Performance of Buildings and 

Nonstructural Components 

in the 2014 South Napa 

Earthquake 

FEMA P-1024 / February 2015 


 


 


 


 


 

February 2015 FEMA P-1024 

Performance of Buildings and Nonstructural 

Components in the 

2014 South Napa Earthquake 

Prepared by 

APPLIED TECHNOLOGY COUNCIL 

201 Redwood Shores Parkway, Suite 240 

Redwood City, California 94065 

http://www.atcouncil.org/ 

Prepared for 

FEDERAL EMERGENCY MANAGEMENT AGENCY
 

Michael Mahoney, Project Officer
 

Washington, D.C. 

ATC MANAGEMENT AND OVERSIGHT
 

Christopher Rojahn (Program Executive) 

Jon A. Heintz (Program Manager) 

Ayse Hortacsu (Project Manager) 

PRINCIPAL AUTHORS
 

John Gillengerten (co-Project Technical Director) 

Maryann Phipps (co-Project Technical Director) 

CONTRIBUTING AUTHORS
 

Kelly Cobeen 

Bret Lizundia 

Joseph Maffei 

Joshua Marrow 

Bill Tremayne 

PROJECT WORKING GROUP 

Veronica Crothers 

Sarah Durphy 

Jonas Houston 

Alix Kottke 

Chiara McKenney 

Karl Telleen 

Noelle Yuen 

PROJECT REVIEW PANEL 

Dan Kavarian 

Roy Lobo 

Khalid Mosalam 

Marko Schotanus 

Fred Turner 

February 2015 
 

 

Notice 

Any opinions, findings, conclusions, or recommendations expressed in this publication do not 

necessarily reflect the views of the Applied Technology Council (ATC), the Department of 

Homeland Security (DHS), or the Federal Emergency Management Agency (FEMA). 

Additionally, neither ATC, DHS, FEMA, nor any of their employees, makes any warranty, 

expressed or implied, nor assumes any legal liability or responsibility for the accuracy, 

completeness, or usefulness of any information, product, or process included in this publication. 

Users of information from this publication assume all liability arising from such use. 
 

 

 

 

 

 

 

 

 

 

 

Preface
 

California is subject to frequent damaging earthquakes, and each one 

presents an opportunity to study the impacts, improve our understanding of 

how buildings perform when subjected to strong ground shaking, and update 

building codes and standards for improved building performance. The 

Federal Emergency Management Agency (FEMA) established the Mitigation 

Assessment Team (MAT) program to investigate post-disaster building 

performance and develop recommendations that address improvements in 

building design and construction, code development, enforcement, and 

mitigation activities that will lead to greater resistance to hazard events. The 

FEMA MAT program, however, is not currently set up to investigate the 

performance of buildings after earthquakes. 

On August 24, 2014, a magnitude-6.0 earthquake occurred in Napa, 

California. In response to this earthquake, the Special Projects task of the 

National Earthquake Technical Assistance Program (NETAP) under FEMA 

Contract HSFE60-12-D-024 with the Applied Technology Council (ATC) 

was used to fund an investigation. At the time, this event had not yet been 

declared a federal disaster, and disaster funds were therefore not available. 

Because of limitations to this funding, some issues, such as performance of 

lifelines or building investigations in additional areas, could not be 

investigated. 

Past earthquakes in California have resulted in significant improvements to 

national and local building codes, including the 1933 Long Beach earthquake 

(which affected schools and unreinforced masonry structures), the 1971 San 

Fernando earthquake (which affected hospitals and non-ductile concrete 

structures), the 1989 Loma Prieta earthquake (which affected soft story wood 

light-frame construction), and the 1994 Northridge earthquake (which 

affected steel moment frame structures). For the 2014 South Napa 

earthquake, work was focused on documenting the observed performance of 

buildings and nonstructural components in order to lead into future 

improvements in future building codes, and to do so within six months. 

ATC is indebted to the vision of Michael Mahoney (FEMA Project Officer), 

and leadership of John Gillengerten and Maryann Phipps who served as CoProject Technical Directors and principal authors for this work. Contributing 

FEMA P-1024 Preface iii 
 

 

 

 

 

 

 

 

 

authors Kelly Cobeen, Bret Lizundia, Joseph Maffei, Joshua Marrow, and 

Bill Tremayne assisted in the development of postearthquake observations 

and conclusions. Veronica Crothers, Sarah Durphy, Jonas Houston, Alix 

Kottke, Chiara McKenney, Karl Telleen, and Noelle Yuen were instrumental 

in the completion of field investigative work within the limited time 

available. The Project Review Panel, consisting of Dan Kavarian, Roy Lobo, 

Khalid Mosalam, Marko Schotanus, and Fred Turner, provided technical 

review of the report. The names and affiliations of all who participated on 

the project team are provided in the list of Project Participants at the end of 

this publication. 

ATC gratefully acknowledges information provided by Brad Harward, 

Shawn Huff, Bruce Maison, Terrence Paret, Chris Tokas, Mark Quattrocchi, 

and Richard Weinert, who generously shared their observations with the 

report authors, and the residents of Napa who provided valuable information 

and assistance during the many visits to the region. 

ATC also gratefully acknowledges Ayse Hortacsu for ATC project 

management, Veronica Heintz and Jack Lakes for assistance in compiling the 

field data, and Amber Houchen for ATC report production services. 

Jon A. Heintz Christopher Rojahn 

ATC Director of Projects ATC Executive Director 

iv Preface FEMA P-1024 
Table of Contents
 

Preface........................................................................................................... iii 

List of Figures............................................................................................... xi 

List of Tables ........................................................................................... xxvii
 

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

1.1 Project Goal .............................................................................. 1-1 

1.2 Investigation Process ................................................................ 1-2 

1.2.1 Survey Process ............................................................ 1-2 

1.2.2 Scope of Investigation ................................................. 1-3 

1.2.3 Site Investigations ....................................................... 1-4 

1.3 Report Organization ................................................................. 1-4 

2. Seismicity and Ground Motion Data.............................................. 2-1 

2.1 West Napa Fault and Surrounding Seismicity .......................... 2-1 

2.2 The South Napa Earthquake ..................................................... 2-3 

2.3 Impact of the South Napa Earthquake ...................................... 2-9 

2.4 West Napa Fault Rupture and Afterslip ................................. 2-11 

2.5 Summary ................................................................................ 2-14 

2.6 Recommendations .................................................................. 2-14 

3. Performance of Buildings Near Station N016 ................................ 3-1 

3.1 Survey Area .............................................................................. 3-1 

3.2 Survey Method ......................................................................... 3-1 

3.3 Building Site Information......................................................... 3-3 

3.4 Building Construction Data ...................................................... 3-3 

3.5 Model Building Type ............................................................... 3-5 

3.6 Performance Modifiers ............................................................. 3-7 

3.7 Nonstructural Elements ............................................................ 3-7 

3.8 General Damage ....................................................................... 3-7 

3.8.1 General Damage Classification ................................... 3-8 

3.8.2 ATC-13 Damage State ................................................ 3-8 

3.9 Structural Performance ............................................................. 3-9 

3.10 Nonstructural Damage ............................................................ 3-11 

3.11 Injuries or Fatalities................................................................ 3-13 

3.12 Functionality ........................................................................... 3-13 

4. Performance of Selected Buildings ................................................. 4-1 

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

4.2 Newer Construction .................................................................. 4-3 

4.2.1 Three-Story Commercial Building, Main Street
 

(Building L1)............................................................... 4-3 

4.2.2	 Three-Story Office Building, Franklin Street 

(Building Z1)............................................................... 4-5 

FEMA P-1024	 Table of Contents v 
 

4.2.3	 Five-Story Hotel, 1st Street (Building Z5) .................4-10 

4.3 Older Construction Excluding URM ......................................4-15 

4.3.1 Three-Story Commercial Building, 1st Street 

(Building I1) ..............................................................4-15 

4.3.2 Historic Post Office Building (Building Z3) .............4-18 

4.3.3 One-Story Retail Building, Clay Street (Building 

Z6) .............................................................................4-20 

4.3.4 Napa County Administration Offices (Building 

F2)..............................................................................4-24 

4.3.5 Napa County Hall of Justice (Building F3) ...............4-27 

4.3.6 Two-Story Retail Building, Napa Center (Building 

Z2) .............................................................................4-32 

4.3.7	 Napa County Courthouse, Brown Street (Building 

D1).............................................................................4-34 

4.4 Unretrofitted URM Construction............................................4-36 

4.4.1	 Two-Story Commercial Building, Brown Street 

(Building E1).............................................................4-37 

4.4.2	 One-Story Restaurant Building, 1st Street (Buildings 

B2/B2A).....................................................................4-39 

4.5 Retrofitted URM Construction with Significant Damage ......4-41 

4.5.1	 Three-Story Office Building, 2nd Street, Napa, CA 

(Building E5).............................................................4-41 

4.5.2	 Two-Story Building, 1st Street (Building I2) .............4-44 

4.5.3	 Two-Story URM Building, 1st Street (Building 

J4) ..............................................................................4-49 

4.6 Retrofitted URM Construction with Limited Damage ...........4-52 

4.6.1 Three-Story Theater Building, Main Street

 (Building L2) ............................................................4-52 

4.6.2	 One-Story Restaurant Building, Main Street 

(Building L4).............................................................4-55 

4.6.3	 Two-Story Building, 3rd Street (Building M1) ..........4-58 

4.6.4 Two-Story Commercial Building, Main Street 

(Building A1).............................................................4-62 

4.6.5	 Two-Story Restaurant Building, 1st Street (Building 

A2).............................................................................4-64 

4.6.6	 One-Story Restaurant Building, Main Street 

(Building A4).............................................................4-67 

4.6.7	 One-Story Restaurant Building, Main Street 

(Building E7).............................................................4-69 

4.7 Summary.................................................................................4-70 

4.8 Recommendations ...................................................................4-71 

5. Performance of Healthcare Facilities .............................................5-1 

5.1 Introduction...............................................................................5-1 

5.2 Performance of Hospitals .........................................................5-2 

5.2.1	 Queen of the Valley Hospital – Napa (OSHPD 

Facility ID 10362) .......................................................5-3 

5.2.2 Sutter Solano Medical Center (OSHPD Facility ID 

12525) ........................................................................5-13 

5.2.3 Kaiser Foundation Hospital – Rehabilitation Center 

Vallejo (OSHPD Facility ID 13142) .........................5-15 

5.2.4 Sonoma Valley Hospital (OSHPD Facility 

ID 11064)...................................................................5-16 

vi Table of Contents FEMA P-1024
 
 

5.2.5	 St. Helena Hospital Center for Behavioral Health 

(OSHPD Facility ID 11013) ...................................... 5-17 

5.2.6 St. Helena Hospital (OSHPD Facility ID 10366)...... 5-18 

5.3 Performance of Skilled Nursing Facilities ............................. 5-21 

5.4 Performance of Medical Office Buildings ............................. 5-24 

5.5 Summary ................................................................................ 5-24 

5.6 Recommendations .................................................................. 5-25 

6. Performance of School Facilities ..................................................... 6-1 

6.1 Introduction .............................................................................. 6-1 

6.2 Napa Valley Unified School District ........................................ 6-1 

6.2.1 Suspended Pendant Fixtures ........................................ 6-3 

6.2.2 Furniture ...................................................................... 6-8 

6.2.3 Ceilings...................................................................... 6-13 

6.2.4 Interior Partitions ....................................................... 6-14 

6.2.5 Glazing ...................................................................... 6-15 

6.2.6 Mechanical and Plumbing Systems ........................... 6-16 

6.2.7 Electrical Systems ..................................................... 6-19 

6.2.8 Concrete and Asphalt Cracking ................................. 6-22 

6.2.9 Additional Observations ............................................ 6-23 

6.3 Other School Facilities within Napa Valley ........................... 6-24 

6.3.1 Justine Siena .............................................................. 6-24 

6.3.2	 Napa Education Center and District Auditorium, 

Napa .......................................................................... 6-26 

6.4 Vallejo City Unified School District ...................................... 6-28 

6.5 Summary ................................................................................ 6-28 

6.5 Recommendations .................................................................. 6-28 

7. Performance of Residential Construction...................................... 7-1 

7.1 Introduction .............................................................................. 7-1 

7.2 Selected Observations .............................................................. 7-2 

7.2.1 Browns Valley House No. 1 ........................................ 7-2 

7.2.2 Browns Valley House No. 2 ........................................ 7-5 

7.2.3 Browns Valley House No. 3 ........................................ 7-7 

7.2.4 Napa House No. 1 ....................................................... 7-9 

7.2.5 Napa House No. 2 ..................................................... 7-10 

7.2.6 Napa House No. 3 ..................................................... 7-11 

7.2.7 Napa House No. 4 ..................................................... 7-12 

7.3 Residential Flood Retrofits..................................................... 7-13 

7.4 Summary ................................................................................ 7-14 

7.4.1 Masonry Chimneys ................................................... 7-14 

7.4.2 Unbraced Cripple Wall Foundations......................... 7-17 

7.4.3 Fault Rupture and Afterslip ....................................... 7-18 

7.5 Recommendations .................................................................. 7-18 

8. Performance of Manufactured Housing ........................................ 8-1 

8.1 Introduction .............................................................................. 8-1 

8.2 Manufactured Homes ............................................................... 8-1 

8.3 Regulatory Background ............................................................ 8-3 

8.4 Gravity and Seismic Support Systems ..................................... 8-5 

8.5 Overall Mobile Home Park Observations .............................. 8-15 

FEMA P-1024	 Table of Contents vii 
 

 

9. 

10. 

8.6	 Detailed Observations at Oaktree Vineyard Mobile Home
 

Park.........................................................................................8-17 

8.7 Detailed Observations at Salvador Mobile Estates .................8-18 

8.8 Detailed Observations at Napa Valley Mobile Home Park ....8-22 

8.9 Summary.................................................................................8-24 

8.10 Recommendations ...................................................................8-25 

Performance of Wine Industry Facilities .......................................9-1 

9.1 Introduction...............................................................................9-1 

9.2 Winery Seismic Risk ................................................................9-1 

9.2.1 Direct Loss and Business Disruption...........................9-2 

9.2.2 Earthquake Insurance ...................................................9-4 

9.3 Wine Barrel Storage .................................................................9-4 

9.4 Wine Tanks and Catwalks ........................................................9-6 

9.5 Bottle and Case Good Storage ..................................................9-7 

9.6 Winery Building Performance ..................................................9-7 

9.6.1 Historic Winery Building, Napa ..................................9-8 

9.6.2 Wine Co-Op Facility, Napa .........................................9-8 

9.6.3 Winery Facility, Napa ..................................................9-8 

9.6.4 Barrel Warehouse, Napa..............................................9-9 

9.7 Summary...................................................................................9-9 

9.7.1 Structural Damage .......................................................9-9 

9.7.2 Wine Barrel Storage ..................................................9-10 

9.7.3 Steel Tanks and Catwalks..........................................9-11 

9.7.4 Bottle and Case Good Storage ...................................9-11 

9.8 Recommendations ...................................................................9-11 

9.8.1 Wine Barrel Storage ..................................................9-12 

9.8.2 Wine Tanks ................................................................9-13 

9.8.3	 Occupant Seismic Safety, Response, and 

Recovery....................................................................9-13 

Performance of Nonstructural Components................................10-1 

10.1 Introduction.............................................................................10-1 

10.2 Exterior Enclosures .................................................................10-2 

10.2.1	 Glazing, Glazed Curtain Walls, and Storefront 

Systems ......................................................................10-2 

10.2.2 Light-Frame Curtain Wall Systems ...........................10-5 

10.2.3 Precast Cladding ........................................................10-6 

10.3 Interior Partitions ....................................................................10-7 

10.4 Ceilings...................................................................................10-9 

10.4.1 Gypsum Wallboard and Plaster Ceilings .................10-10 

10.4.2 Suspended Acoustic Tile Ceilings ...........................10-11 

10.5 Mechanical, Electrical, and Plumbing Equipment ................10-13 

10.6 Piping Systems......................................................................10-15 

10.7 Contents ................................................................................10-19 

10.8 Solar Arrays..........................................................................10-23 

10.8.1 Ground-Mounted Solar Array, Vallejo ....................10-24 

10.8.2 Roof-Mounted Solar Canopy, Vallejo .....................10-25 

10.8.3	 Roof-Mounted Low-Profile Unattached Array,
 

Vallejo .....................................................................10-28 

10.8.4 Roof-Mounted Solar Canopy, Napa ........................10-29 

viii Table of Contents FEMA P-1024
 
 

 

10.8.5 Roof-Mounted Low-Profile Arrays Including 

Ballasted and Mechanical Attached Systems .......... 10-30 

10.9 Summary .............................................................................. 10-32 

10.10 Recommendations ................................................................ 10-33 

11.	 Postearthquake Safety Evaluation of Buildings .......................... 11-1 

11.1 Introduction ............................................................................ 11-1 

11.2 Postearthquake Safety Evaluation Program Management ...... 11-2 

11.2.1 Response of Cal OES ................................................ 11-2 

11.2.2 Response of City of Napa .......................................... 11-4 

11.2.3 Response of City of Vallejo ...................................... 11-4 

11.2.4 Response of the Office of Statewide Health Planning 

and Development....................................................... 11-4 

11.2.5	 Response of the Napa Valley Unified School 

District....................................................................... 11-5 

11.3 Conduct of the Postearthquake Safety Assessment Program . 11-5 

11.3.1 Use of Evaluation Forms ........................................... 11-5 

11.3.2 Assignment of Resources .......................................... 11-6 

11.3.3	 Compensation of Safety Assessment Program
 

Evaluators.................................................................. 11-6 

11.3.4 Local Ordinance Authorization for Placarding ......... 11-6 

11.4 Observations........................................................................... 11-6 

11.4.1 Multiple Postings ....................................................... 11-7 

11.4.2 Inappropriate Use of Placards ................................... 11-8 

11.4.3	 Inconsistent Communication with the Public 

Regarding the Meaning of the Placards................... 11-11 

11.5 Summary .............................................................................. 11-12 

11.6 Recommendations ................................................................ 11-13 

12.	 Barricading of Unsafe Areas ......................................................... 12-1 

12.1 Available Resources ............................................................... 12-1 

12.2 Observations and Issues ......................................................... 12-2 

12.2.1 Initial Barricade Distances ........................................ 12-2 

12.2.2 Transitions to Longer-Term Barricades .................... 12-4 

12.2.3 Exiting into Cordoned Areas ..................................... 12-5 

12.2.4 Protecting Adjacent Buildings................................... 12-6 

12.3 Recommendations .................................................................. 12-6 

12.4 Summary and Recommendations ........................................... 12-7 

13.	 Summary and Conclusions............................................................ 13-1 

Appendix A: Survey Forms and Instructions......................................... A-1 

A.1 Modifications to Survey Form and Instructions ...................... A-1 

Appendix B: Recovery Advisories.................. ......................................... B-1 

B.1 Earthquake Strengthening of Cripple Walls in Wood-Frame 

Dwellings .................................................................................B-1 

B.1.1 Purpose and Background .............................................B-1 

B.1.2 Scope of Document .....................................................B-2 

B.2 Repair of Earthquake-Damaged Masonry Fireplace 

Chimneys ..................................................................................B-3 

FEMA P-1024	 Table of Contents ix 
References .................................................................................................. C-1 

Project Participants ................................................................................... D-1 

x Table of Contents FEMA P-1024
 
List of Figures
 

Figure 2-1 2008 earthquake probabilities from the USGS website ..... 2-2 

Figure 2-2 Geologic map showing fault lines ...................................... 2-3 

Figure 2-3 Surface faulting (yellow lines) produced by the August 24, 

2014 South Napa earthquake ............................................. 2-5 

Figure 2-4 USGS ShakeMap ............................................................... 2-6 

Figure 2-5 Ground Motion recordings from Napa College, CGS 

Station 68150 ..................................................................... 2-7 

Figure 2-6 Ground Motion recordings from Main Street, USGS 

NCSN Station N016 ........................................................... 2-8 

Figure 2-7 Ground Motion recordings from Fire Station No. 3 

USGS NSMP 1765 ............................................................ 2-9 

Figure 2-8 Comparison of code-based versus resultant pseudo-spectral 

acceleration (PSA) spectra on Site Class D for: (a) Napa 

Valley College; (b) Main Street; and (c) Fire 

Station No. 3 .................................................................... 2-10 

Figure 2-9 Observation of afterslip following the South Napa 

earthquake: (a) 11 hours after the earthquake; (b) 4 

months after the earthquake ............................................. 2-12 

Figure 2-10 Afterslip map ................................................................... 2-13 

Figure 3-1 Aerial photo showing the surveyed area ............................ 3-2 

Figure 3-2 Distribution (by count) of buildings by date of original 

construction........................................................................ 3-4 

Figure 3-3 Distribution (by count) of buildings by occupancy type 

(of a total of 68 buildings) ................................................. 3-5 

Figure 3-4 Distribution (by count) of buildings by original structural 

system (of a total of 68 buildings) ..................................... 3-6 

Figure 3-5 Distribution (by count) of unreinforced masonry building 

retrofits (of a total 28 URM buildings) .............................. 3-7 

Figure 3-6 Distribution of building damage according to general 

damage classification ......................................................... 3-8 

FEMA P-1024 List of Figures xi 
Figure 3-7 Distribution of building damage according to ATC-13 

damage states .....................................................................3-9 

Figure 3-8 Damage comparison between unretrofitted and retrofitted 

URM buildings.................................................................3-11 

Figure 3-9 Number of buildings where select types of nonstructural 

damage was observed .......................................................3-12 

Figure 3-10 Distribution of parapet performance ................................3-12 

Figure 3-11 Building functionality: duration (in days) after earthquake 

to resume full functionality ..............................................3-14 

Figure 4-1 Key map providing alphanumeric designations for 

buildings within the 1,000 foot radius around Station 

N016...................................................................................4-2 

Figure 4-2 Key map providing alphanumeric designations for 

buildings investigated but located outside of the 1,000 foot 

radius around Station N016................................................4-3 

Figure 4-3 Exterior view of building ...................................................4-4 

Figure 4-4 Damage to steel studs due to out-of-plane buckling of 

brace ...................................................................................4-5 

Figure 4-5 Out-of-plane wall anchor of adjacent building penetrated 

drywall................................................................................4-5 

Figure 4-6 Exterior view of building ...................................................4-6 

Figure 4-7 Damaged studs in exterior wall ..........................................4-7 

Figure 4-8 Bowed wall separated from floor.......................................4-8 

Figure 4-9 Detail from original drawings showing connection of
 

exterior wall to each floor ..................................................4-8 

Figure 4-10 Failed wall anchor at bowed wall .......................................4-9 

Figure 4-11 Exterior wall, cracked plaster.............................................4-9 

Figure 4-12 Dislodged adhered veneer ................................................4-10 

Figure 4-13 Exterior view of building .................................................4-11 

Figure 4-14 Cracking in spandrel in concrete stair core ......................4-12 

Figure 4-15 Adhered veneer damaged during the earthquake .............4-13 

Figure 4-16 Photo showing failed anchored veneer .............................4-13 

xii List of Figures FEMA P-1024 
 

 

 

Figure 4-17 Stone masonry veneer, showing where loose units have 

been removed ................................................................... 4-14 

Figure 4-18 Sprinkler impacted HVAC components and 

discharged ........................................................................ 4-14 

Figure 4-19 Exterior view of building ................................................. 4-15 

Figure 4-20 Damage to canopy due to falling brick ............................ 4-16 

Figure 4-21 Minor damage to suspended ceilings ............................... 4-17 

Figure 4-22 Convection oven with failed support leg ......................... 4-17 

Figure 4-23 Exterior view of building................................................. 4-18 

Figure 4-24 Damage to corner pier...................................................... 4-19 

Figure 4-25 Lateral shifting at sill line ................................................ 4-19 

Figure 4-26 Glazing damage. .............................................................. 4-20 

Figure 4-27 Shoring of wall with damaged pilasters ........................... 4-21 

Figure 4-28 Damaged pilaster-to-roof beam connection ..................... 4-22 

Figure 4-29 Cracked sprinkler pipe ..................................................... 4-22 

Figure 4-30 Suspended ceiling damage ............................................... 4-23 

Figure 4-31 Overturned store fixture, loss of contents ........................ 4-23 

Figure 4-32 Evidence of pipe motion in penthouse partition wall ...... 4-25 

Figure 4-33 Ceiling and duct damage .................................................. 4-25 

Figure 4-34 Ceiling removed due to water damage, third floor .......... 4-26 

Figure 4-35 Third floor of building after the earthquake .................... 4-26 

Figure 4-36 Exterior view, 1974 wing ................................................. 4-27 

Figure 4-37 Exterior view, 1989 wing ................................................. 4-28 

Figure 4-38 CMU face shell spalling, typical at base of walls ............ 4-28 

Figure 4-39 Floor finish damage due to pounding at the seismic joint 

indicated by the arrow ...................................................... 4-29 

Figure 4-40 CMU damage at precast concrete panels containing the 

window ............................................................................ 4-29 

Figure 4-41 Anchor failure, rooftop cooling tower 1974 wing ........... 4-30 

FEMA P-154 List of Figures xiii 
 

 

Figure 4-42 Housekeeping slab failure, chiller in 1974 wing 

penthouse ..........................................................................4-31 

Figure 4-43 Ceiling damage at seismic joint .......................................4-31 

Figure 4-44 Exterior view of building .................................................4-32 

Figure 4-45 Water pressure from broken sprinkler line created a hole 

in the exterior cladding....................................................4-33 

Figure 4-46 Damaged sprinkler pipe ...................................................4-34 

Figure 4-47 East façade of historic URM courthouse..........................4-35 

Figure 4-48 Close-up of damage at top of the wall ..............................4-36 

Figure 4-49 Failure of URM south wall...............................................4-37 

Figure 4-50 Wooden barrier constructed on the roof a building 

neighboring a masonry wall at risk of collapse ................4-38 

Figure 4-51 Failure of stone masonry east wall ...................................4-38 

Figure 4-52 HVAC equipment damaged by falling stones ..................4-39 

Figure 4-53 Front elevation of Buildings B2/B2A ..............................4-39 

Figure 4-54 Collapsed URM wall and ceiling in dining area ..............4-40 

Figure 4-55 Photographs of building: (a) circa 1910 and (b) 2014 ......4-42 

Figure 4-56 Collapse of URM walls supporting a corner cupola ........4-43 

Figure 4-57 Collapse of the URM wall at a corner cupola ..................4-43 

Figure 4-58 Close-up of steel tube and masonry anchor at corner 

cupola ...............................................................................4-44 

Figure 4-59 Front façade showing damage and UNSAFE placard 

before scaffolding was installed.......................................4-45 

Figure 4-60 Cracking on east side of the tower feature .......................4-47 

Figure 4-61 Top of concrete shear wall at roof level behind the tower 

feature...............................................................................4-47 

Figure 4-62 Steel tube bracing at parapet ............................................4-48 

Figure 4-63 Lath and plaster ceiling damage and temporary taping at 

cracks and spalls ...............................................................4-49 

Figure 4-64 Exterior view of building .................................................4-50 

Figure 4-65 Cracking in URM on south façade ...................................4-51 

xiv List of Figures FEMA P-1024 
 

 

Figure 4-66 URM damage, west elevation .......................................... 4-51 

Figure 4-67 Photo of Building J4 and detail of damage after the 

2000 Yountville earthquake ............................................. 4-52 

Figure 4-68 Exterior view of building ................................................. 4-53 

Figure 4-69 URM parapet bracing ....................................................... 4-53 

Figure 4-70 Loosened wall anchors on south wall, looking down ...... 4-54 

Figure 4-71 Connection failure at compressor .................................... 4-55 

Figure 4-72 Exterior wall on day of earthquake.................................. 4-56 

Figure 4-73 Diagonal cracks in stone wall .......................................... 4-56 

Figure 4-74 Exterior face of parapet wall ............................................ 4-57 

Figure 4-75 Close up of dislodged stone on inside face of parapet..... 4-57 

Figure 4-76 URM parapet bracing, loss of stonework ........................ 4-58 

Figure 4-77 View from the southwest showing front façade and 

fencing ............................................................................. 4-59 

Figure 4-78 Loose stone cladding over window at front façade .......... 4-60 

Figure 4-79 Diagonal cracking at inside face of second story pier at
 

front façade ...................................................................... 4-61 

Figure 4-80 Rear façade elevation....................................................... 4-61 

Figure 4-81 Exterior view of building ................................................. 4-62 

Figure 4-82 Minor cracking in URM wall, north elevation ................. 4-63 

Figure 4-83 Southeast corner, damage to URM wall due to interaction 

with steel stair .................................................................. 4-63 

Figure 4-84 Damage to glazing, west elevation .................................. 4-64 

Figure 4-85 Exterior view of building................................................. 4-65 

Figure 4-86 Damage to stonework above main entrance .................... 4-66 

Figure 4-87 Failed wall anchor, north elevation .................................. 4-66 

Figure 4-88 Failure of air handler unit anchor, screws pulled out of
 

sleeper .............................................................................. 4-67 

Figure 4-89 Building elevation from Main Street ............................... 4-68 

Figure 4-90 Unanchored tank shifted approximately 8 inches ............ 4-69 

FEMA P-154 List of Figures xv 
Figure 4-91 Photo of strong-motion recording instrument ..................4-69 

Figure 4-92 East elevation ...................................................................4-70 

Figure 5-1 Map of hospitals investigated following the South Napa 

earthquake ..........................................................................5-2 

Figure 5-2 Queen of the Valley Hospital site plan indicating building 

numbers ..............................................................................5-4 

Figure 5-3 Damaged concrete beam at the third floor of 

BLD-01650 ........................................................................5-6 

Figure 5-4 Cracked concrete wall piers in BLD-01650 .......................5-6 

Figure 5-5 Cracked precast concrete panel in BLD-01653 ..................5-7 

Figure 5-6 Cracked gypsum board wall in BLD-05309.......................5-7 

Figure 5-7 Third floor ceiling damage in BLD-05323 corridor link ...5-8 

Figure 5-8 Third floor ceiling damage in BLD-01656 ........................5-8 

Figure 5-9 Evidence of water leak in corridor of BLD-01650 .............5-8 

Figure 5-10 South Nursing Wing storefront glazing damage leading to 

entrance posted RESTRICTED USE at BLD-01656 .........5-9 

Figure 5-11 South Nursing Wing storefront glazing damage leading to 

RESTRICTED USE posting at BLD-01656 ......................5-9 

Figure 5-12 Movement at seismic joint between BLD-01652 and 

BLD-01650 Main Hospital...............................................5-10 

Figure 5-13 Damage to seismic joint flashing between BLD-01654 

and BLD-01655................................................................5-10 

Figure 5-14 Damage to seismic joint cover at second floor of 

BLD-01659 ......................................................................5-10 

Figure 5-15 Telephone rack on cantilevered supporting frame at roof 

of BLD-01650 severely out of plumb ..............................5-11 

Figure 5-16 Electrical panel on cantilevered supports damaged at roof
 

of BLD-01656 ..................................................................5-11 

Figure 5-17 Damaged light fixture in BLD-05309 ..............................5-12 

Figure 5-18 Contents damage in BLD-01650 ......................................5-12 

Figure 5-19 Contents damage in BLD-01650 ......................................5-13 

xvi List of Figures FEMA P-1024 
 

 

 

Figure 5-20 Unanchored vending machine in BLD-01656 shifted 

over 12 inches .................................................................. 5-13 

Figure 5-21 Sutter Solano Medical Center site plan ............................ 5-14 

Figure 5-22 The Kaiser Foundation Hospital – Rehabilitation Center 

Vallejo site plan ............................................................... 5-15 

Figure 5-23 The Sonoma Valley Hospital site plan ............................. 5-17 

Figure 5-24 St. Helena Hospital site plan ............................................ 5-18 

Figure 5-25 Front entrance .................................................................. 5-19 

Figure 5-26 Cracking along the separation joint between BLD-01666 

and BLD-01667 at the roof penthouse ............................. 5-20 

Figure 5-27 Cracking of the 1/2 inch to 1 inch thick topping slab over 

original roof slab inside the roof penthouse along the 

separation joint................................................................. 5-20 

Figure 5-28 Evidence of movement along the separation joint at the 

fourth floor between BLD-01668 and BLD-01666 ......... 5-21 

Figure 5-29 Map of skilled nursing facilities ...................................... 5-21 

Figure 6-1 Map showing the locations of all schools in the Napa Valley
 

Unified School District ...................................................... 6-2 

Figure 6-2 Damaged light fixtures in classroom at Pueblo Vista 

Elementary School............................................................. 6-4 

Figure 6-3 Aircraft cable slipped out of the cable gripping support
 

fixture at Pueblo Vista Elementary School ........................ 6-4 

Figure 6-4 Damaged light fixtures in Irene M. Snow Elementary
 

School ................................................................................ 6-5 

Figure 6-5 Damaged light fixtures in Napa Valley Language 

Academy ............................................................................ 6-5 

Figure 6-6 Failed connection at light fixture in Napa Valley
 

Language Academy ........................................................... 6-6 

Figure 6-7 Undamaged connection to light fixture in Napa Valley
 

Language Academy ........................................................... 6-6 

Figure 6-8 Bracing wire pulled out of wall at Harvest Middle 

School ................................................................................ 6-7 

Figure 6-9 Open lens covers at Shearer Elementary School ............... 6-7 

FEMA P-154 List of Figures xvii 
 

 

Figure 6-10 Dislodged fluorescent bulbs at Shearer Elementary 

School .................................................................................6-8 

Figure 6-11 Overturned cabinets in Irene M. Snow Elementary
 

School .................................................................................6-9 

Figure 6-12 Overturned bookcase in Stone Bridge School..................6-10 

Figure 6-13 Overturned bookcase blocking exit in Stone Bridge 

School ...............................................................................6-10 

Figure 6-14 Overturned bookcase at doorway in Harvest Middle 

School ...............................................................................6-11 

Figure 6-15 Overturned file cabinet in Harvest Middle School...........6-11 

Figure 6-16 Dislodged books in Napa High School ............................6-12 

Figure 6-17 Contents dislodged from counters in Stone Bridge School 

wood shop ........................................................................6-12 

Figure 6-18 Dislodged tiles and bent edge angle in a Silverado
 

Middle School classroom .................................................6-13 

Figure 6-19 Damage to suspended acoustic tile ceiling in Napa 

Junction Elementary School .............................................6-14 

Figure 6-20 Gypsum wallboard cracking in New Technology High
 

School ...............................................................................6-14 

Figure 6-21 Dislodged adhered tile in Harvest Middle School............6-15 

Figure 6-22 Broken window at Harvest Middle School ......................6-15 

Figure 6-23 Failed earthquake restraining strap on water heater .........6-16 

Figure 6-24 Failed earthquake restraining strap at Shearer Elementary
 

School ...............................................................................6-17 

Figure 6-25 Shifted rooftop condensate unit at Redwood Middle 

School ...............................................................................6-17 

Figure 6-26 Shifted rooftop make-up air unit at Napa High School....6-18 

Figure 6-27 Broken condensate connection at air conditioning unit, 

Redwood Middle School..................................................6-18 

Figure 6-28 Toppled disconnect for rooftop air handler at Napa High 

School ...............................................................................6-19 

Figure 6-29 Shifted rooftop pipe supports at Silverado Middle 

School ...............................................................................6-19 

xviii List of Figures FEMA P-1024 
 

 

Figure 6-30 Exposed wires at failed conduit fitting, Harvest Middle 

School .............................................................................. 6-20 

Figure 6-31 Shifted conduit at sleeper support, Harvest Middle 

School .............................................................................. 6-20 

Figure 6-32 Shifted conduit at Napa Valley Language Academy ....... 6-21 

Figure 6-33 Broken low voltage conduit coupling at Redwood Middle 

School .............................................................................. 6-21 

Figure 6-34 Broken PVC conduit at Redwood Middle School ........... 6-22 

Figure 6-35 Cracking at slab joint in walkway at Harvest Middle 

School .............................................................................. 6-22 

Figure 6-36 Cracks in asphalt parking lot at Stone Bridge School...... 6-23 

Figure 6-37 Damaged door at Browns Valley Elementary School ..... 6-24 

Figure 6-38 Unrestrained bookshelf overturned in office ................... 6-25 

Figure 6-39 Toppled altar and statuary ................................................ 6-25 

Figure 6-40 Toppled landscape statuary.............................................. 6-26 

Figure 6-41 Interior view of auditorium walls .................................... 6-27 

Figure 6-42 Minor wall cracking......................................................... 6-27 

Figure 7-1 Location of Browns Valley neighborhood relative to 

downtown Napa ................................................................. 7-2 

Figure 7-2 Surface feature of fault rupture observed on street ............ 7-3 

Figure 7-3 Crack running through the street and up the driveway ...... 7-3 

Figure 7-4 Crack continuing around the base of structure................... 7-4 

Figure 7-5 Brick chimney collapse on to the roof. .............................. 7-4 

Figure 7-6 Cracks in the pavement of the backyard and damage to
 

stucco wall ......................................................................... 7-5 

Figure 7-7 Ceiling crack ...................................................................... 7-6 

Figure 7-8 Damage caused due to differential movement of floor slabs 

in garage and driveway pavement ...................................... 7-6 

Figure 7-9 Surface rupture observed on street..................................... 7-7 

Figure 7-10 Photo showing demolished perimeter foundation and 

cracks in pavement ............................................................. 7-8 

FEMA P-154 List of Figures xix 
 

Figure 7-11 Structure raised for foundation repair ................................7-8 

Figure 7-12 Home with collapsed cripple wall ......................................7-9 

Figure 7-13 Building fell into adjoining property ..................................7-9 

Figure 7-14 Failure of porch due to cripple wall collapse ...................7-10 

Figure 7-15 Temporary lateral bracing at cripple wall ........................7-10 

Figure 7-16 House shifted lateral at damaged cripple wall ..................7-11 

Figure 7-17 Collapsed cripple wall......................................................7-11 

Figure 7-18 Failure of porch due to cripple wall collapse ...................7-12 

Figure 7-19 Undamaged residence on the right was posted UNSAFE 

due to risk posed by damaged residence on the left.........7-12 

Figure 7-20 Elevated duplex homes.....................................................7-13 

Figure 7-21 Braced wood cripple walls on the first story of elevated 

duplex homes ...................................................................7-14 

Figure 7-22 Dislodged unreinforced masonry chimney ......................7-15 

Figure 7-23 Photo of damaged chimney..............................................7-16 

Figure 7-24 Photo of chimney laying on front yard of home ..............7-16 

Figure 7-25 Photo of interior chimney collapse ...................................7-17 

Figure 8-1 Typical older (single-wide) home with add-on porch and 

carport ................................................................................8-2 

Figure 8-2 Typical newer (double-wide) home clad in wood panel 

siding with a matching siding skirt ....................................8-2 

Figure 8-3 Typical dry-stacked masonry gravity piers, with 

interspersed wood blocks ...................................................8-6 

Figure 8-4 Steel gravity piers interspersed with masonry piers during 

home reinstallation .............................................................8-6 

Figure 8-5 ETS strap connected to a home chassis beam, cut to allow 

home to be relocated ..........................................................8-7 

Figure 8-6 ETS ground anchor ............................................................8-7 

Figure 8-7 Steel pier system with anchor rods to the ground ..............8-8 

Figure 8-8 ETS removed from homes during reinstallation ................8-9 

xx List of Figures FEMA P-1024 
 

 

 

Figure 8-9 New “cantilevered” pier, anchored to supporting 

plywood panels .................................................................. 8-9 

Figure 8-10 “Cantilevered” steel pier on home requiring 

reinstallation..................................................................... 8-10 

Figure 8-11 “Diagonally braced” ERBS on homes requiring 

reinstallation..................................................................... 8-11 

Figure 8-12 Damaged skirt on older home .......................................... 8-12 

Figure 8-13 Home dropped from masonry gravity pier supports ........ 8-12 

Figure 8-14 Close-up of toppled masonry gravity pier ....................... 8-13 

Figure 8-15 This door was blocked when the home dropped off of the 

gravity supports and had to be broken open by fire 

fighters ............................................................................. 8-13 

Figure 8-16 Add-on porch structure severely damaged by the 

earthquake........................................................................ 8-14 

Figure 8-17 Map of six MHPs north of Napa Fire Station No. 3 ........ 8-16 

Figure 8-18 Oaktree Vineyard MHP typical home configuration ....... 8-18 

Figure 8-19 Damage to brick masonry skirt wall ................................ 8-18 

Figure 8-20 “Cantilevered” pier system that slid, adjacent to a masonry
 

pier that has rolled over ................................................... 8-19 

Figure 8-21 Gap between front porch and home on home with ERBS 

that slid a significant distance .......................................... 8-20 

Figure 8-22 Extent of home sliding..................................................... 8-20 

Figure 8-23 Manufactured home that slid and fell onto its utility 

hookup ............................................................................. 8-22 

Figure 8-24 Napa Valley MHP home displaced significantly to the
 

west .................................................................................. 8-23 

Figure 8-25 Napa Valley MHP home displaced significantly to the
 

east ................................................................................... 8-23 

Figure 8-26 Entry stairs at Napa Valley MHP home that displaced 

significantly to the east .................................................... 8-24 

Figure 9-1 Collapsed barrel stacks ...................................................... 9-3 

Figure 9-2 Anchorage failure allowed tank to shift on pedestal .......... 9-7 

FEMA P-154 List of Figures xxi 
 

Figure 9-3 Historic timber-framed winery building with large 

residual drift at the ground floor .......................................9-8 

Figure 10-1 Broken glass at open storefront on an unreinforced 

Figure 10-2 Typical condition showing temporary plywood barricades 

and plastic over openings where storefront glazing was 

Figure 10-5 Metal stud and stucco framed cladding dislodged from
 

Figure 10-6 Dislodged precast panel in telephone operations facility:
 

Figure 9-4 Steel columns damaged by impact of barrels .....................9-9 

Figure 9-5 Failure of glulam beam to wall connection resulted in roof 

collapse.............................................................................9-10 

masonry building ..............................................................10-3 

damaged ...........................................................................10-4 

Figure 10-3 Broken glass in Napa County air traffic control tower ....10-4 

Figure 10-4 Temporary air traffic control tower ..................................10-5 

concrete wall ....................................................................10-6 

(a) missing panel with orange brackets remaining in place; 

(b) temporary covering after the earthquake ....................10-7 

Figure 10-7 Gypsum wallboard was removed from partition walls 

where water damage from a broken sprinkler head 

Figure 10-10 Cracked and spalled plaster on lath and plaster 

Figure 10-12 Cracking and spalling of a plaster ceiling in an older 

Figure 10-13 Cracking and spalling of a plaster ceiling in an older 

Figure 10-15 Failure of a splice of acoustical tile ceiling grid in a twoFigure 10-16 Failure of “fixed” end support of the acoustical tile 

ceiling grid in a two-story retail store in downtown 

occurred............................................................................10-8 

Figure 10-8 Typical damage to gypsum wallboard .............................10-8 

Figure 10-9 Damage to gypsum wallboard at corner ...........................10-9 

wall...................................................................................10-9 

Figure 10-11 Cracking of gypsum wallboard ceiling ..........................10-10 

masonry building in downtown Napa ............................10-10 

reinforced concrete building in downtown Napa ...........10-11 

Figure 10-14 Acoustic ceiling where tiles fell in an office building ....10-12 

story retail store in downtown Napa ..............................10-12 

Napa ...............................................................................10-13 

xxii List of Figures FEMA P-1024 
Figure 10-17 Failure of “free” end support of the acoustical tile ceiling 

grid in a two-story retail store in downtown Napa ......... 10-13 

Figure 10-18 “S” hook opened during earthquake and caused 

fixtures to drop ............................................................... 10-14 

Figure 10-19 Pendant fixture support detail ........................................ 10-15 

Figure 10-20 Sprinkler head interaction with adjacent components 

resulted in extensive flooding ........................................ 10-16 

Figure 10-21 Repaired condition of a failed pipe at threaded 

connection that resulted in flooding of the first floor 

restaurant........................................................................ 10-16 

Figure 10-22 Sprinkler piping in close proximity to HVAC 

components. ................................................................... 10-17 

Figure 10-23 Sprinkler armover in close proximity to HVAC 

components .................................................................... 10-17 

Figure 10-24 Sprinkler installation in parking garage ......................... 10-18 

Figure 10-25 Failures of powder driven fasteners............................... 10-19 

Figure 10-26 Contents dislodged from grocery store shelves ............. 10-20 

Figure 10-27 Loss of products from shelves ....................................... 10-21 

Figure 10-28 Wine storage rack in retail store that did not lose a single 

bottle of wine in the earthquake. .................................... 10-21 

Figure 10-29 Unanchored fixtures overturned in aisle ........................ 10-22 

Figure 10-30 Overturned unanchored bookshelf................................. 10-22 

Figure 10-31 Solar arrays at medical center in Vallejo ....................... 10-23 

Figure 10-32 Recordings from CGS Station 68294, located 

approximately 300 feet from medical center parking 

garage............................................................................. 10-24 

Figure 10-33 Ground-mounted solar canopy over parking lot. ........... 10-25 

Figure 10-34 Parking garage with solar canopy structure on roof ...... 10-26 

Figure 10-35 Solar canopy structure on roof of parking garage .......... 10-26 

Figure 10-36 Elongated steel X-bracing rods...................................... 10-27 

Figure 10-37 Possible plastic strain of steel rod X-bracing adjacent to 

gusset plate..................................................................... 10-27 

FEMA P-154 List of Figures xxiii 
Figure 10-38	 Clip angle is anchored to the concrete wall but not 

attached to column baseplate..........................................10-28 

Figure 10-39	 Low-profile unattached (ballast-only) solar array on 

roof of medical office building .......................................10-29 

Figure 10-40	 Roof-mounted solar canopy on top of parking garage 

structure..........................................................................10-29 

Figure 10-41	 Locations of rooftop solar arrays inspected by
 

manufacturer’s engineers following the earthquake ......10-30 

Figure 10-42	 Solar array on the roof of an office and warehouse 

building two miles east of earthquake epicenter ............10-31 

Figure 10-43 Mechanical attachment of solar array on the roof of an 

office/warehouse building two miles east of earthquake
 

epicenter .........................................................................10-31 

Figure 11-1 A building with multiple placards.................................... 11-7 

Figure 11-2 A RESTRICTED USE tag with restrictions noted as 

“Public may enter. Stay clear of taped off areas and 

construction.” ...................................................................11-8 

Figure 11-3 A RESTRICTED USE placard with no information on 

the restrictions. .................................................................11-9 

Figure 11-4 An INSPECTED placard on a building with another exit 

that is still restricted .........................................................11-9 

Figure 11-5 A RESTRICTED USE placard with exemptions 

permitting access while the restaurant is open ...............11-10 

Figure 11-6 An UNSAFE placard with an adjacent inconsistent 

placard by the owner ......................................................11-10 

Figure 12-1 A building with an UNSAFE placard where the fence 

setback was much less than a 1.5H:1V setback 

distance.............................................................................12-3 

Figure 12-2 Church with damaged gable façade where the fence 

setback was less than a 1.5H:1V set back distance ..........12-3 

Figure 12-3 Partial street closure .........................................................12-4 

Figure 12-4	 Scaffolding used as a barricade on damaged URM 

building ............................................................................12-5 

Figure 12-5 Scaffolding used as a barricade damaged in a 

windstorm.........................................................................12-5 

Figure 12-6 Replacement scaffolding following the windstorm ..........12-6 

xxiv List of Figures FEMA P-1024 
Figure 12-7 Protective barrier constructed over the rooftops of 

buildings to protect from falling brick ............................. 12-7 

Figure A-1 Postearthquake Building Performance Assessment 

Form (page 1 of 6) ............................................................ A-5 

Figure A-1 Postearthquake Building Performance Assessment 

Form (page 2 of 6) ............................................................ A-6 

Figure A-1 Postearthquake Building Performance Assessment 

Form (page 3 of 6) ............................................................ A-7 

Figure A-1 Postearthquake Building Performance Assessment 

Form (page 4 of 6) ............................................................ A-8 

Figure A-1 Postearthquake Building Performance Assessment 

Form (page 5 of 6) ............................................................ A-9 

Figure A-1 Postearthquake Building Performance Assessment 

Form (page 6 of 6) .......................................................... A-10 

Figure A-2 Surveyor instructions (page 1 of 4)................................. A-11 

Figure A-2 Surveyor instructions (page 2 of 4)................................. A-12 

Figure A-2 Surveyor instructions (page 3 of 4)................................. A-13 

Figure A-2 Surveyor instructions (page 4 of 4)................................. A-14 

FEMA P-154 List of Figures xxv 

 

List of Tables
 

Table 2-1 Strong Motion Recording Sites within the City of Napa ... 2-7 

Table 4-1 Summary of Case Studies .................................................. 4-1 

Table 5-1 List of Hospitals Investigated by OSHPD ......................... 5-2 

Table 5-2 Structural System Descriptions .......................................... 5-3 

Table 5-3 Queen of the Valley Hospital – Napa Building 

Descriptions and Posting ................................................... 5-5 

Table 5-4 Sutter Solano Medical Center Building Descriptions and 

Posting ............................................................................. 5-15 

Table 5-5 Kaiser Foundation Hospital Building Descriptions and 

Posting ............................................................................. 5-16 

Table 5-6 Sonoma Valley Hospital Building Descriptions and 

Posting ............................................................................. 5-17 

Table 5-7 St. Helena Hospital Building Descriptions and 

Posting ............................................................................. 5-19 

Table 5-8 List of Skilled Nursing Facilities Investigated by
 

OSHPD ............................................................................ 5-22 

Table 5-9 Skilled Nursing Facilities Building Descriptions and 

Posting ............................................................................. 5-22 

Table 8-1 Summary of HCD Field Inspection Data Showing Homes 

Requiring Reinstallation .................................................. 8-17 

Table 8-2 Measured or Estimated Movement of Homes with 

“Diagonally Braced” ERBS ............................................. 8-21 

Table10-1 Summary of Low-Profile Attached Rooftop Solar 

Arrays ............................................................................ 10-32 

Table A-1 General Damage Classifications ....................................... A-2 

Table A-2 ATC-13 Damage State Classifications ............................. A-2 

FEMA P-1024 List of Tables xxvii 

 

 

 

 

 

 

 

 

 

 

 


 


 

Chapter 1
 

Introduction
 

The magnitude-6 South Napa earthquake occurred on August 24, 2014 with 

an epicenter located 8 km (5 miles) south southwest of the City of Napa. The 

cities of Napa and Vallejo, as well as the surrounding areas, were 

significantly impacted by the event. The earthquake struck at 3:20 in the 

morning, which was the primary reason for only one fatality and the low 

number of serious injuries. Had the earthquake struck 12 hours earlier, 

during a street festival in downtown Napa, the number of fatalities could 

have easily been in the hundreds due to falling debris from masonry 

buildings and nonstructural components. 

The earthquake was recorded by eight strong-motion recording instruments 

at which horizontal ground motions were significant (exceeded 0.1g), and 

three of those instruments were located within the City of Napa. Availability 

of recorded ground motions and documentation of the impact of the 

earthquake provides an excellent opportunity to calibrate and evaluate 

existing earthquake hazard reduction methodologies. This is also an 

opportunity to expand existing knowledge and databases on the performance 

of buildings and other structures, including seismically retrofitted 

unreinforced masonry (URM) buildings. 

1.1 Project Goal 

The goal of the project was to assess and document the performance of a 

population of buildings impacted by the earthquake and develop a series of 

recommendations to further improve mitigation. The building stock in Napa 

consisted of mostly older buildings, many of which had previously been 

seismically retrofitted. This project focused on the performance of seismic 

retrofitting, particularly for URM buildings, and the performance of 

nonstructural components, since they were responsible for the vast majority 

of the damage and injuries. The performance of buildings designed in 

accordance with recent building codes was also investigated. It is envisioned 

that data from this project will eventually be used to assist in the validation 

of two new assessment methodologies documented in recently released 

FEMA documents, FEMA P-58, Seismic Performance Assessment of 

Buildings (FEMA, 2012b) and the third edition of FEMA P-154, Rapid 

FEMA P-1024 1: Introduction 1-1 
 

 

 

 

 

 

 

 

 

 

 

 

Visual Screening of Buildings for Potential Seismic Hazards: A Handbook, 

(FEMA, 2015). 

