Mitigation Assessment Team Report 

Hurricane Ivan in 
Alabama and Florida 

Observations, Recommendations, 
and Technical Guidance 

FEMA 489 / August 2005 


FEMA 



In response to Hurricane Ivan, the Federal Emergency Management Agency (FEMA) 
deployed a Mitigation Assessment Team (MAT) to evaluate and assess damage from the 
hurricane and provide observations, conclusions, and recommendations on the performance 
of buildings and other structures impacted by wind and flood forces. The MAT included 
engineers and other experts from FEMA Headquarters and the Regional Offices and from 
the design and construction industry. The conclusions and recommendations of this Report 
are intended to provide decision-makers information and technical guidance that can be 
used to reduce future hurricane damage. 
About the Cover 

The cover photograph is a NASA image courtesy of the Moderate Resolution Imaging 
Spectroradiometer (MODIS) Land Rapid Response Team at the National Aeronautics 
and Space Administrations (NASA) Goddard Space Flight Center. The MODIS 
instrument flying aboard NASAs Aqua satellite captured this true-color image of 
Hurricane Ivan on September 15, 2004, at 2:50 p.m. Eastern Daylight Time. At the time 
this image was taken, Ivan was located approximately 170 miles south of the Alabama 
coastline and was moving northward at 14 miles per hour. Ivan made landfall as a 
Category 3 storm with maximum sustained winds near 121 mph with higher gusts. 
(IMAGE COURTESY OF NASA EARTH OBSERVATORY) 


I 



M I T I G A T I O N A S S E S S M E N T T E A M R E P O R T 

Hurricane Ivan in 
Alabama and Florida 

Observations, Recommendations, 
and Technical Guidance 

FEMA 489 /August 2005 


FEMA 



Members of the Mitigation Assessment Team 

FEMA MAT Members: 

John Ingargiola
FEMA Headquarters 

Mike Robinson 

FEMA Headquarters 

Emily Hirsch 

FEMA Headquarters 

Stanley Houston 

FEMA, Region IV 

Jhun de la Cruz 

FEMA Headquarters 

Shabbar Saifee 

FEMA DFO 

MAT Members: 

Ted Van Kirk, PE 

Dewberry & Davis 

Chris Jones, PE 

Dan Deegan, CFM 

PBS&J 

Thomas Smith, AIA, RRC, CSI 

TLSmith Consulting, Inc. 

Jim Delahay, PE 

LBYD, Inc. 

Arthur Hooks, IV 

PBS&J 

Jack Burleson, PE 

International Code Council 

Timothy Reinhold, PE 

Institute of Building & Home Safety 

Scott Douglas 
University of South Alabama
Coastal Transportation Engineering
Research and Education Center 

Suzanne Nicholson 

Dewberry & Davis 

Julie Liptak 

Greenhorne & OMara 

Wanda Rizer 

design4impact 

John Squerciati 

Dewberry & Davis 

Scott Tezak, PE 

URS 

Bill Coulbourne, PE 

URS 

Jimmy Yeung, PhD, PE 

Greenhorne & OMara 





Dedication 

Jim Delahay was a person you did not forget once 
you met him. He was an outstanding engineer, a 
dedicated professional, and a true friend. He was 
also an expert in wind-resistant design, structural 
engineering, and building codes and standards. 
Although a young man, he was well-known 
throughout the engineering profession, and he 
was recognized by his peers on many occasions. 
Among his many accomplishments: Jim was the 
first engineer elected as chairman of the Struc
tural 
Committee of the International Code Council; 
Jim was chair of the Code Advisory Committee of the 
National Council of Structural Engineers Associa
tions; 
he was co-chair of the ASCE 7 Wind Load Task 
Committee; he was past president of the Applied 
Technology Council; and he was president and CEO of Lane Bishop 
York Delahay (LBYD, Inc.) of Birmingham, Alabama. In 2003, he was 
named a Distinguished Engineering Fellow by the University of Ala
bama 
College of Engineering, from which he earned both his BS and 
MS degrees in Civil Engineering. 

Jim made his first post-storm deployment for FEMA after Hurricane 
Ivan, and he was an indispensable member of the Hurricane Ivan Miti
gation 
Assessment Team. We all learned from Jim, and this report is 
all the better because of him. Those who read and use this report will 
benefit directly from Jims expertise and knowledge. 

FEMA and the Hurricane Ivan Mitigation Assessment Team are hon
ored 
to dedicate this report to the memory of Jim, who passed away 
suddenly on April 16, 2005. 


Jim Delahay (1958-2005) 



H 

Tropical Cyclone Report, Hurricane Ivan, 2- 

Hurricane Ivan made landfall on Thursday, September 16, 2004, just 

west of Gulf Shores, Alabama. The hurricane brought 1-minute sus
tained wind speeds (over open water) of 121 miles per hour (mph) (as 

estimated by the National Hurricane Center [NHC]), torrential rains, 

coastal storm surge flooding of 10 to 16 feet above normal high tide, 

and large and battering waves along the western Florida Panhandle 

and Alabama coastline. In its 

construction requirements, and building practices and materials. This 

report presents the MATs observations, conclusions, and recommen 

- 

dations as a result of those field investigations. 

26 September 2004 

(NHC, 16 December 2004, Revised 6 January 2005), 

the NHC categorized Hurricane Ivan as a Category 3 hurricane, as 

measured by the Saffir-Simpson Hurricane Scale. The National Weath 

- 

er Service reported that from September 15 through 16, Ivan spawned 

23 tornadoes in Florida and produced as much as 10 to 15 inches of 

rainfall in some areas (National Weather Service Mobile  Pensacola, 

Powerful Hurricane Ivan Slams the US Central Gulf Coast as Upper 

Category-3 Storm, 

www.srh.noaa.gov/mob/ivan_page/Ivan-main.ht 

m 

). 

After landfall, Hurricane Ivan gradually weakened over the next week, 

moving northeastward over the Southeastern United States and even 

- 

tually emerging off the Delmarva Peninsula as an extratropical low on 
On September 18, 2005, the Federal Emergency Management Agencys 
(MAT) to Alabama and Florida to evaluate building performance dur
ing Hurricane Ivan and the adequacy of current building codes, other 


i 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

Executive 
Summary 





EXECUTIVE SUMMARY 

ii 

 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

Several maps in Chapter 1 illustrate the path of the storm, the depth 
of storm surge along the path, and the wind field estimates. Hurricane 
Ivan approximated a design flood event on the barrier islands and 
exceeded design flood conditions in sound and back bay areas. This 
provided a good opportunity to assess the adequacy of National Flood 
Insurance Program (NFIP) floodplain management requirements 
as well as current construction practices in resisting storm surge and 
wave damage. FEMA was particularly interested in evaluating damages 
to buildings in coastal A Zones where V-Zone construction methods 
are not required. 

Although the NHC categorized Hurricane Ivan as a Category 3 hurri
cane, 
surface observation sites throughout the coastal region provided 
data that indicate that most of the region impacted by the storm likely 
experienced Category 1 intensity winds with some areas near the Ala
bama-
Florida border experiencing Category 2 intensity winds. None of 
the surface wind measurements for overland conditions correspond to 
Category 3 intensity winds. Although Hurricane Ivan was not a design 
wind event when analyzed with respect to the 2001 Florida Building 
Code (FBC) or the 2000/2003 International Building Code (IBC) and 
International Residential Code (IRC), it caused extensive wind-related 
damage to buildings constructed under earlier codes. 

Floodplain Management Regulations 
in Alabama and Florida 

All of the communities visited by the MAT participate in the 
NFIP and have adopted floodplain management regulations 
that meet or exceed minimum NFIP requirements. Up until 
2000, these requirements generally were contained only in commu
nity 
floodplain management ordinances. Starting in 2000, however, 
flood-resistant provisions and floodplain management requirements 
began to be incorporated into model building codes used in the af
fected 
areas (e.g., the IBC, the IRC, and the FBC). 

The MAT determined that the area flooded by Ivan exceeded the 
Special Flood Hazard Area (SFHA) shown on the effective Flood In
surance 
Rate Maps (FIRMs) for many communities, from Gulf Shores, 
Alabama, to Okaloosa County, Florida, and that flood elevations in 
many areas exceeded the 100-year Base Flood Elevations (BFEs) de
picted 
on the FIRMs by 2 to 4 feet. The initial flood studies for these 
communities were completed in the mid 1970s and were based on 
National Oceanographic and Atmospheric Administration (NOAA) 
tide gauge frequency analyses. The next studies were completed in the 



EXECUTIVE SUMMARY 

mid 1980s and were based on FEMAs storm surge model. This second 
round of flood studies also mapped wave crest elevations (as opposed 
to stillwater elevations), due in large part to observed damages to new 
construction at the time of Hurricane Frederic (1979). For the most 
part, this second round of studies resulted in decreased BFEs and a 
smaller SFHA when compared to the studies completed in the 1970s. 
The most recent flood studies were completed in the late 1990s (af
ter 
Hurricane Opal) and added wave setup and extended the V Zone 
to include the primary frontal dune. The most recent studies gener
ally 
increased the BFEs and the SFHA when compared to the studies 
completed in the 1980s, but not to the extent of the studies from the 
1970s. The coastal FIRM changes over time likely resulted in a variety 
of coastal construction practices over the years, as most buildings were 
constructed to the minimum regulatory requirements, and could have 
contributed to flood and erosion damages the MAT observed. 

Building Codes and Standards in Alabama 
and Florida 

Alabama adopts building codes on a statewide basis only for 
state-owned buildings, such as schools. Local jurisdictions de
termine 
the adoption of building codes for private buildings. 
All Alabama jurisdictions have traditionally adopted editions of the 
Standard Building Code (SBC) published by the Southern Building 
Code Congress International. The City of Orange Beach adopted the 
2003 IBC in the summer of 2004, just prior to Hurricane Ivan. The 
City of Gulf Shores adopted the 2003 IBC as an emergency measure 
after Hurricane Ivan  to improve the quality of the reconstruction. 
Most other affected Alabama communities, such as those in unincor
porated 
Baldwin County, were still enforcing the 1997 or 1999 SBC at 
the time of Hurricane Ivan. 

In the Florida Panhandle, the SBC  with local amendments  was used 
to regulate construction until early 2002 when the FBC 2001 Edition 
was adopted statewide. The FBC, administered by the Florida Building 
Commission, governs the design and construction of residential and 
non-residential (commercial, industrial, critical/essential, etc.) build
ings 
in Florida. In December 2004, the Florida Building Commission 
completed the 2004 Edition of the FBC. However, additional changes 
to the 2004 Edition are being made in response to the 2004 hurricanes, 
and the 2004 Edition will not replace the earlier edition until fall 2005. 
Buildings constructed along Floridas Gulf of Mexico shoreline were 
also subject to the provisions of the states Coastal Construction Con
trol 
Line, which have been incorporated into the FBC. 



Damage Assessment Observations 

Flood 

Because Hurricane Ivan approximated or exceeded a design flood 
event, the resultant storm damage provides valuable evidence about 
the adequacy of NFIP maps, floodplain management requirements, the 
reliability of the A-Zone delineation in coastal areas, building codes, 
and design practices. Flood levels from Hurricane Ivan exceeded the 
mapped BFEs throughout many bays and sounds by several feet. Flood 
levels along Gulf-front shorelines also exceeded the mapped BFEs but 
to a lesser extent, and the flooding extended beyond the SFHAs in 
most communities investigated. Many of the barrier islands were sub
merged 
and overwashed. Buildings constructed before the adoption of 
the NFIP and many buildings located outside the SFHA were severely 
impacted by the high storm-surge elevations and increased inundation 
area caused by Ivan. 

Floodborne debris and wave damage (characteristic of V-Zone damage) 
was extensive in A Zones, especially along bay and sound shorelines. 
Floodborne debris from buildings, docks, and piers destroyed lowerlevel 
enclosures, stairs, and some buildings. Buildings that were not 
elevated above the wave crest elevation were damaged during Ivan not 
only by storm surge, but also by waves and floodborne debris. 

Erosion was severe along the barrier islands of Alabama and Florida. 
Areas that had wide beaches and dunes before Ivan were less impact
ed 
than those with smaller, narrower beaches and dunes. Erosion 
along bay and sound shorelines was generally minimal, and structur
al 
damage there was predominantly due to storm surge, waves, and 
floodborne debris. The erosion along the barrier islands undermined 
shallow foundations and caused many buildings to collapse. Many ar
eas 
had suffered beach and dune erosion during past coastal storm 
events, which made the buildings in those areas more vulnerable to 
flood and erosion impacts from Ivan. 

Wind 

Although structural system failures tend to be perceived by the public 
and the building industry as the dominant issue of concern, it is clear that 
for buildings built in accordance with the 2001 FBC or the 2000/2003 
IBC, structural issues have, in general, been addressed by the codes. 
Now, the arena in which improvements can and must be made are those 



related to water intrusion and integrity of the building envelope. Pro
tecting 
the integrity of the building envelope is important not only to 
minimize losses and damages to building contents, but also to prevent 
full internal pressurization and progressive failure of buildings. 

Extensive damage to the building envelope with associated minor 
structural system damage was observed at many residential buildings 
even though Hurricane Ivan was not considered to be a design wind 
event when evaluating wind speeds and wind pressures from the 2001 
FBC or the 2000/2003 IBC and IRC. However, in the areas around 
Gulf Shores, Orange Beach, and Pensacola Beach, existing building 
stock constructed to the 1979 to 1997 SBC can be said to have experi
enced 
a design wind event, and, thus, damage observed is related to 
the design parameters used at the times these codes were enforced. 

Widespread building envelope damage was observed by the MAT 
throughout the affected area. Performance of building envelopes was 
generally poor and led to widespread damage to the interiors of resi
dences, 
businesses, and critical/essential facilities. 

Windborne debris damage was not widespread. ASCE 7 predicts that 
significant windborne debris damage will begin in the 120-mph range 
in inland areas and in the 110-mph range when buildings are within 
one mile of the coast. Since Ivans gust speeds were generally below 
that level, it is expected that glazing damage during Ivan would be less 
common than in other more powerful storms such as Hurricane Char
ley. 
Given that the actual wind speeds were below current code level 
wind speeds, the occasional damage to the structural elements and 
the widespread damage to building envelopes can be characterized as 
wind-related damage caused by inadequate design, old construction 
methods, outdated design codes and methods, lack of maintenance, 
and/or poor construction/code enforcement. Wind damage to the 
contents of residential and commercial buildings, and critical/essen
tial 
facilities due to these failures is preventable. 

Recommendations 

The recommendations in this report are based solely on the ob
servations 
and conclusions of the MAT, and are intended to 
assist the State of Alabama, the State of Florida, local communi
ties, 
businesses, and individuals in the reconstruction process and to 
help reduce damage and impact from future natural events similar 
to Hurricane Ivan. The report and recommendations also will help 
FEMA assess the adequacy of its flood hazard mapping and floodplain 




management requirements and determine whether changes are 
needed or additional guidance required. The general recommenda
tions 
are presented in Sections 8.1 and 8.2. They relate to policies 
and education/outreach that are needed to ensure that designers, 
contractors, and building officials understand the requirements for 
disaster-resistant construction in hurricane-prone regions. Proposed 
changes to codes and standards are presented in Section 8.3. 

Specific recommendations for improving the performance of the build
ing 
structural system and envelope, and the protection of critical and 
essential facilities (to prevent loss of function) are provided in Chap
ter 
8. Implementing these specific recommendations, in combination 
with the general recommendations of Section 8.1 and 8.2 and the 
code and standard recommendations of Section 8.3, will significantly 
improve the ability of buildings to resist damage from hurricanes. Rec
ommendations 
specific to structural issues, building envelope issues, 
critical and essential facilities, and education and outreach have also 
been provided. 

As the people of Alabama and Florida rebuild their lives, homes, and 
businesses, there are a number of ways they can minimize the effects 
of future hurricanes, including: 

Flood-related 

 Elevate all new construction (including substantially improved 
structures and replacement of substantially damaged structures) in 
coastal A Zones with the bottom of the lowest horizontal supporting 
member above the base flood level. 

 Require freeboard for all structures in all flood hazard zones with 
the amount varying with building importance (see ASCE 7-05 and 
ASCE 24-05 for building importance classification and freeboard 
requirements) and anticipated exposure to wave effects. 

 Require V-Zone design and construction for new construction in 
coastal A Zones subject to erosion, scour, velocity flow, and/or wave 
heights greater than 1.5 feet. 

 Use a deep pile and/or column foundation anywhere on a barrier 
island, if erosion/or scour are possible. 

 For sites near bay or sound shorelines, foundation selection 
should be based on several factors: erodibility of the soil; exposure 
to damaging waves (> 1.5 ft high); potential for velocity flow; 
potential for floodborne debris; and required resistance to lateral 
flood and wind forces. 



 Use pier foundations only where soil characteristics and flood 
conditions permit. If there are any doubts as to the appropriate 
foundation to use near bay and sound shorelines, elevate the 
building at least one story above grade on piles or another deeply 
embedded open foundation, and leave the area below free of 
obstructions or enclose it with breakaway walls. 

 Design foundations and structures to withstand loads from 
floodborne debris during a base flood event (100-year). 

 For barrier island sites outside the V Zone, the ground level floor 
of a multi-story building (typically used for vehicle parking and 
building access) should either: 1) use a lowest floor slab or floor 
system that will not collapse and can support all design loads, if 
undermined, or 2) use a slab or floor system that will collapse and 
break into small pieces if undermined. 

 Elevate heating, ventilation, and air conditioning equipment above 
the BFE, and preferably to the same elevation as the lowest floor of 
a building. The equipment should be supported to prevent damage 
from flooding and fastened to resist blow-off from high winds. The 
preferred approach is a cantilevered platform. 

 Ensure that breakaway walls are designed and built to break away 
cleanly and do not cause additional damage to the building. 
Minimize the size of any enclosure to the amount necessary for 
parking and building access. 

 Either elevate pools above the BFE on a pile foundation (and 
design the pool without side support from soil), or install 
a frangible (breakaway) pool at grade level and consider it 
expendable. Do not rely on a bulkhead to protect the pool during 
a severe storm. 

 Subject to local and state regulations for coastal armoring, assume 
that only heavy walls will provide protection during a severe storm, 
and note that even those may be overtopped by surge and waves. 
Consider lightweight bulkheads as temporary structures that may 
provide protection during minor storms, but which will likely fail 
during a major storm. 

Wind-related 

 Design and construct facilities to at least the minimum design 
requirements in the 2003 IBC in Alabama and the 2001 FBC and 
the 2004 FBC (after it becomes effective in the fall of 2005) in 
Florida. 



 When renovating or remodeling for structural or building envelope 
improvements (both residential and commercial), involve a 
structural engineer/design professional/licensed contractor in the 
design and planning. 

 Assure code compliance through increased enforcement of 
construction inspection requirements such as the Florida Threshold 
Inspection Law or the IBC Special Inspections Provisions. 

 Perform follow-up inspections after a hurricane to look for moisture 
that may affect the structure or building envelope. 

 Use the necessity of roof repairs to damaged buildings as an 
opportunity to significantly increase the future wind resistance of 
the structure. 

The following recommendations are specifically provided for state and 
Federal government agencies: 

 Re-evaluate the methodology to determine flood zones and flood 
elevations in coastal areas to address the inconsistencies between 
observed flood elevations (and damages) and BFEs (and anticipated 
damages). 

 Re-evaluate the storm surge data and modeling procedures that 
served as the basis for the effective FIRMs. 

 Use Hurricane Ivan tide levels, inundation limits, and areas subject 
to wave effects as proxies for reconstruction guidance until such 
time as new, up-to-date regulatory studies and maps can be prepared 
and adopted. 

 Allocate resources to hardening, providing backup power and 
data storage to NOAA/NWSs surface weather monitoring systems, 
including the Automated Surface Observing System (ASOS) 
located in hurricane-prone regions. 

 Continue to fund the development of several different tools for 
estimating and mapping wind fields associated with hurricanes 
and for making these products available to the public as quickly as 
possible after a hurricane strikes. 

Additional recommendations and mitigation measures for design pro
fessionals, 
building officials, contractors, homeowners, and business 
owners are presented in Chapter 8, including: 

 Improving the performance of building structural and envelope 
systems through proper design of the continuous load path 



 Improving quality control and inspections 

 Retrofitting existing residential and commercial buildings from 
the roof decks to the foundations 

 Improving the performance of critical and essential facilities 
(including shelters) 

 Improving design and construction guidance 

 Improving public education and outreach 



xi 

MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

Table of Contents 

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

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

1.1 Hurricane Ivan  The Event ...........................................................................................1-1 

1.1.1 Storm Surge Analysis and Discussion .............................................................1-6 

1.1.2 Wind Analysis and Discussion .......................................................................1-22 

1.2 Historical Hurricanes (Frequency of Hurricanes and Tropical 
Storms in Eastern Coastal Alabama and Florida Panhandle) ....................................1-29 

1.3 FEMA Mitigation Assessment Teams ...........................................................................1-31 

1.3.1 Methodology ..................................................................................................1-31 

1.3.2 Team Composition .........................................................................................1-32 

2 Floodplain Management Regulations and Building Codes 
and Standards ........................................................................................................... 2-1 

2.1 Floodplain Management Regulations ...........................................................................2-1 

2.1.1 Flood Studies, Flood Maps, and Floodplain Management 
Regulations .......................................................................................................2-3 

2.1.2 Higher Regulatory Standards ..........................................................................2-5 

2.1.3 Relating Observed Flood Damages to the FIRMs ..........................................2-5 

2.1.3.1 Baldwin County, Alabama ..............................................................2-6 

2.1.3.2 Santa Rosa County, Florida ..........................................................2-10 

2.2 Building Codes and Standards .....................................................................................2-17 

2.2.1 Flood Requirements in Building Codes and Standards - 
Alabama ..........................................................................................................2-17 



TABLE OF CONTENTS 

xii 

 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

2.2.1.1 Flood Provisions in the IBC (2003) ............................................2-18 

2.2.1.2 Flood Provisions in the IRC (2003) ............................................2-18 

2.2.1.3 Flood Requirements in ASCE 7 ...................................................2-18 

2.2.1.4 Flood Requirements in ASCE 24 .................................................2-18 

2.2.1.5 Coastal Construction Control Line (Alabama) ..........................2-19 

2.2.2 Flood Requirements in Building Codes and Standards  
Florida .............................................................................................................2-20 

2.2.2.1 Flood Provisions in the FBC (2004 Edition) ..............................2-20 

2.2.2.2 Coastal Construction Control Line (Florida) ............................2-20 

2.2.3 Wind Requirements in Building Codes and Standards  
Alabama ..........................................................................................................2-22 

2.2.3.1 Comparing Design Wind Speeds ................................................2-22 

2.2.3.2 Comparing Design Wind Pressures .............................................2-24 

2.2.4 Wind Requirements in Building Codes and Standards  
Florida .............................................................................................................2-26 

2.2.4.1 Comparing Design Wind Speeds ................................................2-28 

2.2.4.2 Comparing Calculated Wind Pressures ......................................2-30 

2.2.4.3 Comparing Debris Impact Requirements ..................................2-32 

2.2.4.4 High-Wind Elements of the Code ...............................................2-33 

3 GENERAL CHARACTERIZATION OF DAMAGE .......................................................... 3-1 

3.1 Flood Effects ....................................................................................................................3-1 

3.1.1 Flood Effects on One- and Two-Family Housing ............................................3-2 

3.1.2 Flood Effects on Multi-Family Housing ..........................................................3-9 

3.2 Wind Effects ..................................................................................................................3-13 

3.2.1 Summary of Damage Types ...........................................................................3-13 

3.2.2 Wind Effects on One- and Two-Family Housing ..........................................3-15 

3.2.3 Wind Effects on Multi-Family Housing .........................................................3-16 

3.2.4 Wind Effects on Commercial Buildings .......................................................3-18 

3.2.5 Wind Effects on Critical/Essential Facilities ................................................3-19 

3.3 Lessons Learned and Best Practices ............................................................................3-20 



TABLE OF CONTENTS 

4 STRUCTURAL SYSTEMS PERFORMANCE ............................................................... 4-1 

4.1 Flood 4-1 

4.1.1 Single-Family Residential Buildings ................................................................4-1 

4.1.1.1 Pile Foundations ..................................................................................4-2 

4.1.1.2 Slab on Grade .....................................................................................4-12 

4.1.1.3 Stem Walls ..........................................................................................4-15 

4.1.1.4 Piers ....................................................................................................4-17 

4.1.2 Multi-Family Residential Buildings ...............................................................4-21 

4.1.2.1 Shallow Foundations ..........................................................................4-21 

4.1.2.2 Pile Foundations ................................................................................4-27 

4.1.3 Miscellaneous Structures ...............................................................................4-32 

4.1.3.1 Bulkheads ...........................................................................................4-32 

4.1.3.2 Non-Structural Slabs ..........................................................................4-35 

4.1.3.3 Breakaway Walls .................................................................................4-37 

4.1.3.4 Utilities ................................................................................................4-39 

4.1.3.5 Stairs ....................................................................................................4-44 

4.1.4 Debris Impacts ................................................................................................4-45 

4.2 Wind ..............................................................................................................................4-50 

4.2.1 Wood Frames ..................................................................................................4-50 

4.2.2 Concrete Buildings ........................................................................................4-59 

4.2.3 Commercial Buildings ...................................................................................4-59 

4.2.4 Pre-Engineered Metal Buildings ...................................................................4-60 

4.2.5 Accessory Structures ......................................................................................4-62 

5 BUILDING ENVELOPE PERFORMANCE .................................................................... 5-1 

5.1 Sheathing on the Underside of Elevated Buildings ......................................................5-2 

5.2 Doors ...............................................................................................................................5-4 

5.2.1 Personnel Door Damage .................................................................................5-4 

5.2.2 Garage Door Damage ......................................................................................5-6 

5.2.3 Rolling and Sectional Door Damage ..............................................................5-7 

5.3 Non-Load-Bearing Walls, Wall Coverings, and Soffits ..................................................5-7 



5.3.1 Non-Load-Bearing Walls ..................................................................................5-7 

5.3.2 Wall Coverings and Soffits .............................................................................5-23 

5.4 Roof Systems ..................................................................................................................5-33 

5.4.1 Asphalt Shingles .............................................................................................5-33 

5.4.2 Tile ..................................................................................................................5-36 

5.4.3 Metal Panel and Shingle Roofs .....................................................................5-44 

5.4.4 Low-slope Membrane Systems .......................................................................5-46 

5.5 Windows, Shutters, and Skylights .................................................................................5-51 

5.5.1 Unprotected Glazing .....................................................................................5-51 

5.5.2 Protected Glazing ...........................................................................................5-54 

5.5.3 Skylights ..........................................................................................................5-56 

5.6 Exterior Mechanical and Electrical Equipment Damage ...........................................5-57 

5.6.1 Rooftop HVAC Equipment ............................................................................5-58 

5.6.2 Electrical and Communications Equipment ................................................5-62 

6 PERFORMANCE OF CRITICAL AND ESSENTIAL FACILITIES .................................. 6-1 

6.1 Emergency Operation Centers ......................................................................................6-2 

6.1.1 General Damage ..............................................................................................6-2 

6.1.2 Functional Loss ................................................................................................6-3 

6.2 Hospitals ..........................................................................................................................6-4 

6.2.1 General Damage ..............................................................................................6-4 

6.2.2 Functional Loss ................................................................................................6-5 

6.2.3 Best Practices - Hospitals .................................................................................6-7 

6.3 Schools .............................................................................................................................6-7 

6.3.1 General Damage ..............................................................................................6-8 

6.3.2 Functional Loss ..............................................................................................6-10 

6.4 Shelters ..........................................................................................................................6-10 

6.4.1 General Damage ............................................................................................6-10 

6.4.2 Functional Loss ..............................................................................................6-11 



7 CONCLUSIONS ........................................................................................................... 7-1 

7.1 Flood Hazard Conclusions .............................................................................................7-1 

7.1.1 Lowest Floor Elevations ...................................................................................7-4 

7.1.2 Foundations and Structures ............................................................................7-6 

7.1.3 Piers and Docks ................................................................................................7-6 

7.1.4 Construction Features beneath Elevated Buildings .......................................7-7 

7.1.5 Pools and Bulkheads ........................................................................................7-8 

7.1.6 Utilities .............................................................................................................7-9 

7.2 Wind Hazard Conclusions ............................................................................................7-10 

7.2.1 Building Performance and Compliance with the 
Building Codes, Statutes, and Regulatory Requirements 
of the States of Alabama and Florida ............................................................7-12 

7.2.2 Performance of Structural Systems (Residential and 
Commercial Construction) ...........................................................................7-15 

7.2.2.1 Internal Pressures .........................................................................7-15 

7.2.2.2 Wind Mitigation for Existing Buildings ......................................7-17 

7.2.3 Performance of Building Envelope, Mechanical and 
Electrical Equipment ....................................................................................7-18 

7.2.4 The Need for High-Wind Design and Construction 
Guidance ........................................................................................................7-27 

7.2.5 Performance of Critical and Essential Facilities 
(Including Shelters) ......................................................................................7-27 

8 RECOMMENDATIONS ................................................................................................ 8-1 

8.1 Flood Related Recommendations ..................................................................................8-1 

8.1.1 General Hazard Identification Recommendations ........................................8-1 

8.1.2 Design Guidance ..............................................................................................8-2 

8.1.3 Foundation Recommendations .......................................................................8-2 

8.1.4 Building Utilities ..............................................................................................8-6 

8.1.5 Building Access Structures and Enclosures beneath 
Elevated Buildings ............................................................................................8-7 

8.1.6 Pools and Bulkheads ........................................................................................8-8 

8.1.7 Public Outreach and Education .....................................................................8-8 

8.2 Wind Recommendations ..............................................................................................8-14 



8.2.1 Proposed Changes to Codes and Statutes ....................................................8-15 

8.2.1.1 Statutory Building Code ProvisionsAlabama ..........................8-15 

8.2.1.2 Statutory Building Code ProvisionsFlorida ............................8-16 

8.2.1.3 Reference StandardsASCE 7 ....................................................8-17 

8.2.2 Architectural, Mechanical, and Electrical ....................................................8-17 

APPENDICES 

Appendix A References 

Appendix B Acknowledgments 

Appendix C Acronyms and Abbreviations 

Appendix D FEMA Recovery Advisories 

Appendix E Ivan Flood Recovery Maps 

Appendix F Orange Beach High-Rise Study 


TABLES 

Chapter 1 

Table 1-1. Wind Speeds of the Saffir-Simpson Hurricane Scale ........................................1-6 

Table 1-2. Comparison of HWMs and BFEs for MAT Investigation Sites ...........................1-8 

Table 1-3. Estimated Maximum 3-Second Gust Wind Speeds at 
10-Meters for MAT Investigation Sites (variations for terrain 
are provided) .....................................................................................................1-23 

Table 1-4. Notable Wind Speeds Recorded for Hurricane Ivan ......................................1-28 

Chapter 2 

Table 2-1. Baldwin County Stillwater Elevations and BFEs (2002) ...................................2-6 

Table 2-2. Santa Rosa County Stillwater Elevations ..........................................................2-11 

Table 2-3. Basic Design 3-Second Gust Wind Speeds (For Baldwin and 
Mobile Counties, Alabama) ..............................................................................2-23 

Table 2-4. Typical Single-Family Residence in Gulf Shores, Alabama .............................2-25 



Table 2-5. Basic Design 3-Second Gust Wind Speeds (Ranges for 
Each County) ....................................................................................................2-29 

Table 2-6. Wind Pressures on a Single-Family Residence in 
Pensacola, Florida .............................................................................................2-31 

Chapter 7 

Table 7-1. Design Wind Pressures Building Code ............................................................7-14 

Chapter 8 

Table 8-1. Recommended Foundations for Coastal Areas near Bay/ 
Sound Shorelines and Not Mapped as V Zone .................................................8-4 

Table 8-2. Design and Construction Recommendations .................................................8-10 

Table 8-3. Hazard Identification and Regulations Recommendations .............................8-11 

Table 8-4. Public Outreach Recommendations ................................................................8-12 

Table 8-5. Recommendations Specific to Critical and Essential 
Facilities .............................................................................................................8-14 

Table 8-6. Design and Construction Recommendations .................................................8-19 

Table 8-7. Building Code Recommendations ...................................................................8-22 

Table 8-8. Public Outreach Recommendations ................................................................8-25 

Table 8-9. Recommendations Specific to Critical and Essential 
Facilities .............................................................................................................8-27 

Appendix F 

Table F-1. Summary of Orange Beach, Alabama, High-Rise 
Buildings Inspected ............................................................................................F-2 

Table F-2. Description of Damage States Used in the Orange Beach 
High-Rise Study ...................................................................................................F-6 

Table F-3. Orange Beach High-Rise Buildings (n = 41) Classified by 
Lowest Floor Living Unit Damage States ...........................................................F-7 

Table F-4. Numbers of Lowest Floor Living Units Classified by 
Damage States (n = 233) for 41 Orange Beach High-Rise 
Buildings ..............................................................................................................F-8 



Table F-5. Damage States versus Top of Lowest Floor Elevation .....................................F-10 

Table F-6. Damage States versus Average Erosion Depth ................................................F-12 


FIGURES 

Chapter 1 

Figure 1-1. Path of Hurricane Ivan .......................................................................................1-4 

Figure 1-2. Surge elevation contours in Baldwin County, Alabama ..................................1-10 

Figure 1-3. Surge elevation contours in Escambia County, Florida ..................................1-10 

Figure 1-4. Surge elevation contours in Santa Rosa County, Florida ...............................1-11 

Figure 1-5. Surge elevation contours in Okaloosa County, Florida ..................................1-12 

Figure 1-6. The SLOSH model Envelope of High Water (EOHW) for 
Pensacola Bay, Florida ......................................................................................1-13 

Figure 1-7. CHWM surveyed elevations for Dauphin Island area .....................................1-14 

Figure 1-8. CHWM surveyed elevations for Upper Mobile Bay area ................................1-14 

Figure 1-9. CHWM surveyed elevations for West Beach/Fort Morgan 
area ....................................................................................................................1-15 

Figure 1-10. CHWM surveyed elevations for Orange Beach/Ono Island ...........................1-16 

Figure 1-11. CHWM surveyed elevations for Innerarity Point and 
Perdido Key areas ..............................................................................................1-17 

Figure 1-12. CHWM surveyed elevations for Pensacola/Gulf Breeze area ..........................1-18 

Figure 1-13. CHWM surveyed elevations for Upper Escambia Bay area ............................1-18 

Figure 1-14. CHWM surveyed elevations for Blackwater Bay area ......................................1-19 

Figure 1-15. CHWM surveyed elevations for Holley Navarre area .....................................1-19 

Figure 1-16. CHWM surveyed elevations for Fort Walton area ...........................................1-20 

Figure 1-17. CHWM surveyed elevations for Destin area ....................................................1-21 

Figure 1-18. Extent of hurricane and tropical storm force winds for 
Hurricane Ivan ..................................................................................................1-24 



Figure 1-19. Maximum recorded wind speeds from Hurricane Ivan 
normalized to 3-second peak gust at 10 meters, Exposure C ...........................1-25 

Figure 1-20. Wind swath contour plot (1-minute sustained winds at 
10 meter elevation) based on H*wind analysis ...............................................1-26 

Figure 1-21. Wind swath contour plot (3-second gust at 10-meter elevation) 
based on HAZUS-MH wind field methodology (ARA) ..................................1-27 

Figure 1-22. Historical hurricane and tropical storm paths ...............................................1-30 

Figure 1-23. Some of the locations visited by the MAT .......................................................1-32 

Chapter 2 

Figure 2-1. Floodplain Management Regulations and Building Design, 
Alabama ..............................................................................................................2-2 

Figure 2-2. Floodplain Management Regulations and Building Design, 
Florida ..................................................................................................................2-3 

Figure 2-3. Baldwin County location near the State Park/Orange 
Beach boundary where the historical FIRMs were reviewed. .............................2-7 

Figure 2-4. Comparison of FIRMs over time, at the State Park 
boundary, west end of Orange Beach (Orange Beach, 
Baldwin County, Alabama) .................................................................................2-8 

Figure 2-5. Ivan damage at the west boundary of Orange Beach. 
Houses are missing from piles and piles are broken near 
the ground level. (Orange Beach/State Park boundary) ................................2-9 

Figure 2-6. Ground photo of the same area as Figure 2-5. At this 
location, all houses seaward of the blue house (circled) 
were destroyed. ....................................................................................................2-9 

Figure 2-7. Building on the right side of Figure 2-5 survived, although 
it sustained destruction of the lower enclosed area and 
suffered extensive internal damage due to wind. ..........................................2-10 

Figure 2-8. Santa Rosa County locations where historical FIRMs were 
reviewed .............................................................................................................2-11 

Figure 2-9. Santa Rosa County: Comparison of FIRMs at the centerline 
of the intersection of Bay Street and Harrison Avenue ..................................2-12 

Figure 2-10. Typical houses at Birdseye Circle, which had 2 to 4 feet of 
flooding inside the houses. ..............................................................................2-13 



Figure 2-11. Typical damage to houses along Bay Street that were 
impacted by surge and wave effects from Santa Rosa 
Sound. (Santa Rosa County) ............................................................................2-13 

Figure 2-12. Aerial view of houses along Bay Street and Santa Rosa 
Sound that were heavily damaged by storm surge and 
wave impacts. .....................................................................................................2-14 

Figure 2-13. The house in the foreground was constructed on piles 
and had minimal flood damage during Ivan, although it 
lost a pile support for the deck. .......................................................................2-15 

Figure 2-14. The house on the right (circled), which is at the west end 
of Del Mar Drive, south of Bay Street, along the Santa 
Rosa Sound, was heavily damaged by storm surge and wave 
and debris impacts. ...........................................................................................2-15 

Figure 2-15. This house, located on Santa Rosa Sound and circled in 
Figure 2-14, was severely damaged by surge, wave, and 
debris impacts. ..................................................................................................2-16 

Figure 2-16. Design Wind Speeds from IBC 2003 and ASCE 7-98 and 02 .......................... 2-23 

Figure 2-17. Wind speed and windborne debris region map 
(Courtesy of the Florida Building Commission, 2001) ..................................2-29 

Chapter 3 

Figure 3-1. Buildings constructed on deep pile foundations 
performed well; however, significant damage occurred to 
lower-level enclosed areas and to stairways, utilities, and 
non-structural parking slabs below the elevated portion of 
the building. ........................................................................................................3-3 

Figure 3-2. Insufficient pile embedment caused displacement of 
houses (Gulf Shores, West Beach) .....................................................................3-3 

Figure 3-3. This building, which was less than 2 years old, was 
constructed on piers at the current BFE of 9 feet. It was 
severely damaged by high storm surge, and wave and 
debris impacts. (Big Lagoon) .............................................................................3-4 

Figure 3-4. Damage to NFIP-compliant elevated structure in a V Zone 
(north end of Escambia Bay-Floridatown) ........................................................3-5 

Figure 3-5. Buildings constructed on piles and elevated several feet 
above the BFE sustained less flood damage than adjacent 
buildings at lower elevations. (Big Lagoon) ......................................................3-5 



Figure 3-6. Surge, wave, and debris damage (Little Lagoon) .............................................3-6 

Figure 3-7. Older buildings below the current BFE sustained severe 
flood damage throughout the back bays. (Little Lagoon) ...............................3-6 

Figure 3-8. This new building was constructed to the BFE, but was 
wiped off its foundation (slab atop stem walls) by Ivan. 
(Big Lagoon) .......................................................................................................3-7 

Figure 3-9. Utilities, parking slabs, and enclosed areas under an 
elevated building were severely damaged by the high 
flood elevations and wave action. (Gulf Shores) ..............................................3-7 

Figure 3-10. Large timbers washed from developments on Santa Rosa 
Island, across Santa Rosa Sound, and into several homes 
(Santa Rosa Sound  Oriole Beach) ..................................................................3-8 

Figure 3-11. Significant floodborne debris contributed to the severe 
damage of at-grade enclosed area beneath an elevated 
building. (Big Lagoon) .......................................................................................3-8 

Figure 3-12. Significant floodborne debris contributed to the severe 
damage of buildings throughout the back bays and 
sounds in areas mapped as Zone AE. (Oriole Beach  
Santa Rosa Sound) ..............................................................................................3-9 

Figure 3-13. Collapse of 5-story, multi-family buildings on shallow 
foundations (Orange Beach) ...........................................................................3-10 

Figure 3-14. Pile foundations performed well, but non-structural floor 
slabs collapsed and low-elevation living units were 
destroyed.(Orange Beach) ...............................................................................3-10 

Figure 3-15. Building supported on pile foundation (foreground) 
survived while building on shallow foundation 
(background) collapsed. (Orange Beach) ......................................................3-11 

Figure 3-16. Foundation and structural floor slab survived but lowest 
floor non-structural exterior walls were destroyed by 
surge and waves (Orange Beach) ....................................................................3-12 

Figure 3-17. Destruction of low-elevation living units by surge and 
waves, while second floor units survived intact (Orange 
Beach) ................................................................................................................3-12 

Figure 3-18. Typical wind damage showing loss of roof sheathing and 
damage to structural roof framing (Ono Island) ...........................................3-16 



Figure 3-19. Typical roof sheathing and covering loss (Pensacola Beach) ...........................3-16 

Figure 3-20. Typical gable end wall failure and loss of roof sheathing 
and wall (Perdido Key) .....................................................................................3-17 

Figure 3-21. Typical high rise cladding failure (Perdido Key) ............................................3-17 

Figure 3-22. Commercial building roof covering failure (Pensacola Beach) .......................3-18 

Figure 3-23. Commercial building wall cladding and secondary 
structure failure (Gulf Shores) .........................................................................3-18 

Figure 3-24. Pre-engineered metal building damage (Orange Beach) ..............................3-19 

Figure 3-25. Metal wall panel damage to middle school (Gulf Breeze) .............................3-19 

Figure 3-26. Roof covering and roof deck damage to middle school 
(Pensacola) ........................................................................................................3-20 

Figure 3-27. After this building was destroyed by Hurricane Frederic 
in 1979 (upper photo), it was re-constructed on concrete 
columns, pile caps, and deep piles. (Gulf Shores) .........................................3-21 

Figure 3-28. Severe corrosion of reinforcing steel and spalling of the 
concrete columns supporting the post-Frederic building 
shown in Figure 3-27. .......................................................................................3-22 

Figure 3-29. Hurricane Opal (1995) flood damage to one of the four 
original buildings ..............................................................................................3-23 

Figure 3-30. 1998 photograph showing the post-Opal replacement 
(pile supported) building (background) and one of the 
three remaining older buildings (foreground) ..............................................3-23 

Figure 3-31. Post-Ivan aerial photograph showing severe flood damage 
to two of the three older buildings, with newer, pilesupported 
building intact (left side) ...............................................................3-24 

Figure 3-32. Ivan flood and wind damage to older building (post-Opal 
building visible at far left) ................................................................................3-24 

Figure 3-33. Hurricane Ivan, non-structural enclosure and deck damage 
below newer building .......................................................................................3-25 

Figure 3-34. Four Orange Beach condominiums before Hurricane Ivan. 
The lower pair of buildings was newer, having been 
constructed after the predecessors were destroyed by 
Hurricane Georges (1998). (USGS) ................................................................3-26 



Figure 3-35. The four condominiums in Figure 3-34 after Hurricane 
Ivan (USGS) .......................................................................................................3-27 

Figure 3-36. Deep foundation exposed by erosion, and collapse of 
undermined parking slab, as shown in the photo on the right. .......................3-28 

Figure 3-37. Elevated building constructed to newer code that survived 
Hurricane Ivan (Big Lagoon) ..........................................................................3-29 

Figure 3-38. Older, non-elevated building (near building in Figure 3-37) 
severely damaged in Hurricane Ivan (Big Lagoon) ........................................3-29 

Figure 3-39. House on La Paz Street that was not elevated to the 
current BFEs, and, therefore, was severely damaged by the 
high coastal flooding and wave impacts. .........................................................3-30 

Figure 3-40. House on La Paz Street that was elevated on piles, which 
prevented severe damage from coastal flooding. ...........................................3-30 

Figure 3-41. House on La Paz that was elevated on piles, which 
prevented major flood damage ........................................................................3-31 

Figure 3-42. The surviving house was built to incorporate the 
provisions of the new building code (IRC, IBC) even 
before it was adopted. (Orange Beach) ..........................................................3-31 

Chapter 4 

Figure 4-1. House on a pile foundation that performed well. It 
experienced 5 feet of erosion that resulted in failure of a 
non-structural slab.(Gulf Shores) ......................................................................4-3 

Figure 4-2. House on pile foundation, adjacent to breach in the 
barrier island, that experienced erosion and significant 
non-structural damage below the lowest floor (Gulf Shores). ...........................4-3 

Figure 4-3. These pile-elevated houses in an area mapped as Zone VE 
at Pensacola Beach successfully resisted flood forces. 
Loss of breakaway enclosures and garage doors below the 
lowest floors occurred. (FL DEP Photo). ..........................................................4-4 

Figure 4-4. Row of newer houses on pile foundations that experienced 
significant damages below the lowest floor, but overall the 
pile foundation systems performed well. (Gulf Shores) ..................................4-4 

Figure 4-5. Floor joists were pushed landward when the wave crest 
elevation was above the floor beam. (Gulf Shores). .........................................4-5 



Figure 4-6. Significant erosion caused the non-structural parking slab 
to fail, and insufficient pile embedment caused the 
structure to lean. (Orange Beach) .....................................................................4-5 

Figure 4-7. Erosion contributed to loss of the porch, failure of the 
retaining wall and non-structural parking slab, and 
destruction of the enclosure below the first floor. 
(Orange Beach) ..................................................................................................4-6 

Figure 4-8. The pile foundations in the foreground failed. These 
houses were washed away (see Figures 3-2 and 4-9). ........................................4-6 

Figure 4-9. These houses floated off their pile foundations (shown in 
Figures 4-8 and 3-2). ...........................................................................................4-7 

Figure 4-10. House constructed on a pile foundation in a V Zone 
along Escambia Bay (Floridatown) ....................................................................4-8 

Figure 4-11. Damage to pile-supported house on a bay shoreline, when 
flooding and waves exceeded the lowest floor elevation 
(Gulf Breeze, Pensacola Bay) .............................................................................4-8 

Figure 4-12. House at left (circle) was torn from its pile foundation. 
New houses under construction survived Ivan (Big Lagoon). .........................4-9 

Figure 4-13. Same destroyed house as in Figure 4-12 (circled). Note 
adjacent pile-elevated houses near shoreline, also 
destroyed (Big Lagoon). .....................................................................................4-9 

Figure 4-14. House constructed on piles several feet higher than the 
BFE. Floodwater, waves, and debris caused damages to the 
ground level enclosed area of the house, but not to the 
elevated portion. (Big Lagoon) .......................................................................4-10 

Figure 4-15. Area just to the west of the house shown in Figure 4-14. 
Pile-elevated houses above the BFE (circled) survived, 
while older houses on slab foundations were destroyed. ...............................4-11 

Figure 4-16. Ground view of some of the debris shown in Figure 4-15. .............................4-11 

Figure 4-17. This house located near Sinton Drive successfully resisted 
flood forces since it was elevated higher than the BFE on 
piles. (Big Lagoon) ...........................................................................................4-12 

Figure 4-18. This photo shows the destroyed building adjacent to the 
house in Figure 4-17. (Big Lagoon) .................................................................4-12 



Figure 4-19. The pre-FIRM building constructed on a slab foundation 
(foreground) was completely destroyed. (Big Lagoon) .................................4-13 

Figure 4-20. Destruction of slab-on-grade house (circled) in the Grande 
Lagoon neighborhood (Big Lagoon) ..............................................................4-13 

Figure 4-21. The unreinforced masonry pre-FIRM building in the 
foreground was swept off its slab foundation during Ivan. 
(Oriole Beach) ..................................................................................................4-14 

Figure 4-22. This slab-on-grade building located on the back side of 
the barrier island but directly on the sound was heavily 
damaged by wave action. (Pensacola Beach) ..................................................4-14 

Figure 4-23. The slab-on-grade building located near the back side of 
the barrier island was protected from wave action by other 
houses, but had 4 to 5 feet of water inside. (Pensacola 
Beach) ................................................................................................................4-15 

Figure 4-24. House constructed in a Zone AE on a stem wall foundation, 
which survived, although high floodwaters with debris and 
wave action caused major damage (Big Lagoon) ...........................................4-16 

Figure 4-25. Stem wall foundation where floodwater exceeded required 
flood elevation by approximately 4 feet (Garcon Point, 
Escambia Bay) ...................................................................................................4-16 

Figure 4-26. This stem foundation elevated the house above the BFE 
and performed well. (Tiger Point, Santa Rosa Sound) ..................................4-17 

Figure 4-27. Unreinforced pier foundations failed due to scour at the 
footing and flood levels exceeding the floor elevation 
(Oriole Beach). . ...............................................................................................4-18 

Figure 4-28. Center pier failed causing the elevated floor to collapse. 
(Santa Rosa Sound) ..........................................................................................4-18 

Figure 4-29. Tall, lightly reinforced masonry piers failed due to lateral 
loads from surge and wave action. (Big Lagoon). ..........................................4-19 

Figure 4-30. Manufactured home park where houses experienced storm 
surge, scour, and foundation collapse (Orange Beach) .................................4-19 

Figure 4-31. Unreinforced, dry-stacked block piers slid off of footings. 
(Orange Beach) ................................................................................................4-20 

Figure 4-32. Dry-stacked pier failure (Orange Beach) ........................................................4-20 



Figure 4-33. Total collapse of 5-story building on a shallow foundation 
(Orange Beach) ................................................................................................4-22 

Figure 4-34. Close-up of building shown in Figure 4-33 (Orange Beach) .........................4-22 

Figure 4-35. Shallow foundation failure (Orange Beach - Perdido Key) ...........................4-23 

Figure 4-36. Collapse of a 5-story building constructed on a shallow 
foundation (Orange Beach) Photo courtesy of USGS ...................................4-24 

Figure 4-37. Collapse of the seaward portion of a high-rise building 
supported by a shallow foundation (Perdido Key) ........................................4-25 

Figure 4-38. Older buildings constructed on masonry columns and 
walls atop shallow footings (Pensacola Beach). ..............................................4-25 

Figure 4-39. This building has been flooded by Hurricane Ivan and 
four prior storms. (Pensacola Beach) ..............................................................4-26 

Figure 4-40. Multi-family building on a bay shoreline, heavily damaged 
by surge, waves and floating debris (Oriole Beach, Santa 
Rosa Sound) ......................................................................................................4-27 

Figure 4-41. Aerial view of building in Figure 4-40 .............................................................4-27 

Figure 4-42. Multi-story buildings on piles, impacted by storm surge, 
waves, and erosion, which damaged many lower area walls 
and floors (Orange Beach) ..............................................................................4-28 

Figure 4-43. Although the pile foundation and structural elements 
survived, damage to lowest floor exterior walls, interior 
partitions, and floor slabs occurred during Ivan. (Orange 
Beach) ................................................................................................................4-28 

Figure 4-44. The building on the left shows minimal damage, while the 
building on the right with the lower-level living units 
experienced significant non-structural damage. (Orange 
Beach) ................................................................................................................4-29 

Figure 4-45. This condominium on a deep foundation is located on 
the back side of the barrier island, north of Ft. Pickens 
Road. (Pensacola Beach) ..................................................................................4-30 

Figure 4-46. Aerial view of the building shown in Figure 4-45 (FL DEP 
photo) (Pensacola Beach) ................................................................................4-30 

Figure 4-47. Building with flood and wave damage to the lowest floor 
living units (Perdido Key) ................................................................................4-31 



Figure 4-48. Most of the first floor units in these buildings were severely 
damaged (see Figures 4-53 and 4-54). (Orange Beach) .................................4-31 

Figure 4-49. Pile support buildings performed much better than 
buildings constructed on shallow foundations. (Orange 
Beach) ................................................................................................................4-32 

Figure 4-50. Typical pool failure (Pensacola Beach) ...........................................................4-33 

Figure 4-51. Retaining wall failure (Gulf Shores) ................................................................4-33 

Figure 4-52. Failure of vinyl bulkhead with concrete cap (Orange Beach) .........................4-34 

Figure 4-53. Bulkhead remained intact, but short return wall allowed 
erosion behind the wall (Orange Beach). .......................................................4-34 

Figure 4-54. Bulkhead shown in Figure 4-53 remained in-place, but 
surge and wave overtopping, coupled with erosion at the 
short return wall, led to deck and retaining wall failure. 
(Orange Beach) ................................................................................................4-35 

Figure 4-55. Sand below slab completely eroded away, causing the total 
failure of slab, but grade beams remained intact. 
(Gulf Shores) .....................................................................................................4-35 

Figure 4-56. Concrete slab partially separated from the pile even 
though it had been connected with a nail. (Gulf Shores) .............................4-36 

Figure 4-57. Typical non-structural concrete slab failure. Horizontal 
line indicates previous location of soil level and slab. ( 
Orange Beach) ..................................................................................................4-36 

Figure 4-58. This slab failed but did not break into small pieces due to 
the reinforcing steel. (Orange Beach) ............................................................4-37 

Figure 4-59. Failure of breakaway walls as designed (Gulf Shores) ....................................4-38 

Figure 4-60. Poor detailing of the joint between the breakaway wall 
and the wall above contributed to loss of wall covering 
above the floor beam. (Pensacola Beach). ......................................................4-38 

Figure 4-61. Failure of interior partition to break away cleanly due to 
the attachment of utilities (Gulf Shores) ........................................................4-39 

Figure 4-62. Breakaway walls were nailed over the piles and floor beam, 
preventing a clean break. (Gulf Shores) .........................................................4-39 

Figure 4-63. Loss of condenser platform support. A cantilevered 
condenser support is recommended. (Pensacola Beach) ..............................4-40 



Figure 4-64. Diagonal condenser platform members are susceptible to 
wave and waterborne debris damage. (Gulf Shores) ......................................4-40 

Figure 4-65. Elevator system severely damaged by surge, waves, and 
debris (Gulf Shores) .........................................................................................4-41 

Figure 4-66. Loss of platform supports and air conditioning unit due to 
erosion and flood forces (Gulf Shores) ...........................................................4-41 

Figure 4-67. House under construction at the time of Ivan (Big Lagoon) ..........................4-42 

Figure 4-68. Erosion and flood damage to multi-family electrical 
transformer and interior mechanical room (Perdido Key) ...........................4-42 

Figure 4-69. Debris and sand in low-elevation mechanical room 
(Perdido Key) ....................................................................................................4-43 

Figure 4-70. Damage to the electrical panel, but utility lines were located 
appropriately (beside an interior pile) (Pensacola Beach) ...........................4-43 

Figure 4-71. Drain lines constructed between interior piles (which 
helped to protect them from flood forces), although 
electrical box was connected to plywood panel and was 
destroyed (Pensacola Beach) ...........................................................................4-44 

Figure 4-72. Massive stairs that will obstruct flows could deflect waves 
and debris into the elevated building. (Gulf Shores) .....................................4-45 

Figure 4-73. Stairway structures (circled) that will minimize obstructions 
to flow and potential adverse effects on the elevated 
building (Gulf Shores) .....................................................................................4-45 

Figure 4-74. Large accumulation of debris trapped between house and 
dune walkover (Gulf Shores) ...........................................................................4-46 

Figure 4-75. Ground level photograph of debris shown in Figure 4-74 
(Gulf Shores) .....................................................................................................4-46 

Figure 4-76. Marine pile debris washed into this house in the back bay. 
(Oriole Beach) ..................................................................................................4-47 

Figure 4-77. Same marine pile as shown in Figure 4-76. (Oriole Beach) ...........................4-47 

Figure 4-78. Boats and dock debris from a marina struck this pileelevated 
building, deforming floor beams, breaking joist 
connections, and scarring pilings. (Big Lagoon) ...........................................4-48 

Figure 4-79. Typical view of destroyed docks contributing to floodborne 
debris (Big Lagoon) ..........................................................................................4-48 



Figure 4-80. Small stones from a nearby revetment were likely propelled 
by waves into this north-facing sound side house, breaking 
windows and sliding glass doors. (Gulf Breeze) ..............................................4-49 

Figure 4-81. The small stone revetment contributed stones which were 
propelled by waves and struck the house shown in 
Figure 4-80 (Gulf Breeze) .................................................................................4-49 

Figure 4-82. Load path of a two-story building with a primary woodframing 
system: walls, roof diaphragm, and a floor 
diaphragm ........................................................................................................4-51 

Figure 4-83. Storm surge damaged the lower portion of this house, 
but no wind damage was observed. (Gulf Shores) ..........................................4-52 

Figure 4-84. Progressive failure of wood roof framing (Perdido Key) ...............................4-53 

Figure 4-85. Gable end wall framing diagram .....................................................................4-54 

