Mitigation Assessment Team Report

Hurricane Irma 

in Florida

Building Performance Observations, 

Recommendations, and Technical Guidance

FEMA P-2023 / December 2018
MITIGATION ASSESSMENT TEAM REPORT

Hurricane Irma in Florida

Building Performance Observations,

Recommendations, and Technical Guidance

FEMA P-2023 / December 2018
Big Pine Key, FL 

FEMA / J.T. BLATTY, 2017
Any opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of 

FEMA. Additionally, neither FEMA nor any of its employees makes any warranty, expressed or implied, or assumes any legal 

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

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

All photographs and figures used in this report were taken by the MAT or developed for this report unless stated otherwise.

Map imagery sources (unless otherwise noted in the report):

Aerial imagery: Google Earth Pro, https://www.google.com/earth/ (used with license, accessed September 2017 through 

November 2018). 

Aerial imagery: Esri World Imagery, http://services.arcgisonline.com/arcgis/rest/services/World_Imagery/MapServer (used 

with license, September 2017 through November 2018).

Topographic imagery: Esri World Topography, http://services.arcgisonline.com/arcgis/rest/services/World_Topo_Map/

MapServer (used with license, September 2017 through November 2018).

Copyright information:

Figures on 1609.3(1) and 1609.3(2) are excerpted from the 2017 Florida Building Code-Building Sixth Edition; Copyright 2017

Figure R301.2(4) is excerpted from the 2017 Florida Building Code-Residential Sixth Edition; Copyright 2017 

Washington, D.C.: International Code Council. 

Reproduced with permission. All rights reserved. www.ICCSAFE.org

The definition for Wind-Borne Debris Region and Section R301.2.1.2 are excerpted from the 2017 Florida Building Code 

(6th Edition); Copyright 2017

Washington, D.C.: International Code Council.

Reproduced with permission. All rights reserved. www.ICCSAFE.org
Members of the Mitigation Assessment Team

Team Leader Team Manager Report Manager

Gregory Wilson Manuel Perotin, PE, CFM Samantha N. Krautwurst, PE

FEMA CDM Smith AECOM

Team Members

Bill Blanton, CFM

FEMA

Frances Bui, PE

CDM Smith

Erin Cobb, CFM

FEMA

Bill Coulbourne, PE, F.SEI, F.ASCE

AECOM

Christopher P. Jones, PE

Durham, NC

Samantha N. Krautwurst, PE

AECOM

William Maples, PE

CDM Smith

Steve Martin, CFM, CPM

Florida Division of Emergency 

Management

Sean McGowan, PE

FEMA

Robert Nystrom, PE

CDM Smith

Glenn Overcash, PE

AECOM

Manuel Perotin, PE, CFM

CDM Smith

John “Bud” Plisich

FEMA

Rebecca Quinn, CFM

RCQuinn Consulting, Inc.

Eric Stafford, PE

AECOM

Stuart Ulsh

FM Global

Internal Support

GIS Specialist:

Betsy Hicks, PE, CFM, AECOM

Caitlin Olson, CDM Smith

Graphic Artists:

Lee-Ann Lyons, AECOM

Billy Ruppert, AECOM

Technical Editors and Formatting:

Young Cho, AECOM

Susan Ide Patton, PG, AECOM

Ivy Porpotage, AECOM

Amy Siegel, AECOM

508 Compliance:

Carol Cook, AECOM
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT i

Executive Summary 

Hurricane Irma struck Florida’s coast on September 10, 2017, as 

a low Category 4 storm and caused building damage across the 

entire affected area. 

Hurricane Irma made landfall on the East Coast of the 

United States at Cudjoe Key, FL, with maximum winds 

near 130 miles per hour (mph) and a minimum pressure 

of 931 millibars (mb) (NOAA NHC, 2018). Later that 

day, Hurricane Irma made a second landfall on Marco 

Island as a low Category 3 hurricane with maximum 

sustained winds of 115 mph and a central pressure of 936 

mb before tracking up the Florida Peninsula and into 

Georgia on September 11 (NOAA NWS, 2017). Sustained 

hurricane force winds (i.e., 74 mph or greater) were 

reported along much of the east coast of Florida, from 

Jacksonville to Miami. The Naples Municipal Airport 

reported a wind gust of 142 mph. In addition to the long 

periods of heavy rain and strong winds, storm surge 

caused flooding along the Florida coast, particularly on 

the east side of the State in the Jacksonville area (NOAA 

NHC, 2018; NOAA NWS, 2017). 

Hurricane Irma resulted in one of the largest evacuations (approximately 6.5 million people) and 

most extensively used sheltering operations for the State of Florida (Florida House of Representatives, 

2018). Presidential disaster declarations were issued for Florida, Georgia, Puerto Rico, and the U.S. 

Virgin Islands following the storm (FEMA, 2018c). Hurricane Irma caused damage to buildings 

across the entire affected area, as well as widespread power outages and interruptions in utility 

service. 

NOTEWORTHY STORM 

METRICS 

•	 One of the strongest hurricanes 

ever observed in the open 

Atlantic Ocean 

•	 One of only five hurricanes with 

measured sustained winds of 

185 miles per hour (mph) or 

higher 

•	 Maintained 185 mph sustained 

wind speed for 37 hours, the 

longest period for any tropical 

cyclone
ii MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

EXECUTIVE SUMMARY

Mitigation Assessment Team Deployment and Observations 

Twelve days after Hurricane Irma struck the Florida coast (September 22–25, 2017), the Federal 

Emergency Management Agency (FEMA) deployed a pre-Mitigation Assessment Team (pre-MAT) 

to perform a preliminary field assessment of building damage in limited areas of Collier, Lee, 

Miami-Dade, and Monroe Counties. This pre-MAT was a small team sent in advance of the larger 

MAT to quickly observe and record select perishable damage data; locate damaged areas requiring 

further assessment; and determine the overall impact of the hurricane, scope of buildings and areas 

to be visited, and skillsets that would be needed for the larger, follow-on MAT. Following the preMAT, in response to a request for technical support from the Joint Field Office (JFO) in Florida, 

FEMA deployed the full MAT in December 2017 to assess the performance of buildings in Florida. 

A MAT conducts forensic engineering analyses of buildings and related infrastructure to determine 

causes of damage and success, and recommends actions that Federal, State, and local governments; 

the design and construction industry; and building code and standards organizations can take to 

mitigate damage from future natural hazard events. 

The MAT deployed to Florida assessed the performance of municipal buildings, coastal residential 

properties, and public facilities. The MAT focused on structures in Lee, Collier, Miami-Dade, and 

Monroe Counties. 

Summary of Damage Observed by the MAT 

Although Hurricane Irma was neither a flood nor wind design-level event, the storm caused 

widespread damage to residential and commercial buildings and infrastructure. Other long-term 

damage impacts include the loss of housing in the Florida Keys, damage to wastewater and potable 

water infrastructure, and minor to major erosion at different locations along the coastline. The 

extent of the wind and/or flood damage varied depending on the nature of the building design 

and construction. Chapters 3 and 4, as well as Chapter 5, provide additional insight into why a below 

design-level event caused the damage that it did. 

Flood. The storm caused moderate flooding and erosion in South Florida but was not considered a 

storm surge design event (i.e., exceedance of the 1-percent-annual-chance flood elevations was only 

observed where the combination of storm surge and rainfall caused severe flooding). Buildings in 

low-lying areas were damaged from inundation. 

Although inundation alone was a significant source of damage, some of the more dramatic 

structural failures observed were a result of the added force of wave action and scour. The extent of 

flood damage to buildings varied with the depth of floodwater, the amount of energy in the water 

(waves, velocity), and the nature of building design and construction (old versus new, at-grade versus 

elevated, manufactured housing [MH] units / recreational vehicle versus site-built/modular). Some 

of the structures destroyed by the storm were MH units located in the floodplain. Very few of these 

houses were elevated to the base flood elevation. Buildings constructed at or near grade were subject 

to deeper and more damaging flooding from either storm surge or rainfall-induced flooding. 

The MAT also spoke with building owners, operators, and managers of dry floodproofed nonresidential buildings to understand the performance of dry floodproofing systems. 

In addition, the MAT visited 15 public restroom buildings and sites on or near the shoreline in public 

parks in Lee, Collier, Monroe, and St. Johns Counties. For those restrooms damaged by flooding, iii 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT iii

EXECUTIVE SUMMARY

the degree of damage ranged from complete destruction, to some structural damage, to damage to 

doors and fixtures only. The degree of damage depended on both flood conditions and building 

characteristics. 

Wind. The MAT focused primarily on one- and two-family dwellings, but also assessed some multifamily dwellings (apartments and condominiums) and MH units. Estimated wind speeds from 

Hurricane Irma in Florida did not approach the design wind speeds required in the last six editions 

of the Florida Building Code (FBC). 

Buildings designed and constructed to comply with the FBC met expectations by performing well 

structurally. Though not widespread, wind-induced structural damage to main wind-force resisting 

systems was observed in older (pre-FBC) residential construction and included roof failure and loss 

of exterior walls. Wind damage to roof structures appeared to have been generally initiated through 

loss of roof covering or breaching of the attic envelope. Framed walls of residential structures 

collapsed where significant portions of the roof and ceiling diaphragm were destroyed by wind. 

Many buildings sustained wind-induced failures of building envelope components, connections, 

and systems that allowed wind-driven rain to penetrate into the interior, resulting in costly damage. 

While structural damage observations from Hurricane Irma winds were almost exclusively limited 

to pre-FBC residential buildings, envelope damage was commonly observed on both older and 

newer construction. The most frequently observed damage affected roof coverings, soffits, exterior 

wall coverings, glazed openings, and garage doors. 

Most observed damage to MH units was initiated by wind acting on improperly attached 

appurtenances. When carports and covered porches broke away from MH units, they left openings 

at failed connections in the remaining roof or wall that allowed rain to enter the MH unit envelopes. 

MAT Recommendations 

The recommendations presented in this report are made based on the MAT’s field observations. 

They are directed to design professionals, contractors, building officials, facility managers, 

floodplain administrators, regulators, emergency managers, building owners, academia, select 

industries and associations, and local officials, as well as FEMA. 

General recommendations. The Florida Division of Emergency Management (FDEM), the 

Building Officials Association of Florida (BOAF), Florida Home Builders Association (FHBA), 

and/or other stakeholders should consider developing additional training opportunities regarding 

contemporary flood- and wind-related design and construction issues. The FDEM should continue 

to encourage pre-event evaluation of post-disaster needs and inform building officials and local 

officials responsible for floodplain management about accessing resources to aid recovery through 

the Statewide Mutual Aid Agreement. FDEM should also consider training design professionals to 

assist with inspections. Furthermore, FEMA should develop a timely and effective means to deliver 

the Adjuster Preliminary Damage Assessment data submitted by National Flood Insurance Program 

(NFIP) claims adjusters to States and communities. 

Building codes and floodplain management ordinances. Permitting agencies (e.g., Florida 

Department of Environmental Protection [DEP], Water Management Districts, local government) 

should evaluate permitting criteria and performance requirements for new or replacement 

bulkheads with respect to design conditions, including the effects of saturated backfill, wave 

forces, overtopping, and erosion on both water and land sides. Recommendations related to FEMA 
iv MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

EXECUTIVE SUMMARY

reviewing and updating its event-based erosion methodology. FDEM should expand its technical 

assistance for Community Rating System (CRS) communities are also provided. The Florida 

Department of Highway Safety and Motor Vehicles should update its Florida statutes for MH unit 

installation to reference the most recent edition of FEMA P-85, Protecting Manufactured Homes from 

Floods and Other Hazards (2009c), and consider incorporating additional wind- and flood-resistant 

construction provisions with particular emphasis on anchoring. 

Flood-related building performance. Because dry floodproofing measures were found to fail under 

less than design flood conditions, the MAT recommends that building owners, design professionals, 

and local floodplain administrators follow the guidance in Florida MAT Recovery Advisory 1, 

Dry Floodproofing: O perational C onsiderations ( 2018d), a nd T exas M AT R ecovery A dvisory 1 , Dry 

Floodproofing: Planning and Design Considerations (2018e), related to dry floodproofing methods and 

procedures. These methods and procedures were developed based on observations during and after 

the two storms. Facility managers should develop an emergency operations plan that outlines how 

to prepare the building when severe weather is expected. Facility managers should also routinely reevaluate dry floodproofing designs and plans after deployment of their systems or training exercises, 

as well as instill a culture of preparedness. 

Wind-related building performance. Because building envelope failures were observed on post-FBC 

residential structures following a below design-level wind event, industry groups should investigate 

the causes. In particular, the causes for the observed widespread asphalt shingle roof covering loss 

and the appropriate pressure equalization factor for vinyl siding should be investigated. Industry 

groups and/or academia should also study debris impacts to protective systems from the 2017 (and 

future) hurricanes to determine whether the current wind speed triggers for the wind-borne debris 

region (WBDR) are appropriate as defined in the American Society of Civil Engineers (ASCE) 

standard ASCE 7, Minimum Design Loads for Buildings and Other Structures. Building owners outside of 

the WBDR, in the hurricane-prone region, should consider protecting the glazed openings on their 

buildings. Contractors and inspectors should ensure roof covering repairs and replacements are 

in conformance with FBC requirements. Designers, contractors, and inspectors should place more 

emphasis on proper soffit installation to limit w ind-driven rain from entering building envelopes 

and damaging building interiors. The FBC should require soffit and wall cladding inspections. 

Furthermore, as a best practice, MH appurtenances should be built as standalone units without 

structural connection to the MH unit. 

FEMA technical publications and guidance. The FEMA Building Science Branch should complete 

Guidelines for Wind Vulnerability Assessments for Critical Facilities. FEMA should include lessons learned 

from the 2017 hurricane season in finishing this publication. FEMA should also consider updating 

or producing a supplement for its key hurricane and Risk Management Series technical guidance 

publications to include lessons learned from the 2017 hurricane season and to reflect updates to 

current building codes since the publications’ latest releases. FEMA should update FEMA P-758, 

Substantial Improvement/Substantial Damage Desk Reference (2010) to incorporate new lessons 

learned and recommended guidance and clarifications since it was published in 2010. At 

the same time FEMA 213, Answers to Questions about Substantially Damaged Buildings, should 

be updated to be consistent with the updated FEMA P-758. FEMA should consider expanding 

existing training materials on Substantial Improvement/Substantial Damage for distribution to 

NFIP State Coordinators and other entities. Finally, dry floodproofing guidance should be updated 

and a comprehensive recommendation for dry floodproofing de sign, li mitations, te sting, an d 

maintenance and operations requirements should be developed for inclusion in ASCE 24, Flood 

Resistant Design and Construction.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT v

Contents

Executive Summary .................................................................................................................................... i

Mitigation Assessment Team Deployment and Observations ...............................................................ii

Summary of Damage Observed by the MAT .........................................................................................ii

MAT Recommendations .........................................................................................................................iii

Acronyms and Abbreviations ................................................................................................................xvi

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

1.1 Organization of the Report ...................................................................................................... 1-2

1.2 Hurricane Irma: The Event ...................................................................................................... 1-3

1.2.1 Storm Surge Flooding .................................................................................................. 1-6

1.2.2 Rainfall .........................................................................................................................1-11

1.2.3 Wind .............................................................................................................................1-12

1.2.4 Tornadoes .....................................................................................................................1-14

1.3 Hurricane Irma: The Impact ..................................................................................................1-14

1.4 Regional Preparedness Actions .............................................................................................. 1-15

1.5 FEMA Mitigation Assessment Team ...................................................................................... 1-15

1.5.1 Hurricane Irma MAT ..................................................................................................1-16
vi MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

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1.5.2 Team Composition ......................................................................................................1-16

1.5.3 Methodology ................................................................................................................1-16

Chapter 2. Building Codes, Standards, and Regulations ..........................................................................2-1

2.1 Building Codes in Florida ........................................................................................................ 2-2

2.1.1 Florida Building Commission ...................................................................................... 2-3

2.1.2 Local Amendments ...................................................................................................... 2-4

2.2 Floodplain Management in Florida .........................................................................................2-4

2.2.1 History of Flood Provisions in the Florida Building Code ........................................ 2-6

2.2.2 Flood Provisions in the Florida Building Code .......................................................... 2-7

2.2.3 Local Amendments to the Flood Provisions of the FBC ............................................ 2-8

2.2.4 Floodplain Management Ordinances Coordinated with the FBC ..........................2-10

2.3 Wind Provisions of the Florida Building Code ..................................................................... 2-11

2.3.1 Wind Loads and Wind Design in the FBC .................................................................2-11

2.3.2 Florida-Specific Amendments for Wind and Water Intrusion ................................2-15

2.4 Florida Manufactured Housing Installation Standards ....................................................... 2-16

Chapter 3. Flood-Related Observations ................................................................................................... 3-1

3.1 General Flood Damage Observations ......................................................................................3-3

3.1.1 Erosion and Scour ...................................................................................................... 3-10

3.1.2 Erosion Control Structures ........................................................................................ 3-19

3.2 Performance of Dry Floodproofing Measures .......................................................................3-22

3.2.1 Failure Modes ............................................................................................................. 3-22

3.2.2 Implementation Considerations ................................................................................ 3-26

3.2.3 Operations and Maintenance Plans ......................................................................... 3-26

3.3 Performance of Public Restrooms ..........................................................................................3-26

Chapter 4. Wind-Related Observations ................................................................................................... 4-1

4.1 Main Wind-Force Resisting System Performance ...................................................................4-2

4.1.1 Roof Failure................................................................................................................... 4-2

4.1.2 Wall Failure ...................................................................................................................4-4

4.2 Envelope ....................................................................................................................................4-6
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT vii

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4.2.1 Roof Coverings ..............................................................................................................4-6

4.2.1.1 Asphalt Shingles ............................................................................................4-6

4.2.1.2 Roof Tile ........................................................................................................ 4-9

4.2.1.3 Metal Roof Systems ..................................................................................... 4-10

4.2.2 Soffits ........................................................................................................................... 4-11

4.2.2.1 Vinyl ............................................................................................................. 4-12

4.2.2.2 Metal ............................................................................................................ 4-15

4.2.3 Exterior Wall Coverings ..............................................................................................4-17

4.2.3.1 Vinyl Siding Installation Issues .................................................................. 4-21

4.2.3.2 Vinyl Siding Design Pressure Ratings and the Pressure 

Equalization Factor ..................................................................................... 4-23

4.2.4 Glazed Openings and Opening Protection Systems ................................................ 4-24

4.2.4.1 Impact-Resistant Glazing ............................................................................ 4-25

4.2.4.2 Impact-Resistant Coverings ....................................................................... 4-27

4.2.5 Garage Doors .............................................................................................................. 4-28

4.3 Manufactured Housing Units ................................................................................................4-29

4.3.1 Anchoring ...................................................................................................................4-30

4.3.2 Other Observations .................................................................................................... 4-32

Chapter 5. Recommendations and Conclusions ...................................................................................... 5-1

5.1 Overview of Conclusions and Recommendations ...................................................................5-2

5.2 General Conclusions and Recommendations .........................................................................5-3

5.3 Building Codes, Standards, and Regulations..........................................................................5-4

5.4 Flood-Related Building Performance ......................................................................................5-6

5.5 Wind-Related Building Performance .......................................................................................5-7

5.6 FEMA Technical Publications and Guidance .........................................................................5-9

5.7 Summary of Conclusions and Recommendations ................................................................5-12

Appendices

Appendix A: Acknowledgments ............................................................................................................A-1

Appendix B: References ....................................................................................................................... B-1

Appendix C: Recovery Advisories ........................................................................................................ C-1
viii MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

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List of Figures

Figure 1-1: Composite satellite image from the GOES-13 weather satellite of landfall near 

the Florida Keys (left) on September 10, 2017 8:15 AM ............................................... 1-4

Figure 1-2: Hurricane Irma cone of probable track forecast on Thursday, September 7 

(upper) and most likely arrival of tropical storm force winds on Sunday, 

September 10 (lower) ...................................................................................................... 1-5

Figure 1-3: Surveyed locations of Hurricane Irma’s high water marks ............................................1-7

Figure 1-4: Surveyed locations of Hurricane Irma’s high water marks in Lee and Collier 

Counties ........................................................................................................................... 1-8

Figure 1-5: Surveyed locations of Hurricane Irma’s high water marks in Miami-Dade County ... 1-9

Figure 1-6: Surveyed locations of Hurricane Irma’s high water marks in Monroe County ..........1-10

Figure 1-7: Map of rainfall totals associated with Hurricane Irma (or its remnants) ..................1-12

Figure 1-8: Comparison of gusts experienced during Hurricane Irma (left) with ASCE 

7-10 design 3-second wind gusts (right) ........................................................................1-13

Figure 1-9: Field locations visited by the pre-MAT ..........................................................................1-18

Figure 1-10: Field locations visited by the MAT Wind and Flood Units after Hurricane 

Irma. The inset map shows the locations of field visits in St. Johns County to 

evaluate erosion impacts. .............................................................................................. 1-20

Figure 2-1: FBC and local regulations meet or exceed the NFIP requirements ............................ 2-7

Figure 2-2: Wind speed map for Risk Category II buildings and other structures .......................2-12

Figure 2-3: Wind speed map for Risk Category III and IV buildings and other structures .........2-13

Figure 2-4: Wind speed map for FBCR buildings ............................................................................2-14

Figure 3-1: Locations of selected September 22–25, 2017 (pre-MAT) observations for 

Hurricane Irma ................................................................................................................ 3-2

Figure 3-2: Locations of selected December 10–15, 2017 and February 14–15, 2018 (MAT) 

observations for Hurricane Irma .................................................................................... 3-3

Figure 3-3: Typical range in flood damage observed along Avenue D, in order along the 

street as indicated (Big Pine Key, FL) ............................................................................3-4

Figure 3-4: Long-duration flooding in the Bonita Springs area (Lee County, FL) .......................3-5
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT ix

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Figure 3-5: Elevated house with unreinforced masonry breakaway walls that performed as 

intended (Big Pine Key, FL) ...........................................................................................3-6

Figure 3-6: House constructed at grade where the masonry walls parallel to the shoreline 

were destroyed; this house was near the house shown in Figure 3-5 

(Big Pine Key, FL) ...........................................................................................................3-6

Figure 3-7: Example of a breakaway wall that was reported by a local code official to have 

performed as intended (Lower Matecumbe Key, FL) ................................................... 3-7

Figure 3-8: Example of partial failure of breakaway wall, with no associated damage to 

main structure observed (Cudjoe Key, FL) ................................................................... 3-7

Figure 3-9: Example of a breakaway wall failure that likely contributed to damage to 

columns (Big Pine Key, FL) ............................................................................................3-8

Figure 3-10: Building debris and recreational vehicles washed into a canal on 61st Street 

Ocean (Marathon, FL) ....................................................................................................3-8

Figure 3-12: Car and debris that washed into a house (Big Pine Key, FL) ....................................... 3-9

Figure 3-11: Boat and small debris that washed across a canal and onto houses 

(Big Pine Key, FL) .......................................................................................................... 3-9

Figure 3-13: Shed that washed across Highway US 1 (Grassy Key, FL) ........................................... 3-10

Figure 3-14: Scour near and around building foundation (Lower Matecumbe Key, FL) ............ 3-11

Figure 3-15: Scour was likely due to waves and high-velocity flow at this house on Long 

Beach Drive (same house is shown in Figure 3-6) (Big Pine Key, FL) ...................... 3-12

Figure 3-16: Erosion was likely due to wave attack around the foundation of this house on 

Sombrero Beach Road (Marathon, FL) ....................................................................... 3-12

Figure 3-17: Collapsed building (Lower Matecumbe Key, FL) ....................................................... 3-13

Figure 3-18: Undermined house on deep piles that survived erosion (Vilano Beach, FL) ............3-14

Figure 3-19: Undermined houses constructed on top of the dune (Vilano Beach, FL) .................3-14

Figure 3-20: Collapsed house on shallow foundation that was undermined by erosion 

induced by Hurricane Irma (Vilano Beach, FL) ........................................................ 3-15

Figure 3-21: Locations of FIS transects 28–39, where comparative beach and dune 

profiles are shown in Figure 3-22 through Figure 3-26 (R-numbers are survey 

monuments established by the State of Florida) ......................................................... 3-16

Figure 3-22: Beach and dune profiles at Transect 28 ........................................................................3-17
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Figure 3-23: Beach and dune profiles at Transect 30 ........................................................................3-17

Figure 3-24: Beach and dune profiles at Transect 33 ....................................................................... 3-18

Figure 3-25: Beach and dune profiles at Transect 37 ....................................................................... 3-18

Figure 3-26: Beach and dune profiles at Transect 39 ....................................................................... 3-19

Figure 3-27: Failure of bulkhead (anchor system) (Naples, FL) ..................................................... 3-20

Figure 3-28: Bulkhead toe failure (insufficient embedment) (Naples, FL) ................................... 3-20

Figure 3-29: House on a shallow foundation that collapsed after it was undermined 

following failure of the bulkhead during Hurricane Irma 

(St. Johns County, FL) .................................................................................................. 3-21

Figure 3-30: Flood plank system deployed at utility company building (Key West, FL) ................ 3-23

Figure 3-31: A high-rise residential building under construction was successfully protected 

by a dry floodproofing method that used flood panels and doors; the 

floodproofing was installed by the building contractor (Miami, FL) ........................ 3-24

Figure 3-32: Floodproofing system components at a historic building (top); parts of the 

system failed and approximately 3 feet of flooding infiltrated part of the 

building (Miami, FL) .................................................................................................... 3-25

Figure 3-33: Elevated restrooms with ground-level enclosure. Bunche Beach Preserve 

restroom (Site 1; Lee County), where the degree of flooding in the enclosure, 

if any, would have been shallow. ................................................................................... 3-29

Figure 3-34: Elevated restrooms with ground-level enclosure. Lovers Key State Park 

restroom (Site 2; Lee County) enclosure sustained shallow flooding but no 

damage during Hurricane Irma. ..................................................................................3-30

Figure 3-35: Elevated restroom at Barefoot Beach Preserve County Park 

(Site 3; Collier County) .................................................................................................3-30

Figure 3-36: Elevated restrooms (Site 4; City of Naples Pier) .......................................................... 3-31

Figure 3-37: Elevated restroom at Tigertail Beach Park (Site 5; Marco Island, Collier County) .. 3-32

Figure 3-38: Grade-level restrooms at Marco Island (Site 6; Collier County) ................................ 3-32

Figure 3-39: Elevated restrooms at Sombrero Beach Park without ground-level enclosure 

and that sustained no flood damage during Hurricane Irma (Site 7; Marathon) ... 3-33
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Figure 3-40: Elevated Long Key State Park restroom without ground-level enclosure and 

that sustained no flood damage during Hurricane Irma 

(Site 9; Monroe County) ............................................................................................... 3-33

Figure 3-41: Restroom in Long Key State Park that sustained structural flood damage 

(Site 10; Monroe County) ............................................................................................. 3-34

Figure 3-42: Elevated restroom with ground-level enclosure at Bahia Honda State Park, 

Sandspur Campground; Hurricane Irma flood depth in enclosure was 5 feet 

(Site 12; Monroe County) ............................................................................................. 3-34

Figure 3-43: Elevated restroom at Bahia Honda State Park, Loggerhead 

(Site 13; Monroe County) ............................................................................................. 3-35

Figure 3-44: Grade-level Veterans Memorial Park restroom that was likely exposed to Zone 

V conditions (Site 14; Monroe County) ....................................................................... 3-36

Figure 3-45: Grade-level Vilano Beach Surfside Park restrooms (Site 15; St. Johns County) ....... 3-37

Figure 4-1: House with structural damage to roof system (EWS = 113 mph; 

EDWS = 180 mph) (Sugarloaf Key) ................................................................................ 4-3

Figure 4-2: Residence where a roof-to-wall connection failed (EWS = 78 mph; 

EDWS = 169 mph) (Miami) ............................................................................................ 4-3

Figure 4-3: South end of east-facing wall; the south end of the roof remained in place 

(EWS = 113 mph; EDWS = 180 mph) (Cudjoe Key) ......................................................4-4

Figure 4-4: North end of east-facing wall where the roof was (EWS = 113 mph; 

EDWS = 180 mph) (Cudjoe Key) ....................................................................................4-5

Figure 4-5: Remainder of the screened porch and exterior wall (EWS = 113 mph; 

EDWS = 180 mph) (Cudjoe Key) ....................................................................................4-5

Figure 4-6: House with roof structure loss and collapse of the second floor exterior wall 

and adjacent deck (EWS = 113 mph; EDWS = 180 mph) (Ramrod Key) .....................4-6

Figure 4-7: The MAT could not observe much of the asphalt roof damage on this house 

because it was covered by a tarp (EWS = 111 mph; EDWS = 180 mph) 

(Big Coppitt Key) ............................................................................................................. 4-7

Figure 4-8: Asphalt shingle loss shown inside yellow ovals for house shown in Figure 4-7 

(EWS = 111 mph; EDWS = 180 mph) (Big Coppitt Key) ............................................... 4-7

Figure 4-9: House with asphalt shingle loss as evidenced by tarp (EWS = 120 mph; 

EDWS = 180 mph) (Marathon)....................................................................................... 4-7
xii MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

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Figure 4-10: Residence that lost shingles near the ridge (EWS = 113 mph; 

EDWS = 180 mph) (Sugarloaf Key) ................................................................................4-8

Figure 4-11: Recommended asphalt shingle nail locations for high wind regions ..........................4-8

Figure 4-12: House with shingle loss near main ridge and between roof hips (yellow oval) 

(EWS = 109 mph; EDWS = 170 mph) (Marco Island) ................................................... 4-9

Figure 4-13: Roof tile failure (EWS = 113 mph; EDWS = 180 mph) (Cudjoe Key) .......................... 4-9

Figure 4-14: House lost roof tiles across most of its front eaves (red arrows) 

(EWS = 111 mph; EDWS = 180 mph) (Duck Key) ....................................................... 4-10

Figure 4-15: House with separated metal roof trim and missing fascia cover (red ovals) 

along gable end. (EWS = 113 mph; EDWS = 180 mph) (Sugarloaf Key) ................... 4-11

Figure 4-16: House with damaged metal roof system (EWS = 113 mph; EDWS = 180 mph) 

(Sugarloaf Key) .............................................................................................................. 4-11

Figure 4-17: House that lost its vinyl soffit panel (EWS = 113 mph; EDWS = 180 mph) 

(Summerland Key) ........................................................................................................ 4-12

Figure 4-18: House that lost its soffit along the right side of the front-facing gable 

(EWS = 114 mph; EDWS = 180 mph) (Little Torch Key) ............................................ 4-13

Figure 4-19: House with vinyl soffit damage not caused by fascia loss (EWS = 113 mph; 

EDWS = 180 mph) (Sugarloaf Key) .............................................................................. 4-13

Figure 4-20: Dwelling with similar soffit panel attachment and loss as shown in Figure 4-19 

(EWS = 113 mph; EDWS = 180 mph) (Sugarloaf Key) .................................................4-14

Figure 4-21: House with soffit loss (EWS = 110 mph; EDWS = 169 mph) (Goodland) ...................4-14

Figure 4-22: Metal soffit loss on house (EWS = 113 mph; EDWS = 180 mph) (Ramrod Key) ....... 4-15

Figure 4-23: House with metal soffit loss below missing fascia cover (EWS = 114 mph; 

EDWS = 180 mph) (Big Pine Key) ................................................................................ 4-15

Figure 4-24: Apartment building with metal soffit panel loss (EWS = 104 mph; 

EDWS = 166 mph) (Naples) .......................................................................................... 4-16

Figure 4-25: Metal soffit panel loss apartment gable end overhang (EWS = 104 mph; 

EDWS = 166 mph) (Naples) ...........................................................................................4-17

Figure 4-26: Vinyl siding lost along the back of a house (EWS = 113 mph; 

EDWS = 180 mph) (Sugarloaf Key) .............................................................................. 4-19
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT xiii

TABLE OF CONTENTS

Figure 4-27: House that lost vinyl siding on its gable end wall (EWS = 120 mph; 

EDWS = 180 mph) (Marathon Key) ............................................................................. 4-21

Figure 4-28: Duplex where vinyl siding above the front porch did not comply with 

manufacturer’s installation instructions (EWS = 120 mph; EDWS = 180 mph) 

(Marathon Key) ............................................................................................................. 4-22

Figure 4-29: House appeared to lack utility trim under the windows, as shown in the red 

outline (EWS = 120 mph; EDWS = 180 mph) (Marathon Key) .................................. 4-22

Figure 4-30: House that lacked a proper starter strip, as shown in the red outline 

(EWS = 114 mph; EDWS = 180 mph) (Little Torch Key) ............................................ 4-23

Figure 4-31: House with irregular fastener pattern and apparent lack of a proper starter 

strip (EWS = 114 mph; EDWS = 180 mph) (Little Torch Key) .................................... 4-23

Figure 4-32: Residence with two windows where the outer panes were broken (see red 

arrows) but the inner panes stayed intact (EWS = 113 mph; EDWS = 180 mph) 

(Ramrod Key) ................................................................................................................ 4-25

Figure 4-33: House damaged by wind-borne debris (EWS = 114 mph; EDWS = 180 mph) 

(Little Torch Key) .......................................................................................................... 4-26

Figure 4-34: Wind-borne driven missile damaged second floor door at the same house as 

shown in Figure 4-33 (EWS = 114 mph; EDWS = 180 mph) (Little Torch Key) ....... 4-26

Figure 4-35: House with impact-resistant shutter system damaged by wind-borne debris; 

opening was covered at the time the MAT visited (EWS = 114 mph; 

EDWS = 180 mph) (Little Torch Key) .......................................................................... 4-27

Figure 4-36: House with corrugated metal shutters (EWS = 110 mph; EDWS = 169 mph) 

(Goodland) .................................................................................................................... 4-28

Figure 4-37: Damaged overhead garage doors (EWS = 114 mph; EDWS = 180 mph) 

(Little Torch Key) .......................................................................................................... 4-28

Figure 4-38: Damaged overhead garage door on a house (EWS = 111 mph; 

EDWS = 180 mph) (Duck Key) ..................................................................................... 4-29

Figure 4-39: Anchorage on a new MH unit installation (EWS = 105 mph; EDWS = 164 mph) 

(Collier County) ............................................................................................................4-30

Figure 4-40: Consistent anchorage pattern observed on a new MH unit installation 

(EWS = 105 mph; EDWS = 164 mph) (Collier County) ..............................................4-30

Figure 4-41: New MH unit installation with misaligned anchor strap installation 

(red outline) was otherwise anchored consistently with other post-Irma 

examples(EWS = 105 mph; EDWS = 164 mph) (Collier County)............................... 4-31
xiv MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

TABLE OF CONTENTS

Figure 4-42: MH unit installation where only the first and fourth straps are attached to the 

exterior wall base (EWS = 111 mph; EDWS = 180 mph) (Big Coppitt Key) .............. 4-31

Figure 4-43: MH unit installation with straps spaced at approximately 3 feet on center and 

attached to the exterior wall base, but with loose anchor strap shown in red 

outline (EWS = 120 mph; EDWS = 180 mph) (Marathon Key) .................................. 4-32

Figure 4-44: This MH unit sustained exterior wall damage that was initiated by the loss of 

the attached screened porch (EWS = 115 mph; EDWS = 164 mph) 

(Everglades City) ............................................................................................................ 4-33

Figure 4-45: MH unit that was damaged when its screened porch was lost to high winds 

(EWS = 105 mph; EDWS = 166 mph) (Collier County) .............................................. 4-33

Figure 4-46: MH unit where carport detached from the unit, opening the building 

envelope across the top of a wall (EWS = 105 mph; EDWS = 166 mph) 

(Collier County) ............................................................................................................4-34

List of Tables

Table 1-1: Comparison of Hurricane Irma Wind Speed to Other Major Atlantic Hurricanes ........ 1-3

Table 1-2: Water Surface Elevations and Estimated Return Periods in South Florida Counties ....1-11

Table 2-1: Notable Florida-Specific Amendments for Wind and Water Intrusion ...........................2-15

Table 3-1: Summary of Public Restrooms Visited.............................................................................. 3-27

Table 5-1: Summary of Conclusions and Recommendations.............................................................5-14
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT xv

ACRONYMS AND ABBREVIATIONS

Acronyms and Abbreviations

AAMA American Architectural Manufacturers Association 

ACE Accumulated Cyclone Energy 

ACI American Concrete Industry 

ADCIRC Advanced Circulation 

AISI American Iron and Steel Institute 

ASCE American Society of Civil Engineers 

ASD allowable stress design 

ATC Applied Technology Council 

BCIS Building Code Information System 

BFE base flood elevation 

BOAF Building Officials Association of Florida 

CAC Community Assistance Contact 

CAP-SSSE Community Assistance Program State Support Services Element 

CAV Community Assistance Visits 

CERA Coastal Emergency Risks Assessment 

CFR Code of Federal Regulations 

CPCB Community Planning and Capacity Building 

CRS Community Rating System 

DBPR Department of Business and Professional Regulation 

DEP Department of Environmental Protection (Florida) 

DFE design flood elevation 

DHS U.S. Department of Homeland Security 

EDT Eastern Daylight Time 

EDWS estimated design wind speed 

EOP emergency operations plan 

EWS estimated wind speed 

FBC Florida Building Code 

FBCA Florida Building Code, Accessibility 

FBCB Florida Building Code, Building 

FBCEB Florida Building Code, Existing Building 

FBCEC Florida Building Code, Energy Conservation 

FBCFG Florida Building Code, Fuel Gas 

FBCM Florida Building Code, Mechanical 

FBCP Florida Building Code, Plumbing 

FBCR Florida Building Code, Residential 

FDEM Florida Division of Emergency Management 

FEMA Federal Emergency Management Agency 
xvi MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

ACRONYMS AND ABBREVIATIONS

FFMA Florida Floodplain Managers Association

FHBA Florida Home Builders Association 

FIMA Federal Insurance and Mitigation Administration 

FIRM Flood Insurance Rate Map 

FIS Flood Insurances Study 

HUD U.S. Department of Housing and Urban Development 

HVHZ High-Velocity Hurricane Zone 

IBC® International Building Code 

ICC® International Code Council 

IRC® International Residential Code 

JFO Joint Field Office 

MAT Mitigation Assessment Team 

MEP mechanical, electrical, and plumbing 

MH manufactured housing 

mph miles per hour 

MWFRS main wind-force resisting systems 

NAVD88 North American Vertical Datum of 1988 

NCEI National Center for Environmental Information 

NDRF National Disaster Recovery Framework 

NFIP National Flood Insurance Program 

NGVD29 National Geodetic Vertical Datum of 1929 

NHC National Hurricane Center 

NHRAP Natural Hazard Risk Assessment Program 

NOAA National Oceanic and Atmospheric Administration 

NSF National Science Foundation 

NWS National Weather Service 

PEF pressure equalization factor 

Risk MAP FEMA Risk Mapping, Assessment, and Planning 

RRCC Regional Response Coordination Center 

RSF Recovery Support Function 

SFHA Special Flood Hazard Area 

SFMO State Floodplain Management Office 

SMAA Statewide Mutual Aid Agreement 

SWAN Simulating Waves Nearshore 

TAC Technical Advisory Committees 

TAS Testing Application Standards 

USGS U.S. Geological Survey 

WBDR windborne debris region
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-1

1Introduction

Hurricane Irma was one of the strongest hurricanes ever 

observed in the open Atlantic Ocean and caused 92 fatalities 

in five States (NOAA NHC, 2018). 

