VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

ACKNOWLEDGMENTS

HUD’s Office of Policy Development and Research:

Government Technical Representative: Michael D. Blanford

Technical Advisory Group:

Thanks to the following subject matter experts for their contributions to this guide.

USERS

PRODUCERS

PUBLIC INTEREST

Chair: Randy Noel, MIRM

Francis Babineau, PE

Dana Bres, PE

Anne Anderson, SE

Daniel Buckley

Nicholas Crossley

Heather Anesta, PE, SE

Michael Chandler

Melissa Deas

Illya Azaroff, FAIA

Julia Donoho, AIA, Esq.

Greg Grew, AIA, CBO

Dr. Henry Burton, SE

Michael Funk

Dr. Therese P. McAllister, PE

Matthew Cooper, PE

Maria Hernandez

Amanda Siok

Andrew Kollar, AIA

Elizabeth Miller

Dana Sjostrom, CFM

Darlene Rini, PE

William Sanderson

Nancy Springer, CBO

James Williams, AIA, PE, SE

Lisa Stephens

Kristopher Stenger, AIA

Frank Thompson

Russell Strickland

Dr. Theresa Weston

Meghan Walsh, AIA

Additional Wind Task Group Members

Leader: Heather Anesta, PE, SE

Victor Drozd

Mary Uher

Keith Barnett

Sarah Krompholz

Michael Weber

Alexandra Cary

Tammy Lee

Julie Shiyou Woodard

Dr. Anne Cope, PE

Donald Leifheit, Jr.

Matt Dobson

Loren Ross, PE

Illustrations by VIZ Graphics

Authored by Home Innovation Research Labs

Located in Upper Marlboro, Maryland, Home Innovation Research Labs (Home Innovation) was founded in 1964 as a wholly-owned, independent subsidiary of the National Association of Home Builders (NAHB). Originating as a small product testing laboratory, Home Innovation has since grown to become a full-service market research, building science research, consultant, product testing laboratory, and accredited third-party certification agency dedicated to issues related to the homebuilding industry.

DISCLAIMER

Neither Home Innovation, nor any person acting on its behalf, makes any warranty, express or implied, with respect to the use of any information, apparatus, method, or process disclosed in this publication or that such use may not infringe privately owned rights, or assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method, or process disclosed in this publication, or is responsible for statements made or opinions expressed by individual authors. The contents of this report are the views of the contractor and do not necessarily reflect the views or policies of the U.S. Department of Housing and Urban Development or the U.S. Government.

Visit the Disaster Recovery Tool Kit on the U.S. Department of Housing and Urban Development (HUD), Office of Policy Development and Research (PD&R) website—huduser.gov/portal/disaster-recovery.html—to find this report and other relevant resources, reports, guides, and ordinances sponsored by PD&R to aid homeowners and property owners in the disaster recovery process. Many of the reports in the kit are available in print by calling the HUD User Clearinghouse at 1–800–245–2691, option 1.

As always, all reports are available as free downloads from HUD User.

ii | WIND

HUD.GOV

FOREWORD

According to the National Oceanic and Atmospheric Administration, the United States spent $145 billion in 2021 recovering from natural disasters, which included wildfires, tropical cyclones, floods, tornados, drought conditions, and extreme winter storm events. To mitigate the impact of natural disasters, the U.S. Department of Housing and Urban Development (HUD) continues to develop technical guidance to improve the resilience of housing.

Resilience is characterized by a community’s ability to minimize damage and recover quickly from extreme events and changing conditions.

The Designing for Natural Hazards: A Resilience Guide for Builders & Developers series was developed with a technical advisory group that included subject matter experts from a wide range of industry stakeholders. The experts were tasked with identifying above-code construction techniques to improve the resilience of residential buildings. A consensus process was used with the goal of creating a set of practical, actionable guidelines for builders and developers. The guidelines are intended for new construction, improvements before a natural disaster, and major reconstruction efforts after natural disasters, especially where entire communities need to be rebuilt.

The technical advisory group recognized that when natural disasters occur, certain damage is more likely than other types of damage. To address this challenge, the technical advisory group recommended a mitigation strategy that prioritizes high-frequency damage over damage that rarely occurs—based on post-disaster damage assessment reports. This novel approach encourages improving those parts of the building that typically get damaged first. It can also maximize the impact of disaster mitigation grants by preventing future damage to homes.

The resilience guides are an excellent addition to HUD’s PD&R Disaster Recovery Took Kit. These guides should be updated periodically based on post-disaster damage assessment data—from future natural disasters. The resilience guides will be valuable resources to builders and developers seeking to incorporate resilience in housing.