Figure 4-86. Roof truss with 2x4s oriented in the weak direction 
resisting the wind loads on a gable end wall (Ono Island) ............................4-54 

Figure 4-87. Gable end wall failure due to lack of bracing at hinge 
point in wall (see arrow) (Perdido Key) ..........................................................4-55 

Figure 4-88. Roof framing damage due to lack of connections from 
roof to wall (Orange Beach) ............................................................................4-56 

Figure 4-89. Roof framing damage due to lack of connections from 
roof to wall (Pensacola Beach) ........................................................................4-56 

Figure 4-90. Roof framing damage due to lack of connections from 
roof to wall (Ono Island) .................................................................................4-57 

Figure 4-91. Improper use of a wood truss press plate connector to 
substitute for stud hold-downs (Oriole Beach) ...............................................4-57 

Figure 4-92. Already corroded anchor bolt in new construction 
(Oriole Beach) ..................................................................................................4-58 

Figure 4-93. Improper strapping (Ono Island) ...................................................................4-58 

Figure 4-94. Wall studs between garage doors with inadequate holddowns 
(Ono Island) ..........................................................................................4-59 

Figure 4-95. Metal roofing failure (Foley) ...........................................................................4-60 

Figure 4-96. Heavily damaged pre-engineered boat storage building 
(Orange Beach) ................................................................................................4-61 



Figure 4-97. Heavily damaged pre-engineered boat storage building 
(Orange Beach) ................................................................................................4-61 

Figure 4-98. Collapsed metal canopy at a middle school (Pensacola) ...............................4-62 

Chapter 5 

Figure 5-1. Loss of vinyl siding panels from the underside of an 
elevated residence in Gulf Shores (Laguna Key) ..............................................5-2 

Figure 5-2. Loss of gypsum board from the underside of an elevated 
residence in Gulf Shores (Laguna Key) ............................................................5-3 

Figure 5-3. Loss of plywood from the underside of an elevated 
residence in Gulf Shores (West Beach) .............................................................5-3 

Figure 5-4. Tempered glass door broken by debris from a mortar-set 
tile roof (Pensacola) ...........................................................................................5-5 

Figure 5-5. Sliding glass door frame blown from the wall ..................................................5-5 

Figure 5-6. Floodwater collapsed the garage door at the left end of 
this residence. (Laguna Key) .............................................................................5-6 

Figure 5-7. Typical EIFS assembly .........................................................................................5-8 

Figure 5-8. Typical stucco assembly ......................................................................................5-9 

Figure 5-9. Vertical peeling on a home in Gulf Shores due to lack of 
a projecting band or reveal after the breakaway wall failed 
(Laguna Key) .....................................................................................................5-10 

Figure 5-10. All gypsum board blown off and two windows broken by 
debris. Note the missing studs. (Pensacola Beach) ........................................5-11 

Figure 5-11. Severely deteriorated studs and corroded metal connectors ..........................5-11 

Figure 5-12. Blown off EIFS revealed severely rotted oriented strand 
board (OSB) due to water infiltration at windows and wall 
penetration. .......................................................................................................5-12 

Figure 5-13. Loss of EIFS on a commercial building .........................................................5-13 

Figure 5-14. Multi-story building showing severe EIFS damage. The 
gypsum board typically detached from the studs. ..........................................5-13 

Figure 5-15. The gypsum board detached from the studs at the 
penthouse. Rainwater infiltration damaged the elevator 
controls. (Pensacola) ........................................................................................5-14 



Figure 5-16. EIFS blew off the hospital building in the background 
(see red circle and Figures 5-18 and 6-2). (Pensacola) ..................................5-15 

Figure 5-17. Looking down at the one-story roof to the right of the MOB 
in Figure 5-16 ....................................................................................................5-15 

Figure 5-18. Close up of the damaged EIFS at the hospital ................................................5-16 

Figure 5-19. Wood studs and gypsum board had been temporarily 
installed after the hurricane. ............................................................................5-17 

Figure 5-20. Hospital with EIFS blown off a cast-in-place wall. Note the 
damaged rooftop ductwork. (Pensacola) ........................................................5-17 

Figure 5-21. Close-up of Figure 5-20. The light colored round marks 
indicate where adhesive had been applied. (Perdido Key) ............................5-18 

Figure 5-22. Failure of non-load-bearing stucco wall (see close-up of 
Figure 3-21) .......................................................................................................5-20 

Figure 5-23. Close-up of Figure 3-21. With complete loss of the walls, 
the residents could have inadvertently fallen from the 
building. ............................................................................................................5-21 

Figure 5-24. Six-year old, stucco-sheathed residence with severely 
rotted plywood (Pensacola Beach) ..................................................................5-22 

Figure 5-25. At the end wall of the center building, stucco blew off the 
concrete substrate. ............................................................................................5-22 

Figure 5-26. Brick veneer failure on an office building (Pensacola). ................................5-24 

Figure 5-27. Wood-frame residence has several corrugated ties that 
were never embedded into the mortar joints (see inset) ...............................5-25 

Figure 5-28. These panels were attached with concealed fasteners. 
They unlatched at the standing seams. ............................................................5-26 

Figure 5-29. The green fascia panels had been installed over a 
previous metal panel system. ............................................................................5-27 

Figure 5-30. Loss of vinyl soffits was common. .....................................................................5-28 

Figure 5-31. Although a high-wind panel was used, extensive loss of 
siding and housewrap underlayment occurred. 
See Figure 5-32. .................................................................................................5-29 

Figure 5-32. A double thickness of vinyl occurred at the nailing flange. 
However, many of the panels pulled over the nail heads. ..............................5-29 



Figure 5-33. When a panel becomes unlatched, it becomes very 
susceptible to blow-off. .....................................................................................5-30 

Figure 5-34. Failure of wood framed exterior walls covered with the 
wood siding ........................................................................................................5-32 

Figure 5-35. Vinyl siding had been installed over textured plywood 
siding. ................................................................................................................5-32 

Figure 5-36. The vertical lines of missing shingle tabs are indicative of 
installation via the raking method. ..................................................................5-34 

Figure 5-37. Partial blow-off of ridge vent. When the plywood was 
slotted, the trusses and truss plates were cut. ..................................................5-35 

Figure 5-38. Missing tabs .......................................................................................................5-35 

Figure 5-39. This roof is indicative of tile failure at modest wind speeds, 
wherein failure of eave, hip, and rake tiles were most 
common. . ..........................................................................................................5-36 

Figure 5-40. Direct-to-deck mechanically attached clay tile ................................................5-37 

Figure 5-41. Both nails were located in the right corner. ....................................................5-38 

Figure 5-42. The fastener heads on this direct-to-deck mechanically 
attached tile roof had corroded. ......................................................................5-38 

Figure 5-43. Loss of several batten-attached tiles from a mid-rise 
building .............................................................................................................5-39 

Figure 5-44. Although some of these batten-attached tiles were 
damaged by wind pressure, the majority were damaged by 
windborne debris. .............................................................................................5-40 

Figure 5-45. The majority of these batten-attached tiles were displaced 
by wind pressure. ...............................................................................................5-40 

Figure 5-46. The majority of these batten-attached tiles were displaced 
by wind pressure. ...............................................................................................5-41 

Figure 5-47. The tiles on the lower sloped roof were foam-set. The 
damage on this roof was due to a combination of wind 
pressure and windborne debris. .......................................................................5-41 

Figure 5-48. These tiles were foam-set. See Figures 5-49 and 5-50. .....................................5-42 

Figure 5-49. A minuscule amount of foam was installed. Note that one 
tile slid down-slope about 2" (red arrow). See Figure 5-50. ...........................5-42 



Figure 5-50. View of the underside of the tile that slid in Figure 5-49. ..............................5-43 

Figure 5-51. Significant loss of hip and ridge tiles ...............................................................5-43 

Figure 5-52. These hip and ridge tiles were foam-set. .........................................................5-44 

Figure 5-53. Loss of standing seam metal panels. See Figure 5-54. 
(Pensacola) ........................................................................................................5-44 

Figure 5-54. These panels nearly blew away. The seams on three of the 
panels opened up. (Pensacola) ........................................................................5-45 

Figure 5-55. This 5-V crimp metal panel roof performed very well. ..................................5-45 

Figure 5-56. This residence had metal shingles that simulated the 
appearance of tile. ...........................................................................................5-46 

Figure 5-57. Although the metal edge flashing lifted, a progressive 
membrane lifting and peeling did not occur. (Pensacola) ............................5-47 

Figure 5-58. The edge nailer on top of an old brick wall was 
inadequately attached to the wall. (Pensacola) ...............................................5-48 

Figure 5-59. Loss of a mineral-surfaced BUR installed over LWIC. 
(Pensacola) ........................................................................................................5-49 

Figure 5-60. Minor base flashing displacement on a new hospital roof 
(Gulf Breeze) ....................................................................................................5-49 

Figure 5-61. Single-ply membrane torn by windborne debris (Pensacola) ........................5-50 

Figure 5-62. This hospital roof had been punctured in several locations 
by windborne debris. (Pensacola) ...................................................................5-50 

Figure 5-63. Several windows on this ocean-front home were broken 
by windborne debris. ........................................................................................5-53 

Figure 5-64. The outer pane of this tempered glass window was broken 
by windborne debris. (Pensacola) ...................................................................5-53 

Figure 5-65. This shutter was impacted by high-energy debris. ..........................................5-54 

Figure 5-66. Shutters had been retrofitted on this school, but the 
glazing above and below the window air conditioners and 
the glass entry doors were not protected. (Pensacola) ...................................5-55 

Figure 5-67. These panels did not completely cover the glazing. .......................................5-55 



O 


C H A P T E R 1 

1-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

1 

Introduction 

On September 18, 2004, the Mitigation Division of the Department of Homeland Securitys 
Federal Emergency Management Agency (FEMA) deployed a Mitigation Assessment Team 
(MAT) to the States of Alabama and Florida to assess damages caused by Hurricane Ivan. This 
report presents the MATs observations, conclusions, and recommendations as a result of 
those field investigations. 

Chapter 1 provides an introduction, a discussion of the event, historical information, and 
background on the MAT process. Chapter 2 discusses the floodplain management regula
tions 
and the codes and standards that affect construction in Alabama and Florida. Chapter 3 
provides a general characterization of the observed flood and wind effects, and it documents 
observed hazard mitigation lessons learned and best practices. Chapter 4 details structural 
systems performance in residential and commercial buildings as well as in critical and essen
tial 
facilities. Chapter 5 presents an assessment of building envelope performance. Chapter 
6 discusses damages and functional loss to critical and essential facilities. Finally, Chapters 7 
and 8 present the conclusions and recommendations that are intended to help guide the re
construction 
of hurricane-resistant communities in Alabama and Florida and construction in 
all hurricane-prone regions. Additional information related to the specific technical issues is 
provided in the appendices. 

1.1 Hurricane Ivan  the Event 

The National Hurricane Center (NHC) has issued its report on Hurricane Ivan.1 The re
port 
traces the history of the hurricane and presents meteorological statistics, casualty 
and damage statistics, and a forecast and warning critique. In addition, the National 
Weather Service (NWS) office in Mobile, Alabama, has prepared its own report on the storm.2 
The NWS report includes hourly 0.5-degree radar reflectivity images taken from the NWS 
WSR-88D Doppler Weather Radar in Mobile, Alabama, prior to, during, and after landfall; 
observed peak wind gusts and times; observed storm surge data; and 48-hour rainfall totals. 

1 Stewart, Stacy R., Tropical Cyclone Report Hurricane Ivan 2-26 September 2004, National Hurricane Center Report, 
16 December 2004, Revised 6 January 2005. 

2 National Weather Service Mobile  Pensacola, Powerful Hurricane Ivan Slams the US Central Gulf Coast as Upper 
Category-3 Storm, www.srh.noaa.gov/mob/ivan_page/Ivan-main.htm. 



C H A P T E R 1 

INTRODUCTION 

1-2 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

THE SIGNIFICANCE OF HURRICANE IVAN 

Hurricane Ivan was the most severe hurricane to strike the eastern Alabama, western Florida coastline 
in many decades. The significance of Ivan and its effects are summarized below: 

 Ivan approximated or slightly exceeded design flood conditions on many of the affected barrier islands, 
with the highest open coast flood levels near the area of landfall. 

 On the bay and sound shorelines between Gulf Shores, Alabama, and Santa Rosa County, Florida, Ivan 
greatly exceeded a design flood event. Flood levels during the storm generally exceeded the Base (1- 
percent annual exceedance probability) Flood Elevations (BFEs) on many Flood Insurance Rate Maps 
(FIRMs) by several feet, calling into question the adequacy of the storm surge modeling used as the 
basis for the FIRMs and highlighting the importance of adding freeboard when constructing in coastal 
floodplains. 

 Flood and erosion damages on barrier islands were generally consistent with expectations. Buildings 
closest to the shoreline sustained the most severe damage, and buildings in areas with the narrowest 
beaches and dunes before Ivan struck sustained more damage than buildings in areas with wide 
beaches and healthy dunes before the storm. 

 On barrier islands, newer pile- and/or column-supported buildings elevated above the BFE generally 
performed well; however, they sustained non-structural damage to areas below the elevated floor. 
Some newer buildings elevated to the BFE sustained flood damage (structural and non-structural) 
above and below the BFE. Many older, post-FIRM buildings sustained significant structural damage due 
to piling failures (e.g., inadequate pile embedment, pile breakage, poor connections between the piles 
and the elevated building, etc.) or inadequate foundations, or because of insufficient elevation. 

 On the barrier islands, several relatively new (less than 10-12 years old), three- to five-story multi-family 
buildings, constructed on shallow foundations in flood Zones B, C, or X, collapsed due to erosion and 
undermining. This is the first time that recent post-storm investigations have observed total failures of 
multi-family buildings due to flood effects. 

 Flood damage along bay and sound shorelines was far beyond expectations. Even newer buildings 
constructed in compliance with minimum community foundation and elevation standards sustained 
severe damage due to waves, floodborne debris, and velocity flow. Flood (inundation) damage occurred 
in many areas outside the Special Flood Hazard Area (SFHA) shown on FIRMs. The only types of 
buildings that generally performed well in these areas were those built on piles or stemwall foundations 
with their lowest floor above Ivans wave crest elevation. 

 Ivan was less than a design wind event when expected loads are compared to the 2001 Florida Building 
Code (FBC) and the 2000/2003 International Building Code (IBC) and International Residential Code 
(IRC) load provisions. These codes use a design wind speed map developed for the 1998 edition of 
ASCE 7 where substantial increases in design wind speeds were introduced in this region. 

 Ivan was a design wind event from the Gulf Shores area east through Orange Beach and Pensacola 
Beach and inland in some areas as far north as I-10 for structural frames of buildings built under 
Standard Building Code (SBC) 1979 through 1997 wind load provisions for structural systems. In 
addition, Ivan was a greater than design wind event for this same geographic area when estimated 
actual loads on roof corners and edges are compared to the SBC 1979 through 1997 wind load 
provisions for cladding elements. 

 Wind damage to both commercial and residential buildings was widespread in the southern portions 
of Baldwin County, Alabama, and in the southern portions of Escambia and Santa Rosa Counties, 
Florida. 

 In general, buildings functioning as critical and essential facilities did not perform significantly better than 
their commercial-use counterparts. As a result of poor building envelope performance, the operations and 
response at many critical and essential facilities were hampered or shut down and taken off-line after the 
hurricane. Most critical and essential facilities in the impacted area were housed in older buildings and 
most, if not all, apparently were not mitigated to resist known hurricane risks. 

 Hurricane Ivan generated a greater number and value of flood claims than any other coastal flood event 
in the history of the National Flood Insurance Program (NFIP)  over 18,000 claims valued at over 1 
billion dollars. 

 Due to the severe destruction, the MAT was tasked to assess performance of buildings (residential, 
commercial, critical and essential facilities), floodplain management regulations and FIRMs, building 
codes, and construction practices. 



INTRODUCTION 

When Hurricane Ivan made landfall on September 16, 2004, the NHC 
reported it as a major hurricane that produced sustained winds of 121 
miles per hour (mph), torrential rains, coastal storm surge flooding 
of 10 to 16 feet above normal high tide, and large and battering waves 
along the Alabama and western Florida Panhandle coastline. The NWS 
reports that on September 15 through 16, Ivan spawned 23 tornadoes3 
in Florida and produced as much as 10 to 15 inches of rainfall in some 
areas. Widespread damage occurred, including the damage and/or 
destruction of buildings, infrastructure, and beach erosion. 

After landfall, Hurricane Ivan gradually weakened over the next week, 
moving northeastward over the southeastern United States and even
tually 
emerging off the Delmarva Peninsula as an extratropical low 
on September 19, 2004. The remnant circulation of Ivan then moved 
southwestward, passed over South Florida into the Gulf of Mexico, 
and became a tropical storm again on September 23. As a tropical 
storm, Ivan made its second landfall over southwestern Louisiana on 
September 24, and finally dissipated inland over East Texas later that 
day. Figure 1-1 shows Ivans path associated with its initial landfall on 
September 16, 2004. 

3 The MAT did not investigate any sites impacted by tornadoes spawned by Hurricane Ivan. 



Beyond the normal NWS Automated Surface Observing System (ASOS) 
(the nations primary surface weather observing network stations in 
the area), data were collected at a number of military airports and at a 
number of sites where universities deployed portable meteorological 
instruments and towers in front of the advancing storm. The result is 
that there are a number of surface data observations available for Hur
ricane 
Ivan, particularly near the coast. These observations provide a 
good basis for assessing the performance of various wind field models 
in describing the geographical distribution of winds throughout the 
region impacted by Hurricane Ivan. 

The flood and wind data and maps of probable maximum wind speeds 
included in this report reflect the best available estimates at the time 
of publication. With all hurricanes, there can be localized areas im
 


Figure 1-1. 
Path of Hurricane Ivan 



pacted by special features of the storm including convective cells that 
bring high winds down to the surface. Nevertheless, with the exception 
of one unofficial observation from a sailboat in Wolf Bay, the surface 
observations provide a portrait of a wind field that does not contain 
significant local variations and is generally consistent with the geo
graphical 
distributions and magnitudes suggested by the leading wind 
field models. Furthermore, the leading models provide estimates of 
maximum peak overland surface wind speeds that are within a couple 
of mph of each other. 

Hurricane Categories 

Hurricanes are classified in different categories according to the Saf
fir-
Simpson Hurricane Scale. Table 1-1 presents the categories of 
the Saffir-Simpson Hurricane Scale along with their respective wind 
speeds, presented as both 1-minute sustained wind speeds and as 3-sec
ond 
peak gust wind speeds. Hurricane Ivan is categorized as a Category 
3 major hurricane by the NHC in its Tropical Cyclone Report. A ma
jor 
hurricane is defined as one that has estimated 1-minute sustained 
wind speeds (over open water) that exceed 111 mph. For Ivan, the 
NHC estimated sustained wind speeds at landfall of 121 mph. This is 
equivalent to the threshold velocity for a Category 3 storm on the Saf
fir-
Simpson Hurricane Scale. 

As the storm made landfall just west of Gulf Shores, Alabama, the 
eye diameter is estimated to have increased to between 46 and 58 
miles with the strongest winds occurring in a narrow region near the 
southern Alabama-western Florida Panhandle border (NHC Tropical 
Cyclone Report). A number of surface observation sites provided data 
throughout the coastal region. The data indicate that most of the re
gion 
impacted by the storm likely experienced Category 1 intensity 
winds with some areas near the Alabama-Florida border experiencing 
Category 2 intensity winds. None of the surface wind measurements 
for overland conditions correspond to Category 3 intensity winds. 
Category 3 intensity winds may have occurred in relatively small areas 
along the gulf/land and bay/land interfaces near the Alabama-Florida 
border. A more complete discussion of wind speed estimates based on 
surface wind measurements and computer modeling is provided in 
Section 1.1.2. 



1.1.1 Storm Surge Analysis and Discussion 

Many of the barrier islands exposed to Hurricane Ivan are low lying 
and could not contain the storm surge associated with the storm. 
Coastal storm surge flooding crossed the barrier islands, under
mining 
buildings and roads, and opening new island breaches. In 
addition to the storm surge, breaking waves eroded dunes and bat
tered 
structures. The storms arrival was concurrent with high tide, 
which increased storm surge flooding that was estimated at 10 to 16 
feet above normal tide levels. Large and dangerous battering waves 
occurred near and to the east of where the center of the storm 
made landfall. 

National Oceanographic and Atmospheric Administration (NOAA) 
Gauge 8729840, located on the Pensacola Municipal Pier (Escambia 
Bay) in Florida, failed during Hurricane Ivan, but interior water
marks 
in the gauge housing indicated a 10.2-foot National Geodetic 
Vertical Datum of 1929 (NGVD) maximum water elevation (U.S. 
Army Corps of Engineers [USACE], 2004). The 10.2-foot water level 
is the highest ever recorded at the gauge site in its 82-year existence 
and is thought to reflect storm surge effects only, given that the 
gauge site is on a pier extending into the bay and that the contri
bution 
of Hurricane Ivan wave setup on the water level there was 
probably small. 

An assessment to determine the recurrence interval of Hurricane 
Ivan was performed based on similar methodology used after Hur
ricane 
Opal in 1995. However, although the impacted area was very 

Table 1-1. Wind Speeds of the Saffir-Simpson Hurricane Scale 
Strength 

Sustained Wind 
Speed (mph)* 

Gust Wind Speed 
(mph)** 

Pressure
(millibars) 

Category 1 

74-95 

90-119 

>980 

Category 2 

96-110 

120-139 

965-979 

Category 3 

111-130 

140-164 

945-964 

Category 4 

131-155 

165-194 

920-944 

Category 5 

>156 

>195 

<919 





* 1-minute sustained over open water 

** 3-second peak gust over open water 



large with storm surge elevations exceeding the mapped 100-year 
flood elevations along the open coast and throughout the bays and 
sounds, only the Pensacola tide gauge was available to use for the re
currence 
interval analysis. Using this gauge, the analysis determined 
the recurrence interval was approximately 150 years. Given the lim
ited 
data, this approximate recurrence interval applies only to the 
area surrounding the pier. Recurrence intervals in other parts of 
the affected area could have been higher or lower. Also, local effects 
(including the over washing of the barrier islands, which was not 
accounted for in the initial storm surge analysis performed over 20 
years ago) significantly alter the storm surge levels in different parts 
of the areas bays and sounds. 

To assist in the long-term recovery and mitigation effort, FEMA 
performed a Coastal High Water Mark (CHWM) study throughout 
the impacted area in Alabama and Florida. The study area extend
ed 
from Dauphin Island, along Gulf Shores, Alabama, eastward to 
Destin, Florida, and northward into the Florida Panhandle to en
compass 
Perdido, Escambia, and Blackwater Bays. The observations 
were taken at discrete points distributed along the open coast, the 
seaward and landward side of barrier islands, within the bays, and on 
the shores of several embayments. 

FEMAs CHWM Survey provided observed values of the maximum 
flood elevations throughout the area impacted by Hurricane Ivan.4 
Table 1-2 presents a comparison of the High Water Marks (HWMs) 
and BFEs at the MAT investigation sites. 

4 FEMA 2004. Hurricane Ivan Flood Recovery Maps, http://www.fema.gov/ivanmaps/ 



Table 1-2. Comparison of HWMs and BFEs for MAT Investigation Sites
MAT Investigation 
Site 

Flood Source 

HWMs* 
(feet**) 

FIS Stillwater 
Elevations 
(feet**) 

BFEs (feet**) 

Alabama 

Gulf Shores 

Gulf of Mexico 

10-14 

10.0*** 

12-13 

Orange Beach/ 
Perdido Key 

Gulf of Mexico 

12-15 

9.9*** 

12-13 

Florida 

Gulf Beach Heights 

Perdido Bay 

6-7 

4.3 

5 

Seaglades 

Big Lagoon 

14 

8.0 

8-12 

Pensacola Naval Air 
Station 

Pensacola 
Bay 

10-13 

8.0 

8-12 

Pensacola 

Escambia Bay 

10-14 

5.9/7.2 

6-9 

South Gulf Breeze 

Santa Rosa 
Sound 

10-14 

8.0 

9-12 

West Gulf Breeze 

Pensacola 
Bay 

10-12 

8.0 

7-12 

Northeast Gulf Breeze 

Escambia Bay 

7 

4.9 

5 

Oriole Beach 

Santa Rosa 
Sound 

11 

8.0 

8-12 

Floridatown 

Escambia Bay 

13-16 

7.9 

11-12 

Avalon Beach 

Escambia Bay 

12 

7.9 

9 

Pensacola Beach 

Gulf of Mexico 

6-12 

10.5**** 

11-16 





* HWMs are approximate stillwater elevations and do not include wave heights. 

** In Alabama, elevations are referenced to the North American Vertical Datum of 1988. In Florida, elevations are 
referenced to the NGVD. 

*** Includes wave setup of 2.2 feet. 

**** Includes wave setup of 2.5 feet. 

 



The measured CHWMs along the open beaches of the Gulf of Mex
ico 
are above the 100-year elevations from immediately west of Gulf 
Shores, Alabama, to just east of Destin, Florida. The measured CHWMs 
include the effects of wave setup. Data taken only from building inte
riors 
was used to evaluate the extent of the zone thought to be above 
the 100-year values. This eliminated the possibility of inadvertently in
cluding 
wave height. 

Surge elevation contours were mapped in the impacted areas of Bald
win, 
Escambia, Santa Rosa, and Okaloosa Counties. The contours are 
based upon the surveyed CHWM elevations (referenced to the North 
American Vertical Datum of 1988). The CHWM elevations were used 
to find patterns in the coastal storm surge as it pushed against the open 
coast and into the inland bays. The known path and landfall location 
of Hurricane Ivan, together with the knowledge of how storm surge 
propagates inland, allowed surge contours to be drawn across the ar
eas 
where the CHWMs indicate a change in storm surge elevation. 
Because of the inherent uncertainty and the random and irregular 
spacing of CHWMs, the surge contours represent a generalized maxi
mum 
storm surge elevation, and required professional judgment in 
their creation. Within certain surge contours, CHWMs may be higher 
or lower than the contours if they did not fit the overall pattern as
sessed 
from the CHWMs. 

Wave effects were not considered in developing the storm surge con
tours. 
To estimate the wave heights at the shoreline, standard FEMA 
methodology may be used, where the depth of water at the shoreline 
is multiplied by 1.55 to obtain the height of the wave crest above the 
ground at that point. 

Surge elevation contours in Baldwin County are shown in Figure 1-2. 
HWM elevations along the open coast of Baldwin County were general
ly 
2-3 feet higher than the effective BFEs shown on the FIRM. However, 
the HWM elevations along some of the inland bays (Bayou St. John, 
Perdido Bay, and Wolf Bay) were found to differ from the BFEs by only 
+/- 1 foot. It should be noted that several HWM elevations could not 
be compared to effective BFEs because the areas are currently mapped 
as Zone X, without established elevations. 



Figure 1-3 shows the surge elevation contours in Escambia County. Here, 
the HWM elevations in the inland bay areas varied greatly from the ef
fective 
BFEs. Along Perdido Bay, the HWM elevations were found to be 
approximately 0-2 feet higher than the effective BFEs. Along Big Lagoon, 
HWMs were generally 6-8 feet higher than the BFEs. Along Pensacola 
Bay, they were about 4 feet higher, and along Escambia Bay, generally 
5 feet higher. As with Baldwin County, it should be noted that several 
HWM elevations could not be compared to effective BFEs because the 
areas are currently mapped as Zone X, without established elevations. 

Figure 1-2. 
Surge elevation contours 
in Baldwin County, 
Alabama 


Figure 1-3. 
Surge elevation contours 
in Escambia County, 
Florida 



Figure 1-4 shows the surge elevation contours in Santa Rosa County. 
The HWM elevations in Santa Rosa County were generally found 
to be much higher than the effective BFEs in the inland bay areas. 
Along Pensacola Bay, the HWMs were generally 2-6 feet higher than 
the effective BFEs. However, there were also instances where the two 
elevations were equal, such as at Garcon Point along Pensacola Bay 
(both equal to 10 feet). Along Escambia Bay, the HWMs were found 
to be approximately 3-4 feet higher than the BFEs, and along East 
Bay, approximately 3-6 feet higher. Along the northern shoreline of 
Santa Rosa Sound, the HWM elevations differed from the BFEs by 
about +2 feet, while along Blackwater Bay, the HWMs were about 2- 
4 feet higher than the BFEs. As with the other impacted counties, 
several HWM elevations could not be compared to effective BFEs 
because the areas are currently mapped as Zone X, without estab
lished 
elevations. 

Surge elevation contours for Okaloosa County are shown in Figure 1-5. 
HWM elevations along the open coast of Okaloosa County were gener
ally 
equal to or lower than the effective BFEs shown on the FIRM. The 
HWM elevations along some of the inland bays, such as Boggy Bay
ou, 
were found to be 2-3 feet lower than the effective BFEs. Again, it 
should be noted that several HWM elevations could not be compared 
to effective BFEs because the areas are currently mapped as Zone X, 
without established elevations. 

Figure 1-4. 
Surge elevation contours 
in Santa Rosa County, 
Florida 



The Hurricane Ivan CHWM data clearly show that the storm surge 
levels varied within the bays. This observation indicates that the 100- 
year level determined from the Pensacola Bay tide gauge applies to a 
limited area within the bay. Extreme storm surge conditions extended 
along a 90-mile length of the open coast reaching 5 miles west and 85 
miles east of the storm track. As an initial assessment, it is reasonable 
to assume that conditions capable of producing hurricane storm surge 
elevations exceeding the 100-year recurrence magnitudes extended 
inland over this whole length of the coast. 

The NOAA Sea, Lake and Overland Surges from Hurricanes (SLOSH) mod
el 
prediction run output shows that the maximum surge conditions 
moved across the area as the storm tracked across the coast. Figure 1-6 
shows the results of the SLOSH model for Hurricane Ivan. The hurri
cane 
crossed the coast in the general area of Gulf Shores and Orange 
Beach. Because it tracked north-northeast from there, Mobile Bay and 
most of the Alabama coast was exposed to the weaker left-front storm 
quadrant. In Alabama, the major storm surge struck Orange Beach, 
Gulf Shores, and the peninsula between Bon Secour Bay (the south
eastern 
corner of Mobile Bay) and the open gulf. In Florida, the first 
major surge was along the open coast, at Perdido Key. 

Figure 1-5. Surge 
elevation contours in 
Okaloosa County, Florida 



In general, the results of the SLOSH model correlated with the ac
tual 
storm surge elevations from Ivan as compared by the MAT and 
NOAA. The results of FEMAs CHWM study are presented in Fig
ures 
1-7 through 1-10 for Alabama and Figures 1-11 through 1-17 for 
Florida. The points are shown to differentiate between surge, wave 
runup, and wave height data. Figure 1-7 shows the effect of the storm 
on Dauphin Island and the lower western part of Mobile County. 
Along the open coast, CHWM elevations reached 12 feet and ranged 
between 3 and 6.8 feet on the landward side of the island and the 
more protected areas. 

Figure 1-6. 
The SLOSH model 
Envelope of High Water 
(EOHW) for Pensacola 
Bay, Florida 



Figures 1-9 and 1-10 show the CHWM elevations in Orange Beach, 
Ono Island, West Beach, and Fort Morgan. The surge height, deter
mined 
from water marks in sheltered locations such as interior rooms, 
ranged between 12 and 14.5 feet along this portion of the open Ala
bama 
shore. Much of the beach system was overtopped or overwashed. 

Figure 1-7. 
CHWM surveyed 
elevations for Dauphin 
Island area 


Figure 1-8. 
CHWM surveyed 
elevations for Upper 
Mobile Bay area 



Little Lagoon filled with water, but the effects of wave setup may have 
been smaller than on the open coast, accounting for slightly lower 
CHWM elevations along its north shore. 

The open gulf CHWM elevations decrease slightly near Perdido Pass, 
possibly because of the flow into Perdido Bay. Figure 1-10 shows that 
CHWM elevations in the lower Perdido Bay were 6 to 7 feet. Data from 
the Florida side of upper Perdido Bay (not shown) indicated that the 
water level increased towards the head of the bay with values in the 
range of 8.5 to 9 feet at its northern end. The surge was then amplified 
as it propagated up the lower Perdido River such that the U.S. Geo
logical 
Survey (USGS) gauge at Barrineau Park indicated a level of 14 
feet above the preceding river level. A similar effect appears to have 
affected the head of Wolf Bay as shown on Figure 1-10. 

Figure 1-9 shows that the CHWM elevations were much lower along 
the eastern shore of Mobile Bay in Baldwin County compared to the 
open coast. Data on Figures 1-8 and 1-9 show that elevations on the or
der 
of 6.5 feet were characteristic of this eastern shore of Mobile Bay. 

Figure 1-9. 
CHWM surveyed 
elevations for West 
Beach/Fort Morgan area 



The great majority of the CHWM data points collected for Florida rep
resent 
watermarks from protected locations such as interior walls of 
coastal buildings. In some areas, the storm damage was so extensive 
that coastal roads were washed out or entirely buried with sand. These 
areas are shown as being inaccessible on the figures. Many of the gulf 
beaches in this area are within parks or National Seashores. These nat
ural 
areas contained scant record of the coastal storm surge compared 
to the built-up areas. 

The highest CHWM elevations in Florida occur in the Perdido Key 
area (see Figure 1-11). Much of this barrier island was overtopped. 
Such overtopping of the barrier island would allow a huge volume 
of water to enter Big Lagoon, and this could explain the very high 
CHWM elevations along the mainland coast (Figure 1-11). Figure 1-11 
also shows that there was a noticeable difference in the CHWM eleva
tion 
over the length of Perdido Bay. Both Ono Island and Innerarity 
Point have high ground well above the flood elevation. It appears that 
bay water was displaced towards the upper bay faster than it could be 
refilled from the gulf. This results in a differential in the CHWM eleva
tions 
of about 3 feet over the 12-mile length of the open bay. 

 

Figure 1-10. 
CHWM surveyed 
elevations for Orange 
Beach/Ono Island 



Figure 1-12 shows the area between the entrance to Pensacola Bay and 
Garcon Point in the northwest corner. Much of the barrier island was 
subject to extensive damage by the surge. This includes overtopping 
and overwashing at many locations. The road was buried in many plac
es, 
and access to the island was restricted for weeks. The surge along 
the Pensacola Beach Barrier Island may have been limited by the low 
height of the land. With nothing to back up against, the surge passed 
over the island into Santa Rosa Sound and lower Pensacola Bay. The 
differences in the CHWM elevations between the gulf and sound sides 
support this inferred surge behavior. 

The Santa Rosa Peninsula, which lies behind the barrier island, has 
ground that is much higher than the maximum surge elevation. Figure 
1-12 shows that the surge setup along the southern peninsula shore
line 
had elevations on the order of 11 and 12 feet. This is in contrast 
with values of 6 to 8 feet only 2 miles away across Santa Rosa Sound. 
These CHWM values also demonstrate that the volume of water within 
the Sound increased dramatically during the surge. 

Figure 1-12 shows also that wind-driven water piled up along the 
south-facing shores of the Naval Air Station, the western suburb of 
Warrington, and the Port of Pensacola. This also brought high surge 
levels into Bayou Grande, Bayou Chico, and Bayou Texar. Maximum 
surge elevations throughout Pensacola Bay and the lower portions of 
Escambia and Blackwater Bays appear to have been on the order of 
9.5 to 11 feet. 

Figure 1-11. CHWM 
surveyed elevations 
for Innerarity Point and 
Perdido Key areas 



Figures 1-13 and 1-14 are centered on the Escambia and Blackwater 
arms of the estuary. In both cases there is a clear pattern of surge ampli
fication 
towards the heads of these bays. The highest observed elevation 
in Escambia Bay was 16 feet in Floridatown at the north end of Escambia 
Bay. The Ward Basin is near the north end of Blackwater Bay just south 
of the I-10 highway. Here, the surge elevation reached close to 13 feet. 
In general, the CHWM elevations are a few feet higher along the shores 
of the arms of the estuary than in the main portion of Pensacola Bay. 

Figure 1-12. 
CHWM surveyed 
elevations for Pensacola/ 
Gulf Breeze area 


Figure 1-13. 
CHWM surveyed 
elevations for Upper 
Escambia Bay area 



Figure 1-15 shows the eastern portion of Santa Rosa Sound near Na
varre 
and the East Bay arm of the Pensacola Estuary. The CHWM 
elevations along the open gulf shore are consistent with the values 
further west. Considerable portions of this part of the island were over
topped 
or overwashed. Much of the barrier island was inaccessible due 
to road damage and burial. 

Figure 1-14. 
CHWM surveyed 
elevations for Blackwater 
Bay area 


Figure 1-15. 
CHWM surveyed 
elevations for Holley 
Navarre area 



The mainland shore of Santa Rosa Sound experienced a high surge 
that may have decreased slightly going east. However, this trend may 
be more apparent than real. It was noted that there appeared to be 
a correlation between the surge levels along the north shore of San
ta 
Rosa Sound and the amount of shielding provided by the barrier 
island. Much of this island is part of Eglin Air Force Base and is unde
veloped. 
The height of the dunes varies along the island, and there are 
patches of wooded areas. It was in the regions between the dunes and 
wooded areas where overtopping and overwashing occurred. 

Figures 1-16 and 1-17 show data taken at the eastern end of Santa Rosa 
Sound and near Fort Walton Beach. Open gulf CHWMs approaching 
this 13-foot value have been located east of East Pass, which is the in
let 
into Choctawhatchee Bay, as well. This suggests that a coastal surge 
was generally at 12 feet or higher along more than 90 miles of the gulf 
shoreline between eastern Alabama and Destin, Florida. This open 
coast surge remained high much further to the east, but the land along 
the shore is high with varying relief so that the surge did not penetrate 
significantly behind the beach systems except at a few locations. 


Figure 1-16. 
CHWM surveyed 
elevations for Fort Walton 
area 



Preliminary results of the CHWM study show that storm surge levels 
varied throughout the bays and that these elevations exceeded the 
100-year surge elevations. Based on field observations and the CHWM 
study, the barrier islands were overtopped, which produced extremely 
high surge elevations in the back bays and, in some cases, elevations 
close to or nearly as high as the elevations on the open coast. The 
overtopping of the barrier islands was not accounted for in the surge 
modeling, which was performed over 20 years ago and used in the 
current Flood Insurance Studies (FISs). Numerous hurricanes have 
impacted the Alabama and Florida Panhandle coastline and severely 
eroded many of the high dunes that were modeled in the surge analy
sis. 
Because of the changes in the barrier islands, a new surge model 
would likely produce higher surge elevations, resulting in higher BFEs 
in the back bays. 

Figure 1-17. 
CHWM surveyed 
elevations for Destin area 



1.1.2 Wind Analysis and Discussion 

The NWS and the NHC reported that Hurricane Ivan made landfall 
just west of Gulf Shores, Alabama, on September 16, 2004, at 2:02 
a.m. (Central Daylight Time). After crossing the barrier islands, Ivan 
turned north-northeastward across eastern Mobile Bay and weakened 
to a tropical storm as it crossed the central portion of Alabama. 

Wind speeds at MAT investigation sites have been estimated based on 
a review of the wind speed measurements and the plots shown later in 
this section. The results listed in Table 1-3 correspond to the locations 
shown in Figure 1-23. 

The CHWM study had the following recommendations on how to use the CHWM information to 
assist in the recovery effort from Hurricane Ivan: 

 Compare the Hurricane Ivan CHWMs to the flood elevation data on the effective or preliminary 
FIRMs. These comparisons can help determine where the updated flood hazard data was 
supported by the flooding or where new detailed studies should be performed to update the 
maps. They can help illustrate deficiencies of the existing maps. 

 An evaluation is needed of the recurrence intervals of the surge conditions across the area. 
This will vary from place to place owing to distance from the storm track and local geographic 
effects. Preliminary evidence suggests that much of the area that experienced the most 
severe surge conditions was exposed to more than 100-year conditions. 

 Compare the Ivan CHWMs to CHWMs from other significant flood events. This will identify 
areas of repetitive flooding that can assist in determining locations that would make good 
flood mitigation projects. 

 Complete detailed engineering analyses to determine flood elevations in the areas where 
deficiencies of the existing FEMA maps have been identified, or in areas where property loss 
occurred and there were no previous studies. 

 The locations and severity of the Ivan CHWMs can help identify areas of concern for future 
mitigation projects when funding for such projects becomes available. 

 Use these CHWMs to evaluate the success of completed mitigation projects. The flood depths 
that occurred during Ivan can be used to estimate potential damage that could have occurred 
to buildings that have been bought out and removed as part of mitigation projects already 
completed. Documentation of the damages avoided can be used as success stories to 
further support the mitigation efforts. 

 Use the CHWM data to calibrate and validate FEMAs Hazards US  Natural Hazards Loss 
Estimating Methodology (HAZUS-MH) flood model. 



Figure 1-18 shows the approximate extent of tropical storm winds (39 
to 73 mph, 1-minute sustained) and hurricane force winds (greater 
than 74 mph, 1-minute sustained) for Hurricane Ivan. These wind 
speed contours are based on a combination of actual wind readings and 
wind field models. The first wind field model is the H*wind program 
(Weather and Forecasting, September 1996) produced by the Atlantic 

Table 1-3. Estimated Maximum 3-Second Gust Wind Speeds at 10-Meters for MAT Investigation Sites 
(variations for terrain are provided) 

MAT Investigation Site 

3-Second Gust Speed Estimate 
for Exposure C (Open Terrain) 

3-Second Gust Speed 
Estimate for Exposure B 
(Suburban Terrain) 

Alabama 

Gulf Shores 

105  115 mph 

90  100 mph 

Orange Beach 

105  120 mph 

95  110 mph 

Florida 

Perdido Key 

110  125 mph 

95  110 mph 

West Gulf Beach Heights 

105  120 mph 

90  105 mph 

Gulf Beach Heights 

105  120 mph 

90  105 mph 

Seaglades 

105  120 mph 

90  105 mph 

Pensacola Naval Air Station 

105  115 mph 

90  100 mph 

West Pensacola 

105  115 mph 

90  100 mph 

East Pensacola 

105  115 mph 

90  100 mph 

West Gulf Breeze 

105  115 mph 

90  100 mph 

Northeast Gulf Breeze 

95  110 mph 

80  95 mph 

Oriole Beach 

95  110 mph 

85  95 mph 

Floridatown 

95  110 mph 

80  95 mph 

Avalon Beach 

95  110 mph 

80  95 mph 

East Side of Escambia Bay 
Near Bridge to Gulf Breeze 

95  110 mph 

80  95 mph 

Pensacola Beach 

105  115 mph 

90  105 mph 







Oceanographic and Meteorological Laboratorys Hurricane Research 
Division (HRD). The second is the FEMA Hazards US  Natural Hazards 
Loss Estimating Methodology (HAZUS-MH) that was used by Applied 
Research Associates (ARA) with some adjustments. The maximum re
corded 
Exposure C (open terrain) wind speeds for specific locations 
in Alabama and Florida are presented in Figure 1-19. 

Figure 1-18. 
Extent of hurricane and 
tropical storm force 
winds for Hurricane Ivan 



Despite the large number of wind speed recordings that were available 
throughout the area impacted by Hurricane Ivan, measurements were 
not available at all locations investigated by the MAT. Thus, damage 
investigators and weather scientists must estimate wind speeds using a 
variety of methods, the most reliable of which are scientifically based 
wind field models. The best known model for estimating wind speed 
variations available in the public domain is H*wind from NOAAs 
HRD5. Past experience with H*wind-based analyses suggests that the 
model provides reasonably accurate estimates of the maximum wind 
speeds seen over significant areas impacted by the storm. 


Figure 1-19. 
Maximum recorded wind speeds from Hurricane Ivan normalized to 3-second peak 
gust at 10 meters, Exposure C (open terrain) 

5 Powell, Mark D., Houston, Samuel H. and Reinhold, Timothy A., Hurricane Andrews 
Landfall in South Florida. Part I: Standardizing Measurements for Documentation of 
Surface Wind Fields, Weather and Forecasting, Vol. 11, No. 3, September 1996. Powell, 
Mark D., and Houston, Samuel H. Hurricane Andrews Landfall in South Florida. Part II: 
Surface Wind Fields and Potential Real-Time Applications Weather and Forecasting, 
September 1996. 



The largest differences between measured and predicted values typi
cally 
occur for lateral distributions of winds and the decay of winds as 
the storm progresses inland. Contours of sustained, 1-minute, wind 
speeds from the H*wind analysis avre shown in Figure 1-20. A second 
modeling approach that usually produces reasonable estimates of 
maximum wind speeds and lateral distributions of winds involves use 
of wind field based models such as the one in FEMAs HAZUS-MH loss 
estimation methodology.6 The wind field analysis conducted by ARA 
using this model is shown in Figure 1-21. The maximum wind speed 
estimates for Hurricane Ivan (when normalized) agree within about 
3 mph between the H*wind and ARA analyses despite their indepen
dent 
approaches to making wind speed estimates. There are, however, 
larger differences between wind speeds at specific locations within the 
wind field. The estimated wind speed ranges for the various locations 
visited by the MAT are shown in Table 1-3. 


Figure 1-20. 
Wind swath contour plot 
(1-minute sustained 
winds at 10 meter 
elevation) based on 
H*wind analysis 

6 Vickery, Peter J., Skerlj, Peter, Steckley, Andrew and Twisdale Lawrence A.,Hurricane 
Wind Field Model for Use in Hurricane Simulations Journal of Structural Engineering, 
ASCE, Oct. 2000, pp 1203-1221. 



A number of wind speed measurements were recorded at locations 
along the Alabama and Florida Panhandle coasts. Notable wind speeds 
recorded for Hurricane Ivan were obtained at the following official lo
cations 
as shown in Table 1-4. 

Figure 1-21. 
Wind swath contour plot 
(3-second gust at 
10-meter elevation) 
based on HAZUS-MH 
wind field methodology 
(ARA). The stars and 
letters indicate official 
stations reporting data 
for at least part of the 
storm. 



Table 1-4. Notable Wind Speeds Recorded for Hurricane Ivan
Recording Site 

Location 

Wind 

Official Locations 

Alabama 

Grand Bay (AWIS) 

71 mph (gust)* 

Mobile (NWS-KMOB) 

75 mph 

Florida 

Eglin Air Force Base (KVPS) 

81 mph (gust)* 

Pensacola (NWS-KPNS) 

100 mph 

Pensacola Naval Air Station (KNPA) 

107 mph (gust)* 

 Instrument stopped recording values after this reading and may 
have missed peak. 

* Averaging time for gust 
measurements unknown. 
Estimated to be between 2 and 
5 seconds. 

Universities 
deploying 
portable 10-meter 
meteorological 
towers at various 
locations along the 
coast 

Alabama 

Fairhope (30.480N 87.870W) by Florida Coastal Monitoring 
Program Tower 2 

89 mph 

Gulf Shores Airport (30.290N 87.670W) by University of Oklahoma 
DOW3 

109 mph 

Florida 

Pensacola Regional Airport (30.480N 87.190W) by Florida Coastal 
Monitoring Program Tower 1 

106 mph 

Destin Airport by SBCCOM/CR5000 (30.40N 86.480W) 

89 mph 

Other notable 
measurements 
at non-standard 
heights and 
exposures from a 
number of sources 

Alabama 

Fairhope (30.5N 87.89W) by Texas Tech University WEMITE 2 
 Obstacles for some upwind directions may have reduced the 
observed maximum values 

73 mph 

Gulf Shores Airport (30.3N 87.66W) by Texas Tech University 
WEMITE 1  (Actual values at 9.1 meter elevation of 102 mph [3- 
second gust]) 

104 mph 

Wolf Field MIPS (30.43N 87.54W)  (Actual values at 4 meter 
elevation of 87 mph [3-second gust]) 

109 mph 

Sailboat Odalisque in Wolf Bay  (Actual value at 22 meter 
elevation of 145 mph gust with about 2 miles of open water 
exposure for strong wind direction) 

124 mph 

Florida 

FCMP house ~ 1-mile east of Big Lagoon State Recreation Area 
 (Actual value of 91 mph [2-second gust] at 7 meters elevation 
in suburban area) 

119 mph (107 mph for 
Exposure B) 

FCMP house ~ 8-miles east of Gulf Breeze  (Actual value of 82 
mph [2-second gust] at 7 meters elevation in suburban area) 

107 mph (96 mph for 
Exposure B) 





Note: Wind speeds provided are 3-second peak gust wind speeds at 10 meters, Exposure C (open terrain) except 
where noted otherwise. 



1.2 Historical Hurricanes (Frequency of 
Hurricanes and Tropical Storms in Eastern 
Coastal Alabama and Florida Panhandle 

Gulf Shores and Dauphin Island, Alabama; and Fort Walton, 
Pensacola, and Destin, Florida, have been affected or direct
ly 
hit by past hurricanes that made landfall in the vicinity of 
Hurricane Ivans landfall. Historical information shows that four of 
these cities have been brushed or hit by a hurricane or tropical storm 
approximately once every 3 years; Gulf Shores has been brushed or 
hit approximately every 4 years. For a direct landfalling hurricane 
(within 40 miles), the statistics show the likelihood of such an event 
as once every 8.9 years for Fort Walton and Pensacola, approximately 
once every 12 years for Destin, and approximately once every 13 years 
for Gulf Shores and Dauphin Island. Figure 1-22 highlights some of 
these hurricanes and storms with paths similar to that of Hurricane 
Ivan; three of the hurricanes are described below. 

Hurricane Frederic, 1979 

Hurricane Frederic was the most severe hurricane to strike the Mo
bile, 
Alabama, area since 1926. It was a Category 3 hurricane, making 
landfall on Dauphin Island and passing to the west of Mobile. Storm 
tides of 8 to 12 feet above normal were reported from Pascagoula, Mis
sissippi, 
to western Santa Rosa Island, Florida. Frederic was notable 
due to the extent and magnitude of damage to coastal construction, 
including the destruction of many barrier island homes that were ele
vated 
on pilings to the 100-year stillwater level as required by the NFIP 
at the time. The occurrence of Frederic was a driving force in modify
ing 
NFIP minimum construction standards to require elevation to the 
wave crest elevation rather than the stillwater level. 

Hurricane Opal, 1995 

Opal became a tropical storm near the north-central coast of the Yu
catan 
Peninsula at the end of September 1995. After meandering over 
the southwest Gulf of Mexico, Opal became a hurricane and gradu
ally 
accelerated toward the northeast gulf. Early on October 4th, Opal 
intensified explosively and, according to NHC reports, its maximum 
sustained winds reached 150 mph. However, the hurricane weakened 
when its center crossed the coast near Pensacola Beach, Florida. Fifty 
people died in Guatemala and Mexico, and 9 in the United States. 
The total damage approached $3.5 billion (year 2000 dollars) and in
cluded 
extensive flood damages. 



Hurricane Georges, 1998 

Hurricane Georges 17-day journey resulted in seven landfalls, extend
ing 
from the northeastern Caribbean to the coast of Mississippi, and 
602 fatalities  mainly in the Dominican Republic and Haiti. Georges 
made landfall during mid-morning of September 25 in Key West, Flor
ida, 
with maximum sustained winds of 104 mph, according to NHC 
reports. After moving away from Key West, Georges turned more to 
the northwest, then north-northwest, and gradually slowed down on 
September 26 and 27. The hurricane made landfall near Biloxi, Mis
sissippi, 
on the morning of September 28 with estimated maximum 
sustained 1-minute winds of 104 mph. After landfall, the system mean
dered 
around southern Mississippi and was downgraded to a tropical 
storm on the afternoon of September 28. The total estimated damage 
from Georges is $5.9 billion (year 1998 dollars). 

Figure 1-22. 
Historical hurricane and 
tropical storm paths 



1.3 FEMA Mitigation Assessment Teams 

Most people know of FEMA for its response to disasters and its 
assistance to the impacted people. Other important contribu
tions 
of the agency are the science and engineering studies 
that it performs before and after disasters to better understand natu
ral 
and manmade events. These studies of disasters are conducted 
with the intent of reducing the number of lives lost to these events 
and minimizing the damages and economic impact on the communi
ties 
where these events occur. 

Since the mid-1980s, FEMA has sent MATs to Presidentially Declared 
Disaster areas to evaluate building performance during hurricanes. 
The MAT determines the adequacy of current building codes, oth
er 
construction requirements, and building practices and materials. 
Based on estimates from preliminary information of the potential type 
and severity of damages in the affected area(s) and the magnitude 
of the expected hazards, FEMA determines the potential need to de
ploy 
one or more MATs to observe and assess damage to buildings and 
structures from wind, rains, and flooding associated with the storm. 
These teams are deployed only when FEMA believes the findings and 
recommendations derived from field observations will provide design 
and construction guidance that not only will improve the disaster re
sistance 
of the built environment in the impacted state or region, but 
also will be of national significance to all hurricane-prone regions. 

1.3.1 Methodology 

In response to a request for technical support from the FEMA Disaster 
Field Offices in Mobile, Alabama, and Orlando, Florida, FEMAs Miti
gation 
Division deployed a MAT to Alabama and Florida to evaluate 
building performance during Hurricane Ivan and the adequacy of cur
rent 
building codes, other construction requirements, and building 
practices and materials. Hurricane Ivan approximated a design flood 
event on the barrier islands in an area with relatively recent develop
ment. 
This provided a good opportunity to assess the adequacy of NFIP 
floodplain management requirements as well as current construction 
practices in resisting storm surge damage. FEMA was particularly in
terested 
in evaluating damages to buildings in coastal AE Zones where 
coastal construction methods are not required. 

Field investigations to assess building conditions in selected areas af
fected 
by the hurricane began on September 18 and concluded on 
October 3, 2004. The team conducted ground inspections across the 



width of the storm track from its landfall near Gulf Shores, Alabama, 
to Oriole Beach, Florida, as shown in Figure 1-23 below. Aerial inspec
tions 
were conducted from Dauphin Island, Alabama, to the East Pass 
at Destin, Florida. The aerial inspections were made possible by the 
Office of the Federal Coordinator for Meteorological Services and 
Supporting Research (OFCM) which serves as the executive agent for 
the Working Group for Natural Disaster Reduction and Post-Storm 
Data Acquisition (WG/NDR/PSDA). FEMA is a member of the WG/ 
NDR/PSDA. 

1.3.2 Team Composition 

The MAT included engineers and other experts from FEMA Head
quarters 
and the Regional Office and from the design and construction 
industry. Team members were drawn from FEMAs database of nation
al 
experts. Their fields of expertise included structural, wind, and civil 
engineering; architecture; coastal science; and building codes. 


Figure 1-23. Some of the locations visited by the MAT 



F 


C H A P T E R 2 

2-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

2 

Floodplain 
Management 
Regulations and 
Building Codes and 
Standards 

Floodplain management regulations, and building codes and stan
dards, 
are adopted and enforced to regulate construction in at-risk 
areas. The floodplain regulations applicable to the affected areas are 
discussed in Section 2.1. Section 2.2 discusses the building codes and 
standards used to regulate construction in Alabama and Florida. The 
building code requirements specific to floods are discussed in Subsec
tions 
2.2.1 (Alabama) and 2.2.2 (Florida). Subsections 2.2.3 and 2.2.4 
discuss the Alabama and Florida building code requirements specific 
to wind, respectively. 

2.1 Floodplain Management Regulations 

All of the communities visited by the MAT participate in the 
NFIP and have adopted floodplain management regulations 
that meet or exceed minimum NFIP requirements. Up until 
2000, these requirements generally were contained only in commu
nity 
floodplain management ordinances. Starting in 2000, however, 
flood-resistant provisions and floodplain management requirements 
began to be incorporated into model building codes (e.g., the In
ternational 
Building Code [IBC], the International Residential Code 
[IRC], and the National Fire Protection Association [NFPA] 5000). 



C H A P T E R 2 

FLOODPLAIN MANAGEMENT REGULATIONS AND BUILDING CODES AND STANDARDS 

2-2 

 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

Thus, if a community in Alabama has adopted a recent edition of these 
codes (without amending the code to remove the flood provisions), 
it will have two avenues for enforcing flood-resistant design and con
struction 
requirements  the floodplain management ordinance and 
the building code (see Figure 2-1). More details are contained in Sec. 
2.2.1 of this report. 

This is not the case in Florida, where the Florida Building Code (FBC) 
is in place. Chapter 31 of the FBC specifically defers floodplain man
agement 
issues to the community floodplain management ordinance. 
However, a companion set of design requirements for coastal construc
tion 
seaward of Floridas Coastal Construction Control Line (CCCL) 
has been placed in Chapter 31 of the FBC (see Figure 2-2). Many of 
the CCCL requirements are similar in nature to NFIP requirements 
(e.g., pile foundations, elevation above the 100-year wave crest eleva
tion, 
etc.). More details are contained in Sec. 2.2.2 of this report. 