On September 10, 2017, Hurricane Irma made landfall on the East Coast of the United States. As 

part of the response to the disaster, the Federal Insurance and Mitigation Administration (FIMA) 

of the U.S. Department of Homeland Security’s (DHS’s) Federal Emergency Management Agency 

(FEMA) deployed a Mitigation Assessment Team (MAT) composed of national and regional 

building science and other types of experts to assess the damage in Florida. 

Twelve days after Hurricane Irma struck the Florida coast (September 22–25, 2017), the MAT 

performed a preliminary field assessment of building damage in limited areas in Collier, Lee, 

Miami-Dade, and Monroe Counties. This pre-MAT was a small team sent in advance tasked to 

quickly observe and record select perishable damage data; locate damaged areas requiring further 

assessment; and determine overall impact of the hurricane, scope of buildings and areas to be 

visited, and skillsets that would be needed for a larger, follow-on MAT. The MAT was then deployed 

from December 10 to 16, 2017 to Collier, Lee, Miami-Dade, and Monroe Counties. Investigative field 

work to evaluate erosion impacts in St. Johns County was conducted on February 14 and 15, 2018. Its 

mission was to assess the performance of buildings affected by Hurricane Irma and their associated 

utility systems.
1-2 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

INTRODUCTION

The primary purpose of a MAT is to improve the natural hazard resistance of buildings by evaluating 

the key causes of building damage, failure, and success, and developing strategic recommendations 

for improving short-term recovery and long-term disaster resilience to future natural hazard 

events. The MAT report provides information that will help communities, businesses, design 

professionals, and other interested stakeholders to rebuild and design more robust and resilient 

buildings, structures, and their associated utility systems, thereby minimizing loss of life and 

injuries, and reducing property damage resulting from future natural hazard events. This report 

describes the MAT’s observations during field assessments in Florida and presents conclusions and 

recommendations based on those observations. 

This MAT report focuses on several construction and floodplain management issues observed after 

Hurricane Irma that were not observed in former MAT damage assessments or that were addressed 

in lesser detail in those MAT reports. These issues include, but are not limited to:

+ The lack of planning and operations associated with deploying active dry floodproofing 

systems

+ The effect of preferential scour pathways

+ Damage to structures due to improperly secured fastening of breakaway walls

+ Damage to asphalt shingles, vinyl soffits, and vinyl siding from wind and wind-borne debris

1.1 Organization of the Report

This MAT report is divided into five chapters and three appendices. This chapter describes 

Hurricane Irma, regional preparedness activities and the MAT background and process. Chapter 2 

discusses building codes, standards, and regulations in effect in Florida. Chapter 3 describes MAT 

observations related to the performance of residential and non-residential buildings under flood 

conditions. Chapter 4 describes MAT observations related to damage sustained by residential and 

non-residential buildings from high winds and evaluates the effect building codes have had on 

building performance for those buildings exposed to high winds. Chapter 5 presents the MAT’s 

conclusions and recommendations and is intended to help guide reconstruction for flood- and 

hurricane-prone communities. In addition, the report includes the following appendices:

+ Appendix A: Acknowledgements

+ Appendix B: Glossary

+ Appendix C: Links to Recovery Advisories for Hurricane Irma in Florida

+ Recovery Advisory 1 (2018d), Dry Floodproofing: Operational Considerations

+ Recovery Advisory 2 (2018h), Soffit Installation in Florida

+ Recovery Advisory 3 (2018f), Mitigation Triggers for Roof Repair and Replacement in the 6th 

Edition (2017) of the Florida Building Code
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-3

INTRODUCTION

1.2 Hurricane Irma: The Event

Irma began as a weak wave of low pressure accompanied by disorganized showers and thunderstorms 

that emerged off the West African coast on August 27. Tropical Storm Irma formed in the far eastern 

Atlantic Ocean, just west of the Cape Verde Islands, on the morning of August 30. Over the next 30 

hours, the storm intensified into a major hurricane with highest sustained winds of 115 miles per 

hour (mph), a Category 3 storm on the Saffir-Simpson Hurricane Wind Scale. The storm became a 

Category 5 hurricane on September 5, with maximum sustained winds of 185 mph, and was located 

north of the islands of Puerto Rico and Hispaniola. This made Hurricane Irma one of the strongest 

observed hurricanes in the open Atlantic Ocean. Table 1-1 shows a comparison of Hurricane Irma’s 

wind speeds with other major Atlantic hurricanes. 

THE SIGNIFICANCE OF HURRICANE IRMA

• Hurricane Irma became a Category 5 • As a measure of the storm’s intensity, the

hurricane on September 5, 2017. Hurricane Accumulated Cyclone Energy (ACE) index

Irma’s 185 mph winds were the strongest of 67.5 generated by Irma was the second

1-minute maximum sustained winds recorded highest in the satellite era (since 1966) for an

for an Atlantic hurricane outside of the Gulf of Atlantic hurricane, trailing only Hurricane Ivan

Mexico and the Caribbean. (2004), which had an ACE index of 70.4.

• Hurricane Irma maintained an intensity of 185 •	 As Hurricane Irma hit Florida, tropical storm

mph for 37 hours—the longest any cyclone force winds extended outward up to 400

on record has maintained that intensity— miles from the center.

breaking the old record of 24 hours set by • Approximately 6.5 million residents in Florida Typhoon Haiyan in 2013. were evacuated from coastal areas.

SOURCES: NOAA NWS, 2017; KLOTZBACH AND BELL, 2017

Table 1-1: Comparison of Hurricane Irma Wind Speed to Other Major Atlantic Hurricanes

Year Hurricane Maximum Sustained Winds (mph)

1992 Andrew 173

2004 Ivan 167

2005 Katrina 173

2005 Wilma 184

2017 Irma 185

SOURCES: NOAA, N.D.; NOAA NHC, 2004; NOAA NHC, 2005; NOAA NHC, 2006; NOAA NCEI, 2018b

The storm weakened to a Category 4 on September 8 and then re-intensified while crossing the 

open waters of the Straits of Florida. On September 10 at 9:10 a.m. EDT, Hurricane Irma made 

landfall on Cudjoe Key, FL, as a Category 4 storm with maximum sustained winds near 130 mph 

and a minimum pressure of 931 millibars (mb) (NOAA NHC, 2018). Later that day, Hurricane Irma 

made a second landfall near Marco Island as a Category 3 hurricane with maximum sustained winds 

of 115 mph and a central pressure of 940 mb before tracking up the Floridian Peninsula (Figure 

1-1) and into Georgia on September 11 (NOAA NWS, 2017). Sustained hurricane force wind (i.e., 

74 mph or greater) extended well inland over the southern Florida peninsula. The Marco Island 

Police Department reported a wind gust of 130 mph, and a wind gust of 142 mph was reported at 

the Naples Municipal Airport (NOAA NWS, 2017; NOAA NHC, 2018).
1-4 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

INTRODUCTION

Figure 1-1: Composite satellite image from the GOES-13 weather satellite of landfall near the Florida Keys (left) on 

September 10, 2017 8:15 AM

SOURCE: NASA, 2017

As Hurricane Irma hit Florida, tropical storm force winds extended up to 400 miles from the center, 

and hurricane force winds extended outward 80 miles. Figure 1-2 shows the cone of the probable 

track that was forecast on Thursday, September 7, enveloping the entire State of Florida, and the 

most likely arrival time of tropical storm force winds on Sunday, September 10. In addition to the 

long periods of heavy rain and strong winds, storm surge flooding also pummeled the coasts well 

away from the storm center. In the Jacksonville area, strong and persistent onshore winds blew for 

days before Irma’s center made its closest approach.

The National Oceanic and Atmospheric Administration (NOAA) measures the power of hurricanes 

using the estimated maximum sustained surface wind velocity for each 6-hour period of their 

existence. This measurement, the ACE, was 67.5 for Hurricane Irma, which is the second most 

powerful storm in the satellite era (since 1966) (Klotzbach and Bell, 2017). Irma’s power was the 

result of the duration of sustained hurricane force winds as the storm approached the U.S. coast. 

As it approached southern Florida, the storm weakened to a Category 3 hurricane. For a detailed 

discussion of the timeline and formation history of Hurricane Irma, see the NOAA National 

Hurricane Center’s (NHC’s) Hurricane Irma Tropical Cyclone Report (NOAA NHC, 2018).
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-5

INTRODUCTION

Figure 1-2: 

Hurricane Irma cone 

of probable track 

forecast on Thursday, 

September 7 (upper) 

and most likely arrival of 

tropical storm force winds 

on Sunday, September 10 

(lower)

SOURCE: NOAA NHC, 2017A AND 

2017B
1-6 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

INTRODUCTION

1.2.1 Storm Surge Flooding

Hurricane Irma was the first major (Category 3 or higher) hurricane to make landfall in South 

Florida since Hurricane Wilma of 2005, bringing with it high winds and predicted storm surge 

inundation. Figure 1-3 to Figure 1-6 show the locations of high water marks surveyed by the U.S. 

Geological Survey (USGS) after the event. Significant flooding occurred where the combination 

of storm surge and riverine flooding from rainfall-runoff overflowed streams and riverbanks and 

related infrastructure in the City of Jacksonville (Note: the MAT did not visit this area). This 

phenomenon probably occurred in locations where rivers flow into tidal areas that experienced 

storm surge, although the timing of the runoff and storm surge peaks seldom coincide (NOAA 

NHC, 2018). 

To characterize the storm surge flooding from Hurricane Irma, two datasets from FEMA’s Flood 

Map Service Center1 were queried and compared: tide gage data at locations in South Florida and 

the 10-, 2-, 1-, and 0.1-percent-annual-chance stillwater elevations from the counties’ Flood Insurance 

Studies (FISs). The results of this comparison are reported in Table 1-2.

The FISs for Lee, Collier, Miami-Dade, and Monroe County are currently in the process of being 

updated. The revised Flood Insurance Rate Maps (FIRMs) are estimated to be completed in 2019–

2021. Thus, the effective FISs (circa 2009–2012) were used to determine the annual percent chance 

stillwater elevations. Although the effective studies are dated 2009–2012, the storm surge elevations 

are based on studies from the 1970–1980 timeframe. As reported at these five gages, Hurricane 

Irma was below the 1-percent-annual-chance event (or 100-year flood).

1-PERCENT-ANNUAL-CHANCE EVENT

FEMA FIRMs delineate flood hazard areas and 

zone designations (e.g., Zone VE, Zone AE) that 

reflect the nature of the flood conditions expected 

during the base flood. The base flood is the flood 

that has a 1 percent annual chance of occurrence 

(frequently referred to as the 100-year flood). 

FIRMs show the base flood elevation, or BFE. 

The area designated as subject to inundation 

from the 1-percent-annual-chance flood is called 

the Special Flood Hazard Area (SFHA).

Locations within the SFHA can be exposed to 

flooding at a greater frequency (i.e., more often) 

than the 1-percent-annual chance event. The 

water surface elevation at these locations may 

be less than the BFE, but may still cause minor 

damage. Subsurface areas and infrastructure at 

ground level are subject to flooding at a water 

surface elevation below the BFE.

1 The FEMA Flood Map Service Center can be accessed here: msc.fema.gov/portal/home.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-7

INTRODUCTION

Figure 1-3: Surveyed locations of Hurricane Irma’s high water marks

SOURCE: HIGH WATER MARK DATA IS FROM USGS, 2017
1-8 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

INTRODUCTION

Figure 1-4: Surveyed locations of Hurricane Irma’s high water marks in Lee and Collier Counties

SOURCE: HIGH WATER MARK DATA IS FROM USGS, 2017
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-9

INTRODUCTION

Figure 1-5: Surveyed locations of Hurricane Irma’s high water marks in Miami-Dade County

SOURCE: HIGH WATER MARK DATA IS FROM USGS, 2017

The combined effect of storm surge and tide produced maximum inundation levels between 5 and 

8 feet above ground level for small portions of the Lower Florida Keys from Cudjoe Key eastward to 

Big Pine Key and Bahia Honda Key. Several high water marks of at least 4 feet above ground level 

were also surveyed by USGS in this area, with the highest mark being 5.45 feet above ground level 

on Little Torch Key (NOAA NHC, 2018). 

In Collier County at Chokoloskee, inundation levels were as high as 6 to 8 feet near the waterfront. 

Inland areas of the island had inundation levels of 3 to 5 feet. At the Everglades National Park Gulf 

Visitor Center in Everglades City, the USGS measured a high water mark greater than 5 feet above 

ground. Flooding in other areas in Everglades City ranged from 2 feet to a maximum of 6 feet of 

inundation. Marco Island had up to 3 feet of inundation above ground (NOAA NWS, 2017). Strong 

offshore winds initially blew away from the coast causing water to recede along the southwestern 

coast of Florida. As the center of the storm moved past this area, the winds shifted onshore, and the 

water level at the NOAA tide gage at Naples increased by 6 feet within the first hour and 9 feet in 3 

hours (NOAA NHC, 2018).
1-10 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

INTRODUCTION

Figure 1-6: Surveyed locations of Hurricane Irma’s high water marks in Monroe County

SOURCE: HIGH WATER MARK DATA IS FROM USGS, 2017

In Miami-Dade County along the shoreline of Biscayne Bay, the USGS measured 4 to 6 feet of 

inundation, with the highest estimated depth of more than 5 feet in Matheson Hammock Park. 

Downtown Miami was flooded, likely due to the combination of rainfall and runoff, wave overwash, 

and backflow through the city’s drainage system (NOAA NHC, 2018). Inundation depths were 

shallower in the communities north of downtown Miami. In Broward County, the highest inundation 

was 2 to 3 feet from Ft. Lauderdale Beach southward. In Palm Beach County, inundation was not 

significant (NOAA NWS, 2017).

The combined effect of storm surge and the tide produced maximum inundation levels of 1 to 2 

feet above ground level along the west coast of Florida north of Charlotte Harbor to Apalachee Bay. 

Similar to what occurred near Naples, offshore winds on the northern side of Irma’s circulation 

initially caused water levels to recede below normal levels along much of the west coast of Florida, 

including Tampa Bay. In Tampa Bay at St. Petersburg, the water level was 5 feet below normal 

(NOAA NWS, 2017).
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-11

INTRODUCTION

Table 1-2: Water Surface Elevations and Estimated Return Periods in South Florida Counties

County NOAA ID

NOAA Station 

Name

Maximum 

Water Surface 

Elevation (feet 

NAVD88) 

Estimated 

Return 

Period(a)

Annual-Chance Stillwater Elevation

(feet NAVD88)

10%

(10-Year)

2%

(50-Year)

1%

(100-Year)

0.2%

(500-Year)

Lee 8725520 

Fort Myers, 

Caloosahatchee 

River, FL

3.33 10 year 3.3(b) N/A(b) 7.0(b) 8.1(b)

Collier 8725110 Naples, Gulf of 

Mexico, FL 4.60 <20 year 3.9(c) 7.3(c) 8.4(c) 10.4(c)

MiamiDade 8723214 

Virginia Key, 

Biscayne Bay, 

FL

3.84 <10 year 4.3(d) 5.6(d) 6.2(d) 7.2(d)

Monroe 8723970 Vaca Key, 

Florida Bay, FL 2.14 <10 year 3.2(e) 5.4(e) 6.3(e) 7.6(e)

Monroe 8724580 Key West, FL 2.64 <20 year 1.9(e) 4.2(e) 5.5(e) 6.0(e)

NAVD88 = North American Vertical Datum of 1988; NGVD29 = National Geodetic Vertical Datum of 1929; NOAA = National Oceanic and 

Atmospheric Administration 

(a) Prior to Hurricane Irma, FEMA initiated a coastal flood risk study for the South Florida Study Area (Broward, Miami-Dade, Monroe, and 

Palm Beach Counties) and the Southwest Florida Study Area (Charlotte, Collier, Desoto, Hendry, Lee, and Sarasota Counties). Hurricane Irma impacted the coast in the middle of the coastal flood mapping update process. 

(b) The Lee County FIS is preliminary (dated February 2018). The stillwater values do not include wave setup.

(c) The effective Collier County FIS (dated May 2012) is in the process of being updated by the Southwest Florida Study. The return period 

results herein are only to provide a comparison and will be superseded once the new study is released (2019–2021). The stillwater 

values do not include wave setup.

(d) The effective Miami-Dade County FIS (dated September 2009) is in the process of being updated by the South Florida Study. The results herein are only to provide a comparison and will be superseded once the new study is released (2019–2021). The stillwater values 

do not include wave setup. The stillwater values were converted from NGVD29 to NAVD88.

(e) The effective Monroe County FIS (dated February 2005) is in the process of being updated by the South Florida Study. The results 

herein are only to provide a comparison and will be superseded once the new study is released (2019–2021). The stillwater values do 

not include wave setup. The stillwater values were converted from NGVD29 to NAVD88.

1.2.2 Rainfall

Rainfall totals of 10 to 15 inches were common for Hurricane Irma across the peninsula and the 

Florida Keys. The maximum reported total rainfall for the storm was near the Fort Pierce Water 

Plant in St. Lucie County, where 21.66 inches of rain was measured between September 9 and 12. 

Most rivers in northern Florida were flooded, and major or record flood stages were reported at 

rivers in Alachua, Bradford, Clay, Duval, Flagler, Marion, Nassau, Putnam, and St. Johns Counties 

(Note: the MAT did not visit riverine areas in these counties). The St. Johns River set record flood 

stages at many locations in Duval County, causing major flooding in the Jacksonville metropolitan 

area (NOAA NHC, 2018). Figure 1-7 shows the total estimated rainfall from Hurricane Irma for the 

southeastern United States.
1-12 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

INTRODUCTION

Figure 1-7: 

Map of rainfall totals 

associated with Hurricane 

Irma (or its remnants)

SOURCE: NOAA NCEP, 2017

1.2.3 Wind

On September 10 at 9:10 a.m. EDT, Hurricane Irma made landfall on Cudjoe Key, FL, as a 

Category 4 storm with maximum sustained winds near 130 mph. Later that day as Hurricane Irma 

approached the mainland, sustained Category 3 winds of 111 to 115 mph were confined to a small 

area of the eye that touched Marco Island, FL, and a small part of the immediate coastline of Collier 

County. Sustained Category 2 winds (96 to 110 mph) occurred in portions of the Naples area. 

The highest wind gust recorded on land in South Florida was 142 mph at a monitoring site at the 

Naples Municipal Airport (ID: NPLMP). The maximum sustained wind speed on Marco Island was 

recorded at 112 mph (NOAA NWS, 2017).

Many locations in Broward and Miami-Dade Counties reported sustained winds below hurricane 

force (between 50 and 73 mph). Isolated locations (immediate coastal areas of Broward and 

Miami-Dade Counties within 1 mile of the coast and southern Miami-Dade) may have experienced 

sustained winds that reached the low end of Category 1 hurricane strength (around 75 mph). Wind 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-13

INTRODUCTION

gusts in Broward, Miami-Dade, and 

Palm Beach Counties likely peaked in 

the 80 to 100 mph range (see Figure 

1-8). For comparison, the American

Society of Civil Engineers (ASCE)

standard ASCE 7, Minimum Design

Loads for Buildings and Other Structures,

basic wind speeds2 for Risk Category

II building design are shown on the

right (ASCE 7-10).

ASCE 7 RISK CATEGORIES

The ASCE classifies buildings as Risk Category I, II, III, 

or IV depending on the risk posed to human life if the 

structure were to fail. Almost all residential buildings fall 

into Category II. Category II includes buildings that do 

not fall into Category I (those that pose a low risk to 

human life in the event of failure), Category III (those that 

pose substantial risk to human life in the event of failure), 

or Category IV (those designated as essential facilities, 

which pose substantial hazard to the community in the 

event of failure).

Figure 1-8: Comparison of gusts experienced during Hurricane Irma (left) with ASCE 7-10 design 3-second wind gusts 

(right)

SOURCES: LEFT MAP MODIFIED FROM ARA/FEMA GEOSPATIAL WORKING GROUP, 2017. RIGHT MAP MODIFIED FROM ASCE, 2010

2 Basic wind speed is defined as the 3-second gust speed at 33 feet (10 meters) above the ground in Exposure Category C. 
1-14 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

INTRODUCTION

1.2.4 Tornadoes

Hurricane Irma produced 25 confirmed tornadoes, 21 of which occurred in Florida. There were 

three EF-2 (on the Enhanced Fujita Scale3), 15 EF-1, and 7 EF-0 tornadoes (NOAA NHC, 2018). 

The majority of the tornadoes developed along the east coast of central and northern Florida. The 

tornado in Miami-Dade County struck near Homestead Motor Speedway. In Broward County, two 

of the tornadoes were EF-1 and the other was EF-0. One of the EF-1 tornadoes occurred 4 miles 

west of Miramar along 172nd Avenue between Memorial Hospital and Miramar Regional Park, 

where sections of trees were ripped apart. The other EF-1 tornado formed 4 miles west-northwest 

of Miramar in the Chapel Trail Neighborhood near NW 196th Avenue, north of Pines Boulevard. 

Several trees were ripped apart in a localized area, with some damage to roof tiles and screenedin patios. The damage pattern suggested rotation from a tornado vortex. The EF-0 tornado briefly 

touched down near Oakland Park (NOAA NWS, 2017).

1.3 Hurricane Irma: The Impact

The Tropical Cyclone Report for Hurricane Irma published by NOAA’s NHC on May 30, 2018, 

indicates that Hurricane Irma was directly responsible for 47 fatalities across the Caribbean Islands 

and the southeastern United States as a result of strong winds, heavy rains, and high surf. In the 

United States, 10 direct fatalities were reported and an additional 82 indirect fatalities occurred, 77 

of which were in Florida. These include the fatalities of elderly residents in a nursing home when the 

facility lost power to its central air conditioning, causing the facility to become overheated. Hundreds 

more were injured as a result of the storm (NOAA NHC, 2018). Approximately 6.5 million residents 

in Florida were evacuated from coastal areas (Florida House of Representatives, 2018).

NOAA’s National Center for Environmental Information (NCEI) estimates that wind and water 

damage caused by Irma in the United States totaled approximately $50.5 billion (NOAA NCEI, 

2018a). This estimate is based on a variety of public and private data sources, including FEMA, 

the Insurance Services Office, the U.S. Department of Agriculture, the Energy Information 

Administration, the U.S. Army Corps of Engineers, and State and other agencies. The data sources 

provide key pieces of information that capture the total, direct costs (both insured and uninsured) 

of weather and climate events. The estimated costs were adjusted for inflation and reported in 

dollars in terms of damages avoided had the event not taken place. The damage costs incorporate 

estimates based on physical damage to residential, commercial, and government or municipal 

buildings; material assets within a building; time element losses such as business interruption; 

vehicles and boats; offshore energy platforms; public infrastructure such as roads, bridges, and 

buildings; and agricultural assets such as crops, livestock, and timber. Insured loss data were scaled 

up to account for uninsured and underinsured losses. This is specific by peril, geography, and asset 

class. In addition, the estimated damage costs do not include losses related to health care, injury 

and loss of life, and natural capital.

In the Florida Keys, more than 1,300 boats were damaged or destroyed (NOAA NHC, 2018). Other 

long-term damage impacts include the loss of housing in the Florida Keys, damage to wastewater and 

potable water infrastructure, and minor to major erosion at different locations along the coastline. 

In addition, the estimate of Hurricane Irma’s impact on Florida’s agriculture industry is $2.5 billion 

3 For more information about the Enhanced Fujita scale, refer to www.spc.noaa.gov/faq/tornado/ef-scale.html.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-15

INTRODUCTION

in total losses (Florida House of Representatives, 2018). The insurance industry estimated $8.6 

billion in insured losses (Florida Office of Insurance Regulation, 2018).

For a detailed discussion on the assessment of the storm’s impact on beach and dune erosion and 

structural damage to coastal regions of Florida, refer to the Florida Department of Environmental 

Protection’s report titled, Hurricane Irma Post-Storm Beach Conditions and Coastal Impact in Florida 

Report (Florida DEP, 2018).

1.4 Regional Preparedness Actions

On September 4, Florida Governor Rick Scott declared a state of emergency for Florida and placed 

100 members of the Florida National Guard on duty to assist in preparations. According to a report 

prepared for the Florida House of Representatives (2018), all 7,000 National Guard troops were 

ordered to be on duty by September 8. State and local emergency management officials advised 

residents to stock their hurricane kits. Governor Scott suspended tolls on all toll roads in the State 

starting at 5:00 p.m. on September 5. All State offices in Florida were closed on September 8. 

Schools and colleges were closed in 44 of the State’s 67 counties before Governor Scott ordered all 

State colleges, universities, schools, and offices to be closed from September 8 to 11.

Fifty-four of Florida’s 67 counties issued both voluntary and mandatory evacuation orders to a 

record 6.8 million people. Nearly 700 shelters were opened throughout the State, housing a record 

190,000 people. A record 6.5 million people evacuated, all while the State Emergency Operations 

Center and local emergency management officials adjusted to 10 different scenarios over the course 

of Irma’s track (Florida House of Representatives, 2018).

1.5 FEMA Mitigation Assessment Team

FEMA conducts building performance studies after unique or nationally significant disasters 

to better understand how natural and manmade events affect the built environment. A MAT is 

deployed when FEMA believes the findings and recommendations derived from field observations 

will result in design and construction guidance that will improve the disaster resistance of the built 

environment in the affected State or region and will be of national significance to other disasterprone regions. FEMA bases its decision to deploy a MAT on preliminary information, such as: 

+ Magnitude of event

+ Type and severity of damage in the affected areas 

+ Pre-storm site conditions in the impacted areas, such as the presence of older housing, newer 

housing, non-residential and critical facility stock, and building utility infrastructure 

+ Potential value of study results to the recovery effort

+ Strategic lessons that can be learned and applied, potentially on a national level, related to 

improving building codes, standards, industry practices or guidance, code enforcement, 

research needs, knowledge gaps, or others 

+ Possibility of the field assessment gathering and analyzing pertinent information regarding 

the effectiveness of (1) certain FEMA grants and (2) key engineering principles and practices 

that FEMA promotes in published guidance and best practice documents
1-16 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

INTRODUCTION

+ Value of providing FEMA guidance in discipline topics currently not addressed or updating 

existing FEMA guidance on select topics as needed

The MAT studies the adequacy of current building codes and floodplain management regulations, 

local practices, and building materials in light of the damage observed after a disaster. Lessons 

learned from the MAT’s observations are communicated through recovery advisories, fact sheets, 

and a comprehensive MAT report, all of which are made available to communities and the general 

public to aid their rebuilding efforts and enhance the disaster resistance of building improvements 

and new construction.

1.5.1 Hurricane Irma MAT

Twelve days after Hurricane Irma struck the Florida coast (September 22–25, 2017), the pre-MAT 

performed a preliminary field assessment of building damage in limited areas in Collier, Lee, MiamiDade, and Monroe Counties. The full Irma MAT was deployed on December 10, 2017, to the areas 

initially surveilled by the pre-MAT and completed its field assessment work in February 2018. The 

MAT’s mission was to assess the performance of residential and non-residential buildings affected 

by Hurricane Irma in Florida. To assess the effectiveness of flood and wind mitigation efforts 

previously undertaken, the MAT evaluated buildings that had previously undergone mitigation to 

improve their resistance to hurricane conditions (either wind or flood), as well as residential and 

non-residential buildings that had not been mitigated. The MAT focused on buildings located in 

the area of Hurricane Irma’s landfall in Collier, Lee, Miami-Dade, and Monroe Counties.

1.5.2 Team Composition

The Irma MAT was composed of 17 subject matter experts, including:

+ FEMA Headquarters and Regional office staff

+ A representative from the State of Florida Division of Emergency Management (FDEM) 

Floodplain Management Office

+ Building code, construction, and manufacturing industry staff from the Asphalt Roofing 

Manufacturers Association and PGT Industries

+ Design professionals and technical consultants 

Team members have backgrounds in structural, civil, and coastal engineering; floodplain 

management and mapping; building codes; critical facility protection; flood and wind damageresistant materials; and urban floodproofing. The members of the MAT are listed in the front 

matter of this report. 

1.5.3 Methodology

The Hurricane Irma MAT was divided into two specialty units: Flood and Wind. The Flood Unit 

focused on flood damage related to inundation, scour, and wave forces, as well as the performance 

of dry floodproofing and facility planning. The Wind Unit focused on wind-related damage and 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-17

INTRODUCTION

roof and soffit performance. Each unit visited several locations in Florida to assess the performance 

of different building and facility types.

Involvement of State and Local Agencies

FEMA encouraged State, county, and local government officials and locally based experts to 

participate in the assessment process. Their involvement was critical and helped improve the MAT’s 

understanding of local construction and enforcement practices; encouraged the MAT to develop 

recommendations that were both economically and technically feasible for the communities 

involved; facilitated communications among Federal, State, and local governments and the private 

sector; and improved the State and local understanding of the MAT’s observations, conclusions, and 

recommendations, which should enable them to bring about changes in their communities.

The MAT members met with local emergency management and government officials in many of the 

areas they visited. The officials gave an overview of the damage in their area and helped identify key 

sites to visit. The MAT also coordinated with the FEMA Joint Field Offices (JFOs) that had been set 

up in the area shortly after Hurricane Irma. Individuals who assisted the MAT in its field operations 

and report development are listed in Appendix A.

Pre-MAT Deployment and Site Selection

The pre-MAT was deployed shortly after Hurricane Irma’s landfall and was tasked to quickly observe 

and record select perishable damage data, locate damaged areas requiring further assessment, 

and help determine the size and scope of areas and buildings to be visited, as well as the skillsets 

that would be needed for a larger follow-on MAT. The pre-MAT conducted ground surveillance 

in the areas shown in Figure 1-9. The members of the pre-MAT developed a list of select locations 

and specific building sites they considered important for the MAT to observe to better understand 

performance, vulnerabilities, and gaps or strengths in building planning, design, construction, 

enforcement, or other practices. 

FEMA, State and local government agencies, and the MAT members also identified additional 

potential sites for the MAT to visit. To produce the final site list, the MAT assessed whether data 

were sufficient to evaluate building damage at each site. Specifically, the availability of the following 

data sources was considered for each site:

+ Wind field maps, wind contour maps, and grids showing flood depths and extents produced 

by the FEMA Natural Hazard Risk Assessment Program (NHRAP)

+ Water surface elevation data compiled from USGS, recorded high water marks, and surge 

sensor data

+ Data on FEMA Hazard Mitigation Assistance grant projects

+ Claims from the FEMA National Flood Insurance Program (NFIP) 

+ Data from the effective FEMA National Flood Hazard Layer and preliminary/ongoing FEMA 

Risk Mapping, Assessment, and Planning (Risk MAP) coastal studies in South Florida

+ Damage information received from the FEMA Regional Response Coordination Center 

(RRCC) and JFO through Federal, State, and local governments and academic and private 

sector sources from which buildings of interest were selected

+ Orthophotographs and data from NOAA and the Civil Air Patrol
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Figure 1-9: Field locations visited by the pre-MAT

ADCIRC model, the CERA web mapping application provides an easy-to-use interactive web interface, which is accessible here: 

+ Data from the Fulcrum Community Data National Science Foundation (NSF) Rapid 

Response Research for the 2017 hurricanes4

+ Estimates of storm surge and wave heights from the Coastal Emergency Risks Assessment’s 

(CERA’s) Advanced Circulation (ADCIRC) Storm Surge and Simulating Waves Nearshore 

(SWAN) models webcast5

+ Press/social media stories and photographs of post-disaster damage

4 Fulcrum Community is a crowdsourced data collection solution for qualified humanitarian projects. For the 2017 disaster season, the NSF 

funded teams from universities across the United States and coordinated a response with the objective of collecting perishable data on the 

performance of U.S. civil infrastructure. The data collected are accessible here: web.fulcrumapp.com/communities/nsf-rapid. 

5 The CERA group delivers storm surge and wave predictions for impending or active tropical cyclones in the United States. Based on the 

nc-cera.renci.org. 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 1-19

INTRODUCTION

Based on the results of the pre-MAT, buildings were selected as examples of wind or flood effects 

for the full MAT damage assessment. The buildings selected for damage assessment included 

residential, non-residential, and mixed-use low-rise buildings; mid- and high-rise buildings; critical 

facilities and key assets; and public facilities, specifically public restrooms. Buildings were located 

in both coastal and riverine floodplains, as well as in urban areas, as described in the section that 

follows.

Field Deployment

Two MAT units were deployed on December 10, 2017, for 1 week. The 3-month delay in deployment 

after the storm resulted in the loss of perishable damage data (some sites and buildings were 

demolished; many buildings, roofs, windows and doors, and wall or other systems were already 

repaired or being repaired; and debris fields were cleaned up by the time the MAT arrived). When 

speaking with individuals about specific buildings, some were hesitant to discuss damage repairs 

affecting insurance claims. 

To assess the performance of specific building and facility types, the MAT Flood and Wind units 

visited different locations depending on the type of damage—wind or flood—that occurred during 

Hurricane Irma. Both units conducted site visits and recorded observations along the coast of 

Florida at the locations shown in Figure 1-10. 

The locations were based on those previously visited by the pre-MAT and on FEMA, State, and 

local input. For specific locations, outreach was conducted before and during the MAT deployment 

via telephone and email with site visit representatives to coordinate access. Some attempts were 

successful, while others were not. If a site of interest was identified in a conversation with the local 

contact, the contact was included as part of the field reconnaissance team. 

When possible, building or facility owners were interviewed to gain insight into how well their 

buildings and facilities withstood Hurricane Irma and how their recovery efforts were progressing. 

