

A barrier requires periodic inspections and maintenance to address any necessary repairs. Otherwise, small problems, such as cracks, loss of surface vegetation, erosion and scour, animal tunnels, and trees and shrubs can quickly 

become large problems during a flood event. The barrier should be inspected at a minimum each spring and fall, 

before each impending flood, and after each flood event. To facilitate slope stability as well as maintenance and 

safe grass mowing, the side slopes of most levees should not be steeper than 1 foot vertically to 2.5 feet horizontally (1:2.5) on the floodwater side and 1 foot vertically to 3 feet horizontally (1:3) on the land side. In general, 

driveways positioned to provide access over a protective levee that circles a residence should not be steeper than 

1:3. Trees and large shrubs should not be located on barriers as they can be overturned during high-wind events 

and compromise the structural integrity of the levee. When trees and shrubs die, their roots decay, leaving cavities 

for water to pass through, which can cause the barrier to fail. 

Homeowners interested in additional information on inspection of levees can refer to the following technical 

manuals available for download from the FEMA Website at http://www.fema.gov/technical-manuals-and-guides: 

Technical Manual for Dam Owners: Impacts of Animals on Earthen Dams (FEMA 473) and Technical Manual for Dam Owners: Impact 

of Plants on Earthen Dams (FEMA 534). Although these manuals were developed for dam owners, they contain many 

principles that are applicable to levees.

8.5.2 Housing of Occupants

Although a residence can be used during construction of a barrier, the residence should not be occupied during 

a flood event. Levees and floodwalls may give the homeowner a false sense of security. Every flood is different and 

one that exceeds the height of the barrier could occur at any time. If water overtops the barrier, the protected area 

will fill rapidly. Homeowners should evacuate when a flood warning is first issued. 

8.5.3 Access to Structure

Barriers can make access to the structure difficult. Openings must be created or provided for driveways, sidewalks, and other entrances. These openings must be closed prior to the flood event, as floodwaters can rise rapidly 

enough to prevent an opening from being closed. Examples of these closure mechanisms for floodwalls include 

shields similar to the ones used in dry floodproofing or prefabricated panels and permanently mounted, hinged, 

or sliding flood gates and prefabricated stop logs or panels for levee openings. Unless the gates remain in the 

closed position at all times, human intervention is required to close an entry point to prevent rising floodwaters 

from entering the structure (Figure 8-5).

8.5.4 Human Intervention

As described in Section 8.5.3, openings in the barrier must be closed prior to a flood event. Putting the closure 

mechanisms in place requires human intervention. The barrier will not protect the structure from flooding unless 

the property owner is willing and able to operate all closures before the flooding begins. 
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BARRIERS 8

Figure 8-5. The City of 

Boulder, CO, installed a “pop 

up” closure to this floodwall 

at a City office building 

subject to flash floods. The 

closure floats up into place 

automatically when the site 

is flooded.

8.5.5 Interior Drainage

A barrier that keeps floodwater out of the protected area also will keep water in. Drains and sump pumps should 

be installed to remove water collected inside the barrier. In addition, caution must be taken to ensure that local 

drainage patterns in the area are not disrupted. An interior drainage system, including a sump pump (Figure 8-6), 

must be installed in an area protected by a levee or floodwall.

Figure 8-6. Small patio 

floodwall with sump pump.

HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 9-1

9.0 Protecting Service 

Equipment

Homes are typically provided with a variety of building support service equipment. Five major services 

make up the mechanical, electrical, and plumbing (MEP) systems found in most homes: 

n HVAC systems, including air conditioning 

compressors, heat pumps, furnaces, ductwork, and 

n Fuel systems, including natural gas lines and fuel 

storage tanks 

n Electrical systems, including wiring, switches, 

outlets, fixtures, and fuse and circuit breaker panels 

n Sewage management systems, including sewer lines, 

drains, septic tanks, and drainage fields 

n Potable water systems, including water lines, private 

wells, storage tanks, and water heaters 

Most homes also have communications systems, including 

telephone, internet, and cable television lines. 

Some MEP equipment is typically located inside a home (e.g., furnaces, ductwork, water heaters, appliances) and 

some is located outside (e.g., propane tanks, air conditioning and heat pump condensers, septic tanks). Other MEP 

equipment includes components found both inside and outside a home (e.g., electrical systems; plumbing, gas, 

telephone, internet, and cable television lines; oil storage tanks). 

The original placement of service equipment in and around your home was probably based on standard construction practices and the builder’s preferences. As a result, service equipment is often installed in areas where it will 

be exposed to floodwaters, such as in a basements or crawlspaces or at ground level outside the home. 

Elevation, wet floodproofing, and dry floodproofing protect the structure of your home from damage by floodwaters. But these methods, unlike relocation and the construction of levees or floodwalls, do not prevent floodwaters 

CROSS REFERENCE

For more information about elevating 

electrical and HVAC systems, refer 

to FEMA 348, Protecting Building 

Utilities from Flood Damage (1999), 

Hurricane Sandy Recovery Advisory 

No. 3, Restoring Mechanical, 

Electrical, and Plumbing Systems 

(2013), and FEMA 499, Fact Sheet 

No. 8.3: Protecting Utilities (2010).
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9 PROTECTING SERVICE EQUIPMENT

from reaching the home. For this reason, protecting service equipment located below the expected flood level is 

an essential part of a retrofitting project. 

When relocating or elevating MEP systems, consider horizontal and vertical clearances; venting; and unions, 

fittings, and valves. The replacement of MEP systems also presents an opportunity to improve the energy efficiency 

of your house by selecting high-efficiency equipment that may not have been available when the damaged equipment was installed.

If your house has been damaged by a flood, the repair and restoration work must not violate any floodplain 

management requirements in effect when the house was originally built. Always check with your local building 

department, as locally enforced codes may differ from what is described in this chapter. For example, some communities may require all MEP system restoration or alteration work to comply with the applicable sections of the 

current code, even in houses that are not Substantially Damaged. When considering relocating or elevating MEP 

systems, follow all applicable codes, regulations, and manufacturers’ installation requirements.

Flood Insurance Implications 

Houses built after communities joined the NFIP were required to be elevated to or above the BFE to minimize 

flood damage. These houses should already have elevated MEP systems and components. However, if some equipment was not elevated (such as a furnace or ductwork located in a crawlspace), owners may be paying much 

higher NFIP flood insurance premiums than necessary. Replacing damaged equipment and elevating it on platforms not only minimizes future damage, but may lower flood insurance premiums. Check with insurance agents 

to find out whether taking this action will affect your flood insurance premiums.

You can protect interior and exterior service equipment in three ways: elevating it, relocating it, or protecting it 

in place. More information on these methods can be found in FEMA 348, Protecting Building Utilities from Flood Damage

(1999). 

9.1 Elevation

Service equipment installed outside your home can usually be 

elevated above the flood level. Equipment mounted on an exterior wall (e.g., an electric meter, incoming electric, telephone, 

and cable television lines) usually can be mounted higher up on 

the same wall. Equipment typically placed on the ground (e.g., 

air conditioning compressors, heat pumps) can be raised above 

the flood elevation on pedestals or platforms (Figures 9-1 and 

9-2).

When you elevate service equipment, you should always consider raising it at least 1 foot above the BFE, just as when you 

protect your home with one of the methods described in this 

guide. Elevating service equipment an additional 1 or 2 feet 

often will not increase your retrofitting costs significantly but 

will provide an extra measure of flood protection. Since gas and 

electric meters are typically owned by a utility company, you 

may not be allowed to move or elevate them without the utility 

company’s permission. 

NOTE

Some utility companies have requirements for ensuring their meter 

readers can access the meters, such 

as providing stairs to a platform under 

the reader. Check with your service 

provider before elevating service 

equipment. Refer to the Hurricane 

Isaac Recovery Advisory No. 2, 

Minimizing Damage to Electrical 

Service Components (2012).
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PROTECTING SERVICE EQUIPMENT 9

Figure 9-1. Air conditioning / heat pump 

compressor mounted on a brick pedestal 

outside an elevated home. 

Figure 9-2. Air conditioning/

heat pump compressor 

mounted on a cantilevered 

platform attached to a 

home elevated on an open 

foundation. (Source: FEMA 

P-55 Figure 12-2)
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9 PROTECTING SERVICE EQUIPMENT

The feasibility of elevating equipment inside a basement or 

garage depends largely on the flood level. Simply raising the 

equipment above the floor using a solid pad (such as masonry 

or concrete) or a framed platform (wood or steel) may be possible. Outdoor equipment can be elevated on a platform attached 

to the side of the house. The materials selected to construct elevated platforms should meet the requirements described in 

NFIP Technical Bulletin 2, Resistant Materials Requirements (2008), 

and should be non-combustible when required by the code. A 

pad should be properly anchored to the floor system or slab, and 

the equipment should be properly anchored to the pad. 

As the height of the flood level increases above the floor, the amount of space available above the flood level diminishes and elevation is feasible only for smaller pieces of equipment (e.g., electrical system components, ventilation 

ductwork, or specialized equipment such as furnaces designed to be suspended from the ceiling). If the flood 

level is at or near the ceiling, elevation may not be possible. Instead, equipment must be relocated or protected in 

place as described in Section 9.3. 

Keep in mind that most service equipment must remain accessible for routine maintenance. For example, your 

fuel company must be able to reach your fuel tank to fill or empty it. Before elevating any service equipment, 

check with the utility company to find out whether it has any requirements that would prohibit elevation or 

restrict elevation height. 

Also, remember that any large equipment elevated on platforms or pedestals, both inside and outside your home, 

may be more vulnerable to wind and earthquake damage and may require additional bracing or anchorage. A 

design professional must determine the expected wind and earth¬quake forces at the site and account for them 

in the elevated platform design. 

This precaution is especially important for elevated fuel storage tanks, which could rupture if they are dislodged 

or toppled by wind and earthquake forces. In earthquake-prone areas, fuel storage tanks are sometimes equipped 

with cutoff valves that can help prevent leaks when supply lines are ruptured. Your utility service provider can 

give you more information about cutoff valves and other ways to protect fuel storage tanks from natural hazards. 

9.1.1 Maintaining Horizontal and Vertical Clearances 

When moving equipment, either to another floor or elevated on a platform, maintain the recommended horizontal 

and vertical clearance around it as required by building codes and the National Electrical Code or as recommended 

by manufacturers. Minimum clearances required for equipment, conduits, piping, and duct work should be considered before relocating or elevating equipment. Designing for the minimum clearance is important to maintain 

air circulation, meet insurance or code requirements related to distance from combustible building materials, and 

provide space for maintenance. Most codes dictate that clearance requirements should follow those specified on 

the equipment label or installation instructions. Required clearance typically ranges from 6 to 36 inches, and can 

sometimes be reduced by installing heat shields if allowed by the building code. The use of a heat shield or other 

method to reduce clearance should be verified in codes and manufacturers’ installation requirements. Failure to 

maintain proper clearance can result in safety issues, including fire, and can void equipment warranties. 

NOTE

When elevating HVAC and other 

equipment, be sure to leave sufficient 

space around the unit to allow access 

for maintenance work.
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PROTECTING SERVICE EQUIPMENT 9

9.1.2 Venting Considerations 

Oil- or gas-fueled boilers, furnaces, and water heaters require adequate combustion air and venting of exhaust 

gases. Although some units may vent exhaust directly out of the unit through an exterior wall, other units may 

need to vent exhaust through a chimney. The type of venting system and the clearances necessary for the venting 

system may affect how high the equipment can be elevated.