1.2 Investigation Process 

It is common to focus postearthquake reconnaissance on observations of 

damage. A major focus of this project was performance, both bad and good. 

In order to make it possible to correlate the relationships between ground 

shaking severity and the performance of building, this project collected 

information on all buildings located in the vicinity of a strong-motion 

recording instrument with the purpose of relating damage observations back 

to an input ground motion. 

Postearthquake information was also collected and documented by the 

following organizations: The Earthquake Engineering Research Institute 

(EERI), the Geotechnical Extreme Events Reconnaissance (GEER) 

Association, the Pacific Earthquake Engineering Research (PEER) Center, 

the Post-Disaster Performance Evaluation Program (PDPOC) of the 

Structural Engineers Association of California (SEAOC), and the Technical 

Committee on Lifeline Earthquake Engineering (TCLEE) of the American 

Society of Civil Engineers (ASCE). 

1.2.1 Survey Process 

Most of the buildings discussed in this report were evaluated using the 

methodology developed in the ATC-38 report, Database on the Performance 

of Structures near Strong-Motion Recordings: 1994 Northridge, California, 

Earthquake, (ATC, 2000). This methodology is also the basis for the forms 

used by the Post-Disaster Performance Evaluation Program (PDPOC) of the 

Structural Engineers Association of California (SEAOC) in their data 

collection efforts. 

The ATC-38 methodology was developed following the 1994 Northridge 

earthquake to systematically collect and analyze data from buildings located 

in the vicinity of strong-motion recording instruments. The methodology 

calls for designating one or more specific strong-motion instrument sites and 

investigating every building within a 1,000 foot radius of that instrument 

using a six-page postearthquake building performance assessment form. The 

forms were created to collect data including the structure size, age, location, 

structural framing system and other important structural characteristics, 

nonstructural systems and performance, fatalities and injuries, and estimated 

time to restore the facility to pre-earthquake usability. Information on 

postearthquake damage evaluations and placarding is also collected. 

1-2 1: Introduction FEMA P-1024 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To collect data on buildings impacted by the 2014 South Napa earthquake, 

the forms developed and used for the Northridge earthquake were adopted 

for use with minor modifications to account for new knowledge and the 

specific issues related to this event. Modifications included the addition of 

the “minor” damage state, collection of general classification information for 

nonstructural damage, expanding opportunities for sketching building plans 

and elevations, describing irregularities in terms consistent with FEMA 

P-154, and expanding the scope of nonstructural systems and components 

examined. More information on the modification and a sample data 

collection form used in this project are provided in Appendix A. 

1.2.2 Scope of Investigation 

This investigation primarily focused on collection of data for all buildings 

within a 1,000 foot radius around the strong-motion recording instrument at 

Station N016 located on Main Street in Napa operated by the Northern 

California Seismic Network (NCSN) of the U.S. Geological Survey (USGS). 

This station was identified as the top priority for systematic data collection 

for the following reasons: (1) the level of ground shaking in the area was 

sufficient to cause damage to some buildings; (2) the area contains a large 

number of commercial and civic buildings, both historic and modern; and (3) 

there are several retrofitted unreinforced masonry buildings in the selected 

area. The source-to-site distance for Station N016 was 3.9 km, the peak 

ground acceleration (PGA) was 0.61g (north-south), 0.32g (east-west), and 

0.24g (vertical) (GEER, 2015). It is recognized that although the location of 

the instrument adjacent to the Napa River may have contributed to the PGA 

values being higher than the other two instruments in Napa, the soils in Napa 

Valley are consistently alluvial in nature, resulting in fairly consistent ground 

motions within the study area. 

The investigation was limited to a single site largely as a consequence of 

limited resources. However, reconnaissance work included collection of data 

for select buildings outside the 1,000 foot radius in order to more 

comprehensively examine the nature and scope of building performance in 

the earthquake. Specifically, the study investigated the performance of 

residential construction, manufactured housing, modern commercial 

buildings, healthcare facilities, and schools. In addition, given their 

economic importance to the region, wineries were also examined. 

This investigation was limited to buildings and did not include infrastructure. 

There were many lifelines issues, including loss of power, but loss of water 

supply had the largest impact on building performance. The earthquake 

ruptured over 120 water mains, and at least one of these breaks impacted 

FEMA P-1024 1: Introduction 1-3 
 

 

 

 

 

 

 

 

 

 

 

 

firefighting at one mobile home park, where a fire in one unit resulted in the 

loss of five units due to a delay in providing water to the scene. For 

information on the performance of lifelines in the South Napa earthquake, 

refer to PEER Preliminary Notes and Observations on the August 24, 2014 

South Napa Earthquake (PEER, 2014) and South Napa M 6.0 Earthquake of 

August 24, 2014 report (ASCE, 2014). 

1.2.3 Site Investigations 

Site investigations within the 1,000 foot radius were conducted on September 

5, 8 and 9, 2014, approximately two weeks after the earthquake. Each 

investigation was conducted with a team of not fewer than two engineers, 

one of whom was a registered Structural Engineer in the State of California. 

On average, each team spent between approximately 1 and 1.5 hours 

investigating and documenting each building, using modified ATC-38 forms. 

The level of detail for each building investigation varied based on a number 

of factors including access to the interior of the building (buildings posted 

UNSAFE generally could not be entered), security (entry was not permitted 

or was limited in some buildings), and the availability and willingness of a 

building representative to facilitate and supplement observations. For a 

subset of buildings, drawings were made available for viewing by either the 

building owner or the City of Napa Building Division. 

The database containing the information collected will be published by the 

Applied Technology Council. 

Selected buildings outside the 1,000 radius were also studied. In most cases, 

building data were collected using ATC-38 forms. In some cases, such as 

healthcare facilities, schools, residential construction, manufactured housing, 

and wineries, information was collected throughout the affected area, during 

a period of several weeks after the earthquake, and without completing the 

ATC-38 forms. As with others, investigations varied in their level of detail 

and included a combination of observations, conversations with building 

owners and tenants, and review of drawings. 

Photos in the report not individually acknowledged as originating from 

outside sources were provided by the Principal and Contributing Authors, 

Project Working Group members, and participating ATC staff. 

1.3 Report Organization 

This report describes the performance of structural and nonstructural systems 

in the 2014 South Napa earthquake. Chapter 2 describes the ground motion 

and regional seismicity. Chapter 3 provides a summary of the building 

1-4 1: Introduction FEMA P-1024 
 

 

 

 

 

 

 

survey data based on the information collected using the ATC-38 forms on 

the 68 buildings within the 1,000 foot radius. Chapter 4 provides a summary 

of the performance of selected buildings within and outside of the 1,000 ft 

radius and recommendations. Chapter 5 provides a detailed summary of the 

performance of healthcare facilities. Chapter 6 provides an overview of the 

performance of school facilities within the cities of Napa and Vallejo. 

Chapter 7 provides an overview of the performance of residential 

construction, including observations of surface rupture and afterslip. Chapter 

8 provides a background on seismic requirements for manufactured housing 

and the performance of units in eleven mobile home parks near the epicenter. 

Chapter 9 provides an overview of the performance of wine industry 

facilities affected. Chapter 10 provides an overview of the performance of 

nonstructural elements including glazing, cladding, interior partitions, 

mechanical, electrical, and plumbing equipment, piping systems, contents, 

and solar arrays. Chapter 11 summarizes the response for postearthquake 

safety evaluation of buildings and observed placards. Chapter 12 

summarizes the available resources and observed barricading of unsafe areas. 

Chapter 13 summarizes the recommendations. 

Appendices provide additional information on the subject. Appendix A 

presents the survey forms and instructions used and Appendix B provides 

two Recovery Advisories developed in response to the damage sustained in 

the 2014 South Napa earthquake: the first is on cripple wall foundations and 

a summary is provided here because it was under development when this 

report was published; the second is on masonry chimneys and is provided in 

its entirety. 

FEMA P-1024 1: Introduction 1-5 

 

 

Chapter 2 

Seismicity and Ground Motion 

Data 

This chapter presents information regarding seismicity and ground motion in 

the 2014 South Napa earthquake. Much of the information in this chapter 

was taken from two publications: (1) National Science Foundation-supported 

GEER Report 037, Geotechnical Engineering Reconnaissance of the August 

24, 2014 M6 South Napa Earthquake, (GEER, 2015); and (2) Key Recovery 

Factors for the August 24, 2014, South Napa Earthquake, (USGS, 2014). 

The reader is referred to both of those reports for a more detailed description. 

2.1 West Napa Fault and Surrounding Seismicity 

The region impacted by the South Napa earthquake is encompassed by the 

Bay Area San Andreas Fault System, which forms the boundary between the 

Pacific and North American tectonic plates. It is depicted by the U.S. 

Geological Survey to have a high probability of strong shaking in the future, 

as shown in Figure 2-1. Specifically, the area has a 63% probability of 

experiencing a magnitude 6.7 or greater earthquake in the next 30 years. 

These data are further broken down by each specific fault, and the Rogers 

Creek/Hayward fault system has a 31% chance of causing such an 

earthquake and the Green Valley/Concord fault system has a 3% chance of 

causing such an earthquake. The USGS map does not list the West Napa 

fault as contributing to this probability. 

The August 24, 2014 South Napa earthquake occurred on the West Napa 

fault, which lies within a 70 km (44 miles) wide set of faults that make up the 

San Andreas fault system. The West Napa fault lies between the larger 

Rogers Creek and Green Valley faults and begins at American Canyon at the 

south end of Napa Valley where it meets San Pablo Bay and extends to the 

north-northwest along the west side of Napa Valley (Figure 2-2). 

Napa Valley is a typical California Coastal Range valley situated between 

low lying mountain ranges and filled with 160 meters of older Pleistocene 

alluvial deposits overlaid by 10 meters of more recent Holocene alluvial 

deposits, and is equivalent to Site Class D soils. 

FEMA P-1024 2: Seismicity and Ground Motion Data 2-1 
Figure 2-1	 2008 earthquake probabilities from the USGS website. Available at 

http://earthquake.usgs.gov/regional/nca/ucerf/, last accessed March 5, 2015. 

The most recent earthquake prior to 2014 was the magnitude-5.0 Yountville 

earthquake, which took place roughly 15km northwest of Napa on an 

unnamed fault west of the West Napa fault in September 2000. 

2-2 2: Seismicity and Ground Motion Data FEMA P-1024 
 

Figure 2-2 Geologic map showing fault lines (USGS, 2008). 

2.2 The South Napa Earthquake 

With a magnitude of 6.0, the South Napa earthquake is the largest earthquake 

to strike the San Francisco Bay Area since 1989, when the region was shaken 

FEMA P-1024 2: Seismicity and Ground Motion Data 2-3 
 

by the magnitude-6.9 Loma Prieta earthquake. It was also the first 

earthquake to produce significant surface rupture in Northern California 

since the 1906 San Andreas event. 

The epicenter was located approximately 8 km south-southwest of Napa. 

The earthquake was recorded by a network of seismographs in the Bay Area, 

which located the hypocenter at the south end of Napa Valley at a depth of 

10 km. The primary direction of the earthquake ground motion was to the 

north, meaning that downtown Napa experienced the strongest ground 

motion. 

The West Napa fault is actually a system of several active fault strands, all 

running north-northwest along the west side of Napa Valley. The earthquake 

resulted in significant fault rupturing that extended from Cuttings Wharf 

south of Napa roughly 14 km to the north through Browns Valley and ending 

at Alston Park in the northwest corner of Napa. Faulting also extended 1 to 2 

km southeast in American Canyon (Figure 2-3). 

A ShakeMap was developed immediately after the earthquake utilizing 

ground motion station information (Figure 2-4). 

The ShakeMap indicates that the entire Napa Valley sustained shaking of 

Modified Mercalli Intensity (MMI) VI to VII (strong to very strong), with the 

southern portion of the Valley and the City of Napa shaking at MMI VII to 

VIII (very strong to severe) intensity. The maximum intensity reading was 

MMI IX (violent) at Napa Fire Station No. 3. 

Three strong motion recording sites are located within the City of Napa with 

their attributes listed in Table 2-1 and the ground motion recordings in 

Figures 2-5 through 2-7. 

The GEER report compared these recorded ground motions to the codebased design spectra. The results are shown in Figures 2-8a through 2-8c. 

This comparison for the sites show that the pseudo-spectral accelerations 

recorded at Napa College and Napa Fire Station No. 3 exceeded the 

Maximum Considered Earthquake (MCE) design spectra at a period around 

1.5 seconds near the fault. This effect, referred to as a “bulge” by some, is 

related to the near-fault velocity pulses discussed in the GEER report and 

how the velocity pulse interacted with the Napa Valley soils. The GEER 

report recommends further investigation to study the damage observations 

related to the recorded ground motions compared to the design spectra. 

2-4 2: Seismicity and Ground Motion Data FEMA P-1024 
 

 

CGS Station 68150 

Napa College 

NCSN Station N016 

Main St. 

USGS Station 1765 

Fire Station No. 3 

Figure 2-3 Surface faulting (yellow lines) produced by the August 24, 2014 South Napa 

earthquake (USGS, 2014). Numbers show maximum measured right-lateral offset at 

selected sites, rounded to the nearest cm; includes both coseismic, as well as 

measured afterslip as of November 17, 2014. Red star shows the location of 

earthquake epicenter, orange circles show the location of three ground-motion 

recording instrument stations. 

FEMA P-1024 2: Seismicity and Ground Motion Data 2-5 

 

Figure 2-4 USGS ShakeMap. Available at http://earthquake.usgs.gov/earthquakes 

/eventpage/nc72282711#impact_shakemap, last accessed March 15, 2015. 

2-6 2: Seismicity and Ground Motion Data FEMA P-1024
 
 

 

Table 2-1 Strong Motion Recording Sites within the City of Napa 

Station Name Station Owner Station ID 

Distance to 

Fault 

Napa College California Geological Survey 

(CGS) 

68150 4.1 km 

Main Street U.S. Geological Survey 

Northern California Seismic 

Network (NCSN) 

N016 3.9 km 

Fire Station No. 3 U.S. Geological Survey 

National Strong Motion 

Project (NSMP) 

1765 2.6 km 

Figure 2-5 Ground Motion recordings from Napa College, CGS 

Station 68150 (from http://strongmotioncenter.org/, last 

accessed January 12, 2015). 

FEMA P-1024 2: Seismicity and Ground Motion Data 2-7 
Figure 2-6 Ground Motion recordings from Main Street, USGS NCSN Station N016 (from 

http://strongmotioncenter.org/, last accessed January 12, 2015). 

The Main Street recording depicted by RotD100 is comparable to or exceeds 

the design basis earthquake (DBE) for building systems using ASCE/SEI 

7-10, Minimum Design of Buildings and Other Structures, (ASCE, 2010) 

with periods of vibration less than 0.7 seconds at this site, assuming Site 

Class D for soils. Note that this ground motion had a strong motion duration 

of only six seconds. 

2-8 2: Seismicity and Ground Motion Data FEMA P-1024 
 

 

 

Figure 2-7 Ground Motion recordings from Fire Station No. 3 USGS 

NSMP 1765 (from http://strongmotioncenter.org/, last 

accessed January 12, 2015). 

2.3 Impact of the South Napa Earthquake 

The City of Napa and the surrounding area constitutes a small but significant 

urban area containing about 77,000 people. This magnitude-6.0 earthquake 

is considered a moderately strong earthquake. In such an earthquake, while 

significant losses due to property damage are expected, the risk of serious 

casualties is believed to be low. The USGS Prompt Assessment of Global 

Earthquakes for Response (PAGER) system estimated that economic losses 

directly attributable to the earthquake damage would likely (63% chance) be 

in the range of $100 million to $10 billion. The PAGER system also 

estimated that there would be a very low likelihood of casualties. While the 

actual estimates for the economic damage are still being determined, the 

actual losses suffered appear to be generally in line with the performance 

expectations. 

FEMA P-1024 2: Seismicity and Ground Motion Data 2-9 
 

(a) (b) 

(c) 

the “bulge” 

Figure 2-8 Comparison of code-based versus resultant pseudo-spectral acceleration (PSA) spectra on Site 

Class D for: (a) Napa Valley College; (b) Main Street; and (c) Fire Station No. 3. Red arrow 

indicates the bulge. From GEER (2015). 

For non-essential structures, which make up the vast majority of the building 

stock, the performance expectations of the building codes for relatively 

modern structures subject to a moderately strong earthquake are repairable or 

no structural damage, and potentially significant but repairable nonstructural 

damage. Buildings designed prior to the introduction of modern seismic 

design requirements can sustain intense structural damage and serious 

2-10 2: Seismicity and Ground Motion Data FEMA P-1024 
 

nonstructural damage. However, except for known hazardous building types, 

such as unreinforced masonry structures that have not been retrofitted, the 

probability of life-threatening damage or collapse is believed to be low. 

This event also served as a test of the earthquake early warning system 

presently being developed by the USGS and the State of California. The 

system generated a warning within five seconds, and provided a ten-second 

warning to the test site at Berkeley prior to the arrival of earthquake ground 

motions. No warning would have been possible within 20 miles of the 

epicenter due to the delay inherent within the system. 

2.4 West Napa Fault Rupture and Afterslip 

The earthquake produced more than 14 km of surface rupture from the Napa 

River at Cuttings Wharf in the south, through Browns Valley to Alston Park, 

within the City of Napa, as shown in Figure 2-3. This amount of fault slip is 

considered unusual for a magnitude-6.0 earthquake. 

After the earthquake, parts of the fault were observed to continue to slip. 

This is a phenomenon called afterslip that has been previously described for 

many earthquakes, including several cases in California. Some examples 

include the 1979 Imperial Valley, 1987 Superstition Hills, and 2004 

Parkfield earthquakes. Afterslip occurs quickly at first, then slows down and 

is thought to eventually stop long after the earthquake. 

Figure 2-9 shows the same location 11 hours after the earthquake on August 

24, 2014 and on January 12, 2015, over four months after the earthquake. 

According to the USGS, 11 hours after the earthquake (Figure 2-9a), the slip 

was observed to be several inches, and 135 days later on January 12, 2015 

(Figure 2-9b), the slip was measured as 15 inches. Even though the creep 

rate several months after the earthquake is barely perceptible, the West Napa 

Fault Zone main strand at this location (and in the south, near Highway 12 

crossing) is still creeping faster than the San Andreas fault’s creeping 

section. However, the creep rate is slowing down and is expected to drop 

down to lower than the San Andreas creep rate in the coming months. 

FEMA P-1024 2: Seismicity and Ground Motion Data 2-11 
	 

	 

	 

(a) (b) 

Figure 2-9 Observation of afterslip at Leaning Oak Drive following the South Napa earthquake: (a) 11 

hours after the earthquake (photo from Alex Morelan); (b) 4 months after the earthquake 

(photo from Kenneth Hudnut, USGS). 

In this event, a portion of the fault system experiencing afterslip runs through 

a residential neighborhood, and is impacting a number of residential 

structures. The afterslip is primarily lateral. 

Figure 2-10 shows all of the fault traces from the West Napa fault and their 

respective afterslip hazard. 

	 The yellow fault trace means a moderate level of afterslip hazard; likely 

to experience less than 15 cm, but more than 5 cm, of afterslip during the 

three years after the earthquake. 

	 The green fault trace means a low level of afterslip hazard; very unlikely 

to experience more than 5 cm of afterslip during the three years after the 

earthquake. 

2-12	 2: Seismicity and Ground Motion Data FEMA P-1024 
 

Figure 2-10	 Afterslip map (USGS, 2014). Note that there are no red lines in 

the figure. 

According to the USGS, for all levels of afterslip hazard, the afterslip amount 

that is measured 90 days after the earthquake may double within 10 years 

after the earthquake, although lower levels of afterslip are also possible. The 

afterslip and associated hazard decreases exponentially with time, posing a 

moderate hazard. The southern part of the main strand of the West Napa 

fault within Browns Valley, from south of Leaning Oak Drive up to Partrick 

Road (A to B on Figure 2-10), is shown in yellow on the map and poses an 

FEMA P-1024 2: Seismicity and Ground Motion Data 2-13 
 

 

	 

	 

	 

	 

	 

	 

	 

ongoing hazard to structures. However, the amount of afterslip is not 

expected to be so great as to pose a severe hazard. 

The northern part of the main strand of the West Napa fault within Browns 

Valley, north of Partrick Road (C to D on Figure 2-10), has experienced no 

significant afterslip; low afterslip hazard exists on this part of the main strand 

of the West Napa fault system. The newly named “eastern strand” of the 

West Napa fault system (E to F on Figure 2-10) has experienced no afterslip; 

low afterslip hazard exists on this part of the eastern strand. Other fault 

strands shown in green on the figure also have low afterslip hazard. 

2.5 Summary 

The South Napa earthquake was a moderately strong event. The damage 

observed following the earthquake is consistent with the performance 

expectations for modern and older structures. The near-fault velocity pulses 

observed in the ground motion records might have had a greater impact on 

the built environment, had the building stock in Napa included taller, more 

flexible structures. The interaction between the velocity pulse and the Napa 

Valley soils is currently not completely understood. 

The impact of afterslip on the Browns Valley residential neighborhood has 

caused considerable damage and is an ongoing issue. The afterslip 

phenomenon and the issues it poses for structures straddling a fault trace 

were not familiar topics to engineers or building owners, especially 

homeowners. In addition, mitigation strategies for this hazard are not well 

known or highly developed. Even if the mitigation approaches were more 

widely known, the homeowners would probably not be able to afford the 

measures since most do not have earthquake insurance, and without 

insurance or some other form of support, most would not be able to afford 

the effective mitigation measure. 

2.6 Recommendations 

The South Napa earthquake highlighted several areas for further study, 

including: 

1.	 Further investigation of the damage observations in relation to recorded 

ground motions. 

2.	 Comparison of response spectra from instrumental records to the design 

spectra for periods of vibration relevant to each building. 

3.	 Comparison of estimates of nonlinear response of buildings to the ground 

motions with actual response, especially considering the influence of the 

velocity pulses. 

2-14	 2: Seismicity and Ground Motion Data FEMA P-1024 
 

 

	 

	 

	 

	 

4. Outreach to the community to increase awareness of the issue of 

afterslip. 

5.	 Development of cost-effective methods to estimate afterslip potential and 

mitigate the effects of afterslip. For areas where afterslip potential is 

high and could impact a conventional foundation, the best way to 

mitigate this hazard would be to replace the existing foundation with a 

reinforced concrete mat or raft slab foundation, which has enough 

reinforcing steel to support itself even if the ground is still slipping 

beneath. Also, measures to protect gas lines and other vulnerable piping 

from damage caused by ground movement should be developed. 

However, given that most foundation repairs have already been made 

and given the cost of replacing a building foundation with a new system, 

this mitigation measure is likely not cost effective at this time for 

existing buildings. It should, however be considered for new 

construction within the moderate hazard areas. 

FEMA P-1024 2: Seismicity and Ground Motion Data 2-15 

 

 

Chapter 3 

Performance of Buildings 

Near Station N016 

A major focus of this project was the collection of data for all buildings 

within a 1,000 foot radius of Station N016 located on Main Street in Napa to 

be able to tie the damage observations back to an input ground motion. All 

surveyed buildings within a 1,000 foot radius around Station N016 are 

included in the data set. The database containing the information collected 

will be published by the Applied Technology Council (ATC). Buildings 

included in this report but outside of the 1,000 foot radius are not included in 

the data presented in this chapter. 

This chapter summarizes the trends in the surveyed parameters judged to be 

most significant, and includes a general discussion of the damage patterns 

and trends that were observed. Buildings of special interest are discussed in 

greater detail in Chapter 4. Surveys were conducted over three days, ranging 

from twelve to sixteen days after the earthquake. Information recorded by 

the surveyors is based on their observation at that time. 

3.1 Survey Area 

A total of 68 buildings were surveyed within 1,000 foot of Station N016 

located in downtown Napa. Figure 3-1 shows the extent of the area 

surveyed. Interior and exterior surveys were conducted for 50 of the 

buildings, with the remaining 18 receiving only exterior surveys. 

3.2 Survey Method 

Data in this chapter are based on the information and observations collected 

and recorded on forms originally developed for ATC-38 report, Database on 

the Performance of Structures near Strong-Motion Recordings: 1994 

Northridge, California, Earthquake, (ATC, 2000) and modified for this 

project. Appendix A provides a summary of modifications implemented to 

account for new knowledge and specific issues related to this event and 

provides the forms and instructions used by investigators on the field. 

FEMA P-1024 3: Performance of Buildings Near Station N016 3-1 
 

 

Figure 3-1 Aerial photo showing the surveyed area. The yellow star indicates the location of 

Station N016. The blue circle indicates the extent of the 1,000 foot radius. (Image 

source: Google Maps). 

The form is six pages long and comprises the following blocks of 

information: 

 Building site information 

 Building construction data 

 Model building type 

 Performance modifiers 

 Sketch of building 

 Nonstructural elements 

3-2 3: Performance of Buildings Near Station N016 FEMA P-1024 
 

 

 General damage 

 Nonstructural damage 

 Injuries or fatalities 

 Functionality 

 Geotechnical failures 

 Additional comments 

 Detailed damage description 

The remainder of this chapter summarizes the data collected where 

information is relevant. 

3.3 Building Site Information 

The information collected on this portion of the form pertains to site 

investigation date, building address, and contact information. In addition, 

existing posting placard information and general damage classification 

information is also collected. 

The placard information is based on the methodology presented in ATC-20-1 

Field Manual: Postearthquake Safety Evaluation of Buildings (ATC, 2005). 

Postearthquake safety evaluations in the City of Napa were managed by the 

Building Division, under the direction of the Chief Building Official. The 

City of Napa presented status reports on the process of evaluations on the 

City website on August 25, 2014 and September 5, 2014 (City of Napa, 

2014a and 2014b). It was first reported that 70 buildings within the city were 

posted as UNSAFE and the number of buildings with RESTRICTED USE 

placards was approaching 200. On September 5, 2014, it was reported that 

125 buildings within the city were posted UNSAFE and over 1,000 buildings 

were posted RESTRICTED USE. At the time of the field investigation on 

September 9, 14 buildings within the 1,000 foot survey area were posted 

UNSAFE and 15 were posted RESTRICTED USE (out of a total 68 

buildings). 

3.4 Building Construction Data 

Dates of construction in the surveyed area vary widely, from 1856 to 2014. 

A significant number of historical buildings were located within the survey 

area, including 10 on the National Register of Historical Places. 

Approximate dates of construction were provided on 81% of the building 

surveys. Based on these data, the median age is 1930. Nineteenth century 

FEMA P-1024 3: Performance of Buildings Near Station N016 3-3 
 

 

 

 


 


 


 


 


 


 


 


 

	 


 


 


 


 


 


 


 


 

	 

buildings make up 16% of the set, and 62% were constructed before 1950. 

Figure 3-2 shows the distribution of buildings by original construction date. Date of Construction 

1850-1859 

1860-1869 

1870-1879 

1880-1889 

1890-1899 

1900-1909 

1910-1919 

1920-1929 

1930-1939 

1940-1949 

1950-1959 

1960-1969 

1970-1979 

1980-1989 

1990-1999 

2000-2009 

2010-2014 

No estimate 

1
 

1
 

2
 

4
 

2
 

7 

5 

5 

6 

2 

1 

10 

3 

2
 

1
 

1
 

3 

12 

0 1 2 3 	 4 5 6 7 8 9 10 11 12 13 

Number of Buildings 

Figure 3-2 Distribution (by count) of buildings by date of original 

construction. 

Buildings ranged in height from one to three stories, with the majority of 

buildings (57%) having one story. 

The survey area is located in a commercial district of downtown Napa. 

Accordingly, the majority of buildings (59%) include retail or restaurant 

space. The next two most common occupancy types are offices (16%) and 

government (9%). The surveyed buildings also include three parking 

garages, two warehouses, two theaters, and one hotel. Figure 3-3 shows the 

distribution of buildings by occupancy type. 

3-4 3: Performance of Buildings Near Station N016 FEMA P-1024 
 

 

 

	 

Unknown, 1 Other, 2 Hotel, 1 

Theater, 2 

Warehouse, 2 

Retail/Restaurant, 40 

Office, 11 

Government, 6 

Garage, 3 

Figure 3-3	 Distribution (by count) of buildings by occupancy type (of a 

total of 68 buildings). 

The Napa River runs through the survey area. Many of the buildings in the 

surveyed area are located immediately adjacent to the river. The FEMA 

Flood Insurance Rate Map (FIRM), Panel 516 of 650, for Napa shows that 

while most of the study area lies within Zone X (higher elevation than the 

0.2-percent-annual-chance flood), only one of the buildings was within Zone 

AE, but it was adequately elevated above the Base Flood Elevation of 18 

feet. With the exception of three buildings, all of the buildings were 

observed to be on level sites. 

3.5 Model Building Type 

In the survey area, masonry bearing wall systems make up more than half of 

the inventory, though a wide range of building types are represented in 

smaller numbers. Information about building type was provided on 93% of 

the building surveys and was not reported on the remaining 7%. 

Unreinforced masonry (URM) construction is the most common original 

structural system (41% of the buildings) in the surveyed area. The second 

most prevalent type is reinforced masonry with 22% of the buildings. NonFEMA P-1024 3: Performance of Buildings Near Station N016 3-5 
 

 

 

 

	 

tilt-up concrete shear wall buildings are the third most common with 7%. 

Other building types present include: wood-frame (light-frame and longspan), precast/tilt-up concrete shear wall, concrete moment frame, steel 

frame (moment and braced), and light-gage steel. Figure 3-4 shows the 

breakdown of the surveyed buildings by their original structural system. 

Concrete Moment 

Unreinforced Masonry 

Bearing Wall, 28 

Reinforced Masonry 

Bearing Wall, 15 

Concrete Shear Wall 

Building, 5 

Unknown, 5 

Wood Light 

Frame, 3 

Precast/Tiltup Concrete 

Shear Walls, 2 

Commerical or Long 

Span Wood Frame, 2 

Steel Frame w/ Infill 

Masonry Shear Walls, 2 

Frame, 2 

Steel Moment Frame, 1 

Steel Braced Frame, 2 

Steel Light Frame, 1 

Figure 3-4	 Distribution (by count) of buildings by original structural system 

(of a total of 68 buildings). 

A major focus of this investigation was the performance of seismically 

retrofitted unreinforced masonry buildings; of the 28 URM buildings, 71% 

(20 buildings) have been retrofitted. Figure 3-5 shows the retrofit status of 

the unreinforced masonry buildings in the survey. 

3-6 3: Performance of Buildings Near Station N016 FEMA P-1024 
 

 

	 

	 

Unknown, 1 

Retrofitted 

URM, 20 

Unretrofitted 

URM, 7 

Figure 3-5	 Distribution (by count) of unreinforced masonry building 

retrofits (of a total 28 URM buildings). 

3.6 Performance Modifiers 

More than half of the buildings (57%) were identified as having inadequate 

separation between adjacent buildings to preclude pounding. Storefront 

windows are common in the area, and approximately half of the buildings 

have open front plans (46%). Plan irregularities were identified in 21% of 

the buildings and structural deterioration was observed in 7%. 

3.7 Nonstructural Elements 

Parapets were observed on half (50%) of the buildings. Chimneys were 

uncommon in the area, observed in only 6% of the buildings. 

3.8 General Damage 

Information about damage to each building was collected for the structural 

system. Two independent damage rating systems were used in the survey: 

	 General Damage Classification: Damage is classified based on the 

extent of repairs required. The scale ranges from no visible damage 

(“none”), to “insignificant,” “minor,” and “moderate” to extensive 

damage for which repair may not be economically feasible and could 

require building demolition (“heavy”) and “collapse.” Surveyors were 

permitted to classify the damage as “unknown” if thorough observation 

to classify the damage was not safe or feasible. Appendix A provides 

detailed descriptions for each level. 

FEMA P-1024 3: Performance of Buildings Near Station N016 3-7 
 

 

 

 

 

	 

 ATC-13 Damage State: Damage is classified based on percent damage 

(damaged value divided by replacement value) and is based on ATC-13, 

Earthquake Damage Evaluation Data for California (ATC, 1985). 

Appendix A provides detailed descriptions for each level. 

3.8.1 General Damage Classification 

Distribution of building damage by General Damage Classification is shown 

in Figure 3-6. Overall, nonstructural damage was more common than 

structural damage: 80% of buildings were observed to have some degree of 

nonstructural damage, while 54% were observed to have some degree of 

structural damage. However, the most severe damage classification “Heavy” 

was only observed for structural systems; classifications of nonstructural 

damage were limited to “insignificant” (40%), “minor” (19%), and 

“moderate” (10%). However, it is noted that UNSAFE placards limited 

access to observation of nonstructural damage, so these buildings with 

greater levels of structural damage may well have also had greater amounts 

of nonstructural damage, but because this could not be verified, they have 

been categorized under “Unknown.” Number of Buildings 30 

25 

20 

15 

10 

5 

0 31 13 17 27 9 13 2 7 6 0 3 8 

Structural Damage 

Nonstructural Damage 

None Insignificant Minor Moderate Heavy Unknown 

Figure 3-6	 Distribution of building damage according to general damage 

classification. 

3.8.2 ATC-13 Damage State 

Distribution of building damage by ATC-13 Damage State is shown in 

Figure 3-7. The data for these assessments show a similar pattern for 

nonstructural and structural components as that observed in Section 3.8.1. 

More buildings were assessed to have some degree of nonstructural damage 

than structural damage, although nonstructural damage was clustered in the 

less severe states: “slight,” “light,” and “moderate.” Three buildings were 

3-8 3: Performance of Buildings Near Station N016 FEMA P-1024 
 

60 

assessed as having “heavy” or “major” structural damage, compared to only 

one building having this severity of nonstructural damage. 

This classification system also included assessments for equipment and 

contents damage. Observation of equipment damage was the lowest of the 

four categories, with only 19% of buildings. Contents damage was common, 

with 56% of buildings affected. Two buildings had contents damage 

classified as “Heavy.” 

No buildings were classified under any category as “Destroyed” (100% 

damage). 

Structural Damage 

Number of Buildings 

50 

40 

30 

20 

10 

0 

40 14 7 3 24 26 15 4 0 1 0 0 2 55 10 1 0 2 30 24 10 0 2 2 

0% (None) 0%-1% (Slight) 1%-10% (Light) 10%-30% (Moderate) 30%-60% (Heavy) 60%-100% (Major) 

Nonstructural Damage 

Equipment Damage 

Contents Damage 

Figure 3-7	 Distribution of building damage according to ATC-13 damage 

states. 

3.9 Structural Performance 

More than half of the buildings (37) within the 1,000 foot radius of Station 

N016 sustained some structural damage but the General Damage 

Classification was “insignificant” or higher for only half of these. The 

majority of the damage was reported as minor cracking in concrete and 

masonry buildings. 

For the 68 buildings in the study area, no damage to structural components 

was reported for 31 buildings (46%), and insignificant damage was reported 

for 17 buildings (25%). A total of 9 buildings (13%) sustained minor 

structural damage and 2 buildings (3%) sustained moderate damage; with 6 

buildings (9%) sustaining heavy damage. The level of structural damage in 

three buildings could not be determined. 

Of the 39 non-URM buildings with reported damage states, 36 sustained 

either insignificant damage or no damage. One building suffered heavy 

FEMA P-1024 3: Performance of Buildings Near Station N016 3-9 
 

 

 

	 

	 

	 

	 

	 

	 

	 

	 

damage when a URM wall from an adjacent structure collapsed into structure 

and a portion of one building (Napa County Courthouse, discussed in greater 

detail in Section 4.3.7) sustained damage to its older portions. A single-story 

concrete structure built circa-1930 suffered insignificant damage, with 

cracking observed at the base and top of some concrete columns. 

Unreinforced masonry buildings (28) make up a large percentage of the 

surveyed buildings. Of the seven unretrofitted URM buildings, five were 

posted UNSAFE: 

	 One building was heavily damaged: The building is a two-story structure 

with a setback and sustained significant loss of masonry, with portions of 

the second story walls falling both into the single-story portion of the 

building and out into an adjacent alley. 

	 One building was moderately damaged and sustained serious damage to 

brick and stone URM walls, including a portion of an exterior wall that 

fell on a parked automobile. 

	 One building suffered insignificant damage, but was initially posted 

UNSAFE. It was subsequently reposted INSPECTED. 

	 Two remaining buildings were not accessible for inspection; the nature 

and severity of the structural damage to these buildings could not be 

determined: 

A single-story unretrofitted URM building was posted RESTRICTED USE, 

but was not accessible for inspection and the nature of the damage is 

unknown. A single-story unretrofitted URM commercial building suffered 

insignificant damage; it appears to have been unoccupied at the time of the 

earthquake. 

Among the 20 retrofitted URM buildings, 10 buildings sustained no 

structural damage or the damage was deemed insignificant; six buildings 

suffered minor damage, one building moderate damage, and three were 

heavily damaged. No buildings collapsed. Among the buildings sustaining 

minor damage, two showed minor cracking of URM walls, and one building 

that was retrofitted with a combination of steel braced and moment frames 

sustained localized yielding and buckling in some of the steel elements. One 

of the two heavily damaged buildings is a two-story commercial structure 

that suffered extensive cracking to the URM walls, including X-cracking of 

slender URM piers. Damage to decorative terra-cotta elements was also 

significant. The other heavily damaged building, also a two-story structure, 

was reported to have sustained a wall anchorage failure. 

3-10 3: Performance of Buildings Near Station N016 FEMA P-1024 
 

A number of different approaches were used to retrofit URMs, and partial 

retrofits of URM buildings were less successful in limiting damage compared 

to those that received more comprehensive upgrades. Stone masonry walls 

and parapets were more likely to sustain damage compared to those of brick 

masonry. Overall, based on the performance of the URM buildings within 

1,000 feet of Station N016, it was observed that the hazard mitigation efforts 

in Napa were successful in reducing damage and the risk to life safety due to 

URM construction: Only 20% of the retrofitted URM buildings were posted 

UNSAFE (one additional building was posted UNSAFE due to damage to an 

adjacent structure), compared to over 70% of the unretrofitted buildings. 

No damage or Insignificant Minor Moderate Heavy 

Retrofitted 10 6 1 3 

Unretrofitted 3 0 0 2 

0 

2 

4 

6 

8 

10 

Number of buildings in group 

Figure 3-8 Damage comparison between unretrofitted and retrofitted URM 

buildings. 

3.10 Nonstructural Damage 

Information about damage to each building was collected for nonstructural 

components, equipment, and contents. Figure 3-9 shows the distribution of 

buildings for three major kinds of nonstructural damage: partitions, lights and 

ceiling, and contents. 

Although a majority of the buildings sustained damage in each of these three 

categories, the observable damage was mostly assessed as “insignificant.” 

Damage to contents was the most common of the three, with 24% 

experiencing a significant level of loss (“minor”, “moderate,” or “heavy”). 

Damage to lights and ceilings was the next most common, with 16%. 

Damage to partitions was sustained by the fewest buildings (8%). 

FEMA P-1024 3: Performance of Buildings Near Station N016 3-11 
 

 

 

 

	 	 

Number of Buildings 

None Insignificant Minor Moderate Heavy Unknown 

Figure 3-9 Number of buildings where select types of nonstructural 

damage was observed. 

The performance of parapets is summarized in Figure 3-10. Of the subset of 

buildings with parapets, 21% had observed damage. 

Partition Damage 

20 24 11 28 21 26 3 3 3 2 7 9 0 2 15 11 18

1 

Lights and Ceiling Damage 

Contents Damage 

30 

25 

20 

15 

10 

5 

0 

Damaged 

Parapets, 7 

Undamaged 

Parapets, 23 

Unknown, 4 

Figure 3-10 Distribution of parapet performance. 

For the 68 buildings in the study area, no damage to the nonstructural 

components was reported for 13 buildings (19%), and insignificant damage 

was reported for 27 buildings (40%). A total of 13 buildings (19%) sustained 

minor nonstructural damage and 7 buildings (10%) sustained moderate 

damage. The level of nonstructural damage in 8 buildings could not be 

determined. 

3-12 3: Performance of Buildings Near Station N016 FEMA P-1024 
 

Of the 27 buildings with insignificant damage, 11 were URM structures. 

Eleven buildings sustained some damage to glazing, and four of these were 

estimated to have lost 25% or more of their glazing area. The partitions and 

ceilings in the majority of the buildings sustained either no damage or 

insignificant damage. 

In the 13 buildings with minor nonstructural damage, damage to ceilings and 

lights was most common. Three buildings sustained minor, seven buildings 

sustained moderate, and two buildings sustained heavy ceiling damage. The 

majority of these buildings sustained no or insignificant partition damage. 

Two buildings sustained damage to 50% or more of their exterior glazing. 

Of the seven buildings with moderate nonstructural damage, four sustained 

some damage to partitions, and five had damage to ceilings. 

A total of 32 buildings (47%) had fire sprinkler systems. Damage was 

reported in five buildings. In one case, a number of short pipe hangers failed 

in an unbraced sprinkler system, but there was no loss of water. The 

sprinkler system developed a leak in one building, causing damage to an 

ornamental plaster ceiling. Sprinkler failures in three of the buildings 

resulted in flooding and significant damage to floor coverings and partitions. 

3.11 Injuries or Fatalities 

No injuries or fatalities were reported in the buildings surveyed. 

3.12 Functionality 

In this survey, full functionality is defined as all space in the building being 

usable in its pre-earthquake function. In most cases, loss of functionality 

resulted from damage to contents, nonstructural components and systems, or 

structural members. Given the commercial character of the area, full 

functionality was often synonymous with business operation. In a few cases, 

adjacency of the building to a damaged building delayed full functionality 

until the building was shielded from falling hazards. 

The surveys were conducted between 12 and 16 days following the 

earthquake, so responses of “immediate,” “1-3 days,” and “within 1 week” 

correspond to buildings that were fully functional at the time of the survey. 

In these cases, the length of time is based on conversations with occupants of 

the building and direct observation of the amount of usable space. Responses 

of “within one month” and “within 6 months” correspond to those building 

not fully functional at the time of the survey. For these buildings, the time to 

return to full functionality is a projection based on conversations with the 

occupants and the surveyors’ observations of the damage extent and realistic 

repair time. For roughly a third of the buildings (34%), adequate information 

FEMA P-1024 3: Performance of Buildings Near Station N016 3-13 
 

 

to record or estimate the length of time was not available and as a result, no 

information regarding return time to full functionality was provided for these 

buildings. It is likely that many of these buildings without adequate 

information were not functional after the earthquake and that the surveyor 

chose not to provide as estimate because they did not have enough 

information. 

For buildings where information was provided, less than one half of the 

buildings (44%) remained fully functional through the earthquake. Within 

one week of the earthquake, many buildings were able to make the necessary 

minor repairs, raising the percent of fully functional buildings to 89%. Based 

on projections by the surveyors, the number of fully functional building 

levels off with 91% building within one month and 98% of building full 

functional within 6 months. Figure 3-11 shows the duration to return to full 

functionality for buildings with information and estimates provided. 

One older county office building had to enact an asbestos abatement program 

after fire sprinkler damage revealed the presence of asbestos. Percentage of buildings fully functional 

100% 

90% 

80% 

70% 

60% 

50% 

40% 

30% 

20% 

10% 

0% 

44%, Immediate 

73%, 3 days 

89%, 1 week 

91%, 1 month 

(Projected) 98%, 6 months 

0 20 40 60 80 100 120 140 160 180 200 

Days after earthquake 

Figure 3-11 Building functionality: duration (in days) after earthquake to 

resume full functionality. 

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Chapter 4
 

Performance of Selected 

Buildings 

4.1 Introduction 

In this chapter, case studies documenting the performance of buildings are 

presented. The buildings described in this chapter were chosen to illustrate 

representative examples of seismic performance and include structures that 

sustained significant damage, as well as some that sustained little or no 

damage. The buildings are organized into the following groups of structures: 

•	 Newer construction: Any building designed and constructed using the 

1998 or later edition of the California Building Standards Code 

(California Building Standards Commission, 1998) 

•	 Older construction, excluding unreinforced masonry (URM) construction 

•	 Unretrofitted URM construction 

•	 Retrofitted URM construction with significant damage 

•	 Retrofitted URM construction with limited damage 

Table 4-1 provides a summary of the buildings discussed in this chapter. The 

chapter concludes with a summary of building performance observations and 

recommendations for improvements and further study. 

Table 4-1 Summary of Case Studies 

Structure Group Section 

Number of 

Case 

Studies 

Number of 

Buildings within 

1,000 ft Survey 

Area 

Newer 

Construction 

4.2 3 1 

Older 

Construction, 

not URM 

4.3 7 4 

URM Construction, 

not Retrofitted 

4.4 2 2 

URM Construction, 

Retrofitted 

4.5 and 

4.6 

10 10 

FEMA P-1024	 4: Performance of Selected Buildings 4-1 
 

 

 

 

 

 

 

Seventeen of the 22 buildings described in this chapter were located within 

the 1,000 foot radius around Station N016. Observations and performance of 

all buildings were recorded using the modified Postearthquake Building 

Performance Assessment Forms provided in Appendix A during field visits 

conducted over several days, two weeks following the earthquake. Each 

subsection describing a building summarizes information based on the form. 

The location of each building is designated with an alphanumeric code in the 

section titles. Buildings coded A-N were located within the 1,000 foot radius 

around Station N016, and are shown on Figure 4-1. Buildings coded Z were 

located outside of the 1,000 foot radius and their approximate locations are 

shown in Figure 4-2. It is noted that more detailed investigations were 

conducted for some buildings, and information gained is provided in the text. 

Figure 4-1 Key map providing alphanumeric designations for buildings within the 1,000 foot 

radius around Station N016 (image source: Google Maps). 

4-2 4: Performance of Selected Buildings FEMA P-1024 
 

 

 

 

 

 

 

 

 

 

 

 

	 

	 

Z5 

Z2 

Z6 

Z3 Z1 

Figure 4-2 Key map providing alphanumeric designations for buildings investigated but located 

outside of the 1,000 foot radius around Station N016 (image source: Google Earth). 

Building Z4 is not shown. 

4.2 Newer Construction 

For the purposes of this report, newer construction is defined as any building 

designed and constructed using a 1998 or later edition of the California 

Building Standards Code, which was based on the 1997 Uniform Building 

Code (ICBO, 1997). The most current edition of the California Building 

Standard Code is based on the 2012 International Building Code (ICC, 

2012a). Generally, newer construction sustained little or no structural 

damage. However, nonstructural damage resulted in the closure of several 

buildings, some of which will be closed for months. 

4.2.1 Three-Story Commercial Building, Main Street (Building L1) 

•	 Structural System, Height, Year Built: The building is a three-story 

tall steel concentric-braced frame structure with a wood-framed roof. An 

overview of the building is shown in Figure 4-3. The construction date is 

estimated as 2002. 

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Figure 4-3 Exterior view of building. 

•	 Occupancy Type: Retail and offices on the ground floor, offices on the 

upper floors. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted RESTRICTED USE. The City of Napa website reported damage 

at the north wall of the third floor, and a change in elevation of the floor 

in an office on the second floor. There was no access to the office at the 

time of the investigation and no observable distress was noted in the 

vicinity. 

•	 Structural Performance: No significant damage was observed. A 

brace on the north side of the building buckled elastically out-of-plane, 

causing some damage to the light-frame furring wall (Figure 4-4). 

•	 Nonstructural Performance: In general, very little nonstructural 

damage to the building was observed. There was almost no drywall 

damage observed on the first floor, and no ceiling damage reported. As 

noted above, there was damage to the light-frame furring at the third 

floor north wall, in the vicinity of one brace. Along the north wall, 

damage to the exterior wall occurred when the out-of-plane wall anchors 

of the adjacent building struck the drywall (Figure 4-5). No damage to 

equipment or piping, including the fire sprinkler system, was reported. 

•	 Time until Full Occupancy: The building remained operational. 

4-4 4: Performance of Selected Buildings	 FEMA P-1024 
 

 

 

 

 

 

	 

	 

	 

	 

Figure 4-4 Damage to steel studs due to out-of-plane buckling of brace. 

Figure 4-5	 Out-of-plane wall anchor of adjacent building penetrated 

drywall. 

4.2.2 Three-Story Office Building, Franklin Street (Building Z1) 

•	 Structural System, Height, Year Built: The structural system consists 

of a special welded steel moment frame with reduced beam sections 

(RBS). The building is three stories tall with basement parking, 

constructed in 2008. The front elevation is shown in Figure 4-6. The 

FEMA P-1024	 4: Performance of Selected Buildings 4-5 
 

 

 

 

 

 

 

	 

	 

	 

	 

	 

building is constructed with metal deck and concrete fill at the floors; the 

roof is constructed with untopped metal deck. Typical cladding consists 

of balloon-framed metal studs with gypsum fire sheathing and Portland 

cement plaster with stone veneer on foam substrate and solid stone 

veneer near the base. 

Figure 4-6 Exterior view of building. 

•	 Occupancy Type: Office. 

•	 Posting Placard: The building was posted UNSAFE immediately after 

the earthquake, but at the time of the field investigation, the building was 

posted INSPECTED. 

•	 Structural Performance: There was no reported structural damage. 

One RBS connection was exposed for examination approximately six 

weeks after the earthquake. No damage was observed at the connection. 

•	 Nonstructural Performance: The south exterior wall of the building, 

which contains large sections of solid wall, suffered the most significant 

damage (Figures 4-7 and 4-8). The wall, constructed with metal studs 

sheathed on the exterior with 5/8 inch gypsum fire-rated wallboard and 

approximately 1 1/4 inch of cement plaster (Figure 4-9), does not appear 

to have been detailed to accommodate story drift through a sliding or 

4-6 4: Performance of Selected Buildings	 FEMA P-1024 
 

 

 

 

 

 

 

 

	 

	 

	 

yielding mechanism. Consequently, the wall suffered several types of 

damage due to in-plane displacement, including failure of connections at 

the floors causing separation and bowing of the wall (Figure 4-10 and 

4-11), distressed studs, and plaster and gypsum wallboard cracking 

(Figure 4-12). In addition, the following damage was reported and/or 

observed: (1) Some adhered cast-stone foam-backed veneer and stone 

veneer became dislodged (Figure 4-12); (2) a water heater at the second 

floor, which was reportedly strapped, became dislodged, broke a water 

pipe and caused water to flow into an electrical room below where 

metering equipment suffered water damage; and (3) the glass in an 

interior room partition was broken. 

Figure 4-7 Damaged studs in exterior wall. 

•	 Time until Full Occupancy: The building was closed for several days 

following the earthquake and partially reopened within one week after 

the event. Portions of the building were vacated for three months to 

conduct detailed damage investigations of the south wall and to conduct 

related repairs. 

•	 Other Notes: This building is located outside of the 1,000 foot radius 

around Station N016. It was reported that the south wall was required to 

have a three-hour fire rating because of the proximity to an existing 

adjacent building, and that this heavier than normal construction may 

have contributed to the damage. 

FEMA P-1024	 4: Performance of Selected Buildings 4-7 
 

 

Figure 4-8 Bowed wall separated from floor (photo on right from Lauren Biscombe). 

H2.5 CLIP 

(HURRICANE 

TWIST STRAP) AT 

16” OC WITH 8 

NO. 10 SELFDRILLING 

SCREWS 

Figure 4-9 Detail from original drawings showing connection of exterior 

wall to each floor. 

4-8 4: Performance of Selected Buildings FEMA P-1024 
 

Figure 4-10 Failed wall anchor at bowed wall. 