Figure 2-1. Floodplain Management Regulations and Building Design, Alabama 



FLOODPLAIN MANAGEMENT REGULATIONS AND BUILDING CODES AND STANDARDS 

2.1.1 Flood Studies, Flood Maps, and Floodplain Management 
Regulations 

FEMA provides participating communities with a Flood Insurance Rate 
Map (FIRM) and Flood Insurance Study (FIS). Several areas of flood 
hazard are commonly identified on the FIRM. One of these areas is 
the Special Flood Hazard Area (SFHA), which is defined as the area 
that will be inundated by the flood event having a 1-percent chance 
of being equaled or exceeded in any given year. The 1-percent annual 
chance flood is also referred to as the base flood or 100-year flood. 
SFHAs labeled as Zone AE have been studied by detailed methods 
and show Base Flood Elevations (BFEs). SFHAs labeled as Zone VE 
are along coasts and are subject to additional hazards due to storminduced 
velocity wave action. BFEs derived from detailed hydraulic 
analyses are shown within these zones. (Zone VE is used on new and 
revised maps in place of Zones V1-V30.) Mandatory flood insurance 
purchase requirements apply in all SFHAs.1 


Figure 2-2. Floodplain Management Regulations and Building Design, Florida 

* Ch. 31 defers to Floodplain Management Ordinance, contains CCCL requirements 

** Flood loads only via load combination, FBC Ch. 16 

 

1 Note: The term Zone A is used in this report to represent those flood hazard zones identified on the FIRMs as A1- 
30, AE, and AO, and Zone V is used to represent those flood hazard zones identified on the FIRMs as Zone V1-30 
and VE. Where used in this report, these terms are not intended to describe approximate or unnumbered zones (i.e., 
zones without BFEs). Approximate and unnumbered zones will be identified specifically as such. Further, when the 
term BFE is used in conjunction with Zone A in this report, it should be taken to mean the BFE for Zones A1-30 
and AE, and the depth number shown on the FIRM for Zone AO. 



The zone designation and the BFE are 
critical factors in determining what re
quirements 
apply to a building and, as 
a result, how it is built. For example, 
the NFIP minimum requirements for 
buildings built in Zone VE (Coastal 
High Hazard Areas) are: 1) the build
ing 
must be elevated on pile, post, pier, 
or column foundations, 2) the building 
must be adequately anchored to the 
foundation, 3) the building must have 
the bottom of the lowest horizontal 
structural member at or above the BFE, 
and 4) the building design and method 
of construction must be certified by a 
design professional. The area below the 
BFE must be free of obstructions; if en
closed, 
the enclosure must be made of 
lightweight wood lattice, insect screen
ing, 
or breakaway walls. 

In the Zone AE, the NFIP requires that 
the top of the lowest floor of a building 
must be at or above the BFE; however, 
there are no standards for foundations 
other than the general performance 
standard that the building be anchored 
to resist floatation, collapse, and lateral 
movement. In an A Zone, non-residen
tial 
buildings can be flood-proofed with 
their walls made substantially imperme
able 
to the passage of floodwater. 

For buildings built in Zones B, C, and 
X (areas of moderate or minimal haz
ard 
from the principal source of flood 
in the area), there are no NFIP build
ing 
requirements, even for buildings built on barrier islands, because 
these buildings are outside of the SFHA. 

Many of the buildings on shallow foundations that failed in Hurricane 
Ivan were built in areas that were designated as Zone B, C, or X at the 
time of construction. These areas were exposed to V-Zone conditions 
during Hurricane Ivan as a result of long-term erosion or the erosion 
that occurred during the storm. 

DESCRIPTION OF FLOOD ZONES 

Zones X, B, and C. These zones identify areas 
outside of the SFHA. Zone B and shaded Zone 
X identify areas subject to inundation by the 
flood that has a 0.2-percent probability of being 
equaled or exceeded during any given year. This 
flood is often referred to as the 500-year flood. 
Zone C and unshaded Zone X identify areas above 
the level of the 500-year flood. The NFIP has no 
minimum design and construction requirements 
for buildings in Zones X, B, and C. 

V Zone. The portion of the SFHA that extends from 
offshore to the inland limit of a primary frontal 
dune along an open coast, and any other area 
subject to high-velocity wave action from storms 
or seismic sources. The FIRMs use Zones VE and 
V1-30 to designate these Coastal High Hazard 
Areas. These SFHAs are subjected to inundation 
during the flood that has a 1-percent chance of 
being equaled or exceeded during any given year. 
This flood is referred to as the 100-year flood. 

A Zone. The portion of the SFHA not mapped as 
a V Zone. Although FIRMs depict A Zones in both 
riverine and coastal floodplains (as Zones A, AE, 
A1-30, and AO), the flood hazards and flood forces 
acting on buildings in those different floodplains 
can be quite different. In coastal areas, A Zones 
are subject to wave heights less than 3 feet and 
wave runup depths less than 3 feet. Flood forces 
in A Zones in coastal areas are not as severe 
as in V Zones, but are still capable of damaging 
or destroying buildings on shallow foundations. 
For this reason, different design and construction 
standards are recommended (by the MAT and 
others) in coastal A Zones. 

For NFIP flood zone definitions, refer to 44 CFR 
64.3. 



2.1.2 Higher Regulatory Standards 

One of the goals of the MAT was to investigate building failures in 
mapped Zones AE, B, C, and X. The MAT determined that some of the 
communities visited have adopted more stringent design and construc
tion 
requirements for these zones (e.g., Santa Rosa Island Authority), 
and that structural damage to newer buildings in these communities 
was generally less than in communities that have not adopted higher 
standards. 

The MAT also observed a large number of buildings in all flood haz
ard 
zones (VE, AE, B, C, X) that were constructed (voluntarily) to 
higher than required elevations with pile foundations. These struc
tures 
generally sustained far less flood damage than nearby structures 
constructed to the minimum NFIP requirements. This was especially 
true in Zone AE, where buildings were constructed several feet above 
the BFE on pilings, thus reinforcing the benefits of using V-Zone de
sign 
and construction techniques in the coastal A Zone.2 

2.1.3 Relating Observed Flood Damages to the FIRMs 

FEMAs methodologies for mapping 
have evolved over the years due to im
provements 
in our understanding of 
coastal processes and the develop
ment 
of new technologies. Over a 
30-year period, there have been at least 
four generations of FIRMs in the area 
affected by Hurricane Ivan. As method
ologies 
have evolved, BFEs have gone 
up or down, and Zones VE, Zones AE, and Zones X have expanded 
or contracted. The differences in damages between adjacent build
ings 
are due to differences in how the buildings were constructed (i.e., 
building elevations), and some of this can be explained by the flood 
hazard zone and BFE that were in effect at the time the buildings were 
constructed. 

The MAT determined that the area flooded by Ivan exceeded the 
SFHA shown on the effective FIRMs for many communities, from Gulf 
Shores, Alabama, to Okaloosa County, Florida, which is reflected in 
Table 1-2 and based on the current FIRMs and the High Water Marks 

FEMA recently announced an update of the coastal 
flood hazard mapping guidelines. The guidelines 
will promote more accurate flood studies by 
incorporating consistent methodologies and 
improved technological processes. Guidelines 
are being developed first for the Pacific Coast, 
with the Atlantic and Gulf Coasts to follow. 

2 As a working definition, consider the coastal A Zone to be that area near the shoreline with exposure to breaking wave 
heights between 1.5 and 3.0 feet. Another way to identify the coastal A Zone is to identify areas near the shoreline 
and exposed to waves, where base flood stillwater depths are between approximately 2 feet and 4 feet, or where the 
ground lies between 3 feet and 6 feet below the BFE. 



(HWMs) as shown in Figures 1-7 through 1-17. The coastal FIRM 
changes over the years likely resulted in variations in lowest floor el
evations 
and construction practices since most buildings tend to be 
constructed to the minimum regulatory requirements. 

During its investigations, the MAT researched the flood hazard map
ping 
for two locations in Baldwin County, Alabama; three locations 
in Escambia County, Florida; and one location in Santa Rosa County, 
Florida. The results of some of this research (for one location in Bald
win 
County and the location in Santa Rosa County) are provided in 
Sec. 2.1.3.1 and 2.1.3.2, respectively. 

2.1.3.1 Baldwin County, Alabama 

The effective FIRM and FIS for Baldwin County are in countywide for
mat 
and are dated June 17, 2002. Table 2-1 shows the 2002 Baldwin 
County 100-year stillwater elevations and BFEs along the Gulf of Mex
ico 
shoreline near Orange Beach and Gulf Shores. 

The MAT conducted a series of comparisons to assess flood map 
changes that occurred with the various map revisions (see Figure 2-3 
for a typical comparison). These changes are significant because they 
would have influenced building construction while the maps were 
in place. Three sets of maps were compared: the Baldwin County 
Flood Hazard Boundary Map (FHBM) from October 1983 (based on 
the NOAA tide gauge frequency study); the January 1985 FIRM that 
was based on the TTSURGE joint probability analyses; and the latest 
FIRM, dated June 2002. 

Table 2-1. Baldwin County Stillwater Elevations and BFEs (2002)
Flooding Source 

FIS Stillwater 
Elevations (feet*) 

BFEs (feet*) 

Gulf of Mexico 

9.3  10 

10 - 15** 





* Elevations are referenced to NAVD 1988 

** Includes wave setup of 2.2 feet 



During the 2002 revision, wave setup of 2.2 feet was added along the 
open coast barrier islands, and the primary frontal dune was included 
as a V-Zone mapping criterion. Differences between the 2002 and the 
previous (1985) FIRM include: 1) BFEs on the barrier islands generally 
increased 2 to 3 feet and 2) the V-Zone width increased approximately 
200 to 250 feet. The 2002 revisions outside the barrier islands were pri
marily 
to reflect updated topographic information (the BFEs did not 
change significantly in these areas). 

One of the areas the MAT researched in Baldwin County is located at 
the west end of Orange Beach at the State Park boundary (see red dot 
in Figure 2-3). This area is located on FIRM panel 01003C0819 K of 
the current maps. The flood zone boundaries were measured from the 
centerline of Perdido Beach Boulevard on the 1983, 1985, and 2002 
FIRMs at this location. Figure 2-4 illustrates the flood zone changes 
here, plus the decreasing and then increasing BFEs over time. 


Figure 2-3. Baldwin County location near the State Park/Orange Beach boundary (see red dot) where the 
historical FIRMs (1983, 1985, 2002) were reviewed. 



Figures 2-5, 2-6, and 2-7 illustrate the nature of flood and erosion dam
age 
at this location during Ivan. While the ages of the destroyed and 
surviving buildings are not known, most were likely built after Hur
ricane 
Frederic in 1979. A review of the damage and the FIRMs also 
indicates the following: 

 Houses built to the 1985 BFEs and foundation requirements were 
generally at a disadvantage compared to those houses built to the 
1983 and 2002 requirements. 

 The surviving houses in Figure 2-5 were all built on pilings, even 
though it appears NFIP regulations did not require construction 
on pilings at those locations (the houses are within approximately 
250 feet from the road, where all the FIRMs show Zone A). 

 The surviving houses were all near the rear and middle of the beach 
where wave effects would have been reduced somewhat. None of 
the houses on the front row in this area survived. 


Figure 2-4. 
Comparison of FIRMs 
over time, at the State 
Park boundary, west end 
of Orange Beach (Orange 
Beach, Baldwin County, 
Alabama) 



 The surviving houses in Figure 2-5 were likely built with the lowest 
floor above the BFEs shown on the FIRMs. The CHWM figures in 
Chapter 1 show Ivan stillwater elevations of approximately 12 to 14 
feet NAVD in the area, and wave heights could have been several 
feet higher yet (the highest BFE within 600 feet of the road was 14 
feet NAVD between 1983 and 1985). 


Figure 2-5. 
Ivan damage at the 
west boundary of 
Orange Beach. Houses 
are missing from piles 
and piles are broken 
near the ground level. 
(See Figures 2-6 and 
2-7 for ground photos.) 
(Orange Beach/State Park 
boundary) 

Figure 2-6. 
Ground photo of the same 
area as Figure 2-5. At 
this location, all houses 
seaward of the blue house 
(circled) were destroyed 
by Ivan. Some houses 
(arrow designates the 
left house in Figure 2-5) 
washed landward largely 
intact. Other houses were 
completely destroyed. 
The likely cause was 
pile breakage due to 
inadequate pile size and/ 
or insufficient elevation 
of the houses, combined 
with large lateral (flood 
and wind) loads acting on 
the houses. 



MAT examination of larger buildings in Orange Beach (see section 
3.1.2) confirmed these general findings: elevation above the BFE on 
an adequate pile foundation was the key to buildings successfully re
sisting 
flood forces during Ivan. 

2.1.3.2 Santa Rosa County, Florida 

The effective FIRM and FIS for the unincorporated areas of Santa 
Rosa County, Florida, are dated July 17, 2002. The most recent coastal 
revision was first reflected on the January 19, 2000, FIS and FIRM. For 
this revision, updated coastal flooding analyses were prepared for the 
open coast shorelines of the Gulf of Mexico, Santa Rosa Sound, and 
Pensacola Bay up to U.S. Route 90. The revision incorporated primary 
frontal dune analysis, updated wave action, and provided a new shore
line 
and the effects of coastal erosion. Wave setup of 2.5 feet was added 
to the open coast stillwater elevation. The July 17, 2002, FIS and FIRM 
were produced to reflect changes in community boundaries; there was 
no revised flooding analysis provided as part of this revision. 

Table 2-2 presents stillwater elevations from the Santa Rosa County FIS 
dated July 17, 2002. 


Figure 2-7. 
Building on the right 
side of Figure 2-5 
survived, although it 
sustained destruction of 
the lower enclosed area 
and suffered extensive 
internal damage due 
to wind (soffit loss, 
window breakage, rainfall 
penetration). 



The MAT conducted a detailed comparison to assess flood hazard zone 
changes over time in Santa Rosa County, Florida, along Bay Street in 
the Oriole Beach area (see Figure 2-8). The zero station for this com
parison 
was taken at the centerline of the intersection of Bay Street 
and Harrison Avenue. The MAT used two sets of maps: the Santa Rosa 
County FIRM dated November 1985 and the FIRM dated January 2000, 
the latter of which reflects the same flood hazards shown on the cur
rent 
effective FIS dated July 17, 2002. Figure 2-9 shows how the flood 
zones and BFEs changed between the 1985 and 2000 FIRMs. The major 
changes are an increase in BFEs seaward of Bay Street of up to 3 feet 
and an inland expansion of the SFHA of approximately 1,500 feet (with 
BFEs of 8 and 9 feet in the newly mapped inland areas). 

Table 2-2. Santa Rosa County Stillwater Elevations
Flooding Source 

FIS Stillwater 
Elevations (feet*) 

BFEs (feet*) 

Gulf of Mexico 

10.5** 

11-16 

Pensacola Bay 

4.9  5.7 

5-8 

Santa Rosa Sound 

8.0 

8-12 





* Elevations are referenced to NGVD 1929. 

** Includes wave setup of 2.5 feet. 


Figure 2-8. 
Santa Rosa County 
locations where historical 
FIRMS were reviewed. 
The easternmost dot (just 
northwest of Bay Street 
and Harrison Avenue) 
shows the reviewed 
Santa Rosa County 
location, and the other 
dots reflect building 
locations discussed later 
in this section. 



Figure 2-10 shows some of the houses in the newly mapped area. These 
buildings are on ground estimated at +/- 7 feet NGVD, approximately 
700 feet north of Bay Street (1,000 feet from Santa Rosa Sound) and 
within 1,000 feet of Harrison Avenue. The FIRMs in Figure 2-9 show 
the changes that have occurred in the vicinity. The houses were con
structed 
in flood hazard Zone B, outside the SFHA shown on the 1985 
FIRMs, but had 2 to 4 feet of water inside as a result of Hurricane Ivan. 
Some property owners said their lenders had not notified them when 
the flood maps changed, and they had not purchased flood insurance. 

Many houses constructed along the west end of Bay Street (approxi
mately 
1 mile west of Harrison Avenue) were older, pre-FIRM houses, 
and were likely built on land with grade elevations of 5 to 6 feet NGVD. 
These houses were later mapped by the 1985 FIRM as Zone B or Zone 
AE with a BFE of 7 feet NGVD and by the 2000 FIRM as Zone AE with 
a BFE of 9 feet NGVD. Figure 2-11 shows a typical house along the west 
end of Bay Street that was damaged heavily during Ivan. The house 

Figure 2-9. 
Santa Rosa County: 
Comparison of FIRMs 
at the centerline of the 
intersection of Bay Street 
and Harrison Avenue 



V-Zone conditions during Ivan. 
was most likely in Zone B at the time of construction (but is currently 
mapped as Zone AE elevation 9 feet NGVD). The figure shows signifi
cant 
damage due to storm surge and wave and floating debris impacts, 
which are typical of V-Zone conditions. The HWM (stillwater) in this 
area was approximately 11 feet, as shown on Figure 1-12. Based on 
FEMAs current flood hazard mapping methodology, the 11-foot still
water 
elevation and a ground elevation of approximately 6 feet would 
yield a wave crest elevation of approximately 13 to 14 feet NGVD dur
ing 
Ivan. The house shown in Figure 2-11 undoubtedly experienced 

Figure 2-10. 
Typical houses at 
Birdseye Circle, which 
had 2 to 4 feet of flooding 
inside the houses. This 
area was mapped as 
being outside the SFHA 
on the 1985 FIRM, which 
likely governed the 
construction standards 
that were followed when 
the house was built. 


Figure 2-11. 
Typical damage to houses 
along Bay Street that were 
impacted by surge and 
wave effects from Santa 
Rosa Sound. This house 
on the west end and south 
side of Bay Street was 
constructed with a slabon-
grade foundation. The 
house was either pre-FIRM 
or constructed in Zone B 
(1985 FIRM) and is currently 
mapped as Zone AE with 
a BFE of 9 feet. The house 
undoubtedly experienced 
V-Zone conditions. (Santa 
Rosa County) 



Figure 2-12 is an aerial photograph showing houses along Bay Street 
(above the canal) that were impacted by storm surge, waves, and 
floodborne debris. These houses were likely constructed in Zone B, 
according to the 1985 FIRM; however, many were likely built prior to 
the 1985 FIRM. Although the surge and wave impacts from Hurricane 
Ivan in the area produced V-Zone conditions, the current FIRM shows 
these houses in Zone AE with a BFE of 9 feet. 

Figure 2-12 also shows houses constructed along Santa Rosa Sound 
that experienced different levels of damages based on the elevations 
of their lowest floors. The white house on the bottom right was con
structed 
above the BFE on a pile foundation and higher than other 
nearby houses, which were constructed on a slab or stem wall founda
tion. 
The lower houses were severely damaged by storm surge, waves, 
and debris impacts. The white house and other nearby pile-supported 
houses along this shoreline appear to have been constructed several 
feet above the BFE, which prevented significant flood damages; based 
on elevation certificates, two of the pile-supported houses in this area 
were constructed to an elevation of 15 feet, over 5 feet above the mini
mum 
elevation requirement. 

Figure 2-12. 
Aerial view of houses 
along Bay Street (above 
the canal) and Santa 
Rosa Sound that were 
heavily damaged by storm 
surge and wave impacts. 
The circled house is the 
same house shown in 
Figure 2-11. The house 
on the lower left is the 
same house shown in 
the background of Figure 
2-13. Houses elevated 
above the BFE on pilings 
(see arrow) sustained 
far less flood damage 
than houses at lower 
elevations. 



Figures 2-14 and 2-15 show a house on Santa Rosa Sound that was heavily 
damaged by waves and floodborne debris. The house was likely con
structed 
when the area was mapped as Zone B, but the effective FIRM 
shows the house in Zone AE with a 10-foot BFE. Like the other nearby 
houses, this house undoubtedly experienced V-Zone conditions during 
Ivan. Had this house been elevated on a substantial pile foundation, as 
was the house west of the canal entrance (see arrow) or the white house 
in Figure 2-12, the flood damage would probably have been minimal. 


Figure 2-13. 
The house in the 
foreground was 
constructed on piles 
and had minimal flood 
damage during Ivan, 
although it lost a pile 
support for the deck. 
The house in the 
background (see arrow) 
was constructed at much 
lower level and sustained 
significant flood damage 
throughout the first floor. 
The damaged house is 
also shown on the left 
side of Figure 2-12. 


Figure 2-14. 
The house on the right 
(circled), which is at the 
west end of Del Mar Drive, 
south of Bay Street, along 
the Santa Rosa Sound, 
was heavily damaged by 
storm surge and wave 
and debris impacts. The 
same house is shown in 
Figure 2-15. The effective 
FIRM shows the house 
in a Zone AE with a BFE 
of 10 feet. Note minimal 
flood damage occurred to 
the newer, pile-elevated 
house west of the canal 
entrance (arrow). 



These examples point out several important points: 

 The changes in flood hazard zones and BFEs over time likely 
contributed to the reduction of flood damage experienced by 
newer houses, but given a storm like Ivan with flood levels above 
the BFE, the new maps alone could not ensure building survival. 

 Elevating newer houses on pilings several feet above the BFE was also 
central to the success of these buildings. Elevating the lowest floor 
above the BFE (freeboard) contributed greatly to the reduction in 
flood damage, especially in areas shown as Zone AE on the effective 
FIRM that experienced V-Zone conditions during Ivan. 

Figure 2-15. 
This house, located on 
Santa Rosa Sound and 
circled in Figure 2-14, 
was severely damaged 
by surge, wave, and 
debris impacts. The large 
timber that washed into 
the house reportedly 
originated across the 
Sound in Pensacola 
Beach 



2.2 Building Codes and Standards 

Alabama adopts building codes on a statewide basis only for 
state-owned buildings, such as schools. Local jurisdictions de
termine 
the adoption of building codes for private buildings. 
All Alabama jurisdictions have traditionally adopted editions of the 
Standard Building Code (SBC) published by the Southern Building 
Code Congress International. The City and County of Mobile had ad
opted 
the 2000 International Building Code (IBC) on May 15, 2001 
(City of Mobile) and in 2000 (County of Mobile).3 The City of Or
ange 
Beach adopted the 2003 IBC in the summer of 2004. The City 
of Gulf Shores adopted the 2003 IBC as an emergency measure after 
Hurricane Ivan to improve the quality of the reconstruction. Most 
other affected Alabama communities such as those in unincorporat
ed 
Baldwin County were still enforcing the 1997 or 1999 SBC at the 
time of Hurricane Ivan. 

In the Florida Panhandle, the SBC  with local amendments  was 
used to regulate construction until early 2002. By March 2002, the 
FBC 2001 Edition had been adopted statewide. The FBC, adminis
tered 
by the Florida Building Commission, governs the design and 
construction of residential and non-residential (commercial, industri
al, 
critical/essential, etc.) buildings in Florida. In December 2004, the 
Florida Building Commission completed the 2004 Edition of the FBC. 
The 2004 Edition replaces the 2001 Edition and will be adopted state
wide 
by administrative rule in the fall of 2005. 

2.2.1 Flood Requirements in Building Codes and Standards 
 Alabama 

Flood-resistant construction requirements in coastal Alabama are 
located in the building codes (IBC, IRC), which themselves refer
ence 
community floodplain management ordinances and consensus 
standards with flood requirements (i.e., Minimum Design Loads for 
Buildings and Other Structures published by the American Society of 
Civil Engineers 7 (ASCE 7) and Flood-Resistant Design and Construc
tion 
(ASCE 24)). One additional program affects coastal construction 
in Alabama: the CCCL, which acts as a seaward limit for construction. 
Details for each are provided below. 

3 The International Code Council (ICC) was formed to bring together the three model code groups and their respective 
codes  ICBO (Uniform Building Code), BOCA (National Building Code), and SBCCI (Standard Building Code) - under a 
unifying code body in support of common code development. In 2000, the ICC developed a family of codes, including 
the International Building Code (IBC) and the International Residential Code for One- and Two-Family Dwellings (IRC). 



2.2.1.1 Flood Provisions in the IBC (2003) 

The IBC is applied to multi-family buildings (with a few exceptions, 
which are governed by the IRC), and to non-residential buildings. 
Most of the mandatory flood provisions are contained in Section 1612 
(Flood Loads), but others also occur in the Code related to lowest floor 
elevation inspection, flood resistance materials, accessibility, ventila
tion, 
and elevators. 

2.2.1.2 Flood Provisions in the IRC (2003) 

The IRC applies to one- and two-family dwellings and to some town
houses. 
Most of the mandatory flood provisions are contained in 
Section R323 (Flood-Resistant Construction), but others also occur in the 
Code related to utilities, design, and floodplain construction. 

2.2.1.3 Flood Requirements in ASCE 7 

Design loads used by the IBC (2003) are taken from ASCE 7 (2002). 
The following sections of ASCE 7 deal with flood: 

 Section 2.3 (Load Combinations, including different load 
combinations for V Zones and coastal A Zones) 

 Section 5.3 (Flood Loads, which covers hydrostatic, hydrodynamic, 
and wave and impact loads; and which specifies load criteria for 
breakaway walls) 

Flood design loads, per se, are not specified by the IRC (2003) since 
it is a prescriptive code. The IRC refers the designer to the local juris
diction 
for flood requirements. The IRC makes use of environmental 
hazard maps (wind, seismic, snow, etc.), which are largely consistent 
with ASCE 7 hazard maps. 

2.2.1.4 Flood Requirements in ASCE 24 

ASCE 24 is a standard devoted entirely to flood-resistant design and 
construction. It is referenced by Section 1612 of the IBC (2003), which 
states: The design and construction of buildings and structures in 
flood hazard areas, including areas subject to high velocity wave ac
tion, 
shall be in accordance with ASCE 24. 

The IRC does not reference ASCE 24; thus, communities would have to 
reference ASCE 24 directly for its provisions to apply to small residen
tial 
buildings. However, Section R323 of the IRC states that buildings 
in floodways shall be designed in accordance with the IBC, thereby 
mandating use of ASCE 24 for buildings in floodways. 



The 1998 edition of ASCE 24 was the first edition produced and, 
by default, was the edition referenced by the 2003 IBC. However, 
a new edition of ASCE 24 (2005 edition) is forthcoming, and the 
2005 edition has some significant changes to the earlier edition. 
The 2005 edition of ASCE 24 will be referenced by the 2006 edition 
of the IBC. 

2.2.1.5 Coastal Construction Control Line (Alabama) 

In addition to the NFIP and building code requirements, buildings 
constructed along the Gulf shoreline may also be subject to CCCL 
regulations (Alabama Administrative Code, Division 335-8) admin
istered 
by the Alabama Department of Environmental Management 
(ADEM), Coastal Area Management Program, except in the City of 
Gulf Shores, which administers the CCCL within its jurisdiction. The 
CCCL was established in the mid-1980s and has not been revised 
since that time. 

In Alabama, the CCCL is a line of prohibition, seaward of which no 
construction (including substantial improvement of an existing struc
ture) 
or excavation is allowed. Any proposed building on a parcel 
intersected by the CCCL must obtain a permit from ADEM (or ap
proval 
from Gulf Shores). CCCL variances may be obtained in some 
instances where the property owner can demonstrate that enforcement 
of the CCCL provisions would constitute a taking. CCCL coordinates 
and maps are available from ADEM and Gulf Shores. 

When construction on a parcel intersected by the CCCL involves com
mercial 
or multi-family structures (e.g., a hotel, motel, or condominium), 
the permitting is more involved than for a single-family or duplex-type 
structure. Commercial and multi-family CCCL permits require an Envi
ronmental 
Impact and Natural Hazards Study that includes: 

 A wave study that addresses the flood hazard and erosion 
potential using eroded beach profiles for pre- and post-developed 
conditions, 

 Location and delineation of velocity zones, and 

 Analysis of the projects potential to significantly increase the 
likelihood that damage will occur from floods, hurricanes, or 
storms. 

Commercial and multi-family CCCL permits also require a Beach and 
Dune Enhancement Plan that includes provisions for dune walkovers, 
sand fencing, and vegetation and dune maintenance. 



Bulkheads, retaining walls, or similar structures are not permitted on 
parcels intersected by the CCCL unless it can be demonstrated that: 
1) the bulkhead or retaining wall is landward of the CCCL and it is 
necessary to protect and ensure the structural integrity of an existing 
or previously permitted structure, and 2) there are no other feasible 
non-structural alternatives. 

2.2.2 Flood Requirements in Building Codes and Standards 
 Florida 

Flood-resistant construction requirements in coastal Florida are locat
ed 
primarily in community floodplain management ordinances and in 
Chapter 31 of the FBC (for buildings seaward of the Florida CCCL). 

2.2.2.1 Flood Provisions in the FBC (2004 Edition) 

Major flood provisions contained in the 2004 Edition of the FBC ad
dress 
siting requirements for nursing homes, hospitals, educational 
facilities, and shelters as well as general flood-resistant design require
ments. 
Section 1605.2.2 of the FBC states that flood loads shall be 
determined by the provisions of ASCE 7. There is no reference in the 
FBC to ASCE 24. 

The Florida Building Code  Residential Volume (2004) is a new 
document that is also under development at this time. Like the FBC, 
Section R301.2.4 of the residential volume defers most matters related 
to flood-resistant construction to the community floodplain manage
ment 
ordinance. 

2.2.2.2 Coastal Construction Control Line (Florida) 

The CCCL is established by the Florida Department of Environmental 
Protection (FDEP) and describes the landward boundary of that por
tion 
of the beach-dune system which is subject to severe fluctuations 
based on a 100-year storm surge, storm waves, or other predictable 
weather event (Florida Statutes, Ch. 161). As a practical matter, the 
state defines the CCCL position as being one of the following: 

 the landward limit of storm-induced erosion (where upland 
elevations are substantially greater than the 100-year still water 
level) 

 the landward limit of a 3.0 foot wave propagating at the 100- 
year stillwater level (where upland elevations are low and profile 
inundation occurs) 



 at the landward limit of overwash (in instances where the profile 
is not inundated but where wave overtopping and sediment 
deposition occur), or 

 at the landward toe of the coastal barrier dune structure impacted 
by, but not destroyed by, erosion accompanying the 100-year 
stillwater level and storm waves. 

The Florida CCCL is generally situated farther landward than the Ala
bama 
CCCL, and unlike the Alabama CCCL, the Florida CCCL is a 
line of jurisdiction (not prohibition), seaward of which a permit is 
required from the FDEP and seaward of which special provisions of 
Section 3109 of the FBC apply. The CCCL permit from FDEP addresses 
building siting and beach/dune protection issues, while Section 3109 
of the FBC addresses building design and construction requirements. 
The Florida CCCL has been re-established and moved over the years, 
unlike the Alabama CCCL. 

Building requirements seaward of the Florida CCCL are in many ways 
similar to NFIP V-Zone requirements: elevation above the 100-year 
wave crest on a pile foundation; design for simultaneous flood and 
wind loads, including the effects of storm-induced erosion; aside from 
the foundation, construction below the lowest floor must be frangi
ble 
(i.e., breakaway); etc. However, the State has established its own 
100-year wave crest elevations, which, in most cases, are higher than 
FEMAs BFEs along beachfront areas. 

A comparison of NFIP flood hazard zones and the CCCL in Florida 
shows that the CCCL lies landward of the V-Zone boundary in some 
locations and seaward in others. In areas where the CCCL is seaward of 
the V-Zone boundary, the higher of the BFE and the states wave crest 
elevation will govern (subject to local freeboard requirements). 

In the areas where the CCCL is more landward than the V-Zone bound
ary, 
CCCL provisions will generally control design and construction 
in any A Zones seaward of the CCCL (again, subject to higher stan
dards 
imposed by a community). There may be some inconsistencies, 
however, about which designers should consult building officials and 
floodplain managers (concerning, for example, whether flood open
ings 
are required in CCCL-mandated breakaway walls in mapped A 
Zones seaward of the CCCL). 



2.2.3 Wind Requirements in Building Codes and Standards 
 Alabama 

In Alabama, the 1997 and the 1999 SBC was the code in effect for most 
impacted counties. The exceptions are the City and County of Mobile; 
they adopted the 2000 IBC/IRC on May 15, 2001 (City of Mobile) and 
in 2000 (County of Mobile). 

2.2.3.1 Comparing Design Wind Speeds 

Current codes and standards (the FBC, the IBC, and ASCE 7) stan
dardize 
the wind speed measure as the 3-second peak gust. This differs 
from the fastest-mile wind speed measure that was previously used by 
the SBC and ASCE 7 and the wind speed measure of 1-minute sus
tained 
that is used in the Saffir-Simpson Hurricane Scale presented in 
Chapter 1. 

The IBC specifies higher wind speeds for coastal Alabama than any 
of the previous editions of the SBC. Baldwin County, Alabama, is ap
proximately 
75 miles long in the north-south direction perpendicular 
to the Gulf of Mexico coast line. Mobile County is similar at 65 miles 
long. Therefore, there is great variation in the design wind speeds 
from the coastal, southern end of the counties to the inland, north
ern 
end. At the time of Hurricane Frederic in 1979, the SBC design 
wind speeds were fastest-mile speeds varying from 110 mph at the 
coast to 90 mph inland, the equivalent of 3-second peak gust speeds 
are 130 mph at the coast to 105 mph inland. The 1985 SBC modified 
the required speeds to match those in American National Standards 
Institute (ANSI) A58.1 -1982, the predecessor to the ASCE Minimum 
Load Standard for Buildings and Other Structures (ASCE 7). For Bald
win 
and Mobile Counties, that range of speeds was 85 to 100 mph 
fastest-mile, or 100 to 120 mph measured as a 3-second peak gust. 
The wind speed map remained unchanged for all the subsequent 
editions of SBC, including the last edition in 1999. The maps used 
by the 2003 IBC are taken directly from ASCE 7-02. The 3-second 
peak gust wind speeds for Baldwin and Mobile Counties are 115 mph 
(north end) to 150 mph (at the coast) as shown in Figure 2-16. Table 
2-3 contains a summary of the design wind speeds for the counties in 
Alabama visited by the MAT. Table 2-4 (in the next section) presents 
a summary of the design wind pressure on wall and roof areas for a 
typical residence in Gulf Shores. Exposure B is assumed for the IBC 
calculations. In instances where Exposure C design coefficients are 
applicable, the tabulated pressures would be approximately 30 per
cent 
higher than these values. SBC loads were based on Exposure B, 
but no differentiation was made for more open sites. 



Table 2-3. Basic Design 3-Second Gust Wind Speeds (For Baldwin and Mobile Counties, Alabama)
County 

Standard Building 
Code 1979 Edition* 

Standard Building 
Code 1997 Edition* 

International Building 
Code 2003 Edition and 
ASCE 7-98 and later 

Baldwin 

105-130 mph 

100-115 mph 

114-150 mph 

Mobile 

105-130 mph 

100-115 mph 

117-150 mph 





* Code wind speeds reported as fastest-mile wind speeds in the SBC were converted to 3-second gust for 
comparison. 

Where a range is given, the lower values correspond to the edge of the 
county farthest from the coast, and the higher values correspond to 
the coastal value or the edge of the county closest to the coast. 

Figure 2-16. 
Design Wind Speeds from 
IBC 2003 and ASCE 7-98 
and 02 



2.2.3.2 Comparing Design Wind Pressures 

The methodology required for calculating wind loads in the 2003 IBC 
is that prescribed in Chapter 6 of ASCE 7-02. Using ASCE 7 for de
termination 
of wind loads ensures designers are using state-of-the-art 
methodology in wind-load analysis to calculate wind loads. The ASCE 
7-02 provisions provide the same loads as ASCE 7-98 for the cases dis
cussed 
previously. In addition to the improved load computations 
provided by ASCE 7, the IBC also has requirements for windborne 
debris protection of glazing, and improved component and cladding 
requirements, particularly for roof coverings and accessories. It is 
evident that the design wind pressures have been increasing for com
ponents 
and cladding with each new code development over the last 
25 years. This increase was due to observed failures and damage to 
buildings (similar to MAT observations in Gulf Shores and Orange 
Beach) at these exterior building systems when subjected to a design 
level wind event such as Hurricane Ivan. 

For example, the required pressure for corner zones of roofs has in
creased 
more than 3 fold over that period. Corner zones did not even 
exist in the 1979 SBC. The 1979 SBC did not prescribe higher loads 
at roof perimeters or corners, or at wall corners. These increases are a 
reflection of the findings of both wind tunnel research full-scale mea
surements 
and post-storm investigations. The pressures have increased 
most dramatically on the parts of buildings that consistently experi
enced 
wind-induced damage. In addition, wind speeds in this region 
of the Gulf Coast increased as a result of new modeling of the hurri
cane 
threat. 



Table 2-4. Typical Single-Family Residence in Gulf Shores, Alabama 
Description 

Standard 
Building Code 
1979 Edition 

Standard 
Building Code 
1997 Edition 

International 
Building Code 
2003 Edition 
 Also ASCE 
7-98 and later 

Maximum 
Recorded 
Wind Speed 
for Hurricane 
Ivan using 
IBC Factors 

Basic Wind Design Speed 

110 mph 

97 mph 

145 mph 

Equivalent Wind Speed 
(3-second gust) 

130 mph 

115 mph 

145 mph 

124 mph 

Wind Design Pressures 
on Exterior Walls 

(psf) 

(psf) 

(psf) 

(psf) 

As Main Frame 

Edge 

Middle 

Net Edge 

Net Middle 

20/-18 

20/-18 

33 

33 

21/-18 

15/-13 

32 

21 

32/-28 

23/-20 

46 

31 

24/-21 

17/-15 

34 

23 

As C & C 

Middle 

Corner 

27/-27 

27/-27 

25/-25 

25/-29 

38/-42 

38/-51 

28/-31 

28/-38 

Wind Design Pressures 
on Roof (4 in 12 slope) 

(psf) 

(psf) 

(psf) 

(psf) 

As Main Frame 

 Windward Edge 

 Leeward Edge 

 Windward Middle 

 Leeward Middle 

-25 

-19 

-25 

-19 

-26 

-19 

-19 

-14 

-40 

-28 

-28 

-22 

-30 

-21 

-21 

-16 

As C & C 

Middle 

Corner 

-23 

-23 

15/-23 

15/-52 

22/-35 

22/-73 

16/-26 

16/-54 





1 The pressure calculations under each code for both main frame and components and cladding were calculated using 
building design coefficients in wind zones that provide the maximum wind pressure for any area on that building surface. 

2 Positive value pressures indicate pressures acting inward toward building surfaces. Negative value pressures indi
cate 
pressures acting outward from building surfaces. 

3. Pressures calculated from the 1979 and 1997 SBC were calculated using their appropriate fastest-mile wind speed 
and design methods in the code that were in effect at the time. The 3-second peak gust wind speed is shown for 
comparative purposes only and was not used in the calculation of the design wind pressures. 

psf = pounds per square foot 

net edge = the net pressure contributing to the shear force for the wall edge strips; equal to the sum of the external 
pressures from edge wall Zones 1E and 4E (see ASCE 7 Figure 6-4; internal pressures cancel). 

Net middle = the net pressure contributing to the shear force for the interior wall zone; equal to the sum of the external 
pressures from wall Zones 1 and 4 (see ASCE Figure 6-4; internal pressures cancel). 



2.2.4 Wind Requirements in Building Codes and Standards 
 Florida 

Both the SBC and the FBC 2001 specify higher wind speeds for ar
eas 
that are closer to the ocean or gulf and lower wind speeds for 
the inland areas. However, the methodology required for calculating 
wind loads in the FBC is that prescribed in Chapter 6 of ASCE 7 (with 
exceptions). The acceptance of ASCE 7-98 as the methodology for cal
culating 
design wind pressures was an important step for the Florida 
Building Commission. Using ASCE 7 for determination of wind loads 
ensures designers use state-of-the-art methodology in wind load analy
sis 
to calculate wind loads. The use of ASCE 7 also provided Florida 
with an opportunity to align with the IBC and IRC (basis for the FBC 
2004 Edition), both of which also incorporate the methodologies of 
ASCE 7 for load determination. However, it is important to note that 
the legislative statutes governing construction in Florida restrict use of 
ASCE 7 to the 1998 Edition and, thus, do not incorporate the updates 
included in the 2002 Edition of ASCE 7. The FBC 2001 Edition also 
instituted improved design requirements for components and clad
ding 
(such as roof coverings) and debris impact criteria that were not 
previously required by the SBC. 

In addition to the FBC, there are legislative statutes in Florida that 
affect design and construction. These statutes are found in Chapters 
553.71 and 2000-141 of the Laws of Florida and are presented here to 
assist in understanding the design and construction process in the 
Florida Panhandle. Discussions regarding the use of these statutes as 
part of the design and construction process are presented in Chap
ters 
7 and 8. 

First, regarding wind loads, the Florida Legislature mandated several 
items. One such mandate relates to the wind load provisions of ASCE 
7-98 as implemented by the IBC: 

(3) For areas of the state not within the high velocity 
hurricane zone, the commission shall adopt, pursuant 
to s. 553.73, Florida Statutes, the wind protection 
requirements of the American Society of Civil Engineers, 
Standard 7, 1998 edition as implemented by the IBC, 
2000 edition, and as modified by the commission in its 
February 15, 2000, adoption of the Florida Building Code 
for rule adoption by reference in Rule 9B-3.047, Florida 
Administrative Code. [Section 109(3), Ch. 2000-141, Laws 
of Florida.] 



Next, the Florida Legislature modified the windborne debris regions 
of ASCE 7-98 as follows: 

(3) For areas of the state not within the high velocity 
hurricane zone, the commission shall adopt, pursuant 
to s. 553.73, Florida Statutes, the wind protection 
requirements of the American Society of Civil Engineers, 
Standard 7, 1998 edition as implemented by the IBC, 
2000 edition, and as modified by the commission in its 
February 15, 2000, adoption of the Florida Building 
Code for rule adoption by reference in Rule 9B-3.047, 
Florida Administrative Code. However, from the eastern 
border of Franklin County to the Florida-Alabama line, 
only land within 1 mile of the coast shall be subject to 
the windborne-debris requirements adopted by the 
commission. The exact location of wind speed lines shall 
be established by local ordinance, using recognized 
physical landmarks such as major roads, canals, rivers, and 
lake shores, wherever possible. Buildings constructed in 
the windborne debris region must be either designed for 
internal pressures that may result inside a building when 
a window or door is broken or a hole is created in its walls 
or roof by large debris, or be designed with protected 
openings. Except in the high velocity hurricane zone, local 
governments may not prohibit the option of designing 
buildings to resist internal pressures. [Section 109(3), Ch. 
2000-141, Laws of Florida] 

Lastly, the Florida Legislature modified the definition of Exposure C 
as follows: 

(10) Exposure category C means, except in the high velocity 
hurricane zone, that area which lies within 1,500 feet 
of the coastal construction control line, or within 1,500 
feet of the mean high tide line, whichever is less. On 
barrier islands, exposure category C shall be applicable 
in the coastal building zone set forth in s. 161.55(5). [Ch. 
553.71(10), F.S.] 

However, it is important to note that the combination of the wind 
load determination process of ASCE 7, the new requirements for 
components and cladding, and the debris impact criteria for glazing 
provided immediate construction successes during Hurricane Ivan. 
Most newer houses and commercial buildings near the coast designed 
and constructed to the design wind requirements in the FBC 2001 Edi
tion 
performed well and sustained only minimal damage during this 



hurricane event. These results are in contrast to the damages observed 
in the older building stock, which often ranged from roof covering and 
cladding damage, to roof structural failures, to partial structural col
lapse 
of the primary load-bearing system. 

Santa Rosa, Escambia, and Okaloosa Counties experienced the heavi
est 
damage during Hurricane Ivan. Many of the existing buildings and 
structures in these counties were built under the 1997 edition of the 
SBC. In these counties, like other areas in the state, the FBC 2001 Edi
tion 
is now the applicable building code; exceptions to debris impact 
requirements should be noted. 

The SBC, FBC, IBC, and ASCE 7 codes and standards in hurricaneprone 
areas differ significantly in four areas: 

1. The wind speed measure and the design wind speed 

2. How and where pressures are calculated on a building 

3. Requirements for debris impact protection 

4. The FBC defines building exposure categories as Exposure B 
except for areas within 1,500 feet of the coast 

These differences, which will affect the performance of buildings, are 
discussed in the following subsections, respectively. 

2.2.4.1 Comparing Design Wind Speeds 

Current codes and standards (the FBC, the IBC, and ASCE 7) standard
ized 
the wind speed measure as the 3-second peak gust. This differs 
from the fastest-mile wind speed measure that was previously used by 
the SBC and ASCE 7 and the wind speed measure of 1-minute sus
tained 
that is used in the Saffir-Simpson Hurricane Scale presented in 
Chapter 1. Figure 2-17 shows the FBC 2001 wind speed and windborne 
debris region map. Table 2-5 presents the design wind speeds (in 3- 
second gusts) for the heavily impacted counties from Hurricane Ivan 
using three different codes. The wind speeds shown in Table 2-5 are 
the nominal design, 3-second peak gust wind speeds at 33 feet above 
ground for Exposure C category (open terrain). The SBC used fastestmile 
wind speeds; the FBC 2001 Edition uses the 3-second peak gust 
wind speed. To facilitate comparison with the FBC, the MAT convert
ed 
fastest-mile wind speeds provided in the older editions of the SBC 
Code into 3-second peak gust wind speeds. 



Figure 2-17. 
Wind speed and 
windborne debris 
region map (Courtesy 
of the Florida Building 
Commission, 2001) 

AT L A N T I C 
O C E A N 
G U L F 
O F 
ME X I C O 
Alachua 
Brevard 
Charlotte 
Citrus 
Collier 
De Soto 
Dixie 
Flagler 
Gilchrist 
Glades 
Hardee 
Hendry 
Hernando 
Highlands 
Hillsborough 
Lake 
Lee 
Levy 
Manatee 
Marion 
Okeechobee 
Pasco 
Pinellas 
Polk 
Putnam 
St. Johns 
Sarasota 
Seminole 
Sumter 
Volusia 
Orange 
Osceola 
Jackson 
Calhoun 
Franklin 
Gadsden 
Gulf 
Leon 
Wakulla 
Bay Baker 
Bradford 
Clay 
Columbia 
Duval 
Escambia 
Hamilton 
Jefferson 
Lafayette 
Madison 
Okaloosa 
Santa 
Rosa 
Suwannee 
Taylor Union 
Walton Washington 
Liberty 
Nassau 
Broward 
Dade 
Holmes 
Indian 
River 
Martin 
Monroe 
Palm Beach 
St. Lucie 
Table 2-5. Basic Design 3-Second Gust Wind Speeds (Ranges for Each County)
County 

Standard Building 
Code 1979 Edition* 

Standard Building 
Code 1997 Edition* 

Florida Building 
Code 2001 Edition 
and ASCE 7-98 and 
later Editions 

Escambia 

105-130 mph 

105-112 mph 

120-140 mph 

Santa Rosa 

105-130 mph 

105-112 mph 

120-140 mph 

Okaloosa 

105-130 mph 

105-112 mph 

116-134 mph 





* Code wind speeds reported as fastest-mile wind speeds in the SBC were converted to 3-second gust for comparison. 



Where a range is given, the lower values correspond to the edge of the 
county farthest from the coast, and the higher values correspond to 
the coastal value or the edge of the county closest to the coast. 

2.2.4.2 Comparing Calculated Wind Pressures 

The wind pressures used for design of buildings in the Florida Pan
handle 
have changed significantly from the design pressures from 25 
years ago. The 2001 FBC uses the wind speed map from ASCE 7-98, as 
shown in Figure 2-16. This map prescribes a design wind speed of be
tween 
130 and 140 mph for the affected coastal areas. By comparison, 
Ivans estimated wind speeds were almost 20 percent below the design 
wind speeds required by the current code. 

From Table 2-6, the buildings in the Pensacola area constructed to 
the older SBC codes experienced a design level or near design level 
event. As such, pressures on the main structural systems were at or 
near design loads. An analysis of the wind pressures resulting from 
the actual speeds shows an even greater disparity between the codeprescribed 
design pressures and the pressures predicted from the 
actual recorded wind speeds for components and cladding systems. 
As seen in Table 2-6, the resulting pressures are 25 percent to 40 per
cent 
below the code pressures. 



Table 2-6. Wind Pressures on a Single-Family Residence in Pensacola, Florida 

Description 

Standard 
Building Code 
1979 Edition 

Standard 
Building Code 
1997 Edition 

International 
Building Code 
2001 Edition 
 Also ASCE 
7-98 (and later 
editions) 

Maximum 
Recorded 
Wind Speed in 
Florida from 
Hurricane 
Ivan using 
IBC Factors 

Basic Wind Design Speed 

105 mph 

95 mph 

135 mph 

Equivalent Wind Speed 
(3-second gust) 

130 mph 

110 mph 

135 mph 

119 mph 

Wind Design Pressures on 
Exterior Walls 

(psf) 

(psf) 

(psf) 

(psf) 

As Main Frame 

 Edge 

 Middle 

 Net Edge 

 Net Middle 

18/-16 

18/-16 

30 

30 

20/-17 

14/-13 

31 

20 

28/-25 

20/-18 

40 

27 

22/-19 

15/-14 

31 

21 

As C & C 

 Middle 

 Corner 

25/-25 

25/-25 

24/-24 

24/-28 

33/-36 

33/-34 

25/-28 

25/-34 

Wind Design Pressures on 
Roof (4 in 12 slope) 

(psf) 

(psf) 

(psf) 

(psf) 

As Main Frame 

 Windward Edge 

 Leeward Edge 

 Windward Middle 

 Leeward Middle 

-23 

-17 

-25 

-17 

-25 

-18 

-18 

-14 

-35 

-25 

-25 

-19 

-27 

-19 

-19 

-14 

 As C & C 

Middle 

Corner 

-21 

-21 

14/-22 

14/-50 

19/-30 

19/-63 

14/-24 

14/-49 



 

1 The pressure calculations under each code for both main frame and components and cladding were calculated us
ing 
building design coefficients in wind zones that provide the maximum wind pressure for any area on that building 
surface. 

2 Positive value pressures indicate pressures acting inward toward building surfaces. Negative value pressures indi
cate 
pressures acting outward from building surfaces. 

3. Pressures calculated from the 1979 and 1997 SBC were calculated using their appropriate fastest-mile wind speed 
and design methods in the code that were in effect at the time. The 3-second peak gust wind speed is shown for 
comparative purposes only and was not used in the calculation of the design wind pressures. 

psf = pounds per square foot 

net edge = the net pressure contributing to the shear force for the wall edge strips; equal to the sum of the external 
pressures from edge wall Zones 1E and 4E (see ASCE 7 Figure 6-4; internal pressures cancel). 

Net middle = the net pressure contributing to the shear force for the interior wall zone; equal to the sum of the external 
pressures from wall Zones 1 and 4 (see ASCE Figure 6-4; internal pressures cancel). 



2.2.4.3 Comparing Debris Impact Requirements 

The FBC instituted statewide debris impact requirements related to 
design wind speeds. Prior to the FBC, the South Florida Building Code 
(with county provisions) identified debris impact requirements affect
ing 
the design of buildings for portions of Florida. However, the SBC, 
which was enforced in the portions of the state not using the South 
Florida Building Code, did not have debris impact requirements, and, 
therefore, buildings constructed prior to the adoption of the 2001 FBC 
were not required to protect openings against windborne debris. For 
new construction, Section 1606.1.5 of the FBC 2001 Edition defines 
the windborne debris impact regions as: 

1. Areas where the basic wind speed is 120 mph (53 meters per second 
[m/s]) or greater, except from the eastern border of Franklin 
County to the Florida-Alabama line where the region includes 
areas only within 1 mile of the coast. 

2. Areas within one mile (1.6 kilometers) of the coastal mean high 
water line where the basic wind speed is 110 mph (49 m/s) or 
greater. 

Figure 2-17, in combination with the definitions above, depicts the 
windborne debris impact regions. Different criteria for requiring 
protection of openings against damage from windborne debris ap
ply 
for new buildings constructed to the 2001 FBC in coastal Florida 
counties affected by Hurricane Ivan. Whereas a building within the 
120-mph wind contour (or higher) triggers compliance with the state
wide 
criteria for protecting openings, in the Florida Panhandle, only 
new buildings constructed within one mile of the coast are required 
to have opening protection. The FBC provides clear guidance on de
sign 
requirements in the windborne debris regions. Buildings in these 
regions are required to protect glazed openings (windows and doors) 
to ensure that the building envelope remains enclosed. To achieve 
the requirement of an enclosed building, shutters, laminated glass, 
or other opening protection systems are required to be installed. Pro
tection 
measures are required to resist large or small debris (missiles) 
depending upon their height on the exterior of a building above grade. 
An exemption is provided for residential construction in the Florida 
statutes allowing unprotected glazing and openings if the building was 
designed and constructed as a partially enclosed building. A building 
designed to resist the effects of internal pressurization accounts for 
higher pressures that occur when wind enters a building or structure. 
This exemption implies that wind and rain may enter the building 
increasing internal wind pressure substantially, yet the structural de
sign 
is sufficient to prevent failure of the main wind-force resisting 



system. This method of high-wind design may result in substantial in
terior 
damage from the wind and rain that enter the building since 
openings are not protected. Additional guidance on the windborne 
debris region and the debris impact requirements is provided in FBC 
Section 1606.1.4. 

Given the potential for extreme wind and water damage to buildings 
and building contents when the envelope is breached (as confirmed 
by 2004 post-hurricane investigations), building codes have begun to 
restrict the use of the partially enclosed design option. The 2004 sup
plement 
to the IBC removes this option; thus, building openings must 
be protected or glazed with impact-resistant glazing. A similar change 
to the IRC has been approved in committee, and the next edition 
(2006) is expected to eliminate the partially enclosed design option 
for buildings governed by the IRC. 

2.2.4.4 High-Wind Elements of the Code 

The FBC 2001 Edition has special and stringent requirements for 
HVHZ areas. Sections 1611-1616 in the FBC define wind and debris re
quirements 
of HVHZs. Only Dade and Broward Counties are included 
in the HVHZ areas. 

The HVHZs affect the design and construction of buildings by requir
ing 
higher design wind speeds for the entire building and by requiring 
the design of specific building components, attachments, and equip
ment 
for the design wind speed. The difference in design pressure is 
often substantial and results in a much stronger main structure and 
higher component design values for buildings. Many other require
ments 
(e.g., mandatory exposure category, allowable stress increase, 
requirements for windborne debris, inspections during construction, 
product approval requirements, etc.) make HVHZ design and construc
tion 
substantially stronger than in other areas of the state. Buildings 
built according to HVHZ requirements have much more capacity to 
withstand hurricanes and provide additional protection of property. 

Observations related to specific examples of damage observed and the 
sections of the HVHZ criteria that would help resist the types of dam
age 
noted by the MAT are presented in Chapter 5. 



C 


C H A P T E R 3 

3-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

3 

General 
Characterization 
of Damage 

Chapter 3 provides a general characterization of the damage that 
resulted from Hurricane Ivan. Section 3.1 discusses flood effects on 
one- and two-family housing and on multi-family housing. Section 3.2 
discusses wind effects on one- and two-family housing, multi-family 
housing, commercial buildings, and critical and essential facilities. Fi
nally, 
Section 3.3 presents several case studies demonstrating lessons 
learned and best practices. 

3.1 Flood Effects 

As discussed in Chapters 1 and 2, Hurricane Ivan brought 
high storm surge and waves causing severe damage to build
ings 
along the Gulf Coast in Baldwin County, Alabama, and 
the western portions of the Florida Panhandle. Damages resulted 
from high flood elevations and impacts from waves and debris. The 
storm surge caused severe coastal erosion that caused failure of shal
low 
foundations. The MAT observed that flood elevations in many 
areas exceeded the 100-year BFEs depicted on the FIRMs by 2 to 4 
feet, which was also confirmed by FEMAs Flood Hazard Recovery 
Maps, which were produced in the aftermath of Hurricane Ivan and 
included surveyed high water marks, as discussed in Chapter 1. Wave 
damage, which was anticipated in V-Zone areas, was also observed in 
mapped A-Zone areas. In many areas, flood levels resulted in V-Zone 
type damages in mapped A Zones. Wave and waterborne debris im
pacts 
caused significant damage to buildings and to enclosures, slabs, 
decks, stairs, utilities, and other ancillary features. See Appendix E for 
a discussion of FEMAs Flood Hazard Recovery Maps. 



C H A P T E R 3 

GENERAL CHARACTERIZATION OF DAMAGE 

3-2 

 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

Since many houses were constructed to the current minimal flood 
standards and in many cases were pre-FIRM construction, Hurricane 
Ivans high storm surge and waves, which exceeded the BFEs, signifi
cantly 
destroyed buildings on the open coast of the barrier islands and 
throughout the back bays and sounds. 

3.1.1 Flood Effects on One- and Two-Family Housing 

Severe flood damages occurred to one- and two-family buildings 
throughout the study area, on the barrier islands, and, more signif
icantly, 
throughout the back bays and sounds. Particularly hard hit 
areas were near the shorelines of Little Lagoon, Big Lagoon, Santa 
Rosa Sound, Pensacola Bay, and Escambia Bay. 