The venting system should be tested to ensure it draws adequate air and backdrafting does not occur. If relocating 

equipment, consider the required venting system, as it may affect the final placement of the unit. 

9.1.3 Unions, Fittings, and Valves 

When relocating or elevating equipment is not feasible, consider replacing unions, fittings, or valves to allow 

faster replacement of equipment when damaged, or disconnecting equipment prior to a flood event and relocating it to a higher floor. Although this approach will not bring a non-conforming building into compliance with 

NFIP requirements, it may reduce potential flood damage to utility systems.

9.2 Relocation

When space permits, you can move service equipment from a 

basement or other area below the flood level to an upper floor 

of the home or even an attic. Relocation usually requires more 

extensive changes to both your home and the equipment being 

moved, but it often provides a greater level of flood protection 

because the relocated equipment is farther above the flood level. In some situations, you may also be able to relocate outside 

equipment to higher ground, but only when the slope of your 

lot and other site conditions permit. 

Another relocation option is to build a new, elevated utility room as an addition to your home. The addition could 

be built on an open foundation or extended foundation walls. 

Relocating and elevating equipment and systems can be a simple process, such as elevating a water heater on a 

small platform, or a complex process involving relocating equipment to a higher floor or to a new addition built 

specifically as a utility room. Each type of system has specific vulnerabilities, characteristics, and restrictions on 

placement that can affect a homeowner’s ability to relocate it. 

9.2.1 Electrical Panels

Power outages after a flood event often last much longer if a house’s electrical panel is located below the flood 

elevation because the panel must be replaced before power can be restored. To address this problem, the electrical 

panel should be relocated to an elevation above the lowest floor (into the living space). When moving electrical 

panels to an elevation above the lowest floor, additional components, such as a service disconnect, may need to 

be incorporated into the system to meet the requirements of the National Electrical Code. Also, when relocating 

electrical panels, codes or local requirements may require replacing significant portions of the house wiring. For 

additional information on relocating electrical systems, consult Hurricane Isaac Recovery Advisory No. 2, Minimizing Damage to Electrical Service Components (2012). 

CROSS REFERENCE

Chapters 3 and 4 of FEMA 348, 

Protecting Building Utilities from 

Flood Damage (1999), discuss relocation of service equipment in detail.
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9 PROTECTING SERVICE EQUIPMENT

9.2.2 Electric Meters

Damage to electrical meters is common during flood events. Relocating meters can often result in reduced outage times following flood events. Although some electric utility companies allow meters to be relocated, they 

often have specific requirements and specifications. Most electric utility companies do not want their employees 

to be put at risk climbing ladders or stairs. You may be able to work with your electric utility company to find an 

appropriate spot to relocate your meter to reduce the risk of it being damaged by floodwaters. 

9.2.3 Electrical Wiring

In many houses, some wiring is located below the BFE, especially where the utility service is routed underground. 

If wiring is located below the BFE and the wiring is not rated for wet locations, the wiring should be encased in 

a non-corrosive metal or plastic pipe (conduit) when allowed by code. The conduits should be installed vertically 

to promote thorough drainage when floodwaters recede. Damaged wiring is easier to replace if it is installed in 

a conduit. 

9.2.4 Mechanical Systems 

Mechanical systems include the HVAC system, duct work, and the air handler that delivers the conditioned 

air throughout the house. Elements of the heating and cooling system below the BFE are subject to flooding. 

Ductwork beneath a house’s floor system is susceptible to flooding and should be removed and replaced if it is 

inundated by floodwaters. The ductwork connected to the furnace and air handler is often the most prone to flood 

damage because the furnace is often located in the basement or the building’s lowest floor. 

In many instances, elevating mechanical systems above the BFE may not be possible. They should still be elevated 

as high as possible. Relocating mechanical equipment may require replacing ductwork and moving electrical supplies and refrigerant lines. Physical obstructions, such as walls or framing, may restrict the relocation of ductwork 

and the final location of the system components. 

Condensing units. Protecting the condensing unit for an air conditioning system can often be achieved by elevating it on a platform or attaching a platform to the side of the house. A cantilevered platform is preferred over a 

platform on posts. Posts can obstruct floodborne debris and are more vulnerable to damage and failure, including 

floodborne debris impacts and undermining by scour and erosion.

Heating systems. Boiler systems, which are typically oil- or gas-fired, heat water and either force hot water or 

steam through radiators or baseboards throughout the home. A hot water boiler system consists of the main boiler, heat exchanger and burner, circulation pumps or control valves, and an expansion tank. Many components of 

a boiler system can be damaged by contact with floodwaters. Protecting a boiler system from flooding usually 

requires raising the system in its entirety. Although most boiler systems in residential use are hot water systems, 

the protection of a steam boiler is similar. Relocating a boiler system to an upper level is ideal, but can present 

some significant challenges, such as needing to reroute the plumbing associated with the system. Elevating the 

boiler as high as possible on its current floor may be more practical. The main concerns when elevating a boiler are 

clearances, venting the exhaust, and protecting the supply tank from contamination. Systems using heating oil rely 

on either an above- or below-ground storage tank. The storage tank should be properly anchored and sufficiently 

sealed to prevent floodwater from contaminating the heating oil or allowing the oil to be released. 

A furnace or forced air heating system uses oil or natural gas (and sometimes electricity) to heat air blown across 

heating coils in the system. Relocating these systems to upper floors or attic areas may be possible. If elevating the 
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PROTECTING SERVICE EQUIPMENT 9

furnace to an upper floor is not possible and elevating the furnace in its existing location below the living area 

is the only practical mitigation measure, the required clearances and venting of the unit must be accommodated. 

9.2.5 Water Heaters 

Water heaters, which are oil- or gas-fired, are powered from an electric coil. Conventional residential water heaters 

that use storage tanks typically range in capacity from 40 to 80 gallons. When exposed to floodwater, the internal 

components of the water heater can be damaged. 

Electric water heaters. In some buildings, electric water heaters can be relocated to a higher floor or the 

attic. Relocating the unit requires plumbing and electrical work, as well as a method to drain the tank and prevent 

water damage from leakage. Although relocating a water heater to the attic effectively protects it from flood damage, the heater must be equipped with a drain pan and drain to avoid costly water damage in the event of leakage. 

If a water heater is placed in an attic, it should be routinely maintained and inspected for leaks or other problems. 

Oil or gas-fired water heaters. Oil- or gas-fired water heaters must be vented and may, therefore, be difficult to 

move into a main living space. If an appropriate location for the water heater is not available on a higher floor, it 

can potentially be elevated in its current location. Elevating the tank usually requires a small pad or platform, an 

appropriate location to vent the exhaust, and extending or shortening water supply lines and distribution lines. 

Other water heaters. Although more expensive than conventional water heater systems, tankless systems, which 

heat water instantaneously, require significantly less space and may present a flood mitigation opportunity 

because of their smaller size. Converting a conventional water heater unit fueled by natural gas to a tankless system 

requires minimal additional work. Electric tankless water heaters, by comparison, may not be practical because 

of the electrical system upgrades needed in some houses to provide the additional electrical power for the water 

heater.

Although moving equipment into the attic area may appear to be an effective use of space, equipment such as 

water heaters can cause problems if they are not properly installed. Drain pans and piping to address a water heater 

leak must be carefully considered to make sure water will not overflow and damage rooms below. In areas subject 

to freezing temperatures, drain lines could freeze and prevent water from draining, causing significant interior 

water damage.

9.2.6 Washer/Dryer Units 

Many washing machines and clothes dryers are located in basements, where they are vulnerable to flooding. 

Relocating this equipment to a higher floor may not be practical if space is limited in the living area. Even minimal 

elevation may prevent the units from being damaged in low-level flooding situations. A permanent pad or platform should be constructed to elevate these units; stacked bricks or blocks should not be used because they can 

shift and result in injuries to users or damage to the equipment. Elevating washing machines and clothes dryers 

may require altering the water and drain piping, electrical connections, and gas connections.

9.3 Protection in Place

When elevation and relocation are infeasible or impractical, you may be able to protect service equipment in place 

with low floodwalls and shields and with anchors and tie downs that prevent flotation. Plumbing systems can be 

protected with valves that prevent wastewater from backing up into the home. 
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9 PROTECTING SERVICE EQUIPMENT

9.3.1 Floodwalls and Shields 

Floodwalls and shields are typically components of dry floodproofing systems (Chapter 7) that are used to protect 

entire buildings. However, if a building is wet floodproofed, these components can be used for the protection of 

small areas within a building that contain service equipment that cannot be elevated or relocated. For example, 

you can build a concrete floodwall that surrounds one or more pieces of service equipment, such as a furnace and 

water heater (Figure 9-3). 

If the expected flood depth is less than about 12 inches, the floodwall could be low enough that you could step 

over it to reach the protected equipment. A higher floodwall can include an opening equipped with a removable 

shield, as shown in Figure 9-3, to permit easy access to the protected equipment. In this example, the shield does 

not interfere with the normal operation of the equipment, so it should be left in place and removed only when 

necessary to service the equipment. Leaving the shield in place allows the barrier to function without human 

intervention. 

In general, barriers and shields of the type shown in Figure 9-3 are practical only when flood depths are less than 

about 3 feet. The greater hydrostatic pressure exerted by deeper water requires barriers and shields that are more 

substantial, have more complex designs, and are, therefore, more expensive. As discussed in Chapter 8, all floodwalls should provide at least 1 foot of freeboard above the expected flood elevation.

Regardless of the height of the barrier, the area it protects should 

be equipped with a sump pump that will remove any water that 

accumulates through seepage. 

9.3.2 Anchors and Tiedowns

Anchors and tiedowns are used primarily for aboveground storage tanks (ASTs) that are not el-evated above the flood level and 

for underground storage tanks (USTs). Both types of tanks are 

extremely vulnerable to flotation. Floodwaters and debris impact forces act directly on ASTs, and USTs can be forced out 

Figure 9-3. Water heater 

and furnace protected by 

a concrete floodwall with 

opening and gasketed shield.

CROSS REFERENCE

For more information about anchoring fuel storage tanks, refer to FEMA 

348, Protecting Building Utilities 

from Flood Damage (1999), and the 

FEMA Fact Sheet series Protect Your 

Property from Flooding, Anchor Fuel 

Tanks (2011).
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING 9-9

PROTECTING SERVICE EQUIPMENT 9

of the ground by the buoyancy force of saturated soils. When 

either type of tank is displaced, its connections can be severed 

and the escaping fuel can cause hazardous conditions. 

ASTs can be anchored with metal straps or cables that cross over 

the tank and connect to ground anchors. The length and type 

of ground anchor you need depends largely on the type of soil 

at the site. A design professional can advise you about anchors. 

Another way to anchor an AST is to embed its legs in a concrete 

slab (Figure 9-4). 

Ground anchors can also be used for USTs. The anchoring method involves excavating the soil above the tank, placing steel 

I-beams across it, and connecting them to ground anchors. 

Again, check with a design professional concerning the required 

size and type of anchor. USTs can also be anchored with a concrete slab similar to the one shown in Figure 9-4. 

Installing the slab involves excavating around the tank and removing it temporarily while the slab is poured. 

Another alternative is to excavate down to the tank and pour a concrete slab on top, ensuring not to cover access 

openings. 

On all tanks below the flood level, both aboveground and underground, flexible connections must be used 

between the tank and the supply line. Also, the vent and filler tubes must extend above the flood protection elevation (Figure 9-4). If you have adequate warning of an impending flood, top off the tank. A full tank will be less 

susceptible to corrosion from accumulated moisture and will be heavier and better able to resist buoyancy.