Figure 4-11 Exterior wall, cracked plaster. 

FEMA P-1024 4: Performance of Selected Buildings 4-9 
 

 

 

 

 

 

 

 

 

 

	 

	 

Figure 4-12 Dislodged adhered veneer. 

4.2.3 Five-Story Hotel, 1st Street (Building Z5) 

•	 Structural System, Height, Year Built: This building is a five-story 

hotel, built in 2009. The front elevation is shown in Figure 4-13. It is 

rectangular in plan with an east-west longitudinal length of 254 feet and 

a north-south transverse length of 131 feet. A projection at the northeast 

corner is 26 feet by 55 feet. There is street frontage on the south and east 

sides, with car access through a tunnel under the northeast projection to a 

rear, north alley. There is a seismic joint between a building to the north 

and the northeast projection of the structure. The first floor is at street 

grade. 

Concrete bearing walls and columns and concrete masonry unit (CMU) 

walls at the first story support a post-tensioned concrete podium at the 

second floor. Interior walls bear on mat foundations; perimeter walls and 

columns bear on spread footings and perimeter grade beams. A number 

of the interior bearing walls continue up to the roof level. The third floor 

through roof level diaphragms are concrete fill on metal deck supported 

by the cold-formed stud bearing walls, light steel W-beams, concrete 

walls, and CMU walls. Steel tube columns in the stud walls support the 

ends of the W-beams. Lateral loads are resisted by the concrete and 

CMU shear walls. Above the podium level, shear walls are generally 

configured eccentrically to the floor plate and two street façades. 

The structural drawings indicate that the structural design used the 2001 

California Building Standards Code (California Building Standards 

Commission, 2001), which would be equivalent to the 1997 Uniform 

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Figure 4-13 Exterior view of building. 

Building Code (ICBO, 1997a). The building is clad with stone at the 

lower stories and stucco at the upper stories. The cladding is supported 

by concrete at the base and steel studs at upper stories. 

•	 Occupancy Type: Hotel and restaurant at the first story; hotel at the 

upper four stories. 

•	 Posting Placard: The building was posted RESTRICTED USE 

following the earthquake due to nonstructural falling hazards posed by 

loose stone veneer. The posting remained at the time of the field 

investigation. 

•	 Structural Performance: Cracking of a coupling beam over the door in 

the concrete tower around one stairwell was observed (Figure 4-14). 

Repairs included epoxy injection in cracks. 

•	 Nonstructural Performance: Substantial cracking at the stucco 

cladding and damage to the stone cladding were sustained (Figures 4-15 

and 4-16). It is estimated that less than 1% of the veneer became 

FEMA P-1024	 4: Performance of Selected Buildings 4-11 
 

 

 

 

 

 

 

 

 

Figure 4-14 Cracking in spandrel in concrete stair core. 

dislodged during the earthquake. After the earthquake, stone cladding 

was sounded with hammers and stones identified as loose were removed 

as part of repairs (Figure 4-17). The architectural drawings show control 

joint locations in the stucco and mortar joint locations for the stone. The 

architectural drawings also show anchored veneer, and the specifications 

require the anchors to accommodate vertical and horizontal movement 

between the stone and structural backing. However, based on field 

observations of damaged areas, it appears that veneer above the base was 

adhered, and there were no installed details that would explicitly allow 

for story drift in the stone cladding or stucco. 

The most significant damage was caused in the restaurant area by a 

single sprinkler head that impacted an adjacent beam and was triggered. 

This released water onto both wood and marble flooring (Figure 4-18) 

for several hours, causing enough damage that required the floor to be 

completely replaced. 

The seismic switch for the elevator was triggered, but the elevator was 

later brought back into use. Some ceiling tiles fell down. An emergency 

generator fell off its supports and severed a gas line, but the seismic 

shutoff to the gas line was triggered, preventing loss of gas and potential 

fire. There were cracks in the gypsum board partition finishes. Marble 

flooring tile was loosened. Mirrors above sinks fell and then damaged 

the finishes upon which they fell. Forty mirrors and sinks were 

identified for repair or replacement. 

4-12 4: Performance of Selected Buildings FEMA P-1024 
 

Figure 4-15 Adhered veneer damaged during the earthquake. 

Figure 4-16 Photo showing failed anchored veneer. 

FEMA P-1024 4: Performance of Selected Buildings 4-13 
 

 

 

 

 

 

	 

	 

Figure 4-17 Stone masonry veneer, showing where loose units have been 

removed. 

Figure 4-18 Sprinkler impacted HVAC components and discharged. 

•	 Time until Full Occupancy: Following the earthquake, hotel guests 

were transferred to other hotels in the area. The building was insured for 

earthquake damage and business interruption costs. Repairs took several 

months and the hotel was partially reopened (three out of the four floors 

with rooms) on December 15, 2014, approximately four months after the 

earthquake. Independent retail businesses on the first story of the hotel 

4-14	 4: Performance of Selected Buildings FEMA P-1024 
 

 

 

 

 

 

 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

remained open. It is important to note that building closure was entirely 

related to nonstructural damage. 

•	 Other Notes: This building is located outside of the 1,000 foot radius 

around Station N016. 

4.3 Older Construction Excluding URM 

This section describes the performance of buildings other than unreinforced 

masonry bearing wall structures constructed prior to the adoption of the 1998 

edition of the California Building Standards Code. Damage observed in 

these buildings generally highlighted known vulnerabilities. 

4.3.1 Three-Story Commercial Building, 1st Street (Building I1) 

•	 Structural system, height, year built: The building is a three-story tall 

steel frame structure with URM infill. An overview of the building is 

shown in Figure 4-19. The building was constructed in 1914. 

Figure 4-19 Exterior view of building. 

•	 Occupancy Type: Retail on ground floor, offices and public meeting 

rooms on upper floors. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted RESTRICTED USE due to falling debris. 

•	 Structural Performance: No significant structural damage was 

reported, this speaks very well for a 100-yr old structural system. 

FEMA P-1024	 4: Performance of Selected Buildings 4-15 
 

 

 

 

 

	 

	 

	 

• Nonstructural Performance: A few bricks fell from the façade, 

penetrating the cold-formed steel canopy over the sidewalk (Figure 

4-20). About 30% of the windows in the first floor storefront were 

damaged. Damage to lath and plaster wall finishes was widespread. 

There was minor damage to suspended ceilings in some areas (Figure 

4-21). A support leg of a commercial convection oven failed (Figure 

4-22). Unanchored and marginally anchored rooftop equipment 

displaced but did not fail. No damage to the fire sprinkler system was 

reported. 

•	 Time until Full Occupancy: Portions of the building were inaccessible 

to the public following the earthquake due to fallen debris. At the time 

of the field investigation, some of the retail establishments on the ground 

floor were open. The use of the upper floor spaces was restricted due to 

nonstructural damage. 

Figure 4-20 Damage to canopy due to falling brick. 

4-16	 4: Performance of Selected Buildings FEMA P-1024 
 

 

Figure 4-21 Minor damage to suspended ceilings. 

Figure 4-22 Convection oven with failed support leg. 

FEMA P-1024 4: Performance of Selected Buildings 4-17 
 

 

 

 

 

 

 

 

 

 

	 

	 

	 

	 

	 

4.3.2 Historic Post Office Building (Building Z3) 

•	 Structural System, Height, Year Built: The structural system consists 

of a steel frame with brick masonry infill. The extent of steel framing is 

unknown but steel corner columns were exposed by masonry damage, 

and the column-free interior suggests the presence of steel roof trusses. 

The building was dedicated in 1933. The building is one-story tall with a 

partial mezzanine and full basement. The front, north elevation of the 

building is shown in Figure 4-23. 

Figure 4-23 Exterior view of building. 

•	 Occupancy Type: United States post office. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted UNSAFE. 

•	 Structural Performance: Masonry piers sustained heavy damage on all 

elevations, but worse on front and rear sides. Corner piers sustained 

major inclined cracking two inches or more in width, rear elevation piers 

had cracking in excess of 1/2 inch (Figure 4-24). Some other piers 

shifted laterally at the sill line (Figure 4-25). Short segments of exposed 

corner columns indicate that they may be bowed or no longer plumb. No 

damage was reported in the basement. 

4-18	 4: Performance of Selected Buildings FEMA P-1024 
 

Figure 4-24 Damage to corner pier. 

Figure 4-25 Lateral shifting at sill line. 

FEMA P-1024 4: Performance of Selected Buildings 4-19 
 

 

 

 

 

 

 

 

 

 

	 

	 

	 

	 

	 

•	 Nonstructural Performance: Significant cracking was observed to the 

exterior brick veneer of the building, which is mostly a true veneer with 

anchor ties. Interior finish on exterior wall and interior partitions are 

hollow clay tile with plaster. These were heavily damaged, especially 

near the front corner piers, with significant fallen clay tile units and 

debris. Plaster ceilings were damaged, especially in the vicinity of the 

corner piers. Heavy glazing damage was also observed (Figure 4-26). 

Figure 4-26 Glazing damage. 

•	 Time until Full Occupancy: At the time of the field investigation, the 

building was inaccessible to the public following the earthquake due to 

damage. The building remained closed six monhs after the earthquake. 

•	 Other Notes: This building is located outside of the 1,000 foot radius 

around Station N016. It was reported that during the 2000 Yountville 

earthquake, numerous windows on the front elevation were broken. 

4.3.3 One-Story Retail Building, Clay Street (Building Z6) 

•	 Structural System, Height, Year Built: The store is a one-story, 

precast tilt-up concrete shear wall building with a flexible roof 

diaphragm constructed in 1973. The roof is constructed with plywood 

sheathing, 2x purlins and glulam beams supported by exterior concrete 

bearing walls and interior steel columns. The tilt-up panels are 

interconnected with cast-in-place pilasters. Three sides of the building 

have nearly solid concrete walls; the front has concrete walls on both 

4-20	 4: Performance of Selected Buildings FEMA P-1024 
 

 

 

 

 

 

 

 

	 

	 

	 

	 

	 

sides of the storefront. There have been no significant modifications to 

the structural system since the time of construction. 

•	 Occupancy Type: Retail store. 

•	 Posting Placard: Building was inspected by a structural engineer on the 

day of the earthquake and evacuated until emergency shoring was 

installed. On August 26, 2014, following the installation of out-of-plane 

wall bracing (Figure 4-27) and shoring of damaged glulam beams, the 

building was posted RESTRICTED USE. 

Figure 4-27 Shoring of wall with damaged pilasters. 

•	 Structural Performance: Five glulam beam-to-pilaster connections on 

the north wall of the building suffered damage at the pilaster connection 

(Figure 4-28). The top of the pilaster spalled or cracked around the 

anchor bolts. One mezzanine support beam experienced some damage at 

its connection to the rear wall. 

•	 Nonstructural Performance: One unbraced sprinkler line broke 

(Figure 4-29), and water ran for several hours. The lightly strapped hot 

water heater overturned breaking a water line but not the gas line, which 

had a flexible connection. There was damage to refrigeration equipment. 

The suspended acoustic tile ceiling was severely damaged, including 

substantial loss of tiles and failures in the grid, requiring replacement of 

FEMA P-1024	 4: Performance of Selected Buildings 4-21 
 

 

Figure 4-28 Damaged pilaster-to-roof beam connection. 

the entire ceiling (Figure 4-30). Some light fixtures were dislodged at 

their connections to the struts supporting them. Some unanchored store 

fixtures shifted or overturned. At one aisle, all of the fixtures along one 

side overturned into the aisle; there was substantial loss of contents from 

shelves, and virtually all the product was lost (Figure 4-31). 

Figure 4-29 Cracked sprinkler pipe. 

4-22 4: Performance of Selected Buildings FEMA P-1024 
 

 

 

	 

	 

Figure 4-30 Suspended ceiling damage. 

Figure 4-31 Overturned store fixture, loss of contents. 

•	 Time until Full Occupancy: At the time of the field investigation, it 

was reported that the building would be out of service for at least six 

FEMA P-1024	 4: Performance of Selected Buildings 4-23 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

months. Later it was reported that the store may be moved to a new 

location. 

•	 Other Notes: This building is located outside of the 1,000 foot radius 

around Station N016. The total cost of repairs is estimated to be 

approximately $1.5 million (approximately $500,000 attributed to 

structural repairs and shoring). 

4.3.4 Napa County Administration Offices (Building F2) 

•	 Structural System, Height, Year Built: This three-story tall building 

has a welded steel-braced frame structure with a basement. The building 

has plan irregularity (re-entrant corners). The construction date is 

estimated as 1970s. 

•	 Occupancy Type: Office. 

•	 Posting Placard: The building was not posted. 

•	 Structural Performance: A small number of weld fractures in the steel 

braced frames were reported, but there were no additional reports of 

significant structural damage. 

•	 Nonstructural Performance: Several of the large curb-mounted 

rooftop HVAC units and other rooftop equipment shifted as a result of 

anchorage failures. Movement of the equipment caused domestic water 

pipe breaks (Figure 4-32) in the penthouse resulting in water damage to 

the third floor ceilings. Most of the piping in the penthouse was 

unbraced. As a result of water damage, ceiling finishes in the hearing 

room collapsed. Some of the water damage to the ceilings was 

associated with failure of brazed/soldered piping connections to coils in 

the ductwork (Figure 4-33). The building does not contain a fire 

sprinkler system. Electrical components in the penthouse suffered water 

damage. 

There was extensive ceiling damage in some rooms of the third floor 

(Figure 4-34), with progressively less ceiling damage at each floor lower. 

At the third floor, about 20% of the grid was damaged, including some 

light fixtures that detached from the grid, although safety wires kept 

them from falling. In some areas, ducts disconnected from 

independently supported in-line HVAC components (Figure 4-33). 

Damage to gypsum board partitions spanning floor-to-floor was 

generally minor. Some modular partitions on the third floor came out of 

the top track and fell over, and were subsequently removed (Figure 4­

35). A reported failure mode was the partitions coming off their top 

tracks. Minor cracking of ceramic tile on the floor slabs was observed, 

4-24	 4: Performance of Selected Buildings FEMA P-1024 
 

as was minor damage to exterior insulation finishing system (EIFS) 

cladding. 

Figure 4-32 Evidence of pipe motion in penthouse partition wall. 

Figure 4-33 Ceiling and duct damage. The duct separated from the in-line 

HVAC unit to the right. 

FEMA P-1024 4: Performance of Selected Buildings 4-25 
Figure 4-34 Ceiling removed due to water damage, third floor. 

Undamaged 

modular partition 

Locations of 

damaged 

modular 

partitions 

removed (top 

track is still in 

place) 

Figure 4-35	 Third floor of building after the earthquake. Modular partitions 

similar to those at the left were damaged and removed. 

	 Time until Full Occupancy: The elevators were nonfunctional for two 

days. Portions of the building were unavailable following the earthquake 

due to water damage. At the time of the field investigation, two weeks 

after the earthquake, the third floor was still unoccupied. 

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4.3.5 Napa County Hall of Justice (Building F3) 

•	 Structural System, Height, Year Built: The building consists of two 

wings with reinforced concrete frames with CMU shear walls (Figures 

4-36 and 4-37). The building is three stories tall with a basement. One 

wing was constructed circa 1974, and has a concrete waffle slab floor 

system and precast concrete window units on the exterior. The 

penthouse of the 1974 wing is a steel frame structure with tension rod 

bracing. The second wing was built circa 1989, and has concrete flat 

slab floor systems. 

Figure 4-36 Exterior view, 1974 wing. 

•	 Occupancy Type: Correctional facility and offices. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted RESTRICTED USE. The City of Napa website reported visible 

damage in the court tunnel, and impairment of the domestic water 

system. 

•	 Structural Performance: Minor X-cracking in the first floor CMU 

shear walls was observed, along with minor spalling of the CMU face 

shells at the ends of the walls (Figure 4-38). Pounding damage was 

observed between the 1974 and 1989 wings (Figure 4-39). In the 1974 

wing, some damage was noted in the vicinity of the precast concrete 

panels containing the windows (Figure 4-40). These units are integrated 

into the CMU walls, without any allowance for isolating the panel from 

FEMA P-1024	 4: Performance of Selected Buildings 4-27 
 

 

the effects of story drift. The tension rods in the penthouse reportedly 

failed, but had been repaired or replaced at the time of site visit. 

Figure 4-37 Exterior view, 1989 wing. 

Figure 4-38 CMU face shell spalling, typical at base of walls. 

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Figure 4-39 Floor finish damage due to pounding at the seismic joint 

indicated by the arrow. 

Figure 4-40	 CMU damage at precast concrete panels containing the 

window. 

•	 Nonstructural Performance: Significant nonstructural damage was 

noted in the 1974 wing penthouse. Nearly all vibration-isolated 

components in the penthouse failed (Figure 4-41). Many failures were 

associated with splitting of the unreinforced concrete housekeeping slabs 

FEMA P-1024	 4: Performance of Selected Buildings 4-29 
 

 

 

 

 

 

 

 

 

(Figure 4-42), resulting in anchorage failures. The gas-fired emergency 

generator, which suffered vibration isolator failures, fell from its mounts 

and displaced laterally, but continued to function. The unbraced 

batteries for the generator slid but remained functional. A motor control 

center displaced several feet, but the conduits entering the unit at the top 

kept it from toppling. It was reported that four of the ten duct drops in 

the penthouse failed, but the nature of the failure could not be confirmed. 

Unbraced vibration isolated axial flow fans in-line with the ducts broke 

free from the ducts but did not fall. A mushroom fan on the roof toppled. 

Pumps failed their isolator mounts and were restrained by the pipe drops, 

and one pump pounded against an adjacent partition wall. Ducts and 

conduit crossing the seismic joint between the wings were not provided 

with flexible connections and some failed. Damage to suspended 

ceilings was noted (Figure 4-43), but no general failures of the grid were 

observed. On the third floor, some of the damage to the ceilings was 

associated with failure of brazed/soldered piping connections to coils in 

the ductwork. Damage to gypsum wallboard partitions due to story drift 

was generally minor. Some disruption to the hydraulic elevators due to 

buckled gypsum wallboard in the shafts was reported. 

Figure 4-41 Anchor failure, rooftop cooling tower 1974 wing. 

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Figure 4-42 Housekeeping slab failure, chiller in 1974 wing penthouse. 

Figure 4-43 Ceiling damage at seismic joint. 

The nonstructural components in the 1989 wing performed significantly 

better than those in the 1974 wing. No problems with piping connections 

to in-line coils were reported. No sprinkler issues were reported. 

• Time until Full Occupancy: Building remained operational. 

FEMA P-1024 4: Performance of Selected Buildings 4-31 
 

 

 

 

 

 

 

 

 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

4.3.6 Two-Story Retail Building, Napa Center (Building Z2) 

•	 Structural system, height, year built: The store is a two-story building 

of mixed construction. Figure 4-44 shows an overview of the building. 

The roof is sheathed with plywood supported by 2x wood framing, 

glulam beams, and steel columns. The second floor includes gypsum 

concrete fill on plywood supported by manufactured trusses, glulam 

beams, and steel columns. The lateral system includes pre-Northridge 

moment frames, chevron-braced frames, and plywood shear walls. 

Tenant improvements were constructed in 1987. The date of building 

construction is not known, but estimated as mid-1980s. 

Figure 4-44 Exterior view of building. 

•	 Occupancy Type: Retail. 

•	 Posting Placard: The building was posted RESTRICTED USE 

following the earthquake. A visible placard was not observed during the 

field visit. 

•	 Structural Performance: There was no reported structural damage 

reported or observed. 

•	 Nonstructural Performance: Water was released from five lines 

suspended from the roof for several hours (Figure 4-45). The sprinkler 

piping has threaded connections and damage appears to have been 

related to swaying and interaction with adjacent HVAC components 

(Figure 4-46). The elevator and escalator pits were flooded, and both 

systems required repair. Contents were damaged as a result of water; 

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some merchandise racks were overturned. Considerable amounts of 

gypsum wallboard were water damaged and required removal. The 

suspended acoustic tile ceiling was severely damaged, including damage 

to the grid (“free” ends came off ledger angle supports, “fixed” ends 

pulled out of the wall, and splices failed). A distance of up to 

approximately 70 feet was measured between parallel fixed- and freeends of the ceiling assembly. The ceiling contained splay wire bracing, 

but no compression posts. Suspended lights were installed with 

independent wire supports. Partitions were braced by the ceilings and 

may have contributed to the ceiling damage at some locations. Anchored 

air-handling units on the roof reportedly slid off their supports. 

Figure 4-45	 Water pressure from broken sprinkler line created a hole in the 

exterior cladding (photo by KCRA.com). 

	 Time until Full Occupancy: This building remained closed six monhs

after the earthquake.

	 Other Notes: This building is located outside of the 1,000 foot radius

around Station N016.

FEMA P-1024 4: Performance of Selected Buildings 4-33 
 

 

 

 

 

 

 

 

 

 

	 

	 

	 

Figure 4-46	 	 Damaged sprinkler pipe. Damage believed to have been 

caused by interaction with adjacent air handler. 

4.3.7 Napa County Courthouse, Brown Street (Building D1) 

•	 Structural System, Height, Year Built: The courthouse is comprised 

of three different structures. The west end is a 1916 concrete shear wall 

building. The central portion was built in 1977 and is a reinforced CMU 

infill building with concrete fill on metal deck floors supported by open 

web joists. The east end is the original URM historic courthouse built in 

1856 (Figure 4-47). The main level of the original courthouse is raised 

above grade; a ramp has been added for accessibility. The east façade 

has a series of setbacks in plan at the northeast and southeast corners, 

creating a series of short orthogonal walls. It is owned by Napa County, 

but houses State of California Court functions. The buildings form a 

rectangle in plan with the long direction of approximately 203 feet 

oriented east-west and the transverse direction of approximately 95 feet 

oriented north-south. There are two stories above ground in the 1856 

and 1916 portions and three stories in the 1977 portion. The building is 

set back from the street on the north, east, and south sides and abuts the 

sidewalk on the west side. At the time of field visits, it was surrounded 

with a fence set back a substantial distance from the north, east, and west 

façades. 

It was reported that in 1977, the URM building was partially retrofitted, 

and the central CMU structure was added. The CMU structure is 

seismically separated from the URM building. 

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Figure 4-47	 East façade of historic URM courthouse. Note fallen bricks 

below the damaged portion at the top of the wall. 

•	 Occupancy Type: Office and courthouse. 

•	 Posting Placard: The historic courthouse structure was posted with an 

UNSAFE placard. During a site visit on September 9, 2014, the concrete 

structure on the west side was posted with a RESTRICTED USE placard 

with the following annotation: “Damage to the east side of building. OK 

to use this entrance to secure building. Must be evaluated by an 

engineer.” Subsequently, the 1916 and 1977 portions of the building 

have been reopened. 

•	 Structural Performance: No structural damage was reported in the 

west (1916) and central (1977) portions of the structure. The east (1856) 

URM structure suffered extensive diagonal cracking to spandrels on the 

north-south façade, especially at the roof level, with heavier damage 

concentrated in masonry above the second floor and in the corner piers 

(Figure 4-48). There was partial collapse of the four-wythe brick attic 

wall at the southeast corner just below the roof. It was observed that 

roof-to-wall ties were no longer connected to the walls. Some minor 

damage was visible where the URM structure meets the CMU structure. 

•	 Nonstructural Performance: Significant damage to ceilings and plaster 

wall finishes in the URM structure, as well as water damage, were 

reported. The building was not accessible for field investigations, thus 

details are not known. 

FEMA P-1024	 4: Performance of Selected Buildings 4-35 
 

 

 

 

 

 

 

 

 

 

	 

	 

	 

Figure 4-48 Close-up of damage at top of the wall. 

•	 Time until Full Occupancy: At the time this report was being 

developed, the URM structure remained closed. The county court 

website (Napa County Court, 2015) notes: “After considerable 

remediation, the court has resumed partial operations in the newer 

portion of the Historic Courthouse... However, due to significant seismic 

damage to the historic portion of the building, including the front 

entrance, Departments A, B and N, as well as the Civil and Family Law 

Clerk’s Office, will continue to be closed indefinitely while it undergoes 

structural testing and analysis, and ultimately repair and reconstruction.” 

•	 Other Notes: The 1856 URM structure was damaged and closed 

following the 2000 Yountville earthquake. 

4.4 Unretrofitted URM Construction 

Unretrofitted URMs generally performed poorly, and would have caused 

many deaths and injuries had the earthquake occurred at a time when 

pedetstrians were walking on the streets. However, some unretrofitted 

URMs suffered only little or no damage as a result of immediate proximity to 

other newer or retrofitted buildings on each side, allowing them to effectively 

“lean” on their neighbors, the relatively short the duration of shaking, and in 

some cases, for reasons that have not been identified. 

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4.4.1 Two-Story Commercial Building, Brown Street (Building E1) 

•	 Structural System, Height, Year Built: The building is a two-story 

URM building with a flexible roof diaphragm (Figure 4-49). It was 

constructed in 1904. 

Figure 4-49 Failure of URM south wall (photo courtesy of Marko Schotanus). 

•	 Occupancy Type: Office. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted UNSAFE. It is reported that due to damage to this building and 

an adjacent structure, four surrounding buildings (Buildings E4, E9, E10, 

and E11) were also posted UNSAFE due to the risk of collapsing 

masonry walls striking the building. The surrounding buildings were 

subsequently posted INSPECTED following the erection of wood 

barriers (Figure 4-50). 

•	 Structural Performance: The masonry wall on the south side of the 

building separated from the structure and portions of it fell into the 

neighboring parking lot, striking an unoccupied, parked car (Figure 

4-49). Stones fell off the back of the building into the alleyway that 

separates the building from several retrofitted URMs (Figure 4-51). 

Large parapet stones fell into the attic space, which was used for storage. 

A large X-crack was observed in the north masonry wall. 

FEMA P-1024	 4: Performance of Selected Buildings 4-37 
Figure 4-50 Wooden barrier constructed on the roof a building neighboring 

a masonry wall at risk of collapse. 

Figure 4-51	 Failure of stone masonry east wall. Red arrow indicates wood 

barrier protecting adjacent property from falling stones. 

	 Nonstructural Performance: Cracking of the plaster wall and ceiling 

finishes was observed. HVAC equipment was damaged by falling stone 

masonry (Figure 4-52). 

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Figure 4-52 HVAC equipment damaged by falling stones. 

•	 Time until Full Occupancy: The building remained closed at the time 

this report was being developed. 

4.4.2 One-Story Restaurant Building, 1st Street (Buildings B2/B2A) 

•	 Structural system, height, year built: The building is a single-story 

structure that includes both CMU and unreinforced masonry walls, with 

a flexible roof diaphragm (Figure 4-53). The date of construction is 

unknown. 

Figure 4-53 Front elevation of Buildings B2/B2A. 

•	 Occupancy Type: Restaurant. 

FEMA P-1024	 4: Performance of Selected Buildings 4-39 
 

 

 

 

 

 

 

 

 

 

 

 

	 

	 

	 

	 

	 

•	 Posting Placard: At the time of the field investigation, the building was 

posted UNSAFE due to the collapse of a URM wall on the east side of 

the buildings, and collapse of the ceiling in the dining area. 

•	 Structural Performance: The building shares a common URM wall 

with the structure to the east (Building B3, located to the left of the roof 

drain in Figure 4-53, with the green awning). This wall collapsed into 

the dining area, striking about six tables (Figure 4-54). This is another 

example indicated that the time of the earthquake prevented increased 

numbers of injuries and fatalities. It was reported that a portion of the 

east URM wall above at the roof level that had not collapsed, being 

supported by a beam, was deemed a falling hazard. The parapet at the 

front of the building appeared to have displaced. No damage to the 

CMU walls was noted. 

Figure 4-54 Collapsed URM wall and ceiling in dining area. 

•	 Nonstructural Performance: The plaster ceiling in the dining area 

collapsed. Moderate cracking in interior wall finishes and exterior 

stucco was observed. No damage to equipment was noted. 

•	 Time until Full Occupancy: The building was closed for repairs at the 

time this report was being developed. 

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4.5	 Retrofitted URM Construction with Significant 

Damage 

City of Napa passed an ordinance in 2006 that required property owners to 

retrofit unreinforced masonry buildings by the summer of 2009. The stated 

objective of the ordinance was “to reduce the risk of death or injury” (Napa 

Municipal Code, Chapter 15.110). Some retrofitted URM buildings suffered 

damage as a result of incomplete seismic upgrading measures. Portions of 

buildings where improvements were limited demonstrated vulnerabilities 

over portions of the same building that were more comprehensively 

retrofitted. 

4.5.1	 Three-Story Office Building, 2nd Street, Napa, CA (Building 

E5) 

•	 Structural System, Height, Year Built: This three-story URM building 

was built in 1910 as a hotel and seismically retrofitted circa 1984 to 1986 

to house offices (Figure 4-55). This work included an addition to the 

structure. The retrofit consisted of the addition of steel moment and 

braced frames, and wall-to-floor and roof diaphragm anchorage. 

•	 Occupancy Type: Offices. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted both UNSAFE and RESTRICTED USE. The more heavily 

damaged portion of the building was posted UNSAFE. 

•	 Structural Performance: The building sustained a collapse of the top 

floor URM walls at the northwest and southwest corners (Figures 4-55b, 

4-56, and 4-57). The horizontal tube steel strongback was not effective 

at preventing the wall from collapsing out-of-plane. It was observed that 

the anchor bolts were straight and did not appear embedded through all 

brick wall wythes (Figure 4-58). The soffits of the roof cupola were 

several feet higher than the horizontal tube steel braces. The wall also 

reduced in thickness by at least one wythe above the horizontal braces. 

This resulted in a thinner, unbraced wall section, several feet high, 

spanning between the braces and soffits of the roof cupola. The collapse 

of the walls resulted in a loss of support to the wood-framed roof cupolas 

at the building corners, which were at incipient collapse following the 

earthquake. The other portions of the building sustained minor structural 

damage. 

FEMA P-1024	 4: Performance of Selected Buildings 4-41 
 

 

 

 

 

	 

	 

	 

(a) 

(b) 

Figure 4-55 Photographs of building: (a) circa 1910 and (b) 2014. 

•	 Nonstructural Performance: With the exception of areas in the 

vicinity of heavy structural damage, little nonstructural damage inside 

the building was reported. Several rooftop mechanical units slid off of 

their bases, most appeared to have little or no seismic anchorage. 

•	 Time until Full Occupancy: The less heavily damaged portions of the 

building reopened within two weeks of the earthquake. The heavily 

damaged portion remained closed at the time this report was being 

finalized. 

4-42	 4: Performance of Selected Buildings FEMA P-1024 
 

Figure 4-56 Collapse of URM walls supporting a corner cupola. 

Figure 4-57 Collapse of the URM wall at a corner cupola. 

FEMA P-1024 4: Performance of Selected Buildings 4-43 
 

 

 

 

 

 

 

 

 

 

 

	 

	 

Figure 4-58 Close-up of steel tube and masonry anchor at corner cupola. 

4.5.2 Two-Story Building, 1st Street (Building I2) 

•	 Structural System, Height, Year Built: This URM building is twostories tall, built in 1901, with a partial seismic retrofit at the roof in 1975 

and a comprehensive seismic retrofit and expansion in 2004 (Figure 

4-59). The building is rectangular in plan, 79 feet in the north-south 

longitudinal direction and 34 feet in the east-west transverse direction. 

There is about six feet of separation from the buildings on the west and 

east sides. The building is set back from the street on the north, and 

there is a parking lot at the rear, south façade. The first floor is above 

grade by approximately two feet, and there is a crawl space and 

mechanical subbasement. Exterior walls are two-wythe stone masonry. 

The roof is supported by wood carpenter trusses; the floors by wood 

framing. The top of the front façade has a tall parapet or tower feature 

that is rectangular in plan. There is an exterior steel framed fire escape 

on the east side. 

4-44	 4: Performance of Selected Buildings FEMA P-1024 
 

 

 

 

 

 

 

 

 

 

 

	 

	 

Figure 4-59	 Front façade showing damage and UNSAFE placard before 

scaffolding was installed. 

The 1975 retrofit is located above the roof and consists of steel tubes 

doweled to the inside face of the parapet that are coupled with horizontal 

bracing made of a pair of transverse tubes at third points along the 

longitudinal axis and diagonal tension bracing rod connecting the tubes. 

The City had not yet passed a URM ordinance at the time of the 2004 

retrofit. The federally-funded 2004 retrofit was designed using the 

requirements of the 1997 Uniform Code for Building Conservation 

(ICBO, 1997b). As a qualifying historic building, the provisions of the 

2001 California Historical Building Code (ICC, 2001) were also used. 

The 2004 retrofit provided enhancements to the 1975 retrofit including 

improved parapet ties using vertical drilled dowels down through the cap 

stone of the parapet, additional deeper horizontal drilled dowels 

connecting the steel top to the parapet, replacement of the tension rods 

with larger diameter rods, enhancement of the steel tube splices, and 

connection of the transverse tubes through the roof into the existing 

FEMA P-1024	 4: Performance of Selected Buildings 4-45 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

	 

	 

	 

	 

wood roof trusses. Although some of the 1975 rods were specified to be 

removed, they are still in place. A concrete diaphragm is shown several 

feet below the top of the front tower feature to connect the four parapet 

or walls of the tower together. 

The 2004 retrofit also included tension and shear ties from the walls to 

the roof, second floor, and first floor; a plywood overlay over the roof 

sheathing; a steel collector/chord at the second floor along the perimeter 

walls; reinforced concrete wall backing on the inside face of the front 

(transverse) façade; a transverse concrete wall with a grade beam, and 

diaphragm-to-wall collectors in the middle of the longitudinal direction; 

ties between members at the crawl space post and beam construction; 

anchor pins connecting the interior and exterior stone masonry wythes; 

epoxy injection of existing cracks; repointing; and some stone repair. It 

is possible that some of the repair work may have been associated with 

damage from the 2000 Yountville earthquake. 

Historic drawings indicate that there was a small wooden lean-to 

structure attached to the rear wall that was about eight feet in depth and 

rose up to the parapet level. It had been removed at some point prior to 

1999. The 2004 retrofit included a small two-story wood-frame addition 

at the same rear façade that provided an elevator and second stairway. 

No damage to the wood-frame structure was observed. 

•	 Occupancy Type: The building was originally constructed as the town 

library; it now houses offices and research library/archival space for the 

Napa County Historical Society. Offices are on the first story and offices 

and library space on the second story. 

•	 Posting Placard: The building was initially given an UNSAFE placard. 

Following installation of scaffolding on the west, north, and south sides 

and more permanent fencing, removal of loose wall and ceiling plaster, 

and closure of the front portion of the building, staff working in the 

building were permitted to reoccupy the southern portion of the building. 

An INSPECTED placard was posted at the rear entrance, granting access 

to the southern portion of the building. 

•	 Structural Performance: Damage included cracking of the stone 

perimeter façade pier near the roof level, typically through mortar joints, 

corner damage at all four corners with out-of-plumb movement of 

approximately 2 inches at the northwest and northeast corners and 4 to 6 

inches at the southwest corner. At the northwest corner, the masonry just 

below the cornice had shifted outward up to 3/4 inches. There were 

small fallen stones on the east façade, light cracking above the roof at the 

4-46	 4: Performance of Selected Buildings FEMA P-1024 
 

 

 

 

parapets at the southwest and southeast corners, and very significant 

damage to the front façade stone tower feature at the roof level that 

included fallen stone and shifting of the stone on mortar joints. See 

Figures 4-60 and 4-61 for damage at the front façade and tower feature. 

Figure 4-60 Cracking on east side of the tower feature. 

Figure 4-61 Top of concrete shear wall at roof level behind the tower 

feature. 

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The seismic retrofit work generally appeared effective in mitigating the 

original structural deficiencies, tying the structure together, and limiting 

damage to the masonry elements. Minimal movement was observed at 

the roof-to-parapet ties, and there were no obvious signs of diaphragmto-wall damage or residual offsets. See Figure 4-62 for a parapet tie at a 

corner. The two notable exceptions were outward movement at all four 

corners of the building and damage at the front façade tower feature. 

Figure 4-62 Steel tube bracing at parapet. 

The steel tubes at the roof extended around the corners and held the top 

of the wall and parapets together as did the second floor diaphragm-towall ties. The outward wall movement occurred below the cornice level 

that was approximately between the roof and second story ceiling levels. 

The concrete backing at the front façade stopped at the roof level and did 

not continue up the remaining height of the tower feature. The most 

significant damage began at about this level. The tower feature also did 

not have any parapet bracing or capstone ties like the other parapets. 

Reportedly, historic preservation concerns limited the extent of retrofit 

work that was implemented at the tower feature. 

•	 Nonstructural Performance: Lath and plaster at the walls and ceiling 

cracked and pieces fell (see Figure 4-63), there was movement at the 

second story ceiling, and many books fell from bookshelves in the library 

(the shelves were bolted to the floor). During a site visit on September 9, 

2014, the elevator was not functioning. The cab had descended to the 

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first floor level, and the light was on in the cab, but the doors did not 

fully open. Power, water, and computer service remained in operation. 

The water heater was strapped and was not damaged. No windows were 

broken despite the extent of shaking in walls and damage to furring. The 

steel fire escape on the east side was physically anchored to both 

buildings without a seismic joint on one side. Some out-of-plane pullout 

of the connection at the adjacent building was observed. 

Figure 4-63	 Lath and plaster ceiling damage and temporary taping at cracks 

and spalls. 

•	 Time until Full Occupancy: The building was closed until the interim 

scaffolding, fencing, and repair work were completed and reposted with 

the INSPECTED placard at the rear entrance on September 23, 2014. 

•	 Other Notes: The 2004 retrofit was partly funded by FEMA. As a 

result, California Office of Emergency Management is conducting a 

State Mitigation Assessment Review Team (SMART) assessment of the 

retrofit and damage, including review of retrofit costs and potential 

repair costs. 

4.5.3 Two-Story URM Building, 1st Street (Building J4) 

•	 Structural System, Height, Year Built: This URM building is twostories tall, built in 1905, and seismically retrofitted in 2004 (Figure 

4-64). Retrofit consists of steel moment frames on the open storefront 

façades on the south and east elevations and wall-to-diaphragm 

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anchorage. The north and west sides of the building have URM walls 

only, and no out-of-plane strengthening was provided between floors. 

Figure 4-64 Exterior view of building. 

•	 Occupancy Type: Restaurant on the first floor, offices on the second 

floor. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted UNSAFE. 

•	 Structural Performance: There was in-plane damage at the south 

façade (Figure 4-65) due to “bookend effect” (the two adjacent 

unretrofitted URM structures to the west had no lateral force-resisting 

systems). Out-of-plan punching shear failure of URM wall was observed 

at the second floor anchors of the south wall (Figure 4-66). The building 

suffered moderate to severe diagonal shear of URM at north and west 

walls. The floor-to-wall diaphragm connections for the north and west 

walls had only straight anchors to resist tension (not inclined at 22.5 

degrees), and many were pulled out. 

•	 Nonstructural Performance: Unknown. Building interior was not 

available for observation. 

•	 Time until Full Occupancy: The building remained closed six months 

after the earthquake. 

•	 Other Notes: The building suffered damage in the 2000 Yountville 

earthquake. Observed damage included cracking of spandrels along 

south façade and over the corner diagonal entry at southeast corner of the 

building (Figure 4-67). 

4-50	 4: Performance of Selected Buildings FEMA P-1024 
 

Figure 4-65 Cracking in URM on south façade. 

Figure 4-66 URM damage, west elevation (photo from Chris Jonas, ZFA 

Structural Engineers). 

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Figure 4-67	 	 Photo of Building J4 and detail of damage after the 2000 

Yountville earthquake (PEER, 2000). 

4.6 Retrofitted URM Construction with Limited Damage 

Most of the retrofitted buildings performed well. In some cases, limited 

sections of masonry became loose, and some were dislodged. 

4.6.1 Three-Story Theater Building, Main Street (Building L2) 

•	 Structural System, Height, Year Built: This three-story URM building 

was built in 1879 and seismically retrofitted over a period of years 

(Figure 4-68). This work included an addition to the structure. The 

retrofit consisted of the addition of steel moment frames along the front 

façade, parapet bracing (Figure 4-69), wall-to-floor and roof diaphragm 

anchorage, and steel strongbacks for the URM walls. The roof over the 

stage has been rebuilt with steel framing, and a CMU addition has been 

added to the rear of the structure. 

•	 Occupancy Type: Theater. 

•	 Posting Placard: The building was posted RESTRICTED USE. The 

City of Napa website indicates the fire alarm was on test, the elevator 

was not functioning, and the sprinkler system had been turned off. 

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Figure 4-68 Exterior view of building. 

Figure 4-69 URM parapet bracing. 

•	 Structural Performance: The building did not sustain significant 

structural damage. There is evidence of pounding with the structure to 

the south (Building L1). Some of the wall anchors on the south side of 

the building appear to have loosened, and these wall anchor bolts 

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damaged the wall of the adjacent building (Building L1) (Figures 4-5 and 

4-70). 

Figure 4-70 Loosened wall anchors on south wall, looking down. 

•	 Nonstructural Performance: A single fire sprinkler line failed at a 

threaded fitting above a walk-in cooler and flooded the first floor of the 

structure, damaging the hardwood floor. Minor cracking in the plaster 

wall and ceiling finishes was observed, and about 10% of the sprinkler 

head covers dislodged. The audio and lighting components suspended 

from the ceiling in the theater suffered no damage. In the theater, the 

crown molding made up of large fiberglass units was displaced in some 

areas. The door mechanism of the hydraulic passenger elevator 

malfunctioned; the freight elevator was undamaged. One compressor 

supported on a steel skid assembly suffered connection failures and 

shifted (Figure 4-71). Extensive loss of glassware and dishes in the first 

floor restaurant was reported, along with the loss of some stored wine. 

•	 Time until Full Occupancy: The building was closed for a week to 

repair water damage. 

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Figure 4-71 Connection failure at compressor. 

4.6.2 One-Story Restaurant Building, Main Street (Building L4) 

•	 Structural System, Height, Year Built: This single-story unreinforced 

stone masonry building, with mezzanines at the rear, was built in 1886. 

The building is split into three separate tenancies with solid demising 

stone masonry walls perpendicular to Main Street. The front façade 

(Main Street) is open. The rear façade is comprised of stone masonry 

piers and spandrels. The building was seismically retrofitted, including 

steel moment frames at the front façade, interior shotcrete overlays at the 

rear walls, out-of-plane wall anchorage to roof diaphragms and parapet 

bracing at the front façade. 

•	 Occupancy Type: Restaurant, retail, and office. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted RESTRICTED USE prohibiting access from Main Street due to 

parapet damage, but permitted access via rear and side entrances. 

However, there was no warning sign on the interior of the door and, the 

exit was being actively used by staff leading into the cordoned area. 

•	 Structural Performance: With the exception of the parapets (see 

Nonstructural Performance, below) the observed damage was generally 

minor (Figure 4-72). Minor to moderate cracking was observed at parts 

of the rear wall (Figure 4-73), specifically: at corners (stair stepped 

through bed joints) and inter-tenancy walls (both stair stepped through 

bed joints and through stone masonry units). It was unclear from visual 

FEMA P-1024	 4: Performance of Selected Buildings 4-55 
 

 

 

 

	 

	 

observation as to how or whether these crack patterns related to the 

shotcrete overlays on the interior face of the wall. 

Figure 4-72 Exterior wall on day of earthquake. 

Figure 4-73 Diagonal cracks in stone wall. 

•	 Nonstructural Performance: Stones were dislodged from the stone 

masonry parapets along the front and rear walls, with the majority of 

damage appearing to be on interior face of the parapet (Figures 4-74, 

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4-75, and 4-76). Some capstones were dislodged from the low-height 

parapet along the rear. Stone masonry chimneys at rear appeared 

essentially undamaged. It is unknown how or if these chimneys were 

retrofitted. Some glazing in the mezzanine broke, and there was minor 

loss of contents. 

Figure 4-74 Exterior face of parapet wall. 

Figure 4-75 Close up of dislodged stone on inside face of parapet. 

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Figure 4-76 URM parapet bracing, loss of stonework. 

•	 Time until Full Occupancy: One tenant was able to reopen within one 

day of the earthquake. The other tenant was able to reopen within three 

days. 

4.6.3 Two-Story Building, 3rd Street (Building M1) 

•	 Structural System, Height, Year Built: This URM building is twostories tall, built in 1887 and was seismically retrofitted in 2006-2007 

(Figure 4-77). The building is rectangular in plan, 120 feet in the northsouth longitudinal direction and 40 feet in the east-west transverse 

direction. The building stands alone with no adjacent structures. The 

building had been vacant for a number of years prior to the earthquake, 

and was surrounded by a fence. Exterior walls are two-wythe stone 

masonry. The ground story at the front façade has large window 

openings. There are limited openings on the east and north façades and 

no openings on the west façade. Buildings adjacent to the west façade 

were removed in 1999. The wood sheathed roof is supported by wood 

bowstring trusses at 20 feet on center with rafters and ceiling joists 

spanning north-south between the trusses. The second floor has steel 

W24 transverse girders supported by the masonry walls with sawn 

lumber joists spanning north-south to the girders that support wood floor 

sheathing. The first floor is slab-on-grade. 

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Figure 4-77 View from the southwest showing front façade and fencing. 

The City of Napa had not yet passed a URM ordinance at the time of the 

retrofit. The retrofit was done using the requirements of the 1997 

Uniform Code for Building Conservation. As a qualifying historic 

building, the provisions of the 2001 California Historical Building Code 

were also used. 

The retrofit included parapet bracing of the north (rear) and south (front) 

gable façade, a concrete bond beam atop the east and west walls, tension 

and shear ties from the walls to the roof and to the second floor, a 

plywood overlay over the roof sheathing and over the second floor 

sheathing, a steel moment frame at the first story of the front façade 

where masonry piers are limited, concrete shear walls at third points 

along the longitudinal length of the building, supplemental or secondary 

vertical supports under the roof trusses that continue to the foundation, 

anchor pins connecting the interior and exterior stone masonry wythes, 

and repointing of deteriorated mortar. Some existing tension tie bearing 

plates were present that may be from original construction. Regrouting 

of damaged or missing grout under these bearing plates was specified as 

part of the retrofit. One of the new interior transverse shear walls is Hshaped in elevation with a new grade beam below the walls and a 

collector strengthening an existing roof truss at the top of the walls. The 

other concrete wall assembly is associated with a new stair and elevator; 

it is supported by a concrete mat. The fire sprinkler and electrical 

systems were upgraded during the retrofit. 

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• Occupancy Type: Vacant, with a cold shell. Partitions were removed 

with the retrofit as were finishes on the inside face of much of the stone 

walls. Ceilings were also not present. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted with a RESTRICTED USE placard. No specific information was 

given regarding which areas were restricted. 

•	 Structural Performance: Damage includes stair-stepped cracking 

through mortar joints at piers and spandrels and loose stones over 

windows on the south façade, cracking and a fallen stone at the rear 

façade, and some light cracking at the east façade (Figures 4-78, 4-79, 

4-80). The fallen stone at the rear is near the midspan of the wall where 

out-of-plane accelerations would be largest. No damage was observed on 

the solid west façade. 

Figure 4-78 Loose stone cladding over window at front façade. 

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Figure 4-79 Diagonal cracking at inside face of second story pier at front 

façade. 

Figure 4-80	 Rear façade elevation. Red arrow points to the location where 

the stone fell at the center of the gable. 

•	 Nonstructural Performance: Minimal nonstructural elements exist in 

the building. The fire sprinkler and electrical power remained 

operational. 

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•	 Time until Full Occupancy: Not applicable, as the building was vacant 

at the time of the earthquake. 

•	 Other Notes: The 2006-2007 retrofit was partly funded by FEMA. 

4.6.4 Two-Story Commercial Building, Main Street (Building A1) 

•	 Structural System, Height, Year Built: This two-story unreinforced 

masonry building was constructed in 1890 and was seismically 

retrofitted circa 1985 (Figure 4-81). It appears that the adjacent building 

to the east shares a common URM wall with this structure. The retrofit 

consists of a steel moment frame at the first floor and steel braced frames 

at the second floor on the west elevation. 

Figure 4-81 Exterior view of building. 

•	 Occupancy Type: Restaurant and retail on the ground floor, offices on 

the second floor. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted RESTRICTED USE. The City of Napa website indicates that the 

wall adjacent to parking lot was leaning out. 

•	 Structural Performance: Minor damage (cracking through the stucco) 

was observed in the URM walls on the west and south elevations (Figure 

4-82). However, localized significant damage was observed at the southeast corner of the building, where the rear URM wall appears to be a 

common/party-wall with the adjacent building to the east. A relatively 

modern steel-framed exterior stair, which provides access to the second 

4-62	 4: Performance of Selected Buildings FEMA P-1024 
floor of adjacent building, is supported at the mid-height landing from 

the URM wall. The stair was rigidly attached to the URM wall, the 

adjacent building at the second floor, and at grade. The stair stringers 

appear to have acted as braces, inducing out-of-plane demands on the 

URM wall, which resulted in localized out-of-plane wall failure (Figure 

4-83). The upper stair stringer also buckled. 

Figure 4-82 Minor cracking in URM wall, north elevation. 

Figure 4-83 Southeast corner, damage to URM wall due to interaction with 

steel stair. 

FEMA P-1024 4: Performance of Selected Buildings 4-63 
	 Nonstructural Performance: About 50% of the glazing on the ground 

floor and 10% of the glazing on the second floor were damaged (Figure 

4-84). Minor cracking of the plaster wall and ceiling finishes was 

observed. No damage to the mechanical and electrical systems was 

reported. 

Figure 4-84 Damage to glazing, west elevation. 

	 Time until Full Occupancy: Some of the tenants on the ground floor 

were able to remain open; others were closed until the glazing was 

repaired. The second floor offices appear to have been occupied soon 

after the earthquake. 

4.6.5 Two-Story Restaurant Building, 1st Street (Building A2) 

	 Structural System, Height, Year Built: This two-story unreinforced 

masonry building was built in 1888 and has been seismically retrofitted 

(Figure 4-85). It appears that the adjacent building to the west shares a 

common URM wall with this structure. Retrofit comprised of adding 

lateral force-resisting elements in the transverse direction: a steel 

chevron braced frame at the 1st Street façade and a punched CMU wall 

at rear. The CMU wall was clad with a brick veneer. Parapet bracing and 

out-of-plane wall anchors were also observed; through-bolts with anchor 

plates were visible at roof level. 

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Figure 4-85 Exterior view of building. 

•	 Occupancy Type: Restaurant on the ground floor, offices on the second 

floor. 

•	 Posting Placard: This building was posted UNSAFE following the 

earthquake. At the time of the field investigation, the building was 

posted RESTRICTED USE. 

•	 Structural Performance: Minor damage (hairline cracking) was 

observed at the interior CMU retrofit wall. 

•	 Nonstructural Performance: The stonework parapet above the front 

entrance of the building dislodged (Figure 4-86). Anchorage failure at 

the parapet braces was observed, which may be due to poor adhesive 

installation of anchor bolts (Figure 4-87). One rooftop air conditioning 

unit failed at its base connection and slid slightly on the wood sleeper 

(Figure 4-88). The exterior steel framed stair at rear of building 

interacted with common/party-wall of the building to the west (Building 

A1) and caused out-of-plane wall failure (Figure 4-83). 

•	 Time until Full Occupancy: The building was closed for at least five 

days, although the business was essentially ready to re-open after three 

days except for the parapet repair and removal of posting. 

•	 Other Notes: $15,000 of contents damage to wine bottles and plates 

was reported. 

FEMA P-1024	 4: Performance of Selected Buildings 4-65 

 

Figure 4-86 Damage to stonework above main entrance. 

Figure 4-87 Failed wall anchor, north elevation. 

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Figure 4-88 Failure of air handler unit anchor, screws pulled out of sleeper. 