The MAT spent considerable time assessing partially damaged buildings to determine why certain 

buildings performed better than others. The MAT members documented any observed best 

practices.
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Figure 1-10: Field locations visited by the MAT Wind and Flood Units after Hurricane Irma. The inset map shows the 

locations of field visits in St. Johns County to evaluate erosion impacts.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 2-1

2Building Codes, Standards, 

and Regulations

Building codes that include requirements to address flooding and 

high winds can help buildings resist damage.

This chapter presents an overview of Florida’s building codes, the wind and flood provisions in those 

codes, and floodplain management in Florida. Section 2.1 describes the Florida Building Code 

(FBC), the process used by the Florida Building Commission to adopt and modify the International 

Codes® (I-Codes®), the model codes on which the FBC is based, and how local jurisdictions can 

amend the FBC. 

Section 2.2 highlights recent initiatives of the Florida Division of Emergency Management (FDEM) 

to support communities that participate in the NFIP and summarizes the history of flood provisions 

in the FBC. Florida-specific amendments to the flood provisions of the I-Codes are described, 

including requirements specific to hospitals, nursing homes, and public education relocatable 

units. This section also lists the most common local amendments to the flood provisions in the 

FBC adopted by many Florida communities to incorporate higher and more restrictive standards. 

Section 2.3 summarizes the wind requirements in the FBC, including Florida-specific amendments 
2-2 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

BUILDING CODES, STANDARDS, AND REGULATIONS

for wind and water intrusion. Section 2.4 discusses Florida manufactured housing (MH) installation 

standards. 

FEMA, the State of Florida, and others have documented how buildings are better able to resist 

damage from high winds and flooding when designed and constructed in compliance with building 

codes that contain requirements to address those hazards. As with other post-disaster MAT reports, 

observations after Hurricane Irma reinforce the value of the wind and flood provisions of the FBC, 

and the importance of trained plan reviewers and inspectors. Observations also identify the critical 

importance of builders paying attention to details during construction. 

2.1 Building Codes in Florida

The FBC is part of the Florida Administrative Code adopted through Rulemaking as governed by 

Chapter 120 of the Florida Statutes. The adoption of the FBC by the Florida Building Commission 

as a Rule is mandated by the Florida Legislature (the code is not adopted statutorily). Local 

jurisdictions are required to enforce the FBC, but do not need to adopt it locally. 

When Hurricane Irma made landfall in the State of 

Florida, the 5th Edition (2014) FBC was in effect. The 6th 

Edition (2017) FBC was adopted on June 13, 2017 through 

Rulemaking with an effective date of December 31, 2017. 

The term “Florida Building Code” refers to all of the 

codes administered by the Florida Building Commission, 

which include:

+ Florida Building Code, Building (FBCB)

+ Florida Building Code, Residential (FBCR)

+ Florida Building Code, Existing Building (FBCEB)

+ Florida Building Code, Mechanical (FBCM)

+ Florida Building Code, Plumbing (FBCP)

+ Florida Building Code, Energy Conservation (FBCEC)

+ Florida Building Code, Accessibility (FBCA)

+ Florida Building Code, Fuel Gas (FBCFG)

+ Florida Building Code, Test Protocols (High-Velocity 

Hurricane Zone [HVHZ] Test Protocols)

The 5th Edition (2014) FBC is based on the 2012 Edition of the applicable I-Codes published by 

the International Code Council (ICC). The 6th Edition (2017) FBC is based on the applicable 

2015 I-Codes. The base codes are revised by Florida-specific amendments through Florida’s code 

development process to create the FBC.

SCOPE OF THE FLORIDA 

BUILDING CODE

For new construction, the FBCB 

applies to all buildings and structures except detached one- and 

two-family dwellings and townhouses not more than three 

stories above grade plane, which 

are within the scope of the FBCR. 

One- and two-family dwellings and 

townhouses outside the scope of 

the FBCR are required to comply with the FBCB. The FBCEB 

applies to the repair, alteration, 

change of occupancy, addition to, 

and relocation of buildings, including historic structures.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 2-3

BUILDING CODES, STANDARDS, AND REGULATIONS

2.1.1 Florida Building Commission

The FBC is maintained and updated by the Florida Building Commission with administrative 

support and technical assistance from the Florida Department of Business and Professional 

Regulation (DBPR). The Commission is a 27-member stakeholder group that strives for consensus 

decisions on changes and updates to the FBC. Although the FBC is required to be updated every 

3 years, the Commission may revise the code annually to incorporate Declaratory Statements 

(interpretations), clarifications, and standard updates.

Code Development Process

The development processes for the 5th Edition (2014) and 6th Edition (2017) FBC were essentially 

the same. The first step was to select the base code that would serve as the starting point. The 

2015 I-Codes were selected as the base code for the 6th Edition (2017) FBC. For each update, all 

Florida-specific amendments expire except for the minimum requirements for State agencies 

(schools, nursing homes, swimming pools, etc.), statutory requirements, and the provisions of the 

HVHZ. The public is invited to propose code changes (Florida-specific amendments) to the base 

codes through the online Building Code Information System (BCIS) portal. Before the Florida 

Building Commission reviews the proposed code changes, they are first reviewed by Technical 

Advisory Committees (TACs). Eleven TACs review the proposed changes to the base code and make 

recommendations to the Florida Building Commission. 

Previously, for a proposed code change to be recommended for approval by a TAC, three-fourths of 

the TAC members in attendance were required to be in support of the change. The recommendations 

of the TAC were then forwarded to the Florida Building Commission; incorporating the code 

change in the next edition of the FBC required three-fourths of the Commission members present 

to support the proposal. Once the code development process was completed, the Rulemaking 

process began, and the updated FBC became effective at a predetermined date.

However, as a result of 2017 changes to Section 553.73 of the Florida Statutes, the process for 

developing the 7th Edition (2020) FBC will change rather significantly. The Commission must 

use the 6th Edition (2017) FBC as the base code or starting point. The first phase of the process 

requires the Commission and TACs to review the 2018 I-Codes to examine changes from the 2015 

I-Codes and determine whether to incorporate those changes into the 7th Edition (2020) FBC. The 

second phase will involve the TACs and Commission reviewing proposals submitted by the public to 

determine whether to incorporate those changes into the 7th Edition (2020) FBC. Additionally, the 

threshold for a TAC recommendation of approval of a code change has been reduced from threefourths of the TAC members present at the meeting to two-thirds. 

The 2017 statutory change also limits the Commission to only approving amendments to the code 

that are “needed to accommodate the specific needs of this state.” The statute further specifies that, 

at a minimum, the Commission must “adopt any updates to such codes or any other code necessary to 

maintain eligibility for federal funding and discounts from the National Flood Insurance Program, 

the Federal Emergency Management Agency, and the United States Department of Housing and 

Urban Development.” Any amendments or modifications made to the FBC will be carried forward 

until the next edition of the FBC.
2-4 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

BUILDING CODES, STANDARDS, AND REGULATIONS

The statute also prohibits any weakening of the wind resistance or prevention of water intrusion 

requirements in the FBC, including those contained in referenced standards, though this is not 

part of the 2017 changes.

2.1.2 Local Amendments

Local jurisdictions in Florida are permitted to amend the FBC provided such amendments do not 

weaken the code. Amendments must be submitted to the Florida Building Commission, which 

makes them available online. As part of the triennial code development process, the Commission 

reviews local amendments for consideration and inclusion in the FBC. However, the Commission 

does not have authority to approve or disapprove local amendments. 

Local amendments expire with the effective date of each new edition of the codes, which means 

communities must re-adopt local amendments every 3 years. There are several other limitations 

on local technical amendments, but they can be challenged. As a result, there are very few local 

technical amendments of the code except for those related to flood, which, by statute, do not expire 

(refer to Section 2.3.3). The most common technical amendments related to the wind provisions of 

the code clarify the specific location of the wind speed contours. 

2.2 Floodplain Management in Florida

Communities that participate in the NFIP agree to 

adopt and enforce floodplain management regulations 

that meet or exceed the minimum requirements of the 

NFIP (44 CFR Parts 59 and 60). The State Floodplain 

Management Office (SFMO) of the FDEM is designated 

by the Governor as the NFIP State Coordinating Agency. 

In this capacity, the SFMO serves as a liaison between 

Florida’s 467 NFIP communities and FEMA, helping 

communities implement sound land use development 

in floodplain areas to promote public health and 

safety, minimize loss of life, and reduce economic 

losses caused by flooding. Communities achieve those 

objectives by enforcing local floodplain management 

ordinances and the flood provisions of the FBC. 

Supported by FEMA Community Assistance Program 

State Support Services Element (CAP-SSSE) funding, 

the SFMO conducts Community Assistance Visits (CAV) 

and Community Assistance Contact (CAC) interviews, 

provides one-on-one assistance for ordinance 

development and amendments, offers general technical 

assistance to Florida communities, supports FEMA’s 

Map Modernization and Risk MAP processes, and 

provides training for local officials. The training is 

QUICK GUIDE FOR 

FLOODPLAIN MANAGEMENT

The SFMO produced an illustrated 

overview of floodplain management 

for non-technical local staff and refresher for floodplain administrators. 

The guide is useful for informing 

elected officials, appointed citizen 

boards, and the public. 

The Quick Guide is available online at www.floridadisaster.org/dem/

mitigation/floodplain/communityresources.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 2-5

BUILDING CODES, STANDARDS, AND REGULATIONS

conducted primarily through an agreement with the Florida Floodplain Managers Association 

(FFMA). 

The SFMO also supports communities that participate in the NFIP Community Rating System 

(CRS), a program that recognizes activities undertaken by communities to reduce flood risk by 

providing premium discounts to citizens who have NFIP flood insurance policies. As of April 2018, 

236 of the 467 Florida NFIP communities are in the CRS. Charged by FDEM leadership in early 

2015 to increase participation in the CRS, the SFMO worked with FEMA to develop an initiative 

to visit more than 200 communities. Depending on the results and resolution of any identified 

concerns, the reports produced for each community can be used by FEMA to qualify communities 

for the CRS. 

A central element of the initiative was development of “Seven Performance Measures” that, in 

effect, form a recommitment to the NFIP. The measures include conducting annual inspections 

of Special Flood Hazard Areas (SFHAs), having permit 

procedures and checklists in place, having procedures 

for making Substantial Improvement/Substantial 

Damage determinations, and communicating with utility 

companies and service providers regarding equipment 

and tank requirements. As of mid-2018, 26 of the visited 

communities have received FEMA approval for CRS 

entry. Other benefits of the initiative include increased 

awareness of the SFMO’s availability to provide technical 

support and acceleration of communities transitioning 

to floodplain management ordinances written explicitly 

to rely on the flood provisions of the FBC (refer to 

Section 2.2.4). 

In May 2018, the SFMO released the Florida PostDisaster Toolkit for Floodplain Administrators (see text box 

on the right). The toolkit describes six key actions, 

including planning ahead to communicate, assessing 

post-disaster needs, documenting high water marks, 

making Substantial Improvement/Substantial Damage 

determinations, understanding the NFIP claims and 

Increased Cost of Compliance coverage, and identifying 

post-disaster and mitigation funding assistance. 

To facilitate insurance company access to elevation 

certificates, in the 2016 legislative session, the Governor 

signed a bill amending Section 472.0366 of the Florida 

Statutes to require professionals authorized to prepare 

land surveys to submit elevation certificates to FDEM 

using the form developed by FEMA. Communities report 

that having access to elevation certificates for buildings 

is beneficial when owners elect to have certificates 

prepared as part of obtaining flood insurance policies. 

TOOLKIT FOR 

FLOODPLAIN MANAGERS

The toolkit is available online at www.

floridadisaster.org/dem/mitigation/

floodplain/community-resources.

ELEVATION CERTIFICATES

The web application for submitting elevation certificates and 

accessing submitted documents is 

available at www.floridadisaster.org/

elevation-certificates.
2-6 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

BUILDING CODES, STANDARDS, AND REGULATIONS

2.2.1 History of Flood Provisions in the Florida Building Code

The flood provisions in the FBC are based on the flood 

provisions in the I-Codes, which in turn are related to the 

floodplain management regulations of the NFIP. Since 

1998, FEMA has participated in the code development 

process for the I-Codes. Every 3 years, the family of 

I-Codes is modified through a formal, public consensus 

process. Starting with the 2010 FBC, the flood provisions 

in the I-Codes are retained as the Florida Building 

Commission undertakes the code development process 

every 3 years. 

FEMA deems the flood provisions in the 2018, 2015, 2012, 

and 2009 I-Codes to meet or exceed the minimum NFIP 

requirements for buildings and structures. Because the 

6th Edition (2017) FBC is based on the 2015 I-Codes 

and the Florida Building Commission has not weakened 

any flood provision below the NFIP minimums, the 

flood provisions of the 6th Edition (2017) FBC also meet 

or exceed the minimum NFIP requirements for buildings and structures. In conjunction with 

floodplain management ordinances, Florida communities rely on the FBC to fulfill the requirements 

for participation in the NFIP. FEMA makes the same statement about the flood provisions of the 2012 

and 2009 I-Codes, which formed the basis of the 2010 FBC and 5th Edition (2014) FBC, respectively.

In 2007 and 2008, with technical and funding support from FEMA Headquarters and FEMA 

Region IV, FDEM made a commitment to re-establish the NFIP State Coordinating Agency function 

and build capacity to become a premier State partner in floodplain management. In mid-2008, 

FDEM asked the Florida Building Commission to appoint a flood standards workgroup to develop 

recommendations for integrating the flood damage-resistant provisions in the I-Codes into the FBC. 

In mid-2009, the Commission adopted the workgroup recommendations. As a result, the 2010 FBC 

included those provisions, with some Florida-specific amendments. 

Many Florida communities, through local floodplain management regulations, have adopted and 

enforced provisions that exceed the NFIP minimum requirements for buildings. However, as dictated 

by Florida Statutes, only the FBC governs the design and construction of buildings. Thus, to address 

the potential for conflict and challenge to locally adopted higher standards, the SFMO developed 

a companion model ordinance written explicitly to rely on the FBC for design and construction of 

buildings in SFHAs. The ordinance, described in Section 2.2.4, includes administrative provisions 

and requirements for development other than buildings within the scope of the FBC. Together, the 

FBC and the model ordinance meet or exceed the NFIP requirements (Figure 2-1).

FLORIDA BUILDING CODE 

AND THE NFIP

The Florida SFMO compiles excerpts of the flood provisions of 

the 6th Edition FBC and a summary of the differences between 

the 6th Edition and the 5th Edition, 

online at www.floridadisaster.org/

dem/mitigation/floodplain.

FDEM refers users to FEMA’s 

Highlights of ASCE 24‐14 Flood 

Resistant Design and Construction 

(2015), online at www.fema.gov/

building-code-resources.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 2-7

BUILDING CODES, STANDARDS, AND REGULATIONS

Figure 2-1: 

FBC and local regulations 

meet or exceed the NFIP 

requirements

2.2.2 Flood Provisions in the Florida Building Code

International Building Code (IBC) Chapter 1, Administration, forms the basis for Chapter 1 of 

the FBC, which is used to administer all volumes in the FBC family of codes. For each triennial 

code development cycle, the Florida Building Commission makes numerous amendments to tailor 

Chapter 1 of the IBC according to statutory requirements and State-specific needs. The 5th Edition 

(2014) FBC, which was in effect when Hurricane Irma made landfall, and the 6th Edition (2017) 

FBC, effective December 31, 2017, contain the following Chapter 1 amendments specific to buildings 

and structures in flood hazard areas:

+ Section 102.7 adds a provision that relocated manufactured buildings (not manufactured 

housing) shall comply with flood hazard area requirements (e.g., if moved into or within flood 

hazard areas).

+ Sections 104.2.1 and 104.10.1 are not retained. Local floodplain management regulations 

incorporate equivalent provisions for Substantial Improvement and Substantial Damage 

determinations and requests for modification of flood provisions (refer to Section 2.2.4 of this 

report).

+ Sections 105.14 and 107.6.1 add provisions to restrict the building official’s authority to issue 

permits based on affidavits by stating it does not extend to flood load and flood resistance 

requirements. This limitation is necessary because of the NFIP requirement that communities 

review development for compliance.

+ Section 107.3.5 adds a section to specify examination of documents, including minimum plan 

review criteria for “Building” and “Residential.” These review criteria include flood hazard area 

requirements, lowest floor elevations, enclosures, and flood damage-resistant materials. Plan 

review criteria for mechanical, electrical, and plumbing (MEP) and fuel gas include design 

flood elevations (DFE).

+ Section 110.3 replaces the I-Code section for inspections. It requires two inspections specific to 

flood hazard areas: a foundation inspection and a final inspection. As part of the foundation 

inspection, elevation certification must be submitted upon placement of the lowest floor and 

prior to further vertical construction. As part of the final inspection, final certification of the 

lowest floor elevation must be submitted.
2-8 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

BUILDING CODES, STANDARDS, AND REGULATIONS

+ Section 111.2 adds a new requirement that certificates of occupancy for buildings in flood 

hazard areas must include a statement that documentation of the as-built lowest floor elevation 

has been provided and is retained in the community’s records.

+ Section 117 refers to local floodplain management ordinances for procedures when requests for 

variances to the flood provisions (Section 1612 or R322) are requested. This section does not 

apply to Section 3109, Coastal Construction Control Line.

Through the triennial code development process, the Florida Building Commission considers 

Florida-specific amendments, including several sections in Chapter 4 that outline requirements 

for specific occupancies. Provisions in those sections are considered “agency amendments” and are 

carried forward from edition to edition. Specific to flood hazard areas, agency amendments include:

+ Sections 449 and 450 require, for new construction and Substantial Improvements of hospitals 

and nursing homes, elevation or dry floodproofing to the higher of the base flood elevation 

(BFE) plus 2 feet or “the height of hurricane Category 3 (Saffir-Simpson scale) surge inundation 

elevation.” The sections also specify that for all additions, patient support areas, including food 

service, and patient support utilities for the additions shall be at or above the elevation of the 

existing building, unless otherwise required by Section 1612. 

+ Section 454 requires initial and subsequent installation of public education relocatable units to 

comply with floodplain standards, including setting the “finished floor” 12 inches above the BFE 

and anchoring the units to resist “buoyant forces.”

+ Section 1612.3 and Table R301.2(1) specify the establishment of flood hazard areas, which is 

accomplished by local floodplain management ordinances that adopt flood hazard maps and 

supporting data. 

+ Section 1612.4.1 modifies ASCE 24 Table 6-1 and Section 6.2.1 to permit dry floodproofing of 

non-residential buildings located in Coastal A Zones provided “wave loads and the potential for 

erosion and local scour are accounted for in the design.” The FBC references ASCE 24, Flood 

Resistant Design and Construction, for specific requirements for buildings and related components 

in flood hazard areas.

+ Section 3109 contains requirements applicable to most structures located seaward of the Coastal 

Construction Control Line, a line established by Florida Statute. In the 6th Edition (2017) FBC, 

this section is completely revised to bring the Coastal Construction Control Line requirements 

more in line with the Section 1612 requirements for Coastal High Hazard Areas (Zone V), while 

retaining certain requirements of statute and declaration statements (interpretations) issued by 

the Commission. At many locations around Florida’s coast, the “100-year storm elevation” used 

in the Coastal Construction Control Line requirements is higher than the BFE shown on FIRMs.

2.2.3 Local Amendments to the Flood Provisions of the FBC

A statutory provision was added in 2010 specifically for local amendments to the FBC flood 

provisions. Under three circumstances, these amendments do not expire every 3 years as other local 

amendments do (refer to Section 2.1.2): (1) if they are locally adopted before July 1, 2010; (2) if 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 2-9

BUILDING CODES, STANDARDS, AND REGULATIONS

the higher standard is freeboard; and (3) if the 

higher standard is adopted for the purpose of 

participating in the NFIP CRS.

As of mid-2018, 80 percent of Florida’s NFIP 

communities had adopted FBC-coordinated 

floodplain management regulations (refer to 

Section 2.2.4), with the remainder expected to 

do so by the end of 2019. The SFMO maintains 

a database of the most common locally adopted 

higher standards. The most common higher 

standards that affect the design and construction 

of buildings in flood hazard areas include: 

+ Additional elevation (freeboard). Freeboard specifies how high lowest floors and dry 

floodproofing are above the minimum required elevation. More than 30 communities have 

adopted freeboard of 2 or 3 feet above the BFE, more than 10 have adopted 1.5 feet above the 

BFE, and many have adopted a minimum elevation above the crown of the road (typically 12 

to 18 inches). Prior to the 6th Edition FBCR, which now requires a minimum BFE plus 1 foot, 

nearly 125 communities had individually adopted 1 foot of freeboard.

+ Enclosure limits (prohibition, size limits, access, no partitions). Eighty communities have 

adopted some form of enclosure limits. A small number prohibit walls (other than insect 

screening or lattice). Some communities limit the size to less than 299 square feet (primarily 

in Zone V), while many others limit the size and number of doors and do not allow partitions 

(except crawlspace if required for fire safety).

+ Cumulative Substantial Improvement. More than 80 communities have adopted requirements 

to accumulate costs of improvements and repairs over specific periods of time. The most 

common period of time is 5 years, followed by 10 years, 2 years, and life of structures. Shorter 

periods are typically selected when the objective is to discourage deliberate phasing of 

improvements that, if taken together, would trigger the Substantial Improvement requirement to 

bring structures into compliance with the flood provisions. 

+ Repetitive flood loss. About 40 communities modified the definition of “Substantial Damage” 

to include repetitive flood damage, such that the term includes “flood-related damage sustained 

by a structure on two separate occasions during a 10-year period for which the cost of repairs 

at the time of each such flood event, on average, equals or exceeds 25 percent of the market 

value of the structure before the damage occurred.” Thus, buildings that are determined to 

be substantially damaged by repetitive flooding must be brought into compliance with the 

flood requirements of the FBC. Owners of those buildings, if covered by NFIP flood insurance 

policies, may qualify for Increased Cost of Compliance claims that pay up to $30,000 toward the 

cost of bringing the buildings into compliance.

+ Critical facilities. More than 30 communities have adopted some form of regulation pertaining 

to critical facilities. A common amendment is to define critical facilities to include Flood Design 

Class 3 and 4 structures (see ASCE 24-14 for the Flood Design Class descriptions). Many have 

adopted higher elevation requirements, which may now be superseded by the Flood Design 

SFMO INSTRUCTIONS FOR HIGHER 

STANDARDS

The SFMO provides instructions for local adoption of common higher standards, 

including local technical amendments 

to the flood provisions of the FBC. The 

instructions can be accessed at www.floridadisaster.org/dem/mitigation/floodplain/

community-resources.
2-10 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

BUILDING CODES, STANDARDS, AND REGULATIONS

Class 4 requirement that specifies lowest floors 

and dry floodproofing be at or above the BFE 

plus 2 feet or the 500-year flood elevation 

(elevation of the 0.2-percent-annual-chance 

flood), whichever is higher. A number of 

communities do not permit critical facilities 

in all or part of the SFHA or have adopted 

language requiring alternative locations to be 

considered. 

FLOOD DESIGN CLASS

FEMA’s Highlights of ASCE 24‐14 Flood 

Resistant Design and Construction (2015) 

includes Table 1-1, “Flood Design Class of 

Buildings and Structures,” available online at 

www.fema.gov/building-code-resources.

2.2.4 Floodplain Management Ordinances Coordinated with the FBC 

In 2009, concurrent with the work of the Florida Building Commission’s flood standards workgroup, 

FDEM began developing a model floodplain management ordinance written explicitly to rely on 

the FBC for NFIP-consistent requirements for buildings and structures. The ordinance contains 

administrative provisions, duties and responsibilities of the Floodplain Administrator, provisions 

for determining BFEs and floodways when not specified on Flood Insurance Rate Maps (FIRMs), 

records retention, and other provisions. FEMA supported this work with technical and financial 

assistance. Final approval of the model ordinance was received in January 2013. A major benefit of 

the close collaboration with FEMA is the FEMA Region IV office relies on FDEM’s recommendations 

for approval when communities are required to demonstrate that their ordinances comply with the 

NFIP as part of the flood map revision process.

The FBC-coordinated model ordinance is intended to be administered by the community Floodplain 

Administrator and Building Official and contains direct links with the FBC as follows:

+ Buildings, structures, and facilities that are exempt from the FBC. The NFIP requires

communities to regulate all development. Thus, the scope of the ordinance specifically includes

such buildings and structures and requires conformance with the flood load and flood-resistant

provisions of ASCE 24. The Floodplain Administrator is responsible for inspecting these

buildings and structures.

+ Substantial Improvement and Substantial Damage determinations. The Floodplain

Administrator and Building Official coordinate on these determinations, which are spelled out

in the ordinance. In addition, the ordinance defines “market value.”

+ Variances. Restrictions on variances and conditions and issues that must be examined when 

considering requests for variances are 

specified. FBC Section 117 refers to local 

ordinances when variances to the flood 

provisions of the FBC are requested. 

FDEM anticipated a significant level of effort to 

work with the 467 NFIP-participating communities 

in Florida to transition to the FBC-coordinated 

ordinance. To meet the demand and facilitate 

adoption, the agency procured professional 

services to review draft ordinances and work with 

communities to incorporate community-specific 

ADOPTION OF 

FBC-COORDINATED ORDINANCE

As of mid-2018, more than 80 percent 

of Florida’s NFIP communities have adopted local ordinances based on the 

FBC-coordinated floodplain management 

ordinance. The remaining communities are 

expected to make the transition by the end 

of 2019.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 2-11

BUILDING CODES, STANDARDS, AND REGULATIONS

amendments and higher standards. Considerable attention was paid to preparing higher standards 

that affect the design of buildings in the format required for local technical amendments of the 

FBC (refer to Section 2.2.3).

The SFMO database of higher standards adopted by communities includes common higher 

standards that do not affect the design and construction of buildings in flood hazard areas. As of 

mid-2018, the most common non-building higher standards: 

+ Manufactured home restrictions. Nearly 50 communities adopt restrictions on the installation 

of manufactured homes. While some prohibit manufactured homes in SFHAs, most limit the 

prohibition to the installation of new manufactured homes in Zone V or floodways unless they 

are in existing manufactured home parks or subdivisions that were established before the 

communities joined the NFIP.

+ Compensatory storage. More than 15 communities have adopted some form of compensatory 

storage, most commonly requiring excavation of a volume equivalent to the volume of fill 

brought into flood hazard areas. Some require analyses to demonstrate compensation is 

hydraulically equivalent. 

2.3 Wind Provisions of the Florida Building Code

The design of buildings for wind loads in the State of Florida is governed primarily by the FBCB, 

FBCR, and FBCEB. The 5th and 6th Editions of the FBC reference the 2010 Edition of ASCE 

Standard 7, Minimum Design Loads for Buildings and Other Structures (ASCE 7-10). However, the 

FBCB, FBCR, and FBCEB also contain numerous 

Florida-specific, wind-related amendments that 

exceed the minimum criteria in the I-Codes.

The FBC also contains separate wind, structural, 

and testing requirements for a special zone called 

the “High-Velocity Hurricane Zone.” The HVHZ, 

specifically defined as Miami-Dade and Broward 

Counties, was created for the inaugural version 

of the FBC (2001) as a way to maintain certain 

wind-related provisions from the South Florida 

Building Code. The wind criteria applicable in 

the HVHZ have historically been more stringent than the criteria applied in the rest of the State. 

However, more recent versions of the code have been minimizing the differences.

WIND REQUIREMENTS FOR 

EXISTING BUILDINGS

The FBCEB contains several mitigation “triggers” for roof repairs and reroofing. These 

triggers and mandated mitigation of existing buildings are discussed in Hurricane 

Irma in Florida Recovery Advisory No. 3 

(see Appendix C).

2.3.1 Wind Loads and Wind Design in the FBC

The wind load and wind design requirements of the 5th Edition (2014) and the 6th Edition (2017) 

FBCB and FBCR are similar. Both editions reference ASCE 7-10, and the definition of windborne debris regions, protection of glazed openings, and classification of exposure categories are 

also consistent with ASCE 7. Exceptions permit the use of certain prescriptive high-wind design 

standards primarily for one- and two-family dwellings, although ICC 600 is permitted for Group R2 

buildings (apartments, hotels, dormitories, etc.). These prescriptive standards include:
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BUILDING CODES, STANDARDS, AND REGULATIONS

+ Wood-Frame Construction Manual for One- and Two-Family Dwellings, American Wood Council, 2015

+ Standard for Residential Construction in High-Wind Regions (ICC 600), International Code Council, 

2014

+ Standard for Cold-Formed Steel Framing—Prescriptive Method for One- and Two-Family Dwellings, 2007, 

with Supplement 3, dated 2012 (AISI S230), 2012

Florida-specific design wind speed maps are contained in the 6th Edition (2017) FBCB and FBCR; 

the maps are consistent with ASCE 7-10. The wind speed maps for Risk Category II, III, and IV 

buildings (FBCB) are shown in Figure 2-2 and Figure 2-3, and the wind speed map in the FBCR is 

shown in Figure 2-4.

Figure 2-2: Wind speed map for Risk Category II buildings and other structures

SOURCE: 6TH EDITION [2017] FBCB
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 2-13

BUILDING CODES, STANDARDS, AND REGULATIONS

Figure 2-3: Wind speed map for Risk Category III and IV buildings and other structures

SOURCE: 6TH EDITION [2017] FBCB
2-14 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

BUILDING CODES, STANDARDS, AND REGULATIONS

Figure 2-4: Wind speed map for FBCR buildings

SOURCE: 6TH EDITION [2017] FBCR
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 2-15

BUILDING CODES, STANDARDS, AND REGULATIONS

2.3.2 Florida-Specific Amendments for Wind and Water Intrusion 

As previously stated, the FBC contains numerous Florida-specific amendments related to wind and 

water intrusion, including the requirements in the HVHZ that exceed the minimum requirements 

in the 2015 I-Codes. Table 2-1 lists some notable Florida-specific amendments related to wind and 

water intrusion prevention.

Table 2-1: Notable Florida-Specific Amendments for Wind and Water Intrusion

Non-HVHZ HVHZ

6th 

Edition 

(2017) 

FBCB

• Specifically requires soffits to be designed 

for wall component and cladding loads

• Limits the span of wood structural panels 

used for opening protection to 44 inches

• Enhanced roofing underlayment provisions 

for high-wind areas apply throughout the 

entire State

• Requires labeling on garage doors, impactresistant coverings, and windows to include 

the design wind pressure rating

• Requires all buildings to be designed for wind 

loads; prescriptive high-wind standards are not 

permitted 

• Requires a single wind speed to be used for each 

county

– Miami-Dade County

– Risk Category II = 175 mph

– Risk Categories III and IV = 186 mph

– Broward County

– Risk Category II = 170 mph

– Risk Categories III and IV = 180 mph

• The entire building envelope is required to be 

impact resistant (some deemed-to-comply 

assemblies are provided)

• All areas are required to be designed for Exposure 

Category C unless Exposure Category D applies

• Enhanced roofing underlayment provisions apply 

throughout

• Requires the use of plywood sheathing; oriented 

strand board is not permitted 

6th 

Edition 

(2017) 

FBCR

• Establishes the entire State as requiring wind 

design

– Prescriptive high-wind standards are 

permitted 

– Prescriptive construction provisions in the 

2015 IRC are not permitted 

• Exposure category definitions have been 

revised to be consistent with ASCE 7

• Specifically requires soffits to be designed 

for wall component and cladding loads

• Limits the span of wood structural panels 

used for opening protection to 44 inches

• Enhanced roofing underlayment provisions 

for high-wind areas apply throughout the 

entire State

• Requires labeling on garage doors, impactresistant coverings, and windows to include 

the design wind pressure rating

• References to the use of staples for wall 

covering attachment methods have been 

removed

• Refers to the HVHZ provisions in the FBCB

ASCE = American Society of Civil Engineers; FBCB = Florida Building Code, Building; FBCR = Florida Building Code, Residential; 

HVHZ = High-Velocity Hurricane Zone; IRC = International Residential Code; mph = miles per hour
2-16 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

BUILDING CODES, STANDARDS, AND REGULATIONS

2.4 Florida Manufactured Housing Installation Standards

The Florida Department of Highway Safety and 

Motor Vehicles has jurisdiction over the installation 

of MH units. Requirements for installation, setup, 

tie-downs, and anchoring foundations, with specific 

provisions related to wind loads, are contained in 

Chapter 15C of the Florida Administrative Code. 

With respect to installation in floodprone areas, the 

regulations refer to and incorporate by reference 

the 1985 edition of FEMA 85, Manufactured Home 

Installation in Flood Hazard Areas.

MANUFACTURED HOMES 

CONSTRUCTION

The Manufactured Home Construction 

and Safety Standards, 24 CFR Part 3280, 

developed by the U.S. Department of 

Housing and Urban Development, cover 

the design and construction of manufactured homes.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-1

3Flood-Related Observations

The Irma MAT made general flood-related observations as well 

as examined specific building performance issues. 

This chapter describes the MAT’s observations, which focused on the following:

+ General flood damage 

+ Performance of dry floodproofing 

measures

+ Performance of public restrooms in coastal 

flood hazard areas

The Irma MAT deployed on three occasions: 

September 2017 (pre-MAT), December 2017, 

and February 2018; see text box for additional 

information. The pre-MAT performed a 

cursory review of flood damage to buildings 

at approximately 150 locations in the Florida 

Keys, Southwest Florida, and Southeast 

MAT OBSERVATIONS

Deployments

Pre-MAT: September 22 to 25, 2017

MAT: December 10 to 15, 2017

MAT: February 14 to 15, 2018

Locations

•	 Southwest Florida (Fort Myers to Marco 

Island to Everglades City)

•	 Southeast Florida (Miami and Miami Beach)

•	 The Florida Keys (Tavernier to Key West)

•	 St. Johns County (Vilano Beach and South 

Ponte Vedra Beach)
3-2 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Florida. For the second deployment, the MAT conducted more detailed evaluations of flood 

conditions and flood damage to buildings in the same geographic areas of the pre-MAT visit, at 

approximately 25 general damage sites, 25 floodproofing sites, and 15 public restroom sites. For, the 

third deployment, the MAT visited approximately 20 general damage sites and one public restroom 

site in St. Johns County, FL.

Figure 3-1 shows locations for selected September 2017 observations, and Figure 3-2 shows selected 

locations of flood-related observations made during the December 2017 and February 2018 

deployments. 

Hurricane Irma was a large storm that traveled northward over the entire Florida peninsula. It 

resulted in storm surge and heavy rain in many areas not visited by the MAT. However, the 

MAT observations included in this chapter capture the type and range of effects produced by 

Hurricane Irma.

Figure 3-1: Locations of selected September 22–25, 2017 (pre-MAT) observations for Hurricane Irma
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-3

FLOOD-RELATED OBSERVATIONS 

Figure 3-2: Locations of selected December 10–15, 2017 and February 14–15, 2018 (MAT) observations for 

Hurricane Irma

3.1 General Flood Damage Observations

The Irma MAT, like other post-Hurricane MATs, planned for and made general observations of 

building performance under a variety of flood conditions. Observations of building performance 

under a variety of flood conditions are summarized in this section. The MAT observed many cases 

of erosion and scour, along with variable performance of erosion control structures. Sections 3.1.1 

and 3.1.2 summarize observations made related to these topics.

The extent of flood damage to buildings observed by the MAT varied with the depth of floodwater, 

the amount of energy in the water column (waves, velocity), and type of building design and 

construction (old versus new, at-grade versus elevated, MH unit/recreational vehicle versus sitebuilt/modular). Buildings constructed at or near grade were subject to deeper and more damaging 

flooding. This applied to buildings subject to storm surge and to buildings subject to rainfallinduced flooding.
3-4 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-3 shows how flood damage varied along one street on Big Pine Key. Figure 3-4 shows longduration flooding in the Bonita Springs area. Figure 3-5 and Figure 3-6 show damage to adjacent 

elevated and non-elevated homes on the Atlantic Ocean shoreline of Big Pine Key.

Figure 3-3: Typical range in flood damage observed along Avenue D, in order along the street as indicated 

(Big Pine Key, FL)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-5

FLOOD-RELATED OBSERVATIONS 

Figure 3-4: 

Long-duration flooding in 

the Bonita Springs area 

(Lee County, FL)
3-6 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-5: 

Elevated house with 

unreinforced masonry 

breakaway walls that 

performed as intended 

(Big Pine Key, FL)

Figure 3-6: 

House constructed at grade 

where the masonry walls 

parallel to the shoreline 

were destroyed; this house 

was near the house shown 

in Figure 3-5 

(Big Pine Key, FL)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-7

FLOOD-RELATED OBSERVATIONS 

Performance of breakaway walls below elevated buildings varied. Some walls broke away cleanly 

without damaging the main structure (see Figure 3-7), while others did not. Of those that did not 

break away cleanly, some appeared to cause no damage to the structure (see Figure 3-8), while 

others appeared to cause damage to the columns to which they were attached (see Figure 3-9).