Figure 9-4. Anchoring a fuel 

storage tank with a concrete 

slab.

NOTE

Be especially careful when anchoring 

storage tanks or other service equipment in floodways, Zone V areas, 

and other high-risk areas. Consider 

the effects of high-velocity flows, 

wave action, fast moving floodborne 

debris, and extensive erosion and 

scour wherever these hazards are 

likely to occur.
9-10 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

9 PROTECTING SERVICE EQUIPMENT

Although anchoring is particularly important for storage tanks, remember that the levels of future floods can rise 

higher than expected and inundate service equipment that you have elevated, relocated, or protected in place. For 

this reason, service equipment should be anchored whenever possible so that it will remain in place when acted 

on by flood forces. Anchorage systems should be designed assuming a worst-case scenario of an empty tank. 

9.3.3 Backflow Valves

Flooding can inundate and overload sanitary sewer systems and 

combined sanitary/storm sewer systems. As a result, water can 

flow backward through sewer lines and out through toilets or 

drains. The best solution to this problem is usually to install a 

backflow valve. These valves include check valves, gate valves, 

and dual backflow valves. 

Check valves operate without human intervention. Under normal conditions, they allow wastewater to flow from the home to 

the main sewer line. When flooding causes the flow to reverse, a 

flap or other check mechanism in the valve prevents water from 

flowing back into the home. A disadvantage of check valves is 

that they can become blocked open by debris and fail to operate. 

For this reason, check valves must be inspected regularly and cleaned as necessary. 

Gate valves are manually operated, provide a better seal, and are unlikely to be blocked open. However, they are 

more expensive than check valves and require human intervention. 

The third alternative is dual backflow valves, which combine the benefits of the check valve and the gate valve. 

As the most expensive of the three valve types, the dual backflow valve should be considered primarily for use in 

homes subject to repeated backflow flooding. Gate valves and dual backflow valves are usually installed outside 

the home in a valve pit (Figure 9-5). A licensed plumber should install any check valve system in compliance with 

local codes. Some current community codes only allow use of dual check valve systems. 

Figure 9-5. Example of an 

exterior backflow valve 

installed in a valve pit.

WARNING

The installation of backflow valves 

and other plumbing modifications is 

usually regulated by State and local 

building codes. Some municipalities may prohibit the use of backflow 

valves. A plumber or contractor licensed to work in your area will know 

about the code requirements that 

apply to your retrofitting project.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING A-1

Appendix A 

Bibliography and Sources of Information

FEMA and other organizations have produced many documents about floodproofing and flood hazard mitigation. 

Those listed below provide information that may be useful to a homeowner who is thinking about undertaking a 

retrofitting project or to a homeowner’s designer or builder.

ASCE (American Society of Civil Engineers). 2005a. Flood Resistant Design and Construction. ASCE Standard ASCE 24-05.

ASCE. 2010. Minimum Design Loads for Buildings and Other Structures. ASCE Standard ASCE 7-10.

FEMA (Federal Emergency Management Agency). 1999. Protecting Building Utilities from Flood Damage. FEMA 348.

FEMA. 2000. Above the Flood: Elevating Your Floodprone House. FEMA P-347.

FEMA. 2005. Reducing Damage from Localized Flooding. FEMA 511.

FEMA. 2006. Homebuilders’ Guide to Earthquake-Resistant Design and Construction. FEMA 232.

FEMA. 2009. Recommended Residential Construction for Coastal Areas: Building on Strong and Safe Foundations. FEMA P-550.

FEMA. 2010a. Protecting Utilities. FEMA 499, Fact Sheet No. 8.3.

FEMA. 2010b. Substantial Improvement/Substantial Damage Desk Reference. FEMA P-758.

FEMA. 2010c. Wind Retrofit Guide for Residential Buildings. FEMA P-804.

FEMA. 2011a. Anchor Fuel Tanks: Protect Your Property from Flooding. FEMA Fact Sheet. 

FEMA. 2011b. Coastal Construction Manual: Principles and Practices of Planning, Siting, Designing, Constructing, and Maintaining 

Residential Buildings in Coastal Areas. FEMA P-55, Fourth Edition.

FEMA. 2012a. Engineering Principles and Practices for Retrofitting Flood-Prone Residential Structures. FEMA P-259, Third Edition.
A-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

A BIBLIOGRAPHY AND SOURCES OF INFORMATION

FEMA. 2012b. Minimizing Damage to Electrical Service Components. Hurricane Isaac Recovery Advisory No. 2.

FEMA. 2012c. Minimizing Wind and Water Intrusion by Covering the Underside of Elevated Buildings. Hurricane Isaac Recovery 

Advisory No. 1.

FEMA. 2013a. Cleaning Flooded Buildings. Hurricane Sandy Recovery Fact Sheet No. 1.

FEMA. 2013b. Designing for Flood Levels Above the BFE After Hurricane Sandy. Hurricane Sandy Recovery Advisory No. 5.

FEMA. 2013c. Foundation Requirements and Recommendations for Elevated Homes. Hurricane Sandy Recovery Fact Sheet No. 2.

FEMA. 2013d. Hurricane Sandy in New Jersey and New York. FEMA P-942.

FEMA. 2013e. Reducing Flood Risk and Flood Insurance Premiums for Existing Residential Buildings in Zone A. Hurricane Sandy 

Recovery Advisory No. 7.

FEMA. 2013f. Restoring Mechanical, Electrical, and Plumbing Systems. Hurricane Sandy Recovery Advisory No. 3.

FEMA. 2013g. Unified Hazard Mitigation Assistance Guidance.

FM Approvals. 2006. Approval Standard for Flood Abatement Equipment. FM Standard 2510.

International Code Council. 2012. 2012 International Building Code (IBC 2012).

International Code Council. 2012. 2012 International Existing Building Code (IEBC 2012).

International Code Council. 2012. 2012 International Residential Code (IRC 2012).

OSHA (Occupational Safety and Health Administration). 2012a. Hurricane Sandy Cleanup PPE Matrix. Fact Sheet, 

OSHA-FS-3612.

OSHA. 2012b. Mold Hazards During Hurricane Sandy Cleanup. Fact Sheet, OSHA-FS-3619.

Federal Emergency Management Agency – Technical Bulletin Links

Openings in Foundation Walls and Walls of Enclosures, Technical Bulletin 1, August 2008, 

http://www.fema.gov/media-library/assets/documents/2644.

Flood Damage-Resistant Materials Requirements, Technical Bulletin 2, August 2008, 

http://www.fema.gov/media-library/assets/documents/2655.

Non-Residential Floodproofing – Requirements and Certification. Technical Bulletin 3, April 1993, 

https://www.fema.gov/media-library/assets/documents/3473.

Free-of-Obstruction Requirements, Technical Bulletin 5, August 2008, 

http://www.fema.gov/media-library/assets/documents/3490.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING A-3

BIBLIOGRAPHY AND SOURCES OF INFORMATION A

Wet Floodproofing Requirements, FIA-TB-7, December 1993, 

http://www.fema.gov/media-library/assets/documents/3503.

U.S. Army Corps of Engineers

Tests of Brick-Veneer Walls and Closures for Resistance to Floodwaters, May 1978. 

http://www.dtic.mil/docs/citations/ADA064860.

Structural Integrity of Brick-Veneer Buildings, 1978. http://www.dtic.mil/docs/citations/ADA055972.

Systems and Materials to Prevent Floodwaters from Entering Buildings, May 1985. 

http://www.dtic.mil/dtic/tr/fulltext/u2/a156050.pdf.

USACE National Flood Proofing Committee: Flood Proofing Tests – Tests of Materials and Systems for Flood Proofing Structures, 

August 1988. http://cdm16021.contentdm.oclc.org/cdm/ref/collection/p16021coll11/id/6.

Flood Proofing – How to Evaluate Your Options, July 1993. http://www.usace.army.mil/Library/Pages/default.aspx.

For additional information about natural hazards and hazard mitigation, visit the Internet sites listed below:

American Red Cross

http://www.redcross.org 

Applied Technology Council

http://www.atcouncil.org 

Association of State Floodplain Managers

http://www.floods.org 

Disaster Research Center, University of Delaware

http://www.udel.edu/DRC/ 

Federal Alliance for Safe Homes

http://www.flash.org/

Federal Emergency Management Agency

http://www.fema.gov

Hazard Reduction and Recovery Center (HRRC), Texas A&M

http://archone.tamu.edu/hrrc/

Insurance Institute for Business & Home Safety (IBHS)

http://www.disastersafety.org/

National Association of Home Builders

http://www.nahb.org/
A-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

A BIBLIOGRAPHY AND SOURCES OF INFORMATION

National Flood Insurance Program (NFIP)

http://www.floodsmart.gov/floodsmart/

National Geophysical Data Center 

http://www.ngdc.noaa.gov 

National Information Service for Earthquake Engineering, University of California at Berkeley

http://nisee.berkeley.edu 

Natural Hazards Center at the University of Colorado, Boulder, Colorado

http://www.colorado.edu/hazards

StromStruck – A Tale of Two Homes

http://www.stormstruck.com/

U. S. Army Corps of Engineers – National Nonstructural Flood Proofing Committee

http://www.usace.army.mil/Missions/CivilWorks/ProjectPlanning/nfpc.aspx 

U.S. Department of Housing and Urban Development (HUD) – Office of Policy Development and Research (PDNR)

http://www.huduser.org/portal/index.php

U. S. Geological Survey – Earthquake Hazards Program

http://quake.wr.usgs.gov 

U. S. Natural Resources Conservation Service

http://www.nrcs.usda.gov 

Wind Engineering Research Center, Texas Tech University

http://www.depts.ttu.edu/weweb/ 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING B-1

Appendix B 

Glossary

Many of the terms defined here are also defined in the margins of pages on which they first appear or explained 

in the body of the text.

Acquisition and demolition – The voluntary process by which your State or local government purchases an 

existing at-risk building, and, typically, the underlying land; demolishes the building; and converts the land to 

open space. The land is then maintained as open space and used to restore and/or conserve the natural floodplain 

functions. 

Active retrofitting method – Method that will not function as intended without human intervention. See “passive retrofitting method.”

Adjacent grade – See “lowest adjacent grade (LAG).”

Alluvial fan flooding – Flooding that occurs on the surface of an alluvial fan (or similar landform) that originates 

at the apex of the fan and is characterized by high-velocity flows; active processes of erosion, sediment transport, 

and deposition; and unpredictable flow paths.

Armor – To protect fill slopes, such as the sides of a levee, by covering them with erosion-resistant materials such 

as rock or concrete. 

Backfill – To fill in a hole with the soil removed from it or with other material, such as soil, gravel, or stone.

Backflow valve – See “check valve.”

Barrier systems – See “floodwall” or “levees.”

Base flood – Flood that has a 1 percent probability of being equaled or exceeded in any given year (formerly 

known as the 100-year flood).
B-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

B GLOSSARY

Base flood elevation (BFE) – The elevation of the base flood relative to the datum specified on a community’s 

Flood Insurance Rate Map (FIRM). The elevation is shown on the FIRM for Zones AE, AH, A1–A30, AR, AR/A, AR/

AE, AR/A1–A30, AR/AH, AR/AO, V1–V30, and VE and indicates the water surface elevation resulting from a flood 

that has a 1 percent chance of equaling or exceeding that level in any given year. The BFE is the National Flood 

Insurance Program’s (NFIP’s) minimum elevation to which the lowest floor of a building must be elevated or 

floodproofed (Zone A). In Zone V, the bottom of the lowest horizontal structural member must be elevated to or 

above the BFE; floodproofing is not permitted in Zone V. Many SFHAs are shown on FIRMs without BFEs; in these 

areas, community officials and permit applicants are required to obtain and use information from other sources, 

or must estimate or develop BFEs at specific locations.