4.6.6 One-Story Restaurant Building, Main Street (Building A4) 

•	 Structural System, Height, Year Built: Built in 1933, this single-story 

building is constructed with 6-inch thick unreinforced hollow terracotta 

perimeter bearing walls, and a wood-framed roof (Figure 4-89). There is 

a small wood-framed addition at the rear of the building. The original 

structure was seismically retrofitted circa 2007 ($600,000 construction 

cost, with $200,000 lost revenue during construction according to 

owner). The retrofit was extensive. Unreinforced masonry foundation 

stem walls were strengthened with reinforced concrete overlays and 

grade beams. Plywood sheathed wood-frame walls (typically 2x6 at 24 

inches on center) were installed against the perimeter bearing terracotta 

walls to provide out-of-plane restraint and in-plane shear strength. The 

terracotta walls were anchored to the new wood-frame walls (6x6 studs 

at 4 feet on center) and strengthened roof diaphragm via threaded rod 

epoxy anchors. The relatively open storefront along Main Street was 

strengthened with an inverted moment frame, utilizing HSS14x10 posts 

cantilevered from a continuous grade beam. 

•	 Occupancy Type: Restaurant. 

•	 Posting Placard: At the time of the field investigation, the building was 

posted INSPECTED. 

•	 Structural Performance: No damage was reported. 

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Figure 4-89 Building elevation from Main Street. 

•	 Nonstructural Performance: The building contains beer tanks, kettles, 

and other equipment related to brewing operations. The only reported 

nonstructural damage was reported as: bottles and crockery falling, and 

an unanchored fermentation tank that slid 8 inches (Figure 4-90). The 

tank had flexible pipe connections which remained intact. Minor 

cracking of interior wall and ceiling finishes. 

•	 Time until Full Occupancy: Aside from clean-up of broken bottles and 

dishes, the restaurant was open and serving food on the day of the 

earthquake. 

•	 Other Notes: Station N016 is located in the crawlspace of the building, 

mounted to the top of the footing (Figure 4-91). Drawings of the seismic 

retrofit were available for review. The rear of the building is located 

immediately adjacent to the riverfront. 

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Figure 4-90 Unanchored tank shifted approximately 8 inches. 

Figure 4-91	 Photo of strong-motion recording instrument (Station N016) 

located in the crawlspace of Building A4. 

4.6.7 One-Story Restaurant Building, Main Street (Building E7) 

•	 Structural System, Height, Year Built: The building is a one-story 

unreinforced masonry building with a roof diaphragm constructed in 

1890 (estimated) (Figure 4-92). The building was retrofitted in 2005. 

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Figure 4-92 East elevation. 

•	 Occupancy Type: Restaurant. 

•	 Posting Placard: The building was posted UNSAFE shortly after the 

earthquake due to damage to an adjacent building, but was INSPECTED 

and in use within one week. One of the two tenants in the building 

remained closed for unknown reasons which may have not been related 

to the earthquake. 

•	 Structural Performance: No structural damage was observed. 

•	 Nonstructural Performance: The building suffered loss of several large 

storefront windows, and damage to contents, such as glasses and plates. 

No damage to the building mechanical and plumbing systems was 

reported. 

•	 Time until Full Occupancy: The building was closed for approximately 

a week. 

4.7 Summary 

Buildings constructed to recent codes (1997 Uniform Building Code or later 

editions of the International Building Code) generally performed well 

structurally. The vast majority of older, non-URM structures also performed 

well structurally, although known vulnerabilities, such as poor wall-to-roof 

connections, did result in significant damage and loss of use. 

Nonstructural components and systems in most buildings constructed to 

recent codes were damaged to some extent, and in some cases buildings 

sustained significant damage resulting in loss of use for an extended period. 

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Serious damage to exterior curtain walls and ceiling systems occurred in 

some structures. Pressurized piping system failures, especially fire sprinkler 

systems, caused extensive and significant water damage even though the 

actual number of piping failures was comparatively small. The losses would 

have been much less if the water supply to the sprinklers had been shut off 

after the piping failures. All fire sprinkler systems are equipped with control 

valves; however, they are normally locked in the open position to prevent 

tampering or accidental closure. Due to the hour of the event and the time it 

took someone with the control valve key to arrive on scene, broken sprinkler 

systems ran for hours in several cases, greatly aggravating the water damage. 

In some situations, the fire department shut off the control valve, but this is 

not their top priority as they were often too busy responding to life 

threatening incidents. Under these circumstances, failure of even a single 

sprinkler head caused extensive and widespread damage to wall, floor, and 

ceiling finishes. In most cases, nonstructural components in buildings 

constructed before 1998 were installed prior to the widespread enforcement 

of seismic bracing requirements. Nonstructural damage to suspended 

ceilings, equipment, and piping systems is to be expected in buildings of this 

vintage, and was fairly common. These issues are discussed in greater detail 

in Chapter 10. 

Among the retrofitted URM buildings, ten buildings suffered no structural 

damage, or the damage was deemed insignificant; six buildings suffered 

minor damage, one building moderate damage, and three were heavily 

damaged. None of the retrofitted buildings collapsed, and some exterior 

masonry loosened or fell from three of the damaged buildings. Based on the 

performance of the URM buildings in within 1,000 feet of Station N016, the 

URM hazard mitigation efforts in Napa were successful in reducing damage 

and protecting life safety. A number of different approaches had been used 

to retrofit URMs, and partial retrofits of URM buildings were less successful 

in limiting damage compared to those that received more comprehensive 

upgrades. Stone masonry walls and parapets seem more likely to sustain 

damage compared to those of brick masonry. 

Damage to lath and plaster walls and ceilings was common in URM 

buildings. Damage to glazing was more severe in unretrofitted buildings and 

in those buildings that utilized flexible moment frames at the storefronts. 

4.8 Recommendations 

The performance of buildings in the South Napa earthquake suggests several 

areas for possible improvement and further study, including: 

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1.	 Unretrofitted URM structures continue to pose significant risks to the 

public. Every effort should be made to eliminate the risks posed by these 

buildings. 

2.	 For ordinary building occupancies, building codes focus on preserving 

life safety by reducing the likelihood of building collapse in a very large 

earthquake. Many structural systems emphasize ductility, which can 

translate to structural damage in moderate events. The effects that this 

design approach has on the resiliency of communities subject to more 

frequent, smaller earthquakes should be explored. 

3.	 In modern buildings, the single focus on collapse prevention produces 

structures that are vulnerable to significant losses due to nonstructural 

damage, even in moderate event like the South Napa earthquake. For 

example, the code limits for building drift are such that serious damage 

to drift-controlled components, such as cladding, glazing, and partitions, 

is inevitable in moderate earthquakes. Further study is needed to develop 

drift-controlled components that can tolerate the displacements permitted 

by code. 

4.	 Even where the code specifies drift criteria for nonstructural systems, 

provisions for drift were often lacking in damaged buildings. Better 

coordination between the designer, contractor, and building officials is 

needed to ensure that proper seismic details are provided. 

5.	 The reliability of nonstructural components in ordinary occupancies 

needs to be improved. Recommendations for this are found in Chapter 

10. 

6.	 Chapter 34 of the current California Building Standards Code contains 

requirements for earthquake evaluation and retrofit of select vulnerable 

buildings undergoing significant modifications. Enforcement of code 

triggers related to the scope of renovations should be encouraged for all 

vulnerable buildings to reduce the structural and nonstructural risks they 

pose. 

The following are recommendations specific for improving URM building 

evaluation and retrofit methodologies: 

1.	 There was a wide range of retrofit approaches observed for URM 

buildings. Detailed assessments of selected buildings should be 

conducted to determine if common URM evaluation and retrofit 

methodologies accurately predict observed pier and spandrel cracking 

mechanisms. Findings can be incorporated into future updates of 

evaluation and retrofit guidelines. 

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2.	 With the exception of FEMA 306 and 307, Evaluation of Earthquake 

Damaged Concrete and Masonry Wall Buildings: Basic Procedures 

Manual and Technical Resources, (FEMA, 1998a and b, respectively) 

and recent New Zealand work, common URM evaluation and retrofit 

guidelines focus on pier mechanisms, but provide little guidance for 

spandrel mechanisms. Spandrel damage was observed in a number of 

buildings, and in some cases led to the formation of two-story tall pier 

mechanisms. Study of the cases where this was observed will be of 

value to better understand and predict this behavior and whether it should 

be incorporated into future updates of evaluation and retrofit guidelines. 

3.	 Poorly performing buildings often had retrofit schemes that were either 

incompatible with the properties of the buildings or were not sufficiently 

comprehensive. For example, flexible moment frames are less effective 

in protecting URM buildings than more rigid approaches. Tall URM 

walls may require intermediate supports for out-of-plane forces. 

4.	 Vertical cracking at corners, out-of-plumb leaning, and horizontal out-ofplumb movement at bed joints were observed in a number of buildings. 

Strong steel tubes well developed around the corner (corner ties) 

appeared to mitigate the movement and damage to some extent. 

Investigation of this issue is recommended to determine whether 

prescriptive requirements should be added beyond the typical reduced 

diaphragm-to-wall spacing requirements. 

5.	 There were a number of failures of adhesive-type anchors observed in 

retrofitted URM buildings. Failures could be due to a variety of factors, 

including detailing (straight versus bent anchors), problems with 

adhesion between the anchor and the substrate, deterioration of the 

adhesive material, or the effects of cracking in the masonry on anchor 

capacity. The cause of these failures should be determined and steps 

should be taken to improve the reliability of these anchors. 

6.	 Further study is recommended to assess possible variations in 

interpretations of State Historical Code and the International Existing 

Building Code requirements. In some cases, the goal of minimizing the 

impact to the historic fabric at historic buildings may have led to a 

reduction in the extent and scope of seismic retrofitting and may have 

contributed to damage of elements with reduced mitigation and an 

increase in localized life-safety risks. A study is recommended to 

identify examples of these issues and to develop ways to better address 

both historic preservation and sufficient seismic safety. 

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Chapter 5
 
 

Performance of Healthcare 

Facilities 

5.1 Introduction 

Following the catastrophic collapse of hospital buildings in the 1971 San 

Fernando earthquake, the 1972 Hospital Seismic Safety Act identified 

hospitals in California as essential facilities and established seismic 

performance goals for California hospitals stating: 

“...hospitals, that house patients who have less than the capacity 

of normally healthy persons to protect themselves,... must be 

reasonably capable of providing services to the public after a 

disaster...” 

Unlike most commercial buildings, hospital buildings are designed to remain 

operational after an earthquake. The California Office of Statewide Health 

Planning and Development (OSHPD) enforces the Hospital Seismic Safety 

Act. In addition to oversight of design and construction of hospitals, OSHPD 

performs postearthquake assessments of buildings under its jurisdiction. The 

assessments are performed by multidisciplinary teams of OSHPD staff, 

including structural engineers, inspectors, and fire/life safety officers, who 

examine the buildings and post them using procedures documented in ATC20 family of documents. Damage assessment reports are compiled and are 

available to the public. 

Following the South Napa earthquake, OSHPD activated its Emergency 

Operations Center (EOC) at 4:08 am, 48 minutes after the ground shaking. 

The EOC was staffed by 13 individuals. From the EOC, OSHPD dispatched 

ten investigation teams consisting of 22 total individuals to perform field 

operations. Based on proximity to strong shaking, the first teams were 

dispatched on August 24, 2014 to Queen of the Valley Hospital in Napa and 

Sutter Solano Medical Center in Vallejo. Building inspections continued 

through August 27, 2014. Investigation results were reported to back to the 

EOC on a regular basis. 

The information provided in this chapter was largely provided by OSHPD. 

EOC inspection results are also publically available on OSHPD’s website. 

FEMA P-1024 5: Performance of Healthcare Facilities 5-1 
 

5.2 Performance of Hospitals 

Six hospitals were located near the earthquake epicenter and were 

investigated by OSHPD following the earthquake. The locations of the 

hospitals are shown on the map in Figure 5-1, and more detail is provided in 

Table 5-1. 

Figure 5-1 Map of hospitals (shown as red “H”s) investigated following the 

South Napa earthquake (epicenter is shown as the red star) 

(image source: Google Earth). 

Table 5-1 List of Hospitals Investigated by OSHPD 

OSHPD Facility ID Hospital Name 

Distance to Epicenter 

(miles) 

13142 

Kaiser Foundation Hospital - 

Rehabilitation Center Vallejo 7.1 

12525 Sutter Solano Medical Center 7.2 

10362 

Queen of the Valley Hospital 

- Napa 7.7 

11013 

St. Helena Hospital Center 

For Behavioral Health 7.7 

11064 Sonoma Valley Hospital 9.4 

10366 St. Helena Hospital >15 

In general, hospitals performed well and remained operational following the 

earthquake. There was no significant structural damage reported, and no 

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building was closed as a result of structural damage. One room at Queen of 

the Valley Hospital in Napa was posted RESTRICTED USE after inspectors 

found a crack in a precast beam that required further evaluation. Other 

observed structural damage was limited to minor cracking of concrete wall, 

beam, and slab-on-grade elements. 

Nonstructural damage included damage to suspended acoustic tile ceilings, 

minor gypsum wallboard cracking, damage to a storefront glazing system, 

damage to exterior wall cladding, a small number of broken water pipes, 

movement of unanchored equipment and furnishings, and damage to 

expansion joint covers. Loss of power or a drop in power were reported at 

several hospitals. All emergency generators came on-line and provided 

electrical service to the facility. The Queen of the Valley Hospital ran on 

emergency generators for approximately three hours, while St. Helena 

Hospital experienced only a 35-minute power interruption during which 

emergency generators operated. Two hospitals had elevators out of service 

following the earthquake. 

The following sections provide a summary of the reported performance of 

each hospital. Table 5-2 provides summary description of structural system 

used in the sections that follow. 

Table 5-2 Structural System Descriptions 

Structural System Description 

C1 Concrete moment frame 

C2 Concrete shear wall 

S1 Steel moment frame 

S2 Steel braced frame 

S4 Steel frame with concrete shear walls 

PC2 Precast concrete frame with concrete 

shear walls 

RM1 Reinforced masonry bearing wall 

RM2 Reinforced masonry with rigid floor 

and roof diaphragms 

W1 Wood light frame 

W2 Wood light frame, commercial and 

industrial buildings 

5.2.1	 Queen of the Valley Hospital – Napa (OSHPD Facility ID 

10362) 

•	 Structural System, Height, and Year Built: The Queen of the Valley 

Hospital in Napa consists of 20 individual buildings. The oldest building 

FEMA P-1024	 5: Performance of Healthcare Facilities 5-3 
 

 

 

was constructed in 1957, and the newest is still under construction. 

Buildings range from one- to three-stories in height, and construction 

types include steel moment frames, concrete shear walls, precast 

concrete frames, and reinforced masonry. A plan of the hospital is 

shown in Figure 5-2. Descriptions of the buildings, including number of 

stories, structural system type, year built, and structural performance 

category (SPC) class and nonstructural performance category (NPC) 

class designations, are presented in Table 5-3. 

Figure 5-2 Queen of the Valley Hospital site plan indicating building numbers. Red lines indicate structural 

building separations. 

• Posting Placards: Between August 24 and 26, 2014, OSHPD teams 

investigated all 20 of the buildings and identified minor structural 

damage and widespread minor nonstructural damage. Three of the 

buildings were posted RESTRICTED USE, while the rest were posted 

INSPECTED. The entire hospital stayed in operation during and after 

the earthquake, and all essential services were maintained. 

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Table 5-3 Queen of the Valley Hospital – Napa Building Descriptions and Posting 

Building 

Number 

Building 

Name Stories 

Structural 

System 

Year 

Built 

SPC 

Class 

NPC 

Class Posting 

BLD-01650 Main Hospital 3 PC2 1957 1 2 RESTRICTED USE 

BLD-01651 West Wing 2 RM1 1964 1 2 INSPECTED 

BLD-01652 West Tower 2 S4 1973 2 2 INSPECTED 

BLD-01653 Conference 

Addition 

1 S1 1983 3 2 INSPECTED 

BLD-01654 Link Corridor 2 S1 1983 3 1 INSPECTED 

BLD-01655 South Elevator 

Tower 

3 C2 1983 4 2 INSPECTED 

BLD-01656 South Nursing 

Wing 

3 S1 1983 3 2 RESTRICTED USE 

BLD-01657 North Elevator 

Tower 

3 C2 1983 4 2 INSPECTED 

BLD-01658 North Nursing 

Wing 

3 S1 1983 3 2 INSPECTED 

BLD-01659 Maternity / 

Pediatrics 

2 S1 1983 3 2 INSPECTED 

BLD-01660 Admitting / Lobby 1 S1 1993 3 2 INSPECTED 

BLD-01661 Radiology 

Oncology 

Addition 

1 S2, C2 1995 4 2 INSPECTED 

BLD-01662 MRI Building 1 W1 1992 5 2 INSPECTED 

BLD-01663 Emergency 

Addition 

1 S1 1998 5 4 INSPECTED 

BLD-01664 Emergency 

Canopy 

1 S1 1998 5 4 INSPECTED 

BLD-02881 Canopy Addition 1 S1 1998 5 4 INSPECTED 

BLD-05309 North Acute Care 

Building 

3 S2 2014 5s 4 INSPECTED 

BLD-05323 North Acute Care 

Corridor 

3 Unknown 2014 5s 4 RESTRICTED USE 

BLD-05462 Imaging Center 

Canopy 

1 RM1 2007 5 4 INSPECTED 

BLD-05463 Women's Center 1 S1 2007 5 4 INSPECTED 

•	 Structural Performance: Some structural damage was observed. A 

crack in a precast beam (Figure 5-3) in the Main Hospital (BLD-01650), 

a three-story structure constructed in 1957, led investigators to post the 

the room below the beam RESTRICTED USE pending further analysis. 

Other minor concrete cracking was also identified in this building 

FEMA P-1024	 5: Performance of Healthcare Facilities 5-5 
 

 

(Figure 5-4). Minor cracking and spalling in a precast panel in the 

Conference Addition (BLD-01653) was noted (Figure 5-5); the building 

was posted INSPECTED. 

Figure 5-3 Damaged concrete beam at the third floor of BLD-01650. 

Figure 5-4 Cracked concrete wall piers in BLD-01650. 

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Figure 5-5 Cracked precast concrete panel in BLD-01653. 

•	 Nonstructural Performance: Nonstructural damage occurred 

throughout the hospital, in both the oldest and newest portions. 

Nonstructural damage included cosmetic cracking of gypsum board walls 

and ceilings (Figure 5-6), and acoustic tile ceiling damage (Figures 5-7, 

5-8). It is reported that the seismic switches tripped in the elevators. In 

the old Main Hospital building, damage to the rollers and bent guide rails 

disabled the two of the elevators. Water damage due to leaking pipes 

was noted (Figure 5-9), but there were no reports of flooding. Damage 

to a storefront glazing system resulted in a RESTRICTED USE posting 

at one hospital entrance (Figures 5-10 through 5-11). 

Figure 5-6 Cracked gypsum board wall in BLD-05309. 

FEMA P-1024	 5: Performance of Healthcare Facilities 5-7 
 

Figure 5-7 Third floor ceiling damage in BLD-05323 corridor link. 

Figure 5-8 Third floor ceiling damage in BLD-01656. 

Figure 5-9 Evidence of water leak in corridor of BLD-01650 (paint 

stretched to contain water). 

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Figure 5-10 South Nursing Wing storefront glazing damage leading to 

entrance posted RESTRICTED USE at BLD-01656. 

Figure 5-11	 South Nursing Wing storefront glazing damage leading to 

RESTRICTED USE posting at BLD-01656. Yellow line indicates 

amount of movement in the top track. 

Damage was also observed at seismic separation joints (Figures 5-12 

through 5-14). Some damage to rooftop equipment occurred, especially 

to electrical components on cantilevered supports (Figures 5-15 and 

5-16). Dust released as a result of movement between diffusers and 

sprinkler escutcheons and the ceiling compromised infection control and 

prevented the use of two operating rooms. In some cases, spontaneous 

opening of ceiling access doors compromised the sterile environment. It 

was also reported that cracking in ceiling or walls affected the air balance 

and the ability to maintain positive pressure in some operating rooms. 

Power was lost at this facility and emergency generators were activated 

for approximately three hours; the system performed as originally 

designed. All essential services were maintained. 

FEMA P-1024	 5: Performance of Healthcare Facilities 5-9 
 

 

 

Figure 5-12 Movement at seismic joint between BLD-01652 and 

BLD-01650 Main Hospital. 

Figure 5-13 Damage to seismic joint flashing between BLD-01654 and 

BLD-01655. 

Figure 5-14 Damage to seismic joint cover at second floor of BLD-01659. 

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Figure 5-15 Telephone rack on cantilevered supporting frame at roof of 

BLD-01650 severely out of plumb. 

Figure 5-16	 Electrical panel on cantilevered supports damaged at roof of 

BLD-01656. 

Suspended light fixtures were damaged when they struck one another 

(Figure 5-17). Content damage also occurred, including overturned 

office equipment, book cases, loss of contents off of shelving, and other 

items (Figures 5-18 to 5-20). 

•	 Time until Full Occupancy: Although two operating rooms were 

temporarily out of service, no services were disrupted. 

FEMA P-1024	 5: Performance of Healthcare Facilities 5-11 
 


 

Figure 5-17 Damaged light fixture in BLD-05309. 

Figure 5-18 Contents damage in BLD-01650. 

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Figure 5-19 Contents damage in BLD-01650. 

Figure 5-20	 Unanchored vending machine in BLD-01656 shifted over 12 

inches. 

5.2.2 Sutter Solano Medical Center (OSHPD Facility ID 12525) 

•	 Structural System, Height, Year Built: The Sutter Solano Medical 

Center in Vallejo consists of four individual buildings constructed 

between 1966 and 1989. Buildings range from one- to four-stories in 

height, and construction types include steel moment frames, steel braced 

FEMA P-1024	 5: Performance of Healthcare Facilities 5-13 
 

 

 

	 

	 

	 

	 

frames, concrete shear walls, and reinforced masonry. A plan of the 

hospital is shown in Figure 5-21. Descriptions of the buildings are 

presented in Table 5-4. 

•	 Posting Placard: All of the buildings at Sutter Solano Medical Center 

were posted INSPECTED. 

•	 Structural and Nonstructural Performance: No structural or 

nonstructural damage was observed. 

•	 Time until Full Occupancy: No services were disrupted. 

Figure 5-21 Sutter Solano Medical Center site plan. 

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Table 5-4 Sutter Solano Medical Center Building Descriptions and Posting 

Building Number 

Building 

Name Stories 

Structural 

System Year Built 

SPC 

Class 

NPC 

Class Posting 

BLD-01019 Original 

Hospital 4 C2 1966 2 2 INSPECTED 

BLD-01020 One Story 

Addition 1 RM1 1976 4 2 INSPECTED 

BLD-01021 Tower 

Addition 4 S1 1989 3s 2 INSPECTED 

BLD-02969 Two Story 

Addition 2 S2 1989 4s 2 INSPECTED 

5.2.3	 Kaiser Foundation Hospital – Rehabilitation Center Vallejo 

(OSHPD Facility ID 13142) 

•	 Structural System, Height, Year Built: The Kaiser Foundation 

Hospital – Rehabilitation Center in Vallejo consists of seven individual 

buildings. The oldest was constructed in 1970, and the newest was 

completed in 2010. A plan of the hospital is shown in Figure 5-22. 

Descriptions of the buildings are presented in Table 5-5. 

Figure 5-22 The Kaiser Foundation Hospital – Rehabilitation Center Vallejo site plan. 

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•	 Posting Placard: All of the buildings were posted INSPECTED. 

•	 Structural Performance: Observed structural damage was limited to 

cracking in the slab-on-grade. 

•	 Nonstructural Performance: Nonstructural damage included a second 

floor air handler unit that shifted, movement of unbraced mechanical, 

electrical, and plumbing distribution systems that caused minor damage 

to steel fireproofing, and cracks observed in non-bearing partition walls. 

Utility power was lost, and the emergency generator came on-line. 

•	 Time until Full Occupancy: No services were disrupted. 

Table 5-5 Kaiser Foundation Hospital Building Descriptions and Posting 

Building 

Number Building Name Stories 

Structural 

System 

Year 

Built 

SPC 

Class 

NPC 

Class Posting 

BLD-00204 Central Plant East 1 C2 1993 4 2 INSPECTED 

BLD-00205 Hospital Addition 3 S1 1996 3s 2 INSPECTED 

BLD-00206 ER Addition 1 S1 2001 3s 2 INSPECTED 

BLD-00207 Central Plant West 1 C2, RM1 1970 2 2 INSPECTED 

BLD-00208 Hospital 8 S1, C2 1970 1 2 INSPECTED 

BLD-02779 Hospital Tower 5 S2 2010 5s 4 INSPECTED 

BLD-03631 Central Plant East 

Storage / LOX 

2 C2 1993 4 2 INSPECTED 

5.2.4 Sonoma Valley Hospital (OSHPD Facility ID 11064) 

•	 Structural System, Height, Year Built: The Sonoma Valley Hospital in 

Sonoma consists of eleven individual buildings. The oldest was 

constructed in 1958 and the newest is still under construction. A plan of 

the hospital is shown in Figure 5-23. Descriptions of the buildings are 

presented in Table 5-6. 

•	 Posting Placard: All of the buildings at Sonoma Valley Hospital were 

posted INSPECTED. 

•	 Structural Performance: Observed structural damage was limited to 

cracking in the slab-on-grade. 

•	 Nonstructural Performance: Nonstructural damage was limited to 

minor cracking in gypsum board walls. 

•	 Time until Full Occupancy: No services were disrupted. 

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Figure 5-23 The Sonoma Valley Hospital site plan. 

Table 5-6 Sonoma Valley Hospital Building Descriptions and Posting 

Building 

Number 

Building 

Name Stories 

Structural 

System Year Built 

SPC 

Class 

NPC 

Class Posting 

BLD-01544 West Wing 3 C2, RM1 1970 2 1 INSPECTED 

BLD-01545 Central Wing 1 C2, RM1, 

W1 

1958 2 1 INSPECTED 

BLD-01546 East Wing North 1 RM1 1986 4 1 INSPECTED 

BLD-02990 Central Wing Canopy 1 S1 19893s 3s 1 INSPECTED 

BLD-02991 West Wing Canopy 1 S1 1989 3s 1 INSPECTED 

BLD-03079 East Wing Center 1 S1 1986 3 1 INSPECTED 

BLD-03080 East Wing South 1 W2 1986 4 1 INSPECTED 

BLD-03873 Chiller Building 1 RM2 1986 4 1 INSPECTED 

BLD-05409 East Wing Loading 

Dock Canopy 

1 S1 2012 5s - INSPECTED 

BLD-05410 ED / OR Unknown Unknown Unknown 5s - INSPECTED 

BLD-05411 ED / OR Canopy Unknown Unknown Unknown 5s - INSPECTED 

5.2.5	 St. Helena Hospital Center for Behavioral Health (OSHPD 

Facility ID 11013) 

•	 Structural System, Height, Year Built: The St. Helena Hospital Center 

for Behavioral Health in Vallejo is a single, one-story building from the 

1950s. 

FEMA P-1024	 5: Performance of Healthcare Facilities 5-17 
 

 

 

 

 

	 

	 

	 

	 

	 

•	 Posting Placard: All of the buildings were posted INSPECTED. 

•	 Structural and Nonstructural Performance: No structural or 

nonstructural damage was observed. 

•	 Time until Full Occupancy: No services were disrupted. 

5.2.6 St. Helena Hospital (OSHPD Facility ID 10366) 

•	 Structural System, Height, Year Built: The St. Helena Hospital in St. 

Helena consists of six individual buildings. The oldest was constructed 

in 1949, and the newest was completed in 2012. A plan of the hospital 

site is shown in Figure 5-24 and an overview of the building is shown in 

Figure 5-25. Descriptions of the buildings are presented in Table 5-7. 

Figure 5-24 St. Helena Hospital site plan. 

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Figure 5-25 Front entrance. 

Table 5-7 St. Helena Hospital Building Descriptions and Posting 

Building 

Number 

Building 

Name Stories 

Structural 

System 

Year 

Built 

SPC 

Class 

NPC 

Class Posting 

BLD-01666 Main Wing & Smoking 

Porch Addition 

5 C1, C2 1949 2 2 INSPECTED 

BLD-01667 East Wing 6 C1, C2 1949 2 2 INSPECTED 

BLD-01668 Ancillary Wing (ICCU 

Addition 5th floor) 

5 S2 1980 4 2 INSPECTED 

BLD-03031 Generator Building 1 RM1 1980 4 2 INSPECTED 

BLD-03554 Health Center 5 C2 1968 2 2 INSPECTED 

•	 Posting Placard: All of the buildings were posted INSPECTED. 

•	 Structural Performance: No structural damage was observed. 

•	 Nonstructural Performance: Limited nonstructural damage was 

observed. In particular, a 1 million gallon capacity tank that is part of the 

domestic water supply was disturbed such that sediment from the tank 

began appearing at plumbing fixtures. In response, the facility relied on 

bottled water, and the surgery area switched to using alcohol based hand 

cleaner. The separation joints between Buildings 01666 and 01667 and 

Buildings 01666 and 01668 suffered cosmetic damage (Figures 5-26 

through 5-28). Two elevators went off-line following the earthquake, 

and had to be returned to service by elevator service personnel. A 35-

minute power interruption occurred following the earthquake and the two 

emergency generators operated as designed and then switched back to 

normal power. 

FEMA P-1024	 5: Performance of Healthcare Facilities 5-19 
 

	 

	 

• Time until Full Occupancy: No services were disrupted. 

Figure 5-26 Cracking along the separation joint between BLD-01666 and 

BLD-01667 at the roof penthouse. 

Figure 5-27	 Cracking of the 1/2 inch to 1 inch thick topping slab over 

original roof slab inside the roof penthouse along the separation 

joint. 

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Figure 5-28	 	 Evidence of movement along the separation joint at the fourth 

floor between BLD-01668 and BLD-01666. 

5.3 Performance of Skilled Nursing Facilities 

Skilled Nursing Facilities (SNF) are also under the jurisdiction of OSHPD. 

Most SNFs are single-story wood or light metal framed buildings. 

Figure 5-29 Map of skilled nursing facilities (indicated with red pins) investigated following 

the South Napa Earthquake (epicenter indicated with a red star) (image source: 

Google Earth). 

FEMA P-1024 5: Performance of Healthcare Facilities 5-21 
 

 

 

 

 

 

 

 

Table 5-8 presents a list of the skilled nursing facilities are located near the 

epicenter and were investigated by OSHPD following the earthquake. 

Table 5-8 List of Skilled Nursing Facilities Investigated by OSHPD 

OSHPD 

Facility ID Skilled Nursing Facility Name 

Distance to 

Epicenter (miles) 

23264 The Meadows Of Napa Valley Care 

Center 

7.1 

20361 Piner's Nursing Home 11.3 

20363 Nazareth Skilled Nursing Center -

Napa 

11.6 

21030 Windsor Vallejo Nursing & 

Rehabilitation Center 

11.6 

22929 Crestwood Manor - Vallejo 11.6 

27780 Crestwood Hospital 11.6 

25194 Napa Valley Care Center 12.2 

20368 Golden Living Center - Napa 12.4 

21062 Sonoma Healthcare Center 14.2 

21015 Springs Road Living Center 14.9 

21046 Golden Living Center - London House 

Sonoma 

14.9 

21012 Heartwood Avenue Healthcare 15.3 

21061 Sonoma Acres 16.4 

All of the skilled nursing facilities were posted INSPECTED. No structural 

damage was identified at any of the facilities. In some cases, nonstructural 

damage was observed, including cracks in gypsum wallboard ceilings, 

damage to light fixtures, and leaking water pipes. 

Observed structural and nonstructural damage at each facility are presented 

in Table 5-9. 

Table 5-9 Skilled Nursing Facilities Building Descriptions and Posting 

Building 

Number 

The Meadows Of Napa Valley Care Center (OSHPD Facility ID 23264) 

Posting 

Structural 

Damage Nonstructural Damage 

BLD-04897 INSPECTED None Small cracking at two locations. One crack at 

the ceiling drywall across the corridor and 

another with uplift in what appears to be a 

nonstructural slab that is within the center of a 

connecting corridor between buildings. The 

emergency generator started due to power 

outage in the area. The gas was turned off 

pending the utility check of the building. 

5-22 5: Performance of Healthcare Facilities FEMA P-1024 
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 - - 

 

- 

- 

Table 5-9 Skilled Nursing Facilities Building Descriptions and Posting (Continued) 

Piner s Nursing Home (OSHPD Facility ID 20361) 

Building 

Number Posting Structural Damage Nonstructural Damage 

BLD-04022 INSPECTED None The facility had minor cosmetic 

damage, with some light fixtures 

damaged. Hot water heater piping 

was damaged due to unsupported 

piping. The emergency generator 

started due to the power outage in 

the area. 

Nazareth Skilled Nursing Center Napa (OSHPD Facility ID 20363) Exterior Review Only 

Building 

Number Posting Structural Damage Nonstructural Damage 

BLD-04023 INSPECTED None observed (facility is 

unoccupied, could not inspect 

the interior of this structure). 

There was a leak in the sprinkler 

line at the front entrance under the 

canopy. 

Windsor Vallejo Nursing & Rehabilitation Center (OSHPD Facility ID 21030) 

Building 

Number Posting Structural Damage Nonstructural Damage 

BLD-04256 INSPECTED None None 

Crestwood Manor Vallejo (OSHPD Facility ID 22929) 

Building 

Number Posting Structural Damage Nonstructural Damage 

BLD-04877 INSPECTED None None 

Crestwood Hospital (OSHPD Facility ID 27780) 

Building 

Number Posting Structural Damage Nonstructural Damage 

BLD-05744 INSPECTED None None 

Napa Valley Care Center (OSHPD Facility ID 25194) 

Building 

Number Posting Structural Damage Nonstructural Damage 

BLD-04955 INSPECTED None None 

Golden Living Center Napa (OSHPD Facility ID 20368) 

Building 

Number Posting Structural Damage Nonstructural Damage 

BLD-04024 INSPECTED None Generator started due to loss of 

utility power. 

Sonoma Healthcare Center (OSHPD Facility ID 21062) 

Building 

Number Posting Structural Damage Nonstructural Damage 

BLD-04268 INSPECTED None The generator required manual 

start. 

FEMA P-1024 5: Performance of Healthcare Facilities 5-23 
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Table 5-9 Skilled Nursing Facilities Building Descriptions and Posting (Continued) 

Springs Road Living Center (OSHPD Facility ID 21015) 

Building 

Number Posting 

Structural 

Damage Nonstructural Damage 

BLD-04252 INSPECTED None None 

Golden Living Center London House Sonoma (OSHPD Facility ID 21046) 

Building 

Number Posting 

Structural 

Damage Nonstructural Damage 

BLD-04264 INSPECTED None Utility power lost. The emergency 

generator alarm signal was on, the panel 

showed the generator was not in autostart mode but it did start up. 

Heartwood Avenue Healthcare (OSHPD Facility ID 21012) 

Building 

Number Posting 

Structural 

Damage Nonstructural Damage 

BLD-04250 INSPECTED None None 

Sonoma Acres (OSHPD Facility ID 21061) 

Building 

Number Posting 

Structural 

Damage Nonstructural Damage 

BLD-04267 INSPECTED None Utility power lost, the emergency 

generator came on without issues. 

5.4 Performance of Medical Office Buildings 

Many medical office buildings are designed and constructed under the 

authority of local jurisdictions and not OSHPD. They are generally not 

designed to remain operational after an earthquake. Most medical office 

buildings are one or two stories in height, many are of light-framed 

construction. 

There was no systematic investigation of the performance of medical office 

buildings following the South Napa earthquake. However, two medical 

office buildings in Napa experienced significant nonstructural damage to 

rooftop equipment. Air handler units, water heaters, and other rooftop 

equipment shifted and failed at the connections to the structure, despite the 

fact that they were constructed within the past ten years. 

5.5 Summary 

Hospital buildings generally performed well and remained open and 

functional to serve the communities affected by the earthquake. There was 

no significant structural damage reported, and no building was closed as a 

result of structural damage. Minor nonstructural damage was reported, and 

three buildings at Queen of the Valley Hospital in Napa were posted 

RESTRICTED USE as a result. Nonstructural damage included damage to 

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suspended acoustic tile ceilings, minor gypsum wallboard cracking, damage 

to a storefront glazing system, damage to exterior wall cladding, a small 

number of broken water pipes, movement of unanchored equipment and 

furnishings, and damage to expansion joint covers. Loss of power or a drop 

in power were reported at several hospitals. All emergency generators came 

on-line and provided electrical service to the facilities. Queen of the Valley 

Hospital in Napa had elevators out of service as a result of the earthquake in 

two hospital buildings. Two of the elevators in the old original building 

suffered damage and were taken out of service. 

Given the limited structural damage and continued operation of critical 

equipment and systems, hospitals that experienced the South Napa 

earthquake met the stated objective of the Hospital Seismic Safety Act. The 

level and duration of earthquake shaking experienced at the hospital sites 

coupled with OSHPD’s enforcement of the Hospital Seismic Safety Act are 

believed to be largely responsible for the good performance. 

The earthquake did, however, highlight some of the challenges associated 

with sustained operations following an earthquake. In order to maintain 

functionality, hospitals must have operable ventilation systems, be capable of 

containing contagious diseases, and provide an environment that does not 

adversely affect immune suppressed patients. Adequate sanitation and 

lighting are required, as are functional emergency power systems and 

medical gas systems. 

Both new and older hospital buildings experienced some nonstructural 

damage which, in a larger earthquake with longer duration, could have 

impacted the continuity of service. In particular, damage to exterior walls 

and ceilings in operating rooms was observed to have affected the ability to 

maintain required positive air pressure and the required number of air 

changes, thus impacting the sterile environment. Also, damage to suspended 

piping could have led to flooding and closure of portions of the hospital. 

Finally, damage to furnishings, which are generally not regulated by the 

building code, could have led to serious injuries. 

5.6 Recommendations 

The performance of healthcare facilities in the South Napa earthquake 

suggests several areas for possible improvement and further study, including: 

1.	 Detailing associated with cladding should be studied to ensure the ability 

to accommodate building drifts without unacceptable damage. 

Acceptable performance should be defined based on requirements for 

FEMA P-1024	 5: Performance of Healthcare Facilities 5-25 
 

 

 

 

 

 

 

 

 

 


 


 

	 

	 

	 

	 

	 

	 


 


 

	 

	 

	 

	 

	 

	 

maintaining sterile environments where required. This is further
 

discussed in Chapter 10.
 

2.	 Exemptions in current building codes that exempt seismic restraint 

requirements for most furnishings and contents should be examined to 

assess whether the resulting risk of injury is acceptable. This is more 

fully explored in Chapter 10. 

3.	 Immediately following the earthquake, OSHPD deployed multidisciplinary teams to conduct damage assessments of hospitals. Efforts 

should be made to develop a uniform format for the collected data to 

facilitate detailed follow-up studies. 

4.	 OSHPD postearthquake assessment teams must often make damage 

assessment decisions based on limited information on the structural 

attributes of the particular building. Consideration should be given to 

including a Structural Engineer engaged by the hospital in the assessment 

process, one who is familiar with the specific buildings and can provide 

expert information on the structure. 

5.	 Strong-motion instrumentation of hospitals should be expanded, and the 

information available from strong-motion instrumentation should be used 

as part of any future initiative to set related strategic goals for 

postearthquake recovery and assessment of design practices. 

6.	 The potential value of early warning systems should be explored as 

hospitals should be among the first users. An early warning system 

could give surgeons time to stop surgery, protect and cover a patient in 

the operating room, and take other steps to minimize disruption of patient 

care, such as opening elevators at the closest floor. 

5-26	 5: Performance of Healthcare Facilities FEMA P-1024 
Chapter 6 

Performance of School 

Facilities 

6.1 Introduction 

This chapter provides an overview and summary of seismic performance of 

school buildings and contents in the South Napa earthquake. There was little 

or no structural damage to the schools affected by the earthquake. Several 

schools did, however, experience nonstructural damage to architectural, 

mechanical, or electrical components, including suspended ceilings, light 

fixtures, equipment, and furniture. Some of the damage could have been life 

threatening had the earthquake occurred during school hours. 

Following the significant damage to school buildings in the 1933 Long 

Beach earthquake, the Field Act was established in California within 30 days 

of the earthquake to mandate earthquake-resistant construction of schools 

and to establish the Division of the State Architect (DSA, formerly Office of 

the State Architect). The Field Act requires DSA to review the design, 

construction, alteration, addition, or rehabilitation of public schools, 

kindergarten through 12th grade, and community colleges. Certain nonbuilding projects and minor alteration projects below a cost threshold may be 

exempt from DSA review under the Field Act. For those projects, school 

districts must ensure on their own that work complies. Private schools are 

regulated by local governments. A 1986 Private Schools Seismic Safety Act 

provides some enhancements compared to prior laws. 

After construction is completed, for both public and private schools, the 

owners of the school buildings are responsible for ensuring that school 

buildings are seismically safe and accessible. Many aspects in schools are 

not independently regulated, including furniture and minor nonstructural 

alterations. 

6.2 Napa Valley Unified School District 

There are 31 public school sites within the Napa Valley Unified School 

District. Figure 6-1 shows a map of all schools in the school district. The 

schools are generally one- or two-story buildings of wood-frame or 

reinforced masonry construction dating back to as early as the 1930s. 

FEMA P-1024 6: Performance of School Facilities 6-1 
Following the earthquake, schools were closed for inspection for two days. 

The District deployed three, three-person teams, each of which included an 

architect, a structural engineer, and a school district official. The school 

district also retained mechanical and electrical engineering consultants to 

inspect each school site and recommend repairs, where needed. Classes 

resumed on August 27, 2014 except at the Stone Bridge School, which did 

not reopen until September 2, 2014 due to a broken water main. 

Napa Valley Unified School District filed a preliminary estimate of $8 

million for building repairs. Replacing and repairing contents damaged by 

the earthquake was estimated at $9 million. Virtually none of the damage 

reported is characterized as “structural damage” impacting the safety of the 

gravity or seismic force-resisting systems in the school buildings. The 

observed damage was essentially all nonstructural, affecting the building 

cladding, interior partitions and ceilings, mechanical, electrical, and 

plumbing equipment and distributions systems, and contents. The following 

sections describe the observed damage. 

Figure 6-1 Map showing the locations of all schools in the Napa Valley 

Unified School District (image source: Google Maps). 

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6.2.1 Suspended Pendant Fixtures 

Suspended pendant light fixtures are common in classrooms. The pendant 

fixtures in the Napa Valley Unified School District facilities are typically 

suspended with aircraft (high-strength) cables fastened to the structural 

framing above with lag screws and to the light fixture with mechanical 

fasteners specific to each particular light fixture. The cables are generally 

provided with a means to adjust their length through the use of a cable 

gripper. Some installations include strut backing as a means to align the 

fixtures and reduce the number of hanger supports required. Some of the 

fixtures have supplemental wire bracing to walls or to the ceiling framing to 

limit swaying. 

Past earthquakes dating to the 1952 Kern County earthquake (in southern San 

Joaquin Valley) have demonstrated the vulnerability of pendant-hung 

fixtures to earthquake damage. Code requirements over the years have 

attempted to address many of the deficiencies observed in past earthquakes. 

An exception in Section 13.5.1 of ASCE/SEI 7-10, Minimum Design Loads 

for Buildings and Other Structures, (ASCE, 2010) allows suspended 

nonstructural components to be exempt from loading criteria under certain 

conditions. ASCE/SEI 7-10 also requires nonstructural connections that are 

“positively fastened” and do not rely on frictional resistance “produced by 

the effects of gravity.” DSA has also published Interpretation of 

Regulations, IR 16-9, Pendant Mounted Light Fixtures, (DSA, 2010) 

regarding pendant fixtures. However, even relatively recent installations of 

pendant fixtures have been observed to be vulnerable to damage that could 

threaten student safety. Of the 31 schools sites in Napa, 11 reported some 

damage to pendant fixtures and in five buildings at least one fixture fell from 

the ceiling. 

Several different types of damage were observed: 

	 The aircraft cable supporting the fixture slipped from the gripping 

connection (Figures 6-2 and 6-3) 

	 The connection of the aircraft cable to the fixture failed at the fixture 

(Figures 6-4 through 6-6). Figure 6-7 shows an undamaged connection. 

	 The bracing wire pulled out of its support (Figure 6-8) 

	 The lens cover dislodged (Figure 6-9) 

	 The bulbs dislodged and fell (Figure 6-10) 

In the five schools where at least one fixture was dislodged, similar 

vulnerable light fixtures and their support systems were removed and 

FEMA P-1024 6: Performance of School Facilities 6-3 
	 

replaced by the school district. Fixtures were removed and replaced in a total 

of 48 classrooms and two offices. 

Figure 6-2 Damaged light fixtures in classroom at Pueblo Vista Elementary 

School (photo by Quattrocchi Kwok Architects). 

Figure 6-3 Aircraft cable slipped out of the cable gripping support fixture at 

Pueblo Vista Elementary School (photo by Quattrocchi Kwok 

Architects). 

6-4 6: Performance of School Facilities	 FEMA P-1024 
Figure 6-4 Damaged light fixtures in Irene M. Snow Elementary School 

(photo by Quattrocchi Kwok Architects). 

Figure 6-5 Damaged light fixtures in Napa Valley Language Academy 

(photo by Quattrocchi Kwok Architects). 

FEMA P-1024 6: Performance of School Facilities 6-5 
Figure 6-6 Failed connection at light fixture in Napa Valley Language 

Academy (photo by Quattrocchi Kwok Architects). 

Figure 6-7 Undamaged connection to light fixture in Napa Valley Language 

Academy (photo by Quattrocchi Kwok Architects). 

6-6 6: Performance of School Facilities FEMA P-1024 
Figure 6-8 Bracing wire pulled out of wall at Harvest Middle School (photo 

by Quattrocchi Kwok Architects). 

Figure 6-9 Open lens covers at Shearer Elementary School (photo by 

Quattrocchi Kwok Architects). 

FEMA P-1024 6: Performance of School Facilities 6-7 
	 

Figure 6-10 Dislodged fluorescent bulbs at Shearer Elementary School 

(photo by Quattrocchi Kwok Architects). 

6.2.2 Furniture 

Schools and classrooms are filled with bookcases, cabinets, shelving, file 

cabinets, and similar furniture. Unrestrained furniture is subject to sliding in 

an earthquake. Tall, slender items, such as bookcases and shelving units, are 

prone to overturning. When items overturn, they pose a particularly 

hazardous condition for occupants either because they inflict direct injury or 

can block egress routes. 

Some furniture items are installed at the time a school is constructed, but 

most are installed on an as-needed basis throughout the life of the school 

facility. Since the installation of furniture over 6 feet tall is not regulated by 

the building code, the adequacy of the installation related to earthquake 

safety depends on voluntary implementation of good seismic practice. Such 

good practice is provided in publically available guidelines such as the Guide 

and Checklist for Nonstructural Earthquake Hazards in California Schools 

(Governor’s Office of Emergency Services, 2003), and FEMA E-74, 

Reducing the Risk of Nonstructural Earthquake Damage (FEMA, 2012a). 

There was considerable movement of furniture inside classrooms during the 

2014 South Napa earthquake. In many instances, the damage could have 

caused serious injury to students or staff had the rooms been occupied at the 

time of the earthquake or could have hindered emergency evacuation after 

the earthquake. In all cases where furnishings slid or overturned, there were 

6-8 6: Performance of School Facilities	 FEMA P-1024 
no visible measures in place to prevent such movement. Figures 6-11 

through 6-15 illustrate examples where overturned furniture created a safety 

risk. In cases where furniture did not overturn or move, contents were shed, 

sometimes posing a potential safety hazard as well (Figures 6-16 and 6-17). 

In contrast to free-standing furnishings, built-in casework approved by DSA 

installed at the time of construction performed uniformly well. No wallmounted cabinets experienced damage other than the loss of contents. 

Figure 6-11 Overturned cabinets in Irene M. Snow Elementary School 

(photo by Quattrocchi Kwok Architects). 

FEMA P-1024 6: Performance of School Facilities 6-9 
 

 

Figure 6-12 Overturned bookcase in Stone Bridge School (photo by 

Quattrocchi Kwok Architects). 

Figure 6-13 Overturned bookcase blocking exit in Stone Bridge School 

(photo by Quattrocchi Kwok Architects). 

6-10 6: Performance of School Facilities FEMA P-1024 
Figure 6-14 Overturned bookcase at doorway in Harvest Middle School 

(photo by Quattrocchi Kwok Architects). 

Figure 6-15 Overturned file cabinet in Harvest Middle School (photo by 

Quattrocchi Kwok Architects). 

FEMA P-1024 6: Performance of School Facilities 6-11 
	 

Figure 6-16 Dislodged books in Napa High School (photo by Quattrocchi 

Kwok Architects). 

Figure 6-17	 Contents dislodged from counters in Stone Bridge School wood 

shop (note drill press on floor) (photo by Quattrocchi Kwok 

Architects). 

6-12 6: Performance of School Facilities FEMA P-1024 
6.2.3 Ceilings 

Several ceiling types were affected by the earthquake, including suspended 

acoustic tile, gypsum wallboard or plaster fastened directly to framing (some 

with glued acoustic tiles), and combined systems. In general, damage to 

ceilings was very limited. In suspended acoustic tile ceilings, acoustic tiles 

were reported to have been dislodged in five out of 31 schools and damage to 

the ceiling grid was reported in three schools (Figures 6-18 and 6-19). The 

adequate performance of ceilings is likely related to a combination of factors 

including the duration and magnitude of shaking, the small size of the 

ceilings, bracing provided by classroom walls, the lateral bracing system 

including ceiling tile restraints, and the quality of installations. 

Although there was only limited damage to ceilings caused by the 2014 

South Napa earthquake, many suspended ceilings are actively being replaced. 

Since some ceiling components were variously bent, broken, and “altered” 

by the earthquake, this triggered replacements in accordance with 

Interpretation of Regulations, IR 25-2.13, Metal Suspension Systems for LayIn Panel Ceilings: 2013 CBC, (DSA, 2014) that states: “The entire ceiling 

shall be upgraded to meet the current requirements of the CBC and this IR if 

any portion of the grid system is cut or altered.” Thus, the limited 

earthquake damage to predominantly older ceiling systems is being used to 

trigger improvements to reduce damage in future events. 

Figure 6-18 Dislodged tiles and bent edge angle in a Silverado Middle 

School classroom (photo by Quattrocchi Kwok Architects). 

FEMA P-1024 6: Performance of School Facilities 6-13 
Figure 6-19 Damage to suspended acoustic tile ceiling in Napa Junction 

Elementary School (photo by Quattrocchi Kwok Architects). 

6.2.4 Interior Partitions 

Interior partitions observed typically consisted of full height wood or metal 

studs with gypsum wallboard or plaster sheathing. Reported damage was 

limited to minor cracking (Figures 6-20). In one school small areas of 

adhered ceramic tiles were dislodged (Figure 6-21). 

Figure 6-20 Gypsum wallboard cracking in New Technology High School 

(photo by Quattrocchi Kwok Architects). 

6-14 6: Performance of School Facilities FEMA P-1024 
 

Figure 6-21 Dislodged adhered tile in Harvest Middle School (photo by 

Quattrocchi Kwok Architects). 

6.2.5 Glazing 

Damage to glazing was limited. Broken windows were reported at three 

schools, but only one window was damaged at each school (Figure 6-22). 

Some schools experienced minor movement in the window framing system. 

Figure 6-22 Broken window at Harvest Middle School (photo by 

Quattrocchi Kwok Architects). 