Most one- and two-family buildings on the barrier islands were built 
using V-Zone construction methods with pile foundations. Newer build
ings 
constructed on pile foundations with proper embedment depth 
generally performed well, although many buildings experienced dam
ages 
to lower area enclosures, nonstructural slabs, access stairways, and 
utilities. Older buildings (as well as a few newer buildings) that were 
built on piles with insufficient cross-section or embedment suffered 
destruction or severe damage. 

In areas along the bays and sounds, Ivans flood elevations frequently 
exceeded the BFE by 2 to 4 feet or more, which led to significant in
undation, 
and wave and floodborne debris damage to buildings, even 
those constructed in compliance with community floodplain manage
ment 
requirements. 

Many of the hardest hit areas were mapped as A Zone, but build
ings 
experienced V-Zone conditions, with severe damage occurring 
to buildings elevated to the BFE on slab, pier, and crawlspace foun
dations. 
Buildings constructed outside the SFHA in areas mapped as 
Zones B, C, or X were often subject to A-Zone flood conditions during 
Ivan. As a general rule, wherever wave crest elevations and floodborne 
debris strikes occurred above the lowest floor elevation, the buildings, 
regardless of foundation type, were destroyed or severely damaged. 
The severity of wave and debris damage near bay and sound shorelines 
is one of the most noteworthy characteristics of Hurricane Ivan. 

The buildings that resisted Ivans flood forces most successfully were 
elevated several feet above the BFE on pile foundations. Buildings ele
vated 
on stem wall foundations in Zones A, B, C, and X also performed 
reasonably well, where the top of the foundation was above the limits 



GENERAL CHARACTERIZATION OF DAMAGE 

of wave action and floating debris, and where the footing depth was 
sufficient to resist scour. 

Figures 3-1 through 3-5 illustrate typical flood damages to one- and 
two-family buildings. 

Figure 3-1. 
Buildings constructed 
on deep pile foundations 
performed well; however, 
significant damage 
occurred to lower-level 
enclosed areas and to 
stairways, utilities, and 
non-structural parking 
slabs below the elevated 
portion of the building. 


Figure 3-2. 
Insufficient pile embedment caused 
displacement of houses (Gulf 
Shores, West Beach) 



In many back bay and sound areas, the flood elevations exceeded the 
100-year BFEs and this led to significant damage to buildings, espe
cially 
those that were constructed to lower elevations. Severe damage 
was caused by wave and debris impacts. Most of the buildings on the 
bays and sounds were pre-FIRM buildings built below the current BFE 
or post-FIRM buildings built at BFE. When floodwaters exceeded their 
lowest floor elevations, these buildings were damaged by waves and 
debris impacts. The severity of the damage varied depending on the 
elevation of the lowest floor. 

Many houses that were several rows back from the shoreline (in Zones 
A, B, C, and X) were somewhat protected, but they sustained consider
able 
flood damage due to inundation levels above the lowest floor. In 
many cases, debris from docks and seaward of the rows of houses was 
carried inland by surge and waves, battering other houses and causing 
significant damage. 

Even in areas where buildings were designed and elevated for high 
wave impacts, buildings suffered severe waterborne debris, surge, and 
wave damage when flood levels exceeded FIRM elevations by several 
feet, as shown in Figure 3-4. 


Figure 3-3. 
This building, which was 
less than 2 years old, was 
constructed on piers at 
the current BFE of 9 feet. 
It was severely damaged 
by high storm surge, and 
wave and debris impacts. 
(Big Lagoon) 



Pre- and post-FIRM residential buildings on slab-on-grade, crawlspace, 
or stem wall foundations in Zone AE near the back-bay or sound shore
lines 
experienced substantial damage and/or complete destruction 
when flood elevations significantly exceeded mapped levels. Repre
sentative 
damages are shown in Figures 3-6, 3-7, and 3-8 where houses 
exposed to flood conditions from Little Lagoon and Big Lagoon (the 
water bodies behind Gulf Shores and eastern Perdido Key) experienced 

Figure 3-4. 
Damage to NFIPcompliant 
elevated 
structure in a V Zone 
(north end of Escambia 
Bay-Floridatown) 


Figure 3-5. 
Buildings constructed 
on piles and elevated 
several feet above the 
BFE sustained less flood 
damage than adjacent 
buildings at lower 
elevations. (Big Lagoon) 



severe surge, wave, and debris damage when flood levels exceeded the 
BFE by 2-4 feet. Note that Figure 3-5 shows a pile-elevated building 
near the building shown in Figure 3-8. 


Figure 3-6. Surge, wave, and debris damage (Little Lagoon) 


Figure 3-7. 
Older buildings below the 
current BFE sustained 
severe flood damage 
throughout the back 
bays. (Little Lagoon) 



Severe damage was caused by flood and wave impact to decks, stairs, 
utilities, and enclosed areas beneath elevated buildings, as shown in 
Figure 3-9. Floodborne debris impacts caused severe damage to build
ings 
that were elevated to the BFEs, as shown in Figures 3-10 and 3-11. 


Figure 3-8. 
This new building was 
constructed to the BFE, 
but was wiped off its 
foundation (slab atop 
stem walls) by Ivan. 
The destruction was 
likely due to storm 
surge, wave action, 
and floodborne debris, 
although wind could 
have contributed to the 
breakup of the building 
(note pine tree leaning 
over slab). (Big Lagoon) 

Figure 3-9. 
Utilities, parking slabs, and enclosed areas under 
an elevated building were severely damaged by 
the high flood elevations and wave action. (Gulf 
Shores) 



Figure 3-10. 
Large timbers washed 
from developments on 
Santa Rosa Island, across 
Santa Rosa Sound, and 
into several homes. 
(Santa Rosa Sound 
 Oriole Beach) 


Figure 3-11. 
Significant floodborne 
debris contributed to 
the severe damage of 
at-grade enclosed area 
beneath an elevated 
building. (Big Lagoon) 



3.1.2 Flood Effects on Multi-Family Housing 

The nature and extent of flood damage to multi-family buildings 
varied considerably, depending on: 1) the location, foundation, and 
lowest floor elevation of the building, 2) the local flood conditions 
during Ivan, and 3) the degree of engineering attention received dur
ing 
design. Note that in some areas, building age was a poor predictor 
of building performance; the MAT observed some older multi-family 
buildings that performed well, and some newer multi-family buildings 
that were destroyed by Ivans flood and erosion effects. 

Obviously, building success or failure during Ivan was also dependent 
on how well the flood hazard maps in effect at the time of construction 
represented site conditions at the time of Ivan. Beach and dune ero
sion 
over time undoubtedly contributed to the damage or destruction 
suffered by barrier island multi-family buildings on shallow founda
tions 
in Zones B, C, or X. In addition, the accuracy of BFEs, flood 
hazard zones, and SFHA boundaries contributed to the damage suf
fered 
by multi-family buildings (on both barrier islands and back bays) 
that were constructed to minimum standards only. 

Multi-family buildings that received a high degree of engineering 
attention (fully engineered structures) and had deep foundations 
appeared to withstand Ivans flood and erosion effects, with the ex
ception 
of lowest floor living units that were below Ivans wave crest 
elevation. Fully engineered, multi-family buildings with parking areas 
at ground level and elevated floors built using VE-Zone construction 


Figure 3-12. 
Significant floodborne 
debris contributed to 
the severe damage of 
buildings throughout the 
back bays and sounds in 
areas mapped as Zone 
AE. (Oriole Beach  Santa 
Rosa Sound) 



methods above the BFE generally sustained the least amount of flood 
and erosion damage. 

Many multi-story buildings (e.g., multi-family and commercial) along 
the Gulf shoreline suffered extensive surge, debris, and erosion dam
age 
to their lowest floor levels, pool decks, and bulkheads. The most 
extreme cases were complete building collapse due to undermining of 
shallow foundations (see Figure 3-13). 

Less extreme  but still severe  damage was observed at many multi-sto
ry 
condominium buildings along the Gulf shoreline of Orange Beach 
and Perdido Key. The lowest floors containing living units, lobbies, 
and common areas were often destroyed by storm surge and waves, as 
a result of floor collapse or destruction of exterior walls, or a combina
tion 
of the two (see Figures 3-14 to 3-15). 


Figure 3-13. Collapse of 5-story, multi-family buildings on shallow foundations (Orange Beach) 


Figure 3-14. Pile foundations performed well, but non-structural floor slabs collapsed and low-elevation living 
units were destroyed. (Orange Beach) 



A separate rapid-response study of Orange Beach multi-story structures 
was undertaken to determine the extent and characteristics of lowest 
floor living unit damages (see Appendix F). The study examined 41 
multi-story buildings, not including the collapsed buildings, such as 
those shown in Figure 3-13. Thirty-nine of the 41 buildings had a total 
of 233 living units at the lowest floor level. 

Dates of construction and flood regulations in effect at the times of 
construction (i.e., flood hazard zones and BFEs) were not available at 
the time of the study; thus, compliance with those regulations could 
not be verified. However, although it appears the majority of the build
ings 
were constructed in Zones B, C, or A, they were constructed on 
pile foundations. Lowest floor elevations (top of floor and bottom of 
lowest horizontal supporting members) were measured as part of the 
study, and this information was compared against the FIRMs in effect 
between 1983 and 2004, during which the majority of the construction 
was thought to have taken place. 


Figure 3-15. 
Building supported 
on pile foundation 
(foreground) survived 
while building on 
shallow foundation 
(background) collapsed. 
(Orange Beach) 

The study found that approximately 80 percent of the lowest floor living 
units were destroyed by flood and/or erosion effects, despite the fact 
that most of the buildings were constructed on pile foundations with 
the top of the lowest floor at or above the BFEs that have been in 
effect over the past two decades. The buildings that sustained the 
least structural damage due to waves and erosion were constructed 
to VE-Zone standards with their lowest horizontal structural member 
several feet above the BFE. 



The study also found that the most common damage state was with the 
lowest floor intact and the non-structural walls destroyed (see Figures 
3-16 and 3-17; this occurred in 21 of the 39 buildings, in 101 of the 233 
lowest floor living units). The next most common damage state was 
lowest floor and walls destroyed (this occurred in 15 of the 39 build
ings, 
in 58 of the 233 lowest floor living units). Fully intact conditions 
(no damage to the lowest floor or lowest floor living units) occurred at 
only 6 of the 39 buildings, and 28 of the 233 lowest floor living units. 


Figure 3-16. 
Foundation and structural 
floor slab survived 
but lowest floor nonstructural 
exterior walls 
were destroyed by surge 
and waves (Orange 
Beach) 

Figure 3-17. 
Destruction of lowelevation 
living units 
by surge and waves, 
while second floor units 
survived intact (Orange 
Beach) 



3.2 Wind Effects 

As documented in Chapter 1, the maximum recorded 3-second 
peak gust wind speed in Hurricane Ivan was 117 mph in the 
Perdido Key area. The maximum wind speeds in Gulf Shores 
and Pensacola Beach were recorded to be 109 mph. The wind speeds 
recorded were well below the design wind speeds for this area under 
current building codes, but were just below the design wind speeds 
used for many years under the SBC. Both the IBC and FBC use the wind 
speed map from ASCE 7, as shown in Figure 2-16. This map prescribes a 
design wind speed of between 140 and 150 mph for the affected coastal 
areas. This means that the estimated actual wind speeds were almost 20 
percent below the design wind speeds required by the current codes. 

An analysis of the wind pressures resulting from the actual speeds indi
cates 
a disparity between the current code-prescribed design pressures 
and the pressures predicted from the estimated actual wind speeds. As 
seen in Chapter 2, the resulting pressures are 25 percent to 40 percent 
below the current code-prescribed pressures. However, it was notable 
that the magnitude of the calculated wind pressures based on the es
timated 
wind speed is very similar to the wind pressures and loads 
calculated using the SBC codes that were in effect from 1985 until the 
present for the main structural systems. Comparing the pressures calcu
lated 
for a code event under the SBC codes with the pressures calculated 
based on the estimated wind speed suggests that structural systems such 
as wall and roof framing received design level pressures while compo
nents 
and cladding systems such as roof decking, windows, doors, and 
wall cladding appeared to have been exposed to higher than design 
level pressures. With the code in effect for 20 years, it is reasonable to 
expect that a large percentage of buildings in the impacted area had 
been constructed under that code, and, thus, the damage discussed is 
consistent with the lower (older) design pressures that were exceeded. 

3.2.1 Summary of Damage Types 

Since the wind loads in Hurricane Ivan were significantly below the 
current design level and approximately equal to design levels of the 
past twenty years, one might expect that the buildings in the affected 
area would have minimal wind damage, but that was not the case. The 
damage observed appeared to be disproportionate to the wind speeds. 
The MAT observed the following: 

 Wind damage to wall cladding was widespread throughout all 
building types and sizes. Damage to exterior insulation finish 
systems (EIFS) and vinyl siding was common. 



 Roof coverings of all types were frequently heavily damaged. 

 Rooftop equipment was frequently damaged or completely de
tached 
as a result of the wind. 

 Soffit damage was also observed throughout the entire wind field 
of the storm. 

 Building envelope damage to older buildings was more common 
than to newer buildings; however, there were still many incidences 
of substantial damage even to new buildings. 

Wind-related structural damage was less widespread than the build
ing 
envelope damage, but was not uncommon. The MAT observed 
the following: 

 The most common structural damage was loss of light-framed roof 
structures, primarily in the form of roof sheathing attachment failure, 
and subsequent damage to framing such as trusses or rafters. 

 Another common failure mode was wood framed gable end walls. 

 Many pre-engineered metal buildings experienced heavy damage to 
both the building envelope and to the secondary framing members. 

 Cantilevered gas station canopies failed frequently throughout the 
damage zone. 

Older buildings typically experienced more damage than buildings 
constructed since the adoption of 2001 FBC and 2003 IBC for the fol
lowing 
reasons: 

 Older building codes methods did not always result in resistance 
to high design wind pressures on critical building areas such as 
corner and wall areas (notable points of failure initiation). 

 Even if an older building code was in place, the enforcement of the 
code may have been ineffective. 

 Older buildings may have suffered from degradation of strength 
due to corrosion, termites, dry rot, poor maintenance, or a variety 
of other factors. 

 Construction methods and materials commonly used at the time 
the older buildings were built may now be considered inappropriate 
for a high-wind area. 

Some effects of these observations include the following: 

 Design wind loads that are too low (due to older methods that 
have been revised by current codes), which result in members and 



connections that are too weak for the winds likely to be encountered 
at the site 

 Fasteners for roof sheathing that are too small or are spaced too far 
apart 

 Undersized or missing strapping to anchor the roof structure to 
the walls 

 Lack of a continuous load at the connection between the walls and 
the foundations 

 Structural design that did not account for unprotected windows 
and doors, which, when broken or damaged, lead to structural 
failures due to rapid increases in internal pressure 

 Unprotected openings and glazing, which, when broken or 
damaged, lead to interior damage from wind-driven rain 

 Collapse of large doors, leading to damage resulting from increased 
internal pressure and damage from wind-driven rain 

 Corrosion of ties or fasteners used to attach cladding to the 
structure 

 Corrosion of anchors or connectors that attach the building to the 
foundations or tie structural elements together 

The MAT repeatedly observed cases where buildings constructed with
in 
the past few years survived the storm relatively unscathed, while older 
buildings next door or directly across the street sustained significant 
damage due to rainwater intrusion through damaged roof coverings, 
damaged soffits, and/or broken windows and doors. 

3.2.2 Wind Effects on One- and Two-Family Housing 

Hurricane Ivan affected a large stock of one- and two-family housing. 
In Gulf Shores alone there were over 1,400 homes in the barrier island 
damage zone. The other communities from Gulf Shores to Navarre 
Beach suffered varying degrees of wind-related damage to houses. The 
most widespread type of wind damage to homes was building envelope 
damage. Roof covering damage was the most common type of building 
envelope damage. All types of roof coverings were affected. Structural 
wind damage was mainly in the form of light-framed roof framing fail
ures 
as shown in Figure 3-18. Insufficient attachment of roof sheathing 
panels to the framing beneath was the most common problem. Gable 
end wall failures were frequently observed, as were failed connections 
between the roof and wall members. 



3.2.3 Wind Effects on Multi-Family Housing 

Wind damage to multi-family housing varied considerably with con
struction 
type. Low-rise, wood-framed condominium buildings 
suffered the same types of damage as their one- and two-family coun
terparts, 
as shown in Figures 3-19 and 3-20. Higher story buildings, 
typically built of cast-in-place concrete, suffered no wind damage to 
the primary structural frame. The observed damage was to the build
ing 
envelope and, in some cases, to structural framing members, such 
as roof trusses. The common types of high-rise cladding damage were 
to stucco and EIFS, a popular wall material in the region as shown in 
Figure 3-21, and to all types of roof coverings. 


Figure 3-18. 
Typical wind damage 
showing loss of roof 
sheathing and damage 
to structural roof framing 
(Ono Island) 


Figure 3-19. 
Typical roof sheathing 
and covering loss 
(Pensacola Beach) 



Figure 3-20. 
Typical gable end wall 
failure and loss of roof 
sheathing and wall 
(Perdido Key) 


Figure 3-21. 
Typical high rise cladding failure (Perdido Key) 



3.2.4 Wind Effects on Commercial Buildings 

Although the MAT did not focus on commercial buildings, the Team 
observed several while in the area. The wind damage was consistent 
with the damage observed in multi-family buildings in that it varied 
with construction type. Cladding damage was widespread, particularly 
to EIFS and all types of roof coverings, as seen in Figures 3-21, 3-22, and 
3-23. Many pre-engineered metal buildings suffered significant dam
age 
to the building envelope and to secondary structural members 
such as girts and purlins, as seen in Figure 3-24. Steel joist and metal 
deck roof structures generally fared well. Wood-framed roof structures 
performed much as they did on residential buildings. 


Figure 3-22. 
Commercial building 
roof covering failure 
(Pensacola Beach) 


Figure 3-23. 
Commercial building wall 
cladding and secondary 
structure failure 
(Gulf Shores) 



3.2.5 Wind Effects on Critical/Essential Facilities 

The MAT focused on the damage and loss of function observed at 
many critical and essential facilities such as hospitals, schools, and shel
ters. 
Damage and resulting loss of function was most often the result of 
building envelope damage, as seen in Figures 3-25 and 3-26. Rooftop 
equipment damage was widespread. Little structural wind damage was 
observed. 


Figure 3-24. 
Pre-engineered metal 
building damage
(Orange Beach) 

Figure 3-25. 
Metal wall panel damage 
to middle school 
(Gulf Breeze) 



3.3 Lessons Learned and Best Practices 

Given the hurricane history of the area, several buildings previ
ously 
visited before Ivan were visited again after Ivan. The MAT 
team also observed many other situations where prudent siting 
and construction improved the building performance during Hurri
cane 
Ivan. Several of these buildings are described below. 

Condominium  Gulf Shores, Alabama 

One of the best known examples is a U-shaped condominium in Gulf 
Shores. The original building was elevated on solid walls and was de
stroyed 
by surge and wave effects during Hurricane Frederic in 1979 
(see Figure 3-27, upper photo). The building was reconstructed after 
Frederic on an open foundation (concrete columns atop pile caps and 
deep pilings). Even though the foundation survived Hurricane Ivan 
(Figure 3-27, lower photo), the MAT team observed significant wind 
damage and corrosion. Closer inspection (Figure 3-28) revealed the 
concrete columns elevating the building had been deteriorating for 
some time (i.e., chloride penetration into the concrete, corrosion of 
the reinforcing steel, and spalling of the concrete cover), and prior ef
forts 
to patch the columns were evident. This points out the need for 
constructing near the coast with sound, durable materials and highquality 
workmanship. 


Figure 3-26. 
Roof covering and roof 
deck damage to middle 
school (Pensacola) 



Figure 3-27. 
After this building 
was destroyed by 
Hurricane Frederic in 
1979 (upper photo), it 
was re-constructed on 
concrete columns, pile 
caps, and deep piles. 
The foundation survived 
Hurricane Ivan; however, 
the building experienced 
significant wind damage 
(lower photo). (Gulf 
Shores) 



Condominium Complex  Pensacola Beach, Florida 

Another example of reconstruction using flood-resistant techniques 
is shown in Figures 3-29 through 3-33. In 1995, Hurricane Opal de
stroyed 
one of four low-elevation, masonry and wood-frame buildings 
comprising a condominium complex at Pensacola Beach (Figure 3-29). 
The destroyed building was replaced by an elevated building support
ed 
on concrete pilings above the BFE, in accordance with the local 
governments (Santa Rosa Island Authority) freeboard requirements 
(Figure 3-30). Waves, surge, and wind during Hurricane Ivan severely 
damaged the remaining three original buildings (Figure 3-31 and 3- 
32). The newer pile-supported building performed well from a flood 
perspective (but sustained some wind damage to the roof covering). 
Ground level breakaway walls, decks, and parking slabs were damaged 
under the new building, but the foundation and main structure suc
cessfully 
resisted flood and wave effects (Figure 3-33). The ability of 
the new building to successfully avoid structural damage due to flood 
forces demonstrates the importance of elevation on a deep pile foun
dation 
with breakaway construction below the elevated building. 

Figure 3-28. 
Severe corrosion of 
reinforcing steel and 
spalling of the concrete 
columns supporting the 
post-Frederic building 
shown in Figure 3-27. 
Note evidence of prior 
attempts to repair the 
columns. 



Figure 3-29. 
Hurricane Opal (1995) 
flood damage to one of 
the four original buildings 


Figure 3-30. 
1998 photograph 
showing the post- 
Opal replacement (pile 
supported) building 
(background) and one of 
the three remaining older 
buildings (foreground) 



Figure 3-31. 
Post-Ivan aerial 
photograph showing 
severe flood damage to 
two of the three older 
buildings, with newer, 
pile-supported building 
intact (left side) 


Pile-supported building constructed 
after hurricane Opal 

Figure 3-32. 
Ivan flood and wind 
damage to older building 
(post-Opal building 
visible at far left) 



Condominiums  Perdido Key, Florida 

The MAT observed 4 condominiums in close proximity to each other 
on Perdido Key. They are shown in their pre-Ivan condition in Figure 
3-34, and after Ivan in Figure 3-35. The lower pairs of buildings in each 
figure were newer, having been rebuilt after their predecessors (built 
on shallow foundations) collapsed during Hurricane Georges (1998). 
The upper pair of buildings (also on shallow foundations) survived 
Georges but collapsed during Ivan. 

Figure 3-33. 
Hurricane Ivan, nonstructural 
enclosure and 
deck damage below 
newer building 



The lessons learned in Hurricane Georges served the owners of the 
bottom pair of buildings well during Ivan. These buildings were re-con
structed 
following Georges with deep-pile foundation systems, and the 
foundations performed well during Ivan. The building on the left lost 
the ground floor parking slab as seen in Figure 3-36, and suffered sub
stantial 
roof covering loss due to wind. The building on the right had a 
structural parking slab, which was undermined by Ivan but undamaged. 
The building had only minor cladding damage due to the wind. 


Figure 3-34. 
Four Orange Beach 
condominiums before 
Hurricane Ivan. The 
lower pair of buildings 
was newer, having 
been constructed after 
the predecessors were 
destroyed by Hurricane 
Georges (1998) (USGS) 



Figure 3-35. 
The four condominiums 
in Figure 3-34 after 
Hurricane Ivan. The 
newer buildings on pile 
foundations survived, 
while the older buildings 
on shallow foundations 
collapsed. However, the 
newer building on the 
lower left experienced 
significant interior water 
damage due to roof loss. 
(USGS) 



Residential Buildings 

Figures 3-37 and 3-38 show two residences near Big Lagoon after Ivan: 
an elevated building constructed to a newer code and an adjacent 
non-elevated building constructed to an older code. The difference 
in the performance of each building is apparent. The newer building 
sustained only non-structural flood damage at grade level, with no ap
parent 
wind damage to the roof or building envelope (the building 
performed as expected). The older building was severely damaged by 
flood and wind forces. This comparison demonstrates the importance 
of building elevation and wind-resistant design. 


Figure 3-36. 
Deep foundation exposed by erosion, and 
collapse of undermined parking slab, as 
shown in the photo on the right. 



As discussed throughout this report, elevating a house on piles to the 
minimum standards and preferably several feet higher can prevent sig
nificant 
damage. Figure 3-39 shows an older house with a slab-on-grade 
foundation that was not elevated to the current BFE and that sustained 
considerable damage from Hurricane Ivans high storm surge and de
bris 
impacts. Figures 3-40 and 3-41 show two houses located in the 
same general area as the house shown in figure 3-39, but, because they 
were elevated on piles to higher standards, they sustained minimal 
flood damage. 

Figure 3-37. 
Elevated building 
constructed to newer 
code that survived 
Hurricane Ivan (Big 
Lagoon) 


Figure 3-38. 
Older, non-elevated 
building (near building 
in Figure 3-37) severely 
damaged in Hurricane 
Ivan (Big Lagoon) 



Figure 3-39. 
House on La Paz Street 
that was not elevated to 
the current BFEs, and, 
therefore, was severely 
damaged by the high 
coastal flooding and 
wave impacts 


Figure 3-40. 
House on La Paz Street 
that was elevated on 
piles, which prevented 
severe damage from 
coastal flooding 



Following Hurricane Ivan, Alabama homeowners with houses con
structed 
to standards exceeding the adopted building code were 
rewarded with significantly less damage. The higher building stan
dards, 
contained in the IRC and IBC, require far stronger framing, 
connections, walls and roofs that will withstand winds up to 140 mph. 
The homeowner of the surviving house shown in Figure 3-42 con
structed 
the house on Orange Beach to the new code, before the town 
adopted the IRC and IBC in June 2004. As a result, the house had 
virtually no damage, although numerous houses nearby had signifi
cant 
damage or were destroyed. Figure 3-42 demonstrates the contrast 
between a house destroyed by wind and flood forces and a house that 
survived because it was built to the new code. 


Figure 3-41. 
House on La Paz that 
was elevated on piles, 
which prevented major 
flood damage 


Figure 3-42. 
The surviving house 
was built to incorporate 
the provisions of the 
new building code (IRC, 
IBC) even before it was 
adopted. (Orange Beach) 



T 


C H A P T E R 4 

4-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

4 

Structural 
Systems Performance 

The dominant causes of structural failure observed by the MAT included surge, waves, flood
borne 
debris, and wind. Structural damage due to erosion was also common on the barrier 
islands. These types of damage occurred to residential buildings (single- and multi-family 
housing), commercial buildings, and critical and essential facilities. 

Flood impacts are discussed in Section 4.1. Subsections 4.1.1 and 4.1.2 discuss the flood im
pacts 
on single-family and multi-family residential buildings, respectively. Subsection 4.1.3 
discusses flood impacts to miscellaneous structures associated with residential buildings, such 
as bulkheads, non-structural slabs, breakaway walls, and utilities. Section 4.1.4 discusses im
pacts 
of debris borne by floodwaters. Flood impacts on commercial buildings were similar to 
those on residential buildings; thus, commercial buildings are not discussed separately. Wind 
impacts are discussed in Section 4.2. 

4.1 Flood 

4.1.1 Single-Family Residential Buildings 

Single-family buildings throughout the western sections of the Florida Panhandle and the coast
al 
areas of Baldwin County, Alabama, incurred significant damage caused by high floodwaters 
with wave action and debris impacts. In general, the damage resulted less from foundation 
failures (although these were observed) than from the high flood elevations (which exceeded 
the BFEs) and from the impacts of wave action and debris. In coastal back bay areas desig
nated 
as flood Zones AE, severe damage was caused by wave action and debris generated from 
docks and damaged buildings, including debris originating on the barrier islands that washed 
across the sounds and bays. 



C H A P T E R 4 

STRUCTURAL SYSTEMS PERFORMANCE 

4-2 

 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

Many structures constructed on pile foundations performed well, es
pecially 
those buildings built several feet above the minimum flood 
elevation standards. Structural failures resulting from flooding gen
erally 
correlate with the first floor elevation of the building, although 
some failures also resulted from erosion and improper connections 
between structural components. In general, the lower the elevation 
of the first floor of a building, the more the building was damaged. 
In coastal areas where the lowest floor elevation was lower than the 
wave crest elevation, the building was not only inundated by flood
ing, 
but also extremely susceptible to additional lateral and impact 
loads from wave action, floodborne debris, and velocity flow. 

4.1.1.1 Pile Foundations 

Pile foundations were the most common foundation type for resi
dential 
buildings on the barrier islands and were also common for 
newer construction on the bay and sound shorelines. Generally, 
buildings constructed on pile foundation systems performed well, es
pecially 
those constructed with the lowest floor several feet above the 
BFE. Exceptions were buildings with shallow pile embedment on the 
barrier islands which experienced significant erosion and pile-sup
ported 
buildings anywhere the wave crests exceeded the elevation of 
the lowest floor. 

Barrier Islands 

Figures 4-1 through 4-3 show barrier island houses that experienced 
destruction of enclosures below the houses. Structurally, these houses 
performed well, but the breakaway walls, non-structural parking slabs, 
and the contents below the lowest floor were generally destroyed. This 
type of damage is anticipated when floodwaters and waves rise above 
the parking slab and batter the breakaway walls forming a below BFEenclosure. 
Figure 4-4 shows another problem observed by the MAT 
 survival of residential buildings on pile foundations, but damage or 
destruction of pile-supported decks. Deck failure was sometimes due 
to deck foundation failure (piles supporting decks often are smaller 
and shorter than the building foundation) and sometimes to wind 
failure (uplift). In some instances, loss of decks led to envelope or 
structural damage to the houses. 

In instances where pile-elevated buildings had their lowest floor at or 
just below the wave crest elevation during Ivan, damage to the floor 
system was observed. Figure 4-5 shows a typical example, where the 
piles and shore-perpendicular floor beams performed as intended, 
but where the wave crests struck the shore-parallel floor joists. The 



STRUCTURAL SYSTEMS PERFORMANCE 

lateral forces exceeded the capacity of the joist connections, and the 
joists were pushed landward. The collapse of the joists was usually ac
companied 
by damage to the floor and the building interior. 


Figure 4-1.
House on a pile 
foundation that 
performed well. It 
experienced 5 feet of 
erosion that resulted in 
failure of a non-structural 
slab. Breakaway walls in 
lower level also failed as 
expected. (Gulf Shores) 


Figure 4-2. 
House on pile foundation, 
adjacent to breach in 
the barrier island, that 
experienced erosion and 
significant non-structural 
damage below the lowest 
floor (Gulf Shores). 



Figure 4-3. 
These pile-elevated 
houses in an area 
mapped as Zone VE 
at Pensacola Beach 
successfully resisted 
flood forces. Loss of 
breakaway enclosures 
and garage doors 
below the lowest floors 
occurred, as expected. 
(FL DEP Photo) 


Figure 4-4. 
Row of newer houses 
on pile foundations that 
experienced significant 
damages below the 
lowest floor, but overall 
the pile foundation 
systems performed 
well. Improper pile 
embedment for decks 
remains a concern as 
shown in the two houses 
in the center; one house 
shows the deck is 
sagging, and the other 
deck was destroyed. 
(Gulf Shores) 



Erosion can have a significant impact on the performance of pile foun
dations 
that are not embedded deeply enough in the soil. Many newer 
buildings with deep pile foundations performed well; however, there 
were numerous older buildings that lacked sufficient pile embedment 
to account for the loss of soil due to erosion and scour. In these in
stances, 
permanent deformation or failure of the foundation resulted. 
Figures 4-6 through 4-9 show several examples of failure of the pile 
foundations  either under buildings or under decks  that lacked suf
ficient 
embedment depth and structural capacity to resist Ivans flood 
and wind forces. 


Figure 4-5. 
Floor joists were pushed 
landward when the wave 
crest elevation was 
above the floor beam. 
(Gulf Shores) 


Figure 4-6. 
Significant erosion 
caused the nonstructural 
parking slab 
to fail, and insufficient 
pile embedment caused 
the structure to lean. 
The high storm surge 
and waves caused 
destruction of the 
enclosure below the 
lowest floor. 
(Orange Beach) 



Figure 4-7. 
Erosion contributed to 
loss of the porch, failure 
of the retaining wall and 
non-structural parking 
slab, and destruction 
of the enclosure below 
the first floor. The main 
structure remained 
standing, but appears 
to have sustained some 
envelope damage when 
the porch failed. 
(Orange Beach) 


Figure 4-8. 
The pile foundations in 
the foreground failed. 
These houses were 
washed away (see 
Figures 3-2 and 4-9). 



Bay and Sound Shorelines 

Pile-foundation performance along inland bays and sounds varied 
depending on the flood level, the pile diameter, and pile-to-beam con
nections. 
Most of the pile-elevated houses observed by the MAT along 
bay and sound shorelines were probably constructed in Zones A, B, 
or C; V Zones mapped along the bay and sound shorelines were rela
tively 
narrow, and relatively few houses were actually constructed in 
V Zones. However, many of the areas mapped as Zone A sustained 
V-Zone conditions during Ivan, and those areas mapped as Zone V 
usually sustained flood conditions far worse than those indicated by 
the FIRM. Where floor elevations were below the wave crest elevation, 
buildings were damaged or destroyed; where small diameter piles were 
struck by waves and large debris, they failed; where connections at the 
tops of the piles were inadequate, they failed. 

As with the barrier islands, most of the pile foundations along bay and 
sound shorelines performed well where the lowest floor was elevated 
several feet above the BFE. In other cases, where pile-elevated houses 
were at or near the BFE, they often were heavily damaged by waves and 
debris (see Figures 4-10 and 4-11), sometimes torn completely from 
the pile foundations (see Figures 4-12 and 4-13). 


Figure 4-9. 
These houses floated off 
their pile foundations 
(shown in Figures 4-8 
and 3-2), probably a 
result of inadequate pile 
embedment. 



Figure 4-10. 
House constructed on 
a pile foundation in a V 
Zone along Escambia 
Bay. The house was 
apparently built in 
compliance with VZone 
requirements (BFE 
of 12 feet NGVD), but 
still experienced wave 
impacts on the elevated 
first floor of the building. 
(Floridatown) 


Figure 4-11. 
Damage to pile-supported 
house on a bay shoreline, 
when flooding and waves 
exceeded the lowest floor 
elevation (Gulf Breeze, 
Pensacola Bay) 



The destroyed house on the left side of Figure 4-12 was in the Grande 
Lagoon neighborhood, approximately  mile across Big Lagoon from 
the barrier island, Perdido Key. Perdido Key was completely overwashed 
by Ivan, and stillwater flood levels in the vicinity of Grande Lagoon 
were approximately 13 to 14 ft NGVD (see Figure 1-11), with wave 
crest elevations higher. Flood hazard zones and BFEs shown on the 
FIRMs for this area ranged from VE, elevation 11 feet NGVD, to AE, el
evation 
9 feet NGVD. Figure 4-13 shows the same house (circled) with 
several nearby, pile-elevated houses that were also destroyed. It should 
be noted that some older but intact houses in the neighborhood were 
observed to have poor connections between the floor beams and the 
elevated houses. Wind might also have contributed to the structural 
failures seen in Figures 4-12 and 4-13. 

Figure 4-12. 
House at left (circle) 
was torn from its pile 
foundation. New houses 
under construction 
(arrows, see Figure 4-31 
also) survived Ivan 
(Big Lagoon). 


Figure 4-13. 
Same destroyed house 
as in Figure 4-12 
(circled). Note adjacent 
pile-elevated houses 
near shoreline, also 
destroyed (Big Lagoon). 



Another nearby neighborhood also illustrates the value of a sound 
pile foundation along bay and sound shorelines. Figure 4-14 shows 
an older pile-elevated house near the east end of Seaglade Drive, ap
proximately 
one mile east of the Grande Lagoon neighborhood and 
exposed to similar flood conditions during Ivan. This house is in an 
area mapped as Zone AE, elevation 9 feet NGVD. The enclosure at 
ground level was destroyed, but, otherwise, the house sustained little 
flood damage. 

Figure 4-15 shows the region just to the west of the house in Figure 4- 
14. Older unreinforced masonry houses on slab foundations (arrows) 
were destroyed, but other houses elevated on piles above the BFE (cir
cled) 
survived. MAT team members observed many debris scars 5-to-7 
feet above the base of trees in the area, giving an indication of flood 
depths during Ivan. Debris scars were also evident on the underside 
of the joist sheathing of the house circled on the right side of Figure 
4-15. The house was elevated one full story to allow for under-house 
parking. The dashed line in Figure 4-15 shows the landward limit of 
floodborne debris in the area; Figure 4-16 shows some of the debris. 

Figure 4-14. 
House constructed on 
piles several feet higher 
than the BFE. Floodwater, 
waves, and debris caused 
damages to the ground 
level enclosed area of 
the house, but not to the 
elevated portion. 
(Big Lagoon) 



glade Drive. Flood damages in the Sinton Drive area were consistent 
with those observed at Grande Lagoon and Seaglade Drive: survival 
damage to houses elevated at or near the BFE (see Figure 4-18), and 
destruction of older houses at or near grade. The flood hazard zone 
and BFE for the house in Figure 4-17 are AE, elevation 8 feet NGVD, 
but this area experienced V-Zone conditions, i.e., water levels close to 
14 feet NGVD with waves and floodborne debris. 
Another location visited by the MAT along the north shoreline of Big 
Lagoon, was the Sinton Drive area, approximately 1.5 miles east of Sea
of 
pile-elevated houses several feet above the BFE (see Figure 4-17), 


Figure 4-15. 
Area just to the west 
of the house shown in 
Figure 4-14. Pile-elevated 
houses above the BFE 
(circled) survived, 
while older houses on 
slab foundations were 
destroyed. Dashed line 
indicates landward limit 
of debris that washed 
through the area. 

Figure 4-16. 
Ground view of some 
of the debris shown in 
Figure 4-15. 



4.1.1.2 Slab on Grade 

Buildings constructed with slab-on-grade foundations were widely ob
served 
throughout the affected area, and generally fell into two classes: 
1) pre-FIRM houses inside and outside the SFHA, and 2) post-FIRM 
houses outside the SFHA. Many of these buildings sustained signifi
cant 
damage or were destroyed. In numerous cases, the high level of 
damage was associated with water levels several feet above the slab, ac
companied 
by waves and floodborne debris (see Figures 4-19 through 
4-22). Inundation-only damage was observed in flooded houses far 
from the shoreline (see Figure 4-23). Slab failure due to erosion was 
frequently evident on the barrier islands, but less so on the bay and 
sound shorelines. 

Figure 4-17. 
This house located 
near Sinton Drive 
successfully resisted 
flood forces since it was 
elevated higher than 
the BFE on piles (note 
the wind damage: loss 
of vinyl siding, soffit 
and roof covering). 
Lower, adjacent houses 
(see Figure 4-18) were 
destroyed. 
(Big Lagoon) 


Figure 4-18. 
This photo shows the 
destroyed building 
adjacent to the house 
in Figure 4-17. It was 
destroyed (knocked 
off the masonry pier 
foundation) by some 
combination of storm 
surge, wave and debris 
impacts, and wind. 
(Big Lagoon) 



Figure 4-19. 
The pre-FIRM building 
constructed on a 
slab foundation 
(foreground) was 
completely destroyed, 
yet the adjacent building 
constructed on piles 
at a higher elevation 
remained intact and 
suffered relatively little 
damage. (Big Lagoon) 


Figure 4-20. 
Destruction of slab-ongrade 
house (circled) 
in the Grande Lagoon 
neighborhood. Adjacent 
houses elevated on piles 
above the BFE sustained 
destruction of ground 
level enclosures and 
some wind damage, but 
survived. (Big Lagoon) 



Figure 4-21. 
The unreinforced 
masonry pre-FIRM 
building in the foreground 
was swept off its slab 
foundation during Ivan. 
On the adjacent building, 
the lowest floor was 
gutted and the walls 
ripped out by wave and 
debris impacts. 
(Oriole Beach) 


Figure 4-22. 
This slab-on-grade 
building located on the 
back side of the barrier 
island but directly on 
the sound was heavily 
damaged by wave action. 
(Pensacola Beach) 



4.1.1.3 Stem Walls 

Overall, the MAT observed that stem wall foundations performed well 
against the storm surge, and wave and debris impacts near bay and 
sound shorelines. However, the MAT observed several buildings where 
the stem wall foundations survived, but the buildings atop the founda
tions 
were destroyed (see Figure 3-8) or heavily damaged (see Figures 
4-24 and 4-25). In one instance, a stem wall foundation was used to 
elevate a house (under construction) above the BFE, and damage to 
the unfinished house was relatively minor  porch columns and one 
exterior wall were damaged, apparently by waves or debris slightly ex
ceeding 
the top of the foundation (see Figure 4-26). 

In all cases observed by the MAT, scour around the stem wall founda
tions 
was limited, and foundation failures did not occur; however, this 
type of foundation would be expected to be vulnerable to scour and 
erosion on barrier islands or on higher relief, sloping bay shorelines. 

Figure 4-23. 
The slab-on-grade 
building located near 
the back side of the 
barrier island was 
protected from wave 
action by other houses, 
but had 4 to 5 feet of 
water inside. (Pensacola 
Beach) 


Stillwater
Level 



Figure 4-24. 
House constructed in 
a Zone AE on a stem 
wall foundation, which 
survived, although high 
floodwaters with debris 
and wave action caused 
major damage (Big 
Lagoon) 


Figure 4-25.
Stem wall foundation 
where floodwater 
exceeded required 
flood elevation by 
approximately 4 feet 
(Garcon Point, Escambia 
Bay) 



4.1.1.4 Piers 

Many pier foundations were observed to perform poorly, although 
many of these foundations were used for older, pre-FIRM structures 
and were minimally reinforced or unreinforced. Figures 4-27 and 4-28 
show examples of pier foundation failures at older structures. Figure 
3-3 shows a newly constructed house on piers that was severely dam
aged 
by waves and debris that exceeded the height of the lowest floor 
although the piers themselves remained intact. 

Pier foundations are typically constructed on shallow footings, which 
are prone to failure due to erosion and scour. Tall pier foundations are 
also prone to failure from overturning when flood loads are applied 
to the building. Pile foundations generally perform better than pier 
foundations, especially when constructed in sandy material, which is 
vulnerable to erosion and scour (see Figure 4-29). Pile foundations 
provide much more flexibility and cost efficiencies to account for 
increases in elevation of the finished floor of the structure and for ad
ditional 
embedment to allow for any erosion and scour that will likely 
occur on sandy beaches. 

Figure 4-26. 
This stem foundation 
elevated the house above 
the BFE and performed 
well. The house, which 
was under construction 
at the time of Ivan, 
sustained minor flood 
damage to the walls and 
the columns under the 
porch. (Tiger Point, Santa 
Rosa Sound) 



Figure 4-27. 
Unreinforced pier 
foundations failed due to 
scour at the footing and 
flood levels exceeding 
the floor elevation (Oriole 
Beach). 


Figure 4-28. 
Center pier failed causing 
the elevated floor to 
collapse. Other adjacent 
buildings were elevated 
on pilings and solid 
foundation walls; the 
piers performed better 
than the solid walls, but 
not as well as the pilings 
(Santa Rosa Sound) 



Manufactured houses placed on unreinforced, dry-stacked block piers 
were observed to shift in some cases due to the storm surge and wave 
action effects. Figures 4-30 through 4-32 provide several examples of 
piers shifting under manufactured houses. These types of piers are not 
suitable for coastal areas. 

Figure 4-29. 
Tall, lightly reinforced 
masonry piers failed 
due to lateral loads 
from surge and 
wave action. The pile 
supported houses 
under construction in 
the background are the 
same ones indicated (by 
arrows) in Figure 4-12. 
(Big Lagoon) 


Figure 4-30. 
Manufactured home 
park where houses 
experienced storm 
surge, scour, and 
foundation collapse 
(Orange Beach) 



Figure 4-31. 
Unreinforced, dry-stacked 
block piers slid off of 
footings. (Orange Beach) 


Figure 4-32. 
Dry-stacked pier failure 
(Orange Beach) 



4.1.2 Multi-Family Residential Buildings 

With a few exceptions, newer multi-family structures on the barri
er 
islands generally withstood Ivans flood and erosion effects quite 
well, with the exception of lower floors of some buildings that were 
heavily damaged when Ivans waves exceeded local BFEs and when 
erosion undermined nonstructural slabs. Many multi-family build
ings, 
however, sustained wind damage at less than design wind speeds 
(see Section 4.2). 

One class of multi-family buildings sustained significant flood damage: 
those buildings constructed on shallow foundations on the barrier is
lands. 
Ivan caused up to eight feet or more of vertical sand loss in some 
beachfront areas, and several buildings not constructed with deep 
foundations collapsed. This was the first time that MAT members had 
seen catastrophic failures of multi-family buildings due to erosion. In 
some areas (e.g., Pensacola Beach, central Gulf Shores), undermining 
failures of some buildings on shallow foundations were probably pre
vented 
by recent beach nourishment projects. 

The observed damages are discussed below by foundation types: shal
low 
foundation and pile supported. Damages to bulkheads and pools 
are discussed in 4.1.3.1. 

4.1.2.1 Shallow Foundations 

Hurricane Ivan produced significant storm surge and high waves that 
caused widespread and severe erosion along the barrier islands of 
Baldwin County, Alabama, and the northwestern Florida Panhandle. 
In general, sand loss up to 8-10 feet high was observed, and 100 feet or 
more of dune loss was observed in some areas. Due to the severe sand 
loss, buildings constructed on shallow foundations experienced sig
nificant 
failure and collapse. Many of these buildings were constructed 
in flood Zones B or C, in which the NFIP has no specific foundation 
requirements. However, the FBC requires buildings constructed sea
ward 
of the CCCL to be constructed on pile foundations. In Alabama, 
where coastal construction requirements are not as strict as Floridas 
CCCL, severe building damage occurred as a result of erosion to soils 
supporting shallow foundations and surrounding shallowly embedded 
pile foundations. Figures 4-33 and 4-34 show a post-1997 building that 
was constructed on a shallow foundation in a Zone B. This building 
experienced total collapse during Hurricane Ivan. Figure 4-35 shows 
a similar collapsed building and the success of the adjacent buildings 
constructed on piles and columns. 



Figure 4-33. 
Total collapse of 5-story 
building on a shallow 
foundation (Orange 
Beach) 


Figure 4-34. 
Close-up of building 
shown in Figure 4-33 
(Orange Beach) 



Figure 4-36 shows before and after Hurricane Ivan photos of a 5-story 
building that was constructed on a shallow foundation in flood Zone 
C in the late 1990s. The lowest floor elevation was 19 feet NGVD, sev
eral 
feet above the highest BFE shown nearby on the 1992 FIRM in 
effect when the building was constructed. However, the supporting 
soil was undermined during Ivan and the seaward two-thirds of the 
building collapsed. Review of the permitting file shows initial calcula
tions 
indicated erosion would occur beneath the seaward edge of the 
foundation during a base flood event. Sand was added to the dune to 
compensate for the potential undermining, but it was obviously a poor 
decision to rely on a shallow foundation and a crude erosion calcu
lation. 
Figure 4-37 shows another multi-family building on a shallow 
foundation damaged by Hurricane Ivan. In this case, the storm under
mined 
just the front of the building, causing it to settle, and damaging 
all eight stories. 

Figure 4-38 shows ground and aerial views of older buildings at Pen
sacola 
Beach, elevated on masonry walls and columns atop shallow 
footings. The seaward row of buildings survived Hurricane Opal in 
1995 but did not survive Ivan in 2004, due in large part to the severity 
of Ivan. This scene will be repeated less and less in the future since new 
construction on Pensacola Beach is restricted to pile foundations by 
the local unit of government, the Santa Rosa Island Authority (SRIA). 
SRIA has mandated V-Zone design and construction standards and 
required 1 to 3 feet of freeboard across the entire barrier island com
munity 
(V Zones and A Zones) since before Hurricane Opal. After 
Ivan, SRIA is modifying their ordinance to require 3 feet of freeboard 
everywhere. 

Figure 4-35. 
Shallow foundation 
failure. Note success of 
pile support structures in 
the background. (Orange 
Beach - Perdido Key) 



Figure 4-36. 
Collapse of a 5-story 
building constructed on 
a shallow foundation. 
Arrows identify buildings 
before and after Ivan. 
(Orange Beach) Photo 
courtesy of USGS 



Figure 4-37. 
Collapse of the seaward 
portion of a high-rise 
building supported by 
a shallow foundation 
(Perdido Key) 


Figure 4-38. 
Older buildings constructed on masonry columns and 
walls atop shallow footings (Pensacola Beach). 



Although many multi-family structures were not affected by erosion 
during Ivan, many were affected by high winds, storm surge, waves, 
and floating debris. Figure 4-39 shows a building located on the north 
side of Pensacola Beach, near the Santa Rosa Sound shoreline. NFIP 
records indicate flood claims have been paid for units in the build
ing 
on four occasions: September 1998 (Hurricane Georges), October 
1995 (Hurricane Opal), August 1995 (Hurricane Erin), and Septem
ber 
1979 (Hurricane Frederic). 

Figures 4-40 and 4-41 show another pre-FIRM multi-family building on 
a slab foundation that was heavily damaged by storm surge, waves, and 
debris, this one on the north side of Santa Rosa Sound. 

Figure 4-39. 
This building has been 
flooded by Hurricane Ivan 
and four prior storms. 
(Pensacola Beach) 



4.1.2.2 Pile Foundations 

Pile foundations in multi-family structures generally performed very 
well, although the high storm surge elevations caused considerable 
damage to ground level enclosures and to some lowest floor living units, 
especially to those Orange Beach buildings constructed in flood hazard 
Zones B, C, or X, where BFEs had not been established. The use of pile 
foundations for multi-family buildings avoided the severe damage and 

Figure 4-40. 
Multi-family building on 
a bay shoreline, heavily 
damaged by surge, 
waves, and floating 
debris (Oriole Beach, 
Santa Rosa Sound) 


Figure 4-41. 
Aerial view of building in 
Figure 4-40 (circled) 



collapse observed at buildings with shallow foundations but, by itself, 
was not sufficient to prevent loss of lowest floor living units. Full compli
ance 
with VE-Zone construction standards (e.g., use of a structural floor 
system and elevation of the lowest horizontal structural member above 
the wave crest elevation) was also necessary to prevent damage to those 
living units (see Figures 4-42 through 4-44). In some instances, buildings 
were sited far enough from the shoreline that erosion was not an issue, 
but Ivans surge and wave action was still sufficient to damage the lower 
story. 


Figure 4-42. 
Multi-story buildings 
on piles, impacted by 
storm surge, waves, and 
erosion, which damaged 
many lower area walls 
and floors (Orange Beach) 


Figure 4-43. 
Although the pile 
foundation and structural 
elements survived, 
damage to lowest floor 
exterior walls, interior 
partitions, and floor slabs 
occurred during Ivan. 
(Orange Beach) 



A separate study of Orange Beach multi-story structures was under
taken 
to determine the extent and characteristics of lowest floor living 
unit damages (see Appendix F). The study examined 41 multi-story 
structures, not including the collapsed structures. Thirty-nine of the 
41 buildings had a total of 233 living units at the lowest floor level. The 
buildings were constructed over the years in flood hazard zones B, C, 
AE, and VE, using high-rise construction techniques typical for their 
respective zones. 

Approximately 80 percent of the lowest floor living units were de
stroyed 
by flood and/or erosion effects. Although most of the tops of 
the lowest floors were at or above the highest BFEs appearing on any 
of the FIRMs in the past 20 years, much damage was still sustained by 
the buildings, due to lowest floor collapse and/or stillwater levels dur
ing 
Ivan that exceeded BFEs by up to 2 feet (see Table 1-2 and Figure 
1-8), with wave crest elevations higher yet. 

Figures 4-45 and 4-46 show a pile and column supported building at 
Pensacola Beach that sustained little flood damage, despite severe 
scour around its foundation, since use of the grade level area was lim
ited 
to parking and building access. 

Figure 4-44. 
Pile foundations alone 
are not enough; elevation 
of the lowest floor is also 
critical. The building on 
the left shows minimal 
damage, while the 
building on the right 
with the lower-level 
living units experienced 
significant non-structural 
damage. (Orange Beach) 



Figures 4-47 through 4-49 show examples of other flood and erosion 
damages that affected multi-family buildings on the barrier islands. Fig
ure 
4-47 shows a Perdido Key lower floor living unit that was flooded 
and buried in sand; no structural damage occurred to the building as 
a result, but the lower unit walls, fixtures, and contents were destroyed. 
Figure 4-48 shows several Orange Beach multi-family structures whose 

Figure 4-45. 
This condominium on 
a deep foundation is 
located on the back side 
of the barrier island, north 
of Ft. Pickens Road. This 
building was severely 
damaged by wind, along 
with some utility damage 
in the lower level, and 
severe scour around 
the concrete pile caps. 
Since it was constructed 
on deep foundations 
and there were limited 
enclosures below the first 
floor, damage caused by 
storm surge was limited. 
(Pensacola Beach) 


Figure 4-46. 
Aerial view of the 
building shown in Figure 
4-45 (FL DEP photo) 
(Pensacola Beach) 



bulkheads, pools, decks, and lower floor spaces were damaged or de
stroyed. 
Figure 4-49 again illustrates the relative damages associated 
with deep and shallow foundations during Ivan; the 5-story building 
in the center (shallow foundation) collapsed, while the buildings on 
either side (deep foundations) sustained flood damage to the ground 
level enclosures and parking areas only. 


Figure 4-47. 
Building with flood and 
wave damage to the 
lowest floor living units. 
Some units had up to two 
feet of sand deposited 
inside. (Perdido Key) 

Figure 4-48. 
Most of the first floor 
units in these buildings 
were severely damaged 
(see Figures 4-53 and 
4-54). (Orange Beach) 



4.1.3 Miscellaneous Structures 

This section discusses observed damages and successes for various 
elements related to single and multi-family residential structures, in
cluding 
bulkheads, non-structural slabs, breakaway walls, and utilities. 

4.1.3.1 Bulkheads 

Bulkheads were used around many single-family and multi-family struc
tures 
along the open coast in Gulf Shores and Orange Beach, Alabama. 
These structures were not observed as frequently along beaches in 
Florida due to state-mandated restrictions on coastal armoring. Their 
general purpose is to retain soil and provide protection from erosion. 
They are often used to contain sand that supports pool decks and nonstructural 
parking slabs beneath buildings. In most cases, these walls 
were observed to have been damaged or destroyed by Ivan. 

High storm surge, waves, and erosion resulted in frequent damages 
to bulkheads, pools, and pool decks. Figure 4-50 shows a typical pool 
failure. Lightweight bulkheads (particularly those constructed of vinyl 
and timber) sustained significant damage during Ivan (see Figures 4-51 
and 4-52). Some concrete bulkheads failed, but the more substantial 
ones remained intact. However, even intact concrete bulkheads were 
sometimes overtopped and suffered erosion on the landward side (see 
Figures 4-53 and 4-54). 


Figure 4-49. 
Pile-supported buildings 
performed much 
better than buildings 
constructed on shallow 
foundations as shown in 
the building in the center, 
which collapsed. (Orange 
Beach) 



Figure 4-50. 
Typical pool failure 
(Pensacola Beach) 


Figure 4-51. 
Retaining wall failure 
(Gulf Shores) 



Figure 4-52. 
Failure of vinyl bulkhead with concrete cap 
(Orange Beach) 


Figure 4-53. 
Bulkhead remained 
intact, but short return 
wall allowed erosion 
behind the wall 
(Orange Beach) 



4.1.3.2 Non-Structural Slabs 

Many pile-elevated single-family and multi-family buildings were con
structed 
with non-structural parking slabs that relied on the underlying 
soil for support. When the underlying soil was washed away by Ivan, 
the slabs were undermined and almost always collapsed, as expected 
(some remained in place because they were tied to the pilings). Fig
ures 
4-55 through 4-58 show typical examples of the performance of 
these non-structural slabs. 

Figure 4-54. 
Bulkhead shown in Figure 
4-53 remained in-place, 
but surge and wave 
overtopping, coupled 
with erosion at the short 
return wall, led to deck 
and retaining wall failure. 
(Orange Beach) 


Figure 4-55. 
Sand below slab 
completely eroded away, 
causing the total failure 
of slab, but grade beams 
remained intact. (Gulf 
Shores) 



Figure 4-56. 
Concrete slab partially separated from the 
pile even though it had been connected with 
a nail. These slabs should break free cleanly 
so they do not transfer flood loads to the 
foundation. (Gulf Shores) 


Figure 4-57. 
Typical non-structural 
concrete slab failure. 
Horizontal line 
indicates previous 
location of soil level 
and slab. 
(Orange Beach) 



4.1.3.3 Breakaway Walls 

Walls used for enclosures below the BFE in areas designated as Zone 
VE must be designed to break away under the base flood. Break
away 
walls are required in such instances so as to limit the transfer 
of wave and debris loads to the pile-elevated building foundation. 
The MAT observed the vast majority of breakaway walls functioned 
as intended (see Figure 4-59). However, in some instances the MAT 
observed some problems with breakaway wall design and construc
tion. 
For example: 

. Some breakaway walls did not break away cleanly, causing damage 
to wall finishes above the breakaway panels (see Figure 4-60). 