Basement – Any area of the building having its floor subgrade (below ground level) on all sides.

Benchmark – A reference point established by a survey with a precisely known relationship to a datum. 

Building envelope – The entire exterior surface of a building (including cladding, roofing, exterior walls, doors, 

and windows) that encloses or envelopes the space within.

Buoyancy – The upward hydrostatic force that floodwater exerts on the underside of submerged members (such 

as floor slabs, walls and footings) of homes that have enclosed spaces below the flood level.

Cast-in-place concrete – Concrete poured and formed at the construction site.

Check valve – Valve that allows water to flow in one direction, but automatically closes when the direction of 

flow is reversed. 

Closure – Shield made of strong material, such as metal or wood, used to temporarily close openings in levees, 

floodwalls, and dry floodproofed buildings.

Coastal A Zone – The portion of the coastal SFHA referenced by building codes and standards, where base flood 

wave heights are between 1.5 and 3 feet, and where wave characteristics are deemed sufficient to damage many 

NFIP-compliant structures on shallow or solid wall foundations.

Coastal High Hazard Areas – SFHAs along the coasts that have additional hazards due to wind and wave action. 

These areas are identified on FIRMs as Zones V, V1–V30, and VE.

Compaction – In construction, the process by which the density of earth fill is increased so that it will provide a 

sound base for a building or other structure.

Crawlspace – Type of foundation in which the lowest floor of a home is suspended above the ground on continuous foundation walls.

Cribbing – A temporary framework that usually consists of criss-crossed timbers that provide temporary structural support. Cribbing usually consists of layers of heavy timber. 

Cutoff trench – A core located below the base of a dam or levee structure. The trench is filled with an impervious 

material, such as clay, to form a watertight barrier to prevent under-levee seepage.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING B-3

GLOSSARY B

Datum – An elevation datum is an arbitrary surface that serves as a common reference for the elevations of points 

above or below it. Elevations are expressed in terms of feet, meters, or other units of measure and are identified as 

negative or positive, depending on whether they are above or below the datum. Three common elevation datums are 

mean sea level (msl), NGVD, and NAVD.

Debris – Materials carried by floodwaters, including objects of various sizes and suspended soils.

Demolition – The act or process of reducing a structure, as defined by State or local code, to a collapsed state. 

Design capacity – For drainage systems, the volume of water that a channel, pipe, or other drainage line is designed to convey. 

Design flood elevation (DFE) – The elevation of the design flood relative to the datum specified on the community’s FIRM. The design flood is associated with the greater of the area subject to the base flood or the area designated 

as a flood hazard area on a community flood hazard map. The I-Codes, ASCE 7, and ASCE 24 use the term DFE. In 

most communities, the DFE is identical to the BFE. Communities may designate a design flood (or DFE) in order 

to regulate based on a flood of record, to account for future increases in flood levels based on upland development, or to incorporate freeboard.

Dry floodproofing – Protecting a building through a combination of measures in order to prevent the entrance 

of floodwaters. Structural components of the building must have the capacity to resist the resulting flood loads.

Duration – The measure of how long a flood lasts. Duration can also refer to how long it takes for a creek, river, 

bay, or ocean to return to its normal level.

Elevation – In retrofitting, the process of physically raising an existing building so that it is above the height of 

a given flood.

Elevation datum – Arbitrary surface that serves as a common reference for the elevations of points above or below it. Elevations are expressed in terms of feet, meters, or other units of measure and are identified as negative 

or positive, depending on whether they are above or below the datum. Three common datums are mean sea level 

(msl), National Geodetic Vertical Datum (NGVD), and North American Vertical Datum (NAVD).

Enclosure – That portion of an elevated building below the lowest elevated floor that is either partially or fully 

shut in by rigid walls.

Erosion – A general lowering of the ground surface over a wide area.

Federal Emergency Management Agency (FEMA) – Agency within the Department of Homeland Security (DHS) 

that administers the NFIP. The NFIP is the Federal program, created by Congress in 1968, that makes flood insurance available in communities that adopt and enforce floodplain management ordinances or laws that meet the 

minimum requirements of the NFIP regulations.

Federal Insurance and Mitigation Administration (FIMA) – Component of FEMA directly responsible for administering the flood insurance aspects of the NFIP.

Fill – Material such as soil, gravel, or stone that is dumped in an area to increase the ground elevation. Fill is usually placed in layers and each layer compacted (see “compaction”).
B-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

B GLOSSARY

Flap valve – See “check valve.”

Flash Flood – A flood caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours. 

A flash flood rises and falls very quickly and is usually characterized by high flow velocities.

Flood – Under the NFIP, “a general and temporary condition of partial or complete inundation of normally dry 

land areas” from: 1) the overland flow of a lake, river, stream, ditch, etc.; 2) the unusual and rapid accumulation 

or runoff of surface waters; and 3) mudflows or the sudden collapse of shoreline land.

Flood damage-resistant material – Any building product (material, component, or system) capable of withstanding direct and prolonged contact with floodwaters without sustaining significant damage.

Flood depth – Height of floodwaters above the surface of the ground at a given point.

Flood elevation – Water surface elevation of floodwaters based on a given elevation datum.

Flood frequency – Probability, expressed as a percentage, that a flood of a given size will be equaled or exceeded 

in any given year. For example, the 1 percent annual chance flood has a 1 percent chance (1 in 100) of being 

equaled or exceeded in any given year. 

Flood protection elevation – The elevation to which you choose to protect your home. Although a flood protection elevation less than the DFE is feasible, FEMA recommends protecting your home to at least the DFE.

Floodplain – Any area susceptible to inundation by water from any source. See “regulatory floodplain.”

Floodplain management – Program of corrective and preventive measures for reducing flood damage, including 

flood control projects, floodplain management regulations, floodproofing or retrofitting of buildings, and emergency preparedness plans.

Floodproofing – Any combination of structural or nonstructural changes or adjustments included in the design, 

construction, or alteration of a building that reduce or eliminate flood damage to the building and its contents. 

See “dry floodproofing” and “wet floodproofing.”

Floodwall – Flood barrier constructed of manmade materials, such as concrete or masonry, to keep water away 

from or out of a specified area.

Floodway – Portion of the SHFA that must be reserved to prevent significant increases in flood elevations. The 

flood hazard is usually greater in the floodway (higher flood depths and velocities) than in the surrounding areas 

of the SFHA, referred to as the “flood fringe.”

Flow velocity – Speed at which water moves during a flood. Velocities usually vary across the floodplain and are 

generally greatest near the channel and lowest near the edges of the floodplain.

Footing – The base of a foundation, usually made of concrete and sometimes reinforced with steel bars. Foundation walls are supported on continuous footings; separate foundation members, such as piers, are supported on 

individual footings.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING B-5

GLOSSARY B

Footprint – The land area a house covers. This area is equal to the length of the home multiplied by its width. The 

footprint is not necessarily equal to the total square footage of the home.

Frame Construction – A type of construction in which a supportive framework forms the primary structural element of a building. In residential construction, the framework typically consists of wood or steel members. 

Freeboard – An added margin of safety, expressed in feet above a specific flood elevation, usually the BFE. In States 

and communities that require freeboard, buildings are required to be elevated or floodproofed to the higher elevation. For example, if a community adopts a 2-foot freeboard, buildings are required to be elevated or floodproofed 

to 2 feet above the BFE.

Frequency – See “flood frequency.”

Grade beam – In a slab foundation, a support member cast as an integral part of the slab, as opposed to a separate footing.

Hazard mitigation – Sustained action taken to reduce or eliminate long-term risk to people and property from 

hazards such as floods, hurricanes, earthquakes, and fires.

Human intervention – Any action that a person must take to enable a flood protection measure to function as 

intended. This action must be taken every time flooding threatens.

High-velocity flow – During a design flood or lesser conditions, water movement adjacent to structures and/or 

foundations with flow velocities greater than 10 feet per second.

Hydrodynamic force – Force exerted by moving water.

Hydrostatic force – Force exerted by water at rest, including lateral pressure on walls and uplift (buoyancy) on 

floors.

Ice Jam – Accumulation of floating ice fragments that causes the bridging or damming of a channel or stream.

Impervious soils – Soils that resist penetration by water.

Intensity of rainfall – The amount of rain that falls during a given amount of time. It is usually expressed in inches of rainfall per hour. The greater the number of inches per hour, the greater the intensity.

Jetting – A process in which the hole for the installation of a pile is made by a high-pressure stream of water from 

a nozzle attached to the bottom of the pile.

Letter of Map Amendment (LOMA) – Occasionally, a small area is inadvertently shown to be within the SFHA on 

a FIRM, even though the ground is at or above the BFE. If this occurs, an individual property owner may submit 

survey information to FEMA and request that FEMA issue a document that officially removes a property from the 

SFHA, called a Letter of Map Amendment.

Levee – Manmade barrier, usually constructed of compacted soil, designed to contain, control, or divert the flow 

of flood water from a specified area. 
B-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

B GLOSSARY

Local officials – Community employees who are responsible for floodplain management, zoning, permitting, 

building code enforcement, and building inspection.

Lowest adjacent grade (LAG) – The lowest ground surface that touches any of the exterior walls of a home. The 

LAG is determined at the pier or post of an attached deck or porch if the elevation is lower than the point where 

soil touches the foundation of the building. 

Lowest floor – Floor of the lowest enclosed area within a building, including a basement. The only exception is 

an enclosed area below an elevated building, but only when the enclosed area is used solely for parking, building 

access, or storage and is compliant with relevant regulations

Limit of Moderate Wave Action (LiMWA) – A line indicating the limit of the 1.5-foot wave height during the 

base flood. FEMA requires new flood studies in coastal areas to delineate the LiMWA.

Minimal Wave Action (MiWA) area – The portion of the coastal Special Flood Hazard Area where base flood 

wave heights are less than 1.5 feet.

Moderate Wave Action (MoWA) area – see Coastal A Zone.

Manufactured home – A prefabricated frame home constructed on a transportable frame that can be placed on a 

permanent or temporary foundation (subject to Federal and State standards).

Masonry – Walls constructed of brick, stone, or concrete block.

Masonry veneer – Nonstructural, decorative, exterior layer of brick, stone, or concrete block added to the walls 

of a building.

Mean sea level (msl) – A tidal elevation datum based on data collected over a 19-year tide cycle.

Mitigation reconstruction – The construction of an improved, elevated building on the same site where an existing building and/or foundation has been partially or completely demolished or destroyed. 

Modular home – A frame home assembled on site on a permanent foundation from separate sections manufactured elsewhere (subject to local building codes).

National Geodetic Vertical Datum (NGVD) – A geodetic elevation datum previously used by FEMA for the determination of flood elevations. While NGVD has been updated to the NAVD datum on many FIRMs, it is still the 

datum referenced on many of the older FIRMs. 

North American Vertical Datum (NAVD) – A geodetic elevation datum currently used by FEMA for the determination of flood elevations.

Passive retrofitting method – Method that operates automatically, without human intervention. See “active retrofitting method.”

Permeable soils – Soils through which water can easily penetrate and flow.
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING B-7

GLOSSARY B

Pier – Vertical support member of masonry or cast-in-place concrete that is designed and constructed to function as an independent structural element in supporting and transmitting both building loads and environmental 

loads to the ground.