Solomon Greene

Principal Deputy Assistant Secretary for Policy Development and Research U.S. Department of Housing and Urban Development

HUD.GOV

WIND | iii

TABLE OF CONTENTS

ACKNOWLEDGMENTS ....................................................................................................................... ii

DISCLAIMER ....................................................................................................................................... ii

FOREWARD ...................................................................................................................................... iii

INTRODUCTION TO VOLUME 1: WIND .............................................................................................. 1

BACKGROUND ................................................................................................................................... 1

HOW TO USE THE GUIDES ................................................................................................................. 1

Defining Wind Damage and Resilient Construction ............................................................ 2

Frequency of Damage Type ................................................................................................ 2

Prioritizing High-Frequency Damage for Resilience ............................................................ 3

Grouping Resilience Practices ............................................................................................. 3

NEXT STEPS AND FUTURE RESEARCH ................................................................................................ 4

RESILIENCE “ONE-PAGERS”

Openings—Shutters ............................................................................................................ 5

Roof Deck & Underlayment ................................................................................................ 7

High-Wind Roof Covering ................................................................................................... 9

Continuous Load Path ....................................................................................................... 11

Garage Doors .................................................................................................................... 13

Wall System ...................................................................................................................... 15

Soffit .................................................................................................................................. 17

Pressurization Design ........................................................................................................ 19

Chimney ............................................................................................................................ 21

Roof-Mounted Equipment ................................................................................................ 23

REFERENCES .................................................................................................................................... 25

iv | WIND

HUD.GOV

INTRODUCTION TO

especially reconstruction in areas where entire communities

need to be rebuilt after catastrophic events. The guides do not

VOLUME 1: WIND

focus on minor repairs or renovations that are common after

typical natural disaster events and do not address commercial

Designing for Natural Hazards is a set of resiliency guides for buildings, although many of the construction practices

builders and developers. It is segmented into five short

identified are also applicable to multifamily mixed-use

volumes, each focusing on a specific natural hazard type, as

buildings with wood framing.

illustrated below:

To make the guides as practical and have as much input and

buy-in as possible, Home Innovation employed many of the

same approaches used to assemble the Technical Advisory

Group (TAG) when helping develop the American National

Standards Institute (ANSI) standards. Specifically, Home

Innovation recruited a balanced number of stakeholders to

reach consensus on the approach to developing content. In

addition, all Task Group meetings were open to the public, and

input was solicited beyond the members of the TAG and its

Task Groups. Although these guides were not developed in

accordance with the requirements of an ANSI standard, the

approach to these guides mirrored that spirit and intent of

creating a voluntary, consensus document.

HOW TO USE THE GUIDES

The Designing for Natural Hazards guides are intended to be This guide is Volume 1: Wind, which highlights the damage

used by a wide range of stakeholders, including design

caused by windstorms (that is, tornadoes, hurricanes,

professionals, builders, developers, and even prospective

waterspouts, microbursts, and derechos); in addition, the

homebuyers. The guides differ from other resiliency programs

guide identifies resilient construction practices that can

and resources because they are not a prescriptive program or

eliminate or minimize wind damage in a meaningful way.

list of improvements. Instead, the resilience guides are

BACKGROUND

designed to be flexible and allow users to focus on either a

single resilient construction practice or multiple resilient

HUD tasked Home Innovation Research Labs (Home Innovation)

construction practices, depending on the user’s specific needs.

to develop a set of practical, actionable guidelines for builders

The technical content is provided on a single, double-sided

and developers to design and construct residential buildings,

page for each resilient construction practice. These “one-

neighborhoods, and accessory structures in a manner that could

pagers” are intended to be printed and used as stand-alone

improve residential resilience and integrate resiliency

documents for a builder or developer to specify an above-code

throughout the entire community. The Designing for Natural

construction practice. The one-pagers can also be given to a

Hazards guides accomplish this task by providing technical prospective homebuyer or building owner as a supplemental

content in a very straightforward manner that is easy for a

marketing document to highlight the resilient construction

layperson to understand while also providing references for

features that have been included in a new building.

design professionals, builders, developers, and public officials to Each one-pager includes key information about the specific

dive deeper into the necessary details. These resilience guides

natural hazard and resilient construction practice that will

are not intended to substitute for engineering or architectural

minimize or eliminate potential damage. The front of each

project design work; instead, the technical guidance identifies

document identifies (1) the damage expected by the hazard

the components that can be enhanced or improved to achieve

(as shown in the photo); (2) the frequency that a specific type

above-code performance that should make residential buildings

of damage occurs; (3) a description of the resilient

and other community assets more resilient.

construction practice that can minimize damage; (4) a

The Designing for Natural Hazards guides focus on new description of the mitigation strategy; and (5) a summary of

construction and major reconstruction after natural disasters,

the cost and benefit of implementing the resilient construction

HUD.GOV

WIND | 1

practice. The back of the document provides

additional design guidance details, including (1)

multiple design variations and supplemental

resilient construction practices; (2) the

corresponding level of difficulty associated with

implementing alternative resilient construction

practices; (3) the relative cost of implementing the

various options; and (4) technical references that

provide more information for each design option.