Figure 3-7: 

Example of a breakaway 

wall that was reported by a 

local code official to have 

performed as intended 

(Lower Matecumbe Key, FL)

Figure 3-8: 

Example of partial failure 

of breakaway wall, with 

no associated damage to 

main structure observed 

(Cudjoe Key, FL)
Figure 3-9: Example of a breakaway wall failure that likely contributed 

to damage to columns (Big Pine Key, FL)

The MAT observed considerable debris that had washed around and into buildings in the Florida 

Keys. Debris was composed of building materials and furnishings from damaged and destroyed 

buildings, displaced sheds, automobiles, boats, and recreational vehicles, as illustrated in Figure 

3-10 through Figure 3-13.

3-8 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-10: 

Building debris and 

recreational vehicles washed 

into a canal on 61st Street 

Ocean (Marathon, FL)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-9

FLOOD-RELATED OBSERVATIONS 

Figure 3-11: 

Boat and small debris that 

washed across a canal and 

onto houses 

(Big Pine Key, FL) 

Figure 3-12: 

Car and debris that washed 

into a house 

(Big Pine Key, FL)
3-10 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-13: 

Shed that washed across 

Highway US 1 

(Grassy Key, FL)

3.1.1 Erosion and Scour

The MAT observed a few instances of erosion and scour in Monroe County and widespread dune 

and bluff erosion in St. Johns County. In both counties, buildings with deep foundations performed 

better than buildings with shallow foundations. 

Monroe County

The Monroe County erosion the MAT observed 

was likely due to a combination of waves and 

high-velocity flow across low-lying areas along 

the Atlantic shoreline of the Florida Keys. In 

some cases, the flow could have been affected 

by development practices that channeled or 

confined flow (e.g., privacy walls, driveways, utility 

installations), which contributed to the erosion 

(see Figure 3-14). 

Most building foundations constructed in the last few decades in the Florida Keys are reinforced 

concrete piles that are augered into the soil and underlying rock. These foundations were resistant 

to scour and erosion (see Figure 3-14, Figure 3-15, and Figure 3-16).

The MAT observed one instance of building collapse in the Florida Keys (Figure 3-17). The 

building was a two-story multi-family structure elevated on an open concrete column foundation, 

with ground-level parking below (this building is 600 feet from the undermined building shown in 

Figure 3-14).

EROSION AND SCOUR

Erosion: Loss of soil over a large area.

Scour: Localized loss of soil due to interaction of flow and building components.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-11

FLOOD-RELATED OBSERVATIONS 

Figure 3-14: Scour near and around building foundation (Lower Matecumbe Key, FL) 
3-12 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-15: 

Scour was likely due to 

waves and high-velocity 

flow at this house on Long 

Beach Drive (same house 

is shown in Figure 3-6) 

(Big Pine Key, FL)

Figure 3-16: 

Erosion was likely due to 

wave attack around the 

foundation of this house 

on Sombrero Beach Road 

(Marathon, FL)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-13

FLOOD-RELATED OBSERVATIONS 

Figure 3-17: Collapsed building (Lower Matecumbe Key, FL)

St. Johns County

Erosion observed by the MAT in St. Johns County was a result of storm surge and waves attacking 

oceanfront dunes and bluffs. The same shoreline was also battered by storm surge and waves during 

Hurricane Matthew (2016) and various northeast storms before and after Irma. 

Many undermined buildings were on deep pile foundations and survived the erosion (Figure 3-18 

and Figure 3-19), but many were rendered uninhabitable pending repairs to buildings and utilities 

(and in some cases, replacement of soil). Some houses were on shallow foundations and collapsed 

(Figure 3-20). 
3-14 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-18: 

Undermined house on deep 

piles that survived erosion 

(Vilano Beach, FL)

Figure 3-19: 

Undermined houses 

constructed on top of the 

dune (Vilano Beach, FL)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-15

FLOOD-RELATED OBSERVATIONS 

Figure 3-20: Collapsed house on shallow foundation that was undermined by erosion induced by Hurricane Irma 

(Vilano Beach, FL) 

SOURCE: UPPER PHOTOGRAPH COURTESY OF CIVIL AIR PATROL (SEPTEMBER 20, 2017); LOWER PHOTOGRAPH COURTESY OF ST. JOHNS 

COUNTY (SEPTEMBER 12, 2017).

Figure 3-21 through Figure 3-26 illustrate dune erosion that occurred at selected FIS transect 

locations during Hurricane Matthew and Hurricane Irma.1 The “preliminary transect” lines 

represent pre-Matthew ground elevations. The “preliminary modeled” lines represent the FIS 

estimation of dune erosion during a base flood. In some cases, Hurricane Matthew erosion was 

greater than Hurricane Irma erosion, while in others Hurricane Irma erosion was greater. In some 

cases, the modeled erosion understated actual erosion, while in others it overstated actual erosion. 

This information indicates high longshore variability in dune erosion may occur in any given storm. 

It also demonstrates that building foundations in high dune areas may sustain 5 to 10 feet or more 

of vertical erosion during a severe storm event.

1 Post-Matthew and pre-Irma beach nourishment was implemented in some locations, and the profiles in Figure 3 22 through Figure 3 26 

reflect this. Details on volumes and locations of nourishment are unknown.
3-16 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-21: 

Locations of FIS transects 

28–39, where comparative 

beach and dune profiles 

are shown in Figure 3-22 

through Figure 3-26 

(R-numbers are survey 

monuments established by 

the State of Florida)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-17

FLOOD-RELATED OBSERVATIONS 

Figure 3-22: Beach and dune profiles at Transect 28

Figure 3-23: Beach and dune profiles at Transect 30
3-18 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-24: Beach and dune profiles at Transect 33

Figure 3-25: Beach and dune profiles at Transect 37
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-19

FLOOD-RELATED OBSERVATIONS 

Figure 3-26: Beach and dune profiles at Transect 39

3.1.2 Erosion Control Structures

The pre-MAT and MAT observed many erosion control structures during field visits in canal, bay, 

and estuarine areas (Southwest Florida, Southeast Florida, and the Florida Keys) and along the 

oceanfront (St. Johns County). Many of these structures survived Hurricane Irma and protected 

land behind them, but some showed signs of damage or failure. 

Numerous instances of canal or estuarine bulkhead failures were observed in Southwest and 

Southeast Florida. Failures were typically associated with saturated soil behind bulkheads exerting 

loads that exceeded the capacity of anchor systems or insufficient embedment of the bulkhead into 

the ground. Anchor system failure likely caused the top of the bulkhead to rotate toward the water, 

as shown in Figure 3-27. Failures of bulkheads that were insufficiently embedded into the ground 

likely resulted in the toe of the bulkheads moving toward the water, as shown in Figure 3-28. 

Similar anchor system and toe embedment failures have occurred for decades during periods of 

heavy rain when backfill becomes heavily saturated, and the failures observed after Hurricane Irma 

are not new or different. The canal and estuarine bulkhead failures that the MAT observed did 

not lead to undermining and failure of buildings, but bulkhead failures could be a concern where 

buildings are located close to bulkheads or where bulkheads are constructed close to buildings.
3-20 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-27: 

Failure of bulkhead (anchor 

system) (Naples, FL)

Figure 3-28: 

Bulkhead toe failure 

(insufficient embedment) 

(Naples, FL)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-21

FLOOD-RELATED OBSERVATIONS 

Oceanfront bulkheads that were

supposed to prevent loss of soil under 

buildings did not always perform as 

intended to protect the buildings. Some 

oceanfront bulkhead failures were 

observed in St. Johns County, and such 

failures exposed the foundations and 

septic systems of homes to undermining. 

Homes on very deep foundations 

withstood the loss of soil, while homes 

on shallow foundations did not. Figure 

3-29 shows one such bulkhead failure 

and the resulting collapse of a building 

with a shallow foundation.

ADDITIONAL INFORMATION

Additional information pertaining to dry floodproofing for areas affected by Hurricanes Irma and 

Harvey in 2017 can be found in the following recovery advisories:

•	 Dry Floodproofing: Operational Considerations

(Hurricane Irma in Florida, Recovery Advisory 1, 

2018d)

•	 Dry Floodproofing: Planning and Design 

Considerations (Hurricane Harvey in Texas, 

Recovery Advisory 1, 2018e)

Figure 3-29: House on a shallow foundation that collapsed after it was undermined following failure of the bulkhead 

during Hurricane Irma (St. Johns County, FL) 
3-22 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

3.2 Performance of Dry Floodproofing Measures

The MAT was tasked with evaluating how dry floodproofing systems had performed during 

Hurricane Irma. Approximately 25 sites with dry floodproofing systems were investigated. Not 

all of the systems were deployed prior to Irma, and only some of those deployed were “tested” by 

Irma (i.e., in many cases, the flood level did not reach the flood barrier or closure). In cases where 

floodproofing was tested by floodwater, most buildings sustained at least minor flooding, and some 

sustained more serious flooding. 

Evaluations of dry floodproofing performance were sometimes hampered by a reluctance of building 

owners and managers to discuss their dry floodproofing. Based on discussions, this reluctance 

appears to be related to concerns that comments made to the FEMA MAT might somehow affect the 

floodproofing credit for their NFIP flood insurance policy. However, the MAT was able to obtain 

enough information to make general observations about dry floodproofing performance, owner/

manager understanding of dry floodproofing requirements, deployment successes and failures, 

implementation issues, and availability and scope of floodproofing plans. One designer interviewed 

by the MAT indicated that he specifies dry floodproofing on all his projects, but his two main worries 

are gasket degradation and the time required to deploy dry floodproofing systems. 

Based on interviews conducted by the MAT, building managers and owners understand dry 

floodproofing concepts and understand that floodproofing can lead to NFIP flood insurance 

premium credit, but may not appreciate the importance of design and deployment details necessary 

to achieve successful floodproofing systems. In many cases, deployment is handled by contractors, 

so owners and managers may not understand installation and maintenance procedures, and they 

may not conduct annual testing. 

Finally, there appears to be a need for guidance on maintaining and deploying dry floodproofing 

systems, as well as on developing emergency operations and maintenance plans that meet the 

requirements of Chapter 6 of ASCE 24 (the standard referenced by the FBC and specified by FEMA 

Form 086-0-34, NFIP Floodproofing Certificate for Non-Residential Structures). 

3.2.1 Failure Modes 

Some dry floodproofing systems were not subject to flooding, but still sustained some minor water 

accumulation behind them due to rainwater between the floodproofing system and the building 

face (see Figure 3-30). In one case, significant flooding infiltrated a building as a result of building 

envelope failure that allowed large quantities of rainwater to enter and become trapped behind the 

floodproofing system.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-23

FLOOD-RELATED OBSERVATIONS 

Figure 3-30: Flood plank system deployed at utility company building (Key West, FL)
3-24 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Of those dry floodproofing systems that were deployed and tested, a few worked as intended (see 

Figure 3-31), but most were reported to have leaked (minor quantities of water) or failed (major 

quantities of water; see Figure 3-32). Failure modes described by those responsible for implementing 

floodproofing or observed by the MAT at many floodproofing locations included lack of gaskets, 

failure of gaskets due to physical damage or degradation over time, gasket compression during 

storage, and leaking valves (air gasket systems). 

More significant floodproofing failures were likely associated with human intervention aspects 

of floodproofing (installation and maintenance). In one case, a contractor failed to properly 

install the complete floodproofing system, allowing floodwater to enter the building through the 

unprotected area.

Figure 3-31: A high-rise residential building under construction was successfully protected by a dry floodproofing 

method that used flood panels and doors; the floodproofing was installed by the building contractor (Miami, FL)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-25

FLOOD-RELATED OBSERVATIONS 

Figure 3-32: Floodproofing system components at a historic building (top); parts of the system failed and approximately 

3 feet of flooding infiltrated part of the building (Miami, FL)
3-26 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

3.2.2 Implementation Considerations

One of the MAT’s concerns is the time necessary to implement some of the observed dry 

floodproofing systems. While some systems can be (and were) deployed in 2 hours or less by just 

two workers (see Figure 3-30), other complex systems likely required many workers using material 

handling equipment to lift and position heavy flood posts and panels over 2 or more days (see 

Figure 3-31). Small panels and planks are relatively easy to handle and install and do not require 

equipment. Single, large, heavy panels require more workers and equipment to install and can be 

difficult to lift, hold, align, and secure. As one architect interviewed by the MAT said, “simpler is 

better” when it comes to floodproofing systems.

Lengthy deployment times not only increase the likelihood of flooding when systems are installed, 

but they leave insufficient time to install the dry floodproofing measure before rapid-onset, intense 

rainfall events (“rain bombs”). 

The MAT observed that flood protection components often were not stored in a secure and dedicated 

location. If components are not stored securely in a designated area, they can be misplaced or stolen. 

In many cases, the storage arrangements did not facilitate component inventory, making it hard to 

identify missing parts.

3.2.3 Operations and Maintenance Plans 

The MAT obtained written plans for deployment of dry floodproofing systems for some floodproofed 

sites, but for other sites, plans either were not obtained or may not exist. Plans that were reviewed 

varied in scope and complexity, and some did not include all necessary information for successful 

installations. The required installation knowledge may reside with current staff, but staff members 

change over time, and institutional floodproofing knowledge may be lost if it is not documented. 

3.3 Performance of Public Restrooms

The MAT visited 15 public restroom buildings and sites on or near the shoreline in public parks in 

Lee, Collier, Monroe, and St. Johns Counties. 

The restrooms visited were of varying ages and construction and were subject to a variety of flood 

conditions during Hurricane Irma, depending on building location and elevation. Some restrooms 

were likely exposed to Zone V conditions during Irma (wave heights of 3 feet or higher), while 

others were likely exposed to shallow flooding and small waves (or no waves). 

Table 3-1 summarizes the MAT restroom observations.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-27

FLOOD-RELATED OBSERVATIONS 

Table 3-1: Summary of Public Restrooms Visited

Site Identifier Name/Location MAT Observations

1 Bunche Beach Preserve

(Lee County)

• Zone VE(a)

• Intact and in use, December 2017

• Elevated on masonry foundation walls

• Owner reported possible shallow flooding in grade-level 

enclosure

• See Figure 3-33

2 Lovers Key State Park

(Lee County)

• Zone VE(a)

• Intact and in use, December 2017

• Timber pile foundation

• Owner reported shallow flooding in enclosure below building

• See Figure 3-34

3

Barefoot Beach Preserve 

County Park

(Collier County)

• Zone VE(a)

• Intact and in use, December 2017

• Timber pile foundation

• Flooding was likely shallow and passed beneath building

• There may have been wind damage to building

• See Figure 3-35

4

City of Naples Pier – two 

buildings

(Naples)

• Zone VE(a)

• Intact and in use, December 2017

• Concrete pile foundation

• Flooding was likely shallow and passed beneath building

• See Figure 3-36

5 Tigertail Beach Park

(Marco Island)

• Zone AE(a)

• Intact and in use, December 2017

• Timber pile foundation

• Flooding was likely shallow and passed beneath elevated 

building

• See Figure 3-37

6 Tigertail Beach Park

(Marco Island)

• Zone AE(a)

• Intact and in use, December 2017

• At-grade building

• Likely shallow flooding inside restroom building

• See Figure 3-38

7 Sombrero Beach City Park

(Marathon)

• Zone AE(a)

• Intact and closed, December 2017

• Concrete pile foundation

• Flooding was likely shallow and passed beneath building

• See Figure 3-39

8 Sombrero Beach City Park

(Marathon)

• Zone AE(a)

• Intact and closed, December 2017

• Concrete pile foundation

• Flooding was likely shallow and passed beneath building

• Construction identical to site 7; see Figure 3-39

9 Long Key State Park

(Monroe County)

• Zone AE(a)

• Damaged by flood, September 2017

• At-grade masonry building 

• Building demolished by owner and site cleared between 

September 2017 and December 2017

• See Figure 3-40

(a) Flood zone at time of Hurricane Irma, not necessarily at time of restroom construction. (continued on page 3-28)
3-28 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Table 3-1: Summary of Public Restrooms Visited (concluded)

Site Identifier Name/Location MAT Observations

10 Long Key State Park

(Monroe County)

• Zone AE(a)

• Intact and closed (park closed), December 2017

• Concrete column foundation

• Flooding was likely shallow and passed beneath building

• See Figure 3-41

11

Bahia Honda State Park, 

Sandspur Day Use

(Monroe County)

• Zone AE(a)

• Washed away by Hurricane Irma, September 2017

12

Bahia Honda State Park, 

Sandspur Camping 

Restroom

(Monroe County)

• Zone AE(a)

• Intact and closed (park closed), December 2017

• Elevated on high masonry foundation walls with louvers

• Flooding in enclosure below elevated building was 

approximately 5 feet deep (approximately 1 foot below floor of 

restroom)

• See Figure 3-42

13

Bahia Honda State Park, 

Loggerhead Restroom

(Monroe County)

• Zone AE(a)

• Damaged by wind and closed (park closed), September 2017

• Wood frame building elevated on timber pile foundation

• Building demolished by owner between September 2017 and 

December 2017 

• Replaced with temporary (mobile) toilet building

• See Figure 3-43

14 Veterans Memorial Park

(Monroe County)

• Zone AE(a)

• Damaged by flood, September 2017

• At-grade masonry building 

• See Figure 3-44

15 Surfside Park, Vilano Beach

(St. Johns County)

• Zone VE(a)

• Intact and functional, February 2018 

• Wood frame, at-grade building (walls do not extend to slab) 

• See Figure 3-45

(a) Flood zone at time of Hurricane Irma, not necessarily at time of restroom construction.

For those restrooms damaged by flooding, the degree of damage ranged from complete destruction, 

to some structural damage, to damage to doors and fixtures only. The degree of damage depended 

on both flood conditions (flood depth, flood velocity, wave conditions) and building characteristics 

(floor elevation, robustness of construction, features allowing flow-through). Figure 3-33 through 

Figure 3-45 show the restrooms that the MAT observed (site numbering refers to Table 3-1). For the 

following observations, see Table 3-1.

+ One restroom was destroyed by Hurricane Irma and nothing remained to evaluate (Bahia Honda 

State Park – Sandspur Day Use, Site 11). This restroom was likely exposed to Zone V conditions. 

+ Two restrooms were heavily damaged and observed by the pre-MAT in September 2017, but were 

demolished by the Florida Division of Recreation and Parks before the December 2017 return 

visit to the sites (Long Key, Site 9; Bahia Honda – Loggerhead, Site 13). The Long Key restroom 

was likely exposed to Zone V conditions.

+ One flooded restroom that did not sustain structural damage, Veterans Memorial Park (Site 14), 

was likely subject to Zone V flood conditions.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-29

FLOOD-RELATED OBSERVATIONS 

+ Two restrooms were at grade and were flooded (Tigertail, Site 6; Veterans, Site 14). The Tigertail 

restroom was far from the shoreline, sheltered by 200 feet of dense vegetation, and subject to 

storm surge only. The Veterans restroom was close to the shoreline and subject to storm surge 

and wave action. 

+ One restroom was constructed with at-grade enclosures and partial-height walls (Surfside Park, 

Site 15). Whether the floor slab was flooded as a result of Hurricane Irma is unclear, but if it was, 

the flood depth would have been shallow (inches).

+ Three restrooms were elevated above the Hurricane Irma flood level and had ground-level 

enclosures that were or may have been flooded (Bunche Beach Preserve, Site 1; Lovers Key, 

Site 2; and Bahia Honda, Site 12). 

+ Six restrooms were elevated above the Hurricane Irma flood level and had no ground-level 

enclosure (Barefoot Beach, Site 3; City of Naples Pier, Site 4; Tigertail, Site 5; Sombrero Beach, 

Sites 7 and 8; and Long Key, Site 10).

Figure 3-33: 

Elevated restrooms with 

ground-level enclosure. 

Bunche Beach Preserve 

restroom (Site 1; Lee 

County), where the degree 

of flooding in the enclosure, 

if any, would have been 

shallow.
3-30 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-34: 

Elevated restrooms with 

ground-level enclosure. 

Lovers Key State Park 

restroom (Site 2; Lee County) 

enclosure sustained shallow 

flooding but no damage 

during Hurricane Irma.

Figure 3-35: 

Elevated restroom 

at Barefoot Beach 

Preserve County Park 

(Site 3; Collier County)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-31

FLOOD-RELATED OBSERVATIONS 

Figure 3-36: Elevated restrooms (Site 4; City of Naples Pier)
3-32 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-37: 

Elevated restroom at 

Tigertail Beach Park (Site 5; 

Marco Island, Collier County)

Figure 3-38: Grade-level restrooms at Marco Island (Site 6; Collier County)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-33

FLOOD-RELATED OBSERVATIONS 

Figure 3-39: 

Elevated restrooms at 

Sombrero Beach Park 

without ground-level 

enclosure and that 

sustained no flood damage 

during Hurricane Irma 

(Site 7; Marathon)

Figure 3-40: 

Elevated Long Key State Park 

restroom without groundlevel enclosure and that 

sustained no flood damage 

during Hurricane Irma 

(Site 9; Monroe County)
3-34 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-41: Restroom in Long Key State Park that sustained structural flood damage (Site 10; Monroe County)

Figure 3-42: 

Elevated restroom with 

ground-level enclosure at 

Bahia Honda State Park, 

Sandspur Campground; 

Hurricane Irma flood depth 

in enclosure was 5 feet 

(Site 12; Monroe County)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-35

FLOOD-RELATED OBSERVATIONS 

Figure 3-43: 

Elevated restroom at 

Bahia Honda State 

Park, Loggerhead 

(Site 13; Monroe County)
3-36 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

FLOOD-RELATED OBSERVATIONS 

Figure 3-44: Grade-level Veterans Memorial Park restroom that was likely exposed to Zone V conditions 

(Site 14; Monroe County)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 3-37

FLOOD-RELATED OBSERVATIONS 

Figure 3-45: Grade-level Vilano Beach Surfside Park restrooms (Site 15; St. Johns County)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-1

4Wind-Related Observations

The MAT Wind team assessed one- and two-family dwellings in 

the vicinity of the first and second Florida landfall locations.

Building assessments also included some multi-family dwellings (apartments and condominiums) 

and MH units and also covered Key West eastward to Duck Key and throughout Collier County, as 

well as the Miami area. 

Estimated wind speeds from Hurricane Irma did not approach the design wind speeds required 

by the last six editions of the FBC. Each photograph caption in this chapter includes both the 

estimated wind speed for the photograph location during the storm and estimated design wind 

speed for comparison. Estimated event wind speeds were taken from Applied Research Associates 

data, and ASCE 7-10 design wind speeds, which are referenced in the current edition of the FBC, 

were taken from the Applied Technology Council (ATC) Hazards by Location website.1 Wind speeds 

provided are 3-second peak gust for Risk Category II buildings. Wind speed is not the only factor 

for determining wind pressures or levels of damage; however, wind speeds provide a good basis for 

comparing event conditions and design requirements. In addition to high wind pressures, damage 

to buildings may be caused by wind-borne debris. However, wind speeds were used to more easily 

compare event conditions and design requirements.

1 The ATC Hazards by Location website is available at hazards.atcouncil.org/.
4-2 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

In addition to estimated wind speed and estimated design wind speed in each photograph caption, 

the text describing each figure identifies the year the building was constructed. The date built is 

provided to offer some context with respect to the wind provisions that were in effect when the 

building was permitted for construction. The estimated design wind speed may not be correlated 

with the wind requirements of the codes that were in effect when the building was built. Further, 

damaged components shown in the photographs may have been replaced since the original date of 

construction. Where the property appraisal databases indicated that work permits were issued after 

the original date of construction, the date of the permitted work is noted for damaged components 

identified in the photographs.

Although failures of the main wind-force resisting systems (MWFRSs) were observed in some 

buildings, as described in Section 4.1, most buildings designed and constructed to comply with the 

FBC performed well structurally. However, many of these same buildings sustained wind-induced 

failures of building envelope components that allowed wind-driven rain to penetrate, resulting in 

costly damage, as described in Section 4.2. 

Section 4.3 describes performance assessments of MH units and includes observations on anchorage 

(tie-downs) and damage resulting from failure of attached appurtenances. 

4.1 Main Wind-Force Resisting System Performance

The MWFRS is defined in ASCE 7-10 as an assemblage of structural elements assigned to provide 

support and stability for the overall structure. Examples of MWFRS elements include shear 

walls, roof diaphragms, and structural frames. Wind-induced structural damage to MWFRS was 

not widespread and, where observed, mostly occurred in older (pre-FBC) buildings. Damage 

observations did include roof failure and loss of exterior walls.

4.1.1 Roof Failure

Wind damage to roof structures was often found to have initiated through loss of the roof covering 

or breaching of the attic envelope, though the cause of the initial failure cannot always be 

determined after the event. Once wind enters a building, failures can progress to other components 

and connections along numerous load paths.

Figure 4-1 shows an elevated, single-story, wood-framed house (built in 1988) that lost nearly all its 

roof sheathing, most likely due to withdrawal of the roof decking-to-framing fasteners. Numerous 

roof truss top chords located near the roof ridge were also damaged or missing, but roof framing 

adjacent to the front wall and the roof-to-front wall connections remained intact (see bottom photo 

in Figure 4-1). The roof truss bottom chords remained in place, providing lateral support that 

prevented wall collapse.

Another example of roof damage on a pre-FBC dwelling (built in 1923) in Miami is shown in Figure 

4-2, where large sections of roof were picked up by Irma’s winds and dropped onto the neighboring

house. As shown in the red circle, where connected, the conventional wood frame roof and bond

beam separated from the masonry wall.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-3

WIND-RELATED OBSERVATIONS

Figure 4-1: 

House with structural 

damage to roof system 

(EWS = 113 mph; EDWS = 

180 mph) (Sugarloaf Key)

Figure 4-2: 

Residence where a roof-towall connection failed 

(EWS = 78 mph; EDWS = 

169 mph) (Miami)
4-4 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

4.1.2 Wall Failure

Framed walls of residential structures collapsed where significant portions of the roof and ceiling 

diaphragm were destroyed by wind and the lateral support for the walls was compromised.

Figure 4-3 shows the south end of an elevated one-story, wood-framed residence (built in 1986) on 

Cudjoe Key where roof-to-wall connections failed to prevent large portions of the conventionally 

framed roof from lifting away. The rafters separated from the connectors, which are visible along 

the top of the wall everywhere the roof is missing. The MAT could not determine why the connection 

failed; the connectors may not have been adequate to resist uplift forces associated with Irma’s winds 

on Cudjoe Key, or they may not have been installed according to the manufacturer’s instructions. 

Pre-damage images show the north end of the house had a screened porch; all that remains of 

the porch is shown on Figure 4-4 and Figure 4-5, where the remaining post and header are visible 

along the right side of Figure 4-4 and left side of Figure 4-5. An exterior wall section adjacent to 

the screened porch also collapsed and is also shown in the images. One possible scenario is that 

the overhang portion of the screened porch began failing and created a breach in the envelope, 

allowing wind to enter the interior of the building and create high internal pressures.

Another example of wall failure was observed on Ramrod Key, as shown in Figure 4-6. The twostory, wood-framed residence (built in 1990) lost roof trusses above the east-facing (ocean-facing) 

second floor area; two exterior walls were lost from the room below the missing roof trusses, and the 

adjacent deck floor collapsed onto the porch floor below.

Figure 4-3: 

South end of east-facing 

wall; the south end of the 

roof remained in place 

(EWS = 113 mph; EDWS = 

180 mph) (Cudjoe Key)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-5

WIND-RELATED OBSERVATIONS

Figure 4-4: 

North end of east-facing wall 

where the roof was (EWS = 

113 mph; EDWS = 180 mph) 

(Cudjoe Key)

Figure 4-5: 

Remainder of the screened 

porch and exterior wall 

(EWS = 113 mph; EDWS = 

180 mph) (Cudjoe Key)
4-6 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

Figure 4-6: 

House with roof structure 

loss and collapse of the 

second floor exterior wall 

and adjacent deck (EWS = 

113 mph; EDWS = 180 mph) 

(Ramrod Key)

4.2 Envelope 

Although MAT observations of structural damage from Hurricane Irma winds were almost 

exclusively limited to pre-FBC (prior to March 1, 2002, the date the first edition FBC went into effect) 

residential buildings, the MAT observed envelope damage on both older and newer construction. 

The building envelope includes exterior doors, windows, skylights, exterior wall coverings, soffits, 

roof systems, and attic vents. In buildings elevated on open foundations, the floor is also considered 

a part of the envelope. The most frequently damaged elements of these envelope systems observed 

by the MAT were roof coverings, soffits, and exterior wall coverings. While less frequent, damage to 

glazed openings, impact-protection systems, and garage doors was also noted. 

4.2.1 Roof Coverings

MAT wind observations of roof covering loss are grouped according to common material types 

present in South Florida: asphalt shingles, tile, and metal. In many cases, the reason for the damage 

could not be determined because damaged roofs were under repair or covered by tarps.

4.2.1.1 Asphalt Shingles

Asphalt shingle loss was observed to be widespread, especially in the Florida Keys. Asphalt shingle 

failure was observed on both older dwellings and those built after adoption of the FBC. 

The roof of the Big Coppitt Key house (built in 2005) shown in Figure 4-7 and Figure 4-8 was 

mostly hidden under a tarp, but the uncovered slope reveals shingle loss near the eaves and ridge. 

Figure 4-9 shows another post-FBC dwelling (built in 2007) with significant asphalt shingle loss that 

was observed in Marathon.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-7

WIND-RELATED OBSERVATIONS

Figure 4-7: 

The MAT could not observe 

much of the asphalt roof 

damage on this house 

because it was covered by a 

tarp (EWS = 111 mph; 

EDWS = 180 mph) 

(Big Coppitt Key)

Figure 4-8: 

Asphalt shingle loss shown 

inside yellow ovals for house 

shown in Figure 4-7 (EWS = 

111 mph; EDWS = 180 mph) 

(Big Coppitt Key)

Figure 4-9: 

House with asphalt shingle 

loss as evidenced by tarp 

(EWS = 120 mph; EDWS = 

180 mph) (Marathon)
4-8 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

Asphalt shingle loss was limited on the Sugarloaf Key house (built in 1997) shown in Figure 4-10, 

but the pattern of loss near the ridge remains evident in the inset photo where shingle-to-roof 

deck nails remain in place. The Figure 4-10 inset photo indicates the shingles were likely installed 

incorrectly, because the shingle-to-roof deck nails were positioned too close to the top edge of the 

shingle. As shown in Figure 4-11, asphalt shingle nails in high-wind regions should be positioned 

close to the centerline of the shingle to secure the shingle underneath and decrease the moment 

arm of the uniform wind pressure acting on the shingle.

Figure 4-10: 

Residence that lost shingles 

near the ridge (EWS = 113 mph; 

EDWS = 180 mph) 

(Sugarloaf Key)

Figure 4-11: 

Recommended asphalt shingle nail 

locations for high wind regions

As the MAT anticipated, older asphalt shingle roofs on pre-FBC dwellings were more vulnerable to 

wind damage than newer roofs on post-FBC buildings. Figure 4-12 shows a typical example from 

Marco Island (built in 1971) where asphalt shingle loss is visible near the main ridge and between 

the hips above the garage.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-9

WIND-RELATED OBSERVATIONS

Figure 4-12: 

House with shingle loss 

near main ridge and 

between roof hips (yellow 

oval) (EWS = 109 mph; 

EDWS = 170 mph) 

(Marco Island)

4.2.1.2 Roof Tile

Based on MAT observations, damage to roof tile was limited and generally minor. However, the 

MAT observed failure of several older, pre-FBC roofs with mortar-set roof tiles as described below. 

The Cudjoe Key house (built in 1989), shown in Figure 4-13, lost a significant number of tiles, 

particularly at the hips and garage ridge. The Florida’s Association of Roofing Professionals / Tile 

Roofing Institute (FRSA/TRI) Florida High Wind Concrete and Clay Roof Tile Installation Manual, Fifth 

Edition (2012) (FRSA/TRI Manual) requires mortar-set hip and ridge tiles to be fully embedded in 

mortar. The hip tiles shown in 4-13 were not fully embedded in mortar.

Figure 4-13: 

Roof tile failure (EWS = 113 

mph; EDWS = 180 mph) 

(Cudjoe Key)
4-10 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

Similar damage was observed along the front eaves, ridge, and area along and adjacent to the left 

hip over the front porch of the roof on the Duck Key house (built in 1984) shown in Figure 4-14. 

Although no measurements could be taken, the first course of tile appears to project too far over the 

eave. The FRSA/TRI Manual specifies that tiles must overhang the eave at least 3⁄4 inch but not more 

than 2 inches. Additionally, the first course near the eave does not appear to be set in mortar, as the 

first row of mortar patties are beyond the first course of tile.

Figure 4-14: 

House lost roof tiles across most of its 

front eaves (red arrows) (EWS = 111 

mph; EDWS = 180 mph) (Duck Key)

4.2.1.3 Metal Roof Systems

Residential metal roof systems performed well overall, with a few isolated instances of damage. 

The damage to metal roof systems that the MAT observed was generally limited to roof edges. For 

example, the metal fascia cover separated from the fascia board along the front- and side-facing 

gables of the Sugarloaf Key house (built in 2003) shown in Figure 4-15. The metal roof trim directly 

above the missing fascia covers had also peeled back, but the edge of the metal roof system itself 

appeared to be intact where visible along the right side of the front-facing gable.

The metal roof system damage shown in Figure 4-16 appears to be limited to the hip caps of the 

Sugarloaf Key residence (built in 1992). Monroe County property appraisal data indicate that the 

roof was installed in 1999. 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-11

WIND-RELATED OBSERVATIONS

Figure 4-15: 

House with separated 

metal roof trim and missing 

fascia cover (red ovals) 

along gable end. (EWS = 

113 mph; EDWS = 180 mph) 

(Sugarloaf Key)

Figure 4-16: 

House with damaged metal 

roof system (EWS = 113 

mph; EDWS = 180 mph) 

(Sugarloaf Key)

4.2.2 Soffits

The MAT observed widespread damage to soffits in the Florida Keys, particularly vinyl soffits. MAT 

wind observations of soffit loss are grouped according to common material types present in South 

Florida: vinyl and metal (aluminum and steel). 

In some cases, vinyl soffit failure was also associated with fascia cover loss. While further study is 

needed, the loss of the fascia cover could have resulted in more wind exposure on the edges of 

soffits, affecting their performance. Information on soffit installation in Florida is available in 

Florida Recovery Advisory 2, Soffit Installation in Florida (2018h) (Appendix C). 
4-12 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

4.2.2.1 Vinyl

Vinyl soffit panel assemblies were the most common soffit variety observed by the MAT. Wind 

damage to vinyl soffit assemblies was widespread, especially in the Florida Keys. 

The Summerland Key dwelling (built in 2008) in Figure 4-17 shows an example of soffit failure 

associated with fascia cover loss. Interrelated fascia cover/soffit damage was also observed in a house 

built in 2001 on Little Torch Key, shown in Figure 4-18. 

Figure 4-17: 

House that lost its vinyl 

soffit panel (EWS = 113 

mph; EDWS = 180 mph) 

(Summerland Key)

Not all observed vinyl soffit damage was associated with fascia cover loss. The Sugarloaf Key house 

in Figure 4-19 (built in 1995) lost its vinyl soffit in several areas; the red outline shows where the 

soffit panel was stripped from the assembly’s J-channel, which remains attached along the exterior 

wall. The soffit appears to have been attached to only a single nailing strip across the midpoint of 

the framing above. 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-13

WIND-RELATED OBSERVATIONS

Figure 4-18: 

House that lost its soffit along the 

right side of the front-facing gable 

(EWS = 114 mph; EDWS = 180 mph) 

(Little Torch Key)

Figure 4-19: 

House with vinyl soffit 

damage not caused by 

fascia loss (EWS = 113 

mph; EDWS = 180 mph) 

(Sugarloaf Key)
4-14 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

 Figure 4-20 shows similar soffit panel attachment and loss on a Sugarloaf Key dwelling (built in 

1999). The wider eaves included a second nailing strip to attach the vinyl soffit panels, but the 

attachment did not prove adequate for wind pressures experienced during Hurricane Irma.

The MAT also observed post-FBC construction with vinyl soffit damage outside the Florida Keys, as 

demonstrated by a house in Goodland (Collier County) as shown in Figure 4-21. The dwelling (built 

in 2005) is part of a development described in detail in the text box “Vinyl Siding/Soffit Failure 

Example” in Section 4.2.3 and is another example of soffit failure associated with fascia cover loss. 