Piling – Vertical support member of wood, steel, or precast concrete that is driven or jetted into the ground and 

supported primarily by friction between the pilings and the surrounding earth. Pilings often cannot act as independent support units and therefore are often braced with connections to other pilings.

Post – Long vertical support member of wood or steel set in holes that are backfilled with compacted material. 

Posts often cannot act as independent support units and, therefore, are often braced with connections to other 

posts.

Precast concrete – Concrete materials such as posts, beams, and blocks that are brought to the construction site 

in finished form.

Prolonged contact – At least 72 hours of contact with floodwaters.

Rates of rise and fall – How rapidly the elevation of the water rises and falls during a flood.

Regulatory floodplain – Flood hazard area within which a community regulates development, including new 

construction, the repair of Substantially Damaged buildings, and Substantial Improvements to existing buildings. 

In communities participating in the NFIP, the regulatory floodplain must include at least the area inundated by the 

base flood, also referred to as the SFHA. 

Reinforcement – Inclusion of steel bars in concrete members and structures to increase their strength. 

Relocation – In retrofitting, the process of moving a home or other building to a new location outside the flood 

hazard area.

Retrofitting – Making changes to an existing home or other building to protect it from flooding or other hazards.

Riprap – Pieces of rock or crushed stone added to the surface of a fill slope, such as the side of a levee, to prevent 

erosion.

Saturated soils – Soils that have absorbed, to the maximum extent possible, water from rainfall or snowmelt.

Scour – A localized loss of soil, often around a foundation element.

Sealant – In retrofitting, a waterproofing material or substance used to prevent the infiltration of floodwater.

Service equipment – The utility systems, heating and cooling systems, and large appliances in a retrofitted home.

Significant damage – As it relates to flood-damage resistant materials, any damage requiring more than cosmetic 

repair.

Slab-on-grade – Type of foundation in which the lowest floor of the home is formed by a concrete slab that sits 

directly on the ground. The slab may be supported by independent footings or integral grade beams.
B-8 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

B GLOSSARY

Special Flood Hazard Area (SFHA) – An area delineated on a FIRM as being subject to inundation by the base 

flood, designated Zone A, AE, A1–A30, AR, AO, AH, A99, V, VE, or V1–V30.

Storm surge – Water pushed toward the shore by the force of the winds swirling around a storm. It is the greatest 

cause of loss of life due to hurricanes..

Subgrade – Below the level of the ground surface.

Substantial Damage – Damage to a building, regardless of the cause, is considered Substantial damage if the cost 

of restoring the building to its before-damage condition would equal or exceed 50 percent of the market value of 

the building before the damage occurred

Substantial Improvement – Under the NFIP, an improvement of a building (such as reconstruction, rehabilitation, or an addition) is considered a Substantial Improvement if its cost equals or exceeds 50 percent of the market 

value of the building before the start of construction of the improvement.

Substantially impermeable – A wall is considered substantially impermeable if it limits water accumulation to 4 

inches in a 24 hour period. In addition, sump pumps are required to control any seepage and flood-resistant materials must be used in all areas where seepage is likely to occur. This standard is the minimum requirement; lower 

seepage rates are possible and strongly encouraged by FEMA, particularly in new construction.

Sump pump – Device used to remove water from seepage or rainfall that collects in areas protected by a levee, 

floodwall, or dry floodproofing. In addition, a sump pump is often part of a standard home drainage system that 

removes water that collects below a basement slab floor.

Tsunami – Large, rapidly moving sea waves produced by an undersea earth movement (earthquakes, crustal displacements or landslides) or volcanic eruption.

Underseepage – Water that migrates downward along the sealed walls of a home and then under the foundation.

Veneer – See “masonry veneer.”

Walkout-on-grade basement – Basement whose floor is at ground level on at least one side of a home. The term 

“walkout” is used because most basements of this type have an outside door or doors (entry door, garage door, or 

both) at ground level. A walkout-on-grade basement is not considered a basement under the NFIP. See “basement.”

Watershed – The land area that drains water to a particular stream, river, or lake. It is a land feature that can be 

identified by tracing a line along the highest elevations between two areas on a map, often a ridge. 

Wave action – The characteristics and effects of waves that move inland from an ocean, bay, or other large body 

of water. Large, fast-moving waves can cause extreme erosion and scour, and their impact on buildings can cause 

severe damage. 

Wet floodproofing – The use of flood-damage-resistant materials and construction techniques to minimize flood 

damage to areas below the flood protection level of a building, which is intentionally allowed to flood. Usually, 

only enclosed areas used for parking, building access, or storage are wet floodproofed. 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING C-1

Appendix C

FEMA Offices

The addresses and telephone numbers of FEMA Headquarters and the 10 FEMA Regional Offices are listed below. 

Staff members of the Regional Office for your area can give you more information about retrofitting, hazard mitigation, and the National Flood Insurance Program.
C-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

C FEMA REGIONAL OFFICES

FEMA HEADQUARTERS500 C Street, SW

Washington, DC 20472

(202) 646-2500, (800) 621-FEMA (3362)

TTY: (800) 462-7585

REGION I – CT, MA, ME, NH, RI, VT

99 High Street, Sixth Floor

Boston, MA 02110

(877) 336-2734

REGION II – NJ, NY, PR, VI

26 Federal Plaza, Suite 1337

New York, NY 10278-0002

(212) 680-3600

REGION III – DC, DE, MD, PA, VA, WV

615 Chestnut Street

One Independence Mall, Sixth Floor

Philadelphia, PA 19106-4404

(215) 931-5500

REGION IV – AL, FL, GA, KY, MS, NC, SC, TN

3003 Chamblee Tucker Road

Atlanta, GA 30341-4112

(770) 220-5200

REGION V – IL, IN, MI, MN, OH, WI

536 South Clark Street, Sixth Floor

Chicago, IL 60605-1521

(312) 408-5500

REGION VI – AR, LA, NM, OK, TX

Federal Regional Center

800 North Loop 288

Denton, TX 76209-3698

(940) 898-5399

REGION VII – IA, KS, MO, NE

9221 Ward Parkway, Suite 300

Kansas City, MO 64114-3372

(816) 283-7061

REGION VIII – CO, MT, ND, SD, UT, WY

Denver Federal Center

Building 710, Box 25267

Denver, CO 80255-0267

(303) 235-4800
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING C-3

FEMA REGIONAL OFFICES C

REGION IX – AZ, CA, HI, NV, American Samoa, Guam, Commonwealth of the Northern Mariana Islands, 

Republic of the Marshall Islands, Federated States of Micronesia

1111 Broadway, Suite 1200

Oakland, CA 94607-4052

(510) 627-7100

REGION X – AK, ID, OR, WA

Federal Regional Center

130 228th Street, SW

Bothell, WA 98021-8627

(425) 487-4600

HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING D-1

Appendix D

Alabama

Alabama Department of Community and 

Economic Development

Office of Water Resources

401 Adams Avenue, Suite 434

P.O. Box 5690

Montgomery, AL 36103-5690

Phone: (334) 353-0853

http://www.adeca.alabama.gov/water/ 

Alaska

Alaska Department of Commerce, Community, and 

Economic Development

550 West 7th Avenue, Suite 1770

Anchorage, AK 99501-3510

Phone: (907) 269-4583

Fax: (907) 269-4539

http://www.commerce.state.ak.us/ 

Arizona

Arizona Department of Water Resources

3550 North Central Avenue

Phoenix, AZ 85012-2105

Phone: (602) 771-8657

Fax: (602) 771-8686

http://www.azwater.gov/ 

NFIP State Coordinating Agencies

Arkansas

Arkansas Natural Resources Commission

101 East Capitol, Suite 350

Little Rock, AR 72201-3823

Phone: (501) 682-3969

Fax: (501) 682-3991

http://www.anrc.arkansas.gov/ 

California

California Department of Water Resources

3464 El Camino Avenue, Suite 200

Sacramento, CA 95821

Phone: (916) 574-1409

http://www.water.ca.gov/ 

Colorado

Colorado Water Conservation Board

1313 Sherman Street, Room 721

Denver, CO 80203

Phone: (303) 866-3441

Fax: (303) 861-4272

http://cwcb.state.co.us/ 

Connecticut

Department of Energy and Environmental 

Protection

79 Elm Street

Hartford, CT 06106

Phone: (860) 424-3537

Fax: (860) 424-4075

http://www.ct.gov/dep/ 
D-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

D NFIP STATE COORDINATING AGENCIES

Delaware

Department of Natural Resources and 

Environmental Control

89 Kings Highway 

Dover, DE 19901

Phone: (302) 739-9921

Fax: (302) 739-6724

http://www.dnrec.delaware.gov

District of Columbia

District Department of the Environment

Watershed Protection Division

1200 First Street, 5th Floor

Washington, DC 20002

Phone: (202) 535-2248

Fax: (202) 535-1364

http://green.dc.gov/watershed

Florida

Division of Emergency Management

2555 Shumard Oak Boulevard

Tallahassee, Florida 32399-2100

Phone: (850) 922-4518

http://www.floridadisaster.org/ 

Georgia

Georgia Department of Natural Resources

4220 International Parkway, Suite 101

Atlanta, GA 30354

Phone: (404) 656-6382

Fax: (404) 675-1607

http://www.gadnr.org/ 

Guam

Guam Department of Public Works

542 North Marine Corps Drive

Upper Tumon, Guam 96913

Phone: (671) 646-3131

Fax: (671) 649-6178

http://www.dpw.guam.gov 

Hawaii 

Hawaii Department of Land and Natural Resources

1151 Punchbowl Street

P.O. Box 221

Honolulu, HI 96809

Phone: (808) 587-0267

Fax: (808) 587-0283

http://www.state.hi.us/dlnr/docare/

Idaho

Idaho Department of Water Resources 

322 East Front Street

Boise, ID 83720

Phone: (208) 287-4928

http://www.idwr.idaho.gov/ 

Illinois

Illinois Department of Natural Resources

Office of Water Resources

One Natural Resources Way

Springfield, IL 62702-1271

Phone: (217) 782-4428

Fax: (217) 785-5014

http://dnr.state.il.us/OWR/ 

Indiana

Indiana Department of Natural Resources

402 West Washington Street, Room W264

Indianapolis, IN 46204-2748

Phone: (317) 234-1107

Fax: (317) 233-4579

http://www.state.in.us/dnr/ 

Iowa

Iowa Department of Natural Resources

502 East 9th Street

Des Moines, IA 50319

Phone: (515) 281-8942

Fax: (515) 281-8895

http://www.iowadnr.com/ 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING D-3