. In some cases, utilities were connected to the walls, thereby 
preventing a clean wall failure (see Figure 4-61). 

. In some cases, breakaway walls were installed across pilings instead 
of between pilings (see Figure 4-62). 

Figure 4-58. 
This slab failed but 
did not break into 
small pieces due to 
the reinforcing steel. 
The incomplete slab 
failure might have 
transferred flood forces 
to the foundation 
and contributed to 
the pile failure (piles 
in background were 
partially pulled out of the 
ground and are leaning). 
(Orange Beach) 



Figure 4-59. 
Failure of breakaway 
walls as designed (Gulf 
Shores) 


Figure 4-60. 
Poor detailing of the joint 
between the breakaway 
wall and the wall above 
contributed to loss of wall 
covering above the floor 
beam. (Pensacola Beach). 



4.1.3.4 Utilities 

The MAT observed significant damages to utilities at residential 
structures. The damages occurred due to the locations of utility com
ponents, 
their support, and their attachment. Figures 4-63 through 
4-71 illustrate typical utility performance concerns observed by the 
MAT, all of which are discussed in FEMA 348, Protecting Building Utilities 
from Flood Damage and FEMA 55, Coastal Construction Manual: Principles 
and Practices of Planning, Siting, Designing, Constructing, and Maintaining 
Residential Buildings in Coastal Areas. 


Figure 4-61. 
Failure of interior 
partition to break away 
cleanly due to the 
attachment of utilities 
(Gulf Shores) 


Figure 4-62. 
Breakaway walls were 
nailed over the piles and 
floor beam, preventing a 
clean break. (Gulf Shores) 



Figure 4-63. 
Loss of condenser 
platform support. A 
cantilevered condenser 
support is recommended 
(see Figure 8-3). 
(Pensacola Beach) 


Figure 4-64. 
Diagonal condenser platform members are 
susceptible to wave and waterborne debris 
damage. Cantilevered condenser platforms are 
preferable (see Figure 8-3). (Gulf Shores) 



Figure 4-65. 
Elevator system severely damaged by surge, 
waves, and debris (Gulf Shores) 


Figure 4-66. 
Loss of platform supports 
and air conditioning unit 
due to erosion and flood 
forces (Gulf Shores) 



Figure 4-67. 
House under construction at the time of 
Ivan (Big Lagoon). Note the condenser 
platform foundation survived the flood forces 
(masonry-column-supported house in the 
foreground was destroyed). 


Figure 4-68. 
Erosion and flood 
damage to multi-family 
electrical transformer 
and interior mechanical 
room (Perdido Key) 



Figure 4-69. 
Debris and sand in low-elevation mechanical 
room (Perdido Key) 


Figure 4-70. 
Damage to the electrical 
panel, but utility 
lines were located 
appropriately (beside an 
interior pile) (Pensacola 
Beach) 



4.1.3.5 Stairs 

As coastal residences get more expensive and elaborate, the access 
stairs are getting larger and more substantial. In most cases, this does 
not present a problem; however, in some cases the stair structures 
could act as obstructions and could potentially transfer flood loads or 
cause wave deflection onto elevated structures. Figures 4-72 and 4-73, 
respectively, show examples of stairs that are and are not likely to act 
as obstructions. 

Figure 4-71. 
Drain lines constructed between interior 
piles (which helped to protect them from 
flood forces), although electrical box was 
connected to plywood panel and was 
destroyed (Pensacola Beach) 



4.1.4 Debris Impacts 

Besides the building damage that resulted directly from storm surge, 
wave action, and erosion, severe damage was often caused by float
ing 
debris. Debris damage was common along the barrier islands, but 
seemed especially abundant in the back bays due to the large debris 
fields generated by more seaward damaged or destroyed buildings, 
decks, and dune walkovers, and by numerous docks along the bay 
shorelines. It was not uncommon to see debris from barrier islands 
that had floated across sounds and bays, damaging houses along those 


Figure 4-72. 
Massive stairs that will 
obstruct flows could 
deflect waves and 
debris into the elevated 
building. This type of stair 
structure is a violation 
of the V-Zone free-ofobstruction 
requirement. 
(Gulf Shores) 


Figure 4-73. 
Stairway structures 
(circled) that will 
minimize obstructions 
to flow and potential 
adverse effects on the 
elevated building (Gulf 
Shores) 



inland shorelines. Also, below-BFE enclosures were destroyed by the 
thousands throughout the storm impact area, adding significantly to 
the debris field available to damage other buildings. 

Typical examples of debris impacts are shown in Figures 4-74 
through 4-81. 


Figure 4-74. 
Large accumulation of 
debris trapped between 
house and dune walkover 
(Gulf Shores) 


Figure 4-75. 
Ground level photograph 
of debris shown in Figure 
4-74 (Gulf Shores) 



Figure 4-76. 
Marine pile debris 
washed into this house 
in the back bay. (Oriole 
Beach) 


Figure 4-77. 
Same marine pile as 
shown in Figure 4-76. 
Note the size and the 
length of the pile, which 
caused significant 
damage. (Oriole Beach) 



Figure 4-78. 
Boats and dock debris 
from a marina struck 
this pile-elevated 
building, deforming floor 
beams, breaking joist 
connections, and scarring 
pilings. (Big Lagoon) 


Figure 4-79. 
Typical view of destroyed 
docks contributing to 
floodborne debris (Big 
Lagoon) 



Figure 4-80. 
Small stones from a 
nearby revetment were 
likely propelled by 
waves into this northfacing 
sound side house, 
breaking windows and 
sliding glass doors. (Gulf 
Breeze) 


Figure 4-81. 
The small stone 
revetment contributed 
stones which were 
propelled by waves and 
struck the house, shown 
in Figure 4-80 (Gulf 
Breeze) 



4.2 Wind 

4.2.1 Wood Frames 

Most of the wood-frame buildings observed by the MAT were residen
tial 
buildings, both single family and low-rise condominiums. Overall, 
the predominant wind related damage to these types of buildings was 
not structural failure, but a failure of the building envelope, which 
will be discussed in Chapter 5. 

The wood-framed buildings observed by the MAT generally con
sisted 
of superstructures supported by the load-bearing exterior 
wood-framed walls. Building floors and roofs were supported by 
wood rafters or trusses and plywood decks. This type of construc
tion 
is known as light-frame construction and consists of nominal 
2-inch thick framing members spaced 12 inches to 24 inches to
gether 
and normally concealed by interior finish materials such as 
plaster, gypsum board, or wood paneling. Figure 4-82 shows a dia
gram 
of a typical residential building designed to meet high wind 
requirements. 

Wood is favored as both a structural material and a finish material 
for its economy, architectural flexibility, and aesthetics. Although it is 
rarely used today for commercial buildings, wood is a very favorable 
material to use for residential buildings. Most construction contrac
tors 
are familiar with wood as a building material. Small work crews 
can handle most wood members without special lifting equipment, 
cutting and fastening can be accomplished on site with hand held 
or portable power tools, and the skills needed for wood construc
tion 
are easily learned. The ease of construction and the flexibility of 
wood construction also lead to one of the major problems with it as 
a system: it can be assembled or modified in so many different ways. 
Thus, it becomes more difficult to standardize details and to ensure 
that the contractor follows the plans and specifications. For example, 
a structural steel frame can generally be assembled only in the way 
the engineer and fabricator planned it to be. Otherwise, the beams 
and columns simply will not fit, and field modifications are difficult. 
In the case of wood framed construction, a supply of the basic raw 
materials (lumber, plywood, nails) are delivered to the job site, and 
there are many ways they can be cut and assembled. Wood is also 
one of the most difficult materials for the designer to master because 
it is virtually the only building material that is natural rather than 
manmade, which entails a number of uncertainties. Wood structures 
may be the simplest to build, but they are among the most compli
cated 
to design. 



In the areas damaged by Hurricane Ivan, the MAT observed few houses 
new enough to have been built under the FBC 2001 or the IBC 2003. 
In addition, the actual wind pressures were below the code prescribed 
pressures; therefore, Ivan could not be considered a true code designlevel 
test. Therefore, it is difficult to evaluate the effect of new codes. 
It did appear that newer wood-frame houses generally performed well 
structurally. Efforts in the last 15 years to increase the quality of coastal 
construction, such as the SBC SSTD-10, Hurricane Resistant Residen
tial 
Construction Standard, and FEMA 55, Coastal Construction Manual, 
have been successful. Many newer houses observed by the MAT had 
significant damage due to storm surge below their elevated floors as 
expected, but showed little signs of structural damage due to wind or 
water (see Figure 4-83). 

Figure 4-82. 
Load path of a two-story 
building with a primary 
wood-framing system: 
walls, roof diaphragm, 
and a floor diaphragm 



The most common wind related structural failures observed in lightframed 
construction were roof framing failures. They were most 
commonly observed in older construction, but there were incidents 
of newer buildings experiencing the same damage. Insufficient attach
ment 
of roof sheathing panels to the supporting framing was the most 
common problem. The discovery of zones of high uplift pressures on 
the edges of roof surfaces through wind research over the last 25 years 
has caused newer codes to require much closer nail spacing in these 
zones. Older construction does not have these closer spacings in the 
sheathing nail patterns, and, thus, it is more susceptible to uplift dam
age. 
Once the sheathing attachments fail, a variety of other failure 
modes can happen. Attics that have been breached become pressur
ized 
and other structural elements may then become overstressed. 
This can lead to an unzipping effect of progressive failure where one 
failure leads to a series of subsequent failures. 

Figure 4-83. 
Storm surge damaged 
the lower portion of 
this house, but no wind 
damage was observed. 
(Gulf Shores) 



Another common failure point was wood-frame gable end walls. These 
are commonly under designed or improperly constructed. Often, a 
typical roof truss is the only support element behind the wall cover
ing 
of the gable as shown in Figure 4-85. Trusses are constructed with 
the weak dimension of the lumber turned normal to the plane of the 
truss. This means that when a typical truss is used alone as the wall 
framing for the gable end wall, the truss members must resist the walls 
wind forces in their weak direction. On larger buildings, the height of 
the gable end wall from the plane of the ceiling up to the peak of the 
gable is often taller than the story heights below. In these cases, even 
wall studs would have to be strengthened in order to be adequate. The 
truss members are typically not capable of carrying the bending forces 
in this manner. In cases where adequate wall stud framing is present 
in the gables, the problem is typically the absence of adequate bracing 
where the gable end wall sits on top of the wall below. This point is a 
hinge and must be braced by framing to transfer the wind loads into 
the lateral load resisting system. Figure 4-85 illustrates the arrange
ment 
of these structural members in typical light-frame construction. 
The framing shown in Figure 4-86 shows a truss resisting the wind loads 
with its weak axis. This was in an upscale house under construction, so 
the problem is still not being addressed in all cases. The condominium 
building shown in Figure 4-87 had no evidence of any bracing at the 
hinge point in its gable end wall framing. 

Figure 4-84. 
Progressive failure 
of wood roof framing 
(Perdido Key) 



The final observed failure mechanism in wood framed construction 
was the connections between the roof and wall members. Particularly 
evident in older buildings, the roof framing members were often inad
equately 
anchored to the wall framing. Whether caused by no anchors, 
inadequate anchors, or improperly installed anchors, the failure to 


Figure 4-85. 
Gable end wall framing 
diagram 


Figure 4-86. 
Roof truss with 2x4s 
oriented in the weak 
direction resisting the 
wind loads on a gable 
end wall (Ono Island) 



in Figures 4-88, 4-89, and 4-90, which suffered the total loss of the roof 
framing due to improper anchorage of the roof framing to the walls. 
complete the load paths, as illustrated in Figure 4-82, was the cause of 
damage. The MAT observed several buildings such as the ones shown 

The MAT observed several wood framed houses under construction 
at the time of the storm. It allowed an opportunity to observe current 
construction practices. Although in general the quality of residential 
construction has improved over the last 30 years, there were still exam
ples 
of poor practices being followed in new wood frame construction. 
Several improper installations of wood framing connectors were ob
served 
by the MAT. Several of these installations seemed to indicate a 
lack of understanding of the load path concepts illustrated in Figure 
4-82. The houses in Figures 4-91 and 4-92 had connectors in place, 
but they were the wrong type, in the wrong place, installed without 
the proper number of nails, or were already corroding. Figures 4-93 
and 4-94 show the wall studs between two garage doors in an upscale 
house under construction. The beams above the doors carry all the 
uplift of the roof framing above. However, note the lack of properly 
installed connectors to transfer these uplift forces from the beams to 
the wall studs and from the wall studs to the foundation. Progress is 
still needed in the design and construction of the load paths in wood 
framed buildings. 

Figure 4-87. 
Gable end wall failure 
due to lack of bracing at 
hinge point in wall (see 
arrow) (Perdido Key) 



Figure 4-88. 
Roof framing damage due 
to lack of connections 
from roof to wall (Orange 
Beach) 


Figure 4-89.
Roof framing damage due 
to lack of connections 
from roof to wall 
(Pensacola Beach) 



Figure 4-90. 
Roof framing damage due 
to lack of connections 
from roof to wall (Ono 
Island) 


Figure 4-91. 
Improper use of a 
wood truss press plate 
connector to substitute 
for stud hold-downs 
(Oriole Beach) 



Figure 4-92. 
Already corroded anchor 
bolt in new construction 
(Oriole Beach) 


Figure 4-93. 
Improper strapping 
(Ono Island) 



4.2.2 Concrete Buildings 

High-rise buildings, typically built of cast-in-place concrete, suffered 
little or no wind damage to the primary structural frame. The observed 
damage was to the building envelope. The building envelope perfor
mance 
is described later in Chapter 5. 

4.2.3 Commercial Buildings 

Masonry construction is commonly used for commercial buildings, 
such as shopping centers and office buildings. These buildings were 
supported on reinforced concrete foundations with shallow spread or 
deep foundation systems. Exterior load-bearing walls were constructed 
utilizing concrete masonry unit (CMU). The roof decks were observed 
to be supported by open web steel joists with metal deck. Very little 
structural damage was observed in this type of construction. Where 
structural damage was observed, it seemed to be isolated and a result 
of poor design or construction or a problem with a particular type of 
material installation such as shown in Figure 4-95. This building was in 
an area of relatively low wind speeds, yet suffered catastrophic failure 
while an adjacent retail center had only minor damage. 

Figure 4-94. 
Wall studs between 
garage doors with 
inadequate hold-downs 
(Ono Island) 



4.2.4 Pre-Engineered Metal Buildings 

A pre-engineered steel building system is generally the most economi
cal 
commercial building system and is normally utilized for purposes 
such as warehouses, storage facilities, airplane hangars, and other sim
ilar 
open interior uses. These buildings are easily recognized by their 
sheet metal siding, tapered rigid frames, and long spans with open 
spaces. Secondary structural members consisting of girt and purlins 
are installed to support the metal siding and roofing panels. 

As previously observed after other storms, of all the permanent struc
tural 
framing systems evaluated, the pre-engineered metal framed 
systems performed the poorest. Exterior walls consisting of thin sheet 
metal siding failed prematurely, resulting in a penetrated building 
envelope and causing failure of the main structural framing mem
bers. 
It appeared that the age of the buildings was a factor in their 
performance, either because of the aging and corrosion of the mate
rials 
or because of better design practice in more recent times. The 
MAT noted many newer metal buildings that performed adequately; 
however, all of the large boat storage facilities, new or old, were ob
served 
to have suffered significant damage that was out of scale for 
a wind event of this magnitude, as shown in Figures 4-96 and 4-97. 
Frequently, damage to boat storage facilities is caused by wind getting 

Figure 4-95. 
Metal roofing failure 
(Foley) 



into the building and resulting in internal and external pressure act
ing 
simultaneously on the building. Therefore, even at lower wind 
speeds, these forces will cause significant damage to these types of 
open structures. 

Figure 4-96. 
Heavily damaged preengineered 
boat storage 
building (Orange Beach) 


Figure 4-97. 
Heavily damaged preengineered 
boat storage 
building (Orange Beach) 



4.2.5 Accessory Structures 

Structural damage to accessory structures was observed by the MAT 
throughout the path of Hurricane Ivan. Carports, canopies, fences, 
and screen walls were all observed to sustain wind damage. Typical 
metal canopies between buildings on school campuses did not fare 
well, as shown in Figure 4-98. 


Figure 4-98. 
Collapsed metal canopy 
at a middle school 
(Pensacola) 



G 


C H A P T E R 5 

5-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

5 

Building 
Envelope Performance 

Good structural system performance is critical to avoiding injury to 
occupants and minimizing damage to a building and its contents. It 
does not, however, ensure occupant or building protection. Good 
performance of the building envelope is also necessary. The building 
envelope includes: 

 Sheathing on the underside of bottom-floor joists of elevated 
buildings, 

 Exterior doors, 

 Non-load-bearing walls, wall coverings, and soffits, 

 Roof coverings, 

 Windows, shutters, skylights, and 

 Exterior-mounted mechanical and electrical equipment. 

Historically, poor building envelope performance is the leading cause 
of damage to buildings and their contents in weak- to moderate-inten
sity 
hurricanes. Building structural capacities have improved because 
of stronger building codes and better enforcement, resulting in less 
structural damage overall from hurricanes such as Hurricane Ivan. 
As a result, the performance of the building envelope is becoming 
increasingly important. The following sections describe envelope 
performance during Hurricane Ivan as observed for residential, com
mercial, 
and critical and essential facilities. 



C H A P T E R 5 

BUILDING ENVELOPE PERFORMANCE 

5-2 

 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

5.1 Sheathing on the Underside of Elevated 
Buildings 

Sheathing was typically installed on the underside of bottomfloor 
joists on elevated buildings. Besides protecting batt 
insulation that is placed between joists, sheathing can also pro
tect 
electrical and plumbing lines from floodborne debris. A variety of 
sheathing materials were observed. Vinyl siding and plywood were the 
most common, but gypsum board was observed on three buildings, 
and corrugated metal was observed on one building. The majority of 
the buildings with vinyl experienced sheathing loss (Figure 5-1). For 
further discussion of vinyl siding, see Section 5.3.2. 

All of the buildings with gypsum board experienced sheathing loss 
(Figure 5-2). One of these buildings was a large apartment or con
dominium 
 essentially all of the gypsum board was torn away (the 
gypsum board typically pulled over the nail heads). 


Figure 5-1. 
Loss of vinyl siding 
panels from the 
underside of an elevated 
residence in Gulf Shores 
(Laguna Key) 



BUILDING ENVELOPE PERFORMANCE 

The plywood panels typically performed well, but some losses were 
experienced (Figure 5-3). Nails were typically used to attach the sheath
ing. 
Fastener corrosion was common and some of the nail heads were 
totally corroded away. Fastener spacing along the joists was often about 
12 inches on center. Although the long edge of the sheathing typically 
occurred over blocking, fastener spacing along the long edge was of
ten 
only about 16 inches on center. 

Figure 5-2. 
Loss of gypsum board 
from the underside of an 
elevated residence in Gulf 
Shores (Laguna Key) 


Figure 5-3. 
Loss of plywood from the 
underside of an elevated 
residence in Gulf Shores 
(West Beach) 



Fast-moving floodwater and peaking waves likely caused some of 
the sheathing loss, including complete loss of gypsum board at one 
building. Gouging of sheathing (including penetration of plywood) 
by floodborne debris was also observed. However, the majority of 
the sheathing loss appeared to be caused by wind accelerating as it 
passed beneath the elevated building. ASCE 7, FBC, and IBC do not 
provide guidance on determining design wind loads on sheathing on 
the underside of elevated buildings. Hence, professional judgment in 
specifying attachment is needed. 

5.2 Doors 

Failure of an exterior door has two important effects. First, fail
ure 
can cause a rapid increase in internal pressure, which may 
lead to exterior wall, roof, interior partition, ceiling, or struc
tural 
failure. Second, wind can drive rainwater through the opening, 
causing damage to interior contents and finishes, and lead to the de
velopment 
of mold. The essential elements of good high-wind door 
performance include product testing to ensure sufficient factored 
strength to resist design wind loads (both static and cyclic loading); 
suitable anchoring of the door frame to the building; proper flashing, 
sealants, tracks, and drainage to minimize water intrusion into wall 
cavities or into occupied space; and, for glazed openings, the use of 
laminated glass or shutters to protect against windborne debris dam
age, 
as discussed in Section 5.5. 

5.2.1 Personnel Door Damage 

Personnel door damage was observed on a limited number of build
ings. 
Observed damage included broken window panes (caused 
by windborne debris) and door frames that disengaged from the 
building (likely caused by inadequate fastening to the building), as 
illustrated by Figures 5-4, and 5-5. The sliding glass door frame in Fig
ure 
5-5 had recently been installed in an existing building. The door 
assembly was rated for a load of +/- 50 pounds per square feet (psf). 
The applied loads were well below 50 psf. The frame was attached 
with nails spaced at 4 3/8 inches on center through a vinyl nailing 
flange. Although the edge distance was limited, the typical failure 
mode was nail pull-out. 



Figure 5-4. 
Tempered glass door 
broken by debris from 
a mortar-set tile roof 
(Pensacola) 


Figure 5-5. 
Sliding glass door frame blown from the wall 



5.2.2 Garage Door Damage 

Many damaged garage doors were observed in coastal areas. The ma
jority 
of the doors were damaged by floodwater. Wind-induced damage 
was minimal. (For observations and discussion of garage door wind 
damage caused by Hurricane Charley, see FEMA 488, Mitigation As
sessment 
Team Report, Hurricane Charley in Florida.) Figure 5-6 shows a 
combined garage door and wall covering failure. Where breakaway 
walls are installed, collapse of the garage doors is intended. 


Figure 5-6. 
Floodwater collapsed the 
garage door at the left 
end of this residence. 
(Laguna Key) 



5.2.3 Rolling and Sectional Door Damage 

A limited amount of wind damage to rolling and sectional doors (e.g., 
service garage doors and loading dock doors) was observed, includ
ing 
damage to sectional doors at a fire station. (For observations and 
discussion of rolling and sectional door damage caused by Hurricane 
Charley, see FEMA 488, Mitigation Assessment Team Report, Hurricane 
Charley in Florida.) 

5.3 Non-Load-Bearing Walls, Wall Coverings, 
and Soffits 

Hurricane Ivan caused damage to several non-load-bearing walls, 
wall coverings, and soffits. Non-load-bearing walls included 
exterior insulation finish systems (EIFS) and stucco. Wall cover
ings 
included brick, metal panels, vinyl, and wood. Vinyl was typically 
used for soffits. The following factors are essential to good high-wind 
non-load-bearing wall, wall covering, and soffit performance: prod
uct 
testing to ensure sufficient factored strength to resist design wind 
loads; suitable anchoring of the wall, wall coverings, and soffits to the 
building; use of moisture barriers (e.g., asphalt saturated felt or house
wrap) 
where appropriate; and proper flashing, sealants, and drainage 
to minimize water intrusion into wall cavities or into occupied space. 

Note: For observations and discussion of breakaway walls, see Subsec
tion 
4.1.3.3. 

5.3.1 Non-Load-Bearing Walls 

Non-load-bearing walls that were investigated included EIFS over studs 
and stucco over studs. EIFS and stucco wall coverings over bearing walls 
were also investigated and are included in this section. A large number 
of EIFS failures and several stucco failures were observed. With loss of 
the EIFS or stucco coverings, wind-driven rain was often able to enter 
the wall cavity or the building itself and initiate mold growth. EIFS 
and stucco coverings that became windborne debris were capable of 
breaking unprotected windows. Figures 5-7 and 5-8 show typical EIFS 
and Stucco assemblies. 



Figure 5-7. 
Typical EIFS assembly 



EIFS 

Fast-moving floodwater initiated damage at the residence shown in Fig
ure 
5-6, but a projecting wall band limited progressive peeling of the 
EIFS in the vertical direction. The synthetic stucco was applied over 
a cementitious board that was installed over housewrap. Floodwater 
broke away the wall and initiated progressive peeling of the synthetic 
stucco and cementitious board. However, the presence of the white 
band that projected about 2 inches out from the face of the wall inhib
ited 
vertical peeling. 

At the residence shown in Figure 5-9, there was no projecting band, 
reveal, or other detailing to limit vertical peeling. The synthetic stuc
co 
was applied over polyisocyanurate insulation that was installed 
over asphalt saturated felt. Floodwater broke away the wall and initi
ated 
progressive peeling of the synthetic stucco and a portion of the 


Figure 5-8. 
Typical stucco assembly 



ical fasteners. The fasteners were poorly applied. There were fewer 
fasteners near the bottom edge than there were in the field rows. The 
end of the boards, fasteners were installed through the board joint, so 
that one fastener would hold the edge of two boards (see red circle 
should have been inward of the joint. If the fasteners had been prop 
polyisocyanurate. The facer on the polyisocyanurate peeled off with 
the synthetic stucco. The polyisocyanurate was attached with mechan
fasteners 
were placed too close to the long edge of the board. At the 
in Figure 5-9). Rather than placing fasteners at the joints, fasteners 
erly 
located, several more fasteners would have been required. 

Figures 5-10 through 5-12 show dry rotted studs and sheathing, in
dicating 
long-term moisture intrusion behind the molded expanded 
polystyrene (MEPS) insulation. Both of these buildings used a barrier 
EIFS design, rather than the newer drainable EIFS design. (No drain
able 
EIFS designs were observed.) At the condominium in Figure 5-10, 
the synthetic stucco was installed over MEPS over gypsum board over 
wood studs. Essentially all of the gypsum board blew off (the boards 
typically pulled over the fasteners). Some of the gypsum board on the 
interior side of the studs was also blown off. Note the missing studs on 
the second level at the left. Stud failure may have initiated the EIFS 
blow-off. Note the metal diagonal stud bracing straps. Two of the win
dows 
were broken by debris. 


Figure 5-9. 
Vertical peeling on a 
home in Gulf Shores due 
to lack of a projecting 
band or reveal after the 
breakaway wall failed 
(Laguna Key) 



Figure 5-11 is another view of the condominium complex shown in 
Figure 5-10. The studs were severely rotted and the metal connectors 
were very corroded. 

Figure 5-10. 
All gypsum board blown 
off and two windows 
broken by debris. Note 
the missing studs. 
(Pensacola Beach) 


Figure 5-11. 
Severely deteriorated 
studs and corroded 
metal connectors 



Figure 5-13 shows common planes of failure of EIFS installed over wood 
and metal studs. Typically, separation of the synthetic stucco from the 
MEPS is likely a secondary failure plane. Initial failure is likely caused 
by detachment of the MEPS from the gypsum board, or detachment of 
the gypsum board from the studs. When the MEPS detaches from the 
gypsum board, the gypsum board can suffer strength reduction due to 
wetting from the wind-driven rain, and it, too, will often then blow off 
during a hurricane. 

On the building shown in Figure 5-13, wood studs were used in the 
center section and metal studs were used on adjacent sections. In the 
center area, gypsum board detached from the studs. Near the bottom 
of the wall and above the MEPS, the gypsum board is still attached, 
but the MEPS separated from the gypsum board. At the white area, 
the synthetic stucco separated from the MEPS. Note the attachment 
of the MEPS to the gypsum board. Adhesive is nearly continuous at 
the perimeter of the MEPS boards, and four vertical lines of adhesive 
occur in the field of the boards (the vertical lines are of different 
lengths and none of them extend all of the way to the board edges). 
Adhesive should have been continuously applied throughout the en
tire 
board area. 

Figure 5-12. 
Blown off EIFS revealed 
severely rotted oriented 
strand board (OSB) due 
to water infiltration 
at windows and wall 
penetrations. Roof 
decking blown off of a 
building with a 5-V crimp 
metal panel roof. 



Figure 5-14 shows extensive damage to non-load-bearing EIFS walls 
on a multi-story building. Hurricane Ivan inflicted large areas of EIFS 
failure on many multi-story buildings. 


Figure 5-13. 
Loss of EIFS on a commercial building 


Figure 5-14. 
Multi-story building 
showing severe EIFS 
damage. The gypsum 
board typically detached 
from the studs. See 
Figure 7-11 for a closeup 
of the circled area. 



Figure 5-15 shows extensive damage to non-load-bearing EIFS pent
house 
walls on a mid-rise medical office building (MOB) at a hospital. 
After failure of the EIFS, rainwater was able to blow into the elevator 
penthouse and damage the elevator controls. Loss of vertical transporta
tion 
in mid- and high-rise buildings can severely interrupt functionality. 

Figures 5-16 through 5-19 show EIFS damage and very extensive sec
ondary 
damages caused by EIFS failures at a hospital complex. Because 
of rapid emergency response by construction crews, the hospital re
mained 
functional. However, the damage was very costly and created 
hardships on hospital staff. 

EIFS debris from the hospital shown in Figure 5-16 broke numerous 
windows in the MOB and several of the windows in the connecting 
walkway between the MOB and hospital. The projection from the 
right rear of the MOB is an elevator. The side walls of the elevator 
shaft were EIFS and windows were located in the front wall. Several 
windows were broken by EIFS debris. The EIFS (including the gypsum 
board substrate) blew off the metal studs in several areas. Water infil
tration 
damaged the elevator controls. Several people were trapped in 
the elevator during the hurricane. Fortunately, the MOB had another 
bank of elevators, so vertical transportation was still possible, though 
handicapped by loss of this elevator. 

EIFS (including the gypsum board) also blew off the MOB stair tower 
walls. Some of the gypsum board on the interior side of the studs col
lapsed 
into the stairway, thus trapping a maintenance worker who had 
gone to the mechanical penthouse during the hurricane. 


Figure 5-15. 
The gypsum board 
detached from the 
studs at the penthouse. 
Rainwater infiltration 
damaged the elevator 
controls. (Pensacola) 



Glass shards punctured the one-story roof (Figure 5-17) at the right 
of the MOB (red arrow in Figure 5-16), which housed the urgent care 
facility and regional dialysis unit. However, by quickly performing 
emergency roof repairs and cleaning up the interior, the dialysis unit 
was non-operational for only one day. The roof over the dialysis unit 
was a ballasted ethylene propylene diene monomer (EPDM) mem
brane 
roof. The roof deck was a concrete or lightweight insulating 
concrete topping over metal decking. The deck was effective in mini
mizing 
water infiltration into the facility. (Note: At the time the photo 
in Figure 5-17 was taken, the ballast had been repositioned into rows 
in preparation for removal.) 


Figure 5-16. 
EIFS blew off the 
hospital building in the 
background (see red 
circle and Figures 5-18 
and 6-2). EIFS debris 
broke numerous windows 
in the MOB in the 
foreground. (Pensacola) 


Figure 5-17. 
Looking down at the onestory 
roof to the right of 
the MOB in Figure 5-16. 
The small dark areas 
are locations where 
emergency patches had 
been placed to repair 
punctures from falling 
glass shards. 



The hospitals original concrete wall panels had been furred with met
al 
hat channels and covered with EIFS (Figure 5-18). The majority of 
the gypsum board panels had blown off. The boards pulled over the 
screw heads. The screws and hat channels were moderately corroded. 

Figure 5-19 shows a close-up of the EIFS spandrel damage and glazing 
damage at the MOB. Although the majority of the glazing damage was 
caused by EIFS debris, some window frames were reportedly blown 
out. These failures were likely due to development of high internal 
pressure after windows on windward surfaces were broken by debris, 
combined with suction pressure on the exterior surface of windows on 
the leeward side of the building. 


Figure 5-18. 
Close-up of the damaged 
EIFS at the hospital 



Most of the EIFS damage caused by Hurricane Ivan occurred over met
al 
or wood stud walls. However, some damaged EIFS occurred over 
concrete walls, as shown in Figures 5-20 and 5-21. 

Figure 5-19. 
Wood studs and 
gypsum board had been 
temporarily installed 
after the hurricane to 
prevent patients from 
inadvertently falling out 
of the MOB. 


Figure 5-20. 
Hospital with EIFS blown 
off a cast-in-place 
concrete wall. Note 
the damaged rooftop 
ductwork. (Pensacola) 



For many buildings, the ramification of damage to EIFS assemblies 
was significant. With several of these failures, the cost of repairing the 
EIFS was minor in comparison to the cost of damage to other building 
components; the cost of rainwater damage and mold remediation to 
building interiors, furnishings, and equipment; and the cost due to loss 
of use of the building while repairs where made. EIFS installed over 
wood or metal studs is susceptible to disproportional failure, wherein 
a relatively minor deficiency (such as an inadequate number of screws 
to attach gypsum board) results in loss of the exterior wall, as shown in 
Figure 5-14. Typical EIFS assemblies (i.e., studs, gypsum board, insu
lation, 
and synthetic stucco) lack redundancy to protect the building 
from catastrophic wind and rainwater infiltration when wind initiates 
failure somewhere within the assembly. 

The EIFS damage was primarily related to application and/or design 
deficiencies. Lack of design guides likely contributed to the design 
problems. The test method used to determine wind resistance of EIFS 
assemblies may have also contributed to some of the damage. These 
issues are discussed below: 

 Application: In all cases that were investigated wherein adhered 
insulation boards separated from the gypsum board or concrete 
substrate, there was significant lack of adhesive. EIFS manufacturers 
currently specify that the entire surface of the insulation boards is 
to be covered with adhesive applied with a notched trowel. 

Figure 5-21. 
Close-up of Figure 5-20. 
The light colored round 
marks indicate where 
adhesive had been 
applied. The adhesive 
did not make a good 
bond with the concrete 
and it should have been 
continuously applied. 



In all cases that were investigated wherein gypsum board was 
mechanically attached, the fasteners were too far apart. Spacings 
of 12 inches on center were measured. However, for the Pensacola 
area, the spacings typically should have been a maximum of 6 
inches on center for heights up to 30 feet.1 For taller buildings, 
and buildings located near or at the coast, closer spacings would 
be necessary. Because contract documents were not available, it is 
unknown whether the spacing deficiencies were due to design or 
workmanship errors. 

 Design: Deficiencies included lack of provisions to prevent 
breakaway wall failure, beneath coastal elevated buildings, from 
unnecessarily propagating vertically. 

 Testing: The EIFS industry uses American Society for Testing 
and Materials (ASTM) E 330 to evaluate wind resistance of EIFS 
assemblies. Load is applied to the specimen for 10 seconds before 
being released. The load is then increased and applied for another 
10 seconds, then released. This process is repeated until failure 
occurs. While none of the investigated failures were specifically 
attributed to deficiencies in the test method, the test methods 
load duration of only 10 seconds appears to be inadequate. ASTM 
E 1592 (a test for metal roof and siding panels) specifies that each 
load increment be maintained for a minimum of 60 seconds and 
until the gauges indicate no further increase in deflection. The 
load duration and deflection criteria in E 1592 appear prudent 
for EIFS. 

 Design guides: The EIFS Industry Members Association (EIMA) 
has a Guide to EIFS Construction, but the Guide is silent on windrelated 
issues. Manufacturers of EIFS materials have specifications, 
but they are typically lacking in wind-related criteria. For example, 
to determine fastener spacing for gypsum board (which is a very 
critical element in the load path), designers are referred to gypsum 
sheathing manufacturers. Also, ultimate load values based on 
ASTM E 330 typically are given, but guidance on magnitude of the 
safety factor is often not given to the specifier. 

 An EIFS wind design guide is needed to address the various design 
issues associated with successful performance of EIFS. It should 
include criteria related to studs and their attachment to the building, 
criteria related to attachment of sheathing and insulation boards, 
safety factor selection, and key elements of field observation. 

1 Based on an ICC Evaluation Report, assuming a 16 inches on center stud spacing. 



 Codes: Neither the FBC nor IBC have specific wind-related criteria 
pertaining to EIFS. The International Code Councils Evaluation 
Service does have the AC24 Interim Criteria for Exterior Insulation 
and Finish System for evaluating EIFS. AC24 uses ASTM E 330 
for the wind resistance evaluation. AC24 requires at least six load 
increments with a 10 second load duration for each increment. 
AC24 also requires a minimum safety factor of 3. (Note: The 
Standard Building Code Congress Internationals Evaluation 
Service previously used a safety factor of two. Hence, systems 
designed in accordance with that criteria would be much weaker 
than systems designed in accordance with the ICC criteria.) 

Stucco 

A few buildings with traditional stucco walls were observed. Figures 3-21, 
5-22 and 5-23 show significant damage to non-load-bearing stucco walls 
on two mid-rise condominiums. In several areas, the metal stud system 
failed; in other areas, the gypsum sheathing blew off the studs; and in 
other areas, the metal lath and stucco blew off the gypsum. It appeared 
that failure of the stud track connections initiated most of these failures. 
Figure 5-23 illustrates a serious potential risk to residents. 


Figure 5-22. 
Failure of non-loadbearing 
stucco wall 
(close-up of Figure 3-21) 
(Perdido Key) 



On a few buildings, stucco was applied over plywood over wood studs. 
At the residence shown in Figure 5-24, the plywood was severely rot
ted. 
Figure 5-25 shows failure of stucco applied over cast-in-place 
concrete. Similar failures were observed in Puerto Rico following 
Hurricane Georges (see FEMA 339, Hurricane Georges in Puerto Rico, 
March 1999). 

Figure 5-23. 
Close-up of Figure 3-21. 
With complete loss of 
the walls, the residents 
could have inadvertently 
fallen from the building. 
Although not shown in 
this photograph, several 
of the balcony railings 
had blown away. 
(Perdido Key) 



Figure 5-24. 
Six-year old, stucco-sheathed residence with 
severely rotted plywood (Pensacola Beach) 


Figure 5-25. 
At the end wall of the 
center building, stucco 
blew off the concrete 
substrate. Some of the 
chimney walls made 
of stucco over gypsum 
board over wood studs 
were also blown away. 



As with EIFS assemblies, attention to attachment of studs to the build
ing, 
attachment of gypsum board to the studs, and attachment of the 
lath are critical in achieving good wind performance. 

5.3.2 Wall Coverings and Soffits 

Wall coverings that were investigated included brick veneer, metal 
panels, vinyl siding (and soffits), and wood siding. EIFS and stucco 
wall coverings were also observed; these were discussed in the previ
ous 
section. In some instances, with loss of the coverings, wind-driven 
rain was able to enter the wall cavity and initiate mold growth. Some of 
the blown-off coverings became windborne debris that was capable of 
breaking unprotected glazing. 

Brick 

Several buildings with brick veneer were observed. Figure 5-26 shows 
failure on an office building. The majority of the corrugated ties re
mained 
attached to the steel studs. The ties were spaced approximately 
18 inches on center vertically and 16 inches on center horizontally. 
According to another investigation team that had access to the build
ing, 
the primary mode of failure was tension failure of the ties due 
to severe corrosion. Based on the Brick Industry Associations (BIA) 
Technical Notes 28B  Brick Veneer/Steel Stud Walls, corrugated ties are 
not permitted when brick veneer is supported by steel stud backing. 
In part, this provision is based on the greater corrosion susceptibility 
of corrugated ties versus round ties (i.e., water is more likely to remain 
for a longer period of time on the flat surface of corrugated ties). The 
tie spacings were closer than the maximum recommended in Techni
cal 
Notes 28B, which is 18 inches on center vertically and 32 inches on 
center horizontally, yet still failed due to corrosion. 



Figure 5-27 shows failure at an older wood-framed residence. There 
were several failure modes: 

 Several ties had never been embedded into the mortar joints 

 The tie nails pulled from the studs 

 Lack of bonding between mortar and brick 

 Tie tension failure due to severe corrosion (this occurred on a tie 
embedded into the CMU foundation wall that extended about 4 
feet above grade) 

Figure 5-26. 
Brick veneer failure on an office building 
(Pensacola). 



The MAT observed another house where a large number of the cor
rugated 
ties had never been embedded into the mortar joints. In areas 
where ties had been embedded, the smooth-shank nails pulled from 
the studs. 

At a house under construction, ties had been embedded into the CMU 
foundation wall that extended a few feet above grade  the brick had 
not been installed. The ties were spaced at 16" on center vertically. At 
one area, the horizontal spacings were 22", 30", 20 ", and 26 ". BIA 
Technical Notes 44b  Wall Ties for Brick Masonry specifies a maximum 
vertical and horizontal spacing of 18" and 32" respectively. 

For the building shown in Figure 5-26, because the contract documents 
were not available, it is unknown whether use of the incorrect ties was 
a design or application error. For the residence shown in Figure 5-27, 
failure to embed the ties into the mortar joints was a major workman
ship 
error. Failure to embed ties was documented in a Hurricane Opal 
report by The Masonry Society (An Investigation of the Effects of Hurri
cane 
Opal on Masonry, The Masonry Society, July 1996). Opal struck the 
Florida Panhandle in 1995. 


Figure 5-27. 
Wood-frame residence 
has several corrugated 
ties that were never 
embedded into the 
mortar joints (see inset) 



The Masonry Society deployed a team to assess performance of rein
forced 
and unreinforced masonry and brick veneer. The teams report 
included limited information on performance of brick veneer. The re
port 
recommended a close review of all brick veneer design, but the 
report did not provide specific guidance.2 

Metal Panels 

The MAT observed a limited number of metal wall panel failures. Fail
ures 
were observed at two schools (Figures 3-25 and 5-28). Both schools 
used similar panels. The panels were attached with concealed screws. 
The screws were installed through concealed portions of the standing 
seams. The failures occurred due to unlatching of the seams. 

Another wall panel failure was observed at a hangar (Figure 5-29). 
New panels had been installed over older panels. In one area, the top 
leg of a channel had been screwed at 63" and 43" to the old panels. 
The bottom leg had been screwed at 21" and 43". The new panels 
were attached with clips that were screwed at 12" on center to the hat 
channels. There were two screws per clip. The connections of the new 
panels to the hat channels were much stronger than the connections 
between the hat channels and old panels. 


Figure 5-28. 
These panels were 
attached with concealed 
fasteners. They unlatched 
at the standing seams. 
In addition to generating 
windborne debris, 
loss of panels allowed 
significant rainwater 
infiltration. 

2 The Masonry Society, Hurricane Ivan Investigation Report, April 1, 2005. 



Vinyl Siding and Soffits 

Vinyl was the predominant siding and soffit material observed on resi
dences 
in the areas investigated by the MAT. Performance of the siding 
and soffits was very poor (see Figure 5-30). There were numerous sig
nificant 
failures throughout the areas observed by the MAT. Failures 
were observed on both new and old buildings. When vinyl siding was 
blown off, the underlayment (either asphalt-saturated felt or house
wrap) 
was also often blown away, as shown in Figure 5-31. With loss of 
the siding and underlayment, wind-driven rainwater was then able to 
enter the wall cavity, causing water damage and initiating mold growth. 
Vinyl sidings that became windborne debris were capable of breaking 
unprotected glazing. 

Figure 5-29. 
The green fascia panels 
had been installed over 
a previous metal panel 
system. The original 
panels remained in 
place, but the newer 
panels blew off due to 
inadequate hat channel 
attachment. (Pensacola) 



Vinyl siding manufactured for high-wind areas is available, but was ob
served 
on only one building (Figure 5-31). With high-wind siding, the 
nailing flange is folded over, so there is a double thickness of vinyl at 
the fastener points (Figure 5-32). 

Figure 5-30. 
Loss of vinyl soffits was common. Loss often led to 
water penetration into the building, with damage 
to attic and wall insulation, gypsum board ceilings, 
and building contents. (Orange Beach) 



Vinyl siding that was blown off typically tore around the fastener 
points. Staples were used to attach the siding on some residences, 
but large headed nails were typically used. The 2003 IBC requires a 
maximum fastener spacing of 16". ASTM D 4756, Standard Practice 
for Installation of Rigid Poly (Vinyl Chloride) (PVC) Siding and Soffit also 
specifies a maximum spacing of 16". The 2001 FBC does not specify 
a maximum limit. 

Figure 5-31. 
Although a highwind 
panel was used, 
extensive loss of 
siding and housewrap 
underlayment occurred. 
See Figure 5-32. 


Figure 5-32. 
A double thickness of 
vinyl occurred at the 
nailing flange. This 
provided greater fastener 
pull-over resistance. 
However, many of the 
panels pulled over the 
nail heads. 



Thirty-four fastener spacing dimensions were measured on eight resi
dences. 
The spacings on each of the residences were quite variable. 
On six of the eight residences, one or more spacings exceeded 16". 
The residence with the most excessive measurements had spacings of 
27 ", 25", 25" and 29". At the residence shown in Figure 5-31 with the 
high-wind siding, the greatest spacing was 21". However, of the eleven 
measurements taken at that residence, eight were 14" or less. 

ASTM D 4756 specifies that the fasteners are to be driven into framing 
or furring members, rather than just into plywood or oriented-strand 
board (OSB). Most of the fasteners that were investigated by the MAT 
were just driven into sheathing. Although this practice did not comply 
with ASTM D 4756, no fastener pull-out problems were observed. 

In some cases, the MAT believes that the blow-off was triggered by un
latching 
of the buttlock, which is the bottom portion of the panel (see 
Figures 5-33 and 5-68). Once the panel unlatches from the retainer 
slot just below the nailing flange, the panel is free to rotate outward 
where it can be caught by the wind and blow off. The magnitude of 
the unlatching issue, compared to the strength of the nailing flange 
and fastener spacing, is unknown. When unlatched, panels are very 
susceptible to blow-off. 

Underlayment had not been installed at all on some residences (see 
Figure 4-17). Not installing underlayment is a poor practice because 
vinyl siding (like many other types of wall coverings) does not prevent 
rainwater from getting behind the siding. Underlayment should al
ways 
be installed to intercept the leakage and drain it out of the wall. 



Figure 5-33. 
When a panel becomes 
unlatched, it becomes 
very susceptible to 
blow-off. 



Neither the 2001 FBC nor ASTM D 4756 currently require 
underlayment underneath vinyl siding. The 2003 IBC does require 
underlayment. 

Some vinyl siding was damaged by windborne debris, and some vi
nyl 
soffit damage was observed (see Figure 5-30). Where soffits were 
blown away, a significant amount of water was often driven into the at
tics 
and ultimately into living spaces. Debris damage and soffit failure 
was more commonly observed by the MAT that investigated Hurricane 
Charley. Further discussion and analysis of debris damage and soffits 
are presented in FEMA 488, Hurricane Charley in Florida. 

The vinyl siding damage was related to application deficiencies (i.e., 
excessive spacing between fasteners). However, other factors also like
ly 
contributed to the damage. In most of the failures investigated by 
the MAT, it did not appear that the siding was any stronger than that 
used in areas of the United States that have a 90-mph basic wind speed. 
There also appear to be weaknesses in the ASTM product and test
ing 
standards. ASTM D 3679, Standard Specification for Rigid Poly (Vinyl 
Chloride) (PVC) Siding, specifies a 1.5 safety factor. Considering the sim
plicity 
of the test method and the number of wind failures, the 1.5 
factor appears too low. 

ASTM D 5206 Standard Test Method for Windload Resistance of Rigid Poly 
(Vinyl Chloride) (PVC) Siding requires holding the test load for only 30 
seconds before increasing to the next pressure level. ASTM E 1592 (a 
test for metal roof and siding panels) specifies that each load incre
ment 
be maintained for a minimum of 60 seconds and until the gauges 
indicate no further increase in deflection. The load duration and de
flection 
criteria in E 1592 appear prudent for vinyl siding. Another 
weakness is that D 5206 is a static test. Static tests can over-estimate the 
wind resistance of systems that experience significant deformations 
and/or fatigue failure. Considering the flexible nature of vinyl siding 
and the dynamic nature of wind loading, a dynamic test appears to be 
prudent for vinyl siding. 

Wood Siding 

Several residences had wood siding, either textured plywood or 
boards. The wind performance of wood siding was typically very good. 
Although there were several instances of failure of wood-framed exte
rior 
walls, such as that shown in Figure 5-34, loss of just the plywood 
wall siding was very rare (see Figure 5-35). Loss of board siding was 
also rare. There were instances where failure of other elements, such 
as decks or walls resulted in some progressive failure of board siding. 



However, failure propagation was typically quite limited. An attribute 
of board siding is that it is typically very resistant to progressive fail
ure, 
as shown in Figure 5-34. Large portions of the exterior wall failed 
in two areas, but loss of siding beyond the failed wall area was mini
mal. 
Had the building in Figure 5-34 been covered with vinyl siding 
or EIFS, the vinyl or EIFS failure would have undoubtedly significantly 
propagated beyond the wall failures. 

The generally good performance of plywood and board siding is likely 
due to their inherent strength and stiffness. Low-energy missiles can eas
ily 
penetrate vinyl siding and EIFS, but wood siding is quite resistant. 


Figure 5-34. 
Failure of wood framed 
exterior walls covered 
with wood siding 


Figure 5-35. 
Vinyl siding had been 
installed over textured 
plywood siding. Although 
a large area of vinyl blew 
off, the plywood was 
not damaged, leaving 
the building envelope 
intact. This scenario 
was observed on several 
buildings. 



5.4 Roof Systems 

H istorically, damage to roof coverings and rooftop equipment is 
the leading cause of building performance problems during 
hurricanes. In the rains accompanying a hurricane, rainwater 
entering a building through damaged roofs can cause major dam
age 
to the contents and interior. Unless quick action is taken to dry 
a building, mold bloom can quickly occur in the hot, humid south
ern 
climate. Drying of buildings was hampered after Hurricane Ivan 
by the lack of electrical power to run fans and dehumidifiers. These 
damages are frequently more costly than the roof damages them
selves. 
Rainwater leakage can also disrupt the functioning of critical 
and essential facilities and weaken ceilings and cause them to col
lapse. 
Although ceiling collapse is unlikely to result in death, it can 
cause injury to occupants and further frighten them as they ride out 
the hurricane. 

5.4.1 Asphalt Shingles 

The observations of the Hurricane Ivan MAT were similar and con
sistent 
with the observations of the Hurricane Charley MAT. Failures 
of hip/ridge trim shingles, and failures along the eaves and rakes 
were common. Enhancement of hip/ridge, eave, and rake details, 
and enhanced underlayment protection such as that shown in Hur
ricane 
Recovery Advisory Numbers 1 and 2 (see Appendix D) were 
not observed. Incorrect execution of the starter course was a com
mon 
problem (Figure 7-12). Fastener mislocation was also common. 
Observed fasteners were typically located too high and too close or 
too far away from the ends of the shingles. Use of four nails per shin
gle 
rather than six was frequently observed, including on the school 
shown in Figure 6-8. 

One notable difference between the Hurricane Charley and Ivan 
observations was shingle damage associated with raking. With the 
raking installation method, shingles are installed from eave to ridge 
in bands about 6-feet wide. Where the bands join one another, at ev
ery 
other course, a shingle from the previous row needs to be lifted 
up to install the end nail of the new band shingle. Sometimes install
ers 
do not install the end nail  in these applications, the shingles 
are vulnerable to unzipping at the band lines, as shown in Figure 5- 
36. The National Roofing Contractors Association recommends that 
the raking method not be used. Rather, starting at the eave, shingles 
should be laid one course at a time from rake to rake. 



A limited number of ridge vents were investigated. Figure 5-37 shows 
a metal ridge vent failure. Where the vent lifted, it was attached with 
roofing nails spaced at 22 " and 19" on one side of the ridge, and 
21" and 17 " on the other side. In an area where the vent was not 
blown off, the nails were spaced at 18 ", 10", 11 " and 11 ". The 
nails were moderately corroded. This residence was not originally con
structed 
with a continuous ridge vent. The slot through the plywood 
roof decking was cut during a reroofing project. When the slot was cut, 
the blade of the power saw was not adjusted to suit the deck thickness. 
As a result, a deep cut was made through the trusses and metal connec
tors 
(Figure 5-37 inset). 

Although the exposed opening through the roof at the damaged ridge 
vent was small, a substantial amount of water entered the residence 
during the storm. At the time of the investigation, the roof had been 
open for 15 days. 

A few tabs blew off the roof shown in Figure 5-37. Where the tabs blew 
off, the fasteners were incorrectly located, and a nail was missing at one 
of the shingles (Figure 5-38). However, tab blow-off occurred because 
the tabs had not sealed rather than because of nailing problems. 

Figure 5-36. 
The vertical lines of 
missing shingle tabs are 
indicative of installation 
via the raking method. 
When raked, end nails are 
frequently not installed. 



Figure 5-37. 
Partial blow-off of ridge vent. When the 
plywood was slotted, the trusses and truss 
plates were cut. 


Figure 5-38. 
Missing tabs. All of the 
nails were installed too 
high, and two of the end 
nails were too far from 
the end. An end nail had 
not been installed at the 
lower tab. 



5.4.2 Tile 

Clay and concrete tiles were observed, with concrete being the most 
common. A variety of tile profiles (e.g., S-tile and flat) were observed, 
but no significant wind performance differences were attributed to 
profile. Mortar-set, mechanically attached, and foam-set (adhesive-set) 
attachment methods for tile roofs were observed during the assessment. 
The observations of the Hurricane Ivan MAT were similar and consis
tent 
with the observations of the Hurricane Charley MAT. However, tile 
roofs were more common in the areas impacted by Hurricane Charley. 
Observations from Hurricane Charley, Frances, and Ivan were the basis 
for Hurricane Recovery Advisory Number 3 (see Appendix D). 

Figure 5-39 illustrates typical tile damage in areas that experienced 
modest wind speeds. Eave, hip, ridge, and rake tile failures were com
mon. 
In areas with higher wind speeds or on higher elevation roofs, 
large areas of tiles were blown away, such as shown in Figure 5-40, 5-43, 
and 5-46. 

Mortar-Set Tile Roofs 

As observed after Hurricane Charley and Frances, mortar-set tile roofs 
typically experienced larger blow-off areas than did any of the other 
attachment methods. 


Figure 5-39. 
This roof is indicative 
of tile failure at modest 
wind speeds, wherein 
failure of eave, hip, and 
rake tiles were most 
common. 



Mechanically Attached Tile Roofs 

Figure 5-40 shows a direct-to-deck mechanically attached clay tile roof 
that experienced large blow-off areas. The tiles were attached with two 
nails per tile; however, both nails were located in one corner (Figure 
5-41). A clip near the end of the tile occurred along the eave row. 
However, the clips were ineffective. Many of the tiles were displaced by 
wind pressure, but much of the tile damage was caused by tiles or tile 
fragments impacting other tiles. The hip tiles were nailed with a single 
nail to a ridge board and set in mortar. However, similar to Figure 5-51, 
this attachment method was ineffective. 


Figure 5-40. 
Direct-to-deck 
mechanically attached 
clay tile. The tiles were 
attached with two 
nails per tile. The nails 
typically remained in the 
deck. See Figure 5-41. 



Another direct-to-deck roof is shown in Figure 5-42. This six-year-old 
residence was adjacent to the ocean. Several of the fastener heads had 
corroded off, thus allowing the tiles to lift over the fasteners. 

Figure 5-41. 
Both nails were located 
in the right corner. Better 
load distribution would 
have been achieved by 
placing one of the nails in 
the far left nail hole. 


Figure 5-42. 
The fastener heads 
on this direct-to-deck 
mechanically attached 
tile roof had corroded. 
The six-year old house 
sat near the ocean. 



Several batten-attached roofs were observed. Tiles flying from a midrise 
building, such as that shown in Figure 5-43, can sail a considerable 
distance and have very destructive energy. 

The tiles shown in Figure 5-44 were partially shielded from wind by 
nearby buildings. Hence, while some of the tiles were damaged by wind 
pressure, the majority were damaged by windborne debris (which in
cluded 
tile fragments from this roof). The field tiles were attached 
with a single 2 " long screw. The row of tiles along the eave were at
tached 
with two screws per tile. 


Figure 5-43. 
Loss of several battenattached 
tiles from a 
mid-rise building 



The batten-attached tile damage shown in Figure 5-45 was due to 
increased wind pressure associated with turbulence created by the 
building projection at the upper right of the photograph. Elsewhere on 
this roof, there was intermittent damage to field tiles from windborne 
debris, likely consisting of tiles that were missing from the upper level 
roof and/or tiles blown from the area shown in Figure 5-45. 


Figure 5-44. 
Although some of 
these batten-attached 
tiles were damaged 
by wind pressure, the 
majority were damaged 
by windborne debris 
(which included tile 
fragments). 


Figure 5-45. 
The majority of these 
batten-attached tiles 
were displaced by wind 
pressure. The fasteners 
typically remained in the 
battens. 



The batten-attached tile damage shown in Figure 5-46 was primarily 
caused by wind pressure. Several of the battens were blown away, thus 
indicating inadequate attachment of the battens. 

Foam-set Tile Roofs 

The building shown in Figure 5-46 had a lower-level roof that had a 
relatively low-sloped roof. The foam-set attachment method was used 
on the lower roof. The damage shown in Figure 5-47 was caused by 
wind pressure and windborne debris. 