Although the missing fascia cover played a role by elevating wind pressures within the closed soffit 

system shown in Figure 4-21, the unconventional installation provided inadequate support for the 

soffit panels. The two parallel runs of soffit appear to be joined at the eave’s midpoint with back-toback J-channels. With no nailing strip along the exterior wall, the inside edge of the soffit system 

could only be attached directly to framing at 24 inches on center. 

Figure 4-20: 

Dwelling with similar soffit 

panel attachment and loss 

as shown in Figure 4-19 

(EWS = 113 mph; EDWS = 

180 mph) (Sugarloaf Key)

Figure 4-21: 

House with soffit loss (EWS = 110 mph; 

EDWS = 169 mph) (Goodland)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-15

WIND-RELATED OBSERVATIONS

4.2.2.2 Metal

Metal soffit assemblies were not as common as vinyl soffit assemblies in areas visited by the MAT. 

However, the MAT did observe wind damage to metal soffits in the Florida Keys and Collier County. 

 Figure 4-22 shows metal soffit panel loss along the corner of a Ramrod Key front porch (house built 

in 2005). The remains of the soffit attachment, which were fastened directly to the nailing strip 

along the outside edge and held in place by a channel above the porch opening, are indicated by 

the red arrow. Similar to the damage pattern noted in the previous discussion on vinyl soffits, some 

metal soffit panels were missing; an example is shown in Figure 4-23, where soffits were missing 

below the Big Pine Key house’s (house built in 1989) screened porch gable end outlooker rafters, 

directly below an area where the fascia cover had blown away (compare with Figure 4-17).

Figure 4-22: 

 Metal soffit loss on house 

(EWS = 113 mph; EDWS = 

180 mph) (Ramrod Key)

Figure 4-23: 

House with metal soffit loss 

below missing fascia cover 

(EWS = 114 mph; EDWS = 

180 mph) (Big Pine Key)
4-16 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

ROOF VENTILATION/SOFFIT VENTS

Refer to Section R806 of the 6th Edition (2017) Florida Building Code, Residential (FBCR) for roof ventilation requirements. To avoid water entry at soffit vents, options include eliminating soffit vents and 

providing an alternate method for roof ventilation, or designing for an unvented attic. For additional 

guidance on mitigating water intrusion through attic vents and strengthening soffits, refer to Technical 

Fact Sheet No. 7.5, “Minimizing Water Intrusion through Roof Vents in High-Wind Regions” in FEMA 

P-499, Homebuilder’s Guide to Coastal Construction (2010).

In Naples, the MAT observed two apartment buildings with metal soffit panel loss patterns similar 

to the single-family Florida Keys dwellings shown above. On the left side of Figure 4-24, metal fascia 

covering can still be seen hanging from the eaves near the corner of the hip-roofed building (built 

in 1983). Soffit panels remain in place toward the center of the building, but are missing closer 

to the corner. The right side image of Figure 4-24 shows the adjacent side of the building where 

fascia covering is completely gone along with most of the metal soffit panels. On a nearby Naples 

apartment building (built in 1980), metal soffit panels were lost below the front porch gable end 

outlooker rafters. As shown in Figure 4-25, no damage is apparent along the adjacent fascia of the 

building.

Figure 4-24: Apartment building with metal soffit panel loss (EWS = 104 mph; EDWS = 166 mph) (Naples)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-17

WIND-RELATED OBSERVATIONS

Figure 4-25: 

Metal soffit panel loss 

apartment gable end 

overhang (EWS = 104 mph; 

EDWS = 166 mph) (Naples)

4.2.3 Exterior Wall Coverings

The MAT observed exterior wall covering damage and loss resulting from Hurricane Irma winds. 

Aside from a few isolated instances of damage to wood siding, most of the exterior wall covering 

damage observed by the MAT was to vinyl siding. Damage to vinyl siding was widespread in the 

Florida Keys, but was also observed in Collier County. In most cases, the Irma MAT could not 

determine the design pressure rating of the failed vinyl siding. However, most of the observations 

indicated that the vinyl siding did not appear to be “high-wind” siding. The vinyl siding text box on 

the next page describes a failed vinyl siding installation that did not appear to be rated for South 

Florida application. The subsequent high wind-rated vinyl siding text box describes differences 

between vinyl siding rated for high-wind regions and standard vinyl siding.

For a few other sites, such as the Sugarloaf Key house shown in Figure 4-26, the MAT was able to 

record product identification numbers that allowed them to compare product-specific wind ratings 

to the FBC requirements. The house (built in 2014) lost siding along its back; based on the product 

identification shown in the inset, the MAT determined that the product had a negative design 

wind pressure rating of −74 psf (refer to Section 4.2.3.2). This vinyl siding product had a rolledover nail hem, which is characteristic of higher-rated vinyl siding. Using the Risk Category II design 

wind speed of 180 mph, Exposure Category D, an effective wind area of 10 square feet for Zone 5 

(corner zone), enclosed building classification, and an approximate mean roof height of 20 feet, the 

required design pressures (ASD) are +54 psf and −72 psf. Therefore, based on the required design 

pressure, the design pressure rating, and the estimated wind speeds at this site, the vinyl siding, if 

installed properly, should have resisted wind pressures sustained during Hurricane Irma. The State 

of Florida also requires building envelope products to be approved as described in the text box on 

the next page.
4-18 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

VINYL SIDING/SOFFIT FAILURE EXAMPLE

The MAT visited a subdivision of 24 elevated single-family dwellings in Goodland that sustained 

significant damage to vinyl siding and soffit assemblies on nearly all houses. Typical construction featured combinations of masonry and wood-framed exterior walls with a wood-framed roof. 

Maximum estimated 3-second gusts for Goodland during Irma were estimated to be 110 mph. The 

design wind speed for this site is approximately 169 mph, so vinyl siding and soffit assemblies rated 

for the site-specific conditions and installed per manufacturer’s instructions should not have failed. 

According to Collier County Property Appraisal information, the houses were all built between 2005 

and 2006, when the 2004 FBC was in effect statewide.

The top left photo shows typical siding damage in 

the area. The bottom left photo shows where siding 

was attached with staples to masonry wall furring 

strips at 16 inches on center. Additionally, there is 

no evidence of utility trim in the J-channel above, 

which would have been needed to secure the 

trimmed top course. Similarly, it does not appear 

that starter strips were used at the bottom of the 

first (lowest) course of siding, nor at the division 

between first and second floor siding sections. 

The photo on the right shows an aerial view of the 

neighborhood for perspective. 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-19

WIND-RELATED OBSERVATIONS

HIGH WIND-RATED VINYL SIDING VS. STANDARD VINYL SIDING

Much of the failed vinyl siding that the Irma MAT observed in Florida did not appear to be rated for 

high-wind regions. Technical Fact Sheet 5.3, “Siding Installation in High-Wind Regions,” in FEMA 

P-499, Homebuilders Guide to Coastal Construction (2010), includes guidance on vinyl siding installation. The left-side graphic below from Technical Fact Sheet 5.3 demonstrates the basic differences

between vinyl siding rated for high-wind regions and standard vinyl siding. The right-side image is

siding from one of the damaged houses in Goodland described in the previous text box. Note how

the detached siding has a standard (single) hem and locking area depicted in left image (rather than

the high-wind siding required by the FBC in this area).

Figure 4-26: 

Vinyl siding lost along the 

back of a house (EWS = 

113 mph; EDWS = 180 mph) 

(Sugarloaf Key)
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WIND-RELATED OBSERVATIONS

FLORIDA-PRODUCT APPROVAL

Rule 61G20-3 of the Florida Administrative Code applies to products and systems that compose the 

building envelope and structural frame. The rule requires the following products to have product approval for compliance with the structural requirements of the Florida Building Code:

•	 Panel walls (subcategories include soffits and siding)

•	 Exterior doors

•	 Roofing products

•	 Skylights

•	 Windows

•	 Shutters

•	 Structural components

•	 Impact protective systems

Products may be approved using either the optional statewide product approval system or local 

product approval. Regardless of the method used, products have to be evaluated for compliance 

(evaluation report, certification, test report, etc.), be validated for compliance with the evaluation, 

and approved by the Florida Building Commission. For additional information on product approval in the State of Florida, see Rule 61G20-3 of the Florida Administrative Code or the Building Code 

Information System at www.floridabuilding.org administered by the Florida Department of Business 

and Professional Regulation. A database of products approved using the statewide product approval 

system can be found under the “Product Approval” tab at www.floridabuilding.org.

The Marathon Key house (built in 2009) shown in Figure 4-27 lost siding across a significant portion 

of one gable end wall; based on the product identification shown in the inset, the MAT determined 

that the product had a design wind pressure rating of −55 psf (refer to Section 4.2.3.2). Using the 

Risk Category II design wind speed of 180 mph, Exposure Category D, an effective wind area of 10 

square feet for Zone 5 (corner zone), enclosed building classification, and approximate mean roof 

height of 25 feet, the required design pressures are +56 psf and −75 psf. While the design pressure 

rating is about 27 percent less than the required design pressure, considering the estimated wind 

speeds at this site, the siding should have resisted wind pressures experienced during Hurricane 

Irma if it was properly installed. There is no evidence of utility trim under the window, which left 

the siding vulnerable at that location.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-21

WIND-RELATED OBSERVATIONS

Figure 4-27: 

House that lost vinyl siding 

on its gable end wall (EWS = 

120 mph; EDWS = 180 mph) 

(Marathon Key)

4.2.3.1 Vinyl Siding Installation Issues

In addition to concerns about the use of vinyl siding with inadequate pressure ratings, the MAT 

observed several instances of vinyl siding wind damage on buildings that may have been due to 

installation issues. Figure 4-28 shows a Marathon Key duplex building (built 2017) with vinyl siding 

loss across the front and left exterior walls. The Vinyl Sinding Institute’s 2015 Vinyl Siding Installation 

Manual recommends that the head of the fastener not be driven tightly against the nail hem to allow 

for expansion.2 A clearance of 1/32 inch is recommended between the nail head and nail hem. 

The clearance shown in Figure 4-28 appears to exceed 1/32 inch. Further, vinyl siding loss above 

the front-facing wall above the front porch may have been initiated where a J-channel was installed 

instead of the manufacturer’s specified starter strip.

The houses in Figure 4-29 (built in 2000), Figure 4-30 (built in 1977), and Figure 4-31 (built in 

2000) show representative installation issues where vinyl siding failed. The house in Figure 4-29 was 

permitted to have its vinyl siding replaced in 2015, with work completed in 2016. The Little Torch 

Key house in Figure 4-31 was permitted to repair damage to its vinyl siding due to Hurricane Wilma 

in 2006, with the work completed the same year.

2 The Vinyl Siding Institute’s 2018 Vinyl Siding Installation Manual makes this same recommendation.
4-22 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

Figure 4-28: Duplex where vinyl siding above the front porch did not comply with manufacturer’s installation 

instructions (EWS = 120 mph; EDWS = 180 mph) (Marathon Key)

Figure 4-29:

House appeared to lack 

utility trim under the 

windows, as shown in the 

red outline (EWS = 120 

mph; EDWS = 180 mph) 

(Marathon Key)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-23

WIND-RELATED OBSERVATIONS

Figure 4-30:

House that lacked a proper 

starter strip, as shown in 

the red outline (EWS = 114 

mph; EDWS = 180 mph) 

(Little Torch Key)

Figure 4-31:

House with irregular 

fastener pattern and 

apparent lack of a proper 

starter strip (EWS = 114 

mph; EDWS = 180 mph) 

(Little Torch Key)

4.2.3.2 Vinyl Siding Design Pressure Ratings and the Pressure Equalization Factor

Vinyl siding is required to be certified and labeled as conforming to ASTM D 3679, Standard 

Specification for Rigid Poly(Vinyl Chloride) (PVC) Siding. The 6th Edition (2017) FBC refers to the 2011 

edition of ASTM D 3679, and the 5th Edition (2014) refers to the 2009 edition of ASTM D 3679. For 

determining the design wind pressure rating of vinyl siding, ASTM D 3679 permits test pressures to 

be adjusted to account for pressure equalization across the vinyl siding due to leakage paths (gaps). 

Pressure equalization refers to the reduction in net wind forces across cladding layers caused by 
4-24 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

external pressures being transferred to an interior air space. Pressure equalization of vinyl siding 

is accounted for by using a pressure equalization factor (PEF). ASTM D 3679 permits the PEF for 

vinyl siding to be taken as 0.36, which has the net effect of reducing the required test pressure to 36 

percent of the design pressure rating of the vinyl siding times a Factor of Safety of 1.5. To clarify, the 

applicable equation is shown below:

Pt = Dp x PEF x 1.5

Where:

Pt = test pressure

Dp = design pressure rating of vinyl siding

PEF = Pressure Equalization Factor, 0.36

1.5 = Factor of Safety

For example, if a vinyl siding product had a design pressure rating (Dp) of 60 psf, that product was 

tested to a pressure of 32.4 psf (60 psf x 0.36 x 1.5).

Recent research (refer to the Insurance Institute for Business & Home Safety report Wind Loads on 

Components of Multi-Layered Wall Systems with Air-Permeable Cladding [2012]) has indicated that the PEF 

for vinyl siding should be higher. As a result, the 2017 edition of ASTM D 3679 increases the PEF to 

0.5. Therefore, in the example above, the test pressure in ASTM D 3679-17 for a vinyl siding product 

with a design pressure rating (Dp) of 60 psf will be 45 psf. Debate continues about whether the PEF 

should be even higher than 0.5. 

4.2.4 Glazed Openings and Opening Protection Systems

All sites that the MAT visited are located within the FBC’s Wind-Borne Debris Region (WBDR) (see 

text box “FBC Wind-Borne Debris Region”). These sites have been included in the WBDR since 

the first edition of the FBC went into effect. The FBCR requires protection of all exterior glazed 

openings in the WBDR with products meeting the Large Missile Test of ASTM E 1886 and ASTM 

E 1996, Testing Application Standards (TAS) 201, 202, and 203 (HVHZ Test Protocols), AAMA 

506, or ANSI/DASMA 115 (garage doors). The FBCR also provides a prescriptive solution for wood 

structural panels to serve as opening protection with limitations (the prescriptive solution for wood 

structural panels is not permitted in the HVHZ). While there are several limitations when using 

wood structural panels as opening protection, key limitations include:

+ They must be a minimum of 7/16 inch thick

+ Their span is limited to 44 inches

+ Permanent corrosion-resistant attachment hardware must be provided, and anchors must be 

permanently installed on the building

The MAT observed the impact-resistant glazing and covering damage described in the following 

subsections.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-25

WIND-RELATED OBSERVATIONS

FBC WIND-BORNE DEBRIS REGION

Wind-Borne Debris Regions are defined in The following excerpt from the FBCR applies to 

Chapter 2 of the FBCR as follows: exterior glazed openings in the WBDR:

Wind-Borne Debris Region. Areas within R301.2.1.2 Protection of openings. 

hurricane‐prone regions located in accor- Exterior glazed openings in buildings located 

dance with one of the following: in windborne debris regions shall be protected from wind-borne debris. Glazed opening • Within 1 mile (1.61 km) of the coastal protection for windborne debris shall meet mean high water line where the ultimate the requirements of the Large Missile Test of design wind speed, Vult, is 130 mph (58 ASTM E1996 and ASTM E1886 as modified m/s) or greater. in Section 301.2.1.2.1, TAS 201, 202 and 203, 

• In areas where the ultimate design wind or AAMA 506, as applicable. Garage door 

speed, Vult, is 140 mph (63.6 m/s) or glazed opening protection for windborne 

greater; or Hawaii. debris shall meet the requirements of an ap‐

proved impact-resisting standard or ANSI/ See Figure 2-4 of this MAT report for the Wind- DASMA 115. Borne Debris Region for FBCR buildings.

4.2.4.1 Impact-Resistant Glazing

The MAT observed damage to at least three double-paned glazed openings along one side of the 

Ramrod Key house (built in 2017) shown in Figure 4-32. However, the damaged openings appear 

to have resisted penetration, because in each case the inner panes were intact. The MAT could not 

determine with certainty that the glazed openings in Figure 4-32 were impact-resistant products 

without closer product inspection and research. But given the date of construction and concurrent 

FBCR requirements, the openings were likely protected with impact-resistant glazing to comply with 

building code requirements. 

Figure 4-32:

Residence with two 

windows where the outer 

panes were broken (see 

red arrows) but the inner 

panes stayed intact (EWS = 

113 mph; EDWS = 180 mph) 

(Ramrod Key)
4-26 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

The MAT visited the Little Torch Key house shown in Figure 4-33 and Figure 4-34 (built in 1985) 

to observe extensive wind-borne debris damage. The dwelling was struck repeatedly by construction 

materials blown from a nearby structure that was destroyed during Hurricane Irma. Figure 4-33 

shows where the impact-resistant glazing did not prevent a wind-borne, 12-foot-long, 2x10 rafter 

from penetrating the interior of the house. This missile in particular is more massive than the D 

test missile (9-pound, 2x4 lumber) required by ASTM E1996. According to the homeowners, after 

penetrating the French door side light panel, the missile still had enough energy to reach and 

damage a television on the other side of the room. A second piece of wind-borne lumber penetrated 

the frame of an upper floor door unit on the same (east-facing) side of the house (see Figure 4-34).

Figure 4-33:

House damaged by windborne debris (EWS = 114 

mph; EDWS = 180 mph) 

(Little Torch Key)

Figure 4-34:

Wind-borne driven missile 

damaged second floor 

door at the same house as 

shown in Figure 4-33 (EWS 

= 114 mph; EDWS = 180 

mph) (Little Torch Key)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-27

WIND-RELATED OBSERVATIONS

4.2.4.2 Impact-Resistant Coverings 

In addition to damaged impact-resistant glazing, the MAT observed some damage to impactresistant covering systems. The shutter and shutter system frame on the Little Torch Key dwelling 

(built in 2008) shown in Figure 4-35 was significantly damaged when struck by wind-borne debris. 

Also, note the damage to the railing in the foreground of Figure 4-35. 

Figure 4-35:

House with impactresistant shutter system 

damaged by wind-borne 

debris; opening was 

covered at the time the 

MAT visited (EWS = 114 

mph; EDWS = 180 mph) 

(Little Torch Key)

Another example of damage to impact-resistant covering systems is shown in Figure 4-36, where 

a portion of the system’s frame supporting the left end of the corrugated metal shutter is missing 

(see yellow outline). Shutters were still in place on the elevated first floor of the Goodland residence 

(built in 2005), but the damaged frame (see right image of Figure 4-36) rendered the glazed 

opening beneath it vulnerable to impact, as the metal shutter peeled toward the right side support. 
4-28 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

Figure 4-36: House with corrugated metal shutters (EWS = 110 mph; EDWS = 169 mph) (Goodland)

4.2.5 Garage Doors

The MAT observed a few instances of garage door failure on older, pre-FBC dwellings in the wake 

of Hurricane Irma. The failure mode for each was generally buckling near the base and failure 

at the track, as shown in Figure 4-37 and Figure 4-38. Both single-car overhead garage doors on 

the Little Torch Key house (built in 1980) shown in Figure 4-37 were damaged, but the right side 

opening could not be assessed in its partially open position. The left side door appears to have been 

pulled away from the track (evidenced by the greatest deflection present at the base of the door) by 

outward-acting negative wind pressure. A similar example of a single-width overhead garage door 

that buckled and pulled away from its track at the base is shown in Figure 4-38 for a Duck Key 

house (built in 1985).

Figure 4-37: Damaged overhead garage doors (EWS = 114 mph; EDWS = 180 mph) (Little Torch Key)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-29

WIND-RELATED OBSERVATIONS

Figure 4-38: Damaged overhead garage door on a house (EWS = 111 mph; EDWS = 180 mph) (Duck Key)

4.3 Manufactured Housing Units 

The MAT observed MH units in Collier County and the Florida Keys. Although some examples of 

MH anchorage techniques used in the Florida Keys are included below, inland observations from 

Collier County are primarily discussed because many installations in the Florida Keys were destroyed 

by storm surge. In Collier County, many more MH units than site-built houses were destroyed by 

Hurricane Irma’s winds. Collier County building officials shared district-specific damage assessment 

information indicating that in three districts, 45 MH units were destroyed, while only three singlefamily dwellings and one multi-family dwelling were destroyed. Almost all destroyed units were 

inland of Irma’s storm surge and were therefore destroyed by wind effects.

Date built and/or date manufactured information was not as readily available for the MH units 

as it was for site-built dwellings, which made it difficult for the MAT to determine the applicable 

construction criteria for observed units. When MH units were included on property appraisal 

websites maintained by counties and municipalities, the date listed was the date that units were 

installed in the referenced location, and not the date they were constructed in the factory. The date 

of manufacture should be included on identification plates required by the Department of Housing 

and Urban Development (HUD) as of June 15, 1976. However, the only observed MH units with 

HUD identification plates were newly installed to replace units destroyed by Irma, so the age of 

damaged and destroyed MH units is largely unknown.3 Absent HUD tags could have been destroyed, 

removed, or located inside the MH units where the MAT did not have access. 

3 For the purposes of this report, the MH units presented in this section were likely built after June 15, 1976, and are therefore referred to as 

MH units and are not differentiated as “Early Code” MH units (built after June 15, 1976 but before July 13, 1994) or “New” MH units (built July 

13, 1994 to present). 
4-30 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

4.3.1 Anchoring

New MH units installed after Irma and observed by the MAT appeared to be anchored much more 

consistently than older installations. Figure 4-39 and Figure 4-40 show two examples of post-Irma 

anchorage. Note both units’ metal anchor straps are tight, aligned at the top and bottom, spaced 3 

feet or less on center, and attached to the base of the wall. One exception to post-Irma anchorage 

consistency is shown in Figure 4-41, where straps are misaligned from top to bottom.

Figure 4-39: 

Anchorage on a new MH 

unit installation (EWS = 

105 mph; EDWS = 164 

mph) (Collier County)

Figure 4-40: 

Consistent anchorage 

pattern observed on a new 

MH unit installation 

(EWS = 105 mph; EDWS = 

164 mph) (Collier County)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-31

WIND-RELATED OBSERVATIONS

Figure 4-41: 

New MH unit installation 

with misaligned anchor 

strap installation (red 

outline) was otherwise 

anchored consistently with 

other post-Irma examples

(EWS = 105 mph; EDWS = 

164 mph) (Collier County)

Aside from the newly installed units described above, the MAT observed significant variation across 

MH installations with respect to the spacing of anchors and where they were connected to the unit. 

Loose anchor straps were also commonplace. Without adequate tension, the anchor straps are 

ineffective at resisting the lateral and uplift effects of high wind.

 Figure 4-42 shows a unit in Big Coppitt Key that illustrates typical anchorage variations observed 

in older installations. The unit anchors are spaced at approximately 3 feet on center, but only every 

third strap is attached to the base of the exterior wall, and one of the anchors is not tight (see figure 

caption and inset). Another example from Marathon Key shows all straps spaced at approximately 

3 feet on center and attached to the exterior wall base, but with a visibly loose anchor strap (see 

Figure 4-43).

Figure 4-42: 

MH unit installation where 

only the first and fourth 

straps are attached to the 

exterior wall base (EWS = 

111 mph; EDWS = 180 mph) 

(Big Coppitt Key)
4-32 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

Figure 4-43: 

MH unit installation 

with straps spaced at 

approximately 3 feet on 

center and attached to the 

exterior wall base, but with 

loose anchor strap shown 

in red outline (EWS = 120 

mph; EDWS = 180 mph) 

(Marathon Key)

4.3.2 Other Observations

Carports, decks, porches, and awnings are often attached after the MH unit has been installed. 

Chapter 15C of the Florida Administrative Code requires that additions “shall be free-standing and 

self-supporting with only the flashing attached to the main unit unless the added unit has been 

designed to be married to the existing unit (15C-2.0081).”

As observed in the Hurricane Charley MAT report (FEMA, 2005: Section 7.4), and in FEMA 

Recovery Advisories 4 and 5 for the 2007 tornado outbreak in central Florida, “Understanding and 

Improving Performance of Older Manufactured Homes During High-Wind Events” (2007d), and 

“Understanding and Improving Performance of New Manufactured Homes During High-Wind 

Events” (2007c), respectively, wind damage to MH units is frequently initiated when improperly 

attached appurtenances are blown off or damaged. Specifically, when carports and covered 

porches—which are particularly vulnerable to wind loads—break away from the MH unit, they 

leave openings at failed connections in the remaining roof and/or wall that allow rain to enter the 

MH unit envelope. In some cases, damage progresses from the initial point of failure. The MAT 

observations confirm this progressive failure pattern occurred in Florida during Hurricane Irma. 

The following examples of MH unit damage initiated by improperly attached appurtenances were 

observed during the Hurricane Irma MAT site visits (before damage was cleared away) and are 

representative of many more failures. In the MH unit shown in Figure 4-44, loss of vinyl siding 

across the top and left end of the exterior wall was initiated by loss of the screened porch. The red 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 4-33

WIND-RELATED OBSERVATIONS

tag on the front-facing window of the Everglades City installation means that the damage resulted 

in condemnation by local officials. Furthermore, the unit appears to be half of a double-wide MH 

unit, as evidenced by the exposed wall section (inside yellow oval) where there is no sheathing and 

no insulation in the exposed stud bays. The lack of wood structural sheathing on the wall may have 

contributed to the loss of the vinyl siding. Figure 4-45 shows another example of Collier County 

MH unit damage initiated by an attached screened porch, where the top of a wall opened up along 

the entire length of the unit and the adjacent roof section peeled back. Figure 4-46 shows a unit 

from the same neighborhood where the top of a wall was stripped away by the (formerly) connected 

carport. This MH unit also received a red tag from local officials.)

Figure 4-44: 

This MH unit sustained 

exterior wall damage 

that was initiated by 

the loss of the attached 

screened porch (EWS = 115 

mph; EDWS = 164 mph) 

(Everglades City)

Figure 4-45: 

MH unit that was damaged 

when its screened porch 

was lost to high winds 

(EWS = 105 mph; EDWS = 

166 mph) (Collier County)
4-34 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

WIND-RELATED OBSERVATIONS

Figure 4-46:

MH unit where carport 

detached from the unit, 

opening the building 

envelope across the top of 

a wall (EWS = 105 mph; 

EDWS = 166 mph) 

(Collier County)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 5-1

5Recommendations and 

Conclusions

The conclusions and recommendations are intended to help 

reduce future damage and impacts from flood and wind events 

such as Hurricane Irma.

The conclusions and recommendations presented in this report are based on the MAT’s observations 

in the areas studied; evaluations of relevant codes, standards, and regulations; and meetings with 

local officials, facility representatives, design professionals, and contractors.

The recommendations are intended to assist the State of Florida, communities, design professionals, 

contractors, building officials, facility managers, floodplain administrators, regulators, emergency 

managers, building owners, academia, select industries and associations, local officials, and 

individuals in the reconstruction process, and to help reduce future damage and impacts from 

flood and wind events such as Hurricane Irma. The recommendations will also help FEMA assess 

the adequacy of building codes and standards as they relate to dry floodproofing and floodplain 

management requirements and determine whether changes are needed or additional guidance is 

required to reduce hurricane damage.
5-2 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

RECOMMENDATIONS AND CONCLUSIONS

Section 5.1 is a summary of the conclusions and recommendations based on the MAT’s observations. 

Section 5.2 discusses general conclusions and recommendations. Section 5.3 discusses conclusions 

and recommendations related to building codes, standards, and regulations. Section 5.4 includes 

flood-related building performance conclusions and recommendations. Section 5.5 includes windrelated building performance conclusions and recommendations. Section 5.6 provides conclusions 

and recommendations on FEMA Technical Publications and Guidance. Section 5.7 provides a 

summary of the conclusions and recommendations in a tabular format.

5.1 Overview of Conclusions and Recommendations

The recommendations are presented as guidance to the State of Florida and those who are involved 

with the design, construction, and maintenance of the built environment in the State. The entities 

involved in the reconstruction and mitigation efforts should consider these recommendations in 

conjunction with their existing priorities and resources when determining how they can or will be 

implemented. 

Overall, newer construction generally sustained much less damage than older construction, so the 

requirements incorporated in the FBC, along with floodplain management regulations, appear 

to be working as intended. The extent of flood damage to buildings varied with the depth of 

floodwater, the amount of energy in the water (waves, velocity), and the nature of building design 

and construction (old versus new, at-grade versus elevated, MH units/recreational vehicles versus 

site-built/modular). Although inundation alone was a significant source of damage, some of the 

more dramatic structural failures observed were a result of wave action and scour. Wind-related 

damage was observed for both pre- and post-FBC buildings. While structural damage observations 

were almost exclusively limited to pre-FBC residential buildings, envelope damage was commonly 

observed on both older and newer construction. This envelope damage allowed wind-driven rain to 

penetrate to the interior, resulting in costly damage. 

The MAT Conclusions and Recommendations are prioritized within each subsection as those that 

may be most important to implement by the State, community, or interested party. Specifically, 

recommendations of note from each section include:

Recommendation FL-1a (Section 5.2). FDEM should develop/modify training on the flood provisions 

in the FBC and local floodplain management ordinances.

Recommendation FL-4a (Section 5.3). Permitting agencies should evaluate permitting criteria and 

performance requirements for new or replacement bulkheads.

Recommendation FL-7 (Section 5.4). Local floodplain administrators, design professionals, and 

building owners should follow the guidance in FEMA’s Texas Recovery Advisory 1 (2018e) and 

Florida Recovery Advisory 1 (2018d).

Recommendation FL-9a (Section 5.5). Industry groups should investigate the causes for the 

widespread asphalt shingle roof covering loss that was observed by the MAT.

Recommendation FL-14a (Section 5.6). FEMA should complete Guidelines for Wind Vulnerability 

Assessments for Critical Facilities.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 5-3

RECOMMENDATIONS AND CONCLUSIONS

5.2 General Conclusions and Recommendations

Conclusion FL-1

Building codes and floodplain management requirements were inconsistently enforced. The 

MAT observed inconsistencies in local code enforcement, as well as noncompliance by builders, 

throughout the sites visited (e.g., improper load path and not requiring or using products that are 

on the approved and tested list). Some observed damage is associated with use of non-flood damageresistant materials. 

Recommendation FL-1a. FDEM should consider developing/modifying training on the flood 

provisions in the FBC and local floodplain management ordinances. FDEM, in conjunction 

with FFMA and the Building Officials Association of Florida (BOAF), should develop a 

webinar on the flood provisions in the FBC and local floodplain management ordinances, 

specifically about enclosures, with emphasis on the use of flood damage-resistant materials 

below the required floor elevation. This training should be for builders, developers, floodplain 

administrators, building officials, plan reviewers, and building inspectors.

Recommendation FL-1b. BOAF, FHBA, and other stakeholders should consider developing 

additional training and placing additional emphasis on building envelope components. 

BOAF, FHBA, and other stakeholders should consider developing additional training and 

placing additional emphasis on the use of appropriate building envelope products that have 

been designed or tested for high wind locations. This topic could be addressed in conjunction 

with continuing education courses on the building code.

Conclusion FL-2

Building officials expressed concerns about having adequate resources. Some building officials 

did not feel they had adequate resources to properly inspect damaged buildings for life-safety, 

conduct Substantial Damage determinations, verify Substantial Improvement projects, review 

permit applications for repairs, and enforce FBC requirements during the post-disaster recovery 

period when extensive numbers of work projects are proposed in a short time.

Recommendation FL-2. FDEM should continue to encourage pre-event evaluation of post-disaster 

needs and inform appropriate parties about assessing resources through the Statewide 

Mutual Aid Agreement (SMAA). FDEM should inform building officials and local officials 

responsible for floodplain management about accessing resources to aid recovery through the 

SMAA signed by all Florida counties, or the inter-state Emergency Aid Compact. Although 

the agreement may be accessed at any time, when events are declared major disasters, some 

costs of aid provided under the agreement may be eligible for reimbursement by FEMA. FDEM 

should encourage the BOAF and the Florida Floodplain Managers Association (FFMA) to 

develop strategies under their SMAA and FDEM to recruit professional assistance to support 

communities in need. FDEM should also consider training design professionals to assist 

with inspections. The Florida Post-Disaster Toolkit for Floodplain Administrators should be 

distributed to all communities. FDEM should also continue to encourage pre-event evaluation 

of post-disaster needs.
5-4 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

RECOMMENDATIONS AND CONCLUSIONS

Conclusion FL-3

The State and communities did not receive (or did not receive in a timely manner) data on 

buildings that appeared to have incurred Substantial Damage. When buildings appeared to have 

incurred Substantial Damage, the State and communities either did not receive requested data 

submitted by NFIP claims adjusters, or did not receive the information in a timely manner.

Recommendation FL-3. FEMA should develop an effective and timely means to deliver the 

Adjuster Preliminary Damage Assessment data. When NFIP claims adjusters identify claims 

that, based on available data, appear to have incurred Substantial Damage, the adjusters 

submit data using FEMA Form 086-0-20, Adjuster Preliminary Damage Assessment (2018a). The 

form indicates FEMA and communities can use the data to identify potentially Substantially 

Damaged buildings. FEMA P-758, Substantial Improvement/Substantial Damage Desk Reference

(2010e) (Section 7.4.1), describes using the data for screening purposes only, especially after 

flood events that damage large numbers of buildings. FEMA should develop an effective and 

timely means to deliver data submitted by NFIP claims adjusters to States and communities.

5.3 Building Codes, Standards, and Regulations

Conclusion FL-4

The MAT observed damaged buildings that illustrate the problems associated with siting buildings 

on erodible shorelines. The Florida DEP report (Hurricane Irma Post-Storm Beach Conditions and 

Coastal Impact in Florida [2018]) identified numerous examples of dune/bluff erosion and building 

damage in these areas. Foundation design in these areas is particularly challenging. The MAT also 

observed numerous instances of erosion and damage to buildings and many areas where erosion 

control structures (bulkheads, seawalls, etc.) failed on open coast and estuarine shorelines, in many 

cases under less than base flood conditions. Bulkheads and other erosion control structures may 

not offer the intended level of protection. 

Recommendation FL-4a. Permitting agencies should evaluate permitting criteria and performance 

requirements for new or replacement bulkheads. Permitting agencies (e.g., Florida DEP, 

Water Management Districts, local government) should review public materials, emphasize 

the importance of evaluating existing bulkheads before relying on them for protection, and 

encourage communities to avoid siting buildings close to bulkheads. Permitting criteria and 

performance requirements for new or replacement bulkheads should be evaluated with respect 

to design conditions, including the effects of saturated backfill, wave forces, overtopping, and 

erosion on both water and land sides.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 5-5

RECOMMENDATIONS AND CONCLUSIONS

Recommendation FL-4b. FEMA should review and update their event-based erosion methodology.

FEMA should review and update the methodology used to estimate dune and bluff erosion. 

FEMA should also improve existing siting and foundation design guidance for coastal dune 

and bluff areas in FEMA P-55, Coastal Construction Manual: Principles and Practices of Planning, 

Siting, Designing, Constructing, and Maintaining Residential Buildings in Coastal Areas (2011, 

4th Edition), FEMA P-499, Home Builder’s Guide to Coastal Construction (2010b), and other 

publications. In consultation with the Florida DEP and other coastal States, FEMA should 

evaluate siting criteria and consider recommending revisions to ASCE 24 Chapter 3 on how 

best to consider erosion in design and construction.

Conclusion FL-5

FDEM documented the successful completion of its multi-year CRS initiative. During the initiative, 

which extended into post-Irma recovery, FDEM visited and offered technical assistance to more than 

200 communities with emphasis on eligibility for the CRS.

Recommendation FL-5. FDEM should expand its technical assistance for CRS communities. 

FDEM should review activities undertaken by CRS communities and higher standards adopted 

in floodplain management ordinances by CRS communities to identify activities and standards 

not widely employed. Future technical assistance for CRS communities should focus on 

encouraging consideration of those activities and standards, such as performing stormwater 

master plan studies; establishing compensatory storage requirements; identifying BFEs in 

Approximate Zone A; conducting public outreach for design professionals, surveyors, and 

mappers; and adopting the construction industry Coastal A Zone requirements in the FBC.

Conclusion FL-6

Florida’s installation requirements for MH units do not reference the current edition of FEMA 85.

Florida’s installation requirements for MH units reference the 1985 edition of FEMA 85, Protecting 

Manufactured Homes from Floods and Other Hazards. The current edition, FEMA P-85, was published in 

2009 and includes updated guidance for installation to address resistance to both flood and wind 

conditions. The 2009 edition includes some pre-engineered foundation specifications that minimize 

the need for site-specific engineered solutions for many locations. 