NFIP STATE COORDINATING AGENCIES D

Kansas 

Kansas Department of Agriculture

109 SW 9th Street, 2nd Floor

Topeka, KS 66612-1283

Phone: (785) 296-5440

Fax: (785) 296-4835

http://www.ksda.gov/ 

Kentucky 

Kentucky Division of Water

200 Fair Oaks Lane, 4th Floor

Frankfort, KY 40601

Phone: (502) 564-3410

Fax: (502) 564-9899

http://www.water.ky.gov/ 

Louisiana 

Louisiana Department of Transportation 

and Development

Public Works and Water Resources Division

Floodplain Management Section

1201 Capitol Access Road

P.O. Box 94245

Baton Rouge, LA 70804-9245

Phone: (225) 274-4354

Fax: (225) 274-4351

http://www.dotd.state.la.us/ 

Maine

Maine Department of Agriculture, Conservation 

and Forestry

Floodplain Management Program

93 State House Station, 17 Elkins Lane

Augusta, ME 04333-0038

Phone: (207) 287-8063

Fax: (207) 287-2353

http://www.state.me.us/spo/ 

Maryland

Maryland Department of the Environment

Water Management Administration

1800 Washington Boulevard, Suite 430

Baltimore, MD 21230

Phone: (410) 537-3775

Fax: (410) 537-3751

http://www.mde.state.md.us/ 

Massachusetts

Massachusetts Department of Conservation 

and Recreation

Flood Hazard Management

251 Causeway Street, Suite 800

Boston, MA 02114

Phone: (617) 626-1406

Fax: (617) 626-1349

http://www.mass.gov/dcr/ 

Michagan

Michigan Department of Environmental Quality

525 West Allegan Street

P.O. Box 30458

Lansing, MI 48909-7958

Phone: (517) 335-3448

http://www.michigan.gov/deq 

Minnesota

Minnesota Department of Natural Resources

500 LaFayette Road, Box 32

St. Paul, MN 55515-4032

Phone: (651) 259-5713

Fax: (651) 296-0445

http://www.dnr.state.mn.us/ 

Mississippi 

Mississippi Emergency Management Agency

Office of Mitigation

1 Mema Drive

P.O. Box 5644

Pearl, MS 39208

Phone: (601) 933-6610

Fax: (601) 933-6805

http://www.msema.org/ 

Missouri 

Missouri State Emergency Management Agency

2303 Militia Drive

P.O. Box 116

Jefferson City, MO 65101

Phone: (573) 526-9135

http://sema.dps.mo.gov/ 
D-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

D NFIP STATE COORDINATING AGENCIES

Montana 

Montana Department of Natural Resources 

and Conservation

Floodplain Management Program

1424 9th Avenue

Helena, MT 59620-1601

Phone: (406) 444-6654

Fax: (406) 444-0533

http://dnrc.mt.gov/wrd/water_op/floodplain/default.

asp 

Nebraska 

Nebraska Department of Natural Resources

301 Centennial Mall South

Lincoln, NE 68509-4876

Phone: (402) 471-3932

Fax: (402) 471-2900

http://www.dnr.ne.gov/ 

Nevada 

Nevada Division of Water Resources

901 South Stewart Street, Suite 2002

Carson City, NV 89701

Phone: (775) 684-2847

http://water.nv.gov/ 

New Hampshire

New Hampshire Office of Energy and 

Planning

4 Chenell Drive, 2nd Floor

Concord, NH 03301

Phone: (603) 271-1762

Fax: (603) 271-2615

http://www.nh.gov/oep/ 

New Jersey

Department of Environmental Protection

401 East State Street

P.O. Box 420

Trenton, NJ 08625

Phone: (609) 292-2296

http://www.state.nj.us/dep/ 

New Mexico

New Mexico Department of Homeland Security 

and Emergency Management

13 Bataan Boulevard

P.O. Box 27111

Santa Fe, NM 87508

Phone: (505) 476-9617

Fax: (505) 471-9695

http://www.nmdhsem.org/ 

New York 

New York State Department of Environmental 

Conservation

625 Broadway

Albany, NY 12233-3507

Phone: (518) 402-8146

Fax: (518) 402-9029

http://www.dec.ny.gov/ 

North Carolina

North Carolina Department of Public Safety

Division of Emergency Management

4218 Mail Service Center

Raleigh, NC 27699-4218

Phone: (919) 825-2317

http://www.ncem.org/ 

North Dakota 

North Dakota State Water Commission

900 East Boulevard Avenue

Bismark, ND 58505-0850

Phone: (701) 328-4898

Fax: (701) 328-3747

http://www.swc.state.nd.us/ 

Ohio

Ohio Department of Natural Resources

2045 Morse Road, Building B-2

Columbus, OH 43229

Phone: (614) 265-6752

Fax: (614) 265-6767

http://www.dnr.state.oh.us/ 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING D-5

NFIP STATE COORDINATING AGENCIES D

Oklahoma

Oklahoma Water Resources Board

3800 North Classen Boulevard

Oklahoma City, OK 73118

Phone: (918) 581-2924

Fax: (981) 581-2754

http://www.owrb.ok.gov/ 

Oregon

Department of Land Conservation Development

635 Capitol Street, NE, Suite 150

Salem, OR 97301-2540

Phone: (503) 373-0050

Fax: (503) 375-5518

http://www.lcd.state.or.us/ 

Pennsylvania

Pennsylvania Department of Community and 

Economic Development

Commonwealth Keystone Building

400 North Street, 4th Floor

Harrisburg, PA 17120-0225

Phone: (717) 720-7445

Fax: (717) 783-1402

http://www.newpa.com/ 

Puerto Rico 

Puerto Rico Planning Board

Centro Gubernamental Roberto Sanchez Vilella

P.O. Box 41119, Minillas Station

Santurce, PR 00940-90985

Phone: (787) 723-6200

http://www.jp.gobierno.pr/ 

Rhode Island

Rhode Island Emergency Management Agency

645 New London Avenue

Cranston, RI 02920

Phone: (401) 462-7048

Fax: (401) 944-1891

http://www.riema.ri.gov/ 

South Carolina

South Carolina Department of Natural Resources

Flood Mitigation Program

2762 Wildlife Lane

West Columbia, SC 29172

Phone: (803) 755-9335

Fax: (803) 755-0152

http://www.dnr.sc.gov/

South Dakota

South Dakota Division of Emergency Management

118 West Capitol Avenue

Pierre, SD 57501

Phone: (605) 773-3231

Fax: (605) 773-3580

http://www.oem.sd.gov/ 

Tennessee

Tennessee Department of Economic and 

Community Development

Tennessee Tower Building

3211 North Roan Street

Johnson City, TN 37601

Phone: (423) 434-0158

Fax: (423) 434-0037

http://www.tn.gov/ecd/

Texas

Texas Water Development Board

1700 North Congress Avenue

P.O. Box 13231

Austin, TX 78711-3231

Phone: (512) 463-3509

Fax: (512) 475-2053

http://www.twdb.state.tx.us/

Utah 

Utah Department of Public Safety

Division of Emergency Management

1110 State Office Building

Salt Lake City, UT 84114

Phone: (801) 538-3332

Fax: (801) 538-1676

http://www.cem.utah.gov/ 
D-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

D NFIP STATE COORDINATING AGENCIES

Vermont

Vermont Department of Environmental 

Conservation

Water Quality Division, River Management

1 National Life Drive, Main 2

Montpelier, VT 05620

Phone: (802) 490-6152

http://www.anr.state.vt.us/dec/dec.htm 

Virgin Islands 

Virgin Islands Department of Planning and 

Natural Resources

Cyril E. King Airport, Terminal Building 2nd Floor

St. Thomas, VI 00802

Phone: (340) 774-3320

http://www.dpnr.gov.vi/view-divisions

Virginia

Virginia Department of Conservation and 

Recreation

Division of Dam Safety and Floodplain Management

600 East Main Street, 24th Floor

Richmond, VA 23219

Phone: (804) 371-6135

Fax: (804) 371-2630

http://www.dcr.virginia.gov/

Washington 

Washington State Department of Ecology

P.O. Box 47600

300 Desmond Drive, SE

Olympia WA, 98504

Phone: (360) 407-6131

http://www.ecy.wa.gov/ 

West Virginia

West Virginia Division of Homeland Security 

and Emergency Management

Capitol Building 1, Room EB-80

1900 Kanawha Boulevard

Charleston, WV 25305-0360

Phone: (304) 957-2571

Fax: (304) 965-3216

http://www.dhsem.wv.gov/

Wisconsin

Wisconsin Department of Natural Resources

P.O. Box 7921

Madison, WI 53707

Phone: (608) 266-3093

http://dnr.wi.gov/ 

Wyoming

Wyoming Office of Homeland Security

5500 Bishop Boulevard

Cheyenne, WY 82002

Phone: (307) 777-4907

Fax: (307) 635-6017

http://wyohomelandsecurity.state.wy.us/main.aspx 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING E-1

Appendix E

Alabama

Alabama Historical Commission

468 South Perry Street

P.O. Box 300900

Montgomery, AL 36130-0900

Phone: (334) 230-2690

http://www.preserveala.org 

Alaska

Alaska Department of Natural Resources

Office of History and Archeology

550 West 7th Avenue, Suite 1310

Anchorage, AK 99501-3565

Phone: (907) 269-8721

Fax: (907) 269-8908

http://www.dnr.state.ak.us/parks/oha/index.htm

Arizona

Arizona State Parks

1300 West Washington

Phoenix, AZ 85007

Phone: (602) 542-4009

http://azstateparks.com/SHPO/index.html 

State Historic Preservation Offices

Arkansas

Arkansas Historic Preservation Program

1500 Tower Building

323 Center Street

Little Rock, AR 72201

Phone: (501) 324-9880

Fax: (501) 324-9184

http://www.arkansaspreservation.org/

California

Office of Historic Preservation

Department of Parks and Recreation

1416 9th Street, Room 1442

P.O. Box 942896

Sacramento, CA 94296-0001

Phone: (916) 653-6624

Fax: (916) 653-9824

http://ohp.parks.ca.gov/ 

Colorado

Colorado Historical Society

Office of Archaeology and Historic Preservation

1300 Broadway

Denver, CO 80203

Phone: (303) 866-2136

Fax: (303) 866-2711

http://www.coloradohistory-oahp.org 
E-2 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

E STATE HISTORIC PRESERVATION OFFICES

Connecticut

Connecticut Commission on Culture and Tourism

Historic Preservation and Museum Division

One Constitution Plaza, 2nd Floor

Hartford, CT 06103

Phone: (860) 256-2800

Fax: (860) 256-2811

http://www.cultureandtourism.org/cct/site/default.

asp

Delaware

Division of Historical and Cultural Affairs

21 The Green

Dover, DE 19901

Phone: (302) 736-7400

Fax: (302) 739-5660

http://www.state.de.us/shpo/index.htm 

District of Columbia

Office of Planning

801 North Capitol Street, NE, Suite 4000

Washington, DC 20002

Phone: (202) 442-7600

http://planning.dc.gov/planning/site/default.asp 

Florida

Division of Historical Resources

R. A. Gray Building

500 South Bronough Street

Tallahassee, FL 32399-0250

Phone: (850) 245-6333

http://www.flheritage.com/

Georgia

Department of Natural Resources

Historic Preservation Division

34 Peachtree Street, NW, Suite 1600

Atlanta, GA 30303

Phone: (404) 656-2840

Fax: (404) 657-1046

http://www.gashpo.org/ 

Hawaii

Department of Land and Natural Resources

State Historic Preservation Division

Kakuhihewa Building

601 Kamokila Boulevard, Suite 555

Kapolei, HI 96707

Phone: (808) 692-8015

Fax: (808) 692-8020

http://www.hawaii.gov/dlnr/hpd/hpgreeting.htm 

Idaho

Idaho State Historical Society

2205 Old Penitentiary Road

Boise, ID 83712

Phone: (208) 334-2682

Fax: (208) 334-2774

http://www.idahohistory.net/shpo.html 

Illinois

Illinois Historic Preservation Agency

1 Old State Capitol Plaza

Springfield, IL 62701-1507

Phone: (217) 782-4836

http://www.state.il.us/hpa/ps/ 

Indiana

Department of Natural Resources

Division of Historic Preservation and Archaeology

402 West Washington Street, Room W274

Indianapolis, IN 46204-2739

Phone: (317) 232-1646

http://www.state.in.us/dnr/historic/

Iowa

State Historical Society of Iowa

600 East Locust

Des Moines, IA 50319

Phone: (515) 281-6200

http://www.iowahistory.org 

Kansas

Kansas State Historical Society

6425 SW 6th Avenue

Topeka, KS 66615

Phone: (785) 272-8681

Fax: (785) 272-8682

http://www.kshs.org/resource/buildings.htm 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING E-3