Figure 5-46. 
The majority of these 
batten-attached tiles 
were displaced by wind 
pressure. Many battens 
were blown away. See 
Figure 5-47 for a view of 
the lower-sloped roof. 


Figure 5-47. 
The tiles on the lower 
sloped roof were foamset. 
The damage on 
this roof was due to a 
combination of wind 
pressure and windborne 
debris. 



Tiles were blown off of several areas of the roof shown in Figure 5-48. 
These failures were caused by significant workmanship errors, wherein 
too little adhesive was applied (Figures 5-49 and 5-50). 


Figure 5-48. 
These tiles were foamset. 
See Figures 5-49 and 
5-50. 


Figure 5-49. 
A minuscule amount 
of foam was installed. 
Note that one tile slid 
down-slope about 2" (red 
arrow). See Figure 5-50. 



Hip and Ridge Tiles 

As observed in Hurricanes Charley and Frances, blow-off of hip and 
ridge tiles was very common, even when the trim tiles were nailed to a 
ridge board and set in mortar (Figure 5-51). On one of the observed 
roofs, the hip tiles were foam-set, but failure also occurred with this 
attachment method (Figure 5-52). Hurricane Recovery Advisory Num
ber 
3 (see Appendix D) provides recommendations for enhancing 
attachment of hip and ridge tiles. 


Figure 5-50. 
View of the underside of 
the tile that slid in Figure 
5-49. Note the very 
limited amount of foam 
on the underside of the 
tile and underlayment. 

Figure 5-51. 
Significant loss of hip and 
ridge tiles. The trim tiles 
were set in mortar and 
were attached to a ridge 
board with a single nail 
near the head of the trim 
tile. 



5.4.3 Metal Panel and Shingle Roofs 

A variety of standing seam and exposed fastener panel systems was 
observed, as well as metal shingles. The observations of the Hurricane 
Ivan MAT were similar and consistent with the observations of the Hur
ricane 
Charley MAT. The performance of metal roofing varied greatly. 
Figure 5-53 shows a complex that lost several standing seam panels. 
At one area the panels remained on the roof, but a few of the seams 
opened up (Figure 5-54). In the opened condition, the panels were 
very susceptible to progressive failure, and they were no longer in a 
watertight condition. 


Figure 5-52. 
These hip and ridge tiles 
were foam-set. 

Figure 5-53. 
Loss of standing seam 
metal panels. See Figure 
5-54. (Pensacola) 



As with Hurricane Charley, excellent performance was typically ob
served 
with 5-V crimp metal panel systems. Figure 5-55 shows special 
attention given to attachment along a rake. 


Figure 5-54. These 
panels nearly blew away. 
The seams on three of 
the panels opened up. 
(Pensacola) 


Figure 5-55. 
This 5-V crimp metal panel roof performed 
very well. The screws along the rake were 
very closely spaced; thus, this potentially 
vulnerable edge condition was well secured. 



More metal shingles were observed in the area impacted by Hurricane 
Ivan than in the area impacted by Hurricane Charley. Several battenattached 
metal shingles that simulated the appearance of tile were 
observed. While some of the metal shingles performed well, many fail
ures 
similar to Figure 5-56 were observed. As with other types of roof 
coverings, attention to connections (including attachment of the bat
tens 
for batten-attached systems) is important with metal shingles. 

5.4.4 Low-slope Membrane Systems 

The MAT observed several types of low-slope roof systems. These 
systems included built-up roofs (BURs), modified bitumen, and sin
gle-
ply. Membrane damage was typically caused by windborne debris 
punctures and tears, and by membrane lifting and peeling after lifting 
of either the gutter, edge flashing, or coping. Figure 5-57 shows an 
edge flashing at a hospital that partially lifted. With the flashing in a 
lifted position, the membrane was very susceptible to peeling. Appar
ently, 
the winds subsided before this occurred. 


Figure 5-56. 
This residence had metal 
shingles that simulated 
the appearance of tile. 
The shingles typically 
blew off the battens, but 
some of the battens were 
also blown away. 



Another type of edge failure is shown in Figure 5-58. At this hospital, 
the wooden nailer at the roof edge was bolted to a brick wall, but be
cause 
of an inadequate load path, the bricks lifted up with the nailer. 
The nailer failure resulted in progressive lifting and peeling of the 
roof membrane. Nailer lifting may have also initiated the failure on 
the hospital roof shown in Figure 6-3, although as discussed in Sec
tion 
6.2.2, that failure may have been initiated by lifting and peeling 
of the edge flashing or by debonding of the insulation from the con
crete 
roof deck. The 4' x 8' polyisocyanurate insulation boards had 
been attached to the deck with hot asphalt. This attachment method 
can be very effective, but it requires good contact between the boards 
and asphalt, which can be difficult to achieve if the deck surface is 
not a relatively flat plane. The use of 4' x 4' versus 4' x 8' boards facili
tates 
conformance to irregular substrates. Use of relatively thin boards 
(e.g., 1 " thick) also facilitates conformance. 

Figure 5-57. 
Although the metal 
edge flashing lifted, a 
progressive membrane 
lifting and peeling did not 
occur. Some aggregate 
ballast was blown off 
an adjacent higher roof. 
(Pensacola) 



Figure 5-59 shows blow-off of a large portion of a BUR on an Emer
gency 
Operations Center (EOC). The membrane was mechanically 
attached to a lightweight insulating concrete (LWIC) deck. In one 
area the base sheet had been attached along the side lap with fasten
ers 
spaced at 8 ", 9 " and 8". At one of the adjacent intermediate 
rows, the fasteners were at 32 " and 32". The typical base sheet 
attachment specification is 9" at the laps and 18" at two intermedi
ate 
rows. The failure may have been initiated because of inadequate 
attachment of the base sheet; however, it may have initiated at the 
parapet base flashing. The base flashing was mechanically attached 
to the parapet. Turbulence at a corner area (inset in Figure 5-59) 
likely generated high suction loads on the base flashing, which may 
have been sufficient to pull the base flashing off the parapet and 
cause a progressive lifting and peeling of the membrane. Parapet 
base flashing damage was also observed on a new hospital addition 
(Figure 5-60). 

Figure 5-58. 
The edge nailer on top 
of an old brick wall was 
inadequately attached 
to the wall. Failure of 
the nailer caused a 
progressive lifting and 
peeling failure of the 
roof membrane. 
(Pensacola) 



Figure 5-59. 
Loss of a mineralsurfaced 
BUR installed 
over LWIC. Failure 
may have been due to 
inadequate attachment 
of the base flashing to 
the parapet (see inset). 
(Pensacola) 


Figure 5-60. 
Minor base flashing 
displacement on a 
new hospital roof 
(Gulf Breeze) 



Figure 5-61 shows a single-ply membrane on a school that had been 
torn by windborne debris. This tear was still unprotected six days after 
it was damaged. Although this is a minor problem compared to a large 
blow-off such as shown in Figure 5-59, a substantial amount of water 
can enter the roof system through a tear such as this. Unless there 
is a secondary membrane as discussed in FEMA 424, Design Guide for 
Improving School Safety in Earthquakes, Floods, and High Winds, January 
2004, significant interior water damage can be caused by minor punc
tures 
and tears. Figure 5-62 shows a hospital roof that was punctured 
in several locations by windborne debris. 


Figure 5-61. 
Single-ply membrane 
torn by windborne debris 
(Pensacola) 

Figure 5-62. 
This hospital roof had 
been punctured in 
several locations by 
windborne debris. When 
punctured, a secondary 
membrane, as discussed 
in FEMA 424, is needed 
to avoid water infiltration. 
(Pensacola) 



Aggregate ballasted single-ply membrane roofs were observed at two 
hospital complexes (Figure 5-57 and 5-64). Some aggregates blew off 
of at least one of the roof areas. None of these roofs comply with the 
current edition of ANSI/SPRI RP-4 Wind Design Standard For Ballasted 
Single-ply Roofing Systems. Use of aggregate ballast on a hospital roof in 
a hurricane-prone region is not prudent. 

5.5 Windows, Shutters, and Skylights 

Exterior windows are very susceptible to missile breakage unless 
they are impact resistant (via use of laminated glass or shutters). 
The probability that any one window will be struck by windborne 
debris is typically small; however, when it does occur, the consequences 
can be significant. The probability of impact depends upon local wind 
characteristics and the amount of natural and manmade windborne 
debris in the vicinity. The greater the wind speed, the greater the 
amount of windborne debris that is likely to become airborne. Win
dows 
can also be broken by over-pressurization, but this damage is not 
as common as debris-induced damage. 

The 2001 FBC defines windborne debris regions as those specified in 
ASCE 7-02, except in the Florida Panhandle, where the 2001 FBC has 
different requirements than ASCE 7. This difference in windborne 
debris regions is discussed in Section 2.2.4.3. In windborne debris 
regions, the 2001 FBC requires glazing to be impact resistant or pro
tected 
by shutters (glazing above 60 feet from grade is exempt). 

The MAT observed shutters on several residential and commercial build
ings 
along the coast and inland areas. However, shuttering was not as 
prevalent as in the areas impacted by Hurricane Charley and Frances. 

5.5.1 Unprotected Glazing 

Figure 5-63 shows a residence along the coast. Several of the ocean-fac
ing 
windows were broken by debris from the failed deck. Figure 7-10 
also shows several ocean-facing windows in a mid-rise condominium 
that were broken by windborne debris that included balcony railings 
and non-load-bearing stucco wall components. The MAT observed 
many instances of windborne debris-induced failure of unprotected 
ocean-facing windows. 

Although windborne debris-induced failure of unprotected glazing 
was more frequently observed on the barrier islands than in inland 
areas, broken glazing was observed in inland areas, including the 



Pensacola area, as shown in Figures 5-4, 5-16, 5-64, and 6-4. In both 
coastal and inland areas, glazing damage more commonly occurred 
on the lower floors of buildings due to the greater amount of debris 
flying at lower elevations. However, broken glazing was observed on 
upper levels as shown in Figures 5-16 and 7-15. 

As discussed in the Hurricane Charley MAT report, damage to un
protected 
glazing in inland areas is more likely to occur when wind 
speeds are 120 mph (3-second gust) or greater. With declining wind 
speed, the incidence of glazing damage is reduced. The Hurricane 
Charley MAT observed very few broken windows in inland areas where 
the wind speed was estimated to be less than about 100 mph 3-second 
gust. The Hurricane Ivan MATs observations are consistent with those 
from Hurricane Charley. In the Pensacola area, where the estimated 
Exposure B wind speeds were between 90 and 100 mph 3-second gust, 
glazing damage was limited, except in areas where significant amounts 
of windborne debris were flying, as illustrated in Figures 6-4 and 5-16. 
Had Hurricane Ivan been closer to a design wind speed event, the 
amount of glazing damage in inland areas would have undoubtedly 
been higher. 

At the condominium shown in Figures 7-8 and 7-9, an unusual window 
failure resulted in extensive secondary damages. The lower portion 
of the small windows shown in Figure 7-8 were inward-opening hop
per 
windows (i.e., they were hinged along the bottom of the window 
frame). Because the latch at the top of the hoppers was very weak and 
incapable of resisting the positive wind pressure applied to the glazing, 
many of the hoppers opened. The open windows allowed an increase 
in the internal pressure. The high internal pressure pushed over the 
interior partitions (Figure 7-9). The high internal pressure also ex
erted 
load on the curtain wall facing the ocean, which combined with 
the exterior suction load to cause the curtain walls to fail. The curtain 
walls metal stud tracks were attached with powder driven fasteners 
into the concrete slab. The number of fasteners was insufficient to re
sist 
the applied loads. 



Figure 5-63. 
Several windows 
on this ocean-front 
home were broken by 
windborne debris. 


Figure 5-64. 
The outer pane of this tempered glass window 
was broken by windborne debris (aggregate 
roof ballast, falling glass shards from windows 
above, or EIFS). (Pensacola) 



5.5.2 Protected Glazing 

The MAT did not observe any laminated glass that had been impacted 
by debris, other than a skylight as discussed in Section 5.5.3. However, a 
variety of shutters were observed. They were made of wood sheathing, 
metal panels, or plastic panels of various designs. The MAT observed a 
few cases where shutters were impacted by debris and were effective in 
preventing glass breakage (Figure 5-65). 

A few problems were observed with shutters. At the school shown in 
Figure 5-66, shutters had been retrofitted. However, shutters were not 
placed over the windows above and below window air conditioners 
or over the glazed entrance doors. Although the shutters that were 
installed decreased the amount of exposed glass and, as a result, re
duced 
the probability of glazing damage, a shuttering project should 
protect all exterior glazing. Another problem is illustrated by Figure 5- 
67, wherein metal panels did not completely cover the glazing. Also, at 
that shutter, wing-nuts were installed at only every other fastener stud. 
Installation of nuts on every other stud was observed on several differ
ent 
buildings. When all of the nuts are not installed, shutters are more 
susceptible of being blown away. 


Figure 5-65. 
This shutter was impacted by high-energy debris. 



Figure 5-66. 
Shutters had been retrofitted on this school, but the 
glazing above and below the window air conditioners 
and the glass entry doors were not protected. 
(Pensacola) 


Figure 5-67. 
These panels did not 
completely cover the 
glazing. Also, along 
the bottom track, a 
wing-nut was placed 
only at every other 
fastener stud. The 
shutter may have 
been impacted on the 
right side. 



Two of the panes in the window unit shown in Figure 5-68 were bro
ken 
because the window unit was not fully protected. It was unclear 
whether some of the shutter panels blew away or were never installed. 
At the lower shutter track, rather than employ fixed fastener studs, 
the studs were slid into the track at the track ends. This type of stud 
connector relies on friction to keep the studs from moving sideways. If 
the nuts are not snug, the panels can drift sideways and be blown from 
the track. It was clear that one of the panels had not been fabricated 
for this unit. This illustrates a potential problem with panel shutters. 
When shutter panels are removed from storage for installation, it is im
portant 
for the panels to have been labeled so that the proper panels 
go over the intended windows. 

5.5.3 Skylights 

Figure 5-69 shows a skylight at a hospital canopy. Several of the lami
nated 
glass panels had been impacted by debris and were broken, but 
the glass remained in the frames. 

When tempered glass breaks, it shatters into small pieces and falls out 
of the frame, as shown in Figure 5-64. However, as shown in Figure 
5-69, when laminated glass breaks, the glass remains bonded to the 
plastic film between the panes, and the glazing remains in the frame. 
Although the broken laminated glass will need to be replaced, costly 
interior water and wind damage is avoided. 


Figure 5-68. 
It was unclear whether 
some panels blew away, 
or the glazing was not 
fully protected. Note the 
debris embedded in the 
window mullion. 



5.6 Exterior Mechanical and Electrical 
Equipment Damage 

The MAT observed many damages to mechanical and electrical 
devices mounted on the exterior of buildings. The following 
factors are essential to good high-wind performance of exterior 
mechanical and electrical equipment: determining design wind loads 
on equipment and designing suitable attachments to resist the loads; 
special anchoring of fan cowlings and access panels; and special de
sign 
of lightning protection systems (LPS) anchorage. Guidance for 
these design factors is provided in FEMA 424, Design Guide for Improv
ing 
School Safety in Earthquakes, Floods, and High Winds. 

For equipment susceptible to flooding, see Subsection 4.1.3.4 Utilities. 

Commercial, and critical and essential facilities typically have a wide va
riety 
of mechanical and electrical equipment attached to their rooftops 
and elsewhere. Residences also frequently have rooftop equipment. 
Equipment lost included fan units and HVAC units, electrical and 
communications equipment, and LPS. There are several effects due 
to loss of this equipment: in many instances, the displaced equipment 
left large openings through the roof and/or punctured the roof mem
brane; 
equipment loss often affected the operational functions of the 
facilities; and blown-off equipment became high-energy windborne 


Figure 5-69. 
Several laminated glass 
panes were broken, but 
they remained in their 
frames. The panes were 
likely broken by ballast, 
although falling glass 
shards or EIFS may have 
caused the damage. 
(Pensacola) 



debris in some cases. The equipment observed on critical and essen
tial 
facilities was not anchored more effectively than the equipment on 
common commercial buildings. 

5.6.1 Rooftop HVAC Equipment 

As frequently observed following previous hurricanes, many fan units 
were damaged. In some cases, the fans were blown off the curbs be
cause 
too few screws were used to attach the fans to the curbs. In other 
cases, the fans remained attached to their curbs, but the cowlings were 
blown away (Figure 5-70). (FEMA 424 Design Guide for Improving School 
Safety in Earthquakes, Floods, and High Winds provides guidance for jobsite 
strengthening of cowlings.) Figure 5-71 shows loss of a hood over 
a relief air vent. The connectors attaching the hood had insufficient 
strength to resist the wind loads. Although the opening through the 
roof was small, a substantial quantity of rainwater was able to enter 
the school. Because of widespread damage in the Pensacola area, this 
opening remained unprotected for several days after the storm. 


Figure 5-70. 
Loss of two fan cowlings 
on an EOC. Blown-off 
cowlings can tear roof 
membranes and break 
glazing. (Pensacola) 



Figure 5-72 shows loss of a relief air hood and displacement of a sleep
er-
mounted condenser. Sleeper-mounted condensers do not provide 
resistance to uplift or lateral wind loads. 

Figure 5-73 shows that even large HVAC units are susceptible to dam
age 
at moderate wind speeds (winds were estimated to be 85 to 95 
mph in this area). This unit reportedly weighed 18,000 pounds. It was 
30' long, 10' wide, and 8' high. It was attached to a wooden curb with 
sixteen 1" x 1/8" thick straps. Each strap had a single screw into the 
unit and a single 1 " long #14 screw into the curb. The majority of the 

Figure 5-71. 
Loss of the hood at this 
relief air vent allowed 
rainwater to directly 
enter the school. 
(Pensacola) 


Figure 5-72. 
At this hospital, the 
condenser moved off the 
sleepers and a nearby 
relief air hood was blown 
away. (Pensacola) 



screws pulled out of the curb, although some may have failed in shear. 
The unit was located approximately 20 feet from the edge of the build
ing. 
After lifting off the curb, the unit hit and cut the roof membrane 
in several areas and then fell off the building and crushed two unoccu
pied 
vehicles. It was reported that approximately 2" of water collected 
on the second floor. The building was less than one year old. 

Another observed problem was loss of HVAC access panels (Figure 5- 
74). This type of problem was observed at two hospitals. Windblown 
panels can tear roof membranes and break unprotected glazing. Dam
aged 
rooftop ductwork was also observed at hospitals and an EOC 
(Figures 5-75  5-77). The damaged ductwork provided a direct path 
for water to enter the buildings. The majority of the damage was caused 
by wind pressure; however, the damage ductwork shown in Figure 5-77 
was likely caused by roof membrane debris. 


Figure 5-73. 
This large HVAC unit blew 
off a new medical office 
building. It was attached 
with 16 straps (see inset). 
(Gulf Breeze) 



Figure 5-74. 
Sheet metal access 
panels and shrouds were 
blown off this equipment 
at a hospital. Displaced 
panels can tear roof 
membranes and break 
glazing. (Pensacola) 


Figure 5-75. 
Ductwork and fan units 
on this hospital were 
damaged in several 
locations. Some of the 
windows in this area 
were also broken. Note 
the missing downspout. 
(Pensacola) 



Equipment screen damage was also observed (Figure 7-17). Screen 
panels that are blown away can tear roof membranes and break un
protected 
glazing. 

5.6.2 Electrical and Communications Equipment 

Rooftop electrical and communications equipment was also observed 
to be inadequately anchored. Problems included displacement of LPS 
and antenna collapse and debris damage. Collapsed parking lot light 
fixtures were also observed. Consequences of the damage included loss 

Figure 5-76. 
Damaged ductwork 
at a hospital 
(Pensacola) 


Figure 5-77. 
Damaged ductwork at 
an EOC. This damage 
was likely caused by roof 
membrane debris that 
blew off a nearby area. 
(Pensacola) 



of communications, damage to roof coverings, and loss of lightning 
protection, the latter of which is significant, considering the frequency 
of lightning storms in Alabama and Florida. 

LPS failures were typically the result of poorly anchored systems. Con
nectors 
often fail by opening up and releasing the conductor cable or 
they debond from the roof (Figure 5-78). Figure 5-79 illustrates the 
number of roof membrane punctures that can be caused by loose LPS 
conductors. 


Figure 5-78. 
The LPS on this hospital 
became detached. 
Loose LPS can severely 
damage roof membranes, 
and loose LPS does not 
provide the intended 
lightning protection. 
(Pensacola) 

 


Figure 5-79. 
The LPS conductor on 
this hangar became 
detached and punctured 
the roof membrane 
in several locations. 
(Arrows show ends of 
loose cable.) 
(Pensacola) 



Figure 5-80 illustrates damage to antennas from windblown roof de
bris. 
Mounting the antennas on the penthouse wall was prudent, as 
this avoided penetrations through the roof membrane. However, to 
avoid damage from roof debris, the roof system needs to be sufficiently 
anchored to avoid blow-off. Figure 5-81 shows a collapsed communica
tions 
tower. Collapse of this type of tower has frequently been observed 
following previous hurricanes. 

Figure 5-80. 
The antennas at this 
hospital were damaged 
when the roof membrane 
blew off. (Pensacola) 


Figure 5-81. 
The antenna at this 
hospital collapsed. 
The LPS was also 
displaced in a few areas 
(red arrows). Rooftop 
equipment was also 
damaged. (Pensacola) 



Figure 5-82 shows collapsed light fixtures. These failures were caused 
by severe corrosion. 

Figure 5-82. 
Collapsed light fixtures 
at a hospital. The bottom 
of the tube was severely 
corroded (see inset). 
(Pensacola) 



C 


C H A P T E R 6 

6-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

6 

Performance of 
Critical and 
Essential Facilities 

Critical and essential facilities are needed to lead and manage response 
and recovery operations during and/or after an event. Hurricane Ivan 
had a significant impact on critical and essential facilities. Though all 
of the buildings were subjected to winds that were below design con
ditions, 
the overall performance of the buildings the MAT observed 
was poor. The poor building performance placed additional burden 
on response and recovery personnel as they endeavored to provide as
sistance 
to their communities after the event. According to the 2003 
IBC (Section 1604, Table 1604.5) and the 2001 FBC (Section 1606, 
Table 1606), critical and essential facilities include, but are not limit
ed 
to, hospitals (and other medical facilities), fire and police stations, 
primary communication facilities, disaster (emergency) operations 
centers, and power stations and other utilities required in an emer
gency. 
Schools are also listed in the IBC, but not the FBC. Because of 
the poor performance and reported damage to these facilities, the 
MAT assessed numerous facilities to document the damage and loss 
of function. 

Critical and essential facilities that were damaged include an EOC/po
lice 
station, jails, hospitals, schools, and shelters. Most damage was to 
envelope systems, though a few structural failures did occur (see Chap
ter 
5 for photographs and discussion of envelope damage). Most of 
the damage was to older facilities; however, some newer facilities also 
experienced failure. Except for occasional shuttering of glazed open
ings, 
the investigated buildings did not appear to have been designed 
and constructed with wind-resistance enhancements to the building 
envelope and rooftop equipment. 



C H A P T E R 6 

PERFORMANCE OF CRITICAL AND ESSENTIAL FACILITIES 

6-2 

 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

The MAT observed minimal damages at several jail and fire station 
facilities. This consisted of minor damage to coping, edge flashing, 
and canopies, and loss of fan cowlings  none of which caused any 
significant functional disruption. Maintaining operation of the jails 
avoided transporting and housing inmates in other facilities and 
avoided placing additional burdens on law enforcement personnel. 
Maintaining operation of the fire stations avoided disruption of emer
gency 
response capability. However, all three of the fire stations that 
were observed by the MAT were older pre-engineered metal build
ings. 
Had wind speeds been closer to a current design event, all three 
of these buildings would have likely suffered major damage to the sec
tional 
doors and/or the metal roof panels (see Mitigation Assessment 
Team Report, Hurricane Charley in Florida, FEMA 488 for a discussion of 
fire station performance in Hurricane Charley). 

The MAT did not observe any critical or essential facilities located in 
areas affected by flooding. By being located outside of floodprone 
areas, these critical and essential facilities were able to provide com
munity 
services without interruption due to flooding. 

6.1 Emergency Operation Centers 

E OCs are key buildings in preparing for and responding to an 
event from both local and state levels. The MAT observed only 
one EOC, which was located in the basement of the Escambia 
County Sheriffs Office (in Pensacola). This facility experienced sever
al 
building envelope problems. However, although rainwater entered 
the building, it did not disrupt the EOC operations. 

6.1.1 General Damage 

The original building had two floors above grade. A new two-story 
addition was joined to the original building. Construction of the ad
dition 
was essentially complete when Hurricane Ivan struck. A large 
roof membrane blow-off was experienced in one area (Figure 6-1). 
The damaged membrane was a BUR with a field-applied mineral sur
facing 
over light weight insulating concrete (LWIC). The LWIC was 
likely installed over a structural concrete deck. Although the roof
top 
equipment was inadequately attached on both the original and 
new portions of the building, the equipment was likely damaged by 
windborne roof debris rather than wind pressure. The modified bi
tumen 
roof membrane on the new addition was also damaged. The 
membrane lifted and tore at a roof drain and the base flashing at the 



PERFORMANCE OF CRITICAL AND ESSENTIAL FACILITIES 

parapet was displaced. A portion of the coping was also displaced. 
Some of the windows on the original building were shuttered, but 
some were not  at least one window was broken (likely by windborne 
debris). A portion of the LPS on the new addition was dislodged. 

6.1.2 Functional Loss 

Some rainwater was able to enter the building at damaged rooftop 
equipment, but it was apparent that the roof deck was preventing 
major roof leakage in areas where the roof membrane blew off. Al
though 
the cost to repair the envelope and rainwater damage on the 
original and new portions of the building is significant, the EOC was 
able to continue functioning during and after the hurricane. 

Six days after the hurricane struck, emergency repairs had not been 
made to the roof and open ductwork on this important facility. De
mands 
for repair crews are enormous in the aftermath of a hurricane 
like Ivan. To ensure priority service, it is prudent for owners of critical 
and essential facilities to have pre-established agreements with con
tractors 
to perform emergency inspection and repair if needed. 


Figure 6-1.
General view of the roof 
membrane and rooftop 
equipment damage at 
the Escambia County 
Sheriffs Office/EOC. The 
roof at the upper right 
is on the new addition. 
The mineral surfaced 
BUR landed on an 
aggregate surfaced BUR. 
(Pensacola) 



6.2 Hospitals 

A hospital in Gulf Breeze and all four hospitals and a psychiat
ric-
care hospital in Pensacola were observed. All experienced 
building envelope problems. Though none of the hospitals 
were taken out of service, the envelope damage placed significant 
burdens on several of the facilities. 

6.2.1 General Damage 

Buildings at four of the five hospital complexes experienced roof 
membrane damage  damage was significant at three of the facilities. 
Windows were broken at four of the complexes, with significant dam
age 
at one of them. EIFS blew off the walls at two complexes. At both 
complexes, the EIFS failures resulted in disruption of elevator service 
(see Figures 5-15 and 5-16). At one of the complexes, the EIFS fail
ure 
resulted in significant glazing damage (see Figures 5-16 and 6-2). 
Rooftop equipment and LPSs were damaged at four of the complexes. 
Communications towers and antennas were damaged at two complex
es. 
A loading dock canopy was blown away and several tall parking lot 
light fixtures collapsed at one complex. Sewage backed up in a cancer 
treatment facility because of power loss to a lift station. Tree-fall caused 
roof damage to a materials management building (an ancillary build
ing 
at one complex). 


Figure 6-2. 
View of EIFS damage 
at hospital building 
(Pensacola) 



6.2.2 Functional Loss 

The damage described above placed burdens on hospital staffs and 
took portions of some of the facilities out of service. However, all six 
hospitals were able to continue to provide care. The following is a syn
opsis 
of the major disruptions: 

 At the Pensacola Naval Hospital complex, two patient floors were 
taken out of service because of minor rainwater leakage due to 
roof membrane blow-off from a large portion of the roof (Figures 
6-3 and 6-4). The concrete roof deck was effective in minimizing 
leakage. The modified bitumen membrane had been installed over 
polyisocyanurate insulation mopped to the concrete deck. The blowoff 
was initiated by lifting and peeling of the metal edge flashing, or 
lifting of the wood nailers that the edge flashing was attached to, or 
by debonding of an insulation board from the deck. Debris from the 
roof broke several of the second and third floor windows (including 
some glazed with tempered glass) (Figure 6-4). Roof debris also 
damaged several antennas (Figure 5-80). 


Figure 6-3. 
General view of upper 
roof of the Pensacola 
Naval Hospital. Note 
the missing insulation 
boards near the corner 
of the roof. (Pensacola) 



 At one hospital complex, a portion of the surgical suite and the 
intensive care unit was taken out of service during the hurricane 
due to rainwater infiltration. Sewage disposal was interrupted due 
to lack of power at a lift station  waste was bagged. This interruption 
was of short duration. 

 At one hospital, elevator service at the MOB was interrupted due to 
rainwater infiltration at the elevator penthouse due to EIFS blow off 
(see Figure 5-15). The MOB was connected to the hospital. Sewage 
disposal was interrupted due to lack of power at a lift station. This 
interruption was of short duration. 

 At one hospital complex there were numerous disruptions. 
Communications were lost about an hour after arrival of high 
winds. EIFS failure caused extensive glazing damage and disruption 
of elevator service. Glass shards fell and punctured the roof 
membrane over a regional dialysis unit and urgent care facility. 
However, the roof deck (concrete topping over steel decking) 
minimized rainwater infiltration. Emergency repairs were made, 
and the unit was opened after being out of operation for only 
one day. Rainwater from a punctured roof membrane entered a 
portion of the surgical suite. Sewage back-up disrupted the cancer 
treatment facility for one day. Loss of the canopy at the loading dock 
hampered materials handling. Quick and aggressive emergency 
repairs were responsible for minimizing the impacts of the service 
interruptions at this facility. 


Figure 6-4.
View of a portion of the 
lowest floor roof showing 
broken 2nd and 3rd floor 
windows and debris from 
the roof above shown in 
Figure 6-3 



 At one hospital complex, a very large piece of HVAC equipment 
blew off the MOB roof (see Figure 5-73). Extensive rainwater 
damage occurred on the floor below. An emergency generator was 
brought in to run fans to dry out the facility. 

6.2.3 Best Practices  Hospitals 

Though all of the hospitals had to cope with building performance 
problems, there were observed successes and best practices that contrib
uted 
to minimal damage, particularly in terms of operational actions: 

 Shutters. Some of the buildings had shutters over lower-level 
windows. No shutter breaches were observed. 

 Relocation of patients. At one hospital, patients were moved into 
the corridors in case patient room windows were broken. This 
practice may have been employed at other hospitals, although at 
one of the hospitals, a patient was in a room when a window broke. 
If patient room windows are not impact resistant or protected by 
shutters, moving patients out of the rooms during a hurricane 
appears to be a prudent practice. 

 Satellite dish. At one hospital, satellite dishes were removed from 
their support stands and placed inside a penthouse prior to the 
hurricane. Had this action not been taken, the dishes would likely 
have been blown away and perhaps caused damage to the facility. 
An antenna that was not needed during the hurricane was also 
taken down. 

 Damage response. One hospital experienced significant building 
problems; however, the hospital quickly mobilized contractors and 
cleaning crews. Quick action brought the cancer therapy facility 
and regional dialysis back online within a day, so those vital services 
were only minimally impacted. The rapid damage response also 
likely minimized rainwater damage costs. Rapid response was also 
observed at some of the other hospitals. 

6.3 Schools 

The MAT observed 13 schools, including elementary, middle, and 
high schools. In addition to their traditional role as education
al 
facilities, schools often play an important role in providing 
space for sheltering, emergency response, and recovery after a hurri
cane. 
Thus, their loss of use can greatly impact a communitys ability 
to rapidly respond to the needs of disaster victims. See Section 6.4 for 
additional discussion on schools used as shelters. 



6.3.1 General Damage 

A limited amount of structural damage was observed. It consisted of 
collapsed walkway canopies at a few schools (Figures 4-98 and 6-5), loss 
of a portion of wood joists and roof decking at one school, loss of roof 
decking at one school (Figure 6-6), loss of an auto shop roof struc
ture 
and portion of a CMU load-bearing wall (Figure 6-7), and loss of 
roof joists and collapse of CMU walls at an HVAC chiller enclosure. At 
three of the schools that experienced structural damage, portions of 
the schools were used as shelters. However, the structural damage did 
not occur where people were sheltered. 

All of the observed schools experienced building envelope damage, with 
damage to roof coverings and rooftop equipment being the most com
mon 
problem. Other observed damage included soffit damage, metal 
wall panel damage, and the collapse of a non-load bearing brick wall. 


Figure 6-5. 
Walkway canopy 
collapse at Bellview 
Middle School. Stronger 
winds could have turned 
the debris into lethal 
missiles. (Pensacola) 



Figure 6-6. 
Loss of cementitious wood-fiber roof deck 
panels at Workman Middle School (Pensacola) 


Figure 6-7. 
Loss of the roof structure 
and rear portion of the 
CMU load-bearing wall 
at the George Stone 
Career Center auto shop 
(Pensacola) 



6.3.2 Functional Loss 

Many of the observed schools experienced widespread rainwater 
damage due to breached building envelopes, which resulted in dis
ruption 
or loss of school operations. In some cases, such as that 
shown in Figure 5-71, the envelope damage was minor, but lack of 
quick emergency repairs allowed significant rainwater to subsequent
ly 
enter the building. 

6.4 Shelters 

S helters can be defined in many ways depending on their use. 
A shelter is a place where people go to take refuge during an 
event (often called storm shelters) or to recover when they 
cannot return to their homes immediately after an event due to 
widespread storm damage. For the purposes of this report, the term 
shelters refers to storm shelters or buildings where people went to 
take refuge from the winds and surge during Hurricane Ivan. The 
MAT assessed the performance of some of these storm shelters to 
document how these essential facilities performed. 

Further, because portions of several school buildings evaluated by 
the MAT were designated as storm shelters, damages to schools in 
some communities led to loss of use of shelters that could protect 
residents from injury during subsequent hurricanes. The loss of use 
of schools that function as storm shelters is particularly difficult for 
smaller communities where they often serve as convenient places to 
provide recovery assistance to residents in the days and weeks imme
diately 
after a disaster event. 

For a discussion of the Florida Statewide Emergency Shelter Plan 
(SESP), see Chapter 6 in Mitigation Assessment Team Report, Hurricane 
Charley in Florida, FEMA 488. 

6.4.1 General Damage 

The MAT observed six shelters, five of which were schools. The other 
shelter was the Pensacola Civic Center (a large arena). Structural dam
age 
consisted of collapse of canopies at three of the schools (Figure 
6-5), blow off of roof deck panels at one school (Figure 6-6), and dam
age 
to a stand-alone auto shop at the backside of one school (Figure 
6-7). All five of the schools had roof covering damage, with the damage 
being significant at three of the buildings. One of the schools had an 



aggregate surfaced BUR. A substantial amount of aggregate was blown 
off and, subsequently, broke windows in one or more vehicles. Metal 
wall panels were blown off one of the schools and the Civic Center. 
Rooftop equipment was blown off of two schools and the Civic Center; 
a large fan from the Civic Center crushed an unoccupied car. 

6.4.2 Functional Loss 

Pensacola Civic Center had an occupant load of approximately 1,600 
to 2,000 people at the time Hurricane Ivan struck. Five pieces of roof
top 
equipment over the arena floor were blown off. (For information 
on the roof membrane damage caused by the equipment blow off, 
see Withstanding Hurricane Ivan in the February 2005 issue of In
terface 
(published by the Roof Consultants Institute). 

However, the wind speeds quoted in the article are incorrect. As an 
added safety measure, people were moved out of the arena into pe
ripheral 
areas of the facility before the high winds arrived. Thus, 
although rainwater entered the arena, people were not left exposed. 
Portable toilets were placed within the arena area prior to the hur
ricane. 
That proved to be prudent, for the center lost sewage service 
due to lift station power failure. 

The Jim C. Bailey Middle School (built in 1995) was used as a shel
ter. 
Rainwater entered the building in several different areas where 
asphalt shingles, underlayment, rooftop equipment, and metal wall 
panels were blown off (Figure 6-8). The shingles were attached with 
only four nails instead of six, which the roofing industry recommends 
in high wind areas. The nails were incorrectly located (they were too 
high and at one of the shingles, an end nail was 2  inches rather 
than 1 inch from the end). People were moved from one portion of 
the building to another to escape the rainwater leakage. 



The Workman Middle School sheltered approximately 25 people, 
including about 10 police officers who came in from patrol shortly 
before arrival of the high winds. Although a portion of the school 
complex experienced structural damage (Figure 6-6), no injuries were 
reported. Occupants took shelter in a newer building on campus that 
did not experience structural failure. As shown in Figure 3-26, a sub
stantial 
amount of windborne debris (primarily roofing and canopy 
components from the school) was airborne in this area. 

All of the shelters observed by the MAT experienced blow-off of build
ing 
components. When building components are blown off there is a 
risk that people arriving at a shelter during the hurricane may be in
jured 
or killed. For this reason, buildings selected for shelters should 
be designed and constructed to avoid loss of components. Items par
ticularly 
susceptible to blow-off include aggregate roof surfacing. Roof 
coverings and rooftop equipment were also susceptible if adequate at
tention 
was not given to wind-resistant design and construction. 

At the time of the MAT observations (six days after the hurricane), 
none of the five schools were being used. Some of the schools had too 
much rainwater damage to be of service. 

Figure 6-8. 
Loss of asphalt shingles 
and underlayment 
at the Jim C. Bailey 
Middle School. Note the 
displaced wall panels at 
the upper left and the 
missing panel in
the lower right. 
(Pensacola) 



C 


C H A P T E R 7 

7-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

7 

Conclusions 

The conclusions presented in this report are based on the MATs ob
servations 
in the areas studied; evaluations of relevant codes, standards, 
and regulations; and meetings with state and local officials, business 
and trade associations, contractors, and other interested parties. These 
conclusions are intended to assist the State of Alabama, the State of 
Florida, communities, businesses, and individuals in the reconstruc
tion 
process and to help reduce future damage and impact from flood 
and wind events similar to Hurricane Ivan. The report and recommen
dations 
also will help FEMA assess the adequacy of its flood hazard 
mapping and floodplain management requirements and determine 
whether changes are needed or additional guidance required. 

7.1 Flood Hazard Conclusions 

Flood levels from Hurricane Ivan exceeded the mapped BFEs 
throughout many bays and sounds by several feet. Flood levels 
along Gulf front shorelines also exceeded the mapped BFEs 
but to a lesser extent. As discussed in Chapters 1 and 2, HWMs were 
clearly higher than the stillwater levels used to develop the flood maps 
and were also higher than the BFEs, which include wave heights that 
are not accounted for in the HWMs. Due to these high flood levels, 
the flooding extended beyond the SFHAs in most communities in
vestigated. 
Since many homes were pre-FIRM construction and/or 
constructed to the minimum standards in mapped A Zones and the 
flooding extended beyond the current SFHAs, there was severe dam
age 
of single and multi-family buildings throughout the inland bays 
and sounds, and along the barrier islands in Baldwin County, Ala
bama, 
and the western Florida Panhandle (see Figure 7-1). 



C H A P T E R 7 

CONCLUSIONS 

7-2 

 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

Two circumstances probably account for the fact that the high flood 
levels exceeded the BFEs: 

1) Hurricane Ivans storm surge was greater than the stillwater 
elevations of the mapped 100-year flood event. The stillwater 
elevations are used in the coastal flood analysis to determine the 
minimum elevations standards (BFEs). As noted in Chapter 1, 
the preliminary estimated return period for Hurricane Ivan was 
approximately a 150-year storm. However, the data used to develop 
this return period was extremely limited, and further analysis 
should be performed. 

2) The storm surge overwashed the barrier islands, thus allowing 
more water to enter into the back bays and sounds, especially in 
those areas immediately behind the barrier islands (see Figure 
7-2). This overwash effect was not accounted for in the initial 
storm surge modeling used to develop the stillwater elevations, 
which are the main input parameters in the wave height analysis 
to determine the BFEs and zone designations. Without the 
overwash effect, the flood levels in these back bays and sounds 
would be underestimated. In addition, the storm surge modeling 
was performed over 25 years ago and did not account for possible 
subsequent changes in the topography of the barrier islands. The 
barrier islands have been significantly altered over these last two 
decades as a result of numerous tropical storms and hurricanes, 
including Hurricane Opal, which drastically altered and destroyed 
many of the dunes on the barrier islands. When these dunes stood 
higher than 15-25 feet, as they did when the initial surge model 
was developed, they prevented the floodwaters from overwashing 
the barriers; the only way the storm surge entered the bays and 
sounds was through the inlets. Now that the barriers islands have 
been impacted and altered by Hurricane Ivan, the contribution 
of the overwash into the back bays and sounds will continue to be 
a factor for future events. 



CONCLUSIONS 

Floodborne debris and wave damage (characteristic of V-Zone damage) 
in A Zones was extensive, especially along bay and sound shorelines. 
The storm surge and wave impacts destroyed buildings, enclosures, 
stairs, utilities, and docks and piers, which all became floodborne de
bris. 
Structures that were not elevated higher than the storm surge 
were not only damaged by floodwaters and wave action, but also im
pacted 
by the floodborne debris. 

Figure 7-1. 
Newly constructed 
house in Zone AE, which 
was damaged due to 
high flood levels and 
impacts from waves and 
floodborne debris. The 
effective FIRM shows the 
BFE as 9 feet, but the 
flood levels exceeded this 
by 3-5 feet. (Big Lagoon) 


Figure 7-2. 
Barrier island on Santa 
Rosa Island, east of 
Pensacola Beach, 
which was completely 
overwashed by storm 
surge. The storm surge 
then inundated the Santa 
Rosa Sound. 



Erosion was severe along the barrier islands of Alabama and Flori
da. 
Areas that had wide beaches before Ivan were less impacted than 
those with smaller, narrower beaches. Erosion along bay and sound 
shorelines was generally minimal, and structural damage there was 
predominantly due to storm surge, waves, and floodborne debris. The 
erosion undermined shallow foundations and piers with shallow em
bedment. 
Many areas were susceptible and impacted by past coastal 
storm events, which led to further erosion and impact from Ivan. The 
methodology used to develop the FIRMs takes into account the erosion 
that would likely occur during the 100-year event. However, this analy
sis 
accounts for only one event and not multiple events that change 
or alter the barrier islands and dunes. Based on the eroded condi
tions 
from this one 100-year event, a wave height analysis is performed 
to determine the BFEs and the zone designations. Buildings are con
structed 
to the standards developed and mapped on the FIRMs. These 
standards remain in-place for years and/or decades until a significant 
event results in severe damage or the methodology has been modi
fied. 
After Hurricane Opal, which impacted much of the same area as 
Hurricane Ivan, the FIRMs were revised due to the severe damage, the 
observed HWMs, and new coastal methodologies that had been devel
oped. 
Although smaller events had affected the coastal topography on 
the barrier islands and the new methodologies had been in place for 
over five years, it took a severe event like Hurricane Opal to instigate 
a map change. 

7.1.1 Lowest Floor Elevations 

One of the critical factors for this event was that the amount of dam
age 
to the building was in direct correlation with the elevation of the 
lowest floor (see Figure 7-3). Generally, the lowest floor elevation was 
a function of the type of foundation chosen for the building. Pile foun
dations 
had the advantage of getting the lowest floor up a full story, 
which usually placed it several feet above BFE. Other foundation types 
often resulted in buildings that were at BFE or only slightly higher. For 
Hurricane Ivan, this difference in elevation made a great difference in 
flood and debris damages. 

Most of the damaged buildings occurred in areas mapped as A Zone 
on the current FIRM, although many of the buildings were pre-FIRM 
construction and built on slab foundations. The elevation of the build
ings 
varied throughout the impacted area as well as among houses in 
the same neighborhood and along the same street. Generally, build
ings 
near or on the bays or sounds, constructed to the BFEs or below 
for the pre-FIRM buildings, experienced significant flood levels and 



damaging waves and floodborne debris. FIRM revisions over the past 
two decades have resulted in changes in flood hazard zone desig
nations 
and BFEs. This has led to varied construction practices and 
different lowest floor elevations throughout the coastal areas. These 
map changes may explain some of the variations in structural dam
ages 
observed. However, many newer structures that were constructed 
to the minimum NFIP standards were severely damaged by the high 
storm surge elevations, while many buildings that were constructed 
several feet higher than the minimum standards were much less dam
aged. 
Figure 7-1 is also an example of a building built to the current 
minimum standards that sustained severe damage. 

Some of the variations in building elevations were based on: 

 Changes in the BFE on the FIRMs 

 Higher building elevation requirements such as SRIA 

 Homeowners voluntarily chose to elevate higher than the BFE on 
pile foundations for various reasons: for a better view, to create 
additional parking or storage areas, as a cautionary measure because 
of the proximity to a large bay or sound and the potential flood 
hazard, and/or because other adjacent buildings were elevated 
several feet above the BFE 

 Recommendations by contractors, engineers, architects, state and 
local building and floodplain management officials 

Figure 7-3. 
Lowest floor elevation 
was one of the most 
important factors in 
determining building 
damage during Ivan (Gulf 
Shores, Little Lagoon) 



7.1.2 Foundations and Structures 

On the barrier island, relatively few pile failures were observed during 
field inspections of newer, post-Hurricane Opal homes. However, pre
liminary 
review of pre- and post-Ivan aerial photography indicates many 
pile-supported homes along the beachfront may have been destroyed 
due to some combination of erosion, flood, and wind effects. Poor struc
ture-
to-beam connections likely resulted in intact piles and beams with 
structures missing from atop the foundations. Had these structure-tofoundation 
connections been adequate, these structures would have 
been damaged but probably would have remained in place. 

In areas subjected to coastal erosion and scour, shallow foundation 
damage was extensive and the structural failures dramatic. Shallow 
foundations are not appropriate for supporting structures in high risk 
coastal areas. 

In the bays and sounds, there was generally very little scour or erosion 
that affected the foundations, although some was observed behind 
bulkheads. Overall, since scour and erosion was not a factor, newer 
stem wall and pile foundations performed well; however, once the 
flood levels and wave heights exceeded the lowest floor, severe damage 
resulted to the building. Many older pier and pile foundations failed 
as the result of flood and wave loads that were above the lowest floor 
and exerted pressure on the buildings. The failures occurred due to 
lack of connections, tie-downs, and reinforced concrete. Figure 7-1 is 
also an example of a building constructed on a stem wall foundation, 
which was not impacted by erosion or scour, but due to the elevation 
of the building, the high flood levels and wave and debris impacts to
tally 
destroyed the building. 

7.1.3 Piers and Docks 

The construction of pier and docks, which extend several hundred 
feet in the bays and sounds, was prevalent throughout the impacted 
coastal areas. Damage to these systems was extensive, and dock materi
als 
and pilings provided a significant source of damaging debris. Piles 
and dock sections were found in the lower areas of buildings, which 
contributed to the destruction of many homes. 



7.1.4 Construction Features beneath Elevated Buildings 

The newer buildings built to V-Zone standards with adequate pile em
bedment, 
generally performed well. Breakaway walls functioned as 
intended with the exception of those situations where a clear break
away 
joint separation was not achieved, which led to siding and building 
component damage above the breakaway wall. Utility damages were 
observed when utility connections were attached to or passed through 
breakaway walls. Enclosed areas and stairways were destroyed or se
verely 
damaged, as would be expected. 

NFIP minimum standards require that buildings constructed in V 
Zones be elevated on piles or columns so that the bottom of the lowest 
horizontal structural member of the building is above the BFE. The 
area below the lowest horizontal member must be left free of obstruc
tions 
or enclosed with non-structural breakaway walls, insect screening, 
or latticework, and the area's use be restricted to parking, building ac
cess, 
or storage. The standards were developed with the understanding 
that the area below the lowest horizontal member would be sacrificial 
and would be totally destroyed during a major flood event. 

During Hurricane Ivan, these construction features (e.g., access stairs 
and enclosures) beneath elevated buildings were often destroyed. Not 
only were the enclosed areas, stairs, utilities, and other systems severely 
damaged, but they also become a significant source of floodborne de
bris. 
Many enclosed areas below the lowest floor were fully enclosed 
and, in some cases, finished as additional living space. These features 
are becoming more substantial and are a significant source of flood
 


Figure 7-4. 
Docks along back bays 
contributed to flood 
debris causing extensive 
damage. 



borne debris. Once dislodged by storm surge, wave action, or wind, 
these features can act as obstructions and create unanticipated loads 
on the foundations and increase the potential for structural failure for 
many buildings. 

Stairs and building access features are becoming more elaborate and 
expensive, increasing the total dollar damages resulting from the 
event. Most of the damage below the lowest floor is preventable by lim
iting 
the construction of these enclosures and other systems beneath 
the elevated building. 

7.1.5 Pools and Bulkheads 

Pools and bulkheads suffered extensive damage and should be viewed 
as sacrificial features during a major hurricane. 


Figure 7-5. 
Access stairs and 
enclosures that were 
constructed below 
the lowest floor were 
severely damaged. 



7.1.6 Utilities 

Exterior utilities suffered extensive flood damage when not elevated or 
sited properly. The lack of design and installation attention resulted in 
destruction of building service utility lines, systems, and equipment, and 
led to the loss of function of the occupied space. Compliance with cur
rent 
FEMA publications and codes is essential to the future prevention 
of damages of this type. Figure 7-7 shows an inappropriately mounted 
condenser that was carried off its platform by high floodwaters. 

Figure 7-6. 
Typical failure of swimming pools and bulkheads 
(Gulf Shores) 



7.2 Wind Hazard Conclusions 

While Hurricane Ivan is categorized as a Category 3 major 
hurricane by the NHC in its Tropical Cyclone Report with 
estimated 1-minute sustained wind speeds (over open water) 
of 121 mph, the actual wind speeds gathered on land (presented in 
Chapters 1 and 2) suggest Ivan was more typical of a Category 1 to 2 
hurricane. Flood-related hazards such as storm surge, floodborne de
bris, 
inundation, and wave action were the primary cause of damage. 
The categorization of the storm by a single hurricane classification has 
limited use in the post storm assessment and may lead people in the 
impacted areas to draw incorrect conclusions about the event they ac
tually 
experienced at their site and the strength of their building. The 
development of wind field estimates and resulting wind speed swath 
maps are critical to the proper assessment of an event and its implica
tions 
for building construction and code development. The response 
of buildings to the high winds varied in relationship to their location 
in the wind field, building code in effect at the time of construction, 
and mitigation efforts implemented on the building. 

Although structural system failures tend to be perceived by the pub
lic 
and the building industry as the dominant issue of concern, it is 
clear that for buildings built in accordance with the 2001 FBC or the 
2000/2003 IBC, structural issues have, in general, been resolved. Now, 

Figure 7-7. 
Inappropriately mounted 
condensers for a 
coastal residential site 
that should have been 
mounted at a higher 
elevation and securely 
anchored to their 
platform 



the arena in which improvements can and must be made are those re
lated 
to water intrusion and protection of the building envelope (refer 
to Chapter 5). Protection of the building envelope is important to mini
mizing 
losses and damages to building contents, but also because of 
the importance of the building envelope with respect to internal pres
surization 
of a building or structure. In addition, failure in the building 
envelope often leads to progressive failures in structural systems. 

Widespread building envelope damage was observed throughout the area 
visited by the MAT. Performance of building envelope elements such as 
roof coverings, roof mounted equipment, unprotected glazing, doors, 
soffits, and siding was generally poor and led to widespread damage to 
the interiors of residences, businesses, and critical/essential facilities. 

Windborne debris damage was observed, but was not widespread across 
the entire path of the hurricane. Wind and structural engineering ex
perts 
predict that significant windborne debris damage will begin in 
the 120-mph range in inland areas and in the 110-mph range when 
buildings are within one mile of the coast. In response to this, ASCE 
7 requires that openings in the geographic areas described above be 
protected to resist windborne debris impact. Since Ivans estimated 
gust speeds were generally below that level, it is expected that glazing 
damage during Ivan would be less common than in other more pow
erful 
storms, such as Hurricane Charley. Given that the actual wind 
speeds were below current code level wind speeds but at or near the 
older code level wind speeds, the occasional damage to the structural 
elements and the widespread damage to building envelopes can be 
characterized as wind-related damage caused by inadequate design, 
old construction methods, outdated codes, building age, lack of main
tenance, 
and/or poor construction/code enforcement. Wind damage 
to the contents of residential and commercial buildings, and critical/ 
essential facilities due to these failures is clearly preventable. 

This reports conclusions and recommendations relate only to what 
was observed by the MAT in Hurricane Ivan. The conclusions and rec
ommendations 
of the Hurricane Charley MAT report (FEMA 488) 
with regard to wind hazards are also relevant to design and construc
tion 
in the areas impacted by Hurricane Ivan because similarities in 
damage observations exist. Hurricane Charley was a code level wind 
event along much of the hurricanes path, and readers are encouraged 
to obtain a copy of this report. In addition, a summary report for all 
four hurricanes that impacted Florida in 2004 is available (FEMA 490, 
Summary Report on Building Performance 2004 Hurricane Season, March 
2005). This report is available online at http://www.fema.gov/fima/ 
mat/fema490.shtm. 



7.2.1 Building Performance and Compliance with the Building 
Codes, Statutes, and Regulatory Requirements of the States of 
Alabama and Florida 

Most building damage and failures observed by the MAT appeared 
to be the result of inadequate design and construction methods com
monly 
used before the 2000/2003 IBC and the 2001 FBC. Some 
observed damage and failures might be explained by lack of mainte
nance 
or poor condition of the building. Code changes implemented 
in response to Hurricane Andrew in 1992, such as improvements to 
the SBC and the adoption of the 2001 FBC, can be credited with im
proving 
the wind resistance of buildings that have been designed and 
constructed over the past 12 years. In addition, the improvements in 
ASCE 7, including the addition of windborne debris protection re
quirements 
and the elimination of the 1/3 stress increase factor, are 
further refining the loads that new buildings must resist, thus ensuring 
better performance in wind events. 

A summary of the historical code prescribed wind pressures over the 
last 25 years at two locations within the Hurricane Ivan damage zone is 
presented in Table 7-1. Typical single family residences in Gulf Shores, 
Alabama, and Perdido Key, Florida, as well as a small essential facility 
in the city of Pensacola, Florida, were selected for comparison. The 
table shows that the design wind pressures have been changing, and 
sometimes increasing, with each new code; therefore, it would be ex
pected 
that failures of older buildings would be common if this were a 
code level wind event. For example, the required pressure for corner 
zones of roofs has increased more than 3 fold over that period. Corner 
zone pressures did not even exist in the 1979 SBC. These increases 
are a reflection of the findings of both wind tunnel research and poststorm 
investigations. The pressures have increased most dramatically 
on the parts of buildings that have suffered worst in wind storms. 

To properly evaluate the compliance with past building codes, an anal
ysis 
of the actual pressures experienced by the buildings in Hurricane 
Ivan was necessary. In addition to the design pressures for the current 
and two preceding codes, Table 7-1 also contains the estimated actual 
pressures thought to have been experienced at these locations. These 
pressures are based on the maximum recorded 3-second gust wind 
speeds at each location, using the latest code method of wind pressure 
determination in effect at each location. The resultant pressures range 
from 5 percent to 40 percent below the current design pressures, con
firming 
that this was not a code level wind event with respect to the 
2001 FBC or 2000/2003 IBC. However, it is important to note that in 



most cases, the actual pressures are in the same range as the 1997 SBC 
design pressures. These wind provisions were first introduced in the 
1982 edition of the SBC and were largely unchanged through the 1999 
SBC. Therefore, it is reasonable to expect that a significant number 
of buildings in the damage zone should have been built to withstand 
design pressures in the range of what was experienced in Hurricane 
Ivan. Considering the amount of wind damage observed by the MAT, it 
is evident that under-prediction of the design wind loads by past build
ing 
codes for critical building areas such as roof and wall corners led 
to significant building envelope damage and may have led to some of 
the structural damage observed. However, investigation of the damage 
observed suggests compliance of the construction with the building 
codes was a much bigger factor. 

Some elements of buildings constructed under older codes were vul
nerable 
to damage because of the lack of specific provisions for those 
elements. Building envelope components such as roof coverings have 
much more stringent requirements in the current codes. Rooftop 
equipment and protection of glazing, for example, were largely ignored 
in older codes. Other failures were the result of installed materials and 
systems that are known to lack the ability to perform under high-wind 
loads (i.e., the use of unsecured soffit panels). These components either 
do not meet the new criteria or there is a lack of clear evidence that the 
product will work under high-wind loads. Because these components 
are not considered structural elements, their design and construction 
is often overlooked during design permitting, construction, and inspec
tion. 
Therefore, improvements are needed in the design requirements 
of the codes themselves and in enforcement and code compliance to 
ensure that component and cladding (C&C) elements are being engi
neered 
and designed per the code requirements. 