FEMA P-1024 6: Performance of School Facilities 6-15 
 

6.2.6 Mechanical and Plumbing Systems 

In general, there was limited damage to mechanical and plumbing systems in 

schools. The earthquake restraint straps on two water heaters failed, but the 

tanks did not topple (Figures 6-23 and 6-24). A water main broke at Stone 

Bridge School, and a 28,000-gallon water tank was damaged at New 

Technology High School. The tank, which was anchored to a concrete 

foundation, was damaged at the connection between anchor brackets and the 

tank wall, causing ruptures in the tank wall and water release. There was 

also local buckling of the tank wall near the base. 

The rooftops of most schools support piping and equipment on wood 

sleepers. In many instances, the sleepers are unanchored. The South Napa 

Earthquake caused movement of piping, conduit, and equipment; however 

there was no loss of function reported for any of the rooftop equipment. 

Examples of the damage to rooftop equipment are shown in Figures 6-25 to 

6-29. 

Figure 6-23 Failed earthquake restraining strap on water heater (photo by 

Quattrocchi Kwok Architects). 

6-16 6: Performance of School Facilities FEMA P-1024 
Figure 6-24 Failed earthquake restraining strap at Shearer Elementary School 

(photo by Quattrocchi Kwok Architects). 

Figure 6-25 Shifted rooftop condensate unit at Redwood Middle School (photo by 

Quattrocchi Kwok Architects). 

FEMA P-1024 6: Performance of School Facilities 6-17 
Figure 6-26 Shifted rooftop make-up air unit at Napa High School (photo by Quattrocchi 

Kwok Architects). 

Figure 6-27 Broken condensate connection at air conditioning unit, 

Redwood Middle School (photo by Quattrocchi Kwok 

Architects). 

6-18 6: Performance of School Facilities FEMA P-1024 
Figure 6-28 Toppled disconnect for rooftop air handler at Napa High School 

(photo by Quattrocchi Kwok Architects). 

Figure 6-29 Shifted rooftop pipe supports at Silverado Middle School (photo by 

Quattrocchi Kwok Architects). 

6.2.7 Electrical Systems 

There was limited damage to electrical systems in schools in the South Napa 

Earthquake. Electrical damage was limited to loose conduit fittings and 

broken conduit elbows. Similar to piping, movement of unrestrained rooftop 

conduit caused damage at connections. 

FEMA P-1024 6: Performance of School Facilities 6-19 
Figure 6-30 Exposed wires at failed conduit fitting, Harvest Middle School 

(photo by Quattrocchi Kwok Architects). 

Figure 6-31 Shifted conduit at sleeper support, Harvest Middle School 

(photo by Quattrocchi Kwok Architects). 

6-20 6: Performance of School Facilities FEMA P-1024 
Figure 6-32 Shifted conduit at Napa Valley Language Academy (photo by 

Quattrocchi Kwok Architects). 

Figure 6-33 Broken low voltage conduit coupling at Redwood Middle 

School (photo by Quattrocchi Kwok Architects). 

FEMA P-1024 6: Performance of School Facilities 6-21 
Figure 6-34 Broken PVC conduit at Redwood Middle School (photo by 

Quattrocchi Kwok Architects). 

6.2.8 Concrete and Asphalt Cracking 

Several schools reported damage to concrete slabs-on-grade and one school 

reported damage to the asphalt parking lot, due to ongoing afterslip (see 

Chapter 2). The slab cracking generally occurred at existing slab 

construction joints. 

Figure 6-35 Cracking at slab joint in walkway at Harvest Middle School 

(photo by Quattrocchi Kwok Architects). 

6-22 6: Performance of School Facilities FEMA P-1024 
Figure 6-36 Cracks in asphalt parking lot at Stone Bridge School (photo by 

Quattrocchi Kwok Architects). 

6.2.9 Additional Observations 

At several schools, some doors were reported to be hard to open or binding 

after the earthquake. In some cases, the cause appears to have been 

movement of the building and in others the cause appears to be related to 

ground movement. All doors were operable, but with stronger shaking, it is 

possible that means of egress could have been compromised. 

FEMA P-1024 6: Performance of School Facilities 6-23 
Figure 6-37 Damaged door at Browns Valley Elementary School (photo by 

Quattrocchi Kwok Architects). 

6.3 Other School Facilities within Napa Valley 

6.3.1 Justin Siena 

Justin Siena, a parochial high school in Napa, 10 miles north-northwest from 

the epicenter, sustained nearly $60,000 in losses. Damage included broken 

windows, broken water mains, cracked wall finishes, damaged light fixtures, 

shifted equipment, toppled bookcases and furniture, loss of supplies, and 

damaged statuary (Figures 6-38 through 6-40). 

6-24 6: Performance of School Facilities FEMA P-1024 
Figure 6-38 Unrestrained bookshelf overturned in office (photo by 

Quattrocchi Kwok Architects). 

Figure 6-39 Toppled altar and statuary (photo by Quattrocchi Kwok 

Architects). 

FEMA P-1024 6: Performance of School Facilities 6-25 
Figure 6-40	 Toppled landscape statuary (photo by Quattrocchi Kwok 

Architects). 

6.3.2 Napa Education Center and District Auditorium, Napa 

This building was constructed in 1922 as the Napa High School prior to the 

Field Act, and served that purpose until 1976, when the high school was 

moved to a new facility and the building was converted to administrative 

uses. The auditorium continues to be used for local school productions. The 

building is one-story in height, with a two-story portion and was originally 

constructed with lightly reinforced concrete walls, and wood floor and roof 

systems. 

The building sustained significant damage in the 2000 Yountville 

earthquake, including near collapse of the auditorium stage walls and roof. 

The building was repaired, completely renovated, and seismically retrofitted 

using $3 million in federal repair funds, a $10 million local bond and $3 

million in operating funds. DSA approved plans for the project in 2003 and 

construction was certified as complete. The seismic retrofit included 

installation of a tube steel frame on both sides of the central hallway and 

along the exterior walls. The frames were connected by steel cross-members, 

and wood-frame connections were improved. The 80-foot high auditorium 

stage walls were taken down to the level of a damaged construction joint at 

40 feet and new reinforced concrete walls were installed above, with the 

reinforcing steel doweled into the existing walls. A new steel roof was 

installed over the stage. The auditorium side walls, which were also 

damaged in the 2000 earthquake, were wrapped in carbon fiber mesh and 

stucco was reapplied and painted to restore the building’s appearance (Figure 

6-41). 

6-26 6: Performance of School Facilities FEMA P-1024 
Figure 6-41 Interior view of auditorium walls. 

In the 2014 earthquake, the only damage was minor wall cracking around a 

beam added as part of the retrofit (Figure 6-42). One exterior fire sprinkler 

head under the front portico that broke and discharged on the outside of the 

building. 

Figure 6-42 Minor wall cracking. 

FEMA P-1024 6: Performance of School Facilities 6-27 
 

 

6.4 Vallejo City Unified School District 

There are 21 schools in the Vallejo City Unified School District, but no 

damage was reported at these facilities. 

6.5 Summary 

Schools generally performed well structurally. DSA’s enforcement of the 

Field Act has been largely responsible for the structural seismic safety of 

California’s public schools. Since 1940, no building constructed under the 

Field Act has either partially or completely collapsed, and no students have 

been killed or injured in a Field Act compliant building. However, as the 

2014 South Napa earthquake has highlighted, failures of nonstructural 

components were widespread in schools, and the lack of deaths or injuries 

caused by earthquake may be more related to the time of day of the 

earthquake, than to the seismic safety of the nonstructural components in 

schools. 

Nonstructural components in schools that were particularly vulnerable to 

damage in the South Napa earthquake include overhead lighting, particularly 

pendant fixtures, and classroom furnishings. Despite the fact that damage to 

pendant light fixtures in schools has been documented in virtually every 

damaging earthquake since 1952, even recently installed pendant fixtures 

were damaged in many schools. Eleven of the 31 schools in Napa reported 

damage to pendant fixtures, which often fell across student desks and tables. 

Classroom furnishings, which are generally not regulated by code, also pose 

a threat to students and staff. Unrestrained bookcases, storage units, file 

cabinets, lockers, and similar components overturned in the earthquake, often 

striking tables and desks. Had school been in session during the earthquake, 

these items would have posed a serious risk to students and staff. In some 

cases, overturned furnishings blocked paths of egress. At least three public 

schools experienced potentially life threatening damage to classroom 

furnishings. 

Unrestrained equipment and piping were also damaged in the earthquake, but 

do not pose a direct threat to student safety since these components were 

generally not in areas accessible to the public. 

6.6 Recommendations 

The performance of school buildings and nonstructural components in the 

South Napa earthquake suggests several areas for possible improvement and 

further study, including: 

6-28 6: Performance of School Facilities FEMA P-1024 
	 

	 

	 

	 

	 

	 

	 

	 

	 

	 

1.	 There is a need to develop reliable means of installing pendant lighting 

fixtures that will remain in place and not pose a falling hazard during an 

earthquake. Many of the newer installations of these fixtures 

experienced failures, suggesting that the current methods of design are 

inadequate. Shake table testing is recommended to demonstrate seismic 

reliability. 

2.	 Large, heavy furniture items are constantly being installed in and moved 

around classrooms, and most are outside the scope of the building code. 

Proper anchorage and bracing of these items are critical to occupant 

safety. Classrooms should be examined on a regular basis to ensure that 

furnishings and contents do not pose a serious seismic threat. An annual 

inspection of nonstructural components is recommended at the beginning 

of each school year. The inspection, or the mitigation measures 

identified as a result of such inspection, could be linked to the annual 

ShakeOut earthquake safety awareness program (www.ShakeOut.org) 

that takes place every October, since most schools now participate in this 

program. These nonstructural safety inspections could involve the 

students, staff, and faculty. 

3.	 The consequences of building drift on the functionality of doors should 

be studied. Although all exit doors operated following the South Napa 

earthquake, binding of some doors suggest that in a stronger earthquake, 

some egress routes could be compromised as a result of building 

movement. 

4.	 Guidelines for the installation of rooftop piping and conduit should be 

developed. The building code does not explicitly address this issue and 

simple construction measures could avoid costly earthquake repairs. 

5.	 Nonstructural damage in both public and non-public schools was 

potentially life threatening. All schools, not only public schools, should 

implement measures to enhance seismic safety. 

FEMA P-1024 6: Performance of School Facilities 6-29 

Chapter 7 

Performance of Residential 

Construction 

7.1 Introduction 

Homes make up one of the most important components of a community’s 

building stock. During the South Napa Earthquake, which struck at 3:20 in 

the morning, most residents were asleep in their homes. 

The downtown Napa study area, as defined by the 1,000 foot radius around 

Station N016, does not include any residential construction. In order to 

understand the performance of this important building type, additional 

neighborhoods were visited on September 18, 2014, approximately one 

month after the earthquake. In particular, homes in the Browns Valley 

neighborhood, located to the west of downtown Napa, were included based 

on their proximity to the fault rupture (Figure 7-1). Other homes were 

selected for investigation based on postearthquake safety evaluation data that 

indicated significant failures. 

The homes investigated were generally one- and two-story, single-family 

homes or duplexes and were constructed between 1900 and 1965. All homes 

investigated were wood-framed (designated as W1 on survey forms). The 

performance of manufactured homes is covered in Chapter 8 of this report. 

Larger apartment buildings were not studied. 

In lieu of the more rigorous procedure used to survey each of the buildings in 

the downtown area, residential buildings were examined with a combination 

of drive-by surveys, exterior inspections, and when possible, exterior and 

interior inspections. Information about building performance, as well as the 

earthquake and postearthquake experiences of the occupants, were obtained 

in interviews with occupants and construction crews. 

FEMA P-1024 7: Performance of Residential Construction 7-1 
 

 

Figure 7-1 Location of Browns Valley neighborhood relative to downtown Napa. 

7.2 Selected Observations 

The following selected observations summarize performance of residential 

structures. 

7.2.1 Browns Valley House No. 1 

This one-story, single-family residence is located in the Browns Valley 

neighborhood, and was built circa 1960 on a slab-on-grade. The building 

was posted UNSAFE at the time of the field investigation. Accordingly, the 

inspection was limited to exterior only. This house was co-located with the 

surface feature of the fault rupture. The rupture can be followed from the 

asphalt on the street (Figure 7-2), to the driveway leading up to the garage 

(Figure 7-3), and around the garage (Figure 7-4). The crack running up the 

middle of the driveway is presumed to continue through the house. A fallen 

brick chimney (Figure 7-5) was also observed. This house is located 

immediately to the south of Browns Valley House No. 2. 

7-2 7: Residential Construction FEMA P-1024 
Figure 7-2 Surface feature of fault rupture observed on street. 

Figure 7-3 Crack running through the street and up the driveway. 

FEMA P-1024 7: Performance of Residential Construction 7-3 
 
 

Figure 7-4 Crack continuing around the base of structure. 

Figure 7-5 Brick chimney collapse on to the roof. 

7-4 7: Residential Construction FEMA P-1024
 
7.2.2 Browns Valley House No. 2 

This one-story, single-family residence located in the Browns Valley 

neighborhood was built circa 1960 and is located directly north of Browns 

Valley House No. 1. The residence was posted UNSAFE following the 

earthquake, but the homeowner hired an engineer to inspect the home, and 

the building was reposted as RESTRICTED USE five days after the 

earthquake. At the time of the site visit, the homeowner was conducting 

repair work himself with help of family members and friends. 

Owners were available on site, and both exterior and interior inspections 

were performed. It was reported that the brick chimney collapsed, and was 

demolished prior to the site visit. Cracks running from the south end of the 

property (Figure 7-6), i.e., adjoining to Browns Valley House No. 1, through 

the house (Figure 7-7) to the front of the house (Figure 7-8) and street 

(Figure 7-9) were observed. Inside the house, large cracks (Figure 7-7) and 

buckled floors were observed. The water heater, which had been seismically 

braced, was undamaged. Rooftop solar panels were also undamaged. 

Figure 7-6 Cracks in the pavement of the backyard and damage to stucco 

wall. 

FEMA P-1024 7: Performance of Residential Construction 7-5 
 

Figure 7-7 Ceiling crack. 

Figure 7-8 Damage caused due to differential movement of floor slabs in 

garage and driveway pavement. 

7-6 7: Residential Construction FEMA P-1024 
Figure 7-9 Surface rupture observed on street. 

7.2.3 Browns Valley House No. 3 

This L-shaped, one-story, single-family residence was built circa 1965. An 

exterior inspection was performed. The residence was posted UNSAFE 

following the earthquake. The brick chimney collapsed, and was demolished 

prior to the site visit. Fault rupture caused the building to twist. Damage 

was concentrated at the reentrant corner by the main door, buckling the 

floors. At the time of the site visit, the building was being professionally 

repaired, and had been lifted off the concrete perimeter wall (Figures 7-10 

and 7-11). The contractor was interviewed on site and stated that the plan 

was to completely remove the existing perimeter foundation and interior 

piers and replace with a similar foundation system but one using better 

concrete with deeper embedment lengths. This retrofit is considered far 

superior to other “patch and paint” foundation repairs observed at other sites. 

FEMA P-1024 7: Performance of Residential Construction 7-7 
 

Figure 7-10 Photo showing demolished perimeter foundation and cracks in 

pavement. 

Figure 7-11 Structure raised for foundation repair. 

7-8 7: Residential Construction FEMA P-1024 
7.2.4 Napa House No. 1 

This one-story, duplex residence was built circa 1910. An exterior inspection 

was performed. The residence was posted UNSAFE following the 

earthquake. The brick chimney collapsed. The cripple wall supporting the 

building, which was approximately 5 feet tall, collapsed (Figure 7-12), 

causing the house to fall into the adjoining property (Figure 7-13). As a 

result of the cripple wall failure, the side porch roof collapsed (Figure 7-14). 

Figure 7-12 Home with collapsed cripple wall. 

Figure 7-13 Building fell into adjoining property. 

FEMA P-1024 7: Performance of Residential Construction 7-9 
Figure 7-14 Failure of porch due to cripple wall collapse . 

7.2.5 Napa House No. 2 

This one-story, single-family home was built circa 1910. An exterior 

inspection was performed. The residence was posted UNSAFE following the 

failure of the approximately five foot tall cripple wall (Figure 7-15). The 

house shifted laterally but did not collapse (Figure 7-16). 

Figure 7-15 Temporary lateral bracing at cripple wall. 

7-10 7: Residential Construction FEMA P-1024 
Figure 7-16 House shifted lateral at damaged cripple wall. 

7.2.6 Napa House No. 3 

This one-story, duplex residence was built circa 1925. An exterior inspection 

was performed. The residence was posted UNSAFE following the 

earthquake after the 3 foot tall cripple wall supporting the building collapsed 

(Figure 7-17). As a result of the cripple wall failure, the front porch roof 

collapsed (Figure 7-18). 

Figure 7-17 Collapsed cripple wall. 

FEMA P-1024 7: Performance of Residential Construction 7-11 
Figure 7-18 Failure of porch due to cripple wall collapse. 

7.2.7 Napa House No. 4 

This one-story, single-family residence was built circa 1900 (white building 

on the right of photo in Figure 7-19). An exterior investigation was 

performed. The house was initially posted INSPECTED following the 

earthquake, but was subsequently posted UNSAFE due to the imminent 

hazard posed by the adjacent residence, which had suffered a cripple wall 

failure and severe racking. 

Figure 7-19 Undamaged residence on the right was posted UNSAFE due to 

risk posed by damaged residence on the left. 

7-12 7: Residential Construction FEMA P-1024 
7.3 Residential Flood Retrofits 

A significant portion of the City of Napa lies in the regulatory floodplain of 

the Napa River and its tributaries. Much of the older residential construction 

took place before the floodplain was mapped under the National Flood 

Insurance Program (NFIP), which was established by Congress in 1968 to 

make flood insurance available within participating communities in exchange 

for the adoption of floodplain management ordinances. The Program is 

managed by FEMA and is intended to reduce future flood risk by requiring 

new construction and substantially damaged or improved existing 

construction to be elevated above the Base Flood Elevation (BFE). FEMA 

also operates several mitigation grant programs that can include covering the 

cost of elevating existing buildings above the BFE. Approximately 100 

homes in Napa have been elevated above the BFE under these programs. 

Following the South Napa earthquake, FEMA conducted a survey of these 

homes and determined that all but one had been inspected by the City and 

were posted as INSPECTED. Most of the homes appeared to have been 

elevated on properly braced cripple walls. One home had been posted as 

RESTRICTED USE due to a damaged masonry chimney that was not part of 

the elevation work. Several duplex homes inspected had been elevated a 

full-story height (Figure 7-20) on properly braced wood cripple walls (Figure 

7-21) and were found to have sustained no appreciable damage. 

Figure 7-20 Elevated duplex homes. 

FEMA P-1024 7: Performance of Residential Construction 7-13 
Figure 7-21 Braced wood cripple walls on the first story of elevated duplex 

homes. The height of the electrical outlets indicated the Base 

Flood Elevation. 

7.4 Summary 

The overwhelming majority of residences affected by the South Napa 

earthquake suffered little damage. The good overall performance of singlefamily residences is in keeping with the trends noted in other areas subject to 

moderate earthquakes; light-frame residential construction generally 

performs well, provided that known hazardous conditions are either not 

present or mitigated. 

Damage to residential construction was concentrated heavily on two key 

deficiencies: unbraced chimneys and unbraced cripple walls. The following 

were also noted on damage descriptions in the database: fire, damaged gas 

lines, façade damage, and carport collapses. 

7.4.1 Masonry Chimneys 

Unreinforced masonry chimneys performed poorly with many observed 

failures in the form of significant damage (Figure 7-22) or collapse (Figures 

7-23 and 7-24). In many cases, chimneys fell out onto exterior areas, 

endangering adjacent homes, passersby on sidewalks, and parked cars. In 

other cases, chimneys fell into homes, endangering occupants. In one 

instance, a teenage boy who was asleep in the living room, was struck and 

injured by falling bricks from a collapsed fireplace (Figure 7-25). This was 

7-14 7: Residential Construction FEMA P-1024 
one of the most serious injuries caused by the earthquake. It was reported 

that some reinforced masonry chimneys also failed, likely due to insufficient 

reinforcement. Lightweight metal flue chimneys performed much better and 

caused no injuries. The City of Napa had issued a construction information 

handout Retro Fitting Masonry Fireplace with Factory Built Metal Chimney 

(City of Napa, 2000), but the guidance was not readily implemented. In 

response to the damage sustained to masonry chimneys in the 2014 South 

Napa earthquake, FEMA funded the development of a Recovery Advisory on 

Repair of Earthquake-Damaged Masonry Fireplace Chimneys. This 

Recovery Advisory is provided in its entirety in Appendix B. 

Figure 7-22 Dislodged unreinforced masonry chimney (photo from Janiele 

Maffei). 

FEMA P-1024 7: Performance of Residential Construction 7-15 
Figure 7-23 Photo of damaged chimney (photo from Janiele Maffei) 

Figure 7-24 Photo of chimney laying on front yard of home (photo from 

Janiele Maffei). 

7-16 7: Residential Construction FEMA P-1024 
 

 

Figure 7-25 Photo of interior chimney collapse (photo from Janiele Maffei). 

7.4.2 Unbraced Cripple Wall Foundations 

Due to flood risk, many older homes in Napa have tall cripple walls, 

sometimes as much as one-story tall. In the earthquake, many homes with 

tall, unbraced cripple walls sustained large lateral displacements or collapse 

of the crawl space. Napa House No. 1 fell almost 5 feet and moved laterally 

an equivalent amount. Browns Valley House No. 2 was constructed with 

much shorter, although also unbraced, cripple walls and sustained lateral 

movement of a few inches. Some cripple wall retrofit successes, in which 

tall, braced cripple walls performed well were also reported, including homes 

that had been elevated under FEMA’s mitigation grant programs to address 

flood risk. 

The earthquake highlighted the possibility that residents could find their 

homes unavailable after an earthquake due to damage in adjacent buildings. 

Napa House No. 4 performed well and was initially posted INSPECTED, 

allowing the residents to return home. However, its proximity to the poorly 

performing home next door resulted in Napa House No. 4 being posted 

UNSAFE, forcing the residents out. 

FEMA P-1024 7: Performance of Residential Construction 7-17 
The 2012 edition of the International Existing Building Code (ICC, 2012b) 

presents retrofit provisions for cripple walls shorter than four feet; however, 

no guidance is provided for taller cripple walls. In response to the damage 

sustained to tall cripple walls in the 2014 South Napa earthquake, FEMA 

funded the development of a Recovery Advisory on Earthquake 

Strengthening of Cripple Walls in Wood-Frame Dwellings. A summary of 

the Recovery Advisory is provided in Appendix B. 

7.4.3 Fault Rupture and Afterslip 

The damage to Browns Valley House No. 2 highlights the risks of fault 

rupture. The home, which did not have an unbraced cripple wall, would have 

been expected to perform well in an earthquake. However, it was not able to 

withstand the fault rupture that traced directly through the house footprint, 

and damage (although not collapse) was experienced and occupants had to 

evacuate. The issue of afterslip is covered in Chapter 2; its greatest impact 

was to residential structures in the Browns Valley neighborhood. 

7.5 Recommendations 

Several areas for further study and possible improvement include: 

1.	 Outreach to the community is needed to encourage mitigation of two 

significant hazards in residential construction: unreinforced masonry 

chimneys and tall unbraced cripple walls. FEMA recently contracted to 

develop two Recovery Advisories: The first recommending best practices 

for reconstruction of earthquake-damaged masonry chimneys using lightweight metal flue chimneys, and the second recommending best practices 

for seismically retrofitting cripple wall foundations in one- and twofamily dwellings to minimize risk of damage in future earthquakes. The 

entirety of FEMA DR-4193-RA1, Repair of Earthquake-Damaged 

Masonry Fireplace Chimneys, is provided in Appendix B. A summary 

of the Recovery Advisory on cripple walls is also provided in Appendix 

B. 

2.	 The most effective measure for reducing the hazards posed by fault 

rupture is the implementation of a land use regulation that limits building 

in areas at risk for surface faulting. However, since this event took place 

in an already established neighborhood, using foundation designs that are 

more capable of accommodating ground movement may be useful in 

protecting housing in some locations. As detailed in Chapter 2, for areas 

where afterslip potential is high enough that it could impact a 

conventional foundation, the best way to mitigate this hazard would be to 

replace the existing foundation with a reinforced concrete mat or raft slab 

7-18	 7: Residential Construction FEMA P-1024 
foundation, which has enough reinforcing steel and high-strength 

concrete to support itself even if the ground is still slipping beneath. 

Also, measures to protect gas lines and other vulnerable piping from 

damage caused by ground movement should be developed. However, 

given that most foundation repairs have already been implemented and 

the high cost of replacing a building foundation with a new system, this 

mitigation measure is likely not cost effective for existing buildings. It 

should, however, be considered for any new construction within the 

moderate hazard area. 

FEMA P-1024 7: Performance of Residential Construction 7-19 

Chapter 8 

Performance of Manufactured 

Housing 

8.1 Introduction 

In the August 24, 2014 South Napa earthquake, significant damage was 

observed to manufactured homes (also called mobile homes) located in 

northwest Napa, specifically due to fire following the earthquake. This 

chapter provides an overview of manufactured home performance. 

Three visits were made to survey Napa mobile home parks (MHPs) between 

September 28 and October 18, 2014, visiting a total of eleven MHPs. 

Observations of home support systems were limited to homes where 

surrounding skirts had been fully or partially removed, either for inspection 

(by others) or because reinstallation or re-leveling was required; as a result, 

observations primarily focus on homes that experienced damage. Because 

these visits occurred several weeks after the August 24, 2014 earthquake, it is 

expected that some conditions had changed by the time of the visits. In 

addition to information gathered from the project team’s field investigations, 

State of California Department of Housing and Community Development 

(HCD) provided data summarizing its inspections following the earthquake. 

8.2 Manufactured Homes 

Manufactured homes are built in factories using light-frame construction on 

top of integral steel chassis beams, such that they can be transported to the 

home site and installed. The homes are typically built in standard floor 

sections with common widths of 12 and 14 feet and lengths between 40 and 

60 feet. Each floor section is supported by two longitudinal chassis beams 

that form the primary floor structure; when installed on a home site, support 

is provided along these chassis beams. Homes typically include either one 

single unit (single-wide home) or two units, fabricated to be joined together 

to form an approximately 24-foot wide home (double-wide home). In 

addition, there are two primary categories of homes: (1) older homes 

primarily clad in aluminum and with aluminum panel skirts (Figure 8-1); and 

(2) newer homes with cement board (fiber-cement) or wood panel siding 

with similarly clad skirts (Figure 8-2). The skirts in the older type homes slip 

into continuous tracks and the siding skirts in newer homes are fastened to 

FEMA P-1024 8: Performance of Manufactured Housing 8-1 
continuous wood plates sitting on the ground around the home perimeter. 

The newer home type is believed to have become common in homes 

manufactured in the 1980s and later. Both older and newer homes occur in 

both single-wide and double-wide configurations. 

Figure 8-1 Typical older (single-wide) home with add-on porch and 

carport. Home is clad in aluminum siding and aluminum 

skirting. 

Figure 8-2 Typical newer (double-wide) home clad in wood panel siding 

with a matching siding skirt. 

8-2 8: Performance of Manufactured Housing FEMA P-1024 
 

 

	 

	 

	 

	 

When installed on the home site, the floor of the home generally sits between 

two and three feet above surrounding grade. Installation of the manufactured 

home on the home site involves a gravity support system and may also 

involve systems for wind or seismic resistance, further discussed in Section 

8.3. Manufactured homes are commonly surrounded by extensive 

prefabricated or site-built porches, carports, and other add-on structures, as 

seen in Figures 8-1 and 8-2. Porches are often self-supporting while carports 

are often partially supported by the home. 

Manufactured homes have experienced damage in past earthquakes (EERI, 

1996; EERI, 2005; State of California, 1992). The damage to manufactured 

homes in this and past earthquakes has almost exclusively been associated 

with the support system, rather than the homes themselves. 

8.3 Regulatory Background 

Building code regulations for manufactured homes differ from site-built 

homes. New manufactured homes currently fall under the jurisdiction of the 

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

regulations for home installation in the state of California fall under the code 

adoption authority of the State of California Department of Housing and 

Community Development (HCD). Enforcement of installation requirements 

is permitted to be under the jurisdiction of the local building department (city 

or county); where the local building department chooses not to take 

jurisdiction, enforcement authority remains with HCD. As a result, some of 

the MHPs in Napa fell under HCD jurisdiction and were included in their 

postearthquake inspections, while others did not. 

The regulations for construction of manufactured homes have evolved over 

the years: 

	 Prior to September 1, 1958, there were no construction standards for 

manufactured housing. 

	 Between 1958 and 1971, standards were applied to electrical, 

mechanical, and plumbing systems only. 

	 Between 1971 and 1976, California construction standards were applied 

to construction of homes. 

	 Starting June 1976, HUD standards became applicable to the homes. 

Similarly, oversight of home installation has evolved over the years, with 

permits for and inspections of home installations starting in 1974. 

FEMA P-1024 8: Performance of Manufactured Housing 8-3 
Since September 1994, the California Code of Regulations (CCR) (State of 

California, 1994) has required that a wind tiedown system be installed on 

newly installed or relocated manufactured homes in the state of California. 

This requirement comes from California SB 750, passed in July 1994 

following the Northridge earthquake as a urgency statute “...to ensure that as 

many manufactured homes as possible are protected at the earliest possible 

time from sudden devastation by earthquakes.” The tiedown system can 

either consist of a tiedown assembly chosen from a list approved by HCD, or 

an engineered system. Either system is required to resist a wind load of 15 

pounds per square foot (or the wind pressure specified on the home label, 

where higher), applied to the projected area of the home in each horizontal 

direction. These requirements are found in California Code of Regulations, 

Title 25, Sections 1320 and 1336, Chapter 2, Article 7. The term “ETS” is 

often applied to tiedown systems, whether engineered or pre-approved. 

Homes installed prior to September 1994 were not required to have a 

tiedown or ETS at the time of installation (with the exception of limited highwind locations for which wind bracing has been regulated since 1974); these 

homes are not required to meet this requirement retroactively, except under 

two circumstances: (1) the home is relocated to a new lot; and (2) the home 

requires reinstallation due to damage caused by wind or seismic forces, and 

federal funds are available for the additional installation costs (Section 

18613.4(e) of California Health and Safety Code (State of California, 2014)). 

Although relocation of homes does sometime occur, it is uncommon. 

California Code of Regulations Title 25, Chapter 2, Article 7.5 contains 

provisions for earthquake-resistant bracing systems (ERBS). These 

provisions do not require that ERBSs be installed, but do provide minimum 

requirements for them where they are installed: it is required that they be 

designed in accordance with the 1982 Uniform Building Code (ICBO, 1982), 

and it is required that they limit downward vertical movement of the home to 

not more than two inches. Although ERBSs existed prior to the early 1980s, 

approval of ERBSs by HCD started in January 1981, and inspections of 

ERBS installations started in 1990. ERBSs are most often installed as a 

voluntary retrofit measure, and almost exclusively to homes installed prior to 

September 1994 that do not have tiedown systems. A modest number of 

ERBSs were observed to be installed in the surveyed MHPs. 

It is understood that an ETS, though designed for wind, will provide some 

(undetermined) level of earthquake resistance; as previously discussed, SB 

750 clearly intended to provide increased earthquake performance. 

Similarly, an ERBS, designed considering earthquake resistance, will provide 

some (also undetermined) level of wind resistance. 

8-4 8: Performance of Manufactured Housing FEMA P-1024 
Because the requirement for tiedown systems (ETS) has only been in effect 

since 1994 and because only a limited number of ERBSs have been 

voluntarily installed, there remains a significant population of existing 

manufactured homes in California that do not have ETS or ERBS. Further, 

because the regulations for ETS and ERBS have evolved over the years, the 

systems observed following the South Napa earthquake may or may not have 

been approved and inspected as would currently be required. Their 

performance in the earthquake should be viewed with these limitations in 

mind. 

8.4 Gravity and Seismic Support Systems 

Gravity support of manufactured homes is primarily provided by two lines of 

support piers for each floor section, one along each longitudinal chassis 

beam, located a few feet inboard of the floor section edge. This results in 

two lines of support for single-wide homes and four lines of support for 

double-wide homes. The gravity support piers observed in the MHPs visited 

were almost exclusively stacked concrete masonry units (Figure 8-3). This is 

notably different from homes observed in the 2003 San Simeon earthquake, 

where steel gravity piers were prevalent (EERI, 2005). The masonry units 

are hollow nominal 8”x8”x16”, dry-stacked, and often interspersed with 2x 

wood blocks. The masonry piers sit on either wood or ABS (plastic) mats 

supported on the ground surface (on soil or on a concrete pad). Wood 

wedges are provided at the top of the stack in opposing pairs, used to adjust 

the support height when the floor is leveled; there were no nails or other 

fasteners observed connecting the wedges to the supporting wood block. The 

long (16 inch) masonry block dimension is generally oriented in the 

transverse direction of the home to allow for the wood wedges to engage the 

chassis beam. The spacing of gravity piers installed prior to the earthquake 

appeared to range between eight and ten feet on-center along each chassis 

beam; the spacing for reinstallations observed following the earthquake was 

typically reduced to six feet on center. Supplemental piers were observed to 

occasionally be provided at the perimeter of the homes near doors, and at the 

unit interface in double-wide homes. Only a small percentage of the 

observed homes had been supported on steel (Figure 8-4) or precast concrete 

gravity piers. It appeared that many of the homes that had precast concrete 

gravity piers prior to the earthquake were in the process of replacing them 

with dry-stacked masonry piers. Similar to the masonry piers, the steel and 

precast concrete piers, when used, were also commonly seated on wood or 

ABS mats sitting on the ground surface. 

FEMA P-1024 8: Performance of Manufactured Housing 8-5 
Figure 8-3 Typical dry-stacked masonry gravity piers, with interspersed 

wood blocks. 

Figure 8-4 Steel gravity piers interspersed with masonry piers during home 

reinstallation. 

Where earthquake and wind bracing is provided for manufactured homes, the 

two predominant systems are wind tiedowns (ETS) and ERBS. Although 

perimeter concrete or masonry foundations of the type used for site-built 

8-6 8: Performance of Manufactured Housing FEMA P-1024 
homes are permitted to be used (supplemented with gravity support along the 

chassis), none were observed in the surveyed Napa manufactured homes. 

Early ETS used a set of steel straps looped over the chassis beams and 

attached to helical soil anchors. Figures 8-5 and 8-6 show such a system, 

with the strap cut to allow relocation of the home. HCD representatives 

indicated that this type of ETS is seldom used anymore, replaced by other 

approved systems. Straps were only seen in two of the homes where support 

systems were observed. 

Figure 8-5 ETS strap connected to a home chassis beam, cut to allow home 

to be relocated. 

Figure 8-6 ETS ground anchor. The ground anchor bracket is typically 

attached to a helical soil anchor, embedded in the soil. 

FEMA P-1024 8: Performance of Manufactured Housing 8-7 
It was observed that one home had in place a steel support pier with rods 

anchoring the pier to the ground (similar to the one shown in Figure 8-7). 

This system was identified by HCD as an ETS. The approximately 1/2-inch 

steel anchor rods at each corner of the pier base are identified in 

manufacturer online literature to extend about 15 inches into the ground. The 

observed home did not appear to have moved, and was reported by the 

residents to have performed well. This same system was observed in several 

postearthquake reinstallations. 

Figure 8-7 Steel pier system with anchor rods to the ground. 

Several homes identified by HCD to have ETS at the time of the earthquake 

were observed to have “cantilevered” (individual) steel piers in addition to 

the masonry gravity piers. Each of these homes appeared to have between 

four and eight of these steel piers installed. Figure 8-8 shows these piers, 

removed during reinstallation of homes that had moved considerably during 

the earthquake. 

Many of these “cantilevered” piers did not have holes in the pier base that 

would allow installation of fasteners between the pier base and the 

supporting wood board, nor was the wood board anchored to or embedded in 

the supporting soil, thus some of these “cantilevered” steel piers appeared to 

have slid or toppled over, allowing the home to drop. Similar “cantilevered” 

piers being installed new in postearthquake reinstallations were observed to 

have screw connections between the pier base and the supporting wood 

boards (Figure 8-9), but continued to lack connection of the wood board to 

the supporting soils. 

8-8 8: Performance of Manufactured Housing FEMA P-1024 
Figure 8-8 ETS removed from homes during reinstallation. These 

“cantilevered” piers had no allowance for anchorage to the 

supporting wood boards. 

Figure 8-9 New “cantilevered” pier, anchored to supporting plywood 

panels. 

In another MHP, homes with these “cantilevered” steel piers were not 

identified by HCD to have either ETS or ERBS HCD noted that the devices 

observed following the earthquake may or may not have been designed or 

FEMA P-1024 8: Performance of Manufactured Housing 8-9 
approved as an ETS or ERBS; further, many systems utilize the same 

supports in different numbers and configurations making the exact 

determination of system (ETS, ERBS, or other) extremely difficult to an 

untrained observer. Figure 8-10 shows another type of “cantilevered” pier, 

also without anchorage to the ground, which rocked and toppled over, 

allowing the home to drop. 

Figure 8-10 “Cantilevered” steel pier on home requiring reinstallation. 

A number of homes were found to have identifiable ERBS at the time of the 

earthquake. These are designated as “diagonally braced” ERBS in this 

report, because they often had diagonal bracing members that engage more 

than one chassis beam. Dates of installation of ERBS were in some cases 

identified by residents to be the early 1980s, while others were more recently 

installed. Figure 8-11 illustrates some of these systems. These systems were 

typically seated on wood plates sitting on the ground, similar to the gravity 

piers and “cantilevered” pier systems. Unlike the “cantilevered” steel piers 

that were vulnerable to rolling over, these “diagonally braced” ERBS were 

observed to stay upright while the homes slid horizontally from a few inches 

to more than a foot. The “diagonally braced” ERBS appeared to be much 

more inherently stable under earthquake loading than the “cantilevered” 

piers. 

8-10 8: Performance of Manufactured Housing FEMA P-1024 
	 

	 

	 

Figure 8-11 “Diagonally braced” ERBS on homes requiring reinstallation. 

As previously mentioned, damage to manufactured homes was observed to 

be primarily to the home’s support system rather than the home itself. Very 

few homes were observed to have suffered extensive damage such that they 

could not be reinstalled. The following damage and resulting consequences 

were observed: 

	 Homes sustained damage to the skirts from rocking and shifting (Figure 

8-12). This predominantly affected older homes with aluminum skirts, 

but occasionally affected wood or cement board siding skirts also. This 

damage requires repair, but is not structural and does not affect continued 

occupancy of the home. 

	 Homes sustained disruption to support gravity piers without significant 

sliding or toppling movement. This was identified by HCD as requiring 

reinstallation, even when the damage was to a few piers and the scope of 

repair required was small. 

	 Homes toppled off of support piers, as shown in Figures 8-13 and 8-14. 

Most often the home itself was not damaged; however, occasionally steel 

support piers punched through the floor as the home dropped. When the 

home falls off the supports, the outward swinging doors are often 

blocked, as occurred in the home shown in Figure 8-15. This damage 

can impede safe egress of occupants, requires reinstallation of the home, 

including lifting and placement back onto supports, and repair or 

replacement of damaged components. In addition, reinstallation of any 

FEMA P-1024 8: Performance of Manufactured Housing 8-11 
disrupted utility hook-ups is also required, and minor to major damage to 

surrounding add-on structures, such as decks and carports, is common. 

Figure 8-16 shows an example of a large extent of damage to an attached 

porch. Homes that drop are most often posted RESTRICTED USE so 

residents can retrieve belongings, but not continue to occupy the home. 

Figure 8-12 Damaged skirt on older home. 

Figure 8-13 Home dropped from masonry gravity pier supports. 

8-12 8: Performance of Manufactured Housing FEMA P-1024 
Figure 8-14 Close-up of toppled masonry gravity pier. 

Figure 8-15 This door was blocked when the home dropped off of the 

gravity supports and had to be broken open by fire fighters. 

FEMA P-1024 8: Performance of Manufactured Housing 8-13 
	 

	 

	 

Figure 8-16 Add-on porch structure severely damaged by the earthquake. 

	 Homes sustained minor to significant sliding. Homes that slid 

sometimes retained enough vertical support, primarily through a 

“diagonally braced” ERBS, so that the floors did not drop. Similar to 

homes that toppled off of their supports, these homes require 

reinstallation, repair of hookups, and repair of attached structures. These 

homes were observed to often be posted INSPECTED, allowing 

continued occupancy, even when the ERBS was the only vertical support 

remaining. 

	 In a few cases, fires occurred following the earthquake. Common causes 

in past earthquakes have included damage to gas lines or poorly braced 

water heaters. Although most of the homes were observed to have 

flexible utility hook-ups allowing the home to move relative to the hookup without causing fire, if the home moves far enough, utility lines can 

still potentially be ruptured. 

	 In the few instances where damage to the home superstructure was 

observed, it included cracking of wall finishes around windows, as 

commonly occurs with site-built structures. 

8-14 8: Performance of Manufactured Housing FEMA P-1024 
8.5 Overall Mobile Home Park Observations 

In the eleven parks surveyed, the majority of the homes were installed prior 

to ETS being required. Bracing systems (ERBS or ETS) were observed to 

have been installed on a limited number of the homes. This is likely due to 

those homes being more recently installed or due to owners choosing to 

voluntarily install bracing. 

Five MHPs visited in mid-town Napa (Napa Valley Manor, Rexford Mobile 

Home Estates, Valley Mobile Home Park, Pueblo Trailer Park, and Miller’s 

Senior Park) included a total of approximately 345 homes. Of these, only 

one home was readily observed to require reinstallation. The owner reported 

that, although the home did not fall off of its supports, it did shift several 

inches. The homes in these MHPs were not observed to have readily 

apparent differences in home type, age, or construction from the other parks 

that had much higher incidents of damage. This relatively small amount of 

damage may be attributed in part to these homes being located at a greater 

distance from the fault rupture. 

Six MHPs visited in northwest of Napa are shown in Figure 8-17. Four of 

the MHPs are located adjacent to each other, arranged in an approximately 

north-south string along Highway 29, with the first being approximately one 

block north of Fire Station No. 3 (12.3 km north of the epicenter and the 

location of a ground motion recording station). A fifth park is in the same 

north-south line, but spaced a block further north of the first four. A sixth 

park is located to the east across Highway 29. 

Significantly more damage was observed at the six MHPs northwest of Napa 

than the MHPs in mid-town in spite of the fact that the mix of ages and types 

of homes was judged to be similar among the two groups of MHPs. While 

the ground motion records at Fire Station No. 3 show lower peak ground 

acceleration (PGA) than the records at Station N016 at Main Street, the peak 

ground displacement reported at Fire Station No. 3 is more than twice that 

reported at Station N016 (see Figures 2-6 and 2-7 in Chapter 2). Differences 

in the ground motions are likely to have contributed to the difference in 

performance. Spectral acceleration plots based on the two ground motion 

records are also distinctly different; however, the spectral accelerations are 

difficult to relate to manufactured homes because there is no single 

characteristic period of vibration during shaking once the home slides or 

rocks. 

A summary of homes in MHP 1 through 5 requiring reinstallation is provided 

in Table 8-1, based on field inspections by HCD. MHP 6 is not under the 

FEMA P-1024 8: Performance of Manufactured Housing 8-15 
	 

jurisdiction of HCD, so data were not available. The data in the table must 

be qualified considering first that a home designated by HCD as requiring 

Figure 8-17	 Map of six MHPs north of Napa Fire Station No. 3 (image 

source: Google Maps). 

reinstallation may have had little permanent movement and only a few of the 

gravity piers disrupted, and second, although homes were identified by HCD 

as having ETS or ERBS, these systems may or may not have been approved 

or inspected at the time of installation, and so may not be representative of 

current approval and inspection requirements. Table 8-1 presents that 19% 

of all homes, 21% of homes with ETS, and 27% of homes with ERBS 

required reinstallation after the earthquake. In terms of this performance 

aspect, the performance of homes with ETS and ERBS was poorer than those 

without. 

8-16 8: Performance of Manufactured Housing FEMA P-1024 
 

 

 

8.6 Detailed Observations at Oaktree Vineyard Mobile 

Home Park 

No homes in Oaktree Vineyard MHP (MHP 1 on Figure 8-17) were reported 

by HCD to require reinstallation following the earthquake. Homes in this 

park were installed over an approximate four year period in the 1980s. The 

homes in Oaktree Vineyard MHP are unique in a number of ways: (1) all of 

the homes are of the newer type; (2) each home, in addition to a porch, has 

an attached site-built enclosed garage (Figure 8-18) instead of a carport that 

is common in other MHPs; (3) the home siding appears to have been 

installed on site and is continuous with the garage and porch siding; (4) the 

roofing appears to have been installed on site, and the roofing is continuous 

between the homes and garages. In addition, the homes are most often 

installed in pairs, as is common for two-family dwellings in residential 

developments. 

Table 8-1 Summary of HCD Field Inspection Data Showing Homes Requiring Reinstallation 

Park 

Number of 

Homes 

Homes 

Requiring 

Reinstall 

Homes with 

ETS 

Homes with 

ETS 

Requiring 

Reinstall 

Homes with 

ERBS 

Homes with 

ERBS 

Requiring 

Reinstall 

MHP 1 - Oaktree 

Vineyard 

190 0 (0%) 0 0 (0%) 0 0 (0%) 

MHP 2 - Salvador 

Mobile Estates 

147 32 (22%) 17 5 (29%) 36 7 (19%) 

MHP 3 - Newells 

Mobile City 

116 36 (31%) 5 2 (40%) 3 2 (67%) 

MHP 4 - La Siesta 

Village 

133 27 (20%) 3 0 (0%) 7 4 (57%) 

MHP 5 - Napa Valley 

MHP 

243 62 (26%) 27 4 (15%) 24 6 (25%) 

Total 829 157 (19%) 52 11 (21%) 70 19 (27%) 

Observed damage at Oaktree Vineyard MHP was limited to single-wythe 

brick masonry skirt walls (Figure 8-19). Support systems were observed for 

two homes; one had an ERBS and the other did not. Neither home appeared 

to have moved significantly. Both had damaged masonry skirt walls. 

FEMA P-1024 8: Performance of Manufactured Housing 8-17 
Figure 8-18 Oaktree Vineyard MHP typical home configuration. 

Figure 8-19 Damage to brick masonry skirt wall. 

8.7 Detailed Observations at Salvador Mobile Estates 

According to HCD records, the homes in Salvador Mobile Estates (MHP 2 in 

Figure 8-17) had the highest occurrence of ERBS and ETS installations prior 

to the earthquake. The majority of these homes were installed prior to the 

1994 requirement for ETSs. 

A limited number of homes with the “cantilevered” pier systems were 

observed, as a number of these systems had been removed during home 

8-18 8: Performance of Manufactured Housing FEMA P-1024 
 

	 

reinstallation prior to the site visits. The primary mode of behavior observed 

was rocking or sliding of the “cantilevered” piers (Figure 8-20), which were 

often not connected to the supporting wood boards. Some occurrences of the 

top of these piers punching through the home floor above were also 

observed. 

Some homes with “diagonally braced” ERBS (Figure 8-11) were reported by 

the owners to not have moved at all or only moved a few inches; however, 

multiple homes with the “diagonally braced” ERBS installed were observed 

to have slid significantly during the earthquake, but not fallen or dropped 

appreciably. Figures 8-21 and 8-22 show significant sliding in one home 

with an ERBS. The gravity piers on this home are believed to have tipped 

and been reset upright for temporary support until the home can be moved 

back to its pre-earthquake position. Table 8-2 provides information on four 

homes with “diagonally braced” ERBS for which measurements or estimates 

of sliding were made. This extent of sliding was surprising, as significant 

horizontal movement in 

Figure 8-20	 “Cantilevered” pier system that slid, adjacent to a masonry pier 

that has rolled over. 

past earthquakes had been primarily associated with homes falling off of 

supports and dropping, rather than pure sliding behavior. It is of note that 

significant sliding of the homes occurred in both transverse and longitudinal 

directions. It is also of note that the primary direction of movement was to 

the west. 

FEMA P-1024 8: Performance of Manufactured Housing 8-19 
 

Figure 8-21 Gap between front porch and home on home with ERBS that 

slid a significant distance. 

Figure 8-22 Extent of home sliding. Red arrow is initial wood board position, 

blue arrow is final position. ERBS can be observed in the 

background. 

8-20 8: Performance of Manufactured Housing FEMA P-1024 
 

 

Table 8-2 Measured or Estimated Movement of Homes with “Diagonally 

Braced” ERBS 

Home 

Transverse Sliding 

(in.) 

Longitudinal 

Sliding (in.) Dimension Source 

A negligible 18 Field measured 

B 6-8 negligible Observed damage to 

electrical hookup 

C 15 15 Field measured 

D 14 2 Estimated from photographs 

In some homes, wheels and tires that were still in place near the rear of the 

home appear to have limited the displacement at the rear of the home to 

several inches, causing the front of the home to rotate relative to the rear. 

For the homes that required reinstallation, the “diagonally braced” ERBS did 

appear to have kept the homes from dropping appreciably. 

None of the homes with “diagonally braced” ERBS were observed to have 

severely damaged their utility hookups; this appears to have been a matter of 

chance, with the homes often sliding away from rather than towards their 

hookups. 

One home in Salvador Mobile Estates was damaged by fire following the 

earthquake. The fire-damaged home did not have an ETS or ERBS. The 

home both slid and dropped off of its gravity support piers, falling into its 

utility hookup (Figure 8-23). Information provided by HCD indicates that 

the gas was turned off immediately following the earthquake and that the fire 

initiated a couple of hours later in the laundry room. Neighbors indicate that, 

because of a broken water main, water from tanker trucks were used to fight 

the fire. 

The homes requiring reinstallation in Salvador Mobile Estates were observed 

to have moved in a predominantly westerly direction, and significant 

movement was more prevalent at the west end of the park than other areas. It 

is possible that ground motion characteristics, including a pulse of ground 

displacement, contributed to this pattern. 

FEMA P-1024 8: Performance of Manufactured Housing 8-21 
Figure 8-23 Manufactured home that slid and fell onto its utility hookup. 

8.8 Detailed Observations at Napa Valley Mobile Home 

Park 

Similar to Salvador Mobile Estates, a number of homes at the Napa Valley 

MHP (MHP No. 5 in Figure 8-17) were observed to have very visible 

damage. Like in Salvador Mobile Estates, a notable number of units at the 

west end of the park were damaged and had moved, whether sliding or 

dropping, in a predominantly westerly direction (Figure 8-24). A handful of 

homes, however, were observed to be predominantly displaced in an easterly 

direction, and also experienced significant damage (Figures 8-25 and 8-26). 

It is possible that a ground displacement pulse is responsible for the damage 

in both the west and east directions. 

Napa Valley MHP had two incidents of fire following the earthquake. It is 

reported that the water main to the park broke in the earthquake, resulting in 

there not being water available to fight the fires. One fire destroyed five 

adjacent homes, and the other destroyed a single home. The causes of the 

fires are not known; however, either gas line or water heater rupture are 

thought to be likely. 

8-22 8: Performance of Manufactured Housing FEMA P-1024 
Figure 8-24 Napa Valley MHP home displaced significantly to the west. 

Figure 8-25 Napa Valley MHP home displaced significantly to the east. 

FEMA P-1024 8: Performance of Manufactured Housing 8-23 
 

Figure 8-26 Entry stairs at Napa Valley MHP home that displaced 

significantly to the east. 

8.9 Summary 

Overall the performance of the observed manufactured homes was in line 

with the intent of the seismic design provisions of recent building codes: 

protection of life safety. 

However, significant damage and disruption occurred to a notable number of 

manufactured homes, with the most severe damage being homes lost 

completely to fire. Based on available information, the damage that triggered 

reinstallations appears to have occurred approximately equally to homes with 

ETS and ERBS, as compared to those without. The ground motion 

experienced in this earthquake and the presence of some older (possibly not 

approved or inspected) ETS and ERBS may have contributed to this 

behavior. This, however, is still a surprising result and suggests that the 

ability of these systems to improve earthquake performance needs further 

evaluation. 