STATE HISTORIC PRESERVATION OFFICES E

Kentucky 

Kentucky Heritage Council

300 Washington Street

Frankfort, KY 40601

Phone: (502) 564-7005

Fax: (502) 564-5820

http://heritage.ky.gov/ 

Louisiana

Division of Historic Preservation

Office of Cultural Development

Department of Culture, Recreation and Tourism

1051 North Third Street

P.O. Box 44247

Baton Rouge, LA 70804

Phone: (225) 342-8160

Fax: (225) 219-9772

http://www.crt.state.la.us/hp/ 

Maine

Maine Historic Preservation Commission

55 Capitol Street

65 State House Station

Augusta, ME 04333-0065

Phone: (207) 289-2132

http://www.state.me.us/mhpc/ 

Maryland

Maryland Historical Trust

100 Community Place

Crownsville, MD 21032-2023

Phone: (410) 514-7600

Fax: (410) 514-7678

http://mht.maryland.gov/

Massachusetts

Massachusetts Historical Commission

Department of the Commonwealth

220 Morrissey Boulevard

Boston, MA 02125-3314

Phone: (617) 727-8470

Fax: (617) 727-5128

http://www.sec.state.ma.us/mhc/mhcidx.htm 

Michigan

Department of History, Arts, and Libraries

702 West Kalamazoo Street

P.O. Box 30738

Lansing, Michigan 48909-8238

Phone: (517) 241-2236

Fax: (517) 241-2930

http://www.michigan.gov/mshda/

Minnesota

Minnesota Historical Society

345 West Kellogg Boulevard

St. Paul, MN 55102-1906

Phone: (651) 259-3000

http://www.mnhs.org/

Mississippi

Department of Archives and History

200 North Street

P.O. Box 571

Jackson, MS 39205-0571

Phone: (601) 576-6850

Fax: (601) 576-6876

http://mdah.state.ms.us/

Missouri

Department of Natural Resources

205 Jefferson

P.O. Box 176

Jefferson City, MO 65102

Phone: (573) 751-7858

http://www.dnr.mo.gov/shpo/ 

Montana

State Historic Preservation Office

Montana Historical Society

1410 Eighth Avenue

Helena, MT 59620

Phone: (406) 444-7715

http://www.montanahistoricalsociety.com/shpo/default.asp 
E-4 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

E STATE HISTORIC PRESERVATION OFFICES

Nebraska

Nebraska State Historical Society

P.O. Box 82554

1500 R Street

Lincoln, NE 68501

Phone: (402) 471-3270

http://www.nebraskahistory.org/ 

Nevada

Nevada State Historic Preservation Office

901 S. Stewart Street Suite 5004 

Carson City, NV 89701

Phone: (775) 684-3448

http://nvshpo.org/

New Hampshire

Division of Historical Resources

19 Pillsbury Street, 2nd Floor

Concord, NH 03301-3570

Phone: (603) 271-3483

Fax: (603) 271-3433

http://www.nh.gov/nhdhr/ 

New Jersey

Historic Preservation Office

Department of Environmental Protection

401 E. State Street

P.O. Box 404

Trenton, NJ 08625-0404

Phone: (609) 984-0176

Fax: (609) 984-0578

http://www.state.nj.us/dep/hpo/ 

New Mexico

Historic Preservation Division

Department of Cultural Affairs

Bataan Memorial Building

407 Galisteo Street, Suite 236

Santa Fe, NM 87501

Phone: (505) 827-6320

Fax: (505) 827-6338

http://www.nmhistoricpreservation.org/

New York

State Historic Preservation Office

Peebles Island

P.O. Box 189

Waterford, NY 12188-0189

Phone: (518) 237-8643

http://nysparks.state.ny.us/shpo/ 

North Carolina

State Historic Preservation Office

Office of Archives and History

Department of Cultural Resources

109 East Jones Street

Raleigh, NC 27699

Phone: (919) 807-6570

Fax: (919) 807-6599

http://www.hpo.ncdcr.gov/

North Dakota

State Historical Society of North Dakota

Heritage Center

612 East Boulevard Avenue

Bismarck, ND 58505-0830

Phone: (701) 328-2672

Fax: (701) 328-3710

http://www.history.nd.gov/

Ohio

Ohio Historical Society

Historic Preservation Office

567 East Hudson Street

Columbus, OH 43211-1030

Phone: (614) 298-2000

Fax: (614) 298-2037

http://www.ohiohistory.org/resource/histpres/ 

Oklahoma

State Historic Preservation Office

Oklahoma Historical Society

2401 North Laird Avenue

Oklahoma City, OK 73105

Phone: (405) 521-6249

Fax: (405) 522-0816

http://www.okhistory.org/shpo/shpom.htm 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING E-5

STATE HISTORIC PRESERVATION OFFICES E

Oregon

Parks and Recreation Department

Heritage Programs

725 Summer Street NE, Suite C

Salem, OR 97301

Phone: (503) 986-0671

Fax: (503) 986-0793

http://egov.oregon.gov/OPRD/HCD/

Pennsylvania

Pennsylvania Historical and Museum Commission

300 North Street

Harrisburg, PA 17120

Phone: (717) 787-3362

Fax: (717) 783-9924

http://www.portal.state.pa.us/portal/server.

pt?open=512&mode=2&objID=1426 

Puerto Rico

Calle Norzagaray Final Cuartel de Ballaja, 3er Piso

San Juan, PR 00906-6581

Phone: (787) 721-3737

Fax: (787) 721-3773

http://www.gobierno.pr/OECH/index.htm 

Rhode Island

Rhode Island Historical Preservation and 

Heritage Commission

Old State House

150 Benefit Street

Providence, RI 02903

Phone: (401) 222-2678

Fax: (401) 222-2968

http://www.preservation.ri.gov/ 

South Carolina

State Historic Preservation Office

Department of Archives and History

8301 Parklane Road

Columbia, SC 29223

Phone; (803) 896-6178

Fax: (803) 896-6167

http://shpo.sc.gov/ 

South Dakota

State Historic Preservation Office

State Historical Society

900 Governors Drive

Pierre, SD 57501-2217

Phone: (605) 773-3458

Fax: (605) 773-6041

http://www.sdhistory.org/HP/histpres.htm 

Tennessee

Tennessee Historical Commission

Department of Environment and Conservation

2941 Lebanon Road

Nashville, TN 37243-0442

Phone: (615) 532-1550

http://www.tn.gov/environment/history/

Texas

Texas Historical Commission

1511 Colorado

P.O. Box 12276

Austin, TX 78711-2276

Phone: (512) 463-6100

Fax: (512) 463-8222

http://www.thc.state.tx.us 

Utah

Utah Division of State History

300 South Rio Grande Street

Salt Lake City, UT 84101

Phone: (801) 533-3500

Fax: (801) 533-3567

http://history.utah.gov/

Vermont

Division for Historic Preservation

National Life Building, 2nd Floor

Montpelier, VT 05620-1201

Phone: (802) 828-3213

Fax: (803) 828-3206

http://www.historicvermont.org/ 
E-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

E STATE HISTORIC PRESERVATION OFFICES

Virginia

Department of Historic Resources

2801 Kensington Avenue

Richmond, VA 23221

Phone: (804) 367-2323

http://www.dhr.virginia.gov/ 

Washington

Department of Archeology and Historic 

Preservation

1063 South Capitol Way, Suite 106

Olympia, WA 98501

Phone: (360) 586-3065

http://www.dahp.wa.gov/ 

West Virginia

West Virginia Division of Culture and History

Historic Preservation Office

Cultural Center

1900 Kanawha Boulevard East

Charleston, WV 25305-0300

Phone: (304) 558-0220

Fax: (304) 558-2779

http://www.wvculture.org/ 

Wisconsin

Historic Preservation Division

State Historical Society of Wisconsin

816 State Street

Madison, WI 53706-1417

Phone: (608) 264-6493

http://www.wisconsinhistory.org/hp/ 

Wyoming 

Wyoming State Historic Preservation Office

Barrett Building

2301 Central Avenue

3rd Floor

Cheyenne, WY 82002

Phone: (307) 777-7697

Fax: (307) 777-6421

http://wyoshpo.state.wy.us/ 

American Samoa

c/o Executive Offices of the Governor American 

Samoa

Historic Preservation Office American Samoa 

Government

Pago Pago, American Samoa 96799

Phone: (684) 699-2316

Fax: (684) 699-2276

http://ashpo.org/

Virgin Islands

State Historic Preservation Office

Nisky Center

17 Kongens Gade

St. Thomas, VI 00802

Phone: (340) 776-8605

Fax: (340) 776-7236

http://www.dpnr.gov.vi/historic.htm 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING F-1

Appendix F

Professional Organizations 

The organizations listed below can provide information about registered design professionals and licensed contractors in or near the area where you live.

American Institute of Architects (AIA)

1735 New York Avenue, NW

Washington, DC 20006-5292

Phone: (202) 626-7300 or (800) 242-3837

Fax: (202) 626-7547

http://www.aia.org

American Society of Civil Engineers (ASCE)

International Headquarters

1801 Alexander Bell Drive

Reston, VA 20191-4400

Phone: (703) 295-6300 or (800) 548-2723

Fax: (703) 295-6319

http://www.asce.org 

Association of State Floodplain Managers (ASFPM)

2809 Fish Hatchery Road

Madison, WI 53713

Phone: (608) 274-0123

Fax: (608) 274-0696

http://www.floods.org 

International Association of Structural Movers (IASM)

1223 Morning Shore Drive, Suite 200

P.O. Box 2637

Lexington, SC 29071

Phone: (803) 951-9304

Fax: (803) 951-9314

http://www.iasm.org 
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F PROFESSIONAL ORGANIZATIONS

Insurance Institute for Business and Home Safety (IBHS)

4775 E. Fowler Avenue

Tampa, FL 33617

Phone: (813) 286-3400

Fax: (813) 286-9960 

http://www.disastersafety.org 

International Code Council (ICC)

Headquarters

500 New Jersey Avenue, NW, 6th Floor

Washington, DC 20001-2070

Phone: (888) 422-7233

Fax: (202) 599-9871

http://www.iccsafe.org 

National Association of Home Builders (NAHB)

1201 15th Street, NW

Washington, DC 20005

Phone: (202) 266-8200 or (800) 368-5242

Fax: (202) 266-8400

http://www.nahb.org 
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-1

Appendix G

Retrofitting Checklist 

Use this checklist when you follow the four steps described in this chapter. The information you record here will 

help you work with local officials, design professionals, and contractors. Use the decision-making matrices that 

follow this checklist to decide which retrofitting method is right for your home.

Step 1 – Determine the Hazards to Your Home

1. How long have you lived in your home? 

___ years

2. Was your home ever flooded during that time? 

___ yes ___ no 

(If your answer is yes, go to question 3; if your answer is no, go to question 14.)

3. How many times has your home been flooded? ________

4. What were the dates of flooding?

Flood #1 ______________ Flood #4 ______________

Flood #2 ______________ Flood #5 ______________

Flood #3 ______________

For each flood, answer questions 5 through 13 as best you can.
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5. To your knowledge, were frequencies assigned to any of the floods (e.g., 2-percent-annualchance flood, 1-percent-annual-chance flood)? If so, what were they?