For the State of Florida, the 2001 FBC and the recently completed 
2004 FBC (to be adopted statewide by administrative rule effective Oc
tober 
1, 2005) include several improvements to the structural design 
of buildings and attached structures, as well as improvements for the 
design of building envelope and equipment provisions. Based on the 
observations outlined in this report, design guidance provided by the 
code with regard to the design and construction of the building en
velope 
and attached structures and equipment needs to be expanded 
and improved. Guidance for some of these issues is provided by cur
rent 
model codes and standards, including the IBC/IRC, NFPA 5000, 
and ASCE 7. 



Table 7-1. Design Wind Pressures Building Code 

Equivalent 
Design Wind 
Speed
(3-second 
gust) 

Building Surface / Function 

Exterior Walls 

4 in 12 Roof Pitches 

Main Frame 

Components 
and Cladding 

Main Frame 

Components 
and Cladding 

Single Family Residence in Gulf Shores, Alabama 

Standard Building Code 
1979 Edition1,2,3 

130 mph 

+33 psf 

+/- 27 psf 

-25 psf 

- 23 psf 

Standard Building Code 
1997 Edition1,2,3 

115 mph 

+32 psf 

+25/-29 psf 

-26 psf 

+15/-52 psf 

International Building Code 
2003 Edition1,2,5 

145 mph 

+46 psf 

+38/-51 psf 

-40 psf 

+22/-73 psf 

Actual Maximum 
Recorded Wind Speed1,2,4,6 

109 mph 

+23 psf 

+29/-39 psf 

-31 psf 

+16/-68 psf 

Single Family Residence in Perdido Key, Florida 

Standard Building Code 
1979 Edition1,2,3 

125 mph 

+30 psf 

+/- 25 psf 

-23 psf 

- 21 psf 

Standard Building Code 
1997 Edition1,2,3 

110 mph 

+31 psf 

+24/-28 psf 

-25 psf 

+14/-50 psf 

Florida Building Code 
2001 Edition1,2,5 

135 mph 

+40 psf 

+33/-44 psf 

-35 psf 

+19/-63 psf 

Actual Maximum 
Recorded Wind Speed1,2,4,6 

119 mph 

+31 psf 

+25/-34 psf 

-27 psf 

+14/-49 psf 





psf = pounds per square foot 

1 The pressure calculations under each code for both main frame and components and cladding were calculated 
using building design coefficients in wind zones that provide the maximum wind pressure for any area on that 
building surface. 

2 Positive value pressures indicate pressures acting inward toward building surfaces. Negative value pressures 
indicate pressures acting outward from building surfaces. 

3 Pressures calculated from the 1979 and 1997 SBC were calculated using their appropriate fastest-mile wind 
speed and design methods in the code that was in effect at the time. The 3-second gust wind speed is shown for 
comparative purposes only and was not used in the calculation of the design wind pressures. 

4 Assumed Exposure Category C. 

5 Assumed Exposure Category B. 

6 Actual maximum recorded wind speeds were measured in 3-second gust speeds. Pressures were calculated 
under the current code for that location (IBC or FBC). 



7.2.2 Performance of Structural Systems (Residential and 
Commercial Construction) 

Buildings designed and constructed to resist wind loads prescribed in 
the 2001 FBC and to the requirements of ASCE 7 performed well and 
showed how improvements to the building codes have been successful 
in Florida. Adoption of the IBC in Alabama communities was so recent 
that few buildings had been constructed under those provisions; how
ever, 
the same results as those in Florida are expected. Throughout 
the Hurricane Ivan damage zone, structural wind damage was com
mon 
in certain construction types, at wind pressures 5 to 40 percent 
below design level in the code. The most prevalent construction type 
experiencing structural damage was residential wood roof framing. 
Inadequate nailing of roof sheathing panels, gable end wall failures, 
and lack of properly installed wood framing connectors were the major 
factors in these structural failures. Pre-engineered metal building struc
tures 
suffered significant damage, particularly to older buildings. 

7.2.2.1 Internal Pressures 

Breach of the building envelope through broken windows, failed doors, 
or loss of sheathing led to significant changes of the internal pressures 
in buildings, which sometimes resulted in structural damage. Research 
suggests that internal pressures are affected by openings as small as 1 
percent of the wall area and that the internal pressure generally be
comes 
equal to the external pressure at the opening when the area 
of the opening reaches or exceeds 5 percent of the wall area. Conse
quently, 
the loss of a large window, a sliding glass door, a double-entry 
door, or a garage door can expose the interior of a building to the 
full effect of the external wind pressure. When openings are breached 
on the windward face of the building by direct pressure-related fail
ure 
or by impact from windborne debris, the internal pressure in the 
building rises toward and tends to follow the fluctuations in positive 
pressure that would have occurred on that window, door, or panel 
had it not failed. Because air is essentially incompressible at the wind 
speeds encountered in even the most severe wind storms, the pressure 
builds without the need for much wind flow through the opening. 
However, if other openings in the building are present, including pan
els 
covering ceiling access holes in attics, air pressure can escape from 
the building, but does so as rapidly moving air that whips through 
the building. Failures of windows and doors on the windward face of 
a building have been correlated with subsequent failures of partition 
walls, doors, and windows on side and leeward walls, attic access pan
els, 
roof sheathing, and even whole roof structures (refer to Chapter 4 
for details of these types of failures). 



The MAT observed window failures that resulted in interior parti
tion 
failure and failure of exterior walls, as seen in Figures 7-8 and 
7-9 (this failure is fully described in Subsection 5.5.1. The MAT saw 
other examples where wall materials or framing in the gable end 
walls failed, causing the attic space to become pressurized. In some 
cases, the pressurized attic pushed off the roof sheathing. In other 
cases, the pressurized attics failed the ceilings below them, pressuriz
ing 
the interior spaces, and caused failures in the building envelope 
from the inside. 

Figure 7-8. 
Window damage caused 
exterior wall failure 
(Gulf Shores) 


Internal and external pressures combined 
to cause exterior wall failure 

Window breaches caused 
an increase in internal 
pressure 



7.2.2.2 Wind Mitigation for Existing Buildings 

To minimize damage or prevent failure of older buildings (residen
tial, 
commercial, and critical/essential facilities), mitigation to create 
a continuous load path from the roof to the foundation must be im
plemented. 
This type of mitigation can be expensive because it often 
requires partial demolition and replacement of interior building 
finishes, and may require displacement of occupants while the mitiga
tion 
is performed. Justifying the cost may also be difficult because the 
building code or local ordinance may not require that the building be 
upgraded to current code requirements. 

For homeowners, opportunities to perform mitigation retrofits that 
improve the buildings continuous load path would be during reno
vation 
work or during roof replacement projects, when significant 
invasive work is already being performed and the cost to install extra 
clips, screws, or nails to secure decking to rafters/trusses would be 
minimized. Access to the roof structure/top of wall connection is of
ten 
made accessible during these projects, and clips and straps may 
be installed to help with the creation of a continuous load path. Ad
ditional 
anchorage of the bottom of the walls may still be required to 
develop a complete load path. Mitigation projects stated above would 
address much of the roof decking and roof structure failures observed 
after Hurricane Ivan. 


Figure 7-9. 
Partition walls destroyed 
by interior pressurization 
due to window damage 
(Gulf Shores) 



In commercial, government, and critical/essential facility buildings, 
mitigation retrofit costs may be minimized if these types of projects 
are performed during tenant fit-out projects or during major capital 
improvement projects. Prioritization can be given to mitigating space 
used for critical and essential functions. Public schools are examples of 
places where these types of mitigation projects have occurred. As part 
of their efforts to increase safe public shelter space, FL DCA has evalu
ated 
schools, and sponsored structural and non-structural mitigation 
projects to strengthen buildings and provide debris impact protection 
to mitigate existing buildings that were once vulnerable to damage 
from wind and windborne debris. 

7.2.3 Performance of Building Envelope, Mechanical and 
Electrical Equipment 

Although structural system failures tend to be perceived by the public 
and the building industry as the dominant issue of concern, the great
ly 
improved houses built in accordance with the FBC 2001 and other 
model codes have, in general, resolved most structural issues. Now, the 
arena in which improvements can and must be made are those related 
to water intrusion and protection of the building envelope (refer to 
Chapter 5). Protection of the building envelope is important in mini
mizing 
losses and damages to building contents, but also because of 
the importance of the building envelope with respect to internal pres
surization 
of a building. 

Poor performance of building envelopes and rooftop equipment was 
common on residential, commercial, and critical/essential buildings. 
Envelope and equipment damage was more widespread and signifi
cant 
on older buildings, although new buildings were also damaged. 
Damage was noted throughout all areas observed. Ramifications of 
poor performance include the following: 

 Property damage. Property damage was extensive, requiring repair 
and/or replacement of the damaged envelope and equipment 
components; repair and/or replacement of interior building 
components; and mold remediation and furniture and equipment 
replacement as a result of rainwater and/or wind damage in 
the interior of the building. Even when damage to the building 
envelope or equipment was limited, such as blow-off of a portion of 
the roof covering or broken glazing, substantial rainwater damage 
frequently resulted because of the heavy rains accompanying the 
hurricane and rains occurring in the following days and weeks. 
Rainwater entered the buildings through the breaches in the 
building envelope. 



 Loss of function. Depending upon the magnitude of the wind and 
rainwater damage, repairs can take days or months. As a result, 
residents may not be able to return home, businesses may not be 
able to reopen, and critical/essential facilities may be incapable 
of providing their vital services. In addition to the costs associated 
with repairing the damage and/or replacing the damaged 
property, other financial ramifications related to interrupted use 
of the building can include rental costs of temporary facilities or 
lost revenue due to business interruption. These additional costs 
can be quite substantial. 

Building Envelope 

Poor performance was a function of both inadequate wind resistance 
and damage from windborne debris impact. Inadequate resistance to 
high-wind pressures on building envelopes and rooftop equipment 
was responsible for much of the damage caused by Hurricane Ivan. In 
addition, windborne debris caused significant envelope damage (and 
virtually all of the glazing damage) that the MAT observed. Damaged 
and fallen trees, and failed building envelope components and roof
top 
equipment (such as roof coverings, gutters, HVAC equipment, and 
wall coverings) also became windborne debris that damaged the build
ings 
they blew off of, as well as other buildings in the vicinity. 

The importance of the building envelope is illustrated by Figure 7-10. 
Although the structural frame performed well, poor performance of 
the building envelope resulted in significant damage. Balcony railings, 
stucco wall covering, and entire portions of the non-load-bearing walls 
were blown away. Glazing damage was extensive, although as shown in 
Figure 7-10, shutters were successful in preventing damage to those 
windows and glazed doors that were protected. 



Roof Coverings, Wall Coverings, and Soffits 

Observations showed that roof coverings of all types continue to fail 
during hurricane events. Some of these failures were due to the age of 
the coverings (coverings that were never considered for their ability to 
resist design wind loads) while other failures were due to design and 
construction related issues or debris impact. Specifically, these obser
vations 
are as follows: 

 Wind damage to roof coverings and wall cladding was widespread, 
even with wind speeds below design levels. Improved performance 
of roof and wall coverings was generally observed on the newer 
buildings and is likely due to improved codes and standards, 
product and test method improvements, a more educated designer 
and contractor workforce, and reduced detrimental effects of 
weathering (on newer buildings). 


Figure 7-10. 
Although this was a structural success, 
except for the excellent shutter 
performance, this building was an 
envelope failure. 



 The Brick Industry Association (BIA) sponsored research regarding 
windborne debris resistance of brick veneer walls versus walls with 
other coverings. The research demonstrated that brick veneer was 
quite resistant to debris impact. Based on the research BIA states 
that brick provides safety for building occupants and security for 
property. This statement is only true if the brick veneer is not 
blown away. If wind-induced collapse of brick veneer does occur, 
as illustrated in Figures 5-26 and 5-27, the expected protection will 
not be present. 

 As with many other building envelope elements, improved brick 
veneer design guidance and workmanship are needed. 

 In general, EIFS performed very poorly. For many buildings, the 
poor performance resulted in significant rainwater infiltration 
damage (see Figure 7-11). Much greater attention is needed in the 
design and application of EIFS, and improvements are needed in 
design guides and testing. 


Figure 7-11: 
In this EIFS failure, the majority of the gypsum 
board detached from the studs. At some living 
units, the gypsum board on the interior side of the 
studs was also blown off, thus exposing the units 
directly to the hurricane. 



 In general, vinyl sidings performed very poorly. The vinyl siding 
industry should evaluate the findings of the MAT and launch 
a program to more fully understand the causes of the poor 
performance. 

 Asphalt roof shingles continued to fail below current design level 
winds. In general, it appeared that shingles installed within the 
past few years performed better than shingles installed prior to the 
mid-1990s. The enhanced performance is likely due to product 
improvements and less degradation of physical properties due to 
limited weathering time. In most cases, observed shingle failures 
were attributed to inadequate self-seal adhesive bond strength or 
installation that did not comply with known methods for resisting 
blow-off in high-wind areas (Figure 7-12). 

 Tile roof systems experienced varied levels of performance from 
complete resistance to wind to substantial loss of tiles. Variation in 
performance was primarily related to installation and attachment 
methods with mortar-set tile system failure most frequently observed. 
Tile failures on roofs with foam-adhesive were observed, in most cases, 
to not comply with manufacturers installation recommendations. 
All types of tile (concrete and clay) are vulnerable to breakage from 
debris impact, regardless of installation methods used. Tiles lifted 
by wind or broken from windborne debris often lead to cascading 

Figure 7-12. 
Rather than cutting off 
the tabs, the starter 
course on this new roof 
was turned 180 degrees. 
Hence, the tabs of the 
first row were free to lift 
because they were not 
adhered in the self-seal 
adhesive on the starter. 



failures (Figure 7-13). Tiles on hips, ridges, and edges of the roof 
were a frequent point of failure. Hip and ridge tiles rarely were 
attached using mechanical anchors. 

 Aggregate roof surfacing continued to cause debris damage when 
aggregate was displaced by high winds, becoming windborne 
missiles. 

 For all roof systems, inadequate attention was typically given to edge 
flashing, coping, and gutter/downspout design and installation 
despite being located in the roof areas subject to the highest wind 
pressures. Failure of these roofing components often initiated roof 
membrane lifting and peeling. 

 Wall cladding appeared to have typically received minimal attention 
during design and construction, and continues to be an initiation 
point for progressive failures leading to interior contents damage 
or pressurization of the building interior. 

 In numerous buildings, rain was driven into attic spaces because of 
soffit failures. Widespread loss of soffits was observed in residential 
construction. In many of these instances, water intrusion occurred 
from wind-driven rain through areas where soffits were displaced 
or lost. 

Figure 7-13. 
These batten-attached 
tiles were damaged by 
windborne debris. Much 
of the damage was 
caused by tile impacting 
other tiles. A tile was 
blown 140 feet from this 
building. 



Windows, Doors, and Shutters 

Windows and glazed doors can be protected in all wind regions us
ing 
shutter systems, laminated glazing systems, and other means of 
opening protection. The required protection of these openings in 
areas within the ASCE 7 windborne-debris region appeared justified 
from the amount of observed debris. (However, the lack of a FBC 
windborne debris region in the Florida Panhandle does not appear 
to be justified.) Using glazing protection to prevent full internal pres
surization 
and to protect interior contents from being damaged is an 
effective means of damage reduction for all hurricane-prone regions. 
Specifically: 

 Many homes and businesses that experienced only contents 
damage could have prevented these losses if their openings were 
protected. Success in designing the structural frame to resist wind 
loads and internal pressures was partially negated by significant 
losses to building contents (Figure 7-14). 

 Most shutters observed on buildings during Hurricane Ivan per
formed 
well. 

 In the ASCE 7 windborne-debris regions, unprotected glazing located 
with the first few floors above grade is typically more susceptible to 
breakage than glazing located several stories above grade. This is 
due to the greater quantity of windborne debris at lower elevations. 
However, as illustrated by Figure 7-15, glazing in tall buildings can 
also be broken. Breakage at upper levels can be caused by dislodged 
roof coverings, rooftop equipment, balcony railings or wall coverings 
from the building or an adjacent building. However, as discussed in 
the ASCE 7 C6.59 Commentary, the greatest threat to upper-level 
glazing is the presence of aggregate roof surfacing on the building 
or other buildings within 1,500 feet. 

 If aggregate roof surfaces do not occur within the parameters given 
in ASCE 7, then for most buildings, glazing protection above 60 feet 
above grade is generally not needed (although isolated damage 
may occur as shown in Figure 7-15). On some critical or essential 
facilities, as a very conservative measure, protecting glazing above 
60 feet may be prudent. For these buildings, a special evaluation, 
including consideration of the basic wind speed, characteristics and 
proximity of other buildings, and characteristics of the building 
being considered should be conducted to determine if glazing 
protection above 60 feet is appropriate. 



Figure 7-14. 
Glazing at the top two window units broken 
by debris, while the entire middle window unit 
was blown away. The shuttered window unit 
was not damaged. 



Attached Equipment (Rooftop and Ground Level) 

Much like the building envelope systems already discussed, rooftop 
and ground level equipment is not typically receiving the design, 
installation, or code attention needed. Design guidance in ASCE 7 
provides basic information to calculate wind loads on these elements 
to determine connection and support anchoring systems, but detailed 
guidance is needed. The lack of design and installation attention re
sulted 
in displacement or damage to these units across the wind field 
of the hurricane. This not only resulted in the loss of function asso
ciated 
with the damaged units, but in many cases led to the loss of 
function of the occupied space due to rainwater infiltration at the dis
placed 
equipment. 


Figure 7-15. 
A few of the upper level windows were 
broken. 



7.2.4 The Need for High-Wind Design and Construction 
Guidance 

Designers, contractors, and building officials need additional education 
and resources. Although many successes of design and construction 
were observed across the path of Hurricane Ivan, it was apparent 
that the load path concept was often not fully understood. It was also 
clear that many designers, contractors, and building officials do not 
fully understand the devastating effects that hurricanes can have on 
building envelopes and equipment. It was common to see fasteners 
spaced too far apart, fasteners that were too small, and fasteners with 
weak connections. Enhanced details were seldom seen. In contrast, 
there were numerous examples of failure to follow well established 
basic construction practices such as minimum edge distances for fas
teners. 
Unless wind resistance issues are understood by designers and 
contractors, envelope and equipment failures will continue to occur. 
In part, the envelope and equipment problem is due to lack of highwind 
design guides for various envelope assemblies and various types 
of rooftop equipment. 

7.2.5 Performance of Critical and Essential Facilities 
(Including Shelters) 

Critical and essential facilities must remain operational before, during, 
and after significant events, such as hurricanes, in order to serve their 
communities. As stated in Chapter 6, buildings that are considered 
critical and essential facilities include EOCs, fire and police stations, 
hospitals, shelters, and schools. 

In general, buildings functioning as critical and essential facilities did 
not perform significantly better than their commercial-use counter
parts. 
Despite codes of the past ten years that require higher design 
loads be used in the design of these facilities, the same flaws in construc
tion, 
such as poor wall cladding, poor attachments of roof covering, 
and improper anchorage of rooftop mechanical equipment, were ob
served 
in critical and essential facilities. As a result, the operations and 
response at many essential and critical facilities discussed in Chapter 6 
were hampered or shut down and taken off-line after the hurricane. 

Most critical and essential facilities in the impacted area were housed 
in older existing buildings and most, if not all, apparently were not 
mitigated to resist known hurricane risks. If key areas of the build
ings 
had been mitigated or retrofitted for wind and windborne debris 



design requirements that are specified in the current code, building 
damage and loss of function would have been reduced. 

The building damage to critical and essential facilities experienced 
during Hurricane Ivan led to a significant, and avoidable, loss of func
tion. 
Specific conclusions for critical and essential facilities based on 
these observations are as follows: 

 When older buildings are used as critical and essential facilities, 
damage will likely occur to the roof covering, wall coverings, 
window and door systems, and rooftop equipment. This damage 
leads to significant loss of function at the facilities (Figure 7-16). 

 Some buildings designed to critical and essential facility 
requirements experienced damage and partial failures during the 
hurricane due to lack of protection from windborne debris. Lack 
of protection of windows was common at hospital and medical 
office buildings, and led to window failures and severe damage to 
building contents. 

 Rooftop equipment loss such as loss of HVAC units and vents, 
antennas, communication dishes, and lightning protection systems 
was prevalent. In almost all cases, these failures caused damage to 
roof coverings that often resulted in rainwater intrusion into the 
facilities (Figure 7-17). 

Figure 7-16. 
An older hospital that 
experienced blown off 
roof coverings, gutters, 
downspouts, rooftop 
equipment (including 
lighting protection 
system components), and 
broken glazing 



 Windborne debris could injure or kill first responders at EOCs, 
late arrivers at shelters, or those seeking medical attention at 
hospitals. Although people are not usually outdoors during 
hurricanes, buildings used as essential and critical facilities can be 
the exception. It is common for people to arrive at these facilities 
during a hurricane and additional efforts should be made to reduce 
the potential for windborne debris at these sites. 

 ARC 4496 provides a baseline for a shelters integrity and 
performance, but meeting this criterion does not guarantee that 
the building will resist wind and windborne debris associated with 
all hurricanes. 

 Peer review of the design of critical and essential facilities would 
greatly improve the likelihood that a building has been adequately 
designed to resist extreme winds. 

 Special inspections for key structural items and connections, and 
for installation of envelope components would help ensure the 
performance of critical and essential facilities 

Figure 7-17. 
Rooftop mechanical 
equipment damage at a 
hospital. Several of the 
equipment screen panels 
were blown away. Loose 
panel debris can break 
glazing and puncture roof 
membranes. 



T 


C H A P T E R 8 

8-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

8 

Recommendations 

The recommendations in this report are based solely on the observa
tions 
and conclusions of the MAT, and are intended to assist FEMA, 
the States of Alabama, and Florida, local communities, businesses, and 
individuals in the reconstruction process and to help reduce dam
age 
and impact from future natural events similar to Hurricane Ivan. 
The general recommendations presented in Sections 8.1 (for flood) 
and 8.2 (for wind) relate to policies and education/outreach that are 
needed to ensure that designers, contractors, and building officials 
understand the requirements for disaster resistance construction in 
hurricane-prone regions. 

8.1 Flood Related Recommendations 

The most severe flood-related damages experienced during the 
2004 hurricane season were associated with Hurricane Ivan. 
Recommendations and tables summarizing key recommenda
tions 
are provided below: 

8.1.1 General Hazard Identification Recommendations 

 Re-evaluate the hazard identification/mapping approaches in 
coastal AE/VE Zones  Re-evaluate the methodology to determine 
flood zones and flood elevations in coastal areas, to address the 
inconsistencies between observed flood elevations (and damages) 
and BFEs (and anticipated damages). Re-evaluate the criteria 
for determining the AE/VE Zone boundary, which currently is 
based on a 3-foot wave. Areas subject to waves of 3 feet or higher 



C H A P T E R 8 

RECOMMENDATIONS 

8-2 

 MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

are considered V Zones. Flood hazard mapping procedures and 
methodologies in coastal areas (especially on barrier islands, and 
on mainland, open coast shorelines) may need revisions to capture 
anticipated future coastal conditions (for instance, the possible 
effects of multiple storm events and long-term erosion). 

 Re-evaluate the storm surge modeling  Review the storm surge data 
and modeling procedures that served as the basis for the effective 
FIRMs. Updates after Hurricane Opal (1995) were limited and did 
not affect areas north of Highway 98 in Escambia County. Conduct 
a revised tide frequency analysis, update storm climatology for the 
area, and utilize modern storm surge models to estimate the BFEs 
throughout the Ivan impact area. 

 Reconstruction Guidance  Use Hurricane Ivan tide levels, in
undation 
limits, and areas subject to wave effects as proxies for 
reconstruction guidance until such time as new, up-to-date regula
tory 
studies and maps can be prepared and adopted. 

8.1.2 Design Guidance 

 Although not mandated by the IRC or the FBC, utilize ASCE 24-05 
for flood-resistant design of one- and two-family structures (the IBC 
references ASCE 24, but the IRC does not). Design and construction 
practices specified in ASCE 24-05 will result in flood- and erosionresistant 
foundations throughout coastal areas (not just V Zones) 
and the addition of freeboard to the lowest floor elevation, utility 
equipment that is protected from the flood damage, and the use of 
flood-resistant materials below the BFE. 

 Use ASCE 7-05, Section 5.3 and the associated Commentary, for the 
calculation of flood loads during the base flood. The Commentary 
provides guidance for characterizing and calculating floodborne 
debris loads. 

 Use the Home Builders Guide to Coastal Construction Technical Fact 
Sheets (FEMA 499) and the Coastal Construction Manual (FEMA 
55) for additional guidance related to flood- (and wind-) resistant 
design and construction. 

8.1.3 Foundation Recommendations 

 Elevate the bottom of the lowest structural member above the 
BFE for coastal A Zones  Elevate all new construction (including 
substantially improved structures and replacement of substantially 
damaged structures) in coastal A Zones with the bottom of the 



RECOMMENDATIONS 

lowest horizontal supporting member above the BFE. This is a 
higher standard than the NFIP minimum requirement, which calls 
for only the top of the lowest floor (walking surface) to be at or 
above the BFE. 

 Freeboard  Require freeboard for all structures in all flood hazard 
zones with the amount varying with building importance (see ASCE 
7-05 and ASCE 24-05 for building importance classification and 
freeboard requirements) and anticipated exposure to wave effects 
(see Figure 8-1). When using pile foundations, elevate the lowest 
floor a minimum of one story above grade to allow for parking and 
storage, which is the current practice by some builders. 

 V-Zone standards  Require V-Zone design and construction for 
new construction in coastal A Zones subject to erosion, scour, 
velocity flow, and/or wave heights greater than 1.5 feet. 

 Foundations on barrier islands  Use a deep pile and/or column 
foundation anywhere on a barrier island  including B, C, and X 
Zones  if erosion/or scour are possible. Use of other foundation 
types should be limited to those areas far outside the SFHA, not 


Figure 8-1. Freeboard and open foundations are recommended for V Zones and coastal A Zones. 



subject to future flooding if dunes or other natural protective 
features are lost and not subject to erosion or scour. Other 
foundation types should be the exception, not the rule. 

 Foundations near bay/sound shorelines  For sites near bay or 
sound shorelines, foundation selection should be based on several 
factors: erodibility of the soil; exposure to damaging waves 
(=1.5 feet high); potential for velocity flow; potential for floodborne 
debris; and required resistance to lateral flood and wind forces. 
Aside from the lateral resistance issue, which will probably be a 
function of wind loads, Table 8.1 should be used to help select the 
appropriate foundation near bay/sound shorelines. 

Table 8-1. Recommended Foundations for Coastal Areas near Bay/Sound Shorelines and Not Mapped as V Zone
Foundation Type 

Base Flood Condition Present 

Erodible Soils, 
Base Flood 
Inundation 
Possible 

Wave Heights 
between 1.5 and 
3.0 Feet* 

Velocity Flow 

Large Debris 

Fill 

no 

no 

no 

no 

Slab on grade 

no 

no 

no 

no 

Crawlspace, shallow footing 

no 

no 

no 

no 

Foundation walls, shallow 
footing 

no 

no 

no 

no 

Stemwall, shallow footing 

no 

yes 

no 

yes 

Stemwall, deep footing** 

yes 

yes 

yes 

yes 

Pier, shallow footing 

no 

yes 

no 

no 

Pier, deep footing** 

yes 

yes 

yes 

no 

Post, shallow embedment 

no 

no 

no 

no 

Pile/Column, deep 
embedment** 

yes 

yes 

yes 

yes 

* wave heights greater than 3.0 ft mapped as V Zone: fill, slab, crawlspace, wall foundations not permitted 

** deep means sufficiently deep to withstand erosion and scour, including that induced by the presence of the 
foundation itself 







Absent a detailed study for a site, exposure to damaging waves = 1.5 
feet can be estimated based on three factors: 

 Fetch (during the base flood) from the bay/sound shoreline 
across the water body. If the fetch is less than 1 mile, the potential 
for generation of damaging waves is low; if the fetch is 1 mile or 
greater, assume damaging waves can be generated. 

 Stillwater depth at the site, after accounting for erosion. If the 
stillwater depth is 2 feet or greater, sufficient depth exists to allow 
passage of 1.5-foot waves; if the stillwater depth is less than 2 feet, 
waves may be present but should be less than 1.5 feet high. 

 Obstructions between the site and the shoreline. If dense stands of trees 
or buildings/structures capable of withstanding the base flood occur 
between the site and the shoreline, it is reasonably safe to assume the 
height of any damaging waves will be reduced; if these obstructions do 
not exist (or if they exist but their future existence is questionable), 
assume the wave heights will not be reduced appreciably. 

Pier foundations should be used only where soil characteristics and 
flood conditions permit, and where their design and construction are 
consistent with the details shown in Figure 8-2. Although this is a com
mon 
foundation type, its performance in coastal areas has been poor 
where erosion, waves, and/or debris are present. 


Figure 8-2. Recommended design details 
for masonry piers where this foundation 
type is appropriate 



Although stemwall foundations (backfilled with a concrete slab on 
top) performed better than many other A-Zone type foundations near 
bay/sound shorelines, their use should be contingent on having foot
ings 
deep enough to withstand erosion and scour, including that due 
to the presence of the foundation itself. 

If there are any doubts as to the appropriate foundation to use near bay 
and sound shorelines, elevate the building at least one story above grade 
on piles or another deeply embedded open foundation, and leave the 
area below free of obstructions or enclose it with breakaway walls. 

 Debris Impacts  Design foundations and structures to withstand 
loads from floodborne debris during a base flood event (100-year). 

 Multi-story Construction  For barrier island sites outside the V 
Zone, the ground level floor of a multi-story building (typically 
used for vehicle parking and building access) should either: 1) use 
a lowest floor slab or floor system that will not collapse and can 
support all design loads, if undermined, or 2) use a slab or floor 
system that will collapse and break into small pieces if undermined. 
For V-Zone sites (on barrier islands and bay/sound shorelines), 
the ground floor system must collapse and break into small pieces 
if undermined. 

8.1.4 Building Utilities 

Electrical wiring and equipment and plumbing should be securely 
fastened to the landward side of an interior piling and should not be 
attached to breakaway walls or in areas exposed to wave and debris 
impacts. 

HVAC equipment should be elevated above the BFE and preferably to 
the same elevation as the lowest floor of the building. The equipment 
should be supported to prevent damage from flooding and fastened 
to resist blow-off from high winds. The preferred approach is a canti
levered 
platform (see Figure 8-3). Other acceptable support systems 
include knee-braced platform supports (with the bottom of knee 
braces above wave and debris impacts), and pile supports (with piles 
substantial enough to resist all flood loads and anticipated erosion and 
scour). Shallow and/or small diameter post or pile supports should 
not be used under any circumstances in coastal flood hazard areas. 



8.1.5 Building Access Structures and Enclosures beneath 
Elevated Buildings 

Although newer buildings elevated on piles that were built to V-Zone 
standards performed well structurally, there were considerable resid
ual 
damages to the lower portions of the buildings to enclosed areas 
and elaborate staircases. These damages could have been avoided or 
at least reduced. Although many of these damages are uninsured and 
the costs of repair borne by the owner, there are some added costs to 
the NFIP, particularly for staircases. In addition, as these enclosures 
and stairways become larger, they are less likely to break away and, 
thus, more likely to become obstructions to flood flows increasing risk 
to the rest of the building. The following guidance is provided: 

 Ensure that breakaway walls are designed and built to break away 
cleanly and do not cause additional damage to the building. Do not 
overlap piles or floor beams with breakaway walls. Provide a clean 
joint between the breakaway wall and the siding on the elevated 
portion of the building. 

 Minimize the size of any enclosed areas to the amount necessary 
for parking and building access. Fully enclosing large areas below 
elevated buildings only increases repair costs and contributes to 
increased risk of debris impacts to the building and other nearby 
homes. 

Figure 8-3. 
A cantilevered platform. 



 Design staircases to provide a reasonable means of safe and 
convenient access to the building. Many of the more elaborate 
staircases on newer buildings were obstructions to flood flows under 
the building and may have contributed to increased damages and 
at a minimum, the repairs are costly. 

 Flood insurance claims for stairs and building access structures 
should be limited to a reasonable fraction of the policy limit. The 
amount should be based on the costs to provide access to the 
building that is safe and convenient, but no more. 

 Flood insurance rating and claims procedures should be modified 
to ensure that ratings and claims payments are accurate and reflect 
the risks, particularly in regard to enclosures and obstructions. 

8.1.6 Pools and Bulkheads 

Post-storm inspections consistently show pool and bulkhead failures and 
building owners need to understand that these will likely be destroyed 
during a major hurricane. The following guidance is provided: 

 Pools  either elevate the pool above the BFE on a pile foundation 
(and design the pool without side support from soil), or install 
a frangible (breakaway) pool at grade level and consider it 
expendable. Do not rely on a bulkhead to protect the pool during 
a severe storm. 

 Bulkheads  subject to local and state regulations for coastal 
armoring, assume that only heavy walls will provide protection 
during a severe storm, and note that even those may be overtopped 
by surge and waves. Consider lightweight bulkheads as temporary 
structures that may provide protection during minor storms, but 
which will likely fail during a major storm. Do not rely on bulkheads 
to protect soil supporting buildings; hence, construct buildings on 
pile foundations even if a bulkhead exists. 

8.1.7 Public Outreach and Education 

Tailor informational pamphlets to homeowners and building owners 
to: 

 Educate about the risks of natural hazards and best practices for 
mitigating damages. 

 Educate about the risk of constructing enclosures and accessory 
structures beneath the first floor and emphasize the significant 
damage that will result during a severe coastal flood event. 



For architects, engineers, consultants, building officials, and contrac
tors, 
prepare monographs for trade-wide distribution, and web-based 
tutorials and seminars. Encourage colleges, universities, and trade 
schools to augment existing curriculum with hurricane-resistant design 
and construction instruction. The following topics can be covered: 

 Share post-disaster building performance information to maximize 
the value of lessons learned. 

 Emphasize best practices such as those in the Coastal Construction 
Manual (FEMA 55) and the Home Builders Guide to Coastal 
Construction Fact Sheets (FEMA 499). 

 Emphasize importance of freeboard and strong structure-to-beam 
connections to prevent structure detachment from the founda
tions. 


 Emphasize the importance of flood- and erosion-resistant founda
tions 
in coastal areas, even if not required by code and floodplain 
management regulations. 

For elected officials, develop outreach efforts that clearly demonstrate 
the value of exceeding minimum floodplain and code requirements: 

 Illustrate the fact that freeboard and V-Zone foundations are critical 
to building survival across entire barrier islands, not just sites near 
the shoreline. 

 Show examples of other communities that have adopted higher 
standards and their experience with those higher standards. 

 Assist elected officials in the revision of floodplain management 
ordinances, development regulations, and building codes to re
duce 
future storm damage. 

Tables 8-2 through 8-5 present the flood-related recommendations de
veloped 
by the MAT and first presented in FEMA 490, Summary Report 
on Building Performance 2004 Hurricane Season, March 2005. Table 8-2 
presents the recommendations for design and construction of build
ings 
and accessory structures. 



Table 8-2. Design and Construction Recommendations
Flood Hazard 

Building 
Component 

Recommendation 

Action Required 
By1 

Design, Foundations and Structures 

Design guidance 

Use ASCE 7-05, section 5.3 for the calculation of flood loads 
during the base flood. 

D, C, G 

Design guidance 

Use ASCE 24-05 for the flood-resistant design of all structures in 
flood hazard areas, including one- and two-family structures. 

D, C, G 

Design guidance 

Use the Home Builder Guide to Coastal Construction Technical 
Fact Sheets (FEMA 499) and the Coastal Construction Manual 
(FEMA 55) for additional guidance related to flood- (and wind-) 
resistant design and construction. 

D, C, G 

Floodborne 
debris 

Design foundations and structures to withstand loads from 
floodborne debris during a base flood event (100-year). 

D, C, G 

Lowest floor 
elevation 

Elevate all new construction (including substantially improved 
structures and replacement of substantially damaged 
structures) in A Zones with the bottom of the lowest horizontal 
supporting member above the base flood level. Freeboard for all 
structures in all flood hazard zones is desirable; the amount will 
vary with building importance (see ASCE 7-05 and ASCE 24-05) 
and anticipated exposure to wave effects. 

D, C, G 

Foundations on 
barrier islands 

Require V-Zone standards for new construction in coastal A 
Zones subject to erosion, scour, velocity flow, and/or subject to 
wave heights greater than 1.5 feet. 

G 

High rise 
foundations on 
barrier islands 

For areas outside the V Zone, the ground level floor of a multistory 
building (typically used for parking or building access) 
should either: 1) use a lowest floor slab or floor system that will 
not collapse and can support all loads or 2) use a slab or floor 
system that will collapse into small pieces. 

For areas within the V Zone, the ground floor system must 
collapse and break into small pieces if undermined. 

D, C, G 

Foundations near 
bay and sound 
shorelines 

For sites near bay or sound shorelines, foundation selection 
should be based on several factors as described in section 8.1.3 
and an appropriate foundation should be selected as outlined in 
Table 8-1. 

D, C, G 

Utilities 

Design and construct to ASCE 24-05. HVAC equipment should 
be elevated above the BFE and should be supported to prevent 
damage from flooding, wave, and debris impacts, and high 
winds. The support system should be a cantilevered platform or 
knee-braced platform with the bottom of the knee braces above 
the wave and debris impacts. 

D, C, G 

Dock and piers 

Implement design requirements for docks and piers that 
minimize damage to other structures. 

D, C, G 







Pools 

Either elevate the pool above the BFE on a pile foundation 
(and design the pool without side support from soil), or install 
a frangible (breakaway) pool at grade level and consider it 
expendable. 

D, C, G 

Bulkheads 

Do not rely on bulkheads to do any more than retain soil under 
normal and minor storm conditions; do not design building 
foundations or other structures that rely on bulkheads to retain 
soil during a base flood event. 

D, C, O 





1 Action required by: Designer (D), Contractor (C), Manufacturer (M), Government 
Official (G), Building Owner (O) 

Table 8-3 presents flood hazard identification and regulations recom
mendations. 


Table 8-3. Hazard Identification and Regulations Recommendations 
Flood Hazard 

Parameter 

Recommendation 

Hazard Identification and Regulation 

Storm surge 

Re-evaluate storm climatology, water-level data, and storm-surge modeling; run 
modern storm-surge models as the basis for determining new BFEs. 

A Zones in coastal 
areas 

Re-evaluate the hazard identification/mapping approaches in coastal A Zones. 

Zones B, C, and X on 
barrier islands 

Re-evaluate flood and erosion hazards associated with areas outside the SFHA 
on barrier islands. 

Open coast future 
conditions mapping 

Flood hazard mapping of open coast areas should account for multiple storm 
events and future conditions (e.g., long-term erosion and sea level rise). 





Table 8-2. Design and Construction Recommendations (continued) 

Flood Hazard 

Building 
Component 

Recommendation 

Action Required 
By1 

Accessory Structures 







Table 8-4. Public Outreach Recommendations 
Flood Hazard 

Education Topic 

Outreach 

Building Owners and Homeowners 

Educate building and homeowners in 
the risks of natural hazards and best 
practices for mitigating damages. 

Use FEMA Home Builders Guide to Coastal Construction Fact 
Sheets (FEMA 499). 

Interview homeowners who have been through recent storms 
(both those whose buildings were not damaged and those 
whose buildings were). Use this information to prepare other 
informational pamphlets/video/web sites aimed at homeowners 
and building owners. 

Educate homeowners on the risk 
of constructing enclosures and 
accessory structures beneath the 
lowest finished floor and emphasize 
the significant damage that will 
result during a severe coastal flood 
event. 

Prepare pamphlet. 

Architects, Engineers, Consultants, and Building Officials 

Architects, Engineers, Consultants 

Distribute information in the areas of post-disaster building 
performance to maximize value of lessons learned. 

Emphasize best practices in Coastal Construction Manual 
(FEMA 55). 

Emphasize the importance of flood- and erosion-resistant 
foundations in coastal areas, even if not required by code and 
floodplain management regulations. 

Emphasize importance of freeboard and strong structure-tobeam 
connections to prevent structure detachment from the 
foundations. 

Building Officials 

Same as Architects/Engineers/Consultants, plus: 

Develop educational programs for annual seminars, specially 
designed to share lessons learned and receive training to 
address potential permitting/enforcement problems. 

Encourage building officials to obtain the new certification 
(coastal building inspector) being offered by ICC after July 2005. 





Table 8-4 presents recommendations to alert the public to the flood 
hazard. 



Educate elected officials on how 
to best design buildings for barrier 
islands. 

Pamphlets, videos showing side-by-side photos and discussion 
of freeboard vs. elevating to BFE, V-Zone foundations vs. A-Zone 
foundations in coastal A Zones 

Show elected officials examples 
of other communities that have 
adopted higher standards and 
their experience with those higher 
standards. 

Interview community officials from communities that have 
adopted higher standards  what are the advantages and 
disadvantages of doing so? How much damage has been 
avoided in recent storms? 

Develop relationships with organizations of elected officials 
(county commissioners associations, league of cities, etc.), and 
get on the agenda for their national/state meetings  promote 
higher standards. 

Assist elected officials in the 
revision of floodplain management 
ordinances, development regulations, 
and building codes to reduce future 
storm damage. 

Obtain/prepare model ordinances, development regulations, and 
code revisions that mandate higher standards. 

Contractors 

Share post-disaster building 
performance information to 
maximize the value of lessons 
learned. 

Emphasize best practices such as 
Coastal Construction Manual (FEMA 
55) and Home Builders Guide to 
Coastal Construction (FEMA 499). 
Emphasize importance of strong 
structure-to-beam connections to 
prevent structure detachment from 
the foundations while piles and 
beams are still intact. 

Prepare monographs for trade-wide distribution. Prepare webbased 
tutorials and seminars. Encourage colleges, universities, 
and trade schools to augment existing curriculum with 
hurricane-resistant design and construction instruction. 





Table 8-4. Public Outreach Recommendations (continued) 

Flood Hazard 

Education Topic 

Outreach 

Elected Officials 







The flood hazard recommendations in Table 8-5 are specific to critical 
and essential facilities. 

8.2 Wind Recommendations 

As the people of southern Alabama and northwestern Florida re
build 
their lives, homes, and businesses, there are a number of 
steps they can take to lessen the impact of wind damage from 
future natural hazards, including: 

 Design and construct facilities to at least the minimum design 
requirements in the 2003 IBC in Alabama and the 2001 FBC and 
the 2004 FBC (after it becomes effective in the summer of 2005) in 
Florida. 

 When renovating or remodeling for structural or building envelope 
improvements (both residential and commercial), involve a 
structural engineer/design professional/licensed contractor in 
the design and planning. 

 Assure code compliance through increased enforcement of 
construction inspection requirements such as the Florida Threshold 
Inspection Law or the IBC Special Inspections Provisions. 

 Perform follow-up inspections after a hurricane to look for moisture 
that may affect the structure or building envelope. 

 Use the necessity of roof repairs to damaged buildings as an 
opportunity to significantly increase the future wind resistance of 
the structure. 

Table 8-5. Recommendations Specific to Critical and Essential Facilities
Flood Hazard 

Parameter 

Recommendation 

Action Required 
By1 

Critical/Essential Facilities 

Public shelters 

Do not open shelters located in potential storm-surge inundation 
zones until after the hurricane makes landfall. 

G, CFO 

New structures 

Elevate new structures in floodprone areas to the 500-year (0.2% 
annual exceedance) flood level or higher based on ASCE 24. 

D, G, CFO 

Existing 
structures 

Evaluate vulnerability of existing structures in light of recent 
damage to similar facilities; strengthen and floodproof structures 
where feasible. 

G, CFO, D 





1 Action required by: Designer (D), Government Official (G), Critical Facility Manager/Owner (CFO) 



The following recommendations are specifically provided for state and 
Federal government agencies: 

 The government should place a high priority on and allocate 
resources to hardening, and providing backup power and data 
storage to NOAA/NWSs surface weather monitoring systems, 
including the ASOS located in hurricane-prone regions. Continued 
support is also needed for maintenance, expansion and deployment 
of stand alone unmanned surface observation systems that can be 
safely and reliably placed in advance of a land falling hurricane. 
Support should be provided for the real-time communication of 
data from all these platforms to forecasters and wind field modeling 
efforts. 

 The government should place a high priority on continuing to 
fund the development of several different tools for estimating and 
mapping wind fields associated with hurricanes and for making 
these products available to the public as quickly as possible after a 
hurricane strikes. 

8.2.1 Proposed Changes to Codes and Statutes 

Buildings constructed in accordance with 2001 FBC (and those that 
had been mitigated to resist high-wind loads) were observed to per
form 
substantially better than typical buildings constructed to earlier 
codes, but their positive performance was not without exception. The 
study of buildings and their interaction with high winds associated with 
hurricanes is a continuous process and much has been learned since 
the current codes and statutes were developed and adopted. Incorpo
rating 
the recommendations in this report into the next available code 
cycle is key to setting the new standard in hurricane-resistant construc
tion 
in Alabama, Florida, and all hurricane-prone regions. 

Subsections 8.2.1.1, 8.2.1.2, and 8.2.1.3 provide recommendations spe
cific 
to the codes and statutes currently adopted and being enforced in 
the States of Alabama and Florida. If these recommendations are not 
codified by the states in response to the hurricanes of 2004, the design 
changes recommended herein should be considered best practices 
in hurricane-resistant construction and incorporated in all new con
struction 
and mitigation projects as a discretionary matter. 

8.2.1.1 Statutory Building Code Provisions  Alabama 

 Adopt the 2003 IBC and IRC for all high-wind jurisdictions in the 
state. 



 Do not modify the wind provisions of the IBC/IRC and ASCE 7-02 
with local amendments that suspend some of the provisions, such 
as windborne debris protection. 

 Require the use of high wind provisions for residential construction 
in wind zones of 100 mph and greater. The current 2003 IRC 
requirement is 110 mph; however, the IRC Code Development 
Committee has approved a code change proposal for the 2006 
version lowering the threshold to 100 mph. 

 Review the exemption in windborne debris regions that allows for 
residences to be designed as partially enclosed structures with 
unprotected openings. The MAT observed instances where the 
breach of unprotected glazing led to significant damage to building 
contents that would have been prevented if the damaged buildings 
had been equipped with protected glazing to resist windborne 
debris. The next version of the IRC does not allow for the design of 
partially enclosed structures without protecting glazing. The IBC 
Structural Code Development Committee has approved a code 
change proposal for the 2006 version eliminating the partially 
enclosed option. Based on observed damages in Hurricane Ivan, 
this exemption should not be allowed for any use (residential or 
commercial) in windborne debris regions. 

8.2.1.2 Statutory Building Code Provisions - Florida 

The following design criterion is recommended for inclusion into 
statewide design requirements for all construction. The criteria are 
addressed in Ch. 553.71 and Ch. 2000-141 of the Laws of Florida (and 
presented in Section 2.2 of this report). 

 Review the exemption in windborne debris regions that allows for 
residences to be designed as partially-enclosed structures with 
unprotected openings. The MAT observed instances where the 
breach of unprotected glazing led to significant damage to building 
contents that would have been prevented if the damaged buildings 
had been equipped with protected glazing to resist windborne 
debris. The next version of the IRC does not allow for the design of 
partially enclosed structures without protecting glazing. The IBC 
Structural Code Development Committee has approved a code 
change proposal for the 2006 version eliminating the partially 
enclosed option. Based on observed damages in Hurricane Ivan, 
this exemption should not be allowed for any use (residential or 
commercial) in windborne debris regions. 



8.2.1.3 Reference Standards  ASCE 7 

All of the various building codes that govern the areas within the Ivan 
damage zone in one way or another reference ASCE 7 for wind loads. 
Within that standard is Table 1-1, which classifies buildings based on 
occupancy. This classification is used to determine the importance fac
tors 
for wind, snow, and earthquake loads. The Ivan MAT discovered a 
loophole in this system of classification that needs to be examined by 
the ASCE 7 committee. The loophole was evident in the classification 
of various buildings on hospital campuses. Using Table 1-1, an MOB 
would be classified as a Category II building because it has no patients. 
Further, the table requires a patient bed count of 50 beds or more to 
move the building up to a Category III building, thus invoking the 
1.15 safety factor. However, the MAT observed instances where clinical 
functions essential to the treatment of the community were housed in 
MOBs attached to the hospital. One example of this was a large dialy
sis 
clinic housed in an MOB. Although the building sustained major 
building envelope damage, it was able to quickly make temporary re
pairs 
and restore services. This could have easily not been the case, 
and many patients would have been denied treatment. Immediately af
ter 
a hurricane, movement and access are problematic at best; hence, 
requiring patients to travel to more distant locations to receive life sus
taining 
treatments is more than a mere inconvenience. Consideration 
should be given to changing Table 1-1 to include in Category III those 
buildings that house essential clinical treatment functions that are not 
easily available elsewhere in the community. 

Designers should take care when classifying some facilities that pro
vide 
care, such as nursing homes. For example, skilled nursing homes 
and Alzheimers facilities should be Category III, but an assisted living 
facility might suitably be classified as Category II. Also, the occupancy 
trigger should be reexamined. A skilled nursing home or Alzheimer 
facility should be Category III regardless of the number of patients. It 
is, therefore, also recommended that the ASCE committee examine 
Table 1-1 with respect to nursing homes. 

8.2.2 Architectural, Mechanical, and Electrical 

To improve the performance of the building envelope and rooftop 
equipment, the following action items are recommended in addition 
to the code revisions identified previously. 

 Sheathing on the Underside of Elevated Buildings. Preservativetreated 
plywood is recommended in lieu of gypsum board and 
vinyl siding. It is recommended that the plywood be attached with 
stainless steel nails or screws. As discussed in Section 5.1, because 



of lack of guidance on determining wind loads, it is recommended 
that designers use professional judgment in specifying the fastener 
type, size and spacing. 

 EIFS. Many of the failures of EIFS systems observed by the MAT 
were related to the design and installation of fasteners of the EIFS 
systems. In many other cases, failure modes could not be deter
mined 
but could result from one or more of the following: material 
defects, inadequate test standards and methods, specification of in
appropriate 
system by designers, or poor installation. Nevertheless, 
the failures were so common, and the consequences of the failures 
were so severe, that continued use of EIFS is not recommended in 
high wind coastal areas. When these systems are used, fastening of 
the systems could be improved if the following methods and ap
proaches 
are considered: 

 As discussed in Section 5.3.1, it is recommended that 
two revisions be made to test method ASTM E 330. In 
lieu of a 10-second load duration, a 60-second duration 
is recommended. It is also recommended that deflection 
criteria specified in test method ASTM E 1592 be 
incorporated into ASTM E 330. 

 It is also recommended that the EIFS Industry Members 
Association (EIMA) consider all elements of the EIFS 
assembly. Although EIMA members may not manufacture 
or supply assembly components such as metal framing, 
sheathing, or sheathing fasteners, these other elements are 
also critical in achieving suitable wind performance. 

 It is recommended that manufacturers re-evaluate their 
training programs because it was evident that many 
EIFS assemblies were installed improperly, most likely by 
inadequately trained workers. 

 For EIFS installed over sheathing, it is recommended 
that designers specify attachment requirements for all 
elements of the assembly, including framing and sheathing 
attachment. It is also recommended that designers specify 
special inspections to ensure proper application of all 
elements of the assembly. 

 Vinyl Siding. As discussed in Section 5.3.2, it is recommended that 
two revisions be made to test method ASTM D 5206. In lieu of a 30- 
second load duration, a 60-second duration is recommended. It is 
also recommended that deflection criteria specified in test method 
ASTM E 1592 be incorporated into ASTM D 5206. It is also recom
mended 
that the ASTM task group responsible for ASTM D 5206 



give consideration to dynamic testing of vinyl siding in lieu of the 
static testing now prescribed in ASTM D 5206. 

 It is recommended that ASTM D 3679 be revised to require a mini
mum 
safety factor of 2 versus the 1.5 factor currently specified. It 
is recommended that ASTM D 4756 be revised to require installa
tion 
of a water-shedding underlayment (e.g., asphalt-saturated felt 
or housewrap). 

 The method used to determine the pressure equalization factor cur
rently 
specified in ASTM D 3679 appears to be questionable. It is 
therefore recommended that the ASTM task group responsible for 
the Standard reevaluate the magnitude of the pressure equalization 
factor (0.36). 

Tables 8-6 through 8-9 present the wind-related recommendations de
veloped 
by the MAT and first presented in FEMA 490, Summary Report on 
Building Performance 2004 Hurricane Season, March 2005. A full discussion 
of these recommendations can be found in the Hurricane Charley MAT 
report (FEMA 488). Hurricane Charley was a code level wind event, and 
readers are encouraged to obtain a copy of this report. 

Table 8-6 presents design and construction recommendations to 
avoid or lessen potential wind hazard damage to accessory structures, 
the building envelope and exterior equipment. 

Table 8-6. Design and Construction Recommendations 
Building Component 

Recommendation 

Action 
Required By1 

Wind Hazard 

Accessory Structures 

Attached and detached 

Add additional anchors at corner post connections to 
concrete. 

D, C 

Attached and detached 

Use AAF Guide to Alluminum Construction in High Wind 
Areas until FBC 2004 is adopted. 

D 

Attached and detached 

Increase wind resistance of accessory structure walls 
parallel to primary building (e.g., tension cable, solid K 
bracing). 

D 

Attached and detached 

Provide lateral bracing in roof planes using rigid diagonal 
structural members. 

D, C 

Attached 

Ensure attached building and primary building can 
withstand equal wind pressures. 

D, C 

Attached 

Determine implications to primary building if attached 
structure collapses. 

D, C 







Detached 

Determine ability to withstand windstorm events to reduce 
windborne debris. 

D, C 

Doors 

Exterior doors 

Specify wind-driven rain resistant weather-stripping at 
exterior doors (see FEMA 424). 

D 

Entrance vestibules 

Design entrance vestibules in areas where basic wind 
speed is greater than 120 mph. 

D 

Rolling and sectional 
doors 

Consider type, size, and spacing of door, frame, and frame 
fasteners to loads. If frame is attached to wood blocking, 
attention should also be given to the blocking attachment. 

D, C 

Rolling and sectional 
doors 

Maintain adequate edge distances for frame fasteners 
placed in concrete or masonry. 

C 

Soffit 

Soffits 

Design Guidance: Develop design guidance for attaching 
soffits, including design of baffles or filter media to prevent 
wind-driven rain from entering attics. 

Roof Assembly 

Roof systems 

Testing: Roof assemblies susceptible to dynamic loading 
should be dynamically tested to obtain realistic measure 
of their wind resistance. Higher safety factors should be 
used for those assemblies requiring dynamic testing, but 
for which dynamic test methods are not available. 

D, C, G 

Reroofing 

Tear off old roof (do not re-cover) in areas where basic 
wind speed is 110 mph or greater. 

D, C 

Reroofing 

Install additional sheathing fasteners if existing sheathing 
attachment is not in compliance with current building code. 

D, C 

Asphalt shingles 

Ensure manufacturers installation instructions are 
followed (i.e., starter strips and nail locations) and use 
Recovery Advisory Nos. 1 and 2. 

D, C 

Asphalt shingles 

Re-evaluate attachment of factory-laminated tabs. 

M 

Metal panel roof 
system 

Chalk-line clip locations for panels with concealed clips 
and ensure clip locations are not excessively spaced. 

C 

Metal panel roof 
system 

Base uplift resistance on ASTM E 1592. 

M, D 

Metal panel roof 
system 

Specify close spacing of fasteners at eaves, and hip and 
ridge flashings. 

D 

Tile roof system 

Use Recovery Advisory No. 3. 

D, C 





Table 8-6. Design and Construction Recommendations (continued) 

Building Component 

Recommendation 

Action 
Required By1 

Wind Hazard 

Building Envelope 







Table 8-6. Design and Construction Recommendations (continued) 

Building Component 

Recommendation 

Action 
Required By1 

Wind Hazard 

Roof Assembly (continued) 





Tile roof system 

Develop tiles with improved ductility via internal or 
backside reinforcement or bonding film in hurricane-prone 
regions (e.g., develop tile similar to laminated glass). 

M 

Tile roof (foam-set) 
system 

For foam set tile, simplify number of installation options 
and clarify requirements. 

M 

Tile roof (foam-set) 
system 

Modify training and certification programs to ensure that 
foam-set roof installers are adequately trained. 

M, C 

Tile roof (foam-set) 
system 

Use a higher safety factor (e.g., 4) to account for 
application and testing issues. 

M, D 

Mechanically attached 
roof systems 

FRSA/TRI re-evaluate use of safety factor of 2. Either 
develop dynamic test method or use existing test method 
with higher safety factor (e.g., 3). 