In California, ERBS are required by California Code of Regulations Title 25, 

Chapter 2, Article 7.5 to be designed in accordance with the 1982 Uniform 

Building Code (UBC) (ICBO, 1982). The 1982 UBC requires a complete 

load path for wind and earthquake loads, transmitting the loads to the 

supporting soils. The “diagonally braced” ERBS that were observed 

appeared to have provided adequate bracing strength and adequate 

8-24 8: Performance of Manufactured Housing FEMA P-1024 
	 

connection to the home above for the earthquake loads experienced. Further, 

the practice of bracing between the two chassis beams in the “diagonally 

braced” ERBS appeared to make the bracing inherently more robust than the 

“cantilevered” systems, and should be encouraged in future bracing systems. 

The load path for transmitting loads to the supporting soils, however, was 

observed to be missing or inadequate, and some homes were observed to 

slide significantly as a result. This portion of the load path was observed to 

be similarly missing from the new ERBS being installed following the 

earthquake. 

In California, ETS are required by California Code of Regulations Title 25, 

Chapter 2, Article 7 to be designed for 15 pounds per square foot of wind 

load applied horizontally to the home. A complete load path capable of 

resisting this wind load should also provide significant resistance to 

earthquake loads. Most observed ETS did not appear to have a complete 

load path capable of resisting this wind load. The observed systems similarly 

did not appear to be capable of providing a complete load path for earthquake 

resistance, even though the intent of SB 750 was to provide improved 

earthquake resistance. 

In addition, noteworthy differences in earthquake performance of homes 

were observed. In general, it appeared that the damage was concentrated in 

the older type of home rather than the newer homes. It is not clear what 

caused the better performance of newer homes, but this same pattern was 

observed in the 2003 San Simeon earthquake (EERI, 2005). It was observed 

that the wood siding skirts in newer homes (fastened to continuous wood 

plates sitting on the ground around the home perimeter) appeared to provide 

some contribution to vertical support, reducing rocking of the homes, and 

provide some contribution to lateral support; the skirts in the older type 

homes (which slip into continuous tracks) appeared to provide little to no 

vertical or lateral support. In addition, it was noted that the add-on structures 

of porches and garages likely contribute to better performance of some 

homes. 

8.10 Recommendations 

Based on the performance of manufactured housing in the South Napa 

earthquake the following recommendations are offered,: 

1.	 Based on damage observed following the South Napa earthquake and the 

data presented in Table 8-1, it appears that manufactured homes with 

ETS or ERBS performed no better than those lacking these systems. It is 

recommended that current design and approval criteria should be 

evaluated and potential improvements to the earthquake performance of 

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ERBS and ETS should be considered. As part of the further evaluation, 

the previously discussed qualifying factors that potentially impacted 

earthquake performance should be considered, as should basic principles 

of earthquake resistance and load path. Specific recommendations 

include: 

o	 Analysis and testing should be undertaken to better understand the 

earthquake behavior of these systems. 

o	 Verification that the criteria for ETS provides a meaningful increase 

in earthquake performance compared to unbraced homes. Since this 

system was mandated by SB 750 with the intent of providing 

improved earthquake performance, the ETS should provide better 

resistance to earthquake force and deformation demands compared to 

unbraced homes. 

o	 The performance objectives of the ERBS should be reviewed, and 

the performance of braced homes studied to determine whether the 

intended performance objective was met, and if so, whether the 

intended performance is appropriate for future installations. Based 

on this review, modifications to the requirements for these systems 

should be implemented to improve performance. This could include 

field verification that the bracing systems have been correctly 

installed. The potential for homes sliding into utility hookups and 

the resulting fire hazard should be included in these considerations. 

o	 The criteria for evaluating and approving both ETS and ERBS 

should be reviewed relative to performance objectives, and in light of 

the performance of these systems in the 2014 South Napa 

earthquake. It is recommended that the process for bracing system 

approval be reviewed relative to those of other organizations that 

provide approvals of wind and earthquake resisting systems. It is 

recommended that the testing procedures conducted for approval of 

bracing systems be reviewed to ensure that they adequately address 

performance of the complete installed system, including adequate 

resistance to local overturning and sliding of the bracing assembly. 

o	 The seismic design criteria for ERBS should be updated to 

correspond to building code editions currently adopted and enforced 

by the State of California, especially with regard to the lateral forces 

used for design. This will allow current quantification of seismic 

hazard and current thinking on seismic force-resisting systems to be 

incorporated, which should provide performance that is aligned with 

other types of structures. 

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o	 The current allowance for homes braced with ERBS to drop up to 

two inches be revisited. This drop can easily result in the blockage 

of outward swinging exit doors. The restrictions that led to this drop 

being permitted have not been applicable for 20 years. Prior to 

September 1994, positive anchorage to the home chassis beams was 

discouraged because anchorage was defined as an improvement to 

the property, triggering increases in property taxes; however, due to 

changes in state laws and regulations in 1994, the allowance for a 

two-inch drop is no longer necessary. 

o	 Impediments to anchorage of manufactured homes to the ground 

should be investigated so that solutions involving anchorage can be 

more widely used. Such impediments may include property tax 

considerations. 

o	 The complete load path for ERBS and ETS currently being installed 

should be reviewed to ensure that loads are adequately transferred 

into the home’s floor diaphragm. Many of the current systems attach 

to the bottom flange of the chassis beams only. Earthquake loading 

transverse to the home could potentially yield and severely damage 

the chassis beam. 

o	 Consideration should be given to referencing or incorporating the 

requirements of the NFPA 255, Model Manufactured Home 

Installation Standard, (NFPA, 2013) which, according to FEMA, 

provides the necessary installation criteria to meet wind and seismic 

loads. 

2.	 It is recommended that retrofit strapping of water heaters be required, 

and, if possible, funded. HCD indicates that seismic strapping of water 

heaters is only required upon sale of the home or reinstallation of the 

water heater. Water heaters without strapping remain a significant fire 

concern. 

3.	 It is recommended that the criteria for postearthquake safety assessment 

of manufactured homes be reviewed to make sure that occupant safety is 

adequately considered. It is recommended that a discussion of 

assessment criteria specific to manufactured homes be revisited in a 

future update to the assessment methodology, and that such discussion 

include representatives of HCD. It is also recommended that HCD field 

staff be trained and certified in the state’s Safety Assessment Program to 

ensure adequate safety assessments of damaged manufactured housing 

after future disasters. 

FEMA P-1024 8: Performance of Manufactured Housing 8-27 

 

 

 

 

 

 

 

 

 

 

Chapter 9
 
 

Performance of Wine Industry 

Facilities 

9.1 Introduction 

Napa Valley is home to one of the world’s premier wine-producing region, 

and has approximately 400 wine production facilities, with an estimated 300 

built since 1966. The wine industry is comprised of a diverse mix of 

wineries, ranging from larger production facilities producing millions of 

cases annually to smaller operations producing thousands of cases. 

An estimated 50 wineries were exposed to significant seismic ground 

shaking in the 2014 South Napa earthquake and sustained measurable 

damage to tanks, barrels, or buildings. In this chapter, performance of the 

wine industry facilities in the Napa Valley is examined. 

The majority of Napa Valley wineries are located north of the City of Napa, 

along Highway 29 and the Silverado Trail, located to the east of Highway 29. 

Damaged facilities were concentrated northwest of the epicenter, west of 

Highway 29, reaching approximately 10 miles north of the epicenter. 

Wineries located in within the 10 mile radius include approximately 30 

facilities along Highway 29 or west of Highway 29; most of these facilities 

were smaller or co-op (where multiple winemakers and winery labels 

produce wine using the same facility) facilities. The remainder are located 

southeast of the City of Napa near the airport along Kaiser Road. The 

facilities along Kaiser Road are generally long-term barrel storage and 

distribution facilities. 

Wineries located more than 10 miles north of the epicenter suffered only 

minor contents damage or suffered no measureable damage to wine tasting or 

production facilities. 

9.2 Winery Seismic Risk 

The earthquake risk profile of a winery is varied based on the time of year. 

The only constant in the risk profile is the seismic vulnerability of winery 

buildings. The contents are in constant motion throughout the year as the 

wine industry is an agricultural business on an annual cycle. The wine 

production process is a labor-intensive operation that requires movement and 

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processing of the wine throughout the year. The wine production operation 

is generally characterized as follows, with some variation based on the 

specific winemaking operations and facility type: 

•	 August through November: Harvest and wine grape crush season. The 

majority of stainless steel wine tanks and a significant proportion of wine 

barrels are empty at this time, ready to be filled with the new harvest. 

•	 December through March: All wine storage vessels, including tanks 

and barrels, are full of wine. The wine is aging and undergoing filtering 

and racking operations. White wines are generally stored in stainless 

steel tanks and red wines in barrels and tanks. Limited bottling 

operations occur during this time period. 

•	 March through July: Wines are moved from tanks to barrels and from 

tanks to bottling. In general, white wines may be bottled earlier than red 

wines. Accordingly, the risk exposure includes more full barrels and less 

full stainless steel tanks. Prior to the harvest in August, the barrels and 

tanks will be emptied (not all, but most) to make room for the next crush. 

The majority of content exposure is in finished, bottled goods, with tanks 

and barrels second. Smaller wineries do not have sufficient on site 

storage for bottles and case goods, thus are typically immediately 

shipped to distribution warehouses off site. 

The 2014 South Napa earthquake occurred approximately two weeks into the 

harvest and crush operation, in late August. Barrel stacks consisted of a mix 

of empty and full barrels, minimizing the total wine lost. The majority of 

stainless steel tanks were empty at the wineries in the regions of significant 

seismic ground shaking (MMI VIII or greater). Overall damage to tanks was 

minimal as empty wine tanks generally perform well in earthquakes. The 

loss of wine would have been more significant if the earthquake occurred in 

any month from December through July. 

The earthquake occurred in the middle of the night. If the earthquake 

occurred during normal operating hours, the threat to life safety would have 

been significant in the barrel rooms. There were no reported injuries or loss 

of life in wineries. 

9.2.1 Direct Loss and Business Disruption 

Direct loss of wine and damage to the production equipment varied by 

location, but was relatively low for Napa Valley as a whole. Wineries 

reported wine losses from as little as 0.5% (bottles and some barrels) to as 

high as 15% (barrel stack collapse). Wine loss due to damaged wine tanks 

was reported as minimal because most tanks were empty. 

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Business disruption was minimal. Wine tasting facilities were able to clean 

up broken bottles and displaced contents on Sunday and Monday, open for 

business on Tuesday, two days after the main shock. The impact on wine 

tasting facilities was not noteworthy. Winery production facilities were open 

and operating at nearly all wineries with the exception of Trefethen Family 

Estates, which suffered significant structural damage to the historic winery 

building that housed production and tasting operations. 

Production facility disruption was attributed to collapse of wine barrel stacks 

(Figure 9-1) and limited damage to full stainless steel wine tanks. The 

recovery efforts for the wine barrel stacks were very dangerous and time 

consuming. The piles of barrels were unstable and the threat of aftershocks 

resulted in a life safety risk to the employees engaged in the recovery 

operations. 

Figure 9-1 Collapsed barrel stacks. 

Each winery developed unique recovery operations based on the level of 

severity of the damage. The recovery methods included: 

•	 Custom extensions attached to the forklifts to allow personnel to walk 

along the forks and attach a custom chain to the chime of the barrel (the 

small lip at the end of the staves adjacent to the head of the barrel). The 

process typically took two to five minutes per barrel based on the 

location and the potential for further collapse of the pile upon removal of 

a barrel. 

•	 Used automotive tires were utilized in piles at the base of the stacks as a 

safe landing pad. The barrels were manually pushed off the top of the 

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stack by a person standing on an adjacent stack or by the forks of the 

forklift. Generally every attempt was made to empty the barrel before it 

was pushed off to land on the stack of tires. This method proved to be 

very time consuming but effective in preserving the wine within the 

barrels. 

•	 Dismantling the partially collapsed stacks with a forklift. The operation 

was similar to the method in which barrels are moved within the facility 

during normal operations, with the added risk of subsequent stack 

collapse. Partially collapsed stacks generally were leaning on other 

adjacent stacks. Removal of an adjacent level would redistribute the 

loading and cause collapse of the adjacent stacks. The operation was 

tedious and risky. Therefore, lessons from these operations should be 

studied and documented for wineries to use in future emergency response 

plans. 

•	 Rigging a small crane with two operators to recover the collapsed 

barrels. The crane was mobile and was the largest unit that could fit 

within the roll-up doors at the front of the facility. The operation proved 

to be highly efficient in recovery of both full and empty barrels. The 

cost of the crane rental was significant but necessary in order to get 

facilities fully operational in preparation for the harvest and crush in 

September. 

9.2.2 Earthquake Insurance 

The vast majority of wineries do not carry earthquake insurance coverage for 

the contents, including case goods, tanks, and barrels. Earthquake insurance 

coverage for winery contents is cost-prohibitive or unobtainable for smaller 

wine production facilities. Some of the larger wineries, with multiple 

production facilities throughout California and the United States, carry multihazard peril coverage, which covers fire, flood, windstorm, and earthquake. 

In general, earthquake insurance is not common, and had limited impact on 

the economic recovery of the winery operations. 

9.3 Wine Barrel Storage 

Wineries in the Napa Valley generally utilize one of the following methods 

to store wine barrels, listed from most common to least common: 

•	 Portable Steel Wine Barrel Racks: These racks were invented in the 

late 1980s by a former Robert Mondavi Winery employee. There are 

about six major manufacturers of these racks. The dimensional 

properties of the racks are virtually identical between manufacturers. 

The racks are constructed with a mix of mild steel bars and electric 

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resistance welded square tubing. The racks are painted or powder coated 

for corrosion resistance. They are manufactured in a two-barrel 

configuration (one rack supports two barrels) and a four-barrel 

configuration (one rack supports four barrels). The four-barrel 

configuration consists of two, two-barrel racks linked together to create a 

longer footprint in one direction. The most common configuration used 

in California wineries is the two-barrel rack. The use of the four-barrel 

rack is generally reserved for high production, large volume wine 

facilities. Small wineries typically do not have the floor space or 

forklifts with the capacity required to move the four-barrel rack. The 

barrel rack systems allow the winery to maintain high density storage, 

limited only by the clear height of the roof and the available floor space. 

Stack heights range from one level up to a maximum of six barrels high. 

Above six high, the weight of the full barrels will deform and potentially 

crush the barrel on the bottom level. Each level of barrels is 

approximately three feet tall. 

•	 Pyramid Stacks: In this approach, the barrels are stacked atop one 

another in a pyramid form. The barrels are “chocked” into place with 

wood wedges or using custom fabricated steel cradles. Pyramid stacks 

are used in facilities that can access and maintain the wine in-place, 

rather than moving the barrels to a dedicated washing and maintenance 

region (typical of wineries using the portable steel barrel rack system). 

Pyramid stacking is most commonly used in subterranean caves, with 

stack heights generally no taller than three barrels. Taller stacks require 

a ladder to access the upper level barrels. 

•	 Fixed, Engineered Rack Systems: A limited number of facilities use 

fixed storage rack systems, generally designed and constructed in 

accordance with the building code of the era. These systems are 

generally constructed of heavy timber framing or structural steel. Only 

one facility in the region of high seismic ground shaking used this 

system. 

•	 Other Storage Systems: There are a number of other barrel storage 

methods in limited use in the Napa Valley. This includes rack 

configurations that are a hybrid of a portable rack in a pyramid 

configuration. Other racks are similar to the portable steel barrel rack, 

but use a steel post and beam frame. The barrels are supported on the 

frame and subsequent levels of the racks are supported on the four corner 

posts, not the barrels below. 

There was no reported loss of barrels in caves with pyramid stacks. The 

wineries in the affected region (within 10 miles of the epicenter) generally 

FEMA P-1024 9: Performance of Wine Industry Facilities 9-5 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

used portable steel barrel racks. No damage to engineered rack systems was 

reported. 

There was no report of collapse of wine barrels on four-barrel rack system. 

One winery within 0.5 miles of the epicenter lost two barrels from the top of 

five-high stacks of portable steel four-barrel racks. 

One of the largest wine co-op facilities suffered the most significant loss 

documented in the earthquake, where over 60% of the barrel stacks 

collapsed. This facility houses wine barrels for hundreds of different custom 

crush clients. The recovery operation was time consuming and dangerous, 

compounded by the numerous winemakers arriving at the site after the 

earthquake with the sole purpose of recovering their own barrels, disrupting 

the recovery process. 

Smaller wineries typically do not have operational requirements to stack the 

wine barrels to the heights used by the larger operations (5 to 6 levels high). 

The losses to barrel stacks were generally less with these facilities due to the 

lower fall heights and durability of the wine barrels. 

9.4 Wine Tanks and Catwalks 

The majority of stainless steel wine tanks in the affected region were empty 

in preparation for the wine grape harvest and crush. Thus damage to wine 

tanks was limited. The number of tanks damaged beyond repair is currently 

reported as eight. All damaged tanks were full of wine. There was no 

reported damage to empty tanks. The total loss of wine due to tank damage 

is still being collected as of the publication of this document, but is estimated 

to be just over 10,000 gallons inclusive of all wineries. 

Tank anchorage appeared to play a part in the overall performance. Tanks 

with appropriately sized and spaced anchors performed well. Damage was 

limited to minor deformation of the bottom course of stainless steel in the 

structural wall. Tanks without anchorage shifted on the cellar floor or shifted 

on concrete pedestals (Figure 9-2). The movement of the tanks resulted in 

rupture of fixed glycol cooling lines and tank-supported catwalks. One tanksupported catwalk collapsed when the tank shifted off its concrete pedestal. 

Poorly anchored tanks had the worst performance. Some tanks with poorlydesigned anchorage and limited number of anchorage points suffered failure 

of the tank wall at the anchorage. Wine was lost through the resulting hole in 

the tank wall on four 5,000 gallon tanks in the Oakville region. The tanks 

were anchored using a 1/4 inch weld, 4 inches long, between four steel 

embed plates in the concrete pedestal and the base of the tank. 

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Figure 9-2 Anchorage failure allowed tank to shift on pedestal. 

9.5 Bottle and Case Good Storage 

Wrapped and palletized case good storage performed well in this earthquake. 

There was no reported loss of wine due to collapsed case good storage on 

bulk pallets. The bulk of bottling operations were recently completed and 

most of the case goods had been shipped off site to distribution facilities and 

wine consumers. 

Over 100 wineries reportedly suffered losses to individual wine bottle 

storage and loose case goods, generally within the tasting facilities or the 

estate wine libraries. Bottles toppled from shelves and lay-down, wallmounted wine racks. Total loss of wine from bottle breakage is not fully 

documented but is a marginal percentage of the total production of the 

wineries in the region. The damage resulted in restricted use of the tasting 

facilities for generally two to three days. 

9.6 Winery Building Performance 

Compared to the performance of wine facility contents, the buildings 

performed relatively well. Construction types, configurations, and era of 

construction of the winery facilities in the effected regions are varied. The 

most common construction types include concrete tilt-up, concrete masonry 

bearing wall, wood-frame, and pre-fabricated metal buildings. The majority 

of winery buildings are of 1960s or newer vintage. 

The following sections summarize the performance at four winery facilities 

that sustained notable structural damage. 

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9.6.1 Historic Winery Building, Napa 

The three-story timber-frame winery building, built in 1886 sustained 

significant structural damage. The building was posted UNSAFE and will be 

repaired and returned to service. Full wine barrels, stacked on portable steel 

barrel racks (three levels tall), were stored on the second floor level. The 

mass of the barrels contributed to the shear failure of the exterior lap siding. 

Residual interstory drift at the first story was approximately 15%, with 

virtually no permanent drift at the second and third stories (Figure 9-3). 

Figure 9-3	 Historic timber-framed winery building with large residual drift 

at the ground floor. 

9.6.2 Wine Co-Op Facility, Napa 

The facility sustained significant damage to the interior structural steel 

columns due to impact with toppling wine barrel stacks (Figure 9-4). The 

building was constructed circa 1970 and is a one-story, pre-fabricated metal 

structure. Damage was sufficient to require replacement of one third of the 

columns. No other structural damage was noted. 

9.6.3 Winery Facility, Napa 

This facility sustained damage to the exterior corrugated metal walls due to 

interaction with collapsed wine barrel stacks. Barrels stacked on two-barrel 

racks toppled and blew out the wall at the rear of the main barrel cellar. The 

building was constructed in the 1980s and is a one-story, pre-fabricated metal 

structure. No other structural damage was noted. 

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Figure 9-4 Steel columns damaged by impact of barrels. 

9.6.4 Barrel Warehouse, Napa 

This facility sustained partial collapse of the wood-frame roof structure at the 

south end of the property. The building was constructed in the 1950s and is a 

one-story concrete masonry bearing wall building with a panelized woodframe roof. The connection between the central glue laminated beam and the 

south wall pilaster failed, resulting in a loss of support at the south end of the 

glue laminated beam (Figure 9-5). On Monday August 25, the day after the 

earthquake, the roof was hanging due to secondary action of the roof 

plywood. The plywood diaphragm nailing started systematically failing in 

the early afternoon of August 25, resulting in a complete collapse of the 

south roof at about 3 in the afternoon. The roof was demolished and 

reconstructed with a seismic upgrade at the south end. A seismic upgrade at 

the undamaged regions is planned as a second phase. 

9.7 Summary 

9.7.1 Structural Damage 

The earthquake showed that the mass of the toppled wine barrel stacks is 

sufficient to damage buildings structurally, and can result in local or global 

collapse of the building. Storage of wine barrels on the upper floors of a 

structure can create a serious vertical mass irregularity. Barrels placed 

directly against the perimeter concrete tilt-up or 

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Figure 9-5	 Failure of glulam beam to wall connection resulted in roof 

collapse. 

concrete masonry unit (CMU) walls may topple against or impact the wall, 

imparting additional mass and increasing the out-of-plane force demands on 

the roof diaphragm connections. The additional mass will increase the 

potential for wall-anchorage failure unless the mass of the barrels was 

considered in the original design of the wall anchorage. 

9.7.2 Wine Barrel Storage 

The overwhelming proportion of wine loss and wine barrel collapse was due 

to the two-barrel portable steel barrel rack system. This rack has 

demonstrated poor performance in the 2000 Yountville, 2003 San Simeon, 

and 2014 South Napa earthquakes. The barrel stacks can collapse due to 

“walking” of the racks over the barrels below or by sliding of the racks off 

the barrels below. Failure can occur at any level of the stack. The rack 

sliding or walking is affected by the point of contact with the barrel below. 

The performance of the two-barrel rack has been well-documented through 

prior California earthquakes and academic research. There were no reported 

collapsed stacks using the four-barrel rack. 

Wine barrels are resilient and can endure a fall from heights generally below 

eight feet. Facilities with significant stack collapse suffered relatively low 

losses due to the cascading collapse of the stacks and the reduced fall height 

of the barrels. Wine loss was generally attributed to the first wave of barrels 

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to fall directly on the warehouse floor and barrels with dislodged bungs, 

resulting in slow leaks and wine oxidation. The steel hoops on the barrels are 

spaced at various locations along the length of the barrels (this varies by 

barrel type and manufacturer). The coefficient of friction between the steel 

rack and the steel hoops is sufficiently low compared to the rack supported 

on the wood staves. Further research is planned to study the effects of this 

interface with a future recommendation to barrel manufacturers on proper 

hoop placement. 

9.7.3 Steel Tanks and Catwalks 

Poorly anchored tanks exhibited poor performance in comparison to properly 

anchored tanks. Wine losses were generally attributed to poorly anchored 

tanks. The performance of unanchored tanks could not be well studied, since 

the majority of the unanchored tanks in the effected region were empty. 

Wineries should consult with the tank manufacturers to obtain appropriate 

anchorage design for high seismic regions. The design of the anchorage 

should consider the tight spacing between the tanks. The anchor capacity is 

often times controlled by the edge clearance at the concrete pedestal or the 

center-to-center distance between adjacent anchors. 

Catwalks should not be supported on tanks that are unanchored. Movement 

of the tank can result in failure of the catwalk supports, resulting in a threat 

to life safety if a winery employee were on top of the catwalk or below it. 

9.7.4 Bottle and Case Good Storage 

Bulk, palletized case goods tend to perform well when subjected to strong 

seismic ground shaking. Wine bottles stored on shelves and lay-down storage 

racks are vulnerable to toppling or sliding. Winery tasting facilities could 

implement simple restraint systems, such as cables or wires, to prevent 

toppling of the bottles. Lay-down wine racks could be outfitted with rubber 

pads to provide increased friction to prevent sliding of the bottles in the 

racks. A number of wineries lost individual bottles in their on-site estate 

wine collections. The economic loss of these bottles was significant 

compared to the wine available for retail purchase in the tasting room. 

9.8 Recommendations 

Recommendations for winery operations and future research opportunities 

are listed below. 

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9.8.1 Wine Barrel Storage 

1.	 The four-barrel portable steel barrel rack demonstrated superior seismic 

performance in comparison to the two-barrel rack. Use of the four-barrel 

rack is highly recommended. 

2.	 Whenever possible, the height of the stacks should be limited to four or 

less. Shorter stacks tend to perform better and are less likely to topple. 

The lower height reduces the fall height of the wine barrels, decreasing 

the possibility of wine loss due to barrel breakage. 

3.	 When using the two-barrel portable steel barrel rack, the stacks should be 

oriented with the heads touching in adjacent rows. The rows should be 

oriented with the barrel bilges in contact. The current common practice 

is to stack barrels in deep rows with the heads in contact. Collapse of the 

stacks results in a domino effect as observed in this earthquake and prior 

earthquakes. 

4.	 Appropriate space should be provided between the exterior walls and the 

barrel stacks to avoid interaction should the stacks become unstable or 

collapse. 

5.	 Stacking barrels on warehouse floors with aggressive slope for drainage 

should be avoided. Barrel stacks will have a static lean towards the 

central drains, increasing the likelihood of collapse when subjected to 

seismic ground shaking. 

6.	 Wine barrel storage on portable steel barrel racks or pyramid 

configurations is not subject to the nonstructural seismic design 

provisions in the 2013 California Building Code (California Building 

Standards Commission, 2013a) and ASCE/SEI 7-10, Minimum Design 

Loads for Buildings and Other Structures (ASCE, 2010). The barrels are 

classified as contents and are not required to be anchored or permanently 

fixed to the foundation. Further discussion on the performance of this 

system is warranted within the framework of the structural and fire safety 

provisions in the building code. 

7.	 The top barrels should be restrained to their rack in stacks of barrels on 

portable steel barrel racks. The barrels can be restrained with a variety of 

methods, including straps, clips, or other means. Without restraint, the 

top barrels can easily roll off the supporting rack below and fall to the 

cellar floor. 

8.	 Further research is warranted to study options to improve the 

performance of the two-barrel rack. The wine industry uses this rack 

throughout the western states and switching to a four-barrel rack system 

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and the equipment to handle them is generally cost-prohibitive. 

Additional research could focus on simple and cost-effective strategies to 

improve the performance of this system and allow wineries to continue 

using it. 

9.	 Seismic isolation systems could be an option to limit the seismic ground 

shaking experienced by the barrel stacks. Prior research into the 

application of isolators (full building isolation or low-mass isolator pads 

beneath the barrel stacks) revealed that performance could be improved 

and damage minimized. However, the cost of isolation systems is a 

significant barrier. In addition, the use of isolation pads beneath the 

barrel stacks is not logistically feasible for most high production 

wineries. The highly corrosive, damp environment is not ideal for balland-cone or friction pendulum isolator applications. 

9.8.2 Wine Tanks 

1.	 Wine tank shells and anchorage should be designed in accordance with 

the appropriate American Water Works Association (AWWA) or 

American Petroleum Institute (API) design standards for thin-walled 

vessels. Stainless steel wine tank manufacturers should be attentive to 

the tank anchorage and the placement of the tank in the facility to ensure 

sufficient edge clearance for the embedded anchor bolts. 

2.	 Wine tanks with properly designed anchorage have generally better 

performance over tanks with no anchorage or poorly designed anchorage. 

Existing tanks should be evaluated for anchorage capacity and future 

seismic performance. Retrofit of the tank anchorage may be warranted 

to limit future damage. 

3.	 Unanchored tanks should conform to the requirements of ASCE/SEI 

7-10 Chapter 15, Sections 15.7.5 and 15.7.6. They should not be 

connected to the cooling supply lines with rigid connections. Snubbers 

could be used to restrict the movement of the unanchored tanks. The 

snubbers could allow some level of sliding to dissipate energy. 

4.	 Independent gravity support for catwalk systems is desirable. Tanksupported catwalk systems should only be used with tanks that are 

properly anchored. 

9.8.3 Occupant Seismic Safety, Response, and Recovery 

1.	 In order to improve personal protection if occupants cannot get out of the 

building in time, steel cages mimicking the design of a forklift rollover 

protection cage should be provided throughout the barrel storage facility. 

They could be placed at identified locations throughout the barrel room 

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and would provide a safe haven for employees working in the room 

during an earthquake. 

2.	 Wineries should study the fall and collapse patterns of the wine barrel 

stacks. The study can provide a means for access and egress planning 

and disaster response and recovery within the winery. The study should 

include potential interaction between the barrel stacks, the building and 

surrounding process equipment and wine tanks. 

3.	 The noise from winery operations could hamper an employee’s ability to 

sense when an earthquake is occurring. The winery facilities could be 

outfitted with a public announcement (PA) system with air horns or 

sirens. The PA system could be linked to a seismic ground motion 

sensor or an early warning system. A loud horn or siren, together with 

the appropriate training, could provide the necessary alert and improve 

life safety in the facility. 

4.	 Whenever possible, exposure of the public and winery guests to the wine 

barrel stacks should be limited. Tasting facilities and private events are 

often located in close proximity to the wine barrel stacks. The poor 

performance of this storage system warrants revisiting this practice and 

limiting access to the barrel storage areas to winery employees with 

proper training. 

5.	 A response and recovery plan should be developed, as well as staff 

training. Annual recovery drills should be conducted and special 

equipment should be made available to speed the recovery efforts. 

Wineries should share their recovery best practices within the industry. 

6.	 Response and recovery may include industry mutual aid partnerships 

with wineries in other regions and or plans to quickly move barrels and 

finished wine to other facilities outside the affected region. 

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Chapter 10
 

Performance of Nonstructural 

Components 

10.1 Introduction 

Nonstructural components include all of those building components that are 

not part of the structural system, including architectural, mechanical, 

electrical and plumbing systems, as well as building contents, such as 

furniture and inventory in commercial and retail establishments. Damage to 

nonstructural components and systems in buildings accounts for the majority 

of repair costs in earthquakes, and can contribute to extended downtime for 

repairs. While most modern structures sustained little or no structural 

damage in the 2014 South Napa earthquake, several sustained significant 

nonstructural damage. Also, the only fatality attributable to the earthquake 

was caused by nonstructural damage. 

Seismic design requirements for nonstructural components are contained in 

Chapter 13 of ASCE/SEI 7-10, Minimum Design Loads for Buildings and 

Other Structures, (ASCE, 2010), although furniture and most building 

contents are exempt from code requirements. FEMA E-74, Reducing the 

Risks of Nonstructural Earthquake Damage, (FEMA, 2012a) explains the 

sources of earthquake damage that can occur in nonstructural components 

and provides information on effective methods for reducing risk associated 

with nonstructural earthquake damage, and provides building code provision 

information for commonly used nonstructural components. 

The following factors influence the seismic performance of nonstructural 

components: 

•	 Codes and standards must provide a suitable basis for design. 

•	 Design requirements for nonstructural anchorage and bracing must be 

properly followed. 

•	 Items that require seismic design must be identified and the construction 

documents must clearly illustrate the proper installation details. 

•	 Nonstructural components must be installed in accordance with the 

construction documents. 

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• Adverse interaction (impact) between nonstructural components or 

nonstructural component and the structure must be avoided. 

•	 In cases where components are exempt from code-mandated seismic 

design, consideration of the potential seismic performance should be 

considered and protective measures implemented where needed. 

A deficiency in any of these steps may result in a component installation that 

is vulnerable to unacceptable earthquake damage. 

Seismic provisions of the building codes in general have undergone 

significant changes in the last two decades, and the requirements for 

nonstructural components in particular have changed dramatically. The 

types of nonstructural components subject to the seismic provisions have 

been greatly expanded, the design forces for components have increased, and 

the requirements for attaching the components to concrete and masonry 

construction are much more comprehensive. These changes complicate the 

postearthquake evaluation of nonstructural damage, since the rules under 

which the component was installed may be much different than those 

recommended today. If the component in question does not fully conform to 

those current requirements, care must be taken when drawing conclusions on 

the adequacy of current code requirements. 

In the following sections, observations on the performance of different types 

of nonstructural components are presented, along with example buildings 

that highlight the nature of the damage sustained. Some of the buildings 

discussed are located within the 1,000 foot radius around the Station N016; 

some are not. The structural and nonstructural performance of some of the 

buildings included in this study are discussed in previous chapters. 

Observations on the nonstructural performance of these buildings are not 

repeated here, and where the nonstructural performance of these buildings is 

of special interest, a reference to the appropriate section of this report is 

provided. 

10.2 Exterior Enclosures 

The buildings surveyed had a variety of building exterior enclosure systems, 

including glazed curtain wall and storefront systems, light-frame wall 

systems with stucco finishes, natural and artificial stone veneers attached to 

light-frame wall systems or to structural walls, and precast concrete cladding. 

10.2.1 Glazing, Glazed Curtain Walls, and Storefront Systems 

Damage to glazing was fairly widespread. Of the 68 buildings included in 

the 1,000 foot radius survey around Station N016, 22 buildings sustained 

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damage to 5% or more of the exterior glazing and four buildings to 50% or 

more of the exterior glazing. 

The performance of glazing systems depended in large part on the amount of 

story drift the building experienced, and the tolerance of the glazing 

assembly for story drift. In some cases, the glass did not crack or shatter, but 

the gaskets holding the glass in frame loosened, allowing the pane to shift. 

Large panes of glass were more vulnerable than smaller panes. Older 

buildings, which tended to have open storefronts with large panes of glass, 

suffered most of the glazing damage. The head of a single-bay storefront 

glazing system at Queen of the Valley hospital displaced several inches outof-plane (see Section 5.2.1). 

One-story unreinforced masonry buildings with open storefronts within the 

1,000 foot radius sustained losses of up to 60% of the storefront glazing 

(Figure 10-1). In retrofitted unreinforced masonry buildings, glazed 

storefront damage was more pronounced on building elevations where lateral 

resistance was provided by moment frames, compared to buildings with 

stiffer lateral force-resisting systems. The building in Figure 10-2 was 

retrofitted with a steel moment frame along the front. The stiffness of the 

steel frame appears to have been insufficient to limit drift sufficiently to 

protect the glazing. 

Figure 10-1 Broken glass at open storefront on an unreinforced masonry 

building. 

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Figure 10-2	 	 Typical condition showing temporary plywood barricades and 

plastic over openings where storefront glazing was damaged. 

Nine of the ten plate-glass windows in the Napa County air traffic control 

tower, each 3/4” thick, where shattered during the earthquake (Figure 10-3). 

No employees were present during the earthquake, because the Napa tower 

operates only between 7 a.m. and 8 p.m. Consequently, there were no 

injuries. No structural damage was reported. A temporary tower was 

brought to the site to allow for continued use of the airport (Figure 10-4). 

Figure 10-3 Broken glass in Napa County air traffic control tower (photo by 

J.L. Sousa/Napa Valley Register/ZUMAPress.com). 

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Figure 10-4 Temporary air traffic control tower. 

10.2.2 Light-Frame Curtain Wall Systems 

Minor cracking of stucco finishes on light-frame exterior walls was observed 

in many buildings within the 1,000 foot radius survey around Station N016. 

The performance of light curtain wall systems on modern structures varied 

significantly, with several buildings sustaining substantial cracking, 

connection failures to the building structure, and loss of veneer. Other 

modern buildings sustained insignificant damage to their exterior curtain 

walls. 

A three-story office building with a steel moment-resisting frame sustained 

significant curtain wall damage. The performance of this building is 

discussed in detail in Section 4.2.2. The wall system lacked a mechanism to 

accommodate story drift, and lateral displacements of the structure in the 

earthquake resulted in connection failures, separation of the curtain wall from 

the structure, and permanent displacements. Significant damage to a lightframe curtain wall system was also observed in a five-story hotel, which also 

sustained damage to stone veneer. This building is discussed in Section 

4.2.3. Failures of both anchored and adhered veneers were observed in these 

buildings. The performance of adhered veneer was directly related to the 

performance of the substrate and the strength and condition of the adhesive 

material. 

In one building, an entire built-up light-frame exterior wall unit detached 

from the building and fell on the sidewalk (Figure 10-5). It was reported that 

the wall connectors were weakened as a result of corrosion. 

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Figure 10-5	 Metal stud and stucco framed cladding dislodged from concrete 

wall. 

10.2.3 Precast Cladding 

There were few buildings with precast cladding in the 1,000 foot survey area. 

Immediately outside the 1,000 foot radius, one precast panel dislodged and 

fell from a telephone operations facility, built circa 1961, clad with precast 

concrete panels anchored to a concrete frame with steel angles and embedded 

anchors. During the earthquake, one panel in the penthouse fell outward 

(Figure 10-6). There were early reports that the panel was designed as a 

removable panel to facilitate adding or removing equipment from the room; 

however, this could not be confirmed. Nearly identical precast panels in the 

facility are connected to the structure using angle and anchor details similar 

to those that failed. The dislodged wall fell as a unit and severed the 

building’s utility connection. The backup generator in this facility also 

failed, forcing the facility to maintain operations using stand-by batteries. A 

temporary generator and cooling unit were installed to keep the computer 

servers running during repairs. 

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(a) (b) 

Figure 10-6 Dislodged precast panel in telephone operations facility: (a) missing panel with 

orange brackets remaining in place (photo from PEER (2014)); (b) temporary covering 

after the earthquake. 

10.3 Interior Partitions 

In the observed buildings, most interior partitions were constructed with 

wood or metal studs with gypsum wallboard or plaster sheathing. Partition 

damage was present in many buildings, but most damage was incidental with 

a very small number of buildings experiencing substantial partition damage. 

Within 1,000 feet of Station N016, the interiors of 40 buildings were 

observed. Partition damage was described as “insignificant” or “none” in 

91% of the buildings with interiors observed. Damage was reported as 

“minor” in 6% of the buildings. Two buildings were reported with 

“moderate” damage and none was described as “heavy.” The buildings with 

moderate partition damage also suffered consequential damage due to 

damaged sprinkler piping, which released water for an extended period. As a 

result of water damage, large areas of gypsum wallboard sheathing required 

removal and replacement in these buildings (Figure 10-7). In virtually all 

other cases, repair could be accomplished with local patching and painting 

(Figure 10-8 and 10-9). 

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Figure 10-7 Gypsum wallboard was removed from partition walls where 

water damage from a broken sprinkler head occurred. 

Figure 10-8 Typical damage to gypsum wallboard. 

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Figure 10-9 Damage to gypsum wallboard at corner (photo from OSHPD). 

Older buildings with lath and plaster wall finishes sustained more significant 

damage in the form of cracking and spalling (Figure 10-10). 

Figure 10-10 Cracked and spalled plaster on lath and plaster wall. 

10.4 Ceilings 

Two types of ceilings represent the majority of types affected by the 

earthquake: (1) gypsum wallboard or plaster fastened directly or indirectly to 

structural framing; and (2) suspended acoustic tile ceilings. 

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10.4.1 Gypsum Wallboard and Plaster Ceilings 

Gypsum wallboard ceilings fastened directly to structural framing generally 

performed well. Minor cracking was observed at some locations (Figure 

10-11). Older plaster ceilings did not perform as well as gypsum ceilings. 

Spalling and cracking of these ceilings were observed in multiple buildings 

(Figure 10-12 and Figure 10-13). 

Figure 10-11 Cracking of gypsum wallboard ceiling. 

Figure 10-12 Cracking and spalling of a plaster ceiling in an older masonry 

building in downtown Napa. 

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Figure 10-13	 	 Cracking and spalling of a plaster ceiling in an older reinforced 

concrete building in downtown Napa. 

10.4.2 Suspended Acoustic Tile Ceilings 

Within the 1,000 foot survey area, 16 buildings (24% of the total) were 

identified to have at least some area with suspended acoustic tile ceilings. 

Some damage to the ceilings of these buildings was common, though in only 

one building was it classified as “heavy.” On the opposite side of the 

spectrum, only one building was assessed as having no ceiling damage. The 

majority of these buildings had “insignificant” damage, and two had 

“moderate” damage. 

The most commonly observed form of damage to suspended acoustic tile 

ceilings was fallen tiles (Figure 10-14). Failure of splices in the ceiling grid 

members, as well as damage at the “fixed” and “free” ends of the ceiling 

grid, were observed in several buildings. Figures 10-15 through 10-17 

illustrate a ceiling estimated to be 20 years old that included diagonal wire 

bracing without compression posts. Although reinstalling or replacing tiles 

occurred quickly, failure of the grid itself required an extended period to 

restore. In extreme cases of damage, removal and replacement of the entire 

ceiling was required. 

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Figure 10-14 Acoustic ceiling where tiles fell in an office building. 

Failed splice 

Figure 10-15 Failure of a splice of acoustical tile ceiling grid in a two-story 

retail store in downtown Napa. 

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“Fixed” end pulled out of wall 

Figure 10-16 Failure of “fixed” end support of the acoustical tile ceiling grid 

in a two-story retail store in downtown Napa. 

“Free” end dislodged, 

grid dropped 

Figure 10-17	 Failure of “free” end support of the acoustical tile ceiling grid in 

a two-story retail store in downtown Napa. 

10.5 Mechanical, Electrical, and Plumbing Equipment 

The performance of mechanical, electrical, and plumbing (MEP) equipment 

varied widely in the buildings investigated. Some unanchored or lightly 

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restrained equipment shifted or overturned, and rooftop equipment was more 

heavily damaged than equipment located elsewhere in the building. There 

were failures observed in anchored equipment, but based on the estimated 

age of the equipment installation, the failures occurred in components that 

would not comply with current code. MEP components installed to recent 

standards generally performed well, with the exception of pendant light 

fixtures. The Napa County Hall of Justice (Building F3) consists of two 

wings, one constructed circa 1974 and the other constructed circa 1989. The 

MEP components in the newer wing performed substantially better than 

those in the 1974 Wing. Performance of the MEP components in this facility 

is discussed in Section 4.3.5. In several schools (see Chapter 6) and grocery 

stores, suspended pendant light fixtures became dislodged and dropped. Had 

the earthquake occurred during the day, related injuries would have been 

likely. 

At a grocery store on Trancas Avenue, Napa, the primary lighting in the 

store, which was constructed within the past ten years, consisted of pendant 

fixtures suspended over the aisles. The 1 foot by 4 feet fixtures were 

connected end-to-end and mounted directly to struts that were in turn 

connected via aircraft cable to an “S” hook that connected to an eyebolt 

fastened to the structure. Approximately 10% of the fixtures fell because the 

“S” hook opened up under the combined forces due to seismic loads and the 

weight of the lights (Figure 10-18). The connection detail is shown in Figure 

10-19. 

Figure 10-18 “S” hook opened during earthquake and caused fixtures to 

drop. 

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Figure 10-19 Pendant fixture support detail. 

10.6 Piping Systems 

Piping systems were the source of a considerable portion of damage 

sustained in the earthquake. Automatic fire sprinklers and related piping 

caused substantial damage, in some cases even significant flooding. The 

vulnerability of smaller diameter piping, the lack of adequate clearance 

between the fire sprinkler heads and other equipment, such as ductwork and 

suspended air handling units, and the failure of piping connected to 

inadequately anchored equipment were also demonstrated. 

The county office building on 1st Street, Napa (Building C4) is a two-story 

concrete shear wall structure with a mezzanine. This building sustained 

extensive damage when a single sprinkler head on third floor above the 

ceiling began discharging water after it impacted either a U-hanger for the 

branch line or an adjacent wood beam (Figure 10-20). The sprinkler system 

could not be shut off, and the sprinkler ran for five hours. All partition walls 

and floor coverings sustained extensive water damage. The building was 

expected to be out-of-service for several months. 

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Figure 10-20	 Sprinkler head interaction with adjacent components resulted in 

extensive flooding. 

A single sprinkler line failed at a threaded fitting and flooded the first floor 

of a three-story theater building on Main Street in Napa (Building L2) 

(Figure 10-21). The water to the fire sprinkler system could not be shut off 

because the valve was locked in the open position. The fire pump activated 

and continued to run, and the flooding continued for about nine hours. The 

hardwood floor in the first floor warped and in some areas buckled. In 

addition, some of the partition finishes were damaged by the water and had 

to be replaced. The building was closed for a week to dry out the flooring 

and repair water damage. 

Figure 10-21 Repaired condition of a failed pipe at threaded connection that 

resulted in flooding of the first floor restaurant. 

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Five sprinkler lines suspended from the roof of a two-story retail building in 

the Napa Town Center reportedly broke and remained on for several hours. 

The sprinkler piping had threaded connections and damage appears to have 

been related to swaying and interaction with adjacent HVAC components 

(Figures 10-22 and 10-23). The elevator and escalator pits were flooded and 

both systems required repair. Contents were damaged as a result of the 

water; and considerable amounts of gypsum wallboard were damaged and 

required removal. 

Figure 10-22 Sprinkler piping in close proximity to HVAC components. 

Figure 10-23 Sprinkler armover in close proximity to HVAC components. 

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Domestic water pipe breaks in the penthouse of the Napa County 

Administrative Offices (Building F2) resulted in water damage to the third 

floor ceilings. The conditions contributing to the pipe failures are discussed 

in Section 4.3.4. 

Unbraced sprinkler pipes in a parking garage in downtown Napa supported 

with threaded rods and powder driven fasteners sustained several types of 

damage including permanently bent threaded rod hangers and pullout or 

failure of powder driven fasteners (Figures 10-24 and 10-25). No water 

release was reported. This type of fastener is no longer permitted by the 

building code and the city is not allowing its use for repairs. 

Figure 10-24 Sprinkler installation in parking garage. 

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Figure 10-25	 	 Failures of powder driven fasteners. Bottom right photo is from 

PEER (2014). 

10.7 Contents 

Contents generally refer to components that are not part of the building 

architecture or MEP systems, furnished and installed by the occupant, and 

generally not regulated by the building code. This includes temporary or 

movable items, equipment that is not permanently attached to the structure 

such as desktop items (e.g., computers, copiers, lamps), and most furniture, 

except permanent floor-supported storage cabinets, shelving or book stacks 

over 6 feet tall. Even though they are not regulated by the code, contents 

pose a seismic risk. Unrestrained items may slide, impact other items, tip, or 

overturn, and in some cases, block exits. Failure of one item may damage 

others or cause the collapse of other items. Contents supported on furniture 

or fixtures may fall, break, or spill. 

Virtually all buildings within 1,000 feet of Station N016 experienced some 

contents damage. In some cases, the damage was limited to shelf-mounted 

items shifting or falling. In others, larger furnishings overturned or shifted. 

Had the earthquake occurred at another time of day, contents damage could 

have caused injury or death. The one death attributable to the earthquake 

was caused by a television that shifted off a table and struck the victim in the 

head. 

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The following general observations are noted: 

•	 The majority of retail stores, including wine and olive oil shops, and 

restaurants, experienced loss of product from shelving (Figures 10-26 

and 10-27). An example of a wine storage rack in a retail store where no 

bottles were lost is shown in Figure 10-28. 

•	 In some stores, unanchored shelving racks or storage units overturned 

into aisles (Figure 10-29) 

•	 Some office furnishings overturned or shifted, posing a life-safety hazard 

had the spaces been occupied at the time of the earthquake (Figure 

10-30) 

Figure 10-26 Contents dislodged from grocery store shelves. 

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Figure 10-27 Loss of products from shelves. 

Figure 10-28	 Wine storage rack in retail store that did not lose a single bottle 

of wine in the earthquake. The storage racks were modular 

units of interlocking wood and metal slats. The wine bottles sat 

on two metal slats, one supporting the lower bottle body and a 

front one supporting the bottle neck. The bottle shoulder sat 

below the front slat that kept the bottles from sliding out. 

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Figure 10-29 Unanchored fixtures overturned in aisle. 

Figure 10-30 Overturned unanchored bookshelf. 

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10.8 Solar Arrays 

Building code requirements for solar arrays are still under development and 

there has been some discussion over their content. For this reason, 

information was collected on the performance of different solar arrays in the 

area. Eight solar arrays in the Napa region were investigated. The arrays 

included a range of installation types: Ground-mounted parking canopies, 

roof-mounted parking canopies; roof-mounted low-profile arrays with ballast 

and mechanical attachments; and roof-mounted low-profile arrays without 

mechanical attachments (ballast only). The sites were located in Vallejo and 

Napa. Except for one of the installations, which had an eccentric baseplate 

connection that suffered brace buckling, all of the arrays performed well with 

no reported damage. 

Figure 10-31 shows a variety of different solar array installations present at a 

medical center in Vallejo. The arrays are described in Sections 10.8.1 

through 10.8.3. Ground motion data from an instrument at the medical 

center site is presented in Figure 10-32 for reference. 

Rooftop lowprofile unattached 

array on medical 

office building 

(Section 10.8.3) 

Ground-mounted 

solar canopy 

over parking lot 

(Section 10.8.1) 

Roof-mounted 

solar canopy 

on three-story 

concrete parking 

garage (Section 

10.8.2) 

CGS Station 68294. Recorded PGA 0.469g. 

Figure 10-31 Solar arrays at medical center in Vallejo (image source: 

Google Earth). 

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Figure 10-32	 Recordings from CGS Station 68294, located approximately 300 feet from medical 

center parking garage (from http://strongmotioncenter.org/, last accessed September 7, 

2014). 

10.8.1 Ground-Mounted Solar Array, Vallejo 

This array was mounted on a steel framework over a parking lot (Figure 

10-33). Steel tube columns were anchored to cylindrical concrete pedestals 

that extend approximately three feet above grade. Wide-flange girders frame 

into columns and wide-flange beams run across the top of columns and 

girders. Rows of solar panels are located on the top of the beams. The 

lateral force-resisting system appears to be either an ordinary steel moment 

frame or a cantilever column system. There was no reported interruption in 

power from this array or damage to the supporting system. 

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Figure 10-33	 	 Ground-mounted solar canopy over parking lot (photo from 

Google Street View). No damage reported. 

10.8.2 Roof-Mounted Solar Canopy, Vallejo 

This array consists of a steel open grid framework with multiple bays in both 

plan directions constructed on top of a parking garage roof (Figure 10-34). 

Wide-flange columns have base plates anchored into concrete grout pads on 

the concrete parking structure roof; anchors did not extend into the structural 

roof slab. Wide-flange girders frame into columns. At mid-span of the 

girders, wide-flange beams brace the girders against lateral-torsional 

buckling (Figure 10-35). Rows of solar panels are supported by members 

that span to the girders. Lateral resistance provided by steel tension rod Xbracing is provided at selected bays in the direction perpendicular to girders. 

In the direction parallel to girders, lateral resistance is provided by an 

ordinary steel moment frame. 

The earthquake caused elongation of steel X-bracing rods (Figure 10-36), 

and breakout or crushing of grout around column anchor bolts under column 

base plates (Figures 10-37 and 10-38). The configuration of the baseplates 

and anchor bolts was eccentric with respect to X-bracing rods, amplifying the 

shear demands on the anchor bolts. 

Site personnel reported that the top level of the parking garage was posted 

RESTRICTED USE because of damage to the array, and power from the 

array was shut down. The company that owns and operates the array through 

a power-purchase agreement obtained a permit from the City of Vallejo and 

performed repairs approximately two weeks after the earthquake. 