Recommendation FL-6. The Florida Department of Highway Safety and Motor Vehicles should 

reference the most recent edition of FEMA P-85. The Florida Department of Highway 

Safety and Motor Vehicles should update Chapter 15C, Florida Statues (Manufactured home 

installation) to reference the most recent edition of FEMA P-85 (the 2009 edition, or “as revised 

by FEMA”) in Chapter 15C. The State agency should also consider incorporating additional 

wind- and flood-resistant construction provisions with particular emphasis on anchoring, 

as well as develop a training unit for manufactured home installers, with specific focus on 

requirements for wind resistance and installation in SFHAs. This training should be designed 

to satisfy continuing education requirements for manufactured home installers.
5-6 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

RECOMMENDATIONS AND CONCLUSIONS

5.4 Flood-Related Building Performance

Conclusion FL-7 

Dry floodproofing measures often failed under less than design flood conditions. The MAT visited 

approximately 25 dry floodproofed sites following Hurricane Irma and identified several lessons to 

be learned from dry floodproofing failures under less than design flood conditions. The MAT also 

identified best practices from successfully implemented dry floodproofing measures. 

Recommendation FL-7. Local floodplain administrators, design professionals, and building 

owners should follow the guidance in FEMA’s Texas Recovery Advisory 1 (2018e) and Florida 

Recovery Advisory 1 (2018d). Texas Recovery Advisory 1, Dry Floodproofing: Planning and 

Design Considerations (2018e), and Florida Recovery Advisory 1, Dry Floodproofing: Operational 

Considerations (2018d), have guidance related to dry floodproofing methods and procedures 

developed based on observations made during and after Hurricanes Irma and Harvey. The 

MAT observations illustrate that designing and implementing dry floodproofing for buildings 

is complicated. Therefore, guidance based on recent events should be incorporated into the 

design and implementation of new and existing dry floodproofing. Specific considerations 

from the Recovery Advisories include:

– Conduct a thorough vulnerability assessment, including a survey of all potential water 

entry points, as part of the design process.

– Incorporate freeboard into the design flood elevation based on the building use. 

– Treat flood barriers like fire wall assemblies—label them and minimize modifications and 

penetrations.

– Evaluate utility components and penetrations through walls and floors as potential water 

entry points.

– Install check valves in floor drain systems and require ejector systems with check valves/

backflow preventers for stormwater and sanitary sewers. 

– Provide waterstops at the seals in foundation walls and floor slabs where those spaces are 

intended to remain dry and are located below the design flood elevation. 

Conclusion FL-8

Dry floodproofed buildings where building managers had instilled a culture of preparedness 

sustained less damage than other dry floodproofed buildings. The scope and detail of operations, 

maintenance, and testing plans was an indicator of the dry floodproofing system performance.

Recommendation FL-8a. Facility managers should develop an emergency operations plan (EOP) for 

severe weather. An EOP that outlines how to prepare the building when severe weather events 

are expected should be developed by facility managers. Each dry floodproofed facility should 

have an EOP with action items or an implementation checklist based on a timeline keyed to 

official severe weather warnings and watches. ASCE 24 Chapter 6 contains requirements for 

and discussion of EOPs.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 5-7

RECOMMENDATIONS AND CONCLUSIONS

Recommendation FL-8b. Facility managers should routinely re-evaluate dry floodproofing designs 

and plans as required by codes and standards. After each deployment of a dry floodproofing 

system, including training exercises, the overall design of dry floodproofing systems and 

EOPs for severe weather should be revisited to resolve any deficiencies identified while systems 

were being tested, installed, or subjected to floodwater. ASCE 24 Chapter 6 requires periodic 

practice of installing shields as well as testing of sump pumps and other drainage measures.

Recommendation FL-8c. Facility managers should take reasonable measures to instill a culture 

of preparedness. Facility managers should conduct annual training exercises during which 

dry floodproofing measures are installed, taking note of the time to install each portion of 

the system and the total time to install the entire dry floodproofing system. The commentary 

in ASCE 24 indicates persons responsible for installing or implementing the measures must 

be familiar with the procedures and equipment. Therefore, training exercises should include 

building maintenance and engineering staff along with other building staff that may be needed 

to install dry floodproofing systems with little warning time. Maintenance of dry floodproofing 

system components should be conducted annually, as well as during training exercises and 

following deployment for a flood event. To ensure system functionality, periodic maintenance 

should include checking gaskets and seals, installation hardware and fasteners, and the 

condition of building elements to which dry floodproofing components will be attached. 

Consider creating a video recording of manual dry floodproofing installations, especially the 

complex steps, so the video can be referenced later if untrained staff are required to assist.

5.5 Wind-Related Building Performance

Conclusion FL-9

The MAT observed evidence of inadequate resistance to wind loads for roof coverings of 

residential buildings. In particular, the MAT observed widespread damage to asphalt roof coverings 

on post-FBC residential structures; the reason(s) for this damage was not determined by the MAT. 

Recommendation FL-9a. Industry groups should investigate the causes for the widespread asphalt 

shingle roof covering loss that was observed by the MAT. More research needs to be done 

by industry groups (e.g., manufacturers, insurances, builders) to explain why post-FBC 

asphalt shingle damage was observed to be widespread following a below design-level event 

and whether these failures were the result of design, installation, testing, inspection, or other 

issues. Appropriate mitigating actions should then be taken.

Recommendation FL-9b. Contractors and inspectors must ensure roof covering repairs and 

replacements are in conformance with FBC requirements. When more than 25 percent of 

the total roof area or roof section has to be repaired, provisions of the FBC must be met. 

Contractors and inspectors should ensure roof covering repairs and replacements meet FBC 

requirements. Refer to Florida Recovery Advisory 3, Mitigation Triggers for Roof Repair and 

Replacement in the 6th Edition (2017) Florida Building Code (2018f) for additional guidance. 
5-8 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

RECOMMENDATIONS AND CONCLUSIONS

Conclusion FL-10 

The MAT observed evidence of inadequate resistance to wind pressures and improper installation 

of soffits on residential buildings. Widespread loss of soffits was observed in residential construction, 

and wind-driven rain infiltrated some areas where soffits were displaced or lost. 

Recommendation FL-10a. Designers, contractors, and inspectors should place more emphasis 

on proper soffit installation to limit wind-driven rain. Proper soffit installation should be 

emphasized by designers, contractors, and inspectors in order to limit wind-driven rain from 

entering building envelopes and damaging building interiors. Florida Recovery Advisory 2, 

Soffit Installation in Florida (2018h), provides soffit installation guidance and resources to meet 

or exceed minimum provisions of the FBC. 

Recommendation FL-10b. The FBC should require soffit inspections. Soffit inspections will help to 

ensure compliant products are used and the soffit is securely attached.

Conclusion FL-11

The MAT observed evidence of inadequate resistance to wind pressures for certain wall coverings 

of residential buildings. In particular, failure of vinyl siding on post-FBC residential structures was 

widespread. Instances of improper installation and concerns about appropriate design pressure 

ratings are addressed in Chapter 4 and were probable factors in the damage observed.

Recommendation FL-11a. Vinyl siding manufacturers, insurance organizations, and other 

stakeholders should continue investigations of the appropriate PEF for vinyl siding. 

The MAT’s observations of the amount of damage to vinyl siding and its unique sensitivity 

to proper installation suggests vinyl siding manufacturers, insurance organizations, and 

other stakeholders should continue investigations of the appropriate PEF for vinyl siding. 

Considering that maximum peak gusts in the Florida Keys were approximately 120 mph (well 

below the design wind speed), better performance would have been expected. 

Recommendation FL-11b. The FBC should require wall cladding inspections. Most MAT-observed 

wall cladding failures demonstrated one or more examples of non-compliant installation, 

which can be mitigated through field inspections. Common examples of wall cladding failures 

for vinyl siding include missing utility trim and starter strips. 

Conclusion FL-12

The MAT observed evidence of wind-borne debris, but very few instances of glazed openings 

being breached. ASCE 7-required protection of windows and glazed doors in the wind-borne debris 

region appears to have been widely applied. However, the few instances of observed damage to 

protected glazed openings occurred in areas where estimated wind speeds during Hurricane Irma 

were well below the 130 mph wind-borne debris trigger for which ASCE 7 requires glazed opening 

protection. This suggests that wind-borne debris was generated at wind speeds well below the 130 

mph trigger. 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 5-9

RECOMMENDATIONS AND CONCLUSIONS

Recommendation FL-12a. Industry groups and/or academia should study debris generation and 

strikes to protective systems during hurricanes to determine whether the wind speed triggers 

for the ASCE 7 wind-borne debris region are appropriate. Industry groups and/or academia 

should study debris generation and associated debris strikes to protective systems from the 

2017 hurricane, as well as for future storms, to determine whether the current wind speed 

triggers for the wind-borne debris region as defined in ASCE 7 are appropriate. Data collected 

and analyzed during the study can be used to make recommendations on ASCE 7-required 

protection of windows and glazed doors. 

Recommendation FL-12b. Building owners outside the wind-borne debris region should consider 

protecting the glazed openings on their buildings. Although not required by codes and 

standards, owners of buildings in the hurricane-prone region should consider protecting 

glazed window systems and doors with rated opening protection systems (i.e., storm shutters) 

or retrofitting the building with impact-resistant glazing when located anywhere in the 

hurricane-prone region.

Conclusion FL-13

Failures of appurtenance attachments to MH units increase the units’ vulnerability to wind 

and rain damage. Wind damage to MH units is frequently initiated when improperly attached 

appurtenances (such as carports and screened porches) are blown off or damaged leaving openings 

at failed connections that allow rain to enter the MH unit envelope. In some cases, damage 

progresses from the initial point of failure. This damage increases the unit’s vulnerability to wind 

and rain damage.

Recommendation FL-13. As a best practice, MH appurtenances should be built as stand-alone units 

without structural connection to the MH unit. If the appurtenance is not free-standing and 

is connected to the manufactured home for structural support, plans should be prepared that 

clearly detail the connection between the unit and the structure being attached. The design 

and construction should be approved, permitted, and inspected by building officials.

5.6 FEMA Technical Publications and Guidance

Conclusion FL-14

Select FEMA Building Science technical guidance publications are becoming increasingly 

incongruent with current building codes and do not include lessons learned from recent MATs. 

The Building Science Branch at FEMA Headquarters develops and maintains over 200 publications 

and resources that provide technical guidance on how to assess risk; identify vulnerabilities; better 

understand the NFIP and the regulatory environment with respect to building codes and standards; 

and provide best practices and mitigation measures that can be taken to reduce vulnerabilities 

to flood, wind, and seismic hazards. Some of the FEMA Building Science technical guidance 

publications do not reflect advanced requirements in current building codes nor do they include 

new lessons learned from recent MAT reports.
5-10 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

RECOMMENDATIONS AND CONCLUSIONS

The 2017 hurricane season brought landfalling hurricanes on the island territories and the 

continental United States. There are many valuable and important damage observations and lessons 

learned from this and other events, and the observed damage might have been avoided if the 

guidance from these documents had been incorporated at different building locations. However, 

while the approaches and theories in these publications are still accurate, many of the building 

codes have been updated in the last 8 to 10 years and may impact the current approaches outlined 

in these documents.

Recommendation FL-14a. FEMA should complete Guidelines for Wind Vulnerability Assessments for 

Critical Facilities. FEMA’s Building Science Branch has been developing guidance to assess 

wind vulnerabilities of critical facilities. FEMA should include lessons learned from the 2017 

hurricane season in finishing this publication, which would greatly benefit many stakeholders 

in the U.S. 

Recommendation FL-14b. FEMA should update select FEMA Building Science publications that 

affect coastal construction. The FEMA Building Science Branch should consider updating 

or producing a supplement for its key hurricane technical guidance publications to include 

lessons learned from the 2017 hurricane season and to reflect updates to building codes since 

the publications’ latest releases. These publications might include, but are not necessarily 

limited to, the following:

– FEMA P-55, Coastal Construction Manual (2011)

– FEMA P-499, Home Builder’s Guide to Coastal Construction (2010d)

– FEMA P-762, Local Officials Guide for Coastal Construction (2009b)

– FEMA P-804, Wind Retrofit Guide for Residential Buildings (2010f)

Recommendation FL-14c. FEMA should update the FEMA Risk Management Series guidance 

publications for natural hazards. The FEMA Building Science Branch, working with other 

FEMA and DHS entities, should consider updating or producing a supplement to select 

technical documents from the FEMA Natural Hazard Risk Management Series to include 

lessons learned from the 2017 hurricane season and to reflect updates to building codes since 

the publications’ latest releases. These publications might include, but are not limited to, the 

following:

– FEMA P-424, Design Guide for Improving School Safety in Earthquakes, Floods, and High Winds

(2010a)

– FEMA 543, Design Guide for Improving Critical Facility Safety from Flooding and High Winds

(2007a)

– FEMA 577, Design Guide for Improving Hospital Safety in Earthquakes, Floods, and High Winds: 

Providing Protection to People and Buildings (2007b)
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 5-11

RECOMMENDATIONS AND CONCLUSIONS

Conclusion FL-15 

Many communities have difficulty implementing the Substantial Improvement/Substantial 

Damage requirements, especially after major disasters. Many buildings damaged by flooding 

were designed and built before communities joined the NFIP and began regulating development 

in SFHAs. Enforcing the NFIP and FBC requirements to bring Substantially Improved and 

Substantially Damaged buildings into compliance continues to be one of the more difficult 

challenges for floodplain administrators and building officials. 

Recommendation FL-15a. FEMA should update FEMA P-758; at the same time, FEMA 213 should be 

updated to be consistent with the updated FEMA P-758. FEMA P-758, Substantial Improvement/

Substantial Damage Desk Reference (2010e) should be updated. Updates should include lessons 

learned, and recommended guidance and clairifcations since it was published in 2010. At the 

same time, FEMA 213, Answers to Questions about Substantially Improved/Substantially Damaged 

Buildings (2018b) should be updated to be consistent with the updated FEMA P-758. Outreach 

material should be developed as part of the publication updates. 

Recommendation FL-15b. FEMA should consider expanding existing training materials related 

to Substantial Improvement/Substantial Damage. FEMA should consider developing a 

webinar format training for distribution to NFIP State Coordinators and other entities related 

to Substantial Improvement/Substantial Damage. The materials should incorporate lessons 

learned after Hurricane Irma and other recent flood events and should include a unit focused 

on the local official’s role in helping insured property owners satisfy requirements to qualify 

for Increased Cost of Compliance claims and in issuing permits for mitigation measures 

eligible for use of those claim payments.

Conclusion FL-16 

Future dry floodproofing design and construction can benefit from observed failures and 

successes. The MAT visited about 25 dry floodproofed sites following Hurricane Irma and observed 

several lessons learned from dry floodproofing failures under less than design flood conditions, as 

well as best practices from successes.

Recommendation FL-16a. FEMA should update dry floodproofing guidance. Based on the varying 

performance of dry floodproofing measures observed, FEMA should revise existing dry 

floodproofing guidance to include data and observations from recent events. In particular, 

FEMA Technical Bulletin 3, Non-Residential Floodproofing—Requirements and Certification (1993), 

should be updated to improve guidance on planning, design and construction, and emergency 

operations, as well as maintenance planning requirements. Specific points of emphasis include:

– For new construction, recommend using ACI 350 for designing concrete that will be 

constructed below the required dry floodproofing elevation (ACI 350 concrete design 

reduces the crack width in concrete and increases the fineness of the concrete matrix to 

reduce concrete permeability rates).
5-12 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

RECOMMENDATIONS AND CONCLUSIONS

– Consider limiting the amount of openings below the required dry floodproofing 

elevation, i.e., the portion of the building envelope that is not permanently substantially 

impermeable. As a result, the amount of temporary protective measures would be limited 

to the length of the perimeter required for egress (pedestrian and vehicular). 

FEMA should also consider updating FEMA P-936, Floodproofing for Non-Residential Buildings

(2013a), with relevant lessons learned from the 2017 hurricane season as well.

Recommendation FL-16b. FEMA should evaluate existing dry floodproofing guidance and postflood investigations to develop a recommendation for inclusion in ASCE 24. FEMA should 

review recommendations, fact sheets, and recovery advisories related to dry floodproofing 

included in other MAT reports to develop a comprehensive recommendation for dry 

floodproofing design, limitations, testing, and maintenance and operations requirements for 

consideration by the ASCE 24 committee charged with revising Chapter 6, “Dry Floodproofing 

and Wet Floodproofing.”

5.7 Summary of Conclusions and Recommendations

Table 5-1 is a matrix listing the conclusions and recommendations cross-referenced to the sections 

of the report that describe the supporting observations. The recommendations provided in the 

table have also been cross-referenced to Recovery Support Functions (RSFs) supported by FEMA 

through the National Disaster Recovery Framework (NDRF). FEMA developed the RSFs with the 

objective of facilitating the identification, coordination, and delivery of Federal assistance needed 

to supplement recovery resources and efforts by local, State, tribal, and territorial governments, 

as well as private and nonprofit sectors. The MAT has identified RSFs for the recommendations 

provided in this report to assist Florida with accelerating the process of recovery, redevelopment, 

and revitalization. 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 5-13

RECOMMENDATIONS AND CONCLUSIONS

NATIONAL DISASTER RECOVERY FRAMEWORK AND RECOVERY SUPPORT FUNCTIONS

FEMA has developed the NDRF to create a 

common platform and forum for how the whole 

community builds, sustains, and coordinates delivery of recovery capabilities. FEMA guidance 

states: 

Resilient and sustainable recovery encompasses more than the restoration of a 

community’s physical structures to pre-disaster conditions. The primary value of the 

NDRF is its emphasis on preparing for recovery in advance of disaster. The ability of 

a community to accelerate the recovery process begins with its efforts in pre-disaster 

preparedness, including coordinating with 

whole community partners, mitigating risks, 

incorporating continuity planning, identifying 

resources, and developing capacity to effectively manage the recovery process, and 

through collaborative and inclusive planning 

processes. Collaboration across the whole 

community provides an opportunity to integrate mitigation, resilience, and sustainability 

into the community’s short- and long-term recovery goals. 

The RSFs compose the coordinating structure for 

key functional areas of assistance in the NDRF. 

Their purpose is to support local governments by 

facilitating problem solving, improving access to 

resources and by fostering coordination among 

State and Federal agencies, nongovernmental 

partners, and stakeholders. 

The list of RSFs and the leading coordinating 

agencies is presented below (and available on line 

at www.fema.gov/recovery-support-functions): 

•	 Community Planning and Capacity Building 

(CPCB) RSF (U.S. Department of Homeland 

Security/FEMA) 

•	 Economic RSF (U.S. Department of 

Commerce) 

•	 Health and Social Services RSF (U.S. 

Department of Health and Human Services) 

•	 Housing RSF (U.S. Department of Housing 

and Urban Development) 

•	 Infrastructure Systems RSF (U.S. Army Corps 

of Engineers)

•	 Natural and Cultural RSF (U.S. Department of 

the Interior)
5-14 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

RECOMMENDATIONS AND CONCLUSIONS

Table 5-1: Summary of Conclusions and Recommendations

Observations Conclusions Recommendations

Recovery Support 

Function

General 

MAT Field 

Observation

FL-1

Building codes and 

floodplain management 

requirements were 

inconsistently enforced.

FL-1a. FDEM should develop/modify 

training on the flood provisions in the 

FBC and local floodplain management 

ordinances.

CPCB, Economic 

FL-1b. BOAF, FHBA, and other stakeholders 

should consider developing additional 

training and placing additional emphasis on 

building envelope components.

CPCB, Economic

FL-2

Building officials 

expressed concerns 

about having adequate 

resources.

FL-2. FDEM should continue to encourage 

pre-event evaluation of post-disaster 

needs and inform appropriate parties about 

assessing resources through the SMAA. 

CPCB, 

Economic, 

Housing

FL-3

The State and 

communities did not 

receive (or did not receive 

in a timely manner) 

data on buildings that 

appeared to have 

incurred Substantial 

Damage.

FL-3. FEMA should develop an effective 

and timely means to deliver the Adjuster 

Preliminary Damage Assessment data.

CPCB, 

Economic, 

Housing

Chapter 3 

(Section 3.1)

FL-4

The MAT observed 

damaged buildings that 

illustrate the problems 

associated with siting 

buildings on erodible 

shorelines.

FL-4a. Permitting agencies should evaluate 

permitting criteria and performance 

requirements for new or replacement 

bulkheads.

CPCB, 

Economic, 

Housing, 

Infrastructure

FL-4b. FEMA should review and update 

their event-based erosion methodology.

CPCB, 

Economic, 

Housing, 

Infrastructure

Chapter 2

(Section 2.3) 

FL-5

FDEM documented the 

successful completion 

of its multi-year CRS 

initiative.

FL-5. FDEM should expand its technical 

assistance for CRS communities.

CPCB, 

Economic, 

Housing

Chapter 2

(Section 2.4) and 

Chapter 4 

(Section 4.3)

FL-6

Florida’s installation 

requirements for MH 

units do not reference 

the current edition of 

FEMA 85.

FL-6. The Florida Department of Highway 

Safety and Motor Vehicles should reference 

the most recent edition of FEMA P-85.

CPCB, 

Economic, 

Housing
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT 5-15

RECOMMENDATIONS AND CONCLUSIONS

Table 5-1: Summary of Conclusions and Recommendations (continued)

Observations Conclusions Recommendations

Recovery Support 

Function

Chapter 3 

(Section 3.2)

FL-7

Dry floodproofing 

measures often failed 

under less than design 

flood conditions.

FL-7. Local floodplain administrators, 

design professionals, and building owners 

should follow the guidance in FEMA’s Texas 

Recovery Advisory 1 (2018e) and Florida 

Recovery Advisory 1 (2018d).

CPCB, Economic

FL-8

Dry floodproofed 

buildings where building 

managers had instilled a 

culture of preparedness 

sustained less 

damage than other dry 

floodproofed buildings.

FL-8a. Facility managers should develop an 

EOP for severe weather.

CPCB, Health 

and Social 

Services, 

Economic 

FL-8b. Facility managers should routinely 

re-evaluate dry floodproofing designs and 

plans as required by codes and standards.

CPCB, Health 

and Social 

Services, 

Economic

FL-8c. Facility managers should take 

reasonable measures to instill a culture of 

preparedness.

CPCB, Health 

and Social 

Services, 

Economic

Chapter 4 

(Section 4.2.1)

FL-9

The MAT observed 

evidence of inadequate 

resistance to wind loads 

for roof coverings of 

residential buildings.

FL-9a. Industry groups should investigate 

the causes for the widespread asphalt 

shingle roof covering loss that was 

observed by the MAT.

Housing, 

Economic

FL-9b. Contractors and inspectors 

must ensure roof covering repairs and 

replacements are in conformance with FBC 

requirements.

Housing, Health 

and Social 

Services, 

Economic

Chapter 4 

(Section 4.2.2)

FL-10

The MAT observed 

evidence of inadequate 

resistance to wind 

pressures and improper 

installation of soffits on 

residential buildings.

FL-10a. Designers, contractors, and 

inspectors should place more emphasis on 

proper soffit installation to limit wind-driven 

rain.

Housing, CPCB, 

Economic

FL-10b. The FBC should require soffit 

inspections.

Housing, CPCB, 

Economic

Chapter 4 

(Section 4.2.3)

FL-11

The MAT observed 

evidence of inadequate 

resistance to wind 

pressures for certain wall 

coverings of residential 

buildings.

FL-11a. Vinyl siding manufacturers, 

insurance organizations, and other 

stakeholders should continue investigations 

of the appropriate PEF for vinyl siding.

Housing, 

Economic

FL-11b. The FBC should require wall 

cladding inspections.

Housing, CPCB, 

Economic
5-16 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

RECOMMENDATIONS AND CONCLUSIONS

Table 5-1: Summary of Conclusions and Recommendations (concluded)

Observations Conclusions Recommendations

Recovery Support 

Function

Chapter 4 

(Section 4.2.4)

FL-12

The MAT observed 

evidence of windborne debris, but 

very few instances of 

glazed openings being 

breached.

FL-12a. Industry groups and/or academia 

should study debris generation and strikes 

to protective systems during hurricanes to 

determine whether the wind speed triggers 

for the ASCE 7 wind-borne debris region are 

appropriate.

Housing, CPCB, 

Economic

FL-12b. Building owners outside the 

wind-borne debris region should consider 

protecting the glazed openings on their 

buildings.

Housing, CPCB, 

Economic

Chapter 4 

(Section 4.3)

FL-13

Failures of appurtenance 

attachments to MH 

units increase the units’ 

vulnerability to wind and 

rain damage. 

FL-13. As a best practice, MH 

appurtenances should be built as standalone units without structural connection to 

the MH unit.

Housing, 

Economic

General 

MAT Field 

Observation

FL-14

Select FEMA Building 

Science technical 

guidance publications are 

becoming increasingly 

incongruent with current 

building codes and do 

not include lessons 

learned from recent 

MATs.

FL-14a. FEMA should complete Guidelines 

for Wind Vulnerability Assessments for 

Critical Facilities.

CPCB, Health 

and Social 

Services, 

Economic

FL-14b. FEMA should update select FEMA 

Building Science publications that affect 

coastal construction.

Housing, CPCB, 

Economic

FL-14c. FEMA should update the FEMA Risk 

Management Series guidance publications 

for natural hazards.

Housing, CPCB, 

Health and 

Social Services, 

Economic

FL-15

Many communities have 

difficulty implementing 

the Substantial 

Improvement/Substantial 

Damage requirements, 

especially after major 

disasters.

FL-15a. FEMA should update FEMA P-758; 

at the same time, FEMA 213 should be 

updated to be consistent with the updated 

FEMA P-758. 

Housing, CPCB, 

Economic

General 

MAT Field 

Observation

FL-15b. FEMA should consider expanding 

existing training materials related to 

Substantial Improvement/Substantial 

Damage.

CPCB, Economic

Chapter 3 

(Section 3.2)

FL-16

Future dry floodproofing 

design and construction 

can benefit from 

observed failures and 

successes. 

FL-16a. FEMA should update dry 

floodproofing guidance.

CPCB, Economic

FL-16b. FEMA should evaluate existing 

dry floodproofing guidance and post-flood 

investigations to develop a recommendation 

for inclusion in ASCE 24.

CPCB, Economic

ASCE = American Society of Civil Engineers

BOAF = Building Officials Association of Florida 

CPCB = Community Planning and Capacity Building

CRS = Community Rating System (NFIP)

EOP = emergency operations plan

FBC = Florida Building Code

FDEM = Florida Division of Emergency Management

FEMA = Federal Emergency Management Agency

FHBA = Florida Home Builders Association

MAT = Mitigation Assessment Team

MH = manufactured housing

PEF = pressure equalization factor

SMAA = Statewide Mutual Aid Agreement
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT A-1

A

Appendix A: 

Acknowledgments

The Federal Emergency Management Agency (FEMA) would like to acknowledge the contributions 

of the following persons to the Mitigation Assessment Team study of the areas affected by Hurricane 

Irma in Florida: 

Stuart Adams, EI, CFM

Stantec

James Ahling

Guest Services

Martha D. Akins, R.I.D.

Vizcaya Museum and Gardens

Miles Anderson

Florida Division of Emergency Management

Robert Azimi

FM Approvals 

Daniel Bass, RA, CFM

FEMA Headquarters

Randy Behm, PE, CFM

U.S. Army Corps of Engineers

Christopher Bender, PhD, PE, D.CE

Taylor Engineering

Charles Benson, RA

Charles H. Benson & Associates, 

Architects, P.A.

Chad Berginnis, CFM

Association of State Floodplain Managers 

Blossom’s Cajun Kitchen

John Bourdeau, Jr., CFM, PMP

FEMA Region VI

Dana Bres, PE

U.S. Department of Housing and Urban 

Development

Lindsay Brugger, AIA, SEED

American Institute of Architects

Haven Burkee, RA, NCARB

Bender & Associates Architects

Karl W. Bursa, AICP, CFM

Village of Islamorada
A-2 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

ACKNOWLEDGMENTS

Christa Carrera, CFM

City of Naples

Paul Carroll, PE, PMP

AECOM

Walter Cashwell

Keys Energy Services

Diana Castro, PE, CFM

AECOM

Caroline Cilek, AICP, CFM

Collier County

Anne Cope, PhD, PE

Insurance Institute for Business & 

Home Safety

Stephanie Costa, LCAM

BrickellHouse

Daniel E. Deegan, CFM

AECOM

Kelli DeFedericis, CFM

City of Marco Island

Emily Dhingra, PE, CFM

AECOM

Matthew Dobson

Vinyl Siding Institute 

Tara Dodson

St. Johns County

Patrick Doty, CFM

St. Johns County

Siavash Farvardin

Insurance Institute for Business & Home 

Safety

FEMA Modeling Working Group

Gina Filippone, CFM

AECOM

Derek Fellows, PE

FEMA Region IV

Michael Fischer

Asphalt Roofing Manufacturers Association

Florida Division of State Parks (Bahia Honda, 

Long Key, Lovers Key, Tallahassee)

Scott Fraser, CFM

City of Key West

Jaime Gascon, PE

Miami-Dade County

Bret Gates

FEMA Headquarters

Laura Ghorbi, PE, CFM

AECOM

Nathan Gould, PhD, PE, SE

ABS Consulting

Leslie Chapman-Henderson

Federal Alliance for Safe Homes, Inc.

Elena Drei-Horgan, PhD, CFM

AECOM

John Ingargiola, EI, CFM, CBO

FEMA Headquarters

International Code Council

Mohsen Jarahpour, CFM

City of Miami Beach

Tony Jenkins

Biltmore Construction Company, Inc.

Cheryl Johnson, PE, CFM

AECOM 

Dave Johnston

Vinyl Siding Institute

Jena’I Jordan

FEMA Headquarters

Bruce H. Koniver

Koniver Stern Group

Erin Koss

PGT Custom Windows + Doors
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT A-3

ACKNOWLEDGMENTS

Edward Laatsch, PE

FEMA Headquarters

Lee County Parks and Recreation

Marc Levitan, PhD

National Institute of Standards and 

Technology

Paul Loughran

Plaza Construction

Philip Line, PE

American Wood Council

David Low, PE

DK Low & Associates

Tim McQuillen

Asphalt Roofing Manufacturers Association

Mo Madani, CBO

Florida Department of Business and 

Professional Regulation

Therese McAllister, PhD, PE

National Institute of Standards and 

Technology

Sean McNabb

FEMA JFO

Rachel Minnery, FAIA

American Institute of Architects

Judith Mitrani-Reiser, PhD

National Institute of Standards and 

Technology

Tim Montgomery, PE

CDM Smith

National Park Service (Everglades 

National Park)

Brian O’Connor, PE

CDM Smith

Frankie Pettit, GISP

AECOM

David O. Prevatt, PhD, PE

University of Florida

Adam Reeder, PE, CFM

CDM Smith

Michael Rimoldi, MPA, CBO, CFM

Federal Alliance for Safe Homes, Inc.

John Ritchey

FEMA Headquarters

Victor Rodriguez

Vizcaya Museum and Gardens

David B. Roueche, PhD

Auburn University

Patrick Sacbibit, PE, CFM

FEMA Headquarters

Ana M. Salquiero, PE

City of Miami Beach

Charlie Sanner

FEMA Headquarters

Kelsey Schill

CDM Smith

James Schock, PE, CBO, CFM

St. Johns County

Michael Schultz, GISP, CFM

CDM Smith

Pataya Scott, EIT

FEMA Headquarters

Vince Seijas, B.S., CFM

Miami-Dade County 

Dotty Smallwood

Everglades City

Terry Smallwood

Everglades City 

Christopher Smith

FEMA Headquarters 

Thomas Smith, AIA, RRC, F.SEI

TLSmith Consulting, Inc.

Lyle B. Stern

Koniver Stern Group
A-4 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

ACKNOWLEDGMENTS

Terri Sullivan

Village of Islamorada

Scott Tezak, PE, BSCP

Atkins

Casey Thayer, CGMP

Outreach Process Partners

Valentia Mediterranean Cuisine

Peter Vickery, PhD, PE, F.SEI, F.ASCE

Applied Research Associates

Jonathan Westcott, PE

FEMA HQ

Howard White, CBO

St. Johns County

Jordan Williams, CFM

CDM Smith 

John Woodson

City of Marathon

Mark Zehnal

Insurance Institute for Business & 

Home Safety

Casey Zuzak

GISP, FEMA Region VIII
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT B-1

B

ACI (American Concrete Institute). 2006. Code Requirements for Environmental Engineering Concrete 

Structures, ACI 350.

AISI (American Iron and Steel Institute). 2012. Standard for Cold-Formed Steel Framing—Prescriptive 

Method for One- and Two-Family Dwellings, 2007, with Supplement 3, dated 2012, AISI S230.

American Wood Council. 2012. Wood-Frame Construction Manual for One- and Two-Family Dwellings 

(AWC WFCM).

Applied Research Associates, Inc. (ARA)/FEMA Geospatial Working Group, 2017. “Gusts 

Experienced During Hurricane Irma” (personal communication).

ASCE (American Society of Civil Engineers). 2010. Minimum Design Loads for Buildings and Other 

Structures, ASCE 7-10.

ASCE. 2014. Flood Resistant Design and Construction, ASCE 24-14.

CERA (Coastal Emergency Risks Assessment). 2018. “ADCIRC Storm Surge Guidance for 

Emergency Managers and Decision Makers” (website). Last accessed December 2018, 

http://nc-cera.renci.org/.

FEMA (Federal Emergency Management Agency). n.d. Guidelines for Wind Vulnerability Assessments of 

Critical Facilities, FEMA P-(unnumbered). Not yet completed.

FEMA. 1985. Manufactured Home Installation in Flood Hazard Areas, FEMA 85.

FEMA. 1993. Non-Residential Floodproofing—Requirements and Certification, Technical Bulletin 3. 

https://www.fema.gov/media-library/assets/documents/3473. 

Appendix B: References
B-2 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

REFERENCES

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Performance Observations, Recommendations, and Technical Guidance, FEMA 549.

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FEMA. 2007a. Design Guide for Improving Critical Facility Safety from Flooding and High Winds, FEMA 

543. https://www.fema.gov/media-library/assets/documents/8811. 

FEMA. 2007b. Design Guide for Improving Hospital Safety in Earthquakes, Floods, and High Winds: 

Providing Protection to People and Buildings, FEMA 577.

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FEMA. 2007c. Understanding and Improving Performance of New Manufactured Homes During High-Wind 

Events, 2007 Tornadoes in Florida Recovery Advisory 5. 

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FEMA. 2007d. Understanding and Improving Performance of Older Manufactured Homes During HighWind Events, 2007 Tornadoes in Florida Recovery Advisory 4. 

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FEMA. 2009a. Hurricane Ike in Texas and Louisiana: Mitigation Assessment Team Report, Building 

Performance Observations, Recommendations, and Technical Guidance, FEMA P-757. 

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FEMA. 2009b. Local Officials Guide for Coastal Construction, FEMA P-762. 

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FEMA. 2009c. Protecting Manufactured Homes from Floods and Other Hazards, FEMA P-85. 

https://www.fema.gov/media-library/assets/documents/2574v.

FEMA. 2009d. Tornado Protection: Selecting Refuge Area in Buildings, FEMA P-431. Second Edition.

https://www.fema.gov/media-library/assets/documents/2246.

FEMA. 2010a. Design Guide for Improving School Safety in Earthquakes, Floods, and High Winds, FEMA 

P-424. https://www.fema.gov/media-library/assets/documents/5264. 

FEMA. 2010b. Home Builder’s Guide to Coastal Construction, FEMA P-499. 

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FEMA. 2010c. “Minimizing Water Intrusion through Roof Vents in High-Wind Regions,” Technical 

Fact Sheet No. 7.5. FEMA P-499, Homebuilder’s Guide to Coastal Construction.

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FEMA. 2010d. “Siding Installation in High-Wind Regions,” Technical Fact Sheet 5.3. FEMA P-499. 

Homebuilders Guide to Coastal Construction. 

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FEMA. 2010e. Substantial Improvement/Substantial Damage Desk Reference, FEMA P-758. 

https://www.fema.gov/media-library/assets/documents/18562. 
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT B-3

REFERENCES

FEMA. 2010f. Wind Retrofit Guide for Residential Buildings, FEMA P-804. 

https://www.fema.gov/media-library/assets/documents/21082. 

FEMA. 2011. Coastal Construction Manual, FEMA P-55. 

https://www.fema.gov/media-library/assets/documents/3293. 