M, D 

Built-up roofs 

Develop and codify technically based criteria for aggregate 
surfacing on built-up and sprayed polyurethane foam roofs. 

M, G 

Edge flashings and 
copings 

Comply with ANSI/SPRI ES-1 (2003). Use safety factor of 
3 for critical and essential facilites and a factor of 2 for 
other buildings. 

D 

Edge flashings and 
copings 

Install edge flashings on top of membrane to clamp it 
down. 

D, C 

Edge flashings and 
copings 

Place a bar over roof membrane near edge of flashing and 
coping to provide secondary protection (see FEMA 424). 

D, C 

Gutters and 
downspouts 

Use professional judgment to specify and detail gutter 
uplift resistance. 

D 

Gutters and 
downspouts 

Design Guidance: Develop design guide, test method, and 
code criteria for gutters, including attachment of downspouts. 

M, C 

Rooftop walkway pads 

Research wind resistance of roof walkway pads. 

M, G 

Windows 

General 

Develop window assemblies that are more wind-driven 
rainwater-resistant. 

M 

General 

The window industry should re-evaluate current test 
procedures to better represent wind-driven rain produced 
by hurricane and tropical storm winds. 

D, C, M, G 





Exterior Equipment 

General 

For all exterior equipment, recommend safety factor of 3 
due to uncertainties pertaining to wind load. 

D 

General 

Design Guidance: Develop guidance and code criteria for 
attaching condensers and rooftop mechanical equipment 
(including ductwork). 

D, G 







Table 8-7. Building Code Recommendations 
Wind Hazard 

Building Component 

Recommendation 

Building Envelope 

Soffit 

Soffit 

Develop and adopt wind resistance and wind-load criteria regarding wind 
resistance for soffits. Wind-driven rain resistance of ventilated soffit panels 
should also be added. Testing Application Standard (TAS) 110 may be a 
suitable test method, although it may require modification. 

Roof Assembly 

Edge flashing and 
coping 

FBC Section 1503 (Weather Protection): Compliance with American National 
Standards Institute (ANSI) SPRI ES-1. 

Gutters 

FBC Section 1503 (Weather Protection) and IBC/IRC: Develop and add 
criteria regarding uplift resistance of gutters. 

Ridge vents 

FBC Section 1503 (Weather Protection) and IBC/IRC: Add criteria regarding 
wind and wind-driven rain resistance of ridge vents. Attachment criteria 
require development, but TAS 110 could be referenced for rain resistance. 

Metal panel roof 
system 

FBC Section 1504 (Performance Requirements): Require compliance with 
ASTM E 1592 for testing the uplift resistance of metal panel roof systems. 





General 

Evaluate the need to better secure exterior devices, such 
as pool equipment and roof-mounted solar heaters. 

D, C, O, CF 

Cowlings 

Anchor cowlings on exhaust fans to curbs using cables 
(see FEMA 424). 

M, D, C 

Access panels 

Modify access panels attached by manufacturer to ensure 
secure attachment (see FEMA 424). 

M, D, C 

Lightning protection 
systems 

Develop guidance and code criteria for attachment 
of lightning protection systems (see FEMA 424), 
communications towers, and satellite dishes. 

M, D, C 





1 Action required by: Designer (D), Contractor (C), Manufacturer (M), Government Official (G), Building Owner (O) 

Table 8-6. Design and Construction Recommendations (continued) 

Building Component 

Recommendation 

Action 
Required By1 

Wind Hazard 

Exterior Equipment (continued) 





Table 8-7 presents building code recommendations to avoid or lessen 
damage from potential wind hazards to the building envelope, windows 
and shutters, exterior equipment, and critical and essential facilities. 



Roof system 

FBC Section 1510.3 (Recovering vs. Replacement) and IBC/IRC: Require 
removal of existing roof covering down to the deck and replacement of 
deteriorated sheathing in areas where basic wind speed is 110 mph or 
greater. If existing sheathing attachment does not comply with loads derived 
from Chapter 16, require installation of additional fasteners to meet loads. 

Asphalt shingles 

FBC Section 1507.2 (Roof Covering Application) and IBC/IRC: Require 
compliance with UL 2390. Also require six nails per shingle and require use of 
asphalt roof cement at eaves, rakes, hips, and ridges where basic wind speed 
is 110 mph or greater (refer to Recovery Advisory No. 2). 

Mortar-set tile roof 
system 

FBC Section 1507.4 (Clay and Concrete Tile) and IBC/IRC: Provide an 
alternative to the use of mortar to attach field tiles and hip/ridge tiles. 

Built-up roof 

FBC Section 1508 (Roof Coverings with Slopes Less Than 2:12): Add 
technically based criteria regarding blow-off resistance of aggregate on builtup 
and sprayed polyurethane foam roofs. 

Windows and Shutters 

Shutters 

IBC and FBC Section 1606.1.4 (Protection of Openings): Add requirement to 
label shutters (other than wood) because without labels, building owner does 
not know if shutters are suitable. 

Windborne debris 
region 

FBC: Revise the Florida Panhandle criteria to match ASCE 7. 

Manufactured Housing 

Revise Chapter 15C of the Rules and Regulations of Florida to provide window 
protection systems (and a strengthened structure around openings) on Zone II 
and Zone III units being installed in the windborne regions defined by Chapter 
16 of the FBC. 





Table 8-7. Building Code Recommendations (continued) 

Wind Hazard 

Building Component 

Recommendation 

Roof Assembly (continued) 





Exterior Equipment 

General 

FBC Section 1522.2 (Rooftop Mounted Equipment): Make applicable 
throughout the State of Florida for all wind speeds. Develop and add criteria 
that pertain to attaching lightning protection systems. Provisions also 
included in electrical codes. 

Critical and Essential Facilities 

General 

Critical and essential facilities, at a minimum, should be designed with wind 
loads using an importance factor of 1.15 in accordance with ASCE 7. 







Critical and Essential Facilities (continued) 

General 

For hurricane shelters and Enhanced Hurricane Protection Areas (EHPAs), 
adopt wind speed recommended by FL DCA in the SESP and the ASCE 7- 
02/2001 FBC wind speed map design wind speed plus 40 mph. This is 
also the recommended best practice in the FL DCA shelter design guidance 
and in FBC Section 423, Part 24; change to a requirement. This criterion 
should be required by the SESP and should be used until the International 
Code Councils High Wind Shelter Standard is completed in 2006/2007 and 
available for adoption. 

General 

Minimum debris impact protection should be per ASTM E 1996 Category E 
for a 9-pound 2x4 (nominal) missile traveling at 50 mph. This criterion should 
be required by the SESP and should be used until the ICCs High Wind Shelter 
Standard is completed in 2006/2007 and available for adoption. 

General 

As an alternative to designing shelters to the SESP or ASCE criteria, design 
or retrofit buildings to be used as shelters to the design guidance provided in 
FEMA 361, Design and Construction Guidance for Community Shelters. 





Table 8-7. Building Code Recommendations (continued) 

Wind Hazard 

Building Component 

Recommendation 





Table 8-8 presents recommendations to alert building owners and ho
meowners; 
architects, engineers, and consultants; building officials; 
contractors; manufacturers; and associations, institutions, and societ
ies 
of steps they can take to avoid or lessen potential damages from 
wind hazards. 



Table 8-8. Public Outreach Recommendations 
Wind Hazard 

Education Topic 

Outreach Method 

Building Owners And Homeowners 

Plan and budget construction projects that 
incorporate natural hazard mitigation measures. 

Select design and construction teams 
knowledgeable in effective construction methods 
in hurricane-prone areas. 

Prepare and protect building prior to hurricane 
landfall. 

What to do after hurricane passes (building 
inspection for damage, emergency repairs, and 
drying out building interiors). 

Rebuild damaged structure in manner that 
protects against future damage. 

Inspect exterior connections and fasteners for 
wear, corrosion, and other deterioration. 

Educate building owners on how wind-driven 
rainwater enters buildings, the resulting 
implications (loss of electricity, mold), and 
prevention methods. 

. Tailor informational pamphlets to homeowners 
and building owners. 

. Develop strategy to distribute information (e.g., 
standardized information sheets during sale of 
building). 

. Enlist assistance of real-estate companies and 
organizations such as the Building Owners and 
Managers Association. 

. Provide public service notices at start of each 
hurricane season. 

. Develop informational materials on how winddriven 
rainwater enters buildings, the resulting 
damage, and prevention methods. 

Architects, Engineers, Consultants 

Improve the technical proficiency of building 
envelope design. 

Provide adequate level of design details for 
connecting rooftop equipment, including 
mechanical, electrical and lightning protection. 

Share post-disaster building performance 
information to maximize the value of lessons 
learned. 

. Prepare monographs for trade-wide distribution. 

. Prepare web-based tutorials and seminars. 

. Encourage colleges and universities to augment 
existing curriculum with hurricane-resistant 
design instruction. 







Building Officials 

Share post-disaster building performance 
information to maximize the value of lessons 
learned. 

Train building officials to identify structural 
weaknesses that may cause structure or building 
component failure during a hurricane (e.g., 
unbraced gable ends, missing truss bracing, 
truss anchorage, window/door anchorage). 

Implement effective enforcement techniques to 
maintain a high construction quality. 

. Conduct annual seminars for building officials 
and plan reviewers in coastal areas to share 
lessons learned. 

. Implement hurricane disaster building inspection 
training program and train the trainer program. 

Contractors 

Educate contractors who construct building 
envelopes and install rooftop equipment on 
hurricane resistant fastening and anchoring 
systems. 

Educate contractors on how wind-driven water 
enters buildings, the resulting implications (loss 
of electricity, mold), and prevention methods. 

. Develop and distribute visual tools such as 
instructional videos or DVDs. 

. Conduct on-the-job training to highlight failures 
that occur when simple anchoring techniques 
are not applied. 

. Encourage trade schools in hurricane-prone 
areas to augment their curriculum with 
courses on state-of-the- art hurricane-resistant 
construction. 

Manufacturers 

Educate manufacturers of building envelope 
materials and rooftop equipment on the 
performance of their products during hurricanes. 

Encourage manufacturers to provide special 
guidance for use of their products in hurricaneprone 
areas. 

Develop improved products and systems for 
hurricane-prone areas. 

Manufacturers should educate designers and 
contractors on their products. 

. Develop and distribute informational notices to 
manufacturers. 

Associations, Institutes, and Societies 

Advocate hurricane-resistant design and 
construction to their membership. 

 Develop educational materials for distribution to 
their members and industry. 





Table 8-8. Public Outreach Recommendations (continued) 

Wind Hazard 

Education Topic 

Outreach Method 







Table 8-9. Recommendations Specific to Critical and Essential Facilities 
Wind Hazard 

Component 

Recommendation 

Action
Required By1 

General 

Detailing and notations 
on the building plans 

Facility plans should delineate the facility area designed 
to function as a shelter or hardened area. Details of the 
shelter or hardened area and the envelope elements should 
be provided to ensure that the construction requirements 
are clearly understood by the builder and building official. 
Provide facility design criteria and maximum design 
pressures for the main wind force resisting system 
(MWFRS) and for components and cladding. 

D, C, CFO 

Material selection 

Reinforced concrete roof deck and reinforced concrete 
and/or reinforced and fully grouted concrete masonry 
unit (CMU) exterior walls are recommended. FEMA 
424, Design Guide for Improving School Safety in 
Earthquakes, Floods, and High Winds, and FEMA 361, 
Design and Construction Guidance for Community 
Shelters, provide detailed guidance on material selection 
for structural and building envelope systems. 

D, C, CFO 

General 

Develop additional criteria to help ensure continuity of 
function. See FEMA 424 and FEMA 361. 

CFO 

General 

Emphasize best practices for schools and shelters 
described in FEMA 424 and FEMA 361 respectively, and 
in the latest codes and standards for wind resistance 
(ASCE 7). 

CFO 

Design guidance 

Develop a comprehensive design guide to complement 
FEMA 424 for mitigating existing facilities. 

D, G 

Perform vulnerability 
assessment 

Perform vulnerability assessment to ensure continuity of 
operations. The assessment should evaluate the building 
performance and utilities that service critical/essential 
facilities so that the building owner understands impacts 
to the facility during a storm and operational impacts 
due to limited utility services. 

CFO 





Table 8-9 presents wind-hazard recommendations specific to critical 
and essential facilities. 



General 

Implement mitigation measures or structurally retrofit 
critical/essential facilities to design levels other than 
minimum code requirements for general use buildings. 
Do not house critical facilities in lightly engineered 
buildings such as pre-engineered metal buildings. 

CFO, D 

General 

Educate designers: buildings designed to minimum EHPA 
requirements does not guarantee that building used 
as shelter will be properly designed and constructed to 
resist extreme wind events. Emphasize best practices for 
shelters described in FEMA 361. 

D, C 

General 

Educate designers: American Red Cross 4496 provides 
a baseline for a shelters integrity and performance, 
but meeting this criterion does not guarantee that the 
building will resist wind and windborne debris associated 
with hurricanes. Emphasize best practices for shelters 
described in FEMA 361. 

D, C 

General 

Conduct special inspections for key structural items and 
connections to ensure performance of critical facilities. 

CFO, C 

General 

Design critical and essential facilities with wind loads 
using an importance factor of 1.15 in accordance with 
ASCE 7. For some facilities, design using the 40-mph 
increase with importance factor of 1 (recommended for 
shelter EHPA design in FBC Section 423, Part 24). 

D 

General 

Incorporate hazard mitigation peer review into design 
approval process to ensure that critical and essential 
facilities are adequately designed to resist extreme 
winds. 

D 

Accessory Structures 

Detached 

Strengthen the anchorage of structures and portable 
classroom buildings at schools. 

D, C, G, CFO 

Building Envelope 

General 

Contract drawings and specifications for new construction 
and remedial work on existing building envelopes and 
rooftop equipment should undergo rigorous peer review, 
submittal review, field observation (inspection), and 
testing prior to construction. 

D, C, G 

General 

Implement mitigation measures in buildings not built 
to current building codes to protect roof coverings, 
wall coverings, window and door systems, and rooftop 
equipment. 

D, CFO 





Table 8-9. Recommendations Specific to Critical and Essential Facilities (continued) 

Wind Hazard 

Component 

Recommendation 

Action
Required By1 

General (continued) 







Windows 

Windows 

Implement window protection systems to protect critical 
facilities from windborne debris. 

CFO, D 

Shutters 

Install shuttering system on all exterior glazing that is 
not windborne debris resistant. Install power-operated 
shutters or laminated glass, or apply an engineered film 
system to the glazing and frame on upper-level floors. 

D, C, CFO 





1 Action required by: Designer (D), Government Official (G), Critical Facility Manager/Owner (CFO) 

Table 8-9. Recommendations Specific to Critical and Essential Facilities (continued) 

Wind Hazard 

Component 

Recommendation 

Action
Required By1 

Building Envelope (continued) 







Systems, 

ANSI/SPRI ES-1, 

Wind Design Standard for Edge
Systems Used with Low 

Slope Roofing Systems 

, December 2003. 

ANSI/SPRI RP-4, 

Wind Design Standard for Ballasted Single-ply Roofing 

1 & 2. 

FEMA 55, 

Coastal Construction Manual: Principles and Practices of 

Planning, Siting, Designing, Constructing, and Maintaining Residential 

Buildings in Coastal Areas 

, June 2000. 

November 2002. 

ARC 4496, 

Guidelines for Hurricane Evacuation Shelter Selection 

, July 1992. 

ASCE 7, 

Minimum Design Loads for Buildings and Other Structures. 

ASTM D 3679, 

Standard Specification for Rigid Poly (Vinyl Chloride) (PVC) 

Siding 

ASTM D 4756, 

Standard Practice for Installation of Rigid Poly (Vinyl 

Chloride) (PVC) Siding and Soffit 

, 2003. 

ASTM D 5206 

Standard Test Method for Windload Resistance of Rigid Poly 

(Vinyl Chloride) (PVC) Siding 

ASTM E 1592, 
Metal Roof and Siding Systems by Uniform Static Air Pressure Difference
ASTM E 1996, 


FEMA 339, 

 Hurricane Georges in Puerto Rico 

, March 1999. 

FEMA 348, 

Protecting Building Utilities from Flood Damage 

, 1999. 

FEMA 361, 

Design and Construction Guidance for Community Shelters, 

 

 

July 2000. 


A-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

A 

References 



A P P E N D I X A 

 REFERENCES 

A-2 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

FEMA 424, Design Guide for Improving School Safety in Earthquakes, 
Floods, and High Winds, January 2004. 

FEMA 488, Mitigation Assessment Team Report: Hurricane Charley in 
Florida, Observations, Recommendations, and Technical Guidance, FEMA, 
Washington, DC, February 2005. 

FEMA 490, Summary Report on Building Performance 2004 Hurricane 
Season, March 2005. 

FEMA 499, Home Builders Guide to Coastal Construction, Technical Fact 
Sheets, March 2005. 

FEMA 2004. Hurricane Ivan Flood Recovery Maps, 
http://www.fema.gov/ivanmaps/ 

The Masonry Society, Hurricane Ivan Investigation Report, April 1, 2005. 

The Masonry Society, An Investigation of the Effects of Hurricane Opal on 
Masonry, July 1996. 

NFPA 5000, Building Construction and Safety Code, January 2004. 

National Weather Service Mobile  Pensacola, Powerful Hurricane 
Ivan Slams the U.S. Central Gulf Coast as Upper Category-3 Storm, 
www.srh.noaa.gov/mob/ivan_page/Ivan-main.htm. 

Powell, Mark D., and Houston, Samuel H. Hurricane Andrews 
Landfall in South Florida. Part II: Surface Wind Fields and Potential 
Real-Time Applications, Weather and Forecasting, September 1996. 

Powell, Mark D., Houston, Samuel H. and Reinhold, Timothy A., 
Hurricane Andrews Landfall in South Florida. Part I: Standardizing 
Measurements for Documentation of Surface Wind Fields, Weather 
and Forecasting, Vol. 11, No. 3, September 1996. 

Stewart, Stacy R., Tropical Cyclone Report Hurricane Ivan 2-26 
September 2004 National Hurricane Center Report, 16 December 
2004, Revised 6 January 2005. 

TAS 110-2000, Testing Requirements for Physical Properties of Roof 
Membranes, Insulation, Coatings, and Other Roofing Components. 

Vickery, Peter J., Skerlj, Peter, Steckley, Andrew and Twisdale Lawrence 
A., Hurricane Wind Field Model for Use in Hurricane Simulations, 
Journal of Structural Engineering, ASCE, Oct. 2000, pp 1203-1221 



Acknowledgments B


KenMeredith, 

Alabama 
Department 
of 
Water 
Resources 

Florida 
Department 
of 
Environmental 
Protection, 

Bureau of Beaches and Coastal Systems 

Steve Foote, 

City of Gulf Shores 

W. Craig Fugate, 
Florida Division of Emergency Management 

Jo Godfrey, 

City of Orange Beach 

Chuck Hamilton, 

City of Gulf Shores 

Darryl Hatheway, 

Michael Baker 

Phillip Hicks, 

Alabama Department of Economic 
and Community Affairs 

Jeffrey Moon, 

City of Orange Beach 

Debbie Norton, 

Santa Rosa Island Authority 

Spencer M. Rogers, Jr.
, 

North Carolina Sea Grant 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 


APPENDIX B 

ACKNOWLEDGMENTS 

B-2 

MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

Chuck Sanders, CFM,
Alabama Department of Economic 
and Community Affairs 

Landon Smith,
City of Orange Beach 

Michael Terry,
City of Gulf Shores 

United States Air Force Auxiliary, 
Civil Air Patrol 

Office of the Federal Coordinator for 
Meteorological Services and Supporting 
Research 

Philip West,
City of Orange Beach 



C 
Acronyms and 
Abbreviations


C-1HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 
AAAF Aluminum Association of FloridaADEM Alabama Department of Environmental ManagementANSI American National Standards InstituteARA Applied Research AssociatesARC American Red CrossASCE American Society of Civil Engineersasl above sea levelASOS Automated Surface Observing SystemsASTM American Society for Testing and MaterialsATCT air traffic control towerAWOS Automated Weather Observing SystemBBFE base flood elevation (1-percent annual exceedance probability)
BIA Brick Industry Association 
BOAF Building Officials Association of FloridaBPAT Building Performance Assessment TeamBUR built-up roof

APPENDIX C 

ACRONYMS AND ABBREVIATIONS 

C-2 

MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

C 

C&C components and cladding 

CFR Code of Federal Regulations 

CMU concrete masonry unit 

CHWM coastal high water mark 

D 

DFO Disaster Field Office 

E 

EDT Eastern Daylight Time 

EHPA Enhanced Hurricane Protection Area 

EIFS exterior insulation and finish systems 

EIMA EIFS Industry Members Association 

EMS Emergency Medical Services 

EOC Emergency Operations Center 

EPDM ethylene propylene diene monomer 

ESRI Environmental Systems Research Institute 

F 

FAA Federal Aviation Administration 

FBC Florida Building Code 

FCMP Florida Coastal Monitoring Program 

FDEP Florida Department of Environmental Protection 

FEMA Federal Emergency Management Agency 

FHBA Florida Home Builders Association 

FIRM Flood Insurance Rate Map 



A P P E N D I X C 

ACRONYMS AND ABBREVIATIONS 

FIS Flood Insurance Study 

FLASH Federal Alliance for Safe Homes 

FL DCA Florida Department of Community Affairs 

FRSA Florida Roofing, Sheet Metal and Air Conditioning 
Contractors Association, Inc. 

G 

GDT Geographic Data Technology 

GPS global positioning system 

H 

HAZUS-MH Hazards US  Multi-Hazard 

HWM high water mark 

HMGP Hazard Mitigation Grant Program 

HRD Hurricane Research Division 

HUD U.S. Department of Housing and Urban Development 

HVAC heating, ventilation, and air conditioning 

HVHZ High Velocity Hurricane Zone 

I 

I Importance Factor 

IBC International Building Code 

IBHS Institute for Building & Home Safety 

ICC International Code Council 

ICU intensive care unit 

IRC International Residential Code 

ISO Insurance Services Office 



L 

LPS lighting protection system 

LWIC lightweight insulating concrete 

M 

MAT Mitigation Assessment Team 

MEPS molded expanded polystyrene insulation 

MOB medical office building 

mph miles per hour 

MWFRS main wind force resisting system 

N 

NAHB National Association of Home Builders 

NAVD North America Vertical Datum 

NCDC National Climatic Data Center 

NFIP National Flood Insurance Program 

NFPA National Fire Protection Association 

NGVD National Geodetic Vertical Datum 

NHC National Hurricane Center 

NIST National Institute of Standards and Technology 

NOAA National Oceanographic and Atmospheric 
Administration 

NRCA National Roofing Contractors Association 

NWS National Weather Service 



O 

OFCM Office of the Federal Coordinator for Meteorological 
Services and Supporting Research 

OSB oriented-strand board 

P 

psf pounds per square foot 

PVC polyvinyl chloride 

R 

Rmax radius of maximum winds 

RTI Roof Tile Institute 

S 

SBC Standard Building Code 

SBCCI Southern Building Code Congress International, Inc. 

SESP Statewide Emergency Shelter Plan (Florida) 

SFBC South Florida Building Code 

SFHA Special Flood Hazards Area 

SLOSH Sea, Lake, and Overland Surges from Hurricanes 

SPF sprayed polyurethane foam 

SPRI (New name of the Single Ply Roofing Institute) 

SRBOAF Suwannee River Building Officials Association of 
Florida 

SRIA Santa Rosa Island Authority 



T 

TAS Testing Application Standard 

U 

UL Underwriters Laboratories 

URM unreinforced masonry 

U.S. United States 

USACE U.S. Army Corps of Engineers 

USGS U.S. Geological Survey 

W 

WG/NDR/PSDA Working Group for Natural Disaster Reduction 
and Post-Storm Data Acquisition 



D-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

D 

FEMA 
Hurricane Recovery 
Advisories 



Roof Underlayment for 
Asphalt Shingle 
Roofs 


www.fema.gov 

Recovery Advisory No. 1 

HURRICANE RECOVERY ADVISORY 

Recovery Advisory No. 1  Roof Underlayment for Asphalt Shingle Roofs September 2004 


Page 1 of 2 

Purpose: To provide recommended practices for use of roofing underlayment as an enhanced secondary 
water barrier in hurricane-prone areas (both coastal and inland). 

Key Issues 

 Verify proper attachment of roof sheathing 
before installing underlayment 

 Lapping and fastening of underlayment 
and roof edge flashing 

 Selection of underlayment material type 

Sheathing Installation Options 

The following three options are listed in order of decreasing resistance to long-term weather exposure following 
the loss of the roof covering. Option 1 provides the greatest reliability for long-term exposure; it is advocated 
in heavily populated areas where the design wind speed is equal to or greater than 120 mph (3-second peak 
gust). Option 3 provides limited protection and is advocated only in areas with a modest population density and 
a design wind speed less than or equal to 110 mph (3-second peak gust). 

Installation Sequence  Option 11 

1. Before the roof covering is installed, have the deck inspected to verify that it is nailed as specified on the drawings. 

2. Install self-adhering modified bitumen tape (4 inches wide, minimum) over sheathing joints; seal around 
deck penetrations with roof tape. 

3. Broom clean deck before taping; roll 
tape with roller. 

4. Apply a single layer of ASTM D 226 Type 
II (#30) felt. 

5. Secure felt with low-profile, capped-head 
nails or thin metal disks (tincaps) 
attached with roofing nails. 

6. Fasten at approximately 6 inches on center 
along the laps and at approximately 12 
inches on center along two rows in the 
field of the sheet between the side laps. 

7. Apply a single layer of self-adhering 
modified bitumen complying with ASTM 
D 1970 over the #30 felt throughout the 
roof area. 

8. Seal the self-adhering sheet to the deck 
penetrations with roof tape or asphalt 
roof cement. 

Note: The underlayment options illustrated here are for asphalt shingle roofs. See FEMA publication 55, 
Coastal Construction Manual, for guidance concerning underlayment for other types of roofs. 

Note: This fact sheet provides general guidelines and recom
mended 
enhancements for improving upon typical practice. 
It is advisable to consult local building requirements for 
type and installation of underlayment, particularly if specific 
enhanced underlayment practices are required locally. 



Recovery Advisory No. 1  Roof Underlayment for Asphalt Shingle Roofs September 2004 


Page 2 of 2 

Installation Sequence  Option 21 

1. Before the roof covering is installed, 
have the deck inspected to verify 
that it is nailed as specified on the 
drawings. 

2. Install self-adhering modified bitumen 
tape (4 inches wide, minimum) over 
sheathing joints; seal around deck 
penetrations with roof tape. 

3. Broom clean deck before taping; roll 
tape with roller. 

4. Apply two layers of ASTM D 226 Type I 
(#15) felt with offset side laps. 

5. Secure felt with low-profile, cappedhead 
nails or thin metal disks 
(tincaps) attached with roofing nails. 

6. Fasten at approximately 6 inches 
on center along the laps and at 
approximately 12 inches on center along a row in the field of the sheet between the side laps. 

Installation Sequence  Option 31,2 

1. Before the roof covering is installed, 
have the deck inspected to verify 
that it is nailed as specified on the 
drawings. 

2. Install self-adhering modified bitumen 
tape (4 inches wide, minimum) over 
sheathing joints; seal around deck 
penetrations with roof tape. 

3. Broom clean deck before taping; roll 
tape with roller. 

4. Apply a single layer of ASTM D 226 
Type I (#15) felt. 

5. Tack underlayment to hold in place 
before applying shingles. 

1 Note: If the building is within 3,000 feet of saltwater, 
stainless steel or hot-dip galvanized fasteners are 
recommended for the underlayment attachment. 

2 Note: (1) If the roof slope is less than 4:12, tape and seal the deck at penetrations and follow the recommendations given in The NRCA Roofing 
and Waterproofing Manual, by the National Roofing Contractors Association. (2) With this option, the underlayment has limited blowoff resistance. 
Water infiltration resistance is provided by the taped and sealed sheathing panels. This option is intended for use where temporary or permanent 
repairs are likely to be made within several days after the roof covering is blown off. 

General Notes 

 Weave underlayment across valleys. 

 Double-lap underlayment across ridges (unless there is a continuous ridge vent). 

 Lap underlayment with minimum 6-inch leg turned up at wall intersections; lap wall weather barrier over 
turned-up roof underlayment. 

Additional Resources 

National Roofing Contractors Association (NRCA). The NRCA Roofing and Waterproofing Manual. (www.NRCA.net) 



Asphalt Shingle Roofing 

for High-Wind 
Regions 


www.fema.gov 

Recovery Advisory No. 2 

HURRICANE RECOVERY ADVISORY 

Recovery Advisory No. 2  Asphalt Shingle Roofing for High-Wind Regions September 2004 


Page 1 of 2 

Purpose: To recommend practices for installing asphalt roof shingles that will enhance wind resistance in 
high-wind, hurricane-prone areas (both coastal and inland). 

Key Issues 

 Special installation methods are recommended for asphalt roof shingles used in high-wind, hurricane-prone 
areas (i.e., greater than 90-mph, 3-second peak gust design wind speed). 

 Use wind-resistance ratings to choose among shingles, but do not rely on ratings for performance. 

 Consult local building code for specific installation requirements. Requirements may vary locally. 

 Always use underlayment. See Fact Sheet No. 1 for installation techniques in hurricane-prone areas. 

Construction Guidance 

Follow shingle installation procedures for enhanced wind resistance. 

1 



Recovery Advisory No. 2  Asphalt Shingle Roofing for High-Wind Regions September 2004 


Page 2 of 2 

Consider shingle physical properties. 

1. Design wind speed based on 3-second peak gust. 

2. ASTM D 3462 specifies a minimum fastener pull-through resistance of 20 lb at 70 F. If a higher resistance is desired, it must be specified. 

3. Neither ASTM D 225 or D 3462 specify minimum bond strength. If minimum bond strength is desired, it must be specified. 

Ensure that the fastening equipment and method results in properly driven roofing nails for maximum 
blow-off resistance. The minimum required bond strength must be specified (see Wind-Resistance 
Ratings, below). 

Fastener Guidelines 

 Use roofing nails that extend through 
the underside of the roof sheathing, or 
a minimum of 3/4 inch into planking. 

 Use roofing nails instead of staples. 

 Use stainless steel nails when 
building within 3,000 feet of 
saltwater. 

Weathering and Durability 

Durability ratings are relative and are not standardized among manufacturers. However, selecting a shingle 
with a longer warranty (e.g., 30-year instead of 20-year) should provide greater durability in hurricane-prone 
climates and elsewhere. 

Organic-reinforced shingles are generally more resistant to tab tear-off, but tend to degrade faster in warm 
climates. Use fiberglass-reinforced shingles in warm, hurricane-prone climates and consider organic shingles 
only in cool, hurricane-prone climates. Modified bitumen shingles may also be considered for improved tear-off 
resistance of tabs. Organic-reinforced shingles have limited fire resistance  verify compliance with code and 
avoid using in areas prone to wildfires. 

After the shingles have been exposed to sufficient sunshine to activate the sealant, inspect roofing to ensure 
that the tabs have sealed. Also, shingles should be of interlocking type if seal strips are not present. 

Wind-Resistance Ratings 

Wind resistance determined by test methods ASTM D 3161 and UL 997 does not provide adequate 
information regarding the wind performance of shingles, even when shingles are tested at the highest fan 
speed prescribed in the standard. Rather than rely on D 3161 or UL 997 test data, shingle uplift loads should 
be calculated in accordance with UL 2390. Shingles having a bond strength (as determined from test method 
ASTM D 6381) that is at least twice as high (i.e., a minimum safety factor of 2) as the load calculated from 
UL 2390 should be specified/purchased. 

2 


3 



Tile Roofing for 

Hurricane-Prone Areas 


www.fema.gov 

Recovery Advisory No. 3 

HURRICANE RECOVERY ADVISORY 

Recovery Advisory No. 3  Tile Roofing for Hurricane-Prone Areas November 2004 


Page 1 of 2 

Purpose: To provide recommended practices for designing and installing extruded concrete and clay tiles that will 
enhance wind resistance in hurricane-prone areas (both coastal and inland). 

Key Issues 

Missiles: Tile roofs are very vulnerable to breakage from wind-borne debris (missiles). Even when well attached, they 
can be easily broken by missiles. If a tile is broken, debris from a single tile can impact other tiles on the roof, which 
can lead to a progressive cascading failure. In addition, tile missiles can be blown a considerable distance and a 
substantial number have sufficient energy to penetrate shutters and glazing, and potentially cause injury. Where the 
basic wind speed is equal to or greater than 110 mph (3-second peak gust), the wind-borne debris issue is of greater 
concern than in lower wind speed regions. Note: There are currently no testing standards requiring roof tile systems to 
be debris impact resistant. 

Attachment methods: Storm damage investigations 
revealed performance problems with mortar-set, 
mechanically-attached (screws or nails and supplementary 
clips when necessary) and foam-adhesive (adhesive-set) 
attachment methods. In many instances, the damage 
was due to poor installation. Investigations revealed that 
the mortar-set attachment method is typically much more 
susceptible to damage than are the other attachment 
methods. Therefore, in lieu of mortar-set, the mechanicallyattached 
or foam-adhesive attachment methods in 
accordance with this Advisory are recommended. 

To ensure quality installation, licensed contractors should 
be retained. This will help ensure proper permits are filed 
and local building code requirements are met. For foamadhesive 
systems, it is highly recommended that installers 
be trained and certified by the foam manufacturer. 

Uplift loads and resistance: Calculate uplift loads and resistance in accordance with the Design and Construction 
Guidance section below. Load and resistance calculations should be performed by a qualified person (i.e., someone 
who is familiar with the calculation procedures and code requirements). 

Corner and perimeter enhancements: Uplift loads are greatest in corners, followed by the perimeter and then the 
field of the roof (see Figure 1). However, for simplicity of application on smaller roof areas (e.g., most residences and 
smaller commercial buildings), use the attachment designed for the corner area throughout the entire roof area. 

Hips and ridges: Storm damage investigations have revealed that hip and ridge tiles attached with mortar are very 
susceptible to blow-off. Refer to the attachment guidance below for improved attachment methodology. 

Quality control: During roof installation, installers should implement a quality control program in accordance with the 
Quality Control section below. 

Design and Construction Guidance 

1. Uplift Loads 

In Florida, calculate loads and pressures on tiles in 
accordance with the current edition of the Florida Building 
Code (Section 1606.3.3). In other states, calculate loads 
in accordance with the current edition of the International 
Building Code (Section 1609.7.3). 

As an alternate to calculating loads, design uplift pressures 
for the corner zones of Category II buildings are provided 
in tabular form in the Addendum to the Third Edition of the 
Concrete and Clay Roof Tile Installation Manual (see Tables 6, 
6A, 7, and 7A). 


Classification of Buildings 

Category I - Buildings that represent a low 
hazard to human life in the event 
of a failure 

Category II - All other buildings not in 
Categories I, III, and IV 

Category III - Buildings that represent a 
substantial hazard to human life 

Category IV - Essential facilities 



Recovery Advisory No. 3  Tile Roofing for Hurricane-Prone Areas November 2004 


Page 2 of 2 

2. Uplift Resistance 

For mechanical attachment, the Concrete and Clay Roof Tile Installation Manual provides uplift resistance data for 
different types and numbers of fasteners and different deck thicknesses. For foam-adhesive-set systems, the Manual 
refers to the foam-adhesive manufacturers for uplift resistance data. Further, to improve performance where the basic 
wind speed is equal to or greater than 110 mph, it is recommended that a clip be installed on each tile in the first row 
of tiles at the eave for both mechanically-attached and foam-adhesive systems. 

For tiles mechanically attached to battens, it is recommended that the tile fasteners be of sufficient length to penetrate 
the underside of the sheathing by  minimum. For tiles mechanically attached to counter battens, it is recommended 
that the tile fasteners be of sufficient length to penetrate the underside of the horizontal counter battens by  
minimum. It is recommended that the batten-to-batten connections be engineered. 

For roofs within 3,000 feet of the ocean, straps, fasteners, and clips should be fabricated from stainless steel to 
ensure durability from the corrosive effects of salt spray. 

3. Hips and Ridges 

The Concrete and Clay Roof Tile Installation Manual gives guidance on two attachment methods for hip and ridge 
tiles: mortar-set or attachment to a ridge board. Based on post-disaster field investigations, use of a ridge board is 
recommended. For attachment of the board, refer to Table 21 in the Addendum to the Concrete and Clay Roof Tile 
Installation Manual. 

Fasten the tiles to the ridge board with screws (1 minimum penetration into the ridge board) and use both adhesive 
and clips at the overlaps. 

For roofs within 3,000 feet of the ocean, straps, fasteners, and clips should be fabricated from stainless steel to 
ensure durability from the corrosive effects of salt spray. 

4. Critical and Essential Buildings (Category III or IV) 

Critical and essential buildings are buildings that are expected to remain operational during a severe wind event such 
as a hurricane. It is possible that people may be arriving or 
departing from the critical or essential facility during a hurricane. 
If a missile strikes a tile roof when people are outside the 
building, those people may be struck by tile debris dislodged by 
the missile strike. Tile debris may also damage the facility. It is 
for these reasons that tiles are not recommended on critical or 
essential buildings. 

If it is decided to use tile on a critical or essential facility and 
if the tiles are mechanically attached, it is recommended that 
clips be installed at all tiles in the corner, ridge, perimeter, and 
hip zones (see ASCE 7-02 for the width of these zones). (See 
Figure 1) 

5. Quality Control 

It is recommended that the applicator designate an individual to 
perform quality control (QC) inspections. That person should be 
on the roof during the tile installation process (the QC person 
could be a working member of the crew). The QC person should 
understand the attachment requirements for the system being 
installed (e.g., the type and number of fasteners per tile for mechanically attached systems and the size and location 
of the adhesive for foam-adhesive systems) and have authority to correct noncompliant work. The QC person should 
ensure that the correct type, size, and quantity of fasteners are being installed. 

For foam-adhesive systems, the QC person should ensure that the foam is being applied by properly trained applicators 
and that the work is in accordance with the foam manufacturers application instructions. At least one tile per square 
(100 square feet) should be pulled up to confirm the foam provides the minimum required contact area and is correctly 
located. 

If tile is installed on a critical or essential building, it is recommended that the owner retain a qualified architect, 
engineer, or roof consultant to provide full-time field observations during application. 

Note: In addition to the tables referenced above, the Concrete and Clay Roof Tile Installation Manual contains other 
useful information pertaining to tile roofs. Accordingly, it is recommended that designers and installers of tile obtain a 
copy of the Manual and the Addendum. Hence, the tables are not incorporated in this Advisory. 

Figure 1. For critical and essential facilities, 
clip all tiles in the corner, ridge, perimeter, 
and hip zones. 
NOTE: See ASCE 7 
for zone width. 
Perimeter 
zone 
Hip zone 
Field 
Corner zone Ridge zone 
 The Manual can be purchased online from the Florida Roofing, Sheet Metal and Air Conditioning Contractors 
Association, Inc. at www.floridaroof.com or by calling (407) 671-3772. Holders of the Third Edition of the Manual who do 
not have a copy of the Addendum can download it from this web site. 



Recovery Advisory No. 4  Coastal Building Successes and Failures December 2004 

Page 1 of 4 

Coastal Building Successes 
and Failures 


www.fema.gov 

HURRICANE RECOVERY ADVISORY 

Recovery Advisory No. 4 

Purpose: To discuss how coastal construction requirements are different from those for inland construction. 
To discuss the characteristics that make for a successful coastal building. 

Is Coastal Construction That Different From Inland Construction? 

The short answer is, yes, building in a coastal 
environment is different from building in an inland 
area: 

 Flood levels, velocities, debris, and wave action in 
coastal areas tend to make coastal flooding more 
damaging than inland flooding. 

 Coastal erosion can undermine buildings and destroy 
land, roads, utilities, and infrastructure. 

 Wind speeds are typically higher in coastal areas 
and require stronger engineered building connections 
and more closely spaced nailing of building 
sheathing, siding, and roof shingles. 

 Wind-driven rain, corrosion, and decay are frequent 
concerns in coastal areas. 

In general, homes in coastal areas must be designed and built to withstand 
higher loads and more extreme conditions. Homes in coastal areas will require 
more maintenance and upkeep. Because of their exposure to higher loads and 
extreme conditions, homes in coastal areas will cost 
more to design, construct, maintain, repair, and insure. 

Building Success 

In order for a coastal building to be considered a 
success, four things must occur: 

 The building must be designed to withstand coastal 
forces and conditions. 

 The building must be constructed as designed. 

 The building must be sited so that erosion does not 
undermine the building or render it uninhabitable. 

 The building must be maintained/repaired. 

A well-built but poorly sited building can be undermined 
and will not be a success (see Figure 1). Even if a 
building is set back or situated farther from the coastline, 
it will not perform well (i.e., will not be a success) if it is 
incapable of resisting high winds and other hazards that 
occur at the site (see Figures 2 and 3). 


Figure 1. Poorly sited building on shallow foundation 
undermined by erosion. 


Figure 2. Well-sited buildings that still sustained damage due 
to building envelope and connection failures. 



Recovery Advisory No. 4  Coastal Building Successes and Failures December 2004 

Page 2 of 4 

Similarly, a building compliant with the regulatory 
requirement that the lowest floor be elevated to the Base 
Flood Elevation (BFE) can still be damaged when the flood 
elevation exceeds the BFE (see Figure 4 and the discussion 
of lowest floor elevation in item 3 on the next page). The 
BFE is the expected elevation of flood waters and wave 
effects during the 100-year flood. 


Figure 3. Well-sited building that still sustained damage due 
to building envelope and connection failures. 

Figure 4. Compliant building damaged when the 
flood elevation exceeded the BFE. 

What Should Owners and Home Builders Expect From a Successful Coastal Building? 

In coastal areas, a building can be considered a success only if it is capable of resisting damage 
from coastal hazards and coastal processes over a period of decades. This statement does not imply 
that a coastal residential building will remain undamaged over its intended lifetime. It means that the 
impacts of a design-level flood, storm, wind, or erosion event (or series of lesser events with combined 
impacts equivalent to a design event) will be limited to the following: 

 The building foundation must remain intact and functional. 

 The envelope (walls, openings, roof, and lowest floor) must remain structurally sound and capable of 
minimizing penetration by wind, rain, and debris. 

 The lowest floor elevation must be sufficient to prevent floodwaters from entering the elevated 
building envelope during the design event. 

 The utility connections (e.g., electricity, water, sewer, natural gas) must remain intact or be restored 
easily. 

 The building must be accessible and usable following a design-level event. 

 Any damage to enclosures below the Design Flood Elevation (DFE)* must not result in damage to the 
foundation, the utility connections, or the elevated portion of the building. 

*The DFE is the locally mandated flood elevation, which will be equal to or higher than the BFE. 



Recovery Advisory No. 4  Coastal Building Successes and Failures December 2004 

Page 3 of 4 

Recommended Practice 


1 

Siting  Site buildings away from 
eroding shorelines and high-hazard 
areas. 

Building Form  Flat or low-sloped 
porch roofs, overhangs, and gable 
ends are subject to increased 
uplift in high winds. 
Buildings that are 
both tall and narrow 
are subject to 
overturning. Each of 
these problems can 
be overcome through 
the design process, 
but each must receive 
special attention. In 
the design process, 
chose moderate-sloped 
hip roofs (4/12 to 6/12) 
if possible. 

Lowest Floor Elevation  
Elevate above the DFE the bottom of the lowest horizontal structural member supporting the lowest floor. 
Add freeboard to reduce damage and lower flood insurance premiums. 

Freeboard is a factor of safety, usually expressed in feet above flood level, that is applied to compensate 
for unknown factors that could contribute to flood heights greater than those calculated for a selected 
flood. Freeboard is advisable in coastal areas where storms often cause flooding that exceeds the 100- 
year flood elevation. 

Free of Obstructions  Use an open foundation. Do not obstruct the area below the elevated portion 
of the building. Avoid or minimize the use of breakaway walls. Do not install utilities or finish enclosed 
areas below the DFE (owners tend to convert these areas to habitable uses, which is prohibited under the 
National Flood Insurance Program and will lead to additional flood damage and economic loss). 

Foundation  Make sure the foundation is deep enough to resist the effects of scour and erosion; strong 
enough to resist wave, current, and flood forces; and capable of transferring wind and seismic forces on 
upper stories to the ground. 

Connections  Key connections include roof sheathing, roof-to-wall, wall-to-wall, and walls-to-foundation. 
Be sure these connections are constructed according to the design. Bolts, screws, and ring-shanked nails 
are common requirements. Standard connection details and nailing should be identified on the plans. 

Exterior Walls  Use structural sheathing in high-wind areas for increased wall strength. Use tighter 
nailing schedules for attaching sheathing. Care should be taken not to over-drive pneumatically driven 
nails. This can result in loss of shear capacity in shearwalls. 

Windows and Glass Doors  In high-wind areas, use windows and doors capable of withstanding 
increased wind pressures. In windborne debris areas, use impact-resistant glazing or shutters. 

Flashing and Weather Barriers  Use stronger connections and improved flashing for roofs, walls, doors, 
and windows and other openings. Properly installed secondary moisture barriers, such as housewrap or 
building paper, can reduce water intrusion from wind-driven rain. 

Roof  In high-wind areas, select appropriate roof coverings and pay close attention to detailing. Avoid 
roof tiles in hurricane-prone areas. 

Porch Roofs and Roof Overhangs  Design and tie down porch roofs and roof overhangs to resist uplift 
forces. 

Building Materials  Use flood-resistant materials below the DFE. All exposed materials should be 
moisture- and decay-resistant. Metals should have enhanced corrosion protection. 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 



Mechanical and Utilities  Electrical boxes, HVAC equipment, and other equipment should be elevated 
to avoid flood damage and strategically located to avoid wind damage. Utility lines and runs should be 
installed to minimize potential flood damage. 

Quality Control  Construction inspections and quality control are essential for building success. Even 
minor construction errors and defects can lead to major damage during high-wind or flood events. Keep 
this in mind when inspecting construction or assessing yearly maintenance needs. 

Will the Likelihood of Success (Building Performance) Be Improved by Exceeding Minimum 
Requirements? 

States and communities enforce regulatory requirements that 
determine where and how buildings may be sited, designed, 
and constructed. There are often economic benefits to 
exceeding the enforced requirements (see box). Designers 
and home builders can help owners evaluate their options 
and make informed decisions about whether to exceed these 
requirements. 

Adopting and enforcing modern building codes (e.g., IBC, IRC, 
and FBC) and educating residents, businesses, contractors, 
and community officials on best construction practices with 
regard to the design of new structures and the mitigation of 
hazards to older structures are recommended. 

Next Steps 

To improve coastal construction practices, consider the following: 

 Contact your local building official to obtain the latest applicable building code requirements for coastal 
construction. 

 Review best practices guidelines and recommendations contained in FEMAs Coastal Construction Manual. 
The Coastal Construction Manual is available in Adobe Portable Document Format (PDF) on CD-ROM (FEMA 
55CD) and as a print publication (FEMA 55). Both versions are available from the FEMA Distribution Center. 
Call 1-800-480-2520 and request either FEMA 55CD or FEMA 55. 

 
*Note: Flood insurance premiums can be reduced up to 60 percent by exceeding minimum siting, design, and construction practices. See 
the V-Zone Risk Factor Rating Form in FEMAs Flood Insurance Manual (http://www.fema.gov/nfip/manual.shtm). 

13 

14 

Benefits of Exceeding Minimum 
Requirements 

 Reduced building damage during 
coastal storm events 

 Reduced building maintenance 

 Longer building lifetime 

 Reduced insurance premiums* 

 Increased reputation of builder 



H 

and to the east of where the center of the storm made landfall. Wide 

Hurricane Ivan made landfall on September 16, 2004, at approximate 

- 
maximum sustained winds of 130 miles per hour. Hurricane-force 

winds extended outward up to 105 miles from the center of the storm. 

Coastal storm surge flooding of 10 to 16 feet above normal tide lev 

- 

els, along with large and dangerous battering waves, occurred near 

meowners, to identify existing and increased flood hazards caused by 

the storm, and to use this information during recovery and redevelop 

- 

ment to avoid future flood damages. 

Hurricane Ivan maps are for advisory purposes only; they do not su 

- 

- 

spread damage occurred, including the damage and/or destruction of 

homes, infrastructure, and beach erosion. 

In the wake of this devastating event, the Federal Emergency Man 

- 

agement Agency (FEMA) initiated a short-term project to produce 

high-resolution maps that show flood impacts from the storm for por 

- 

tions of Okaloosa, Escambia, and Santa Rosa Counties in Florida, and 

Baldwin County, Alabama. The maps, which are available from the 

 

Ivan maps link on 

www.fema.gov/ivanmap 

s 

, show high water mark 

flood elevations, flood inundation limits from Hurricane Ivan, the 

inland limit of waterborne debris (trash lines), and storm surge el
evation contours based on the high water marks. The maps also show 
comparison to the Hurricane Ivan data. 
- 

persede effective FIRMs. The Ivan data presented are preliminary and 

subject to update as additional data become available. Figure E-1 shows 

a flood recovery map for Gulf Shores, Alabama. 


A P P E N D I X E 

IVAN FLOOD RECOVERY MAPS 

E-1 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 

E 

Ivan Flood 
Recovery Maps 





A P P E N D I X E 

IVAN FLOOD RECOVERY MAPS 

E-2 

MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 


Figure E-1. Sample Flood Recovery Map A9 for Gulf Shores, Alabama. 



F 
OrangeBeach 
High-RiseStudy 

HURRICANE IVAN IN ALABAMA AND FLORIDA MITIGATION ASSESSMENT TEAM REPORT 
Post-Ivan High-Rise Damage SurveyHigh-rise buildings along the Orange Beach, Alabama, Gulf of Mex-
ico shoreline (seaward of Perdido Beach Boulevard.) were inspected 
by FEMA contractors between November 3 and 18, 2004. The pur-
pose of the inspections was to determine the numbers and elevations 
of lowest floor living units that were damaged or destroyed by flood 
effects during Hurricane Ivan. Given the large number of damaged 
multi-family buildings that would not be classified as substantially 
damaged, an attempt was made to identify those lowest floor living 
units that could be repaired or reconstructed in-place, and which 
would have been classified as substantially damaged had they been 
individual buildings. 
Building data were collected using a data sheet (see Figure F-1) and 
information from the data sheets was tabulated. A total of 43 build-
ings were inspected (see Figure F-2). Two buildings collapsed and 
would be classified as substantially damaged, and were removed from 
the study sample. Characteristics of the remaining 41 buildings are 
summarized in Table F-1.

APPENDIX F 

ORANGE BEACH HIGH-RISE STUDY 

F-2 

MITIGATION ASSESSMENT TEAM REPORT HURRICANE IVAN IN ALABAMA AND FLORIDA 

Table F-1. Summary of Orange Beach, Alabama, High-Rise Buildings Inspected 

Buildings Inspected (43) 

Number of Buildings Inspected 

43 

Total Number of Living Units 

3,567 

Collapsed Buildings (2) 

Number of Buildings Collapsed 

2 

Number of Living Units, Collapsed Buildings 

70 

Standing Buildings (41) 

Number of Buildings 

41 

Number of Living Units 

3,497 

Average Number of Living Units (range = 18 to 247) 

85 

Average Number of Stories (range = 5 to 15) 

11 

Number of Buildings with Living Units on Lowest Floor 

39 

Number of Living Units, Lowest Floor 

233 

Number of Buildings with Lobby/Common Area on Lowest 
Floor 

28 





Figure F-3 shows the lowest floor elevations of the 41 buildings used 
for the analysis. Figure F-4 shows the numbers of lowest floor living 
units versus lowest floor elevation. 



A P P E N D I X F 

ORANGE BEACH HIGH-RISE STUDY 


Figure F-1. Sample data sheet for Orange Beach high-rise study 



Figure F-2. Locations of 43 high-rise buildings inspected in Orange Beach, Alabama (numbers are code numbers assigned during inspections) 



The lowest top-of-lowest-floor elevation was 10 feet the National Geo
detic 
Vertical Datum (NGVD), but the lowest living units were at 12.5 
feet NGVD; the highest top of a lowest floor was 21.9 feet NGVD. Ap
proximately 
two-thirds of the tops of lowest floors and lowest floor 
living units were between 14.6 feet NGVD and 18.5 feet NGVD. 

Inspections showed the bottom of the lowest horizontal supporting 
member (BLHM) of the lowest floor (excluding pile caps) varied from 


Figure F-3. 
Top of lowest floor 
elevations for Orange 
Beach high-rise buildings 


Figure F-4. 
Lowest floor living unit 
elevations 



Table F-4. Numbers of Lowest Floor Living Units Classified by Damage States 
(n = 233) for 41 Orange Beach High-Rise Buildings 

Floor Condition 

Sums 

Wall Condition 

Intact 

Damaged 

Destroyed 

Intact 

28 

0 

0 

28 

28 

Damaged 

18 

1 

3 

22 

205 

Destroyed 

101 

24 

58 

183 

Sums 

147 

 25 

58 

233 

 

147 

86 

 

233 





Figure F-5. 
Floor intact, wall intact 
damage state 


TLF 

EROSION 

BLHM 



Building Damage versus Lowest Floor Elevation 

Building damage states were compared against lowest floor elevations. 
Not surprisingly, buildings with the lowest floor elevations had more 
wall and floor destruction than buildings with higher floor elevations 
(see Table F-5, Figure F-8 and Figure F-9). 

Figure F-6. 
Floor intact, wall 
destroyed damage state 


Figure F-7. 
Floor destroyed, wall 
destroyed damage state 

TLF 

BLHM 



Note that even though the number of lowest floor living units above el
evation 
19.6 feet was less than 10 percent of the total number of lowest 
floor living units (see Figure F-4), these units accounted for 75 percent 
of the total number of undamaged lowest floor living units  units at 
higher floor elevations had a better survival rate. 

Similarly, 69 percent of the totally destroyed lowest floor living units 
were below elevation 16.5 feet NGVD, even though only 52 percent of 
the total number of lowest floor living units were below this elevation  
units at lower elevations had a greater likelihood of being destroyed. 

Review of Hurricane Ivan water levels at Orange Beach (see Table 1-2 
and Figure 1-10) show that water levels reached elevations of approxi
mately 
12 to 15 feet NGVD, which exceeded the BFEs there. The Ivan 
water levels may have included wave setup and some wave effects, but 
probably did not reflect the true wave crest elevation, which could 
have been several feet higher than the measured water levels. The fact 
that lowest floor living units survived intact only when the floor eleva
tion 
exceeded 19 feet NGVD is consistent with this, and reinforces the 
importance of adding freeboard  designing and constructing build
ings 
above the minimum elevations required by the NFIP. 

Table F-5. Damage States versus Top of Lowest Floor Elevation* 

Damage State 

Number of 
Buildings (n) 

Average Top of Lowest 
Floor Elevation (ft NGVD) 

Floor Intact, Wall 
Intact 

6 

19 

Floor Intact, Wall 
Destroyed 

21 

17.4 

Floor Destroyed, 
Wall Destroyed 

15 

15.9 





* damage states not included in table for small n 



Building Damage versus Erosion Depth 

Building damage states were also compared against erosion depth at 
the building foundations. Not surprisingly, buildings with the greatest 
erosion depths had more wall and floor destruction than buildings 
with lower erosion depths (see Table F-6). Low erosion depths were as
sociated 
with buildings sited farther from the shoreline, and buildings 
near the east end of Orange Beach, where sand trapped against the 
East Pass jetty produced a wide beach seaward of the buildings. 

Figure F-8. 
Floor intact, wall intact 
damage state versus top 
of lowest floor elevation 


Figure F-9. 
Floor destroyed, wall 
destroyed damage state 
versus top of lowest floor 
elevation 



Table F-6. Damage States versus Average Erosion Depth* 

Damage State 

Number of Buildings (n) 

Average Erosion Depth 
(ft) 

Floor Intact, Wall 
Intact 

6 

1.3 

Floor Intact, Wall 
Destroyed 

20 

7 

Floor Destroyed, Wall 
Destroyed 

15 

6 





* damage states not included in table for small n 

Summary of Findings 

 While the exact construction requirements for each building 
(i.e., the effective flood hazard zones and BFEs at the time of 
construction) are not certain, all but two of the high-rise structures 
examined were constructed with pile foundations -- which prevented 
total collapse of the structures. 

 The buildings, as a whole, performed well structurally, although a 
high percentage of the lowest floor living units and common areas 
were damaged or destroyed by Ivans flood effects and erosion. 
Lowest floor damage could have been prevented or reduced by 
adherence to current VE zone construction standards and use of 
freeboard to elevate the lowest floors several feet above the BFE. 

 Elevating the lowest floor one story above the BFE and using the 
space below the BFE for parking would be the most appropriate 
means of reducing lowest floor living unit damage to new high-rise 
buildings in the area.