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Figure 10-34 Parking garage with solar canopy structure on roof (photo by 

Jiun-Wei Lai). 

Figure 10-35 Solar canopy structure on roof of parking garage (photo by JiunWei Lai). 

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Figure 10-36 Elongated steel X-bracing rods. Note residual drift in the shored 

column to the left (photo by Jiun-Wei Lai). 

Figure 10-37	 Possible plastic strain of steel rod X-bracing adjacent to gusset 

plate. Column has twisted due to eccentric configuration of rod 

bracing and anchor bolts. Anchor bolt breakout or grout 

crushing occurred beneath column baseplate (photo by JiunWei Lai). 

FEMA P-1024 10: Performance of Nonstructural Components 10-27 
 

Figure 10-38 Clip angle is anchored to the concrete wall but not attached to 

column baseplate. Note eccentricity between the X-bracing rod 

and the column anchor bolts (photo by John Silva). 

10.8.3 Roof-Mounted Low-Profile Unattached Array, Vallejo 

The 30-foot tall medical office building supports a number of unattached, 

ballasted solar sub-arrays (Figure 10-39). Each sub-array consists of a grid 

of aluminum members, interconnected in east-west and north-south 

directions. The array’s aluminum “feet” bear on the building’s single-ply 

roofing. Resistance to wind uplift is provided by concrete ballast blocks 

stacked in aluminum pans. Ballast blocks stacked over a certain height are 

expected to be secured in the pans with wire or glue. Resistance to 

earthquake forces is provided by friction between the array and the roof 

surface. 

It is reported that the rooftop array did not displace. No interruption in 

power production from this array was reported. The building itself was 

reported to suffer minor nonstructural damage (some drywall cracking, 

falling ceiling tiles, and damage to sprinkler escutcheons were reported). No 

structural damage to the building was reported. 

10-28 10: Performance of Nonstructural Components FEMA P-1024 
Figure 10-39 Low-profile unattached (ballast-only) solar array on roof of 

medical office building (photo from Kaiser Permanente). No 

damage was reported. 

10.8.4 Roof-Mounted Solar Canopy, Napa 

This rooftop array on top of the parking structure on 5th Street in Napa is 

supported on a steel framework constructed with round HSS steel cantilever 

columns (Figure 10-40). Columns have baseplates with anchor bolts into the 

top of a concrete wall that is part of the building structure. There was no 

observed or reported damage and no apparent loss of power. 

Figure 10-40 Roof-mounted solar canopy on top of parking garage structure. 

No damage was reported. 

FEMA P-1024 10: Performance of Nonstructural Components 10-29 
 

10.8.5	 Roof-Mounted Low-Profile Arrays Including Ballasted and 

Mechanical Attached Systems 

Roof-mounted low-profile arrays with solar panel support systems were field 

examined by a system manufacturer. The arrays use a combination of ballast 

and mechanical attachments to the building roof. 

No damage was reported at any of the four sites visited, and there was no 

reported interruption of power production. The sites included two wineries, a 

movie theater, and an office warehouse building (Figure 10-41). Some 

instances of support movement (1 inch or less) were reported (Figure 10-42), 

and there was some evidence of load applied to mechanical attachments 

(Figure 10-43), but it is not clear whether the observed movement was 

caused by the earthquake or other sources such as thermal expansion and 

contraction. Table 10-1 provides a summary. 

Figure 10-41 Locations of rooftop solar arrays inspected by manufacturer’s engineers following the 

earthquake (Image from Google Earth.) 

10-30	 10: Performance of Nonstructural Components FEMA P-1024 
Figure 10-42	 Solar array on the roof of an office and warehouse building two 

miles east of earthquake epicenter (photo from PanelClaw, 

Inc.). Array includes ballast and mechanical attachments to the 

building roof at selected locations. No damage reported. 

Figure 10-43 Mechanical attachment of solar array on the roof of an 

office/warehouse building two miles east of earthquake 

epicenter (photo from PanelClaw, Inc.). Array includes ballast 

and mechanical attachments to the building roof at selected 

locations. Mechanical attachments are evenly distributed 

throughout the array and typically showed similar evidence of 

possible movement. 

FEMA P-1024 10: Performance of Nonstructural Components 10-31 
Table10-1 Summary of Low-Profile Attached Rooftop Solar Arrays 

Building Location Height (ft.) Construction Roof 

Modules per 

attachment Roof slope Observations 

Winery 

North of 

Napa, 12 

miles from 

epicenter 

26 

Concrete 

tilt-up, 

woodframed roof 

PVC 26 

Barrel 

shaped, 

mostly eastwest slope 

Free ends of some 

south supports 

displaced 0.5 inch 

or less toward 

east. 

Theater 

Near 

downtown 

Napa, 4 

miles from 

epicenter 

40 

Concrete 

tilt-up, steelframed roof 

TPO 

with slip 

sheets 

20 

Nearly flat 

(1/2 inch 

per foot or 

less) 

Some supports 

displaced 1.0 inch 

or less on top of 

slip sheets, 

generally in the 

same direction 

Office/ 

warehouse 

2 miles east 

of epicenter 25 

Concrete 

tilt-up, steelframed roof 

Mineral 

cap sheet 6 

Arrays cross 

roof ridge; 

modules 

mostly on 

east slope 

Attachments show 

deformations 

indicating possible 

displacement 

toward north 

(Figure 10-42) 

Warehouse 

/ laboratory 

American 

Canyon, 3 

miles 

southeast of 

epicenter 

25 Tilt-up TPO 12 

Nearly flat 

(1/2 inch 

per foot or 

less) 

No evidence of 

movement 

10.9 Summary 

While most modern structures suffered little or no structural damage in the 

2014 South Napa earthquake, several experienced significant nonstructural 

damage. This type of damage continues to account for the vast majority of 

the earthquake damage. In some cases, nonstructural damage caused 

buildings to be closed for six months or more. 

By far the most costly nonstructural damage was caused by damage to fire 

sprinkler systems. The extent of damage was primarily related to three 

factors: (1) the time it took to turn off the water after the damage was 

identified; (2) the number of pipe or sprinkler head breaks; and (3) their 

location in the building (rooftop versus other locations in the structure). In 

cases where water release lasted for several hours, damage to a single pipe or 

sprinkler head was sufficient to flood substantial portions of the building and 

require building closure for several months. Most of the damage was 

sustained in small diameter unbraced sprinkler piping. It appears that much 

of the damage was caused by interaction (impact) of sprinkler heads or pipe 

fittings with adjacent suspended components. 

Damage to cladding posed a risk to the public as adhered veneer was 

dislodged from several buildings and one precast panel fell from a building. 

In one modern building, the exterior stucco wall was severely damaged 

10-32 10: Performance of Nonstructural Components FEMA P-1024 
because it was not detailed to accommodate the expected story drift of the 

structural framing system. In another case, an entire built-up light-frame 

exterior wall unit detached from the building and fell on the sidewalk. 

Consistent with observations in past earthquakes, unanchored equipment and 

inadequately restrained equipment suffered damage. The damage to rooftop 

equipment was generally more severe than damage to equipment in other 

building locations because of the higher amount of accelerations in the roof 

compared to other levels. 

Pendant lighting fixtures fell in several retail stores and schools. The causes 

of failure vary from installation to installation due the variety of fixtures and 

connectors used. Based on the observed performance, especially at schools, 

it appears even modern pendant light fixture supports have low reliability. A 

more detailed discussion in provided in Chapter 6. 

Unrestrained furnishings shifted or overturned. In some cases, these 

components posed safety threats. One unrestrained television that struck a 

building occupant on the head and caused the only death directly attributable 

to the earthquake. 

Rooftop solar arrays performed well, except for one canopy structure on the 

roof of a parking garage that had an eccentric base plate connection and 

suffered anchor and rod failures and brace buckling. 

10.10 Recommendations 

The performance of nonstructural components in the 2014 South Napa 

earthquake suggests several areas for possible improvement and further 

study, including: 

1.	 Losses associated with damaged sprinkler piping and sprinkler heads 

were substantial. In order to reduce related losses in future earthquakes, 

several aspects of fire sprinkler design and use should be investigated: 

o	 Immediately following an earthquake, damaged sprinkler systems 

should be shut off as soon as it is clear that the risk of fire following 

earthquake is low. Without fire protection, building owners should 

establish a 24-hour fire watch such that the fire department can be 

called if a fire develops. Since the Fire Department may be 

responding to fires and unavailable to turn off water, alternate 

approaches to safely shutting off building fire protection systems 

should be studied. Building owners or operators currently have the 

authority and ability to shut off a system. Normally, this is done by 

the building engineer or head of maintenance, but following the 2014 

FEMA P-1024 10: Performance of Nonstructural Components 10-33 
2. 

3. 

4. 

South Napa earthquake, few, if any, individuals knew how to do 

it. Owners and operators should designate someone on site and give 

them a key to the lock with the responsibility of turning off the water 

supply should sprinkler systems suffer damage and start releasing 

water. A good emergency plan designates alternates for each 

responsibility, including control of the sprinkler system. 

o	 Where sprinkler heads are connected to a ceiling, use of flexible 

piping between the branch line and sprinkler head (sprinkler drops) 

may reduce the potential for damage. Shake table testing has 

established the effectiveness of flexible sprinkler drops. 

o	 Threaded iron sprinkler pipe fittings provide little ductility, and have 

a high risk of leaking in moderate ground shaking and fracturing in 

strong shaking. The performance of different types of fire sprinkler 

piping, connections and bracing should be investigated. 

Recommendations for approaches to reduce the potential for pipe 

breaks and the probability of unintended water release should be 

researched and developed. Consideration should be given to 

investigating new technologies or approaches to improved seismic 

performance. 

o	 The interaction of fire sprinkler piping with other MEP components 

warrants further study. The current practice of using unbraced 

sprinkler drops and armovers may be contributing to adverse 

interactions, as well as failure to specify adequate clearance between 

piping and other components. The role of bracing or other means to 

prevent damaging interactions should be explored. Also, the 

importance of maintaining clearances with other obstructions is 

critical and standard requirements need to be maintained. 

The adequacy of code provisions for pendant lighting fixtures, especially 

those with multiple points of support, should be examined. Engineering 

analysis should be used be used to predict the performance of a pendant 

system. As an alternative, shake table testing should be considered as a 

means to validate its performance. 

The adequacy of current code requirements for design and inspection of 

adhered veneer should be examined. Acceptable postearthquake 

performance states should be defined. 

The adequacy of current code requirements for exterior cladding should 

be studied, especially for adhered foam-backed veneer. The code 

requirement to “accommodate” story drift should be clarified by 

establishing performance expectations for exterior cladding. As a 

10-34	 10: Performance of Nonstructural Components FEMA P-1024 
minimum, clarifying language should be considered for the commentary 

to the code. Engineers and building officials should ensure that cladding 

connections are specifically detailed to accommodate building drift and 

seismic demands, and field inspections should be performed to verify 

that the connections are properly constructed. Best practice guidance 

should be developed to illustrate the issues and possible solutions for 

various types of cladding systems. 

5.	 Guidelines for the installation of rooftop piping and conduit should be 

developed. The building code does not explicitly address this issue and 

simple construction measures could avoid costly postearthquake repairs. 

6.	 The adequacy of code requirements to protect glazing from damage 

should be investigated. This is particularly true for building systems and 

seismic retrofitting techniques, such as moment frames, that experience 

significant amounts of drift during an earthquake. 

7.	 Some furnishings and contents not regulated by the building code pose 

seismic safety risks. The public should be made aware of these risks 

and, as a minimum, voluntary installation of seismic restraints should be 

encouraged, particularly for slender items, such as bookcases. 

Approaches for promoting a culture of seismic safety should be explored. 

8.	 Installation of MEP equipment is often completed without inspection by 

a Building Official or design professional. Approaches for requiring 

equipment inspections during construction should be explored. The 

impact of damage to contents and furnishings on emergency egress 

should be investigated. 

9.	 Architects, mechanical engineers, plumbing engineers, electrical 

engineers, fire protection engineers, information technology (IT) 

consultants, and others associated with nonstructural components should 

be trained to better understand the seismic performance implications of 

improperly designed or installed nonstructural components. 

10. Damage to interior partitions was generally less than predicted by 

researchers. This is of interest in the field of earthquake damage 

estimation, where high levels of partition damage are predicted using 

current partition fragility data. The performance of gypsum wallboard 

and plaster partitions should be studied to better understand their 

vulnerability and to recommend detailing to reduce the potential for 

costly damage. 

11. The adequacy of code design requirements can be effectively evaluated 

with measurements of actual floor and roof accelerations and 

FEMA P-1024 10: Performance of Nonstructural Components 10-35 
displacements. Installation of strong motion recording devices 

throughout buildings should be encouraged. 

10-36 10: Performance of Nonstructural Components FEMA P-1024
 
 

Chapter 11 

 Postearthquake Safety 

Evaluation of Buildings 

11.1 Introduction 

In the aftermath of an earthquake, one of the most important steps taken is 

the safety evaluation of the community building stock. Buildings that have 

been damaged and pose a potential safety threat are identified and posted to 

restrict or prohibit use. Of equal importance, and a vital step towards 

maintaining the life of the community, is identifying those buildings that are 

safe to occupy. Because significant events like the 2014 South Napa 

earthquake affect thousands of buildings, safety evaluations must be done in 

a rapid and efficient manner. This chapter summarizes how the safety 

evaluations were managed and implemented with a focus on the City of Napa 

where the majority of urban damage was concentrated. In general, the 

process of conducting the postearthquake evaluations went smoothly, and the 

rapid response of the local authorities facilitated the recovery of the 

community. As might be expected in the aftermath of significant natural 

disaster, some inconsistencies in the procedures occurred. In this chapter, 

observations of the placarding process and issues that were encountered 

during the postearthquake damage evaluations are discussed. 

Following the earthquake, buildings were evaluated to determine if they were 

safe to occupy and then posted (or placarded or tagged) using the procedures 

in ATC-20-1 Field Manual: Postearthquake Safety Evaluation of Buildings 

(ATC, 2005). The postearthquake evaluation process in ATC-20-1 has three 

levels of placards defined as follows. 

	 INSPECTED (green): No apparent hazard is found, although repairs may 

be required. The original seismic resistance is not significantly 

decreased. No restriction on use or occupancy. 

	 RESTRICTED USE (yellow): A hazardous condition exists (or is 

believed to exist) that requires restrictions on the occupancy or use of the 

structure. Entry and use are restricted as indicated on the placard. 

	 UNSAFE (red): Extreme structural or other hazard is present. There may 

be imminent risk of further damage or collapse from creep or 

FEMA P-1024	 11: Postearthquake Safety Evaluations 11-1 
 

aftershocks. Unsafe for occupancy or entry, except as authorized by the 

local building department. 

11.2 Postearthquake Safety Evaluation Program 

Management 

Building safety evaluations following a disaster in the United States are 

managed using the National Incident Management System (NIMS), a 

systematic tool developed by FEMA and used for the command, control, and 

coordination of emergency response. All aspects of the disaster response are 

coordinated through this system. Incidents are typically managed at the 

lowest possible geographical, organizational, and jurisdictional level. In 

instances where success depends on the involvement of multiple 

jurisdictions, levels of government, functional agencies, or emergencyresponder disciplines, NIMS provides for effective and efficient coordination 

across a broad spectrum of organizations and activities. The implementation 

of the NIMS process in California is coordinated by the Office of Emergency 

Services for the State of California (Cal OES), using their Standardized 

Emergency Management System (SEMS) protocol. 

It is also worth noting that several cities, including San Francisco and Los 

Angeles, have developed or are in the process of developing and 

implementing Building Occupancy Resumption Programs (BORP) that are 

based on the idea of a city deputizing licensed structural engineers to 

investigate buildings and develop a plan with building owners before an 

earthquake. Following an event, armed with prior knowledge of the facility 

and up-to-date building drawings and documentation, the structural engineer 

can immediately assess the safety of the building and allow re-occupancy or 

more quickly begin the shoring up and repair process. A BORP program was 

not in place in areas affected by the South Napa earthquake. 

Following the earthquake, safety evaluations were conducted by local 

building department staff along with volunteers, mutual aid, and state 

personnel provided through Cal OES. The following sections provide a 

summary of how evaluations were managed. 

11.2.1	 Response of Cal OES 

Cal OES coordinates the process of providing safety assessment program 

evaluators trained in postearthquake safety evaluations. Cal OES maintains a 

database of approximately 6,000 Safety Assessment Program (SAP) 

evaluators who have completed a training program based on ATC-20-1 and 

have registered as Disaster Service Worker (Barnes, 2014). 

11-2	 11: Postearthquake Safety Evaluations FEMA P-1024 
 

 

The earthquake occurred on Sunday, August 24, 2014 at 3:20am. In 

accordance with the state’s SEMS protocol, later that day Napa County 

requested assistance from Cal OES for the City of Napa, the City of 

American Canyon, and the County itself; Solano County requested assistance 

for the City of Vallejo and the County itself. Sonoma County did not request 

assistance. Safety Assessment Program evaluators are state employees, local 

government employees such as building inspectors, and volunteers. Cal OES 

assessed the requests and then contacted organizations that partner with Cal 

OES including the Structural Engineers Association of California (SEAOC), 

the American Institute of Architects (AIA), the American Society of Civil 

Engineers (ASCE), the California Building Officials (CALBO), and the 

American Construction Inspection Association (ACIA). 

At SEAOC, the contact for Cal OES is the chair of the State Disaster 

Emergency Services (DES) Committee. SEAOC has four local member 

organizations with parallel committees: the Structural Engineers Association 

of Northern California (SEAONC), Structural Engineers Association of 

Central California (SEAOCC), Structural Engineers Association of Southern 

California (SEAOSC), and Structural Engineers Association of San Diego 

(SEAOSD). The state SEAOC DES chair contacted the local DES chairs 

with the request for assistance, with a preference for SEAONC volunteers 

based on the size and location of the earthquake. The local chairs then 

emailed members in their organization who have certification and were on 

the volunteer list. 

SEAOC provided volunteers immediately following the request and 

continued to provide volunteers for approximately two weeks after the 

earthquake. In the end, SEAONC provided about 20 volunteers, and the total 

number of volunteers from for the four member organizations in SEAOC was 

approximately 60. 

After the first week, the City of Napa began requesting only CALBO 

personnel. CALBO responded with numerous SAP evaluators, but due to 

problems with communication, it became difficult to obtain SAP evaluators 

from CALBO over the entire ten-week span of activation. Cal OES then 

requested SAP resources from the California Office of Statewide Health 

Planning and Development (OSHPD) to complete the activation. It is noted 

that civil engineer SAP evaluators from the California Department of 

Transportation (Caltrans) also assisted in this activation. 

FEMA P-1024 11: Postearthquake Safety Evaluations 11-3 
 

11.2.2	 Response of City of Napa 

Postearthquake safety evaluations in the City of Napa were managed by the 

Building Department, under the direction of the Chief Building Official. 

The City of Napa provided status reports on the process of evaluations (City 

of Napa, 2014a and b) on the city’s website. As of 5pm on August 25, 2014, 

70 buildings were placarded as UNSAFE and the number of buildings with 

RESTRICTED USE placards was approaching 200. There were 60 

inspectors working to evaluate structures. By September 5, 2014, there were 

125 buildings posted UNSAFE and 1,036 buildings posted RESTRICTED 

USE. For several months following the earthquake the City of Napa 

periodically posted a GIS map of structures with UNSAFE and 

RESTRICTED USE placards on a website (this website is not available 

anymore). 

11.2.3	 Response of City of Vallejo 

Safety evaluations in the City of Vallejo were managed by the local Building 

Department. As of September 17, 2014, 404 structures had been posted 

RESTRICTED USE, and 34 structures had been posted UNSAFE. In total 

1,075 properties were inspected (City of Vallejo, 2014). 

11.2.4	 Response of the Office of Statewide Health Planning and 

Development 

Safety evaluations for healthcare facilities were managed by OSHPD, which 

has a statutory responsibility to perform postearthquake safety evaluations. 

Details on healthcare facility building evaluation efforts are included in 

Chapter 5. OSHPD also responded to mutual aid requests from the cities of 

Napa and Vallejo. They also responded to a request from three stateoperated facilities that provide long-term care for veterans, individuals with 

developmental disabilities, and individuals mandated for psychiatric 

treatment by a criminal or civil court judge. The following placards were 

posted: 

 Veterans Home of California in Yountville: Six INSPECTED placards. 

 Napa State Hospital: This older facility provides mental health 

treatment. One UNSAFE placard; eight RESTRICTED USE placards; 

and 49 INSPECTED placards. The UNSAFE placard was posted on an 

unoccupied unreinforced masonry building. RESTRICTED USE 

placards were generally posted on structures with potential damage to 

masonry chimneys, damage to structural walls or bracing 

 Sonoma Developmental Center: 21 INSPECTED placards. 

11-4	 11: Postearthquake Safety Evaluations FEMA P-1024 
 

At the peak, OSHPD provided 30 staff members in response to mutual aid 

requests. 

11.2.5	 Response of the Napa Valley Unified School District 

Safety evaluations for schools were addressed by several agencies. K-12 

schools in California are regulated by the Division of State Architect (DSA). 

Unlike OSHPD, DSA does not have regulatory authority to inspect schools 

after an earthquake unless there is a local request. Local requests were not 

made, so DSA structural engineers did not review school buildings after the 

event (Barnes, 2014; Turner, 2014). 

In the Napa Valley Unified School District, district officials set up teams of a 

district official, a local architect, and a local structural engineer. The school 

district also retained mechanical and electrical engineering consultants to 

inspect each school site and recommend repairs, where needed. Evaluations 

began on the day after the earthquake. Details on building evaluation efforts 

are included in Chapter 6. 

11.3 Conduct of the Postearthquake Safety Assessment 

Program 

While all of the jurisdictions followed the general procedures of ATC-20-1 

for their building evaluations, there were variations in the application of the 

methodology, which are discussed in this section. 

11.3.1	 Use of Evaluation Forms 

There were some differences observed in how the ATC-20-1 safety placard 

system was used by different jurisdictions in this event. In some cases, 

LIMITED USE (Yellow) placards were issued for buildings not necessarily 

to limit access, but apparently more to document damage to ensure that 

repairs would be made. In these cases, the placard did not list any access 

restrictions but instead appeared to be used as an administrative tool to 

inform the owner that repairs of the documented damage were needed before 

the placard would be removed. This prevented people from occupying the 

building without the proper repairs having been made. 

In Vallejo, the placards were based on the ATC-20-1 forms (with the City of 

Vallejo logo added), but the ATC-20-1 assessment forms were not used. 

Instead, City of Vallejo inspectors used simplified forms that were not 

necessarily consistent with the placard. These were revised as the process 

proceeded until the assessment form began to look similar to the ATC-20-1 

assessment form. 

FEMA P-1024	 11: Postearthquake Safety Evaluations 11-5 
 

11.3.2 Assignment of Resources 

In both Napa and Vallejo, structural engineers were often assigned to 

evaluate single-family residences, rather than the larger, more complicated 

urban structures. 

Although ATC-20 evaluations can be conducted by anyone with proper 

training and registration in the State’s program, using the limited resource of 

available experienced structural engineers for more complicated structures is 

recommended. ATC-20-1 presents three evaluation procedures: Rapid, 

Detailed, and Engineering. The first two are used as part of the 

postearthquake assessment process. The proportion of Rapid versus Detailed 

Evaluations conducted is not known, but it is assumed that the vast majority 

were Rapid Evaluations. ATC-20-1 recommends that Detailed Evaluations 

be conducted by structural engineers. 

11.3.3 Compensation of Safety Assessment Program Evaluators 

Initially, the local jurisdiction requesting assistance is responsible for 

compensating Safety Assessment Program evaluators. Eventually, if a 

formal disaster declaration is made, the local jurisdiction can make a request 

to recoup the costs of compensation. Volunteer evaluators, such as those 

from SEAOC or AIA, donate their time, but travel and lodging expenses are 

reimbursed by the city requesting the help. Compensation for government 

employees, such as local building officials from other jurisdictions or 

agencies, serving as safety assessment program evaluators are provided 

through mutual aid. This is a significant difference, so initial requests are 

usually aimed at volunteer evaluators. 

11.3.4 Local Ordinance Authorization for Placarding 

In theory, a local community should have an ordinance that formally 

authorizes the postearthquake safety evaluation process and use of placards. 

It was reported that the City of Vallejo had such an ordinance, but the City of 

Napa only had a model ordinance (not enforced) (Barnes, 2014). Placards 

typically also carry the logo of the local jurisdiction. In the City of Napa, 

placards were observed with and without the City of Napa logo, though they 

matched the forms in ATC-20-1. 

11.4 Observations 

The postearthquake safety evaluation process generally appeared to meet the 

goals of providing rapid information on whether buildings in the affected 

area were safe to occupy. Using GIS technology, the status of the 

postearthquake inspections in Napa was accessible to the public online. In 

11-6 11: Postearthquake Safety Evaluations FEMA P-1024 
 

general, the process went smoothly, and buildings were evaluated in a timely 

manner. Some issues did arise, especially following the initial safety 

assessments when buildings were being reevaluated, and are discussed in this 

section. 

11.4.1 Multiple Postings 

Many buildings in Napa received follow-up evaluations and the buildings 

were reposted with a different placard. However, in some cases, the 

superseded placard was not removed. Figure 11-1 shows an example of an 

UNSAFE placard placed over an INSPECTED placard. The INSPECTED 

placard had the City of Napa logo; the UNSAFE placard which came later 

did not. This could cause confusion over which placard takes precedence. 

ATC-20-1 notes that there can be only one posting classification for a 

building and that all entrances should receive the same placard. Some 

buildings in Napa were observed to have an INSPECTED placard at one 

entrance and a RESTRICTED USE placard at another entrance. Those 

entering through the entrance posted INSPECTED thus may not have been 

aware of the restrictions in areas of danger. 

Figure 11-1 A building with multiple placards. 

FEMA P-1024 11: Postearthquake Safety Evaluations 11-7 
 

 

11.4.2 Inappropriate Use of Placards 

The purpose of the RESTRICTED USE placard is to restrict use to local 

areas of the building with significant damage. The restrictions need to be 

documented on the placard so that building occupants understand the 

limitations. Figure 11-2 shows an example of a proper use of the 

RESTRICTED USE placard at a building where an area with falling hazards 

had been taped off and access was restricted to selected entrances. 

Figure 11-2 A RESTRICTED USE tag with restrictions noted as “Public may 

enter. Stay clear of taped off areas and construction.” 

However, a number of RESTRICTED USE placards had minimal or no 

information on the restrictions (Figure 11-3 shows an example), reducing the 

effectiveness of the placard. 

Figure 11-4 shows an INSPECTED placard that was placed on the rear 

entrance of a building where access to the front entrance was restricted due to 

a significant falling hazard. A RESTRICTED USE placard should have been 

placed at both entrances clearly identifying the restrictions. 

Figure 11-5 shows a RESTRICTED USE placard on a restaurant with falling 

hazards. Outdoor seating adjacent to the placards was restricted, “except 

during the following times: (1) Monday – Friday, 4:30pm to closing, (2) 

Saturday to Sunday – All Day.” The restrictions should never relate to when 

the restaurant is open, but rather to the hazard itself. Placing exceptions for 

11-8	 11: Postearthquake Safety Evaluations FEMA P-1024 
 

specific times is inappropriate and in this case potentially endangers patrons 

during the busier times. 

Figure 11-3 A RESTRICTED USE placard with no information on the 

restrictions. 

Figure 11-4 An INSPECTED placard on a building with another exit that is 

still restricted. A RESTRICTED USE placard should have been 

used. 

FEMA P-1024	 11: Postearthquake Safety Evaluations 11-9 
 

Figure 11-6 shows a building with an UNSAFE placard with a separate sign 

from the landlord implying that the landlord could grant permission to the 

space despite the UNSAFE placard. As the UNSAFE placard indicates, 

entry is not permitted except in writing by the local jurisdiction, not the 

owner. 

Figure 11-5 A RESTRICTED USE placard with exemptions permitting access 

while the restaurant is open. 

Figure 11-6 An UNSAFE placard with an adjacent inconsistent placard by 

the owner. 

11-10 11: Postearthquake Safety Evaluations FEMA P-1024 
 

11.4.3	 Inconsistent Communication with the Public Regarding 

the Meaning of the Placards 

The public often has questions about the meaning of the placard language, 

and what steps they should take after receiving a placard. A website was 

established to provide information relevant to the City of Napa and Napa 

County, http://www.napaquakeinfo.com/tag-information.html (accessed 

November 25, 2014). The website states that for the City of Napa, the “tags” 

(placards) have the following meanings: 

	 Red Tag: A red tag means the building structure has been damaged and 

is not safe to enter. Please do not enter your building. 

	 Yellow Tag: A yellow tag means “cautionary.” Property owners can 

access and clean their buildings, and once clean can contact the City for 

re-inspection. 

	 Green Tag: A green tag means that either the building has not been 

affected or has slight damage. The building is structurally safe to enter. 

For Napa County, the website states that the tags have the following 

meanings: 

	 Red Tag: A red tag means the building structure has been severely 

damaged and it is no longer safe. Please do not enter the building. 

	 Yellow Tag: 

o	 A yellow tag means that the building has been moderately damaged. 

Use of the building is limited. 

o	 Residents may continue to live in a home that has a 

yellow tag, but they may have to avoid damaged areas. 

o	 Commercial properties may be entered for the purposes of clean-up 

and repair, but may not be opened to the public. 

o	 The yellow tag cannot be removed by the County until the damage 

has been repaired and passed inspection. 

	 Green Tag: A green tag means that either the building has not been 

affected or has slight damage. The building is structurally safe to enter. 

The information for UNSAFE (red) and INSPECTED (green) placards is 

consistent with ATC-20-1 for both jurisdictions. However, for both 

jurisdictions, the information for the RESTRICTED USE (yellow) is not 

consistent with ATC-20-1. According to ATC-20-1, all restrictions on use 

should be noted on the placard and should indicate areas that are not safe for 

entry. The information for Napa County is more nuanced, but the prohibition 

FEMA P-1024	 11: Postearthquake Safety Evaluations 11-11 
 

of public access to a commercial building with a RESTRICTED USE placard 

may be overly restrictive. As noted above, the placard should identify the 

areas that are restricted and those that are not. 

The City of Vallejo’s website (http://vallejo.hosted.civiclive.com 

/cms/one.aspx?objectId=99620, accessed December 1, 2014) provided the 

following information: 

	 Red Tag: A red tag means the building structure has been damaged and 

is deemed unsafe to enter and occupy. Please do not enter your building. 

	 Yellow Tag: A yellow tag means “restricted use” or “limited access.” 

Property owners can access, clean, remove possessions and abate 

imminent hazards in their building, and once clean can contact the City 

for re-inspection. 

	 Green Tag: A green tag means the building has not sustained structural 

damage or has minor damage. The building is structural safe to enter. 

The information for UNSAFE (red) and INSPECTED (green) placards is 

consistent with ATC-20-1. The information for the RESTRICTED USE 

(yellow) is not. Again, all restrictions on entry and use should be noted on 

the placard. 

11.5 Summary 

In the aftermath of the 2014 South Napa earthquake, each jurisdiction 

responded to the need to evaluate the safety of buildings in the impacted 

region, using the resources they had available. In general, the process went 

smoothly, and buildings were evaluated in a timely manner. However, there 

were significant variations in evaluation and placarding procedures among 

the different jurisdiction. The definitions provided to the public by 

jurisdictions on the meaning of the RESTRICTED USE placard were 

inconsistent with the intent of the ATC-20-1 procedures, and varied 

significantly by jurisdiction. 

In some cases, the placarding of the buildings was not clear, with current and 

superseded placards posted on the same entrance. This could present a 

potentially hazardous condition, because in several instances the building 

was initially posted INSPECTED (safe to occupy) and subsequently posted 

UNSAFE. Postings at different entrances of a building were not always 

consistent, and in some cases, a person entering through one entrance would 

be unaware of a hazardous condition in the building, because there was a 

different placard at the door they entered. 

11-12	 11: Postearthquake Safety Evaluations FEMA P-1024 
 

11.6 Recommendations 

A number of areas for improvement in the postearthquake damage evaluation 

program were identified, including: 

1.	 Use of the ATC-20-1 evaluation forms and procedures as written is 

strongly recommended. The evaluation procedures are the product of 

extensive development, testing, and experience and they should not be 

modified or abridged. 

2.	 A document should be developed to provide guidance to local 

jurisdictions on how to provide effective management of the 

postearthquake safety evaluation process and incorporate common issues 

and lessons learned from those who have been directly involved in the 

process. This document could include discussion and recommendations 

on: 

o	 Appropriate use of evaluation forms, together with placards. 

o	 Best practices for assigning safety assessment program volunteers 

with varying degrees of experience and training. While ATC-20-1 

evaluations can be conducted by anyone with proper training and 

registration in the State’s program, using the limited resource of 

available experienced structural engineers for more complicated 

structures is recommended. ATC-20-1 recommends that Detailed 

Evaluations be conducted by structural engineers. 

o	 Quality assurance techniques should be outlined to provide 

consistent evaluation and placarding decisions and to reduce misuse 

of placards. 

o	 Recommendations on implementing language for local ordinances to 

formally authorize the evaluation and placarding process. 

3.	 A document should be developed to provide guidance for communities in 

how to communicate the placard requirements to citizens. Common 

misunderstandings, particularly related to the RESTRICTED USE 

placard, should be discussed. 

4.	 Placarding should be consistent for each building, and copies of the 

placard should be placed at all entrances. No building should have 

different placards at different entrances. 

5.	 Only the most current placard should be posted. Superseded placards 

should be removed, and all entrances to the building should be posted 

with the most current placard. 

FEMA P-1024	 11: Postearthquake Safety Evaluations 11-13 
 

6.	 RESTRICTED USE placards should never include provisions that permit 

the public to be exposed to hazardous conditions based on the time of 

day. Public use should be prohibited until the hazardous condition in 

that location is mitigated. 

7.	 Postearthquake evaluation training should be updated to address the 

commonly observed issues as noted above. Building Occupancy 

Resumption Programs should be considered for supplementing limited 

city resources and facilitate postearthquake recovery. 

8.	 It was observed that because there is no requirement to pay the salaries 

of volunteer evaluators (as opposed to building officials from other 

jurisdictions paid through mutual aid), initial requests were typically 

aimed at volunteer evaluators. Wider discussion of the appropriateness 

of this situation is worth discussing in the building community. 

11-14	 11: Postearthquake Safety Evaluations FEMA P-1024 
 

Chapter 12 

Barricading of Unsafe Areas 

Following the 2014 South Napa earthquake, barricades and fencing were 

installed around damaged buildings to protect pedestrians, traffic, and 

adjacent buildings. This chapter summarizes selected observations related to 

barricades and fencing and related guidelines and codes. 

12.1 Available Resources 

ATC-20-1, Field Manual: Postearthquake Safety Evaluation of Buildings, 

(ATC, 2005) provides limited guidance on barricades but does not provide 

details of design and location of barricades and fencing. 

Following review of the 2010 and 2011 earthquakes in Christchurch, New 

Zealand, the development of guidelines for barricades and cordons was 

identified as a high priority. As a result, the volunteer members of California 

Building Officials (CALBO) developed the Interim Guidance for 

Barricading, Cordoning, Emergency Evaluation and Stabilization of 

Buildings with Substantial Damage in Disasters (CALBO, 2013). The 

Guidelines note that requirements in California Building Code Chapter 33, 

Safeguards During Construction, apply only to stable buildings under 

construction and not unstable, damaged buildings. The Guidelines 

recommend initial placement of soft barriers, such as fencing, at horizontal 

distances (H) up to 1.5 times the height (V) of the façade or structure at risk, 

termed a 1.5H:1V setback, “to allow for the possibility that falling items can 

bounce and shatter.” Wide safe distances including block-long cordons are 

warranted until inspectors, Safety Assessment Program (SAP) evaluators, 

building owners, engineers, contractors, and other agents can evaluate, 

stabilize, or remove potential falling or collapse risks and erect hard, impactresistant barriers to protect the public. 

It is noted that the Guidelines are permissive and can be adapted to the 

unique circumstances of every damaged structure. For example, a 7-story 

100-foot tall building with a damaged appendage at the second floor need not 

be barricaded to 150 feet out, whereas for a unreinforced masonry (URM) 

building with a damaged parapet at the roof level, the full setback of 1.5 

times the building height would be appropriate. For some multi-story 

buildings, the setback distance may be larger than the width of the sidewalks 

and street in front of the building. In cases perpendicular to the street or for 

FEMA P-1024 12: Barricading of Unsafe Areas 12-1 
 

rear walls, there may be adjacent buildings abutting the damaged building 

with no separation. To achieve the required setback distance, the adjacent 

building would have to be cordoned off, as well. The Guidelines note that 

the locations and types of barriers, barricades, and cordons can be refined as 

situational awareness improves during recovery. 

Another available resource is the Safety Assessment Program Coordinator 

Student Manual (Cal OES, 2013), which discusses issues related to 

cordoning and barricades. 

12.2 Observations and Issues 

Damage in the downtown business district of the City of Napa was 

substantial, and barricading and fencing were an important aspect of the 

recovery process. It appears that there were at times two conflicting 

priorities: (1) barricading around damaged buildings to protect the public 

from falling debris, especially in an aftershock, and (2) keeping the streets 

open so that owners and customers could still reach those businesses that 

were able to remain open. Given that the primary economy of the downtown 

Napa area is tourism, it is understandable that the City did not want to cause 

further economic hardship by closing off entire streets. However, safety 

must remain a top priority. It is fortunate that the number and size of 

aftershocks were much smaller than expected. 

Based on field visits and discussions with others, several issues with 

barricades were identified. 

12.2.1 Initial Barricade Distances 

In some cases, it was observed that initial barricades were inadequately 

spaced from damaged buildings. Figure 12-1 shows an unreinforced 

masonry (URM) building with an UNSAFE placard and significantly 

damaged masonry façades, with a fence only several feet from the building 

(much less than the 1.5 times the vertical height), with the street allowed to 

remain in full operation. 

Figure 12-2 shows a church with a gable wall separated from the roof 

diaphragm where the fence was set back some distance into the street, but 

less than the 1.5H:1V setback threshold. 

There were some streets that were closed in downtown Napa due to the 

falling hazards from damaged buildings, but typically only the sidewalks and 

portions of the street were fenced off, usually at a distance of much less than 

1.5 times the height of the falling hazard. Figure 12-3 shows a street that was 

12-2 12: Barricading of Unsafe Areas FEMA P-1024 
 

partially closed due to damage of the adjacent building. Prior to removal of 

the damaged roof over the cupolas, the entire street had been closed. 

There were also some adjacent buildings where access was restricted due to 

damage in the adjoining structure though the buildings were not cordoned 

off. 

Figure 12-1 A building with an UNSAFE placard where the fence setback 

was much less than a 1.5H:1V setback distance. 

Figure 12-2 Church with damaged gable façade where the fence setback 

was less than a 1.5H:1V set back distance. 

FEMA P-1024 12: Barricading of Unsafe Areas 12-3 
 

Figure 12-3 	 Partial street closure. Prior to removal of the damaged roof 

cupola, the entire street was closed. 

12.2.2 Transitions to Longer-Term Barricades 

As time passed and damage could be better evaluated, the barricades and 

fencing strategies evolved. A common approach while repairs were being 

made was to install scaffolding in front of the damaged building façades. To 

limit the visual impact, plastic fencing was usually part of the installed 

scaffolding (Figure 12-4). Reportedly, scaffolding was not engineered and 

not anchored or attached to the building it was barricading. Although it is 

likely that the scaffolding and screening would stop small pieces of masonry 

and other cladding materials from falling outward, given the relative mass of 

many of the damaged structures with URM façades, it is not obvious that the 

scaffolding would be effective in preventing a failing wall from falling on the 

sidewalk or street. 

In at least one case, a windstorm damaged a lightweight scaffolding system 

placed adjacent to a damaged URM side wall (Figures 12-5 and 12-6). The 

lightweight system was later replaced with a more robust scaffolding system 

(Turner, 2014). 

To keep bystanders from breeching a fenced area, some of the longer-term 

barricades used smooth plywood walls of around eight feet in height that 

could not be easily scaled without a ladder. 

12-4 12: Barricading of Unsafe Areas FEMA P-1024 
 

Figure 12-4 Scaffolding used as a barricade on damaged URM building. 

12.2.3 Exiting into Cordoned Areas 

In some instances, buildings with RESTRICTED USE placards had certain 

exits below damaged masonry gable walls. Yellow caution tape was used 

around the area (at far less than the 1.5H:1V distance) and the door had a 

RESTRICTED USE placard on the outside. However, there was no warning 

sign on the interior of the door, and staff was observed taking breaks within 

the cordoned area using the exit. Since the building remained in use as a 

restaurant, diners and staff in an emergency might use this exit and walk 

directly into a potential falling hazard zone from the damaged gable above. 

Figure 12-5 Scaffolding used as a barricade damaged in a windstorm (photo 

by Fred Turner). 

FEMA P-1024 12: Barricading of Unsafe Areas 12-5 
 

 

Figure 12-6 Replacement scaffolding following the windstorm (photo by 

Fred Turner). 

12.2.4 Protecting Adjacent Buildings 

In one instance, an unretrofitted URM building was severely damaged and 

posted UNSAFE as a result of damage to brick walls. There were four 

shorter undamaged buildings immediately adjacent to it that were also posted 

UNSAFE due to risk of collapsing masonry walls striking their rooftops 

(Refer to Section 4.4.1). In order to allow occupancy in the adjacent 

buildings, the City of Napa required barriers to be constructed over the 

adjacent rooftops to prevent any falling bricks from penetrating the roofs and 

posing a safety risk to building occupants (Figure 12-7). With the protective 

barriers in place, the adjacent buildings were reposted INSPECTED and were 

opened for business. 

12.3 Summary 

In the period immediately following the earthquake, damage evaluations are 

performed rapidly, and because they are based on limited information, they 

are expected to be conservative. Local officials have to decide between two 

contending priorities: to protect the public from the hazards posed by 

damaged buildings while minimizing the impact of the earthquake on homes 

and businesses, by allowing the public access to undamaged structures as 

soon as possible. 

The general guidelines for barricading and fencing of damage buildings that 

were available at the time of the South Napa earthquake are permissive, and 

substantial variations in the fencing and barricading distances were observed 

following the earthquake. For buildings with parapet and façade damage, 

12-6 12: Barricading of Unsafe Areas FEMA P-1024 
 

Figure 12-7	 Protective barrier constructed over the rooftops of buildings to 

protect from falling brick. 

which were fairly widespread in the downtown area, the recommended 

setbacks for the fences were rarely enforced. No hard, impact-resistant 

barriers were installed. The setbacks were typically determined by an 

assessment of the falling hazard risk posed by the structure, or by other 

criteria, such as the desire to maintain or reopen rigths of way, minimize 

disruption, and speed recovery. In some instances, exit paths for buildings 

passed under damaged façades, even though from the exterior, the area was 

cordoned off. So it appeared that the Guidelines were not fully implemented 

and the public was not uniformly protected from falling hazards in 

aftershocks. Furthermore, trained SAP Coordinators were not involved with 

ensuring that barricades recommended by SAP personnel were effectively 

erected. 

12.4 Recommendations 

The experience with barricading damaged buildings in the South Napa 

earthquake suggests several areas for possible improvement and further 

study, including: 

1.	 The effectiveness of scaffolding and other types of barricades in 

providing life safety protection against various types of falling hazards is 

not well understood. A research project is recommended to compare the 

effectiveness of various forms of scaffolding and barricading against 

different falling hazards. This could include smaller and larger masonry 

FEMA P-1024 12: Barricading of Unsafe Areas 12-7 
 

elements from different heights. Guidance should be provided to assist 

engineers with design of barriers to protect against damage posed by 

falling masonry. 

2.	 Further development of consensus guidelines, such as Interim Guidance 

for Barricading, Cordoning, Emergency Evaluation and Stabilization of 

Buildings with Substantial Damage in Disasters, into a formal document 

is recommended and should involve various stakeholders and 

professionals with relevant expertise. This work should include 

discussion about protection not just of the public way, but also adjacent 

buildings in potential danger from damaged structures. 

3.	 The local authority having jurisdiction should establish criteria for the 

placement of barricades and fencing around damaged buildings that 

allows for some flexibility based on easily identifiable conditions. This 

would establish baseline requirements that could be followed 

consistently following an earthquake. 

4.	 Where occupancy is granted for a structure that has damaged elements 

posing as falling hazards, there should be follow-up site visits by the 

local building or fire authorities to confirm that limited access and 

barricading requirements are being followed. 

12-8 12: Barricading of Unsafe Areas FEMA P-1024 
Chapter 13 

 Summary and Conclusions 

The August 24, 2014 South Napa earthquake struck early in the morning, 

which greatly reduced the potential for serious casualties. Had the 

earthquake struck 12 hours earlier during a downtown street festival, this 

would have been a far different story. No building sustained complete 

collapse, but a number of older structures experienced partial collapse or 

serious structural damage. Falling masonry from damaged buildings in 

downtown Napa would have posed a serious threat to life. 

Damage to nonstructural components was by far the greatest contributor to 

property damage. Secondary damage due to failures of water piping and fire 

sprinkler systems was serious, often resulting in extensive losses to buildings 

that otherwise suffered only minor damage. Although of only moderately 

strong intensity, the South Napa earthquake provides a significant 

opportunity for study of building performance and the effectiveness of 

seismic hazard mitigation efforts. 

Performance data were collected and analyzed systematically for buildings 

located in the vicinity of strong-motion recording instrument USGS NCSN 

Station N016 at Main Street in Napa. This is an effective means of rapidly 

collecting building performance data and should be implemented after every 

significant earthquake. 

Buildings constructed to recent codes generally performed well structurally, 

although many buildings suffered some nonstructural damage. Older 

structures not of unreinforced masonry (URM) construction performed well 

structurally, although known vulnerabilities did in some cases result in 

significant damage and loss of use. 

Buildings of URM construction make up 40% of the buildings surveyed 

within 1,000 feet of instrument N016, and over two-thirds of the URM 

buildings had been seismically retrofitted prior to the earthquake. Based on 

the performance of these buildings, the URM risk mitigation efforts in Napa 

were successful in reducing damage and protecting life safety. Unretrofitted 

URM structures continue to pose significant risks to the public and efforts 

should be made to reduce the risks posed by these buildings. 

FEMA P-1024 13: Summary and Conclusions 13-1 
Although the hospital nearest the epicenter remained open and functional, it 

did highlight some of the challenges associated with sustaining hospital 

operations following an earthquake. Both new and older hospital buildings 

experienced some nonstructural damage which, in a larger earthquake with 

longer duration, could have impacted the continuity of service. 

Schools performed well structurally, but they experienced nonstructural 

damage that could have been life threatening had the earthquake occurred 

during school hours. The earthquake highlighted the danger posed by 

pendant light fixtures, unrestrained bookcases, storage units, and similar 

components that overturned in the earthquake, often striking tables and 

desks. These items are generally not covered by the building code, and a 

special effort will be needed to reduce the hazards posed by these items. 

Classrooms should be examined on an annual basis to ensure that furnishings 

and contents are properly anchored and braced. Such an inspection program 

could be tied to the annual ShakeOut drill that almost all schools now 

perform. All schools, not just public schools, should implement measures to 

enhance seismic safety. 

The overwhelming majority of residences affected by the South Napa 

earthquake suffered little damage. The performance of single-family 

residences is consistent with the prior observations that light-frame 

residential construction generally performs well, provided that known 

hazardous conditions are either not present or have been mitigated. 

Continued efforts to increase the awareness of the public of the hazards 

presented by masonry chimneys and unbraced cripple walls are needed. The 

fault rupture passed through some residential neighborhoods, damaging 

homes that otherwise would be expected to perform well, and the afterslip 

observed in the days after the earthquake continues to be an issue. 

Manufactured homes with earthquake bracing systems appeared to perform 

no better than those lacking these systems. The performance objectives of 

these earthquake bracing systems should be studied to improve performance. 

Approximately 50 wineries were exposed to significant seismic ground 

shaking in the South Napa earthquake. Direct loss of wine and damage to the 

production equipment varied by location, but was relatively low for the Napa 

Valley as a whole. The timing of the earthquake relative to the grape harvest 

contributed to the low losses. Much of the wine loss that did occur was 

attributed to collapse of wine barrel stacks. Given the hazard posed by 

collapsing barrel stacks, criteria for unanchored barrel storage should be 

established. The exposure of the public and winery guests to the wine barrel 

stacks should also be strictly limited. 

FEMA P-1024 13: Summary and Conclusions 13-2 
Nonstructural components and systems in most buildings surveyed were 

damaged to some extent, in some cases resulting in loss of building use for 

an extended period. Of concern was serious damage to exterior curtain walls 

in modern structures, an indication that building code requirements for 

accommodation of story drift are not being effectively applied. Pressurized 

piping system failures, especially fire sprinkler systems, caused significant 

water damage even though the actual number of piping failures was 

relatively small. 

The process of evaluating and posting buildings went smoothly following the 

earthquake. There were some significant variations in evaluation and 

placarding procedures among the different jurisdictions, especially with 

regard to the meaning of the RESTRICTED USE placard. The definitions 

provided to the public by jurisdictions should be consistent with the intent of 

the procedures set forth in ATC-20-1, Field Manual: Postearthquake Safety 

Evaluation of Buildings, (ATC, 2005). Use of the ATC-20-1 evaluation 

forms and procedures as written is strongly recommended. 

Once damaged buildings were identified, local officials took steps to protect 

the public from potential falling hazards posed by these buildings, balancing 

the need to protect the public from falling hazards while minimizing the 

impact of the earthquake on undamaged homes and businesses. Additional 

research is recommended to establish the effectiveness of various forms of 

scaffolding and barricading against different falling hazards, and provide 

guidance for engineers who design barriers to protect against damage posed 

by falling masonry. 

Every significant earthquake provides opportunities to assess the 

performance of buildings, reevaluate the effectiveness of earthquake risk 

mitigation efforts, and review the effectiveness of post-disaster response 

procedures. The 2014 South Napa earthquake demonstrated the vulnerability 

of URM buildings to damage in moderate ground shaking. It also 

highlighted that even in areas of high seismic risk where there is elevated 

awareness of that risk in the design and construction communities, moderate 

earthquakes cause costly and disruptive damage. The losses in modern 

structures were largely due to avoidable nonstructural damage. Attention to 

detailing for story drifts, installation of piping systems to avoid impact with 

other components, and contingency plans to allow for timely shut-down of 

damaged piping systems would have mitigated much of the observed 

damage, and none of these actions would have materially added to the cost of 

construction. Continued efforts are needed to inform and educate building 

owners and the design and construction communities on cost-effective ways 

to reduce earthquake damage and improve the resiliency of our communities. 

FEMA P-1024 13: Summary and Conclusions 13-3 

	 

	 

Appendix A 

Survey Forms and Instructions 

This appendix presents the forms used in the 1,000 foot survey around 

Station N016. The forms are based on the survey forms presented in 

ATC-38 report, Database on the Performance of Structures near StrongMotion Recordings: 1994 Northridge, California, Earthquake, (ATC, 2000). 

Based on the feedback received from initial investigations on the field, the 

ATC-38 forms were modified to account for new knowledge and specific 

issues related to this event. In addition, some portions of the instructions 

were clarified to improve the consistency of the data collected. 