FEMA. 2013a. Floodproofing Non-Residential Buildings, FEMA P-936. 

https://www.fema.gov/media-library/assets/documents/34270. 

FEMA. 2013b. Mitigation Assessment Team Report: Hurricane Sandy in New Jersey and New York, FEMA 

P-942. https://www.fema.gov/media-library/assets/documents/85922. 

FEMA. 2015a. Highlights of ASCE 24-14 Flood Resistant Design and Construction. 

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FEMA. 2015b. NFIP Flood Insurance Floodproofing Certificate for Non-Residential Structures, FEMA Form 

FEMA Form 086-0-34. June 2, 2015. 

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FEMA. 2016. “Revised Specific Rating Guidelines Effective April 1, 2017.” MEMORANDUM FOR: 

Write Your Own (WYO) Principal Coordinators and the National Flood Insurance Program 

(NFIP) Servicing Agent. December 14, 2016. 

https://www.fema.gov/media-library/assets/documents/34620. 

FEMA. 2018a. Adjuster Preliminary Damage Assessment, FEMA Form 086-0-20. September 12, 2018. 

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FEMA. 2018b. Answers to Questions about Substantially Damaged Buildings, FEMA 213. 

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FEMA. 2018c. “Disasters” (webpage). Accessed December 2018. 

https://www.fema.gov/disasters.

FEMA. 2018d. Dry Floodproofing: Operational Considerations, Hurricane Irma in Florida Recovery 

Advisory 1. https://www.fema.gov/media-library/assets/documents/158123.

FEMA. 2018e. Dry Floodproofing: Planning and Design Considerations, Hurricane Harvey in Texas

Recovery Advisory 1. 

https://www.fema.gov/media-library/assets/documents/158123.

FEMA. 2018f. Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) Florida 

Building Code, Hurricane Irma in Florida Recovery Advisory 3. 

https://www.fema.gov/media-library/assets/documents/158123.

FEMA. 2018g. “Recovery Support Functions” (webpage). 

https://www.fema.gov/recovery-support-functions. 

FEMA. 2018h. Soffit Installation in Florida, Hurricane Irma in Florida Recovery Advisory 2. 

https://www.fema.gov/media-library/assets/documents/158123.

Florida DEP (Department of Environmental Protection). 2018. Hurricane Irma Post-Storm Beach 

Conditions and Coastal Impact in Florida Report. Division of Water Resource Management. 
B-4 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IRMA IN FLORIDA

REFERENCES

https://floridadep.gov/water/engineering-hydrology-geology/documents/

hurricane-irma-post-storm-beach-conditions-and-coastal.

Florida Division of Emergency Management. 2018a. Elevation Certificates. 

https://www.floridadisaster.org/elevation-certificates/.

Florida Division of Emergency Management. 2018b. Floodplain Management in Florida: Quick Guide. 

https://www.floridadisaster.org/dem/mitigation/floodplain/community-resources/.

Florida Division of Emergency Management. 2018c. Florida Post-Disaster Toolkit for Floodplain 

Administrators. 

https://www.floridadisaster.org/dem/mitigation/floodplain/community-resources/.

Florida Division of Emergency Management. 2018d. “State Floodplain Management Program” 

(webpage). https://www.floridadisaster.org/dem/mitigation/floodplain/.

Florida House of Representatives. 2018. Select Committee on Hurricane Response & Preparedness Final 

Report. January 16, 2018. 

https://www.myfloridahouse.gov/Sections/Documents/loaddoc.aspx?PublicationTy

pe=Committees&CommitteeId=2978&Session=2018&DocumentType=General%20

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(website). Accessed December 2018. https://web.fulcrumapp.com/communities/nsf-rapid.

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– FBCEB (FBC, Existing Building), 5th (2014) and 6th (2017) Editions.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT B-5

REFERENCES

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– FBCM (FBC, Mechanical), 5th (2014) and 6th (2017) Editions.

– FBCP (FBC, Plumbing), 5th (2014) and 6th (2017) Editions.

– FBCR (FBC, Residential), 5th (2014) and 6th (2017) Editions.

– FBC, Test Protocols (High-Velocity Hurricane Zone [HVHZ] Test Protocols), 5th (2014) 

and 6th (2017) Editions.

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Systems with Air-Permeable Cladding.

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(webpage). https://earthobservatory.nasa.gov/images/90948/hurricane-irma-strikes-florida.

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Miami, Florida. http://www.aoml.noaa.gov/hrd/flyers/HurricaneAndrewHandoutCat5b.pdf.

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Jamie R. Rhome, and Daniel P. Brown. National Hurricane Center. 20 December 2005. 

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Eric S. Blake, Hugh D. Cobb III, and David P. Roberts. National Hurricane Center . 12 

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August–12 September 2017. John P. Cangialosi, Andrew S. Latto, and Robbie Berg National 

Hurricane Center. 30 June 2018. 

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3692ba7d1fe&_sm_au_=iVVqtf7Tr510QTRn.

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September 2017. https://stn.wim.usgs.gov/fev/#IrmaSeptember2017.
HURRICANE IRMA IN FLORIDA MITIGATION ASSESSMENT TEAM REPORT C-1

C

Recovery Advisory 1:

Dry Floodproofing: Operational Considerations

Recovery Advisory 2:

Soffit Installation in Florida

Recovery Advisory 3:

Mitigation Triggers for Roof Repair and Replacement 

in the 6th Edition (2017) Florida Building Code

Appendix C: 

Recovery Advisories
Dry Floodproofing: Operational Considerations FL-RA1 / May 2018 Page 1 of 9

Dry Floodproofing: 

Operational Considerations

HURRICANE IRMA IN FLORIDA Recovery Advisory 1, May 2018

Purpose and Intended Audience 

The purpose of this advisory is to provide guidance on how to effectively implement dry floodproofing 

mitigation measures for non-residential structures. This Recovery Advisory incorporates observations 

made by the Federal Emergency Management Agency (FEMA) Mitigation Assessment Teams (MATs) in 

Texas and Florida after Hurricanes Harvey and Irma. It describes best practices and lessons learned about 

planning, preparation, and operations of dry floodproofing systems that can make facilities more resistant to 

disruption in future flood events. The information in this advisory is directed toward existing and new, nonresidential facilities.

The guidance in this advisory, along with other FEMA 

publications related to dry floodproofing, should be used by 

building owners and design professionals to take action to 

limit the interruption of building services and flood damage to 

buildings. It will also be useful to communities and building 

owners preparing designs and proposals for FEMA Section 

404 Hazard Mitigation grants and hazard mitigation elements 

included in recovery funding available through FEMA Section 

406 Public Assistance. 

The primary audience for this advisory includes building 

owners, operators, and managers; installers; and contractors, 

but may also be helpful for architects, engineers, various 

planners, as well as local government and building code 

officials involved with building planning, design, enforcement, 

operations, or maintenance. It will also be useful to 

communities and building owners preparing designs and proposals for FEMA hazard mitigation funding. 

FEMA Public Assistance Program 

Funding for Dry Floodproofing Projects

In addition to funding for repair 

and recovery projects, FEMA Public 

Assistance (PA) Program funding may 

be available for cost-effective hazard 

mitigation measures that increase 

resilience, such as dry floodproofing 

projects. For more information, refer 

to Chapter 2 Section VII.C., “Hazard 

Mitigation” of FEMA’s Public Assistance 

Program and Policy Guide (2018). 

Key Issues

" Some dry floodproofing systems were not regularly tested or properly maintained. When the systems were 

installed prior to the storm, several systems did not provide the intended level of protection.

" Some facilities lacked formal or written documentation on who, how, when, and where to deploy 

floodproofing systems, which resulted in time and energy wasted on a disorderly or partial deployment 

prior to the event. 

This Recovery Advisory Addresses

" Observations related to dry floodproofing system operations

" Operations, maintenance, and testing plans for dry floodproofing systems 

" Deployment considerations for active dry floodproofing

" Floodproofing considerations for a facility Emergency Operations Plan

A companion advisory, titled Dry Floodproofing: Planning and Design Considerations (Hurricane Harvey in Texas, 

TX-RA1, 2018), describes observations of system failures; flood vulnerability assessments; and planning and 

design considerations for dry floodproofing.
Dry Floodproofing: Operational Considerations FL-RA1 / May 2018 Page 2 of 9

Observations Related to Dry Floodproofing System Operations 

The floodwaters of Hurricanes Harvey and Irma 

tested passive and active dry floodproofing 

systems. Dry floodproofing involves using passive 

and active measures to seal a structure or area so 

floodwater cannot enter (see text box). 

With the uncertainty surrounding the tracks of 

both storms and amount of flooding predicted from 

rainfall and storm surge, the planning, preparation, 

and installation of dry floodproofing systems was a 

timing and logistical challenge. 

After Hurricanes Harvey and Irma, the MATs 

deployed by FEMA to evaluate building 

performance observed some best practices 

that enhanced response, such as the use of 

passive floodproofing systems that operated 

automatically with the rise of floodwater. However, 

the MATs observed other active measures that 

created significant challenges, such as systems 

that required a sizeable crew with heavy and 

specialized equipment to mobilize over a period of 

several days in advance of the storm to properly 

install the system. 

The damage observed by the MATs illustrate 

that planning for dry floodproofing deployment is 

inconsistent, installation of dry floodproofing is 

not always effective, and even when installed, 

the level of effectiveness of the operation and 

implementation of dry floodproofing systems is 

variable. 

Dry Floodproofing Systems

Active: Dry floodproofing systems that require 

human intervention to deploy the physical 

barrier and are effective only if there is enough 

warning time to mobilize the labor and equipment 

necessary to implement them and safely evacuate.

Passive: Dry floodproofing systems that do not 

require human intervention to deploy the physical 

barrier.

The image below (from Delaware, 2007) shows 

an example of an active dry floodproofing barrier 

installed at a commercial property.

Key Terminology

Flood Barrier: The physical barrier, composed of Floodwall: A constructed barrier of flood damageopening protection, floor slab, and wall system, resistant materials to keep water away from or out 

that separates floodwater from the dry floodproofed of a specific area. Floodwalls surround a building 

portion of the building. and are typically offset from the exterior walls of 

Opening Protection: the building; some floodwalls can be integrated into A cover, shield, or door that 

the building envelope. Floodwalls are considered a covers a window, doorway, loading dock access, or component of the overall flood barrier. other opening in a building wall or floor. Sometimes 

called a “closure device.” Flood Entry Point: Any opening, joint, gap, crack, 

low point, or other location through or over which 

floodwater can enter.
Dry Floodproofing: Operational Considerations FL-RA1 / May 2018 Page 3 of 9

Operations, Maintenance, and Testing Plans for Dry Floodproofing Systems 

Both the American Society of Civil Engineers, Standard 

for Flood Resistant Design and Construction (ASCE 

2014), and the National Flood Insurance Policy (NFIP) 

guidelines require that the operations, maintenance, 

and testing1 plan of a dry floodproofing system be 

developed during the design of the system and 

regularly updated throughout the life of the building. 

The procedures described in the operations, 

maintenance, and testing plan should be conducted 

annually and considered part of the long-term 

approach to maintaining the effectiveness of the 

building’s flood protection system. The floodproofing 

components at installation locations should be 

inspected to evaluate system performance following 

any flood event and after any construction or 

demolition project in the building’s vicinity. Periodic 

deployment drills (at least annually) should also 

be specified in the operations, maintenance, and 

testing plan. FEMA recommends that the operations, 

maintenance, and testing plan include the following 

items: 

" A decision tree identifying responsible parties, 

a sequence and timeline by which various 

components will be installed, including identified 

triggers or benchmarks to initiate procedures

" A list of personnel, equipment, and supplies 

needed to deploy all system components

" A map of the equipment storage location and 

component deployment locations

" A record of the manufacturer or designer and their 

contact information for expediting replacement 

parts and support as needed

" A copy of the NFIP Floodproofing Certificate 

In addition to the above-described elements of the 

operations, maintenance, and testing plan, the 

following should be considered. These are based 

on MAT observations of damage and interviews with 

building owners and managers after Hurricanes Harvey 

and Irma.

Size and weight. Consider the size and weight of 

individual dry floodproofing panels when choosing or 

designing a system and the openings they will cover 

Applicable Codes

ASCE 24 (Section 6.2.3) describes 

implementation requirements and restrictions 

for dry floodproofing new buildings and when 

Substantial Improvements are made to 

existing buildings. Owners who want to dry 

floodproof existing buildings may also benefit 

from following the guidelines in this standard.

NFIP Floodproofing Certificate

The requirements of the NFIP Floodproofing 

Certificate are described in FEMA P-936 

(1993) and should be understood before 

starting design. The NFIP Floodproofing 

Certificate requires compliance with ASCE 

24 and is both a design and construction 

certification. Professional engineers and 

architects should read the Floodproofing 

Certificate in its entirety and the applicable 

sections of ASCE 24, FEMA P-936, and 

Technical Bulletin 3, “Non-Residential 

Floodproofing” (FEMA 1993), prior to signing it.

Responsible Parties 

Deployment of dry floodproofing systems is a 

shared responsibility of the building owner or 

manager, installer (i.e., contracted or on-site 

staff), and possibly building occupants.

Figure 1: Large (6 feet high x 6 feet wide) metal flood panel 

requiring special equipment for installation

1 The terms “testing” and “exercising” are used interchangeably in 

this advisory although they may have different definitions for design 

professionals and emergency managers. Regular evaluation of how the 

dry floodproofing system performs (under practice and design flood 

conditions) can improve a facility’s response to disruption in future 

flood events.
Dry Floodproofing: Operational Considerations FL-RA1 / May 2018 Page 4 of 9

(Figure 1). If there are difficulties in installing large panels, consider approaches to improve the installation 

process. This may entail replacing the panel type with a passive floodproofing component or with a 

component that is easier to install. 

System manufacturer. Flood protection systems should come from a reputable manufacturer and be 

consistent with a testing standard such as ANSI/FM 2510 that includes performance standards for 

hydrostatic test strength, system leakage, corrosion, and resistance to impact, wear, abrasion, tear, and 

puncture. 

Storage. Determine an appropriate storage location for the dry 

floodproofing components, supplies, and equipment. Ensure 

the location is not open to the elements, as ultraviolet radiation 

and temperature extremes degrade rubber seals, gaskets, and 

component identification labels (Figure 2). Ensure this location 

is secure to prevent theft and vandalism, but is also accessible 

and labeled for the installer in case of deployment. On-site 

storage of floodproofing components is preferable. A separate 

location should be provided for spare parts. 

All parts should be clearly labelled with permanent marker 

and a unique identification label that signifies its location 

when installed.

In-house versus contract staff. Assess the pros and cons 

of using contracted installers versus in-house staff. Ensure 

sufficient, trained staff will be available to implement the 

system prior to a flood event. Some dry floodproofing systems 

are installed by hired contractors who may be responsible 

for deploying systems at many sites across a city or region. 

Contract laborers may be limited in availability and timing in 

the days before an event.

Deployment drills. Conduct a deployment drill of the 

floodproofing system annually, or more frequently, 

as prescribed by the operations, maintenance, 

and testing plan, including testing all valves, sump 

pumps, power generators, and other drainage 

measures. An important task is to ensure that 

all valves or other drainage measures are clear 

of debris.

During drills and tests, building operators should 

record the number of workers, the equipment 

needed, and the time it takes to install part or 

all of the system, and any perceived system 

deficiencies should be identified. Ensure that any 

staff member who may be called upon to install 

specific floodproofing measures participates in 

drills and is familiar with and able to implement the 

floodproofing system. Ensure that the deployment 

drill considers egress requirements for personnel 

who remain inside the building.

Regular inspection. Regularly inspect and maintain shields, doors, gates, pumps, equipment, gaskets, 

seals, brackets, panels, hardware, etc., and replace immediately if needed, to ensure system performance 

(Figure 3). Use the equipment list in the operations, maintenance, and testing plan to perform an annual 

accounting of all component and installation equipment. 

Figure 2: Flood panels (metal) and window shutters 

(plywood) were stored together outside a building. 

Panels and rubber gaskets were exposed to the 

elements; this storage practice is not recommended. 

Figure 3: Torn gasket on metal flood panel after panel was 

removed. Gasket must be replaced before the next deployment. 
Dry Floodproofing: Operational Considerations FL-RA1 / May 2018 Page 5 of 9

Perform a building-wide inspection of all areas below 

the design flood elevation to check for penetrations 

in walls, floors, and ceilings, which are common 

sources of leakage during flood events. If not properly 

designed with seals able to withstand hydrostatic 

loads for their given locations, such penetrations 

can negate flood protection benefits afforded by any 

floodproofing systems.

Wet-testing. Perform wet-testing of the floodproofing 

system every 5 years or after gasket replacement. 

Water leak detection system. Install a water leak detection system behind the dry floodproofing system 

to allow remote monitoring to determine when passive systems are deployed and whether measures are 

performing as expected.

Provide labels. To discourage unnecessary penetrations, consider labeling the walls and slabs of a dry 

floodproofed area, including any flood barriers that are part of a building design (e.g., foundation walls) with 

“Dry Floodproofed: No Penetrations Below This Level;” the sign should indicate the design flood elevation on 

the wall (Figure 4). For any existing penetrations that are sealed with watertight components or assemblies, 

consider a similar marking or designation.

Penetrations Below Design Flood Elevation 

If any pipes, conduits, or ducts that penetrate 

below the design flood elevation cannot resist 

flood loads, a mitigation solution should be 

immediately identified and implemented. Refer 

to Hurricane Harvey Recovery Advisory TX-RA1 

for more information about penetrations.

Figure 4: Example 

signage on a dry 

floodproofed wall 

spaced appropriately to 

maintain awareness

Deployment Considerations for Active Dry Floodproofing

Dry floodproofing measures should be activated once specifically identified triggers or benchmarks occur per 

the facility Emergency Operations Plan (refer to the following section). The following list includes common 

considerations to help building owners and operators effectively deploy their active dry floodproofing systems. 

" Ensure that the appropriate building operations staff, installer, or municipality officials, if required, have 

copies of the operations, maintenance, and testing plan and the facility Emergency Operations Plan. 

" Deploy all components specified by the operations, maintenance, and testing plan.

" Deploy in the order and at the locations specified in the operations, maintenance, and testing plan. 

Consider prioritizing locations that are more vulnerable or critical. 

" Ensure that the dry floodproofing systems are installed correctly. Failure to install and tighten bolts, or 

repair/replace gaskets and seals as needed, can lead to leaks or floodproofing system failure.

DRY

FLOODPROOFED

NO PENETRATIONS BELOW 

THIS LEVEL

DRY

FLOODPROOFED

NO PENETRATIONS BELOW 

THIS LEVEL

Waterproof Sealant

Line indicates the design flood elevation
Dry Floodproofing: Operational Considerations FL-RA1 / May 2018 Page 6 of 9

" Verify that the system components required 

to install the dry floodproofing systems are 

stored together, as outlined in the operations, 

maintenance, and testing plan, with a separate 

area for spare parts (Figure 5). 

" For individual flood components, verify that 

each component has retained its marking with 

its unique identification label that signifies its 

location when installed (Figure 6). Stickers 

and ink have a tendency to degrade over time, 

potentially leaving installers unsure of the 

proper sequence or location of the panels. 

Some manufacturers make flood panels with 

installation directions directly on the panel 

rather than in a separate document.

" The map showing where 

the dry floodproofing 

components will be 

installed should be 

reviewed and made 

available, as needed. 

" If the flood panel 

requires a gasket to 

be inflated with air to 

ensure a watertight 

seal, provide redundant 

methods to maintain 

inflation, such as a 

portable air tank or 

pump (Figure 7).

Figure 5: Enclosed storage space for multiple flood panels, 

stanchions, and hardware

Figure 6: Installed flood panels. Each flood 

panel has a unique ID number. Also note the 

tightener bracket at top.

Figure 7: Flood gate with an air tank 

and a hand pump as a redundancy 

measure to inflate gaskets
Dry Floodproofing: Operational Considerations FL-RA1 / May 2018 Page 7 of 9

Floodproofing Considerations for a Facility Emergency Operations Plan

Floodproofing considerations should be included in 

the facility’s Emergency Operations Plan regardless 

of the size, scope, and complexity of the building(s). 

The scope and complexity of the floodproofing 

system and dry floodproofing measures will dictate 

the level of detail, phasing, and sequencing 

specified in the Emergency Operations Plan. It 

will also affect the equipment needed, number of 

personnel and time needed to install the system, 

maintenance requirements, appropriate training and 

exercising, and other issues. Flood-related considerations should address the process and timeline leading 

up to and during deployment, specific storm conditions that trigger deployment of floodproofing measures, 

and whether and how the system will be operated during the storm event. Specific additional emergency 

procedures should be developed for events larger than the design event.

Pertinent information from the floodproofing system’s operations, maintenance, and testing plan should 

be included in the floodproofing portion of the facility Emergency Operations Plan, as well as deployment 

considerations for active dry floodproofing measures (see previous subsections). Refer to Table 1 for details 

to evaluate when preparing the facility Emergency Operations Plan. 

Building owners and operators should review and update the floodproofing portions of their facility Emergency 

Operations Plan on an annual basis (e.g., after hurricane or rainy season), and after each time the facility’s 

floodproofing system is deployed. Pertinent information related to storm observations, system performance, 

damage to the floodproofing system, or any perceived system weaknesses or deficiencies should be recorded 

in both the facility Emergency Operations Plan and the operations, maintenance, and testing plan. 

The building owners and operators should ensure that the facility Emergency Operations Plan and 

operations, maintenance, and testing plan are accessible to appropriate building operations staff, installer, 

or municipality, if required, and are forwarded as part of any workplace transition to maintain institutional 

continuity. 

Hurricane Irma Floodproofing Example

A building manager stated that a contractor had 

installed parts of the dry floodproofing system at 

one entrance of a building, but had not installed 

the required components at another building 

entrance. The result was that the first floor of the 

building flooded.

Table 1: Floodproofing Considerations to Include in a Facility Emergency Operations Plan

Considerations Details to Evaluate

Standby Power • 

• 

• 

• 

How long will emergency generators supply power for the sump pump system and other 

building systems without an off-site fuel delivery? 

Will emergency generators be accessible during the flood event and equipped to operate 

during a flood event?

Will fuel delivery be hindered by the implemented dry floodproofing?

Are redundancy measures such as backup connections to other generators needed?

Prior to Event • 

• 

• 

• 

• 

• 

• 

• 

Who makes the decision to initiate mobilization and deployment of the floodproofing 

system? When will it occur based on warning time and expected flood conditions?

Is the facility Emergency Operations Plan permanently posted in at least two 

conspicuous locations?

What staff or contractors will be needed (e.g., maintenance staff, building engineer, 

contractors, installers) to retrieve and install active dry floodproofing components?

How many days prior to an event will personnel be mobilized?

How will personnel, equipment, and components be staged or phased?

Where are the storage location(s) and deployment location(s) of all necessary equipment?

How long will it take to deploy or activate the floodproofing system?

What is the system’s design flood elevation? What is the expected flood depth?
Dry Floodproofing: Operational Considerations FL-RA1 / May 2018 Page 8 of 9

Table 1: Floodproofing Considerations to Include in a Facility Emergency Operations Plan (concluded)

Considerations Details to Evaluate

Evacuation* • Under what conditions will the building be evacuated?

• Who will make the decision to evacuate the building in advance of or during a flood event?

• Which points are designated as egresses or emergency openings and are they

clearly marked?

• Does the means of egress allow the floodproofing measures to remain in place?

• How does the facility Emergency Operations Plan account for building evacuation timing

and sequencing?

Building

Occupancy

During Event*

• Will the building be occupied during a flood event? If yes, then by whom (e.g., maintenance

staff, employees, tenants)? What will their role be, if any, in deploying and operating the dry

floodproofing system?

• What will the occupants require in the event of an emergency (e.g., food, water, shelter)?

How will supplies be stockpiled and how will operations continue during the event?

• Will implemented dry floodproofing measures disrupt operations?

After the Event • What staff or contractors will be needed for cleanup, debris management, removal of

floodproofing equipment, and inspection of floodproofing equipment performance?

• How long will it take to resume normal operations?

* FEMA recommends evacuating a building before a flood event whenever possible. Building owners and operators should evacuate in 

accordance with state and local government orders or notices. For unique situations that may require critical personnel to remain behind, 

advanced coordination and planning should occur with the local government so that emergency and government personnel can plan accordingly 

for their jurisdictional emergency operations plan.

References and Resources 

References

ASCE (American Society of Civil Engineers). 2014. Standard for Flood Resistant Design and Construction. ASCE 

Standard ASCE 24-14.

American National Standards Institute and FM Approvals. 2014. Approval Standard for Flood Abatement 

Equipment. ANSI/FM 2510. http://www.fmapprovals.com/products-we-certify/products-we-certify/floodmitigation-products.

FEMA (Federal Emergency Management Agency). 1993. Non-Residential Floodproofing – Requirements and 

Certification. Technical Bulletin 3-93. https://www.fema.gov/media-library/assets/documents/3473.

FEMA 2013. Floodproofing Non-Residential Structures. FEMA P-936. https://www.fema.gov/media-library/

assets/documents/34270. 

Resources

ASCE. 2016. Minimum Design Loads of Buildings and Other Structures. ASCE Standard ASCE 7-16.

ASFPM (Association of State Floodplain Managers). n.d. “National Flood Barrier Testing & Certification 

Program.” http://www.nationalfloodbarrier.org. 

FEMA. 2017. Protecting Building Utility Systems from Flood Damage. FEMA P-348. https://www.fema.gov/

media-library/assets/documents/3729.

Risk Management Series publications listed below are available at https://www.fema.gov/security-riskmanagement-series-publications.

" FEMA. 2007. Design Guide for Improving Critical Facility Safety from Flooding and High Winds. FEMA P-543.
Dry Floodproofing: Operational Considerations FL-RA1 / May 2018 Page 9 of 9

" FEMA. 2007. Design Guide for Improving Hospital Safety in Earthquakes, Floods, and High Winds.

FEMA P-577.

" FEMA. 2010. Design Guide for Improving School Safety in Earthquakes, Floods, and High Winds.

FEMA P-424.

Technical Bulletins listed below are available at https://www.fema.gov/media-library/collections/4.

" FEMA. 1993. Non-Residential Floodproofing – Requirements and Certification. Technical Bulletin 3-93.

" FEMA. 1993. Wet Floodproofing Requirements. Technical Bulletin 7-93.

" FEMA. 2008. Flood Damage-Resistant Materials Requirements. Technical Bulletin 2. 

Recovery Advisories for Hurricane Sandy listed below are available at https://www.fema.gov/media-library/

assets/documents/30966.

" FEMA. 2013. Reducing Flood Effects in Critical Facilities. Hurricane Sandy RA2.

" FEMA. 2013. Reducing Interruptions to Mid- and High-Rise Buildings During Floods. Hurricane Sandy RA4.

" FEMA. 2013. Designing for Flood Levels Above the BFE After Hurricane Sandy. Hurricane Sandy RA5.

Recovery Advisories from the 2016 Fall Flooding in Iowa listed below are available at https://www.fema.gov/

media-library/assets/documents/130555. 

" FEMA. 2017. Flood Protection for Critical and Essential Facilities. 2016 Fall Flooding in Iowa RA3.

" FEMA. 2017. Flood Protection and Elevation of Building Utilities. 2016 Fall Flooding in Iowa RA4.

" FEMA. 2017. Flood Protection for Backup and Emergency Power Fuel Systems. 2016 Fall Flooding in 

Iowa RA5.

For more information, see the FEMA Building Science 

Frequently Asked Questions website at http://www.fema.

gov/frequently-asked-questions-building-science.

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Please scan this QR code 

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Science web page.
Soffit Installation in Florida FL-RA2 / May 2018 Page 1 of 7

Soffit Installation 

in Florida

HURRICANE IRMA IN FLORIDA Recovery Advisory 2, May 2018

Purpose and Intended Audience

This Recovery Advisory provides soffit installation 

guidance and resources to meet or exceed minimum 

provisions of the 6th Edition (2017) Florida Building 

Code, Residential (FBCR). The primary audience for 

this advisory includes contractors and homeowners, 

but may also be helpful for building officials and 

design professionals. 

Key Issues 

" Wind-damaged soffits allowed wind-driven rain 

to enter building envelopes, resulting in costly 

damage to building interiors.

" While some water was blown into attics through 

soffit vents, the amount of water intrusion 

increased dramatically when the soffit material 

was missing (Figure 1).

" Need for clarification of how to meet the 6th 

Edition (2017) FBCR soffit installation criteria. 

This Recovery Advisory Addresses 

" Soffit design wind loads and installation in the 

Florida Building Code

" Installing the soffit

Soffit Design Wind Loads and Installation 

in the Florida Building Code

Compliance with the 6th Edition (2017) of the 

Florida Building Code (FBC) is required throughout 

the state for building permits issued after 

December 31, 2017, including projects to repair 

and rebuild Hurricane Irma damage. One- and twofamily dwellings are covered under the scope of the 

FBCR. Soffit provisions in the 6th Edition (2017) of 

FBCR were updated from the previous (5th) edition 

as follows:

1. In the 6th Edition (2017) FBCR Component and 

Cladding Load Table R301.2(2), design wind 

pressures are tabulated as Allowable Stress 

Design (ASD)-level values. The 5th Edition 

(2014) FBCR tabulated strength design-level 

Florida Building Code and International Code 

Council Codes

The 2015 International Residential Code (IRC) 

serves as the base code for the 6th Edition (2017) 

FBCR. Florida-specific amendments are added 

through the state’s established code development 

process. The Florida Building Codes can be viewed 

for free through the “Public Access” option on the 

ICC website: https://codes.iccsafe.org/public/

collections/FL.

Figure 1: Vinyl soffit damage on a home in Sugarloaf Key

Soffit Vents

Refer to the 6th Edition (2017) of FBCR Section 

R806 for roof venting provisions. To avoid water 

entry at soffit vents, options include eliminating 

soffit vents and providing an alternate method 

for air to enter the attic, or designing for an 

unvented attic. Another approach is to place filter 

fabric (like that used for heating, ventilation, or 

air conditioning system filters) above the vent 

openings; however, such an approach needs to 

be custom designed. For additional guidance 

on mitigating water intrusion through attic vents 

and strengthening undamaged soffits, refer 

to Technical Fact Sheet No. 7.5, “Minimizing 

Water Intrusion Through Roof Vents in High-Wind 

Regions” in FEMA P-499, Homebuilder’s Guide to 

Coastal Construction (FEMA 2010).
Soffit Installation in Florida FL-RA2 / May 2018 Page 2 of 7

wind pressures and included a note that permitted the values to be multiplied by 0.6 for ASD. Since 

component and cladding products are rated using ASD wind pressures, the 6th Edition table values 

should be easier to use than the previous edition’s. 

2. The effective wind area for soffit design pressures is specified as 10 square feet. The clarification 

simplifies soffit load determination. Unlike Table R301.2(2) in the FBCR, Table 1 on page 3 of this advisory 

is further simplified for soffit applications and only includes design pressures for effective wind areas of 

10 square feet. 

Installing the Soffit

Meeting the 6th Edition (2017) FBCR soffit 

installation criteria requires determining (1) the siteand location-specific wind loads that soffits must 

resist, and (2) which soffit assemblies are rated and 

approved to meet the wind load demand, and how 

the chosen soffit assembly must be installed to 

perform as designed.

Step 1: Determine the Wind Loads

Follow the steps below to find minimum soffit 

wind loads (pressures) in accordance with the 

2017 FBCR.

1. Determine location- and site-specific factors 

that affect the soffit wind pressures. 

a. Design wind speed: Find location-specific 

design wind speeds in Figure R301.2(4) of 

the 6th Edition (2017) FBCR. Wind speeds for specific addresses and latitude/longitude can be found 

at http://windspeed.atcouncil.org or https://asce7hazardtool.online/. For one- and two-family dwellings, 

select wind speeds given for ASCE 7-10, Risk Category II.

b. Exposure category: Check with your local building official to determine site-specific exposure category 

(B, C, or D) in accordance with the 6th Edition (2017) FBCR Section 301.2.1.4.3. Keep in mind that 

exposure category can vary within individual neighborhoods because it is related to the terrain that 

surrounds the building.

c. Mean roof height: Determine the mean roof height (MRH) in accordance with the 6th Edition (2017) 

FBCR Section R202 definition: “The average of the roof eave height and the height to the highest point 

on the roof surface, except that eave height shall be used for a roof angle of less than or equal to 10 

degrees.” Refer to Figure 2 for clarification. 

2. Using the site-specific wind speed determined 

in Step 1a, find the Zone 4 and Zone 5 

pressures using Table 1. 

Zone 5 wind pressures apply to soffit surfaces 

within 4 feet of wall corners, and Zone 4 wind 

pressures apply to all other areas. The selected 

soffit system must resist the building’s highest 

(Zone 5) wind pressures, so calculating Zone 

4 pressures will not be necessary for many 

assemblies (refer to Figure R301.2(7)). 

3. Modify the wind pressure(s) for the specific 

wind zone, as determined in Step 2, for factors 

determined in Steps 1b and 1c.

FBCR Soffit Installation Provision

The following Chapter 7 (Wall Covering) provisions 

specifically address soffit installation:

R703.1.2.1 Wind resistance of soffits: Soffits 

and their attachments shall be capable of resisting 

wind loads specified in Tables R301.2(2) and 

R301.2(3) for walls using an effective wind area of 

10 square feet.

R703.11.1.4 Vinyl soffit panels: Soffit panels 

shall be individually fastened to a supporting 

component such as a nailing strip, fascia or 

subfascia component or as specified by the 

manufacturer’s instructions.

Source: 6th Edition (2017) FBCR

Figure 2: Illustration showing how to determine the MRH
Soffit Installation in Florida FL-RA2 / May 2018 Page 3 of 7

To do this, multiply wind pressure values by the coefficients in Table 2 as needed to adjust for exposure 

categories other than B and MRHs other than 30 feet. For MRHs between those given in Table 2, use the 

value assigned to the higher MRH or interpolate between the higher and lower values. 

4. Select a soffit system rated to resist Zone 5 pressures determined in Step 3. 

In some cases, such as the prescriptive wood structural panel soffit, the soffit attachment schedule may 

be reduced for (lesser) Zone 4 pressures where soffit sections are 4 feet or more from building corners. 

Follow material-specific guidance in Step 2 of this advisory to ensure compliant application. 

Table 1: Soffit Positive and Negative Pressures (Pounds per Square Foot) for Zones 4 and 5 with MRH=30 feet, Exposure B

115 mph 120 mph 130 mph 140 mph 150 mph 160 mph 170 mph 180 mph

Zone 4

-15.0 -16.0 -19.0 -22.0 -26.0 -30.0 -33.0 -37.9

14.3 15.5 18.2 21.2 24.3 27.7 31.2 35.0

Zone 5

14.3 -20.0 -24.0 -28.0 -32.0 -37.0 -41.0 -46.8

-19.0 15.5 18.2 21.2 24.3 27.7 31.2 35.0

Source: Table R301.2(2) in the FBCR, abbreviated to address Florida-specific wind speeds and wall zones only; available at https://codes.iccsafe.

org/public/collections/FL.

Table 2: Height and Exposure Adjustment Coefficients for Soffit Pressure

Mean Roof Height (feet) Exposure B Exposure C Exposure D

15 1.00 1.21 1.47

20 1.00 1.29 1.55

25 1.00 1.35 1.61

30 1.00 1.40 1.66

35 1.05 1.45 1.70

40 1.09 1.49 1.74

45 1.12 1.53 1.78

50 1.16 1.56 1.81

55 1.19 1.59 1.84

60 1.22 1.62 1.87

Source: Table R301.2(3) in the FBCR available at https://codes.iccsafe.org/public/collections/FL.

Step 2: Material-Specific Soffit Installation

Whether or not a soffit installation is code-compliant depends on both the material and product. In Florida, 

manufactured soffit products must be approved as described in the text box titled “Florida Product Approval” 

because they are part of the building envelope and included under the “panel walls” product category. As 

such, selecting manufactured soffit products with up-to-date Florida product approval is the first required step 

for most soffit installations. Alternately, wood structural panel soffits may be assembled and installed on site 

to resist the wind pressures determined in Step 1 using the prescriptive approach described at the end of 

this section.