Flood #1 _________________________________________________________________________

Flood #2 _________________________________________________________________________

Flood #3 _________________________________________________________________________

Flood #4 _________________________________________________________________________

Flood #5 _________________________________________________________________________

6. How high did the floodwaters rise in your home? 

(If you can, state the height of the water above the lowest floor, including the basement floor.)

Flood #1 ______________ Flood #4 ______________

Flood #2 ______________ Flood #5 ______________

Flood #3 ______________

7. About how long did your home remain flooded? 

(You can give your answer in days, weeks, or months, as appropriate.)

Flood #1 ______________ Flood #4 ______________

Flood #2 ______________ Flood #5 ______________

Flood #3 ______________

8. Did you have any warning before your home was flooded? If so, how much warning? 

(You can give your answer in days or hours as appropriate.)

Flood #1 ___ No Warning ___ Warning _______ Days/Hours

Source of warning (news report, local officials, firsthand observation): _________________________

Flood #2 ___ No Warning ___ Warning _______ Days/Hours

Source of warning (news report, local officials, firsthand observation): _________________________

Flood #31 ___ No Warning ___ Warning _______ Days/Hours

Source of warning (news report, local officials, firsthand observation): _________________________

Flood #4 ___ No Warning ___ Warning _______ Days/Hours

Source of warning (news report, local officials, firsthand observation): _________________________
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-3

RETROFITTING CHECKLIST G

Flood #5 ___ No Warning ___ Warning _______ Days/Hours

Source of warning (news report, local officials, firsthand observation): _________________________

9. Did the floodwaters cause scour and/or erosion around your home or elsewhere on your lot? 

If so, describe the effects.

Flood #1 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred

Description _______________________________________________________________________

________________________________________________________________________________

Flood #2 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred

Description _______________________________________________________________________

________________________________________________________________________________

Flood #3 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred

Description _______________________________________________________________________

________________________________________________________________________________

Flood #4 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred

Description _______________________________________________________________________

________________________________________________________________________________

Flood #5 ___ No Erosion/Scour Occurred ___ Erosion/Scour Occurred

Description _______________________________________________________________________

________________________________________________________________________________

10. Was your home damaged by wave action or the impact of ice or other floodborne debris? 

If so, describe the damage.

Flood #1 ___ No Waves or Debris ___ Waves ___ Debris

Description of Damage ______________________________________________________________

________________________________________________________________________________

Flood #2 ___ No Waves or Debris ___ Waves ___ Debris

Description of Damage ______________________________________________________________

________________________________________________________________________________
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Flood #3 ___ No Waves or Debris ___ Waves ___ Debris

Description of Damage ______________________________________________________________

________________________________________________________________________________

Flood #4 ___ No Waves or Debris ___ Waves ___ Debris

Description of Damage ______________________________________________________________

________________________________________________________________________________

Flood #5 ___ No Waves or Debris ___ Waves ___ Debris

Description of Damage ______________________________________________________________

________________________________________________________________________________

11. How difficult and/or expensive was cleaning up after the floodwaters receded?

(If you can, describe what you had to do to clean up both inside your home and around your lot, 

how long the cleanup took, and how much you spent on cleanup.)

Flood #1 Cleanup Description ______________________________________________________

________________________________________________________________________________

Cost $ _______________ Time _______________

Flood #2 Cleanup Description ______________________________________________________

________________________________________________________________________________

Cost $ _______________ Time _______________

Flood #3 Cleanup Description ______________________________________________________

________________________________________________________________________________

Cost $ _______________ Time _______________

Flood #4 Cleanup Description ______________________________________________________

________________________________________________________________________________

Cost $ _______________ Time _______________

Flood #5 Cleanup Description ______________________________________________________

________________________________________________________________________________

Cost $ _______________ Time _______________
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-5

RETROFITTING CHECKLIST G

12. What was the total cost to repair all flood damage, not including the cleanup costs listed 

above?

Flood #1 $______________ Flood #4 $______________

Flood #2 $______________ Flood #5 $______________

Flood #3 $______________

13. What was the total value of all home contents (furnishings, belongings, etc.) damaged by 

flooding?

Flood #1 $______________ Flood #4 $______________

Flood #2 $______________ Flood #5 $______________

Flood #3 $______________

14. Is your home either in or near one of the shaded areas on the wind hazard map in Figure 4-1?

If you are not sure how to interpret Figure 4-1, your local officials and design professional can help 

you. 

___ yes ____ no

15. Has your home ever been damaged by a hurricane or other high-wind event? 

___ yes ___ no. 

 If your answer is yes, note how many times and describe both the damage and the repairs made. 

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

16. Is your home either in or near one of the shaded areas on the earthquake hazard map in 

Figure 4-2? If you are not sure how to interpret Figure 4-2, your local officials and design professional 

can help you. 

___ yes ___ no
G-6 SIX WAYS TO PROTECT YOUR HOME FROM FLOODING HOMEOWNER’S GUIDE TO RETROFITTING

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17. Has your home ever been damaged by an earthquake?

___ yes ___ no. 

If your answer is yes, note how many times and describe both the damage and the 

repairs made. 

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

18. Has your home ever been damaged by other hazard events, such as fires or landslides? 

___ yes ___ no. 

If your answer is yes, note how many times and describe both the damage and the repairs made. 

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-7

RETROFITTING CHECKLIST G

Step 2 – Inspect Your Home

Provide as much of the following information as you can about your home.

1. When was your home built? _____

2. Construction type (see Section 3.2.1; check all that apply): 

 ___ frame ___ masonry veneer ___ masonry ___ manufactured home

3. Foundation type (see Section 3.2.2; check all that apply):

___ basement (subgrade on all sides) ___ walkout-on-grade basement ___ crawlspace 

___ slab-on-grade ___ piers ___ posts/columns ___ piles

4. Describe any other damage and repairs or other additions to your home other than those you 

described in Step 1. Other damages would include foundation settlement, dry rot, and termite 

damage.

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

To answer questions 5 through 9, you will need to have at least a rough idea of the DFE for your retrofitting project. If you don’t have enough information to answer these questions now, go to Step 3 

and determine your DFE when you talk with your local official(s). 

5. Approximate difference between elevation of lowest floor (including basement) and design 

flood elevation (DFE) (see Figure 4-3): 

___ feet

6. Interior utilities below the DFE (check all that apply): 

___ furnace ___ ductwork ___ hot water heate ___ electrical panel ___ electrical outlets 

___ electrical switches ___ baseboard heaters ___ sump pumps ___ fuel tanks

other ____________________________________________________________________________
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7. Exterior utilities below the DFE (check all that apply):

___ air conditioning / heat pump compressor ___ electric meter ___ fuel tank 

___ septic tank ___ well ___ gas meter

other_____________________________________________________________________________

8. Major appliances below the DFE (check all that apply): 

___ washer ___ dryer ___ refrigerator ___ freezer

other ____________________________________________________________________________

9. How many drains (such as sink, tub, and floor drains) and toilets are below the DFE? _______
HOMEOWNER’S GUIDE TO RETROFITTING SIX WAYS TO PROTECT YOUR HOME FROM FLOODING G-9

RETROFITTING CHECKLIST G

Step 3 – Check with Your Local Officials

When you meet with your local official(s), be sure to discuss the issues below. Also, make note of the 

information you receive from the local officials. (You may find that you will need to talk with more 

than one person to get all the information you need.)

1. Explain your retrofitting needs, go over the information you recorded in Steps 1 and 2, and discuss any 

preferences you may have regarding the retrofitting methods described in Chapter 3.

2. Provide the official with photographs of your home and a copy of a plat map that shows the dimensions 

of your lot and the location of your home. If you do not have a plat map, ask how you can get one.

3. Ask whether your home is in the regulatory floodplain. If the answer is yes, ask what the BFE is at your 

home and whether your home is in the floodway or Coastal High Hazard Area (Zone V). Ask whether 

any restudies or revisions are underway that might provide updated flood hazard information for the area 

where your home is located. Also, ask for additional flood hazard information concerning characteristics 

such as flow velocity, the potential for wave action and debris flow, rates of rise and fall, warning time, 

and duration of inundation. This additional information may be useful to your design professional.

4. Ask whether your home is subject to your community’s regulatory requirements concerning Substantially 

Damaged structures or whether the retrofitting measure you are considering would subject your home to 

Substantial Improvement requirements. (See the definitions of Substantial Improvement and Substantial 

Damage in Section 2.5 and Section 3.1.1)

5. Ask whether your home is subject to high winds, earthquakes, and other hazards, such as wildfires. 

Refer to the maps in Figures 4-1 and 4-2.

6. Ask whether your State and/or community enforces building codes or other regulations that could affect 

your retrofitting decision, including any floodplain management regulations more stringent than those 

required by the NFIP. For example, ask whether the State or community requires freeboard for flood 

protection measures.

7. In your discussion of building codes, ask whether retrofitting will require that you upgrade other components of your home (such as electrical and plumbing systems) to meet current code requirements.

8. Ask about the types of permits and fees that may be required in connection with the retrofitting methods 

you are considering.

9. Ask whether the official is aware of any Federal, State, or local historic preservation regulations that may 

affect your property. If necessary, have the official follow up with the SHPO (see Appendix E) to be sure 

that your retrofitting project is in compliance with all preservation laws.

10. Ask about Federal, State, and local programs that provide financial assistance for certain types of homeowner flood protection retrofitting projects. Ask whether you are eligible for assistance.

11. Go through the appropriate decision-making matrix (see Section 4.2) with the official and discuss any 

questions you may have about the advantages and disadvantages of the alternative retrofitting methods. 

12. Ask for any guidance that local officials can provide to help you find a good contractor or design 

professional.
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Step 4 – Consult a Design Professional and Retrofitting Contractor

Initial Meeting

1. Explain your retrofitting needs; go over the information you recorded in Steps 1 and 2; discuss the 

results of your meeting with your local official(s), including the decision-making matrix; and discuss 

any preferences you may have regarding retrofitting methods you selected in 

Step 3. 

2. Verify that the design professional is licensed and registered in the State where the work will be done.

3. Verify that the contractor is licensed, bonded, and insured as required by State and local laws.

4. Ask for references and proof of proper bonds and insurance, including disability and workers’ 

compensation.

5. Decide whether you, the design professional, or the contractor will be responsible for obtaining 

and managing the work of subcontractors and for obtaining all permits required by State and local 

agencies.

6. Schedule a site visit.

Site Visit

1. Ask the design professional or contractor to tell you about any characteristics of your home or lot that 

would affect your selection of a retrofitting method.

2. Once you decide on a retrofitting method, ask for a written estimate of the project cost and schedule.

Contract

1. If you are satisfied with the cost estimate and schedule, get a written, signed, and dated contract that 

describes the work to be done and that states the estimated cost, the payment schedule, and the start 

and completion dates of the work.

2. Ask whether the contractor will provide a warranty or guarantee for the work performed. Any warranty 

or guarantee should be written into the contract. The contract should state the terms of the warranty or 

guarantee, who is responsible for honoring it, and how long it will remain valid.

Notes

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

____________________________________________________________________________________

FEMA P-321

Catalog No. 08322-1

FEMA

U. S. DEPARTMENT OF

HOMELAND SECURITY

U. S. DEPARTMENT OF

HOMELAND SECURITY

FEMA P-765

Catalog No. 09092-3

FEMA

U. S. DEPARTMENT OF

HOMELAND SECURITY

FEMA P-312

Catalog No. 09349-6