A.1 Modifications to Survey Form and Instructions 

A General Damage Classification for nonstructural components was added 

on the page 1 of the form. In addition, two new levels were introduced to the 

General Damage Classifications (to apply to both structural and nonstructural 

components): 

	 An intermediate General Damage Classification was added between the 

“insignificant” and “moderate” levels. This new damage classification, 

“minor,” represents a state where structural or nonstructural damage have 

occurred but can be repaired relatively easily, without significant 

disruption to the occupants. Examples include repairs to equipment 

anchorage and supports, repair of minor cracking in concrete or masonry, 

or replacement of loosened anchors. It also includes damage to URM 

parapets, where the work does not require removal and reconstruction, 

and restrictions on occupants are limited to restricted access in the 

immediate vicinity of the work. 

	 A “collapse” classification was added to describe partial or complete loss 

of gravity support. 

Table A-1 provides the revised General Damage Classifications. 

A new level, “0,” was added to ATC-13 Damage State definitions for 

conditions where the percent damage to the structure or nonstructural 

components cannot be determined. Table A-2 provides the ATC-13 Damage 

State definitions used by the investigator teams on the field. 

FEMA P-1024 A: Survey Forms and Instructions A-1 
	 

Table A-1 General Damage Classifications 

Code Description 

(N) None No damage is visible, either structural or nonstructural. 

(I) Insignificant Damage requires no more than cosmetic repair. No structural 

repairs are necessary. For nonstructural elements this would 

include spackling partition cracks, picking up spilled contents, 

putting back fallen ceiling tiles, and repositioning equipment 

and furnishings. 

(m) Minor Minor repairable structural or nonstructural damage has 

occurred. Repairs can be made without significant disruption 

to occupants. This damage state includes cracked or dislodged 

masonry requiring repair. 

(M) Moderate Repairable structural damage has occurred. The existing 

elements can be repaired in place, without substantial 

demolition or replacement or elements. For nonstructural 

elements this would include minor replacement of damaged 

partitions, ceilings, contents, or equipment. 

(H) Heavy Damage is so extensive that repair of elements is either not 

feasible or requires major demolition or replacement. 

Includes URM buildings that require partial or complete 

reconstruction of damaged masonry walls. For nonstructural 

elements this would include major or complete replacement 

of damaged partitions, ceilings, contents, or equipment. 

(C) Collapse Partial or complete loss of gravity support with collapse. 

Table A-2 ATC-13 Damage State Definitions 

Damage State Percent Damage (damaged value/replacement value) 

0 Unknown Unknown 

1 None 0% 

2 Slight 0% - 1% 

3 Light 1% - 10% 

4 Moderate 10% - 30% 

5 Heavy 30% - 60% 

6 Major 60% - 100% 

7 Destroyed 100% 

Additional modifications included the following: 

	 Checkboxes were added for identifying the building as a candidate for 

further study of FEMA methodologies FEMA P-58, Seismic 

performance Assessment of Buildings, (FEMA, 2012b), FEMA E-74, 

Reducing the Risks of Nonstructural Earthquake Damage, (FEMA, 

2012a), and FEMA P-154, Rapid Visual Screening of Buildings for 

Potential Seismic Hazards: A Handbook, (FEMA, 2015), or as a 

A-2 A: Survey Forms and Instructions FEMA P-1024 
	 

	 

	 

	 

	 

	 

retrofitted unreinforced masonry building at the top of page 1 of the 

form. 

	 Irregularities were described in terms consistent with FEMA P-154 on 

page 2 of the form. 

	 Opportunities for sketching building plans and elevations were expanded 

on page 2 of the form. 

	 Parapets and major appendages were added to the scope of nonstructural 

systems and components examined on page 2 of the form. 

The six-page form and the instructions are provided in Figures A-1 and A-2, 

respectively. 

FEMA P-1024 A: Survey Forms and Instructions A-3 
 

This Page Intentionally Left Blank 
Figure A-1 Postearthquake Building Performance Assessment Form (page 1 of 6). 

FEMA P-1024 A: Survey Forms and Instructions A-5 
Figure A-1 Postearthquake Building Performance Assessment Form (page 2 of 6). 

A-6 A: Survey Forms and Instructions FEMA P-1024 
Figure A-1 Postearthquake Building Performance Assessment Form (page 3 of 6). 

FEMA P-1024 A: Survey Forms and Instructions A-7 
Figure A-1 Postearthquake Building Performance Assessment Form (page 4 of 6). 

A-8 A: Survey Forms and Instructions FEMA P-1024 
Figure A-1 Postearthquake Building Performance Assessment Form (page 5 of 6). 

FEMA P-1024 A: Survey Forms and Instructions A-9 
Figure A-1 Postearthquake Building Performance Assessment Form (page 6 of 6). 

A-10 A: Survey Forms and Instructions FEMA P-1024 
Figure A-2 Surveyor instructions (page 1 of 4). 

FEMA P-1024 A: Survey Forms and Instructions A-11 
Figure A-2 Surveyor instructions (page 2 of 4). 

A-12 A: Survey Forms and Instructions FEMA P-1024 
Figure A-2 Surveyor instructions (page 3 of 4). 

FEMA P-1024 A: Survey Forms and Instructions A-13 
Figure A-2 Surveyor instructions (page 4 of 4). 

A-14 A: Survey Forms and Instructions FEMA P-1024 
Appendix B 

Recovery Advisories 

This appendix presents two recovery advisories being prepared by the 

Applied Technology Council for the Federal Emergency Management 

Agency in response to the 2014 South Napa earthquake. 

B.1 Earthquake Strengthening of Cripple Walls in WoodFrame Dwellings 

South Napa Earthquake Recovery Advisory FEMA DR-4193-RA2, 

Earthquake Strengthening of Cripple Walls in Wood-Frame Dwellings, was 

under development by the Applied Technology Council at the time this 

report was being finalized, thus a brief summary is provided here. The 

document will be available on the FEMA website (http://www.fema.gov 

/earthquake-publications) when completed. 

B.1.1	 Purpose and Background 

The South Napa earthquake and past earthquakes have damaged many 

cripple walls in residential structures, causing significant repair costs to the 

homeowners. The repair cost for failed cripple walls is significantly higher 

than the cost of strengthening cripple walls before an earthquake. 

Several existing documents provide prescriptive approaches to the 

strengthening of cripple walls up to four feet tall: 

	 Chapter A3 of the International Existing Building Code (ICC, 2012b) 

provides provisions and details for engineers. 

	 Standard Plan A: Residential Seismic Strengthening Plan (developed in 

2008, available at http://seaonc.org/free-publications, last accessed 

March 12, 2015) provides a prescriptive seismic strengthening plan for 

cripple wall bracing and foundation sill plate anchorage of light woodframed residential structures. 

	 Seismic Retrofit for Residential Wood Frame Cripple Walls and Sill 

Plate Anchorage (developed by Simson Strong-Tie in 2012, available at 

http://www.strongtie.com/literature/f-plans.html, last accessed March 12, 

2015) is based on the 2012 International Existing Building Code and 

calls out the specific retrofit solutions for reinforcing a home’s cripple 

wall and foundation connection. 

FEMA P-1024	 B: Recovery Advisories B-1 
 

 Standard Earthquake Home Retrofit Plan Set (prepared by the City of 

Seattle under Project Impact in 2012, available at http://www.seattle.gov 

/dpd/static/get_file/Earthquake%20Home%20Retrofit%20Planset_DPD 

D017407_LatestReleased.pdf, last accessed March 12, 2015) provides 

plan details and reference sheets. 

Where a dwelling meets the limitations set for applicability and where 

approved by the local building official, a homeowner or contractor may use 

one of the prescriptive plan sets to strengthen cripple walls up to four feet tall 

without a detailed design by an engineer. 

B.1.2 Scope of Document 

This Recovery Advisory currently under development briefly describes the 

issues involved in the retrofit of cripple walls in wood residential structures 

and will include a prescriptive plan set for the earthquake strengthening of 

cripple walls and the anchorage of sill plates in one- or two-story tall, one- or 

two-family residential structures with cripple walls up to seven feet in height. 

The plan set is generally consistent with the seismic strengthening provisions 

of the 2012 International Existing Building Code and the 2013 California 

Existing Building Code (California Building Standards Commission, 2013b). 

The design in the plan set is based on the following assumed seismic design 

parameters: SDS equal to 1.56g and SD1 equal to 0.97 g; Seismic Design 

Category D; Site Class D; Seismic Importance Factor, I, equal to 1.0; 

Response Modification Factor, R, equal to 6.5; and Design Base Shear, V, 

equal to 0.13W, where W is the seismic weight of the structure (using 

allowable stress design). The value of the Design Base Shear will include a 

0.75 reduction factor commonly applied in design for existing structures, as 

specified in Section A301.3 of the 2012 International Existing Building 

Code. Given this design basis, the plan set is expected to be applicable in 

many areas of high seismicity in the United States, not just in the vicinity of 

Napa, California. 

The plan set includes the following sheets: Technical notes; construction data 

and earthquake strengthening schedule; layout plan; and details of sill plate 

to concrete foundation connections, floor framing to sill plate connections, 

cripple wall to floor framing connections, tie-down installation, plywood 

braced-panel installation, foundation replacement, and panel notching and 

top-plate splices. The plan set will also provide example foundation plans 

with example strengthening of cripple walls. 

B-2 B: Recovery Advisories FEMA P-1024 
	 

B.2 Repair of Earthquake-Damaged Masonry Fireplace 

Chimneys 

South Napa Earthquake Recovery Advisory FEMA DR-4193-RA1, Repair of 

Earthquake-Damaged Masonry Fireplace Chimneys, recommends best 

practices for reconstruction of earthquake-damaged masonry chimneys in 

one- and two-family dwellings to minimize risk of damage in a future 

earthquake. The information provided is advisory and building permits are 

required when conducting the work described. 

FEMA DR-4193-RA1 is provided in its entirety in the following 11 pages. 

FEMA P-1024	 B: Recovery Advisories B-3 
This Page Intentionally Left Blank 
     

                   

                 

             

               

                     

             

             

               

           

        

             

           

                 

               

           

             

                                 

                         

                       

           

   

             

             

                 

             

                   

                   

                   

           

       

                   

                       

                   

               

                

               

       

          

         

     

 

 

 

	 

	 

	 

	 

	 

 

	 

 

 

 

	 

	 

	 

	 

	 

 

	 

Repair of Earthquake-Damaged 

Masonry Fireplace 

Chimneys 

SOUTH NAPA EARTHQUAKE RECOVERY ADVISORY FEMA DR-4193-RA1 

Purpose and Intended Audience

The August 24, 2014 South Napa Earthquake has again served

as a reminder that masonry chimneys in wood‐frame dwellings

are extremely vulnerable to earthquake shaking. FEMA

assessment teams observed over 100 brick masonry chimneys

damaged in the South Napa Earthquake (Figures 1 and 2). Older,

unreinforced masonry chimneys with degraded mortar are

most vulnerable, but even masonry chimneys constructed

according to modern standards are susceptible to significant

damage. Collapses of previously damaged and reconstructed

chimneys were also observed.

This Recovery Advisory recommends best practices for

reconstruction of earthquake‐damaged masonry chimneys in

one‐ and two‐family dwellings to minimize risk of damage in

future earthquakes. Owners of dwellings that might have a

historic designation, and owners of multi‐family dwellings,

should consult with the building department regarding

applicable requirements.

Information in this advisory is intended to be used by homeowners to compare and contrast options for

reconstruction, and by contractors to understand details and applicable building code requirements associated

with implementation of these options. Note that building permits are always required when

performing the work described in this advisory.

Key Issues:

1.	 Damaged chimneys reconstructed to match pre‐earthquake conditions

will remain vulnerable to damage in future earthquakes.

2.	 Repair of older, unreinforced masonry chimneys to meet modern

seismic performance standards is generally considered to be

infeasible, and such chimneys may remain vulnerable to collapse in

future earthquakes.

3.	 Best practices for reducing future potential for damage involve partial

or complete removal of the masonry and reconstruction with metal

flues or fireplace inserts and light‐frame construction.

This Recovery Advisory Addresses:

	 Capping of the chimney at the roof level (Alternative A)

	 Reconstruction of the chimney from the top of the firebox up, either

maintaining the use of the existing masonry fireplace (Alternative B),

or installing a fireplace insert (Alternative C), or

	 Full reconstruction of the firebox and chimney (Alternative D).

Figure 1: Chimney damaged in the South Napa

Earthquake. Photo Credit: Exponent.

Figure 2: Chimney damaged in the

South Napa Earthquake. Photo Credit:

Janiele Maffei, CEA

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Best Practices for Minimizing Future Risk
 

Good – Capping of Chimney at Roof Level (Alternative A)
 

For a single story dwelling, if all damage occurred at or above the roof level, the chimney

can be permanently removed down to the roof level. This is only possible when use of

the fireplace will be discontinued. This is the least costly of the alternatives, but also

provides a lesser level of hazard mitigation.

Exterior appearance: The firebox and chimney will remain unchanged up to the roof

level. The upper portion of the chimney will be removed.

Interior appearance: Fireplace and mantel will remain, but the fireplace can no longer be

used and will need to be closed off.

Environmental: Fireplace will no longer burn combustible materials.

Better – Reconstruction from Top of Firebox, Maintaining Existing Fireplace (Alternative B)

Allows continued use of an undamaged masonry firebox in combination with a new

metal flue and light‐weight chimney enclosure.

Exterior appearance: The firebox at the bottom of the chimney will remain exposed

brick. The reconstructed portion of the chimney is often finished with siding or stucco,

but can also be finished with adhered brick veneer to preserve the original appearance.

Interior appearance: Remains unchanged.

Environmental: Fireplace can remain fuel‐burning (note that the owner could also

choose to convert to a more environmentally friendly gas‐burning fireplace).

Better – Reconstruction from Top of Firebox, Using Fireplace Insert (Alternative C)

Allows continued use of an undamaged masonry firebox in combination with a new

chimney. In addition, a factory‐built fireplace insert is installed inside of the fireplace.

Exterior appearance: The firebox at the bottom of the chimney will remain exposed

brick. The reconstructed portion of the chimney is often finished with siding or stucco,

but can also be finished with adhered brick veneer to preserve the original appearance.

Interior appearance: Fireplace and mantel will remain, but a fireplace insert will be

visible inside of the original masonry fireplace.

Environmental: Fireplace can remain fuel‐burning. Fireplace inserts can be more energy efficient at producing

heat in the home, can reduce emissions through more complete combustion of solid fuels, or can be converted

to more environmentally friendly gas‐burning.

Best – Full Reconstruction of Firebox and Chimney (Alternative D)

Involves replacement of the entire firebox and chimney with light‐frame construction

above the top of the foundation. This is necessary if earthquake damage extends below

the shoulder of the firebox. It is also appropriate where complete removal of fireplace

masonry is preferred.

Exterior appearance: The entire height of the firebox and chimney is reconstructed and

is often finished with siding or stucco, but can also be finished with adhered brick veneer

to preserve the original appearance. None of the original brick masonry construction

remains.

Interior appearance: Fireplace and mantel will be removed and replaced with factory‐built fireplace unit. This

can provide an opportunity to change or modernize the interior appearance or enhance the use of the fireplace.

Environmental: Fireplace can remain fuel‐burning. Factory‐built fireplace units can be more energy efficient at

producing heat in the home, can reduce emissions through more complete combustion of solid fuels, or can be

more environmentally friendly gas‐burning.

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Other Methods of Repair or Reconstruction

While the solutions detailed in this advisory are recommended as best practices, other code‐conforming

approaches for repair or reconstruction are possible:

	 Installation of concrete inside the flue. In cases where the fireplace will not be used in the future, lightly

damaged chimneys can sometimes be repaired and strengthened through the installation of rebar into the

flue (over the full height) and by filling the flue with concrete. This approach reduces the potential for some

types of damage, but the increased weight and difficulty in adequately anchoring the heavy chimney to the

dwelling raises questions about the validity of this approach and the overall benefit for reducing future risk.

	 Engineered solutions. Engineered solutions for reconstruction of damaged chimneys are possible. An

engineered approach has the advantage that the solution can be customized for the specific situation, and

can include a number of wide‐ranging options for reinforcing or reconstructing the chimney and firebox. An

engineered approach may be appropriate or necessary in some dwellings.

	 Reconstruction in‐kind. Although reconstruction of chimneys to their pre‐earthquake configuration may be

permitted by building codes in some jurisdictions, this approach does little to reduce the potential for

future damage or risk to life‐safety, and is not recommended.

Recommended Methods of Hazard Mitigation

Whether or not your chimney has been damaged, now is a good time to be thinking about mitigating the hazard

associated with masonry chimneys before the next earthquake. Although they are presented as alternatives for

repair and reconstruction after damage in an earthquake, the solutions detailed in this advisory are also

recommended as best practices for pre‐earthquake hazard mitigation (retrofit) of chimneys. As such they can be

applied equally to undamaged chimneys.

Where it is not possible to implement these best practices outlined in this advisory, other steps can be taken

before the next earthquake to partially reduce the risk posed by masonry chimneys, such as:

	 Minimizing time spent next to the chimney, both inside and outside the dwelling. This will minimize the risk

of serious injury should the chimney collapse. In particular, sleeping adjacent to a masonry chimney should

be avoided.

	 Installing plywood in the attic space, either attached to the underside of the roof rafters or the top of the

ceiling joists. Plywood in the attic space is intended to slow or even prevent brick debris from coming

through the ceiling into the living space in the event of chimney failure. This approach is easy and relatively

inexpensive; however, the effectiveness is likely to vary widely from residence to residence. It is important

that plywood installed for this purpose does not become used as an attic storage area, as this can overload

the ceiling and roof systems and result in failure.

Several methods are NOT recommended for pre‐earthquake mitigation. These include the following:

	 Masonry chimneys should not be retrofitted using steel braces that extend down to the roof surface. Such

bracing is thought to have promoted chimney failure in past earthquakes, and must be carefully engineered.

	 Simply restoring the outside surface of deteriorated mortar joints (repointing) or patching of isolated

masonry cracks is not sufficient. While such actions are encouraged as part of regular chimney maintenance,

they will do little to reduce the potential for damage in future earthquakes.

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General Information for Construction

Building Codes

Reconstruction of damaged chimneys must be in conformance with adopted building code provisions and local

ordinances. Reconstruction must use manufactured parts (metal flues, anchor plates, flue caps, fireplace inserts,

and factory‐built fireplaces) meeting applicable Underwriters Laboratory (UL) Standards (commonly referred to

as UL listed). For manufactured parts, installation in accordance with the manufacturer’s installation instructions

is mandatory. In addition, installation instructions impose some requirements on the surrounding construction,

such as required dimensions and clearances.

Other parts of the reconstruction are required to be in accordance with applicable provisions of the adopted

building or residential code. Most states and local jurisdictions base their residential code on a recent edition of

the International Residential Code (IRC) (ICC, 2015). In California, this results in the California Residential Code

(CRC) (CBSC, 2013), which can be further amended by the local building official.

This recovery advisory does not attempt to provide an exhaustive list of applicable building codes. Some limited

sections of interest are summarized below. Persons designing or performing repair work are advised to become

familiar with applicable requirements.

Scope of Work

For dwellings in California, repair of damage does not trigger requirements for seismic strengthening beyond the

scope of repair (California Building Code Section 3405.1.2 (HCD 1)) (CBSC, 2013). The only exception is where

conditions exist that are judged by the building official to result in substandard building conditions, in which case

additional work to correct the substandard conditions would be required.

Building Permit

A building permit is required for work described in this advisory and must be obtained prior to the start of

construction work.

California Residential Code Sections of Interest

For foundation extension: Minimum concrete strength of 2500psi per Section R402.2

Minimum depth of foundation, 12 inches below grade Section

R403.1.4

For bolting to concrete beam: Sections R403.1.6 and R603.3.1

For cold‐formed steel stud walls: Section R603

For fireplace and chimney construction: Chapter 10

For roof flashing and crickets: Section R905

For chimney enclosure wall covering: Chapter 7

Dwellings with a Historic Designation

Older dwellings may have a historic designation, indicating that they are deemed to be historically significant.

This designation can be given at the Federal (National Register of Historic Places), State (State Register of

Historic Places) or local level, and local building departments generally have a list of buildings with such

designation. For historic dwellings, further consideration of repair methods that preserve the existing historic

construction and appearance are appropriate. Historic designation may come with additional requirements

such as historic preservation guidelines, and review of planned repairs by the local planning department and

historic preservation board. Historic designation may also permit flexibility regarding reconstruction methods

and materials, including reconstruction of damaged masonry chimneys using matching masonry. Where such

reconstruction is used, an engineered solution is recommended and a structural engineer should develop the

best approach for mitigating future earthquake hazard. Owners of dwellings that may have a historic

designation should consult with the building department regarding applicable requirements.

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Alternative A: Capping of Chimney at Roof Level

Overview

For single story dwellings, where the chimney is damaged at or

above the roof level and it is not intended that the fireplace be

used in the future, it is possible to remove the chimney down to

the roof line and install a sheet metal cap over the chimney for

weather protection.

This alternative provides the greatest hazard reduction for

chimneys that extend a considerable distance above the roof

line, and less benefit for short chimneys.

It is recommended that the chimney be removed to a distance of

three to six inches above the adjacent roof. This will permit a

sheet metal cap that extends several inches down each side of

the chimney to be installed, providing a flashing. The cap should

be secured to the masonry.

The interior of the firebox will need to be closed off to prevent

any possible use of the fireplace. For least impact on interior

appearance, plywood can be installed across the fireplace

opening, set back into the fireplace, and painted to match interior finishes.

Although capping eliminates the hazard associated with the most vulnerable portion of the chimney (above the

roof), there is still risk of damage or collapse of the remaining masonry in future earthquakes.

Alternative B: Reconstruction from Top of Firebox Up, Maintaining Existing

Fireplace

Overview

Alternative B permits continued use of an undamaged firebox in

combination with a new chimney. Instead of using a

conventional masonry chimney with a clay flue liner, the new

chimney is constructed using a lightweight metal flue contained

in a cold‐formed steel stud chimney enclosure, as shown in

Figure 4. This lightweight, flexible construction is much more

resistant to damage in future earthquakes. Although the

remaining masonry firebox could be damaged in a future

earthquake, the firebox is much less vulnerable to damage than

the original masonry chimney. As a result, the risk of collapse

and the associated risk to life safety are greatly reduced when

this reconstruction alternative is implemented.

Primary Components

The primary components of Alternative B construction are listed

below, illustrated in Figure 5. Additional details of construction

are provided in Figures 6 and 7.

1.	 Masonry firebox. Inspect the firebox to verify that it is in good condition prior to start of repair work.

2.	 Existing framing. To remain as is except for roof blocking as detailed in Figure 7 and Item 7 below.

3.	 Masonry veneer. Verify support and anchorage of existing veneer where it occurs above and surrounding

the fireplace.

Figure 3: Dwelling with a chimney capped at the

roof line.

Figure 4: Dwelling with chimney reconstructed

from the firebox up.

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4.	 Firebox to flue transition. The transition from

the masonry firebox to the metal flue includes:

anchorage to masonry, concrete bond beam,

steel adapter cone, and anchor plate. This detail

is critical to the safe performance of this

reconstruction alternative. See Figure 6 for more

information.

5.	 Cold‐formed steel track. Anchor track to

concrete beam per Figure 6.

6.	 Cold‐formed steel stud wall. Provide full height

studs.

7.	 Chimney connection to dwelling. Provide stud

blocking and steel strap connection to existing

dwelling framing at upper floor, ceiling, and roof

framing.

8.	 Insulation. Provide insulation between studs at

exterior walls of the chase, allowing for the

proper clearances in accordance with the

manufacturer’s installation instructions.

9.	 Metal flue. Provide UL Standard 103 listed metal

flue, installed in accordance with manufacturer’s

instructions. Provide as large a flue as can be

installed in available space while still meeting

minimum clear distances.

10. Flue cap. Install flue cap supplied by flue

manufacturer as part of the flue assembly.

11. Fire blocking. Provide fire blocking between chimney chase and attic as required by the building code.

Figure 5: Components of a masonry firebox in combination with

lightweight metal flue and chimney (Alternative B).

Figure 6: Example of detail at masonry firebox transition to metal flue and light‐frame chimney (Alternative B, similar

detail for Alternative C).

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Requirements for Flue Transitions and Components

Figure 6 provides details for the transition from the masonry firebox to the metal flue and stud wall chimney

chase. The components of this transition include the following:

	 Fabricate a 12 gage (97 mil) minimum sheet steel adaptor cone as shown in Figure 6. The adaptor cone is to

have minimum 12 gage (97 mil) sheet steel top and bottom plates as shown. This will likely need to be

custom fabricated by a sheet metal shop for each chimney. All seams are to be fully welded. The adaptor

cone is intended to provide a smooth‐surfaced transition between the flue opening at the top of the firebox

and the anchor plate and metal flue. The base plate geometry is to match the opening geometry at the top of

the firebox, and the top plate geometry is to be coordinated with the anchor plate. The adaptor cone will also

serve to minimize movement of heated gas through cracks that might form in the surrounding concrete

beam. The adaptor cone is to be set in cementitious grout.

	 Provide not less than four 1/2‐inch diameter threaded rod anchors anchoring the adaptor cone base plate to

the firebox masonry, as shown in Figure 6. Extend the threaded rods to one inch below the top of the

concrete beam. Where the existing masonry is fully grouted at anchor locations, drill one‐inch diameter holes

six inches deep and set in high‐strength grout. Where the existing masonry is not fully grouted, place

threaded rods in cavity and grout the entire cavity.

	 Place reinforcing steel (rebar) and construct a concrete beam around the adaptor cone, using the cone as the

inside form. Maintain a minimum 1‐1/2 inch clear distance between rebar and outside face of concrete.

	 When required by anchor plate manufacturer, install stone wool (basalt) insulation board on top of the

transition cone top plate as shown in Figure 6.

	 Install fireplace anchor plate in accordance with the manufacturer’s installation instructions. UL Standard

103a provides information on anchor plates; however, UL does not currently certify (list) these anchor plates.

The provider of the metal chimney should provide an anchor plate that is intended for use with the chimney,

and should verify that it has been tested per UL103a.

	 Enclose the new flue in a light‐frame chimney enclosure constructed of not less than 18 gage (43 mil) by 3‐1/2

inch deep galvanized steel studs at not more than 12 inches on center. Install fire stops per code

requirements. Fasten the steel studs to the existing residence exterior wall and tie the chimney framing into

the existing roof framing with not less than 18 gage by 1‐1/4 inch wide steel straps with not less than four #8

screws to the steel construction and four 8d common nails to existing wood construction.

Light‐Frame Chimney Bracing to Roof

IRC and CRC requirements for the

height of the chimney require that

the top of the chimney extend

three feet above the roof and not

less than two feet above the

elevation of the roof or other

construction within a ten foot

radius, as illustrated in Figure 7.

This often requires that the

chimney extend a significant

distance above the roof line. Where

this occurs, it is necessary to

provide bracing of the chimney

down to the roof. Such bracing

should be provided in the upper

third of the chimney clear height

above the roof (H), as shown in

Figure 7. Chimney bracing may also

be required in Alternative C. Figure 7: Bracing of light‐frame chimney chase to roof (Alternatives B and C).

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Alternative C: Reconstruction from the Top of Firebox, Using Fireplace Insert

Overview

Alternative C permits continued use of an undamaged masonry

firebox in combination with a new chimney and fireplace insert.

For decades wood‐frame dwellings included a conventional

masonry chimney and fireplace. However, many homes are now

constructed with prefabricated fireplaces, or have had factory

units inserted into the original masonry firebox (Figure 8). While

a factory insert will not make a fireplace more earthquake‐

resistant, it can be more energy efficient and more ecologically

friendly. Thus a factory‐built fireplace insert may be a viable

option at the time of the repair.

A factory‐built fireplace insert provides a firebox within a steel

or cast iron shell. The insert occupies the space of the original

masonry firebox and utilizes the existing chimney chase. Building

codes require that these systems be UL listed, and fireplace

inserts often come packaged with a metal chimney as a certified

system. (Homeowners are cautioned against using a chimney or

connections not approved by the fireplace manufacturer. If your

home already has a fireplace insert that utilizes the original masonry

chimney liner, you will need to find a metal flue that is UL listed for

use with your fireplace insert.)

Primary Components

The primary components of the installation of a fireplace insert into

an existing masonry fireplace are listed below and illustrated in Figure

9. Items not noted are similar to information shown in Figure 5.

1.	 Bottom connection. Secure bottom of fireplace insert.

2.	 Fireplace insert. Provide UL Standard 127 listed fireplace insert.

3.	 Damper and draft stop. Remove as required to install flue.

4.	 Flexible flue transition from insert to chimney. Install transition

supplied as part of UL listed flue.

5.	 Metal flue connections. Install flue connections supplied as part of

UL listed assembly.

6.	 Firebox to flue transition. Provide transition similar to that shown

in Figure 6.

7.	 Metal chimney. Provide UL listed metal chimney.

8.	 Cold‐formed steel stud wall. Provide chimney enclosure as

described for Alternative B.

Requirements for Fireplace Inserts

Installation of factory inserts must be done per the manufacturer’s instructions and all applicable code

requirements (consult your local building department). At a minimum, the following should be considered:

	 Some homes have prefabricated chimneys that should not be equipped with an insert, or that greatly limit

the inserts certified for such use. (It can be difficult to tell the difference between prefabricated and

conventional masonry fireplaces without inspecting the inside of the firebox and flue connection.)

Figure 8: Fireplace insert

Figure 9: Components of a Factory‐built

Fireplace Insert (Alternative C).

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	 Carefully check the dimensions to ensure the selected insert will fit properly. The size and location of the

damper opening is particularly important. (If you are uncomfortable with this determination, enlist the help

of a professional contractor.)

	 The insert, chimney, and accessories must be certified per UL Standard 127 (listed and labeled as such). Your

building official and contractor can assist with other local building code requirements.

	 A hearth extension (UL 1618 listed) may be needed, particularly if the insert does not fit entirely within the

firebox.

	 The insert should be anchored to prevent shifting.

	 Flue joints and connection to the fireplace must be per the manufacturer’s instructions and UL standards.

Masonry Firebox Transition to Light‐Frame Chimney

This method of reconstruction requires a transition from the firebox to the metal flue and stud wall chimney

chase, similar to that shown in Figure 6 for Alternative B. Alternative C is different in that the metal flue runs

continuous past the concrete bond beam. See installation instructions for required clear distance between bond

beam and flue.

Light‐Frame Chimney Bracing to Roof

This method of reconstruction is also subject to IRC and CRC chimney height requirements and chimney bracing

may be required. See light‐frame chimney bracing requirement in Figure 7 under Alternative B for more details.

Alternative D: Full Reconstruction of Firebox and Chimney

Overview

If earthquake damage extends below the shoulder of the firebox

or if complete removal of all masonry is preferred, the entire

firebox and chimney can be replaced from the top of foundation

up. This involves installing a factory‐built fireplace and metal flue

inside a cold‐formed steel stud chimney chase, as seen in Figure

10. This type of lighter and more flexible construction avoids

many of the issues that have made masonry fireplaces and

chimneys vulnerable to damage in past earthquakes. If preserving

the architectural aesthetic of masonry is important, adhered

masonry veneer can be used.

Primary Components

The primary components of Alternative D construction are listed

below and illustrated in Figure 11.

1.	 Existing foundation. To remain.

2.	 Extension of existing foundation. Provide where required to

meet dimensional requirements specified by the fireplace manufacturer. Where foundation extension is

required, match the depth of the existing foundation, but not less than 12 inches below grade. Provide No. 4

rebar top and bottom of new concrete. Epoxy dowel to the existing footing at not more than 12 inches on

center. See the applicable building code for additional requirements.

3.	 Non‐combustible hearth extension. Provide hearth extension not less than 20 inches in depth.

4.	 Factory‐built fireplace. Provide UL Standard 127 listed fireplace.

5.	 Cold‐formed steel track. Anchor track to concrete foundation.

6.	 Cold‐formed steel stud wall. Provide full height studs.

Figure 10: Replacement of entire firebox and

chimney with light‐frame construction.

Repair of Earthquake-Damaged Masonry Fireplace Chimneys 	 	 HSFE60-12-D-0242 / January 2015 Page 9 of 11 
         

           

     

                 

           

       

         

   

         

                 

         

   

           

             

                

   

           

  

           

         

   

             

              

                                     

                                     

                        

                                     

                                 

                                   

                                   

                               

                           

                       

                                     

                             

                           

         

                                 

           

         

                   

              

         

	 

	 

	 

 

	 

	 

 

	 

	 

	 

	 

 

	 

	 

	 

	 

 

	 

	 

 

	 

	 

	 

	 

 

	 

7.	 Existing framing. Framing may require modification to

accommodate new fireplace opening. Use applicable

building code provisions.

8.	 Metal flue. Provide UL listed metal flue supplied by

fireplace manufacturer and to be installed in

accordance with their installation instructions.

9.	 Stud blocking. Provide continuous blocking at 4’‐0”

maximum vertical spacing.

10. Insulation. Provide insulation between studs at

exterior walls of the chase, allowing for the proper

clearances in accordance with the manufacturer’s

installation instructions.

11. Chimney connection to dwelling. Provide stud

blocking and steel strap connection to existing

dwelling framing at upper floor, ceiling, and roof.

12. Existing framing. To remain.

13. Light‐frame wall. From roof up.

14. Chimney cap. Provide framed chimney cap on chimney

chase.

15. Flue cap. Install flue cap supplied by flue

manufacturer.

16. Fire blocking. Provide fire blocking between chimney

chase and attic.

Requirements for Removal and Replacement of the

Firebox

	 Remove all existing masonry above the foundation.

	 Fireboxes often extend a foot or more into the dwelling living space. Removal will need to include the interior

portions of the masonry firebox. Mantels and shelves that are supported off of the firebox will likely need to

be removed, but might be later reinstalled, supported off the dwelling wall.

	 Masonry veneer is sometimes used as the interior finish for the wall around the fireplace. Where this is the

case, this veneer will likely need to be removed to allow framing modifications and fireplace installation. If

the veneer is to be reinstalled, details should conform to applicable provisions of IRC or CRC Chapter 7.

	 Portions of the exterior wall, floor, ceiling, or roof of the dwelling could potentially be supported on the

masonry firebox. Where this is the case, these elements of the dwelling will need to be re‐supported.

Modifications to dwelling framing should conform to applicable provisions of the IRC or CRC.

	 Minimum dimensional requirements are provided in the manufacturer’s installation instructions. These will

determine the required depth and width of the chimney chase, as well as the size of the interior fireplace

opening. It is possible that these dimensions will exceed current dimensions, requiring extension of the

foundation and enlargement the framed wall opening. These modifications should be made in accordance

with the IRC or CRC.

	 Factory‐built fireplace, flue and chimney cap should conform to UL Standard 127 and should be installed in

accordance with the manufacturer’s installation instructions.

Resources and other Useful Links

	 Association of Bay Area Governments, Training Materials for Seismic Retrofit of Wood‐Frame Homes.

http://www.abag.ca.gov/bayarea/eqmaps/fixit/training.html

Figure 11: Components of a factory‐built fireplace in light‐

frame chimney chase (Alternative D).

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	 California Governor’s Office of Emergency Services and FEMA, Guidelines to Strengthen and Retrofit your Home

before the Next Earthquake, Revised October, 2000.

http://www.cupertino.org/Modules/ShowDocument.aspx?documentid=527

	 California Seismic Safety Commission, Homeowner’s Guide to Earthquake Safety, 2005.

http://www.seismic.ca.gov/pub/CSSC_2005‐01_HOG.pdf

	 CBSC, 2013 California Building Code, California Building Standards Commission, Sacramento, California.

http://www.ecodes.biz/ecodes_support/Free_Resources/2013California/13Building/13Building_main.html

	 CBSC, 2013 California Residential Code, California Building Standards Commission, Sacramento, California.

http://www.ecodes.biz/ecodes_support/Free_Resources/2013California/13Residential/13Residential_main.html

	 City of Los Angeles, Department of Building and Safety, P/BC 2008‐070: Reconstruction and Replacement of

Earthquake Damaged Masonry Chimneys, 2008. http://ladbs.org/LADBSWeb/LADBS_Forms/InformationBulletins/IB‐P

‐BC2008‐070EQDamagedChimney.pdf

	 City of Napa, Community Development Department, Retrofitting Masonry Fireplace with Factory Built Metal

Chimney. http://www.cityofnapa.org/images/CDD/buildingdivdocs/handoutsanddetails

/retro_fitting_masonry_fireplace_with_factory_built_metal_chimney.pdf

	 City of San Luis Obispo, Building & Safety Division, Reconstruction and Replacement of Earthquake Damaged Masonry

Chimneys, January 2004. http://www.slocity.org/communitydevelopment/build/infobull1.pdf

	 City of Seattle, Department of Planning and Development, Director’s Rule 5‐2004: Alteration and Repair of

Unreinforced Masonry Chimneys. http://www.seattle.gov/dpd/codes/dr/DR2004‐5.pdf

	 Consortium of Universities for Research in Earthquake Engineering, EDA‐02: General Guidelines for the Assessment

and Repair of Earthquake Damage in Residential Woodframe Buildings, February 2010.

http://www.curee.org/projects/EDA/docs/CUREE‐EDA02‐2‐public.pdf

	 Federal Emergency Management Agency, FEMA 232: Homebuilders’ Guide to Earthquake‐Resistant Design and

Construction, June 2006. https://www.fema.gov/media‐library/assets/documents/6015

	 Federal Emergency Management Agency, FEMA 547: Techniques for the Seismic Rehabilitation of Existing Buildings,

2006 Edition. http://www.fema.gov/media‐library‐data/20130726‐1554‐20490‐7382/fema547.pdf

	 Federal Emergency Management Agency, FEMA E‐74: Reducing the Risks of Nonstructural Earthquake Damage—A

Practical Guide, Fourth Edition, December 2012. https://www.fema.gov/earthquake‐publications/fema‐e‐74‐reducing

‐risks‐nonstructural‐earthquake‐damage

	 ICC, 2015 International Residential Code, International Code Council, Country Club Hills, Illinois.

For more information, see the FEMA Building Science Frequently 

Asked Questions web site at http://www.fema.gov/frequentlyasked-questions. 

If you have any additional questions on FEMA Building Science 

Publications, contact the helpline at FEMA-Buildingsciencehelp@ 

fema.dhs.gov or 1-866-927-2104. 

You may also sign up for a FEMA Building Science e-mail 

subscription, which is updated with publication releases and 

FEMA Building Science activities. Subscribe at 

https://public. govdelivery.com/accounts/USDHSFEMA/ 

subscriber/new?topic_ id=USDHSFEMA_193. 

Visit the Building Science Branch of the Risk Reduction 

Division at FEMA’s Federal Insurance and Mitigation 

Administration at http://www.fema.gov/building-science. 

To order publications, contact the 

FEMA Distribution Center: 

Call: 1-800-480-2520 

(Monday–Friday, 8 a.m.–5 p.m., 

EST) Fax: 240-699-0525 

E-mail: FEMA-PublicationsWarehouse@fema.dhs.gov 

Additional FEMA documents can be 

found electronically in the FEMA 

Library at http://www.fema.gov 

/library. 

Please scan this QR 

code to visit the FEMA 

Building Science Web 

page. 

Repair of Earthquake-Damaged Masonry Fireplace Chimneys 	 	 HSFE60-12-D-0242 / January 2015 Page 11 of 11 

References 

ASCE, 2010, Minimum Design Loads for Buildings and Other Structures, 

ASCE/SEI 7-10, American Society of Civil Engineers, Reston, Virginia. 

ASCE, 2014, South Napa M 6.0 Earthquake of August 24, 2014, TCLEE 

Preliminary Reconnaissance Report, John Eidinger editor, American 

Society of Civil Engineers, Reston, Virginia. Available at: 

http://cms.asce.org/uploadedFiles/Technical_Groups_and_Institutes/TCL 

EE/NAPA%202014%20ASCE%20Final.pdf , last accessed January 28, 

2015. 

ATC, 1985, Earthquake Damage Evaluation Data for California, ATC-13, 

prepared by the Applied Technology Council funded by the Federal 

Emergency Management Agency, Redwood City, California. 

ATC, 2000, Database on the Performance of Structures near Strong-Motion 

Recordings: 1994 Northridge, California, Earthquake, ATC-38, 

prepared by the Applied Technology Council for the U.S. Geological 

Survey, California Office of Emergency Services, and Institute for 

Business and Home Safety, Redwood City, California. 

ATC, 2005, Field Manual: Postearthquake Safety Evaluation of Buildings, 

ATC-20-1 Second Edition, Applied Technology Council, Redwood City, 

California. 

Barnes, Jim, 2014, personal communication with Bret Lizundia. Mr. Barnes 

coordinates the Safety Assessment Program for Cal OES. 

Cal OES, 2013, Safety Assessment Program Coordinator Student Manual, 

State of California Governor’s Office of Emergency Services, Version 6, 

Sacramento, California. 

CALBO, 2013, Interim Guidance for Barricading, Cordoning, Emergency 

Evaluation and Stabilization of Buildings with Substantial Damage in 

Disasters, California Building Officials, November. 

California Building Standards Commission, 1998, 2001, 2013a California 

Building Standards Code, Sacramento, California. 

FEMA P-1024 C: References C-1 
 

California Building Standards Commission, 2013b, California Existing 

Building Code, California Code of Regulations Title 24, Part 10, 

Sacramento, California. 

City of Napa, 2000, Retro Fitting Masonry Fireplace with Factory Built 

Metal Chimney, Community Development Department, Napa, California. 

Available at http://www.cityofnapa.org/images/CDD/buildingdivdocs 

/handoutsanddetails/retro_fitting_masonry_fireplace_with_factory_built_ 

metal_chimney.pdfhttp://www.cityofnapa.org/images/CDD/buildingdivd 

ocs/handoutsanddetails/retro_fitting_masonry_fireplace_with_factory_bu 

ilt_metal_chimney.pdf, last accessed March 9, 2015. 

City of Napa, 2014a, Earthquake Recovery Status Report, August 25, 2014, 

2014, http://www.cityofnapa.org 

/index.php?option=com_content&view=article&id=1840%3Aearthquake 

-status-report-as-of-5pm-aug-25&catid=1%3Alatest&Itemid=30, last 

accessed December 5, 2014. 

City of Napa, 2014b, Earthquake Recovery Status Report, September 5, 

2014, http://www.cityofnapa.org 

/index.php?option=com_content&view=article&id=1874%3Aearthquake 

-recovery-status-report-4pm-fri-sept-5&catid=1%3Alatest&Itemid=30, 

last accessed December 5, 2014. 

City of Vallejo, 2014, City of Vallejo Earthquake Recovery, Vallejo, 

California. Available at http://www.ci.vallejo.ca.us/common 

/pages/DisplayFile.aspx?itemId=102604, last accessed, January 28, 2015. 

DSA, 2010, Pendant Mounted Light Fixtures, Interpretation of Regulations 

Document IR16-9, Department of General Services, Division of the State 

Architect, Sacramento, California. Available at 

http://www.documents.dgs.ca.gov/dsa/pubs/IR_16-9_rev11-03-10.pdf, 

last accessed March 5, 2015. 

DSA, 2014, Metal Suspension Systems for Lay-In Panel Ceilings: 2013 CBC, 

Interpretation of Regulations Document IR 25-2.13, Department of 

General Services, Division of the State Architect, Sacramento, 

California. Available at http://www.documents.dgs.ca.gov 

/dsa/pubs/IR_25-2-13_04-08-14.pdf, last accessed March 5, 2015. 

EERI, 1996, Northridge Earthquake Reconnaissance Report, Supplement C 

(Part 2) to Earthquake Spectra. Vol. 11., edited by W. T. Holmes and P. 

Somers, Earthquake Engineering Research Institute, Oakland, California. 

C-2 C: References FEMA P-1024 
 

EERI, 2005, The San Simeon, California, Earthquake, December 22, 2003, 

Earthquake Engineering Research Institute, Oakland, California. 

FEMA, 1998a, Evaluation of Earthquake Damaged Concrete and Masonry 

Wall Buildings: Basic Procedures Manual, FEMA 306, prepared by the 

Applied Technology Council for the Federal Emergency Management 

Agency, Washington, D.C. 

FEMA, 1998b, Evaluation of Earthquake Damaged Concrete and Masonry 

Wall Buildings: Technical Resources, FEMA 307, prepared by the 

Applied Technology Council for the Federal Emergency Management 

Agency, Washington, D.C. 

FEMA, 2012a, Reducing the Risks of Nonstructural Earthquake Damage, 

FEMA E-74, prepared by the Applied Technology Council for the 

Federal Emergency Management Agency, Washington, D.C. Available 

at https://www.fema.gov/earthquake-publications/fema-e-74-reducingrisks-nonstructural-earthquake-damage, last accessed January 28, 2015. 

FEMA, 2012b, Seismic Performance Assessment of Buildings, FEMA P-58, 

prepared by the Applied Technology Council for the Federal Emergency 

Management Agency, Washington, D.C. 

FEMA, 2015, Rapid Visual Screening of Buildings for Potential Seismic 

Hazards: A Handbook, FEMA P-154, prepared by the Applied 

Technology Council for the Federal Emergency Management Agency, 

Washington, D.C. 

GEER, 2015, Geotechnical Engineering Reconnaissance of the August 24, 

2014 M6 South Napa Earthquake, NSF-Funded Geotechnical Extreme 

Events Reconnaissance Association Report No GEER -037, Version 3: 

January 8, 2015. Available at http://www.geerassociation.org 

/GEER_Post%20EQ%20Reports/SouthNapa_2014/GEER_SouthNapa_0 

1-08-2015_reduced.pdf, last accessed January 28, 2015. 

Governor’s Office of Emergency Services, 2003, Guide and Checklist for 

Nonstructural Earthquake Hazards in California Schools, Department of 

General Services, Division of the State Architect, Seismic Safety 

Commission, Department of Education, Sacramento, California. 

Available at http://www.documents.dgs.ca.gov/dsa/pubs/SB1122.pdf, 

last accessed January 28, 2015. 

ICBO, 1982. 1997a, Uniform Building Code, International Conference of 

Building Officials, Whittier, California. 

FEMA P-1024 C: References C-3 
ICBO, 1997b, Uniform Code for Building Conservation, International 

Conference of Building Officials, Whittier, California. 

ICC, 2001, California Historical Building Code, California Code of 

Regulations Title 24, Part 8, developed for the California Building 

Standards Commission, Washington, D.C. 

ICC, 2012a, International Building Code, International Code Council, 

Washington, D.C. 

ICC, 2012b, International Existing Building Code, International Code 

Council, Washington, D.C. 

Napa County Court, 2015, Earthquake Update, Napa, California. Available 

at http://www.napacourt.com, last accessed March 6, 2015. 

NFPA, 2013, Model Manufactured Home Installation Standard, NFPA 225, 

National Fire Protection Association, Quincy, Massachusetts. 

PEER, 2010, Brief Report on the September 3, 2000 Yountville/Napa, 

California Earthquake, by Eduardo Miranda, Hesaam Aslani for the 

Pacific Earthquake Engineering Research Center, Berkeley, California. 

Available at http://peer.berkeley.edu/publications/yountville-napa_sep2000.html, last accessed March 12, 2015. 

PEER, 2014, PEER Preliminary Notes and Observations on the August 24, 

2014 South Napa Earthquake, Pacific Earthquake Engineering Research 

Center Report No. 2014/13, edited by Grace S. Kang and Stephen A. 

Mahin, University of California, Berkeley. Available at 

http://peer.berkeley.edu/publications/peer_reports/reports_2014/webPEE 

R-2014-13-Napa.pdf, last accessed January 28, 2015. 

State of California, 1992, The Effectiveness of Manufactured Home Systems 

during Earthquakes, State of California, Business, Transportation and 

Housing Agency, Department of Housing and Community Development, 

Sacramento, California. 

State of California, 1994, California Code of Regulations, Sacramento, 

California. 

State of California, 2014, California Health and Safety Code, Sacramento, 

California. Available at http://www.leginfo.ca.gov/cgibin/calawquery?codesection=hsc, last accessed March 14, 2015. 

C-4 C: References FEMA P-1024 
Turner, Fred, 2014, personal communication with Bret Lizundia. Mr. Turner 

is the Staff Structural Engineer for the California Seismic Safety 

Commission. 

USGS, 2008, Mapping of the West Napa Fault Zone for Input into the 

Northern California Quaternary Fault Database, U.S. Geological 

Survey External Award Number 05HQAG0002, Menlo Park, California. 

Available at http://earthquake.usgs.gov/research/external 

/reports/05HQAG0002.pdf, last accessed January 28, 2015. 

USGS, 2014, Key Recovery Factors for the August 24, 2014, South Napa 

Earthquake, U.S. Geological Survey Open File Report 2014-1249, 

Menlo Park, California. Available at http://pubs.usgs.gov/of 

/2014/1249/pdf/ofr2014-1249.pdf, last accessed January 28, 2015. 

FEMA P-1024 C: References C-5 

 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 


 

Project Participants 

ATC Management and Oversight 

Christopher Rojahn (Program Executive) 

Applied Technology Council 

201 Redwood Shores Parkway, Suite 240 

Redwood City, California 94065
 

Jon A. Heintz (Program Manager) 

Applied Technology Council 

201 Redwood Shores Parkway, Suite 240 

Redwood City, California 94065
 

FEMA Oversight 

Mike Mahoney (Project Officer)
 

Federal Emergency Management Agency 

500 C Street, SW, Room 416
 

Washington, DC 20472
 

Principal Authors 

John Gillengerten (Co-Project Technical Director) 

5155 Holly Drive 

Shingle Springs, California 95682
 

Contributing Authors 

Kelly Cobeen 

Wiss Janney Elstner Associates, Inc.
 

2000 Powell Street, Suite 1650
 

Emeryville, California 94608 

Bret Lizundia 

Rutherford + Chekene Consulting Engineers
 

55 Second Street, Suite 600 

San Francisco, California 94105
 

Joseph Maffei 

Maffei Structural Engineering 

148 Hermosa Avenue 

Oakland, California 94618
 

Ayse Hortacsu (Project Manager) 

Applied Technology Council 

201 Redwood Shores Parkway, Suite 240 

Redwood City, California 94065
 

Maryann Phipps (Co-Project Technical Director) 

Estructure 

1144 65th Street Suite A 

Oakland, California 94608
 

Joshua Marrow 

Partner Engineering and Science, Inc. 

111 Pine Street 

Suite 1750 

San Francisco, California 94111
 

Bill Tremayne 

Holmes Culley 

235 Montgomery Street 

Suite 1250 

San Francisco, California 94104
 

FEMA P-1024 D: Project Participants D-1 
 

 

Project Working Group 

Veronica Crothers 

Maffei Structural Engineering 

148 Hermosa Avenue 

Oakland, CA 94618 

Sarah Durphy 

Estructure 

1144 65th Street Suite A 

Oakland, California 94608 

Jonas Houston 

Holmes Culley 

235 Montgomery Street 

Suite 1250 

San Francisco, CA 94104 

Alix Kottke 

Estructure 

1144 65th Street Suite A 

Oakland, California 94608 

Project Review Panel 

Dan Kavarian 

City of Napa 

P.O. Box 660 

Napa, California 94559 

Roy Lobo 

Office of Statewide Health Planning and 

Development 

400 R Street 

Suite 200 

Sacramento, California 95811 

Khalid M. Mosalam 

733 Davis Hall 

University of California 

Berkeley, California 94720 

Chiara McKenney 

Estructure 

1144 65th Street Suite A 

Oakland, California 94608 

Karl Telleen 

Maffei Structural Engineering 

148 Hermosa Avenue 

Oakland, California 94618 

Noelle Yuen 

Maffei Structural Engineering 

148 Hermosa Avenue 

Oakland, California 94618 

Marko Schotanus 

Rutherford + Chekene Consulting Engineers 

55 Second Street, Suite 600 

San Francisco, California 94105 

Fred Turner 

Alfred E. Alquist Seismic Safety Commission 

1755 Creekside Oaks Drive #100 

Sacramento, California 95633 

D-2 D: Project Participants FEMA P-1024 
 FEMA P-1024
 

Catalog No. 14331-2