Soffit system support and corrosion resistance. Regardless of whether the chosen soffit system is 

manufactured or assembled prescriptively using wood structural panels, soffit system support and the 

corrosion resistance of the soffit fasteners must be addressed. Section 802 of the 6th Edition (2017) FBCR 

and Section 3.5 of the 2015 Edition Wood Frame Construction Manual provides requirements for ceiling 

joists, rafter overhangs, rake overhangs, and outlookers that support soffit systems. Section R703.3.2 

of the 6th Edition (2017) FBCR requires corrosion-resistant wall covering fasteners in accordance with 

manufacturer’s installation instructions. Refer to Note 1 of Table 3 for guidance on corrosion protection 

specific to wood structural panel soffits. 
Soffit Installation in Florida FL-RA2 / May 2018 Page 4 of 7

Florida Product Approval

Rule 61G20-3 of the Florida Administrative Code applies to products and systems that comprise the 

building envelope and structural frame. The rule requires the following products to have product approval 

for compliance with the structural requirements of the Florida Building Code:

• Panel walls • Windows

• Exterior doors • Shutters

• Roofing products • Structural components

• Skylights • Impact protective systems

Products may be approved using either the optional statewide product approval system or local product 

approval. Regardless of the method used, products have to be evaluated for compliance (evaluation 

report, certification, test report, etc.), be validated for compliance with the evaluation, and approved by 

the Florida Building Commission. For additional information on product approval in the State of Florida, 

see Rule 61G20-3 of the Florida Administrative Code or the Building Code Information System at http://

www.floridabuilding.org administered by the Florida Department of Business and Professional Regulation. 

A database of products approved using the statewide product approval system can be found under the 

“Product Approval” tab at http://www.floridabuilding.org.

Navigating the Florida Approval Website to Find Approved Products for Your Location

1. Link to the main page: http://www.floridabuilding.org

2. Select the “Product Approval” option from the left margin

3. From the Product Approval menu, select “Find a Product or Application”

4. From the “Category” pull-down options, select “Panel Walls”

5. From the “Subcategory” pull-down options, select “Soffits”

6. For “Application Status,” select “Approved”

7. If in Broward or Miami-Dade Counties, select “Yes” from “Approved for use in HVHZ”

8. Click on “Search”

9. Select any given listing to determine allowable “Design Pressure” and installation instructions

In some cases, allowable design pressures are shown in “Summary of Products” at the bottom of the 

page. In other cases, it is necessary to open the Evaluation Report(s) or Installation Instructions linked in 

the right column of “Summary” for design pressures.

Since fastener vulnerability to corrosion varies with location, check with your local building official for 

any specific requirements or guidelines. For further recommendations on corrosion-resistant connectors, 

see Table 1 in the National Flood Insurance Program Technical Bulletin 8, Corrosion Protection for Metal 

Connectors in Coastal Areas (FEMA 1996). 

Manufactured soffit systems. Since February 2018, the Florida Product Approval website has listed 

approved soffit assemblies for vinyl, metal (aluminum and steel), fiber cement, and engineered wood 

assemblies. 

To find the rated design pressures approved for each product, refer to the evaluation report and/or the 

installation instructions linked at the bottom of each product page. Only soffit panels that have been rated to 

meet or exceed the wind pressures determined for the specific location and site should be installed. See the 

text box for Florida Product Approval website navigation tips. 

When selecting soffit systems from the Florida Product Approval website that meet the wind pressure loading 

for your building, note that individual product installation instructions vary with respect to the information and 
Soffit Installation in Florida FL-RA2 / May 2018 Page 5 of 7

level of detail provided. Review the installation instructions on the Florida Product Approval website for any 

prospective product prior to purchasing while considering the following: 

" When determining soffit pressure resistance from the evaluation report or installation instructions, select 

“Allowable Design Load,” not “Ultimate Load.” If needed, Ultimate Loads can be converted to Allowable 

Design Loads by multiplying values by 0.6.

" Check whether the installation instructions have sufficient detail needed to install and inspect the soffits. 

In cases where blocking or substrate size and/or attachment to framing indicates “by others” or “per 

project requirements,” the details will need to be specified and sealed by a professional engineer licensed 

in Florida for site-specific loads. 

" Ensure that the installation instructions include all referenced details needed for the chosen design 

pressure application.

Wood structural panel, closed soffit. 

As an alternative to manufactured soffit 

systems, wood structural panel soffits 

may be prescriptively installed to resist 

the location- and site-specific wind 

pressures determined in Step 1. 

Where the design pressure is 30 

pounds per square foot (psf) or less, 

wood structural panel soffits should 

be a minimum of 3/8 inch in thickness 

and fastened to framing or nailing 

strips with a minimum of 6d box nails 

(2-inch x 0.099-inch x 0.266-inch 

head diameter [flat head]) spaced not 

more than 6 inches on center at panel 

edges and 12 inches on center at 

intermediate supports.

For design pressures greater than 30 

psf, refer to Table 3 for modified panel 

thickness, fastener type, size, and 

spacing. See Figure 3 for a detail of a 

wood structural panel, closed soffit.

Figure 3: Detail of wood structural panel, closed soffit

Protect edges of 

Exposure 1 sheathing 

against weather

Any appropriate 

grade of Exterior 

panels for closed 

soffit per Table 3

Leave 1/8 inch space at all 

panel end and edge joints. 

Support all panel edges.

Fasteners per Table 3

Wood Structural Panel Sheathing 

Wood structural panel sheathing is manufactured with span ratings of 12/0, 16/0, 20/0, 24/0, 24/16, 

32/16, 40/20, and 48/24, in performance categories ranging from 5/16 to 3/4, and in two bond 

classifications: Exterior and Exposure 1. 

Span ratings appear as two numbers separated by a slash, such as 32/16, 48/24, etc. The left-hand 

number denotes the maximum recommended spacing of supports when the panel is used for roof 

sheathing with the strength axis of the panel across three or more supports (two or more spans). The 

right-hand number denotes the maximum recommended spacing of supports when the panel is used 

for subflooring with the strength axis of the panel across three or more supports (two or more spans). A 

panel marked 32/16, for example, may be used for roof decking over supports up to 32 inches on center 

or for subflooring over supports up to 16 inches on center. 

Source: APA, http://www.wooduniversity.org/glossary
Soffit Installation in Florida FL-RA2 / May 2018 Page 6 of 7

Table 3: Installation Information for Wood Structural Panel, Closed Soffit 

Maximum 

Design Pressure 

(- or + psf)

Minimum 

Nominal Panel 

Thickness 

(inch) Nail Type and Size (inch)

Fastener Spacing along 

Supports (inch)

Galvanized 

Steel

Stainless 

Steel

40 3/8 6d box (2 x 0.099 x 0.266 head diameter) 6 4

50 3/8

6d box (2 x 0.099 x 0.266 head diameter) 4 4

8d common (21⁄2 x 0.131 x 0.281 head diameter) 6 6

60 3/8

6d box (2 x 0.099 x 0.266 head diameter) 4 3

8d common (21⁄2 x 0.131 x 0.281 head diameter) 6 4

70 7/16

8d common (21⁄2 x 0.131 x 0.281 head diameter) 4 4

10d box (3 x 0.128 x 0.312 head diameter) 6 4

80 7/16

8d common (21⁄2 x 0.131 x 0.281 head diameter) 4 4

10d box (3 x 0.128 x 0.312 head diameter) 6 4

90 15/32

8d common (21⁄2 x 0.131 x 0.281 head diameter) 4 3

10d common (3 x 0.148 x 0.312 head diameter) 6 4

Notes:

1: Fastener spacing for galvanized steel nails can be larger than for stainless steel nails of the same diameter and length because galvanized steel 

nails have better withdrawal resistance from wood. Hot-dip galvanized steel nails or stainless steel nails are recommended in coastal areas. 

2: Maximum spacing of soffit framing members = 24 inches; tabulated values assume minimum two-span continuous condition.

3: Only exterior panels should be used for closed soffits. To achieve pressure values shown in Table 3, panels must be installed with strong axis 

across supports. A 3/8-inch, 7/16-inch, and 15/32-inch minimum nominal panel thickness is associated with minimum panel span ratings (e.g., 

panel grade) of 24/0, 24/16, and 32/16, respectively. 

4: Tabulated nail spacing assumes sheathing is attached to soffit framing members with a specific gravity of at least 0.42, which includes the 

following species combinations: spruce-pine-fir, hem-fir, Douglas-fir-larch, and southern pine. 

Source: Table adapted from data available in National Design Specifications for Wood Construction (AWC 2015) and Special Design Provisions for 

Wind & Seismic (AWC 2015). 

References and Useful Links

References

ASCE (American Society of Civil Engineers). 2010. ASCE 7-10, Minimum Design Loads for Buildings and 

Other Structures.

AWC (American Wood Council). 2015. National Design Specifications for Wood Construction. http://www.awc.

org/pdf/codes-standards/publications/nds/AWC-NDS2015-ViewOnly-1603.pdf?_sm_au_=iVV06qrjPvPZPnZj.

AWC. 2015. Special Design Provisions for Wind & Seismic. http://www.awc.org/pdf/codes-standards/

publications/sdpws/AWC-SDPWS2015-ViewOnly-1508.pdf.

AWC. 2015. Wood Frame Construction Manual for One- and Two-Family Dwellings. http://www.awc.org/pdf/

codes-standards/publications/wfcm/AWC-WFCM2015-ViewOnly-1510.pdf. 

FEMA (Federal Emergency Management Agency). 1996. Technical Bulletin 8, Corrosion Protection of Metal 

Connectors in Coastal Areas. https://www.fema.gov/media-library/assets/documents/3509.

FEMA. 2010. Home Builder’s Guide to Coastal Construction. FEMA P-499. https://www.fema.gov/media-library/

assets/documents/6131.
Soffit Installation in Florida FL-RA2 / May 2018 Page 7 of 7

Useful Links

“Florida Building Codes.” Florida Department of Business & Professional Regulation (DBPR). 

Link: https://www.floridabuilding.org/bc/bc_default.aspx.

“APA Glossary.” WoodUniversity.Org. Link: https://www.wooduniversity.org/glossary.

“APA Help Desk.” WoodUniversity.Org. Link: https://www.apawood.org/help.

“Hazards by Location.” Applied Technology Council. Link: https://hazards.atcouncil.org/.

“ASCE 7 Hazard Tool.” American Society of Civil Engineers (ASCE). Link: https://asce7hazardtool.online/.

For more information, see the FEMA Building Science 

Frequently Asked Questions website at http://www.fema.

gov/frequently-asked-questions-building-science.

If you have any additional questions on FEMA Building 

Science Publications, contact the helpline at FEMABuildingsciencehelp@fema.dhs.gov or 866-927-2104.

You may also sign up for the FEMA Building Science email 

subscription, which is updated with publication releases 

and FEMA Building Science activities. Subscribe at https://

service.govdelivery.com/accounts/USDHSFEMA/subscriber/

new?topic_id=USDHSFEMA_193.

Visit the Building Science Branch of the Risk Management 

Directorate at FEMA’s Federal Insurance and Mitigation 

Administration at https://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

Email: FEMA-PublicationsWarehouse@fema.dhs.gov

Additional FEMA documents can be 

found in the FEMA Library at 

https://www.fema.gov/media-library/

resources.

Please scan this QR code 

to visit the FEMA Building 

Science web page.
Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) FBC FL-RA3 / May 2018 Page 1 of 9

Mitigation Triggers for Roof Repair 

and Replacement in the 6th Edition 

(2017) Florida Building Code

HURRICANE IRMA IN FLORIDA Recovery Advisory 3, May 2018

Purpose and Intended Audience

This Recovery Advisory provides guidance on wind mitigation triggers for roof repairs and replacement in the 

6th Edition (2017) Florida Building Code (FBC). The information in this advisory is particularly pertinent to 

repairs and rebuilding in areas of Florida recovering from Hurricane Irma. However, this information applies 

generally throughout Florida. The primary audience for this advisory includes building owners, operators, and 

managers; design professionals; building officials; contractors; and municipal building and planning officials. 

The guidance in this advisory should be incorporated or 

referenced to help in the development of repair scopes of 

work and/or hazard mitigation proposals for FEMA Section 

406 Public Assistance grants or used by designers and 

various stakeholders for other projects. Relevant guidelines 

and codes are listed in the text boxes to the right.

Key Issues 

" Damage requiring reroofing or roof repairs to withstand 

future events

" Need for clarification of the applicability of the 25% Rule 

in the FBC for reconstruction

" Need for clarification of mitigation actions required when 

a roof covering is replaced or repaired in Florida

This Recovery Advisory Addresses

" Roof repairs

" Residential wind mitigation

" Commercial wind mitigation

Roof Repairs

Building codes have historically required reroofing to meet 

the same requirements as new construction but permitted 

repairs to be made using like materials, provided no 

dangerous or unsafe condition was created by using such 

materials. However, as a result of the damage caused by 

the hurricanes of 2004, the FBC adopted several wind 

mitigation measures that apply when roofs are replaced 

or repaired. These provisions recognize that with the 

roof covering removed, upgrades and improvements to 

the resistance of the roof assembly (underlayment, roof 

decking, roof-to-wall connections) to wind loads and water 

penetration are more easily performed. 

FEMA Public Assistance Program and 

Policy Guide

See Section VII, “Permanent Work 

Eligibility” in FEMA’s Public Assistance 

Program and Policy Guide (FEMA 2018).

Florida Building Code

• Florida Building Code, Building (FBCB)

• Florida Building Code, Residential (FBCR)

• Florida Building Code, Existing Building 

(FBCEB)

Florida Building Code Definitions 

High-Velocity Hurricane Zones (HVHZ):

The HVHZ consists of Broward and Dade 

Counties.

Reroofing: The process of recovering or 

replacing an existing roof covering.

Roof Repair: Reconstruction or renewal 

of any part of an existing roof for the 

purposes of its maintenance.

Roof Replacement: The process of 

removing the existing roof covering, 

repairing any damaged substrate, and 

installing a new roof covering.

Source: 6th Edition (2017) FBC
Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) FBC FL-RA3 / May 2018 Page 2 of 9

FBC 25% Rule. The FBC limits how much of an existing roof can be repaired within a specific period of time 

before triggering the requirement to comply with the latest code, often referred to as the “25% Rule.” The 25% 

Rule has applied to construction in South Florida as far back as the 1957 South Florida Building Code. In the 

2001 and 2004 FBC, the 25% Rule only applied to buildings within a High-Velocity Hurricane Zone (HVHZ). 

In the 2007 FBC, the rule was modified slightly and adopted to be applicable to the rest of Florida. The 

applicability of the 25% Rule has differed somewhat for buildings within and outside the HVHZ, with changes 

made between the 5th Edition (2014) and 6th Edition (2017), as described below. 

5th Edition (2014) FBC. The 5th Edition (2014) versions of the rule are as follows:

" Areas outside the HVHZ: “Not more than 25 percent of the total roof area or roof section of any existing 

building or structure shall be repaired, replaced or recovered in any 12-month period unless the entire 

roofing system or roof section conforms to requirements of this code” (Section 708.1.1, FBCEB 2014).

" Areas within the HVHZ: “Not more than 25 percent of the total roof area or roof section of any existing 

building or structure shall be repaired, replaced or recovered in any 12-month period unless the entire 

existing roofing system or roof section is replaced to conform to requirements of this code” (Section 

1521.4, FBCB 2014). 

The distinction is that for areas outside the HVHZ, if more than 25 percent of the total roof area or roof 

section had to be repaired, replaced, or recovered in any 12-month period, the remainder of the roof only 

had to be replaced if it did not conform to the requirement of the current code. For areas in the HVHZ, if 

more than 25 percent of the total roof area or roof section had to be repaired, replaced, or recovered in any 

12-month period, the remainder of the roof or roof section had to be replaced to conform to the requirements 

of the code, regardless of whether it complied with the current code.

6th Edition (2017) FBC. In the 6th Edition (2017) FBC, the 25% Rule was revised for areas outside the HVHZ 

to make it consistent with how it is applied in the HVHZ. Therefore, if more than 25 percent of the total roof 

area or roof section has to be replaced or recovered in any 12-month period, the 6th Edition (2017) FBC 

requires the remainder of the roof or roof section to be replaced to conform to the requirements of the code, 

regardless of whether it complies with the current code (see FBCR Section R908.1.1, FBCB Sections 1511.1 

and 1521.4, and FBCEB Section 706.1.1).

Roof Sections: If a building roof contains multiple 

levels or is divided by, for example, parapet walls or 

expansion joints, each area is considered an individual 

roof section when applying the 25% Rule. Therefore, 

in accordance with the 6th Edition (2017) of the FBC, 

if more than 25 percent of the total roof area or roof 

section of a building has to be repaired or replaced, 

the entire roof or roof section has to be replaced to 

conform to the requirements of the code. Figures 

1 and 2 show examples of roof sections on two 

different buildings.

Figure 1: Example of residential building with two roof sections

Roof section 1

Roof section 2

Figure 2: Example of non-residential building with four roof 

sections

Roof section 1 Roof section 3

Roof section 4

Roof section 2

Florida Building Code Definitions 

Roof Section: A separation or division of a roof 

area by existing joints, parapet walls, flashing 

(excluding valleys), difference of elevation 

(excluding hips and ridges), roof type, or legal 

description, not including the roof area required 

for a proper tie-off with an existing system.

Source: 6th Edition (2017) FBC
Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) FBC FL-RA3 / May 2018 Page 3 of 9

Residential Wind Mitigation

When a roof covering system on a single-family dwelling is removed and replaced, the 6th Edition (2017) FBCR 

requires the following components to be investigated and subsequent measures to be taken if deficiencies 

are found: 

" Roof deck attachment – Several options are provided for improving the roof deck attachment.

" Enhanced underlayment (secondary water barriers) – Since the underlayment requirements for new 

construction have been improved, the secondary water barrier requirements now simply reference the 

applicable underlayment table for new construction.

" Roof-to-wall connections – Improvements to 

roof-to-wall connections are covered in Section 

R908.8.

As indicated in the text box titled “FBCR Wind 

Mitigation Requirements,” single-family residential 

structures permitted subject to the Florida Building 

Code are exempt from the residential wind 

mitigation requirements. The phrase “permitted 

subject to the Florida Building Code” means a 

building permitted to any version of the Florida 

Building Code (2001, 2004, 2007, 2010, 5th 

Edition [2014], or 6th Edition [2017]).

Additionally, the FBCR and FBCEB permit 

the investigation of the roof decking and any 

mitigation measures taken to be performed by a 

roofing contractor.

Roof Deck Attachment

An evaluation of the existing roof deck fastening is required to determine if mitigation is required. If the 

existing connections are found to be insufficient, specific supplemental fasteners are required at specific 

spacings. Supplemental fasteners must be ASTM F1667 RSRS-01 ring shank nails with the minimum 

dimensions specified in the FBCEB and FBCR. The number and minimum spacing of supplemental fasteners 

depend on the spacing of the existing fasteners as specified in Table R908.7.1.2 of the FBCR and shown in 

Table 1. Figure 3 is an illustration of a roof decking showing where supplemental fasteners are required and 

the required spacing.

FBCR Wind Mitigation Requirements

R908.7: When a roof covering on an existing 

site-built single-family residential structure is 

removed and replaced, the following procedures 

shall be permitted to be performed by the roofing 

contractor:

• Roof-decking attachment shall be as required by 

Section R908.7.1.

• A secondary water barrier shall be provided as 

required by Section R908.7.2.

Exception: Single-family residential structures 

permitted subject to the Florida Building Code are 

not required to comply with this section.

Source: 6th Edition (2017) FBCR

Table 1: Supplemental Fasteners at Panel Edges and Intermediate Framing (FBCR)

Existing Fasteners Existing Spacing

Vasd 110 mph or Less 

Supplemental Fastener 

Spacing Shall Be No 

Greater Than

Vasd Greater Than 110 

mph Supplemental 

Fastener Spacing Shall Be 

No Greater Than

Staples or 6d Any 6 inches on center b 6 inches on center b

8d clipped head, round 

head, smooth or ring shank

6 inches on center or 

less

None necessary None necessary

8d clipped head, round 

head, smooth or ring shank

Greater than 6 inches 

on center

6 inches on center a 6 inches on center a

a. Maximum spacing determined based on existing fasteners and supplemental fasteners.

b. Maximum spacing determined based on supplemental fasteners only.

Note: Vasd (nominal wind speed per FBC) shall be determined in accordance with Section 1609.3.1 of the Florida Building Code, Building or 

Section R301.2.1.3 of the Florida Building Code, Residential.

Source: Table R908.7.1.2 in the FBCR, modified slightly to define terms, available at https://www.floridabuilding.org
Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) FBC FL-RA3 / May 2018 Page 4 of 9

Florida Building Code Wind Speeds

Wind Speed, Vult: Ultimate design 

wind speeds. Vult is determined from 

the wind speed maps.

Wind Speed, Vasd: Nominal design 

wind speeds. Vasd is determined by 

multiplying Vult by √0.6. 

Source: 6th Edition (2017) FBC

Secondary Water Barriers

Criteria for the required secondary 

water barrier are addressed in Section 

R908.7.2 of the FBCR. Provisions for 

areas within and outside the HVHZ 

are provided separately; while the 

requirements for within and outside the 

HVHZ are generally similar, there are 

subtle differences. Additionally, the requirements also differ slightly depending on the type of roof covering 

being installed. Table 2 summarizes what qualifies as a secondary water barrier for asphalt shingle roofs that 

are removed and replaced in the HVHZ and outside the HVHZ. 

Figure 3: Example of roof decking showing placement and spacing of 

supplemental roof deck fasteners

Existing roof deck 

fastened with staples 

at varying spacing 

Add supplemental 

fasteners at 6 inches 

on center at panel 

edges and intermediate

framing

24 inches

6 inches (typical)

Existing roof

framing member

Table 2: Summary of Secondary Water Barrier Options for Asphalt Shingle Roofs

Roof Slope Material Details

Within High-Velocity Hurricane Zones

2:12 and greater Approved asphalt 

impregnated 30# felt 

underlayment or approved 

synthetic underlayment

(ASTM D226 Type II or 

ASTM D4869 Type IV)

• Single layer with 4-inch side lap

• 6-inch end laps

• Metal cap nails with a cap diameter of not less than 1-5/8

inches but no more than 2 inches and thickness of 32-gage

sheet metal

• Nails are required to be minimum 12 gauge, annular ring

shank nails having not less than 20 rings per inch, heads

not less than 3/8 inch (9.5 mm) in diameter, and lengths

sufficient to penetrate the thickness of plywood panel or

wood plank decking not less than 3/16 inch (4.8 mm), or

to penetrate into a 1-inch (25 mm) or greater thickness of

lumber not less than 1 inch

• Fasteners to be in a grid pattern of 12 inches between laps

• Fasteners at side and end laps at 6 inches on center

ASTM D1970 • Apply 4-inch-wide self-adhering strips over joints in roof

sheathing with one of the underlayment installation methods

and types identified in the FBC for the HVHZ over the entire

roof deck

Note: In the HVHZ, if the self-adhering membrane is to 

be applied over the entire roof, it must be applied over 

a mechanically fastened anchor sheet (using one of the 

underlayment materials and attachment methods described in 

the row above).
Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) FBC FL-RA3 / May 2018 Page 5 of 9

Table 2: Summary of Secondary Water Barrier Options for Asphalt Shingle Roofs (concluded)

Roof Slope Material Details

Outside High-Velocity Hurricane Zones

2:12 to less 

than 4:12

ASTM D226 Types I or II

ASTM D4869 Types II, III, 

or IV

ASTM D6757

• 

• 

• 

• 

Double layer with 19-inch side lap for all types

6-inch end laps offset 6 feet

Metal or plastic cap nails with a cap diameter of not less 

than 1 inch and thickness of 32-gage sheet metal

One row of fasteners in the field of the sheet at 12 inches 

on center

• Fasteners at side and end laps at 6 inches on center

ASTM D1970 • 

• 

Apply self-adhering membrane over the entire roof

Alternatively, apply 4-inch-wide self-adhering strips over 

joints in roof sheathing with one of the underlayment 

installation methods and types identified above over the 

entire roof deck

4:12 and greater ASTM D226 Type II

ASTM D4869 Type IV

ASTM D6757

• 

• 

• 

• 

• 

Single layer with 4-inch side lap for all types

6-inch end laps offset 6 feet

Metal or plastic cap nails with a cap diameter of not less 

than 1 inch and thickness of 32-gage sheet metal

Two staggered rows of fasteners in the field of the sheet 

with a maximum fastener spacing of 12 inches on center

Fasteners at side and end laps at 6 inches on center

ASTM D1970 • 

• 

Apply self-adhering membrane over the entire roof

Alternatively, apply 4-inch-wide self-adhering strips over 

joints in roof sheathing with one of the underlayment 

installation methods and types identified above over the 

entire roof deck

Source: Compiled from Sections R908.7 and 2 and Table R905.1.1 of the 6th Edition (2017) FBCR and Sections 1517.5.1, 1517.5.2, 1518.2, 1518.3, 

and 1518.4 of the 6th Edition (2017) FBCB.

For areas outside the HVHZ, Section R905.1.1 of the FBCR permits the use of a reinforced synthetic 

underlayment that is approved as an alternative to underlayment complying with ASTM D226 Type II. In 

addition, a minimum tear strength of 20 pounds in accordance with ASTM D1970 or ASTM D4533 is 

permitted as an alternative outside the HVHZ. This underlayment is required to be installed and attached 

in accordance with the requirements for the applicable roof covering and slope, except metal cap nails are 

required where the ultimate design wind speed, Vult, equals or exceeds 150 mph. In the HVHZ, a synthetic 

underlayment installed with tin tabs is permitted in accordance with Sections 1518.2, 1518.3, and 1518.4 of 

the FBCB.

Figures 4 through 8 illustrate some of the secondary water barrier methods that are summarized in Table 2.

Roof-to-Wall Connections

Improvements to roof-to-wall connections are covered in Section R908.8 of the FBCR and only apply to 

buildings located in the wind-borne debris region with an insured value of $300,000 or more, or if uninsured, 

have a just valuation for purposes of ad valorem taxation of $300,000 or more. The code requires roof-towall connections to be retrofitted only up to a 15 percent increase in the cost of reroofing. As with roof deck 

attachments and secondary water barriers, single-family residential structures permitted subject to the Florida 

Building Code are exempted from these requirements.
Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) FBC FL-RA3 / May 2018 Page 6 of 9

Figure 4: Example 1 – Outside the HVHZ

12 inches on center

One layer of ASTM 

D226 Type II, ASTM 

D4869 Type IV, or

ASTM D6757

Stagger rows

Metal drip

edge

Fascia Metal drip edge

MetaI or plastic cap nails. Cap diameter not less than 1 inch. 

Nail shank diameter not less than 0.083 inch for ring shank nails and 

0.091 inch for smooth shank nails. Metal cap thickness not less than 

32-gage sheet metal or 0.01 inch for power-driven fasteners. Plastic 

cap outside edge thickness not less than 0.035 inch.

4-foot x 8-foot roof sheathing

4 inches 6 inches on center

6-inch

end laps

Figure 5: Example 2 – Outside the HVHZ

4-foot x 8-foot roof sheathing

Metal drip

edge

Fascia Metal drip edge

Self-adhering polymer modified bitumen membrane 

complying with ASTM D1970 applied over the entire roof.

All laps to be in accordance with the manufacturer’s 

installation instructions.

Figure 6: Example 3 – Outside the HVHZ

4-inch-wide (minimum) 

self-adhering modified bitumen 

tape at sheathing joints

4 feet x 8 feet roof sheathing

12 inches on center

Stagger rows

6 inches on center 4 inches 

Metal drip

edge

Fascia Metal drip edge

MetaI or plastic cap nails. Cap diameter not less than 1 inch. 

Nail shank diameter not less than 0.083 inch for ring shank nails and 

0.091 inch for smooth shank nails. Metal cap thickness not less than 

32-gage sheet metal or 0.01 inch for power-driven fasteners. Plastic 

cap outside edge thickness not less than 0.035 inch. 

One layer of ASTM 

D226 Type II, ASTM 

D4869 Type IV, or

ASTM D6757

6-inch

end laps

Figure 7: Example 1 – Within the HVHZ

4-inch-wide (minimum) 

self-adhering modified bitumen 

tape at sheathing joints

4 feet x 8 feet roof sheathing

12 inches on center

Stagger rows

4 inches 

Metal drip

edge

Fascia Metal drip edge

MetaI cap nails. Cap diameter not less than 

1.625 inches nor more than 2 inches. Ring shank 

nails as specified by the HVHZ. Metal cap 

thickness not less than 32-gage sheet metal.

One layer of 30# felt

NOTE: A double layer

of ASTM D226 Type I 

with 19-inch lap is 

also permitted

6 inches on center

6-inch

end laps

Figure 8: Example 2 – Within the HVHZ

4-foot x 8-foot roof sheathing

12 inches on center

6-inch

end laps

Stagger rows

4 inches 

Metal drip

edge

Fascia Metal drip edge

MetaI cap nails. Cap diameter not less than 

1.625 inches nor more than 2 inches. Ring shank 

nails as specified by the HVHZ. Metal cap 

thickness not less than 32-gage sheet metal.

One layer of 

30# felt

6 inches on center
Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) FBC FL-RA3 / May 2018 Page 7 of 9

The FBCR and FBCEB codes provide prescriptive solutions for various roof configurations and wall types. They 

also address the most vulnerable locations by prioritizing mandated roof-to-wall retrofit expenditures. 

Commercial Wind Mitigation

While the wind mitigation provisions for commercial buildings are not as encompassing as those for singlefamily dwellings, the FBCEB requires certain roof components to be evaluated and potentially improved when 

the roof covering is replaced.

Section 707.3.2 of the FBCEB requires an evaluation of the roof diaphragm, connections of the roof 

diaphragm to roof framing members, and roof-to-wall connections when roofing materials are removed from 

more than 50 percent of the roof diaphragm or section. If the diaphragm and the connections specified are 

not capable of resisting 75 percent of the wind loads specified in the FBCB, they are required to be replaced 

or strengthened to meet those loads (refer to the text box titled “Roof Diaphragms Resisting Wind Loads”).

The 6th Edition (2017) FBCEB includes new exceptions to Section 707.3.2 shown in the text box. They are 

intended to apply to buildings that have been designed for wind loads that are comparable to modern wind 

load standards. The American Society of Civil Engineers (ASCE) Minimum Design Loads for Buildings and 

Other Structures (ASCE 7-88) and the 1991 Standard Building Code (SBCCI 1991) specified component and 

cladding loads comparable to the loads in modern codes and standards. When an evaluation is performed 

by a registered design professional confirming that the roof diaphragm, connections of the roof diaphragm to 

roof framing members, and roof-to-wall connections are in compliance with ASCE 7-88 or the 1991 Standard 

Building Code, the strengthening or replacing of these components is not required. 

Florida Building Code, Existing Building – Roof Diaphragms Resisting Wind Loads 

707.3.2 Roof diaphragms resisting wind loads in high-wind regions. Where roofing materials are 

removed from more than 50 percent of the roof diaphragm or section of a building located where the 

ultimate design wind speed, Vult, determined in accordance with Figure 1609.3(1) of the Florida Building 

Code, Building, is greater than 115 mph (51 m/s), as defined in Section 1609 (the High-Velocity Hurricane 

Zone shall comply with Section 1620) of the Florida Building Code, Building, roof diaphragms, connections 

of the roof diaphragm to roof framing members, and roof-to-wall connections shall be evaluated for the 

wind loads specified in the Florida Building Code, Building, including wind uplift. If the diaphragms and 

connections in their current condition are not capable of resisting at least 75 percent of those wind loads, 

they shall be replaced or strengthened in accordance with the loads specified in the Florida Building 

Code, Building.

Exceptions:

1. This section does not apply to buildings permitted subject to the Florida Building Code.

2. This section does not apply to buildings permitted subject to the 1991 Standard Building Code or 

later edition, or designed to the wind loading requirements of ASCE 7-88 or later editions, where an 

evaluation is performed by a registered design professional to confirm the roof diaphragm, connections 

of the roof diaphragm to roof framing members, and roof-to-wall connections are in compliance with 

the wind loading requirements of either of these standards or later editions.

3. Buildings with steel or concrete moment resisting frames shall only be required to have the roof 

diaphragm panels and diaphragm connections to framing members evaluated for wind uplift.

4. This section does not apply to site built single family dwellings. Site-built single-family dwellings shall 

comply with Sections 706.7 and 706.8.

5. This section does not apply to buildings permitted within the HVHZ after January 1, 1994, subject to 

the 1994 South Florida Building Code, or later editions, or where the building’s wind design is based 

on the wind loading requirements of ASCE 7-88 or later editions. 

Source: 6th Edition (2017) FBCEB
Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) FBC FL-RA3 / May 2018 Page 8 of 9

Similar to the mitigation provisions for residential construction, Section 707.3.2 does not apply to buildings 

permitted subject to the Florida Building Code. In addition, the provisions do not apply to site-built singlefamily dwellings, as those structures are addressed in Section R908.7 of the FBCR (also covered in Section 

706.7 of the FBCEB).

Buildings with moment-resisting frames do not have roof-to-wall connections and are therefore only required to 

have roof diaphragm panels and diaphragm connections to framing members evaluated for wind uplift.

References and Resources 

References

ASCE (American Society of Civil Engineers). 1988. Minimum Design Loads for Buildings and Other Structures.

ASCE Standard ASCE 7-88.

ASTM (American Society for Testing and Materials). 2009. Specification for Asphalt-Saturated Organic Felt Used 

in Roofing and Waterproofing. D226 / D226M-09.

ASTM. 2015. Specification for Self-Adhering Polymer Modified Bitumen Sheet Materials Used as Steep Roofing 

Underlayment for Ice Dam Protection. D1970 / D1970M-15.

ASTM. 2015. Specification for Driven Fasteners, Nails, Spikes, and Staples. F1667-15.

ASTM. 2015. Standard Test Method for Trapezoid Tearing Strength of Geotextiles. D4533 / D4533M-15.

ASTM. 2016. Specification for Asphalt-Saturated Organic Felt Underlayment Used in Steep Slope Roofing.

D4869 / D4869M-16a.

ASTM. 2016. Standard Specification for Inorganic Underlayment for Use with Steep Slope Roofing Products.

D6757-2016. 

FBC (Florida Building Code). 2017. “Florida Department of Business & Professional Regulation” Web page. 

https://www.floridabuilding.org/bc/bc_default.aspx. Codes are available from ICC at https://codes.

iccsafe.org/public/collections/Florida.

FEMA (Federal Emergency Management Agency). 2018. Public Assistance Program and Policy Guide. FP-104-

009-2. https://www.fema.gov/media-library/assets/documents/111781.

SBCCI (Southern Building Code Congress International). 1991. Standard Building Code.

Resources

FEMA (Federal Emergency Management Agency). 2009. Local Officials Guide for Coastal Construction. FEMA 

P-762. https://www.fema.gov/media-library/assets/documents/16036.

FEMA. 2010. Home Builder’s Guide to Coastal Construction. FEMA P-499. https://www.fema.gov/media-library/

assets/documents/6131.

FEMA. 2010. Wind Retrofit Guide for Residential Buildings. FEMA P-804. https://www.fema.gov/media-library/

assets/documents/21082.

FEMA. 2011. Coastal Construction Manual: Principles and Practices of Planning, Siting, Designing, Constructing, 

and Maintaining Residential Buildings in Coastal Areas, 4th Edition. FEMA P-55. https://www.fema.gov/

media-library/assets/documents/3293. 

Useful Links

FBC (Florida Building Code), multiple years and editions, can be obtained from ICC at https://codes.iccsafe.

org/public/collections/Florida.

Insurance Institute for Business & Home Safety (IBHS) Fortified Home Standards and Technical Bulletins. 

https://disastersafety.org/fortified/resources/.
Mitigation Triggers for Roof Repair and Replacement in the 6th Edition (2017) FBC FL-RA3 / May 2018 Page 9 of 9

For more information, see the FEMA Building Science 

Frequently Asked Questions website at http://www.fema.

gov/frequently-asked-questions-building-science.

If you have any additional questions on FEMA Building 

Science Publications, contact the helpline at FEMABuildingsciencehelp@fema.dhs.gov or 866-927-2104.

You may also sign up for the FEMA Building Science email 

subscription, which is updated with publication releases 

and FEMA Building Science activities. Subscribe at https://

service.govdelivery.com/accounts/USDHSFEMA/subscriber/

new?topic_id=USDHSFEMA_193.

Visit the Building Science Branch of the Risk Management 

Directorate at FEMA’s Federal Insurance and Mitigation 

Administration at https://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

Email: FEMA-PublicationsWarehouse@fema.dhs.gov

Additional FEMA documents can be 

found in the FEMA Library at 

https://www.fema.gov/media-library/

resources.

Please scan this QR code 

to visit the FEMA Building 

Science web page.