Because the resilient construction practices

summarized in these guides are intended to be

implemented in areas where the building code does

not specify resilient construction practices, builders

cannot rely on a building code official to verify that

the practices have been followed. Therefore,

builders who undertake these resilient construction

practices will need to either incorporate the

practices into their internal quality assurance

process or hire a third-party organization to confirm

Figure 1. Federal Emergency Management Agency’s Composite Wind Zone Map Source: National Institute of Standards and Technology

that the resilient construction practice(s) was

appropriately included in the design and constructed

Federal Emergency Management Agency (FEMA) and HUD.

per their specification, which will require some additional detail The Task Group gathered and discussed the wind damage

beyond the one-pagers.

described in the reports, then reviewed a wide range of

Defining Wind Damage and

technical resources—for example, resources from FEMA, HUD,

Resilient Construction

the American Society of Civil Engineers (ASCE), the International

Code Council (ICC), and the Insurance Institute for Business & Wind damage can occur from a variety of windstorms,

Home Safety (IBHS)—to identify the most relevant resilient

including the most common types: thunderstorms,

construction content to be included in the Wind one-pagers.

microbursts, tornadoes, hurricanes, cyclones, haboobs, and

derechos. National Oceanic and Atmospheric Administration

For those building in an area that is already designated as a

(NOAA) defines damaging winds as “those that exceed

high-risk wind zone, nearly all of the wind-related resilient

50–60 mph. Most thunderstorm winds that cause damage at

construction practices in this guide will apply, in addition to

the ground are a result of outflow generated by a

other requirements. However, for those building a more wind-

thunderstorm downdraft—[these] damaging winds are often

resilient residential building outside a high-risk wind zone area

called ‘straight-line’ winds to differentiate the damage they

(that is, in a low-risk wind zone area), this guide can help

cause from tornado damage. A tornado is a narrow, violently

builders implement the practices incrementally by adding one

rotating column of air that extends from a thunderstorm to

or more wind-resilient features to the building.

the ground. Major hurricanes can cause devastating to

FEMA publishes a composite map of wind zones in the United

catastrophic wind damage and significant loss of life simply

States, as illustrated in Figure 1.

due to the strength of their winds.” For this Designing for

Natural Hazards guide, the Wind Task Group did not Frequency of Damage Type

distinguish in the cause of wind damage because it can occur

After familiarizing themselves with specific damage caused by

from a wide range of weather phenomena and is generally

windstorm events described in various disaster reports, the

handled the same way by insurance companies.

Wind Task Group was asked to determine the type of damage

The first undertaking for the Wind Task Group was to identify

most likely to occur when considering all possible damage from

typical damage that happens when windstorm events occur.

wind. The authors have identified the damage on the one-

To that end, the group reviewed case studies of major storm

pagers, and, to determine the frequency, the Wind Task Group

events, such as hurricanes and tornadoes, published by the

reviewed available damage data from Auburn University’s

2 | WIND

HUD.GOV

building as the most practical mitigation strategy

for resilience. Many were concerned that if

funding for above-code practices/strategies were

limited, or if a builder wanted to invest in a

specific resilient construction practice above all

others, knowing what was most important to do

would be difficult, if not for some level of

prioritization. Data about the frequency of

damage type are necessary for builders and

developers to prioritize the resilient construction

practices that will yield the greatest benefit—or

the least damage—to the building. The damage

frequency metrics on the one-pagers are intended

Figure 2. Quantification of Common Wind Damage

to provide builders and developers with a general idea of the

Patterns in Recent Windstorms

frequency and severity of possible damage so that cost alone

Source: StEER Network

is not driving the mitigation strategy.

Structural Extreme Events Reconnaissance (StEER) Program.

According to StEER, their mandate is “to investigate structural

The StEER data offer a level of insight for wind-related damage

performance under natural hazards that emphasizes those

that is not available for other hazard types. The StEER report

causing structural damage to the built environment, generally

titled Quantification of Common Wind Damage Patterns in

due to dynamic load effects. This would include hurricanes

Recent Windstorm states, “[Graphs and] plots show that roof (wind, wave, and storm surge), tornadoes and other wind

damage is more prevalent than wall damage across all classes

events, earthquakes, and tsunamis. While wind-driven rain is

of buildings [i.e., residential, multifamily, and commercial],

considered as part of the cascading hazards encountered in

with roof cover (e.g., shingles) the most frequently damaged

wind events like hurricanes, other forms of water damage due

building component. Wall cladding typically is the next most

to inland flooding are generally not targeted by StEER. Similarly, frequently damaged building component. Some variability

while cascading hazards such as fire after earthquakes could be

between occupancy classes in the distribution of damage to

investigated as part of an earthquake response, StEER would

the various building components is observed, but the sample

not respond to a wildfire event in and of itself.”

sizes for multifamily and commercial structures are notably

smaller than that for single-family structures. Care should be

StEER focuses on collecting representative datasets for each

taken in any direct comparisons of building performance

hazard event, typically sampling from clusters of similar

across the occupancy classes.” Because the one-pagers in this

structure types (for example, single-family residential,

document primarily focus on single-family buildings, the

commercial) across the hazard gradient and sampling at

authors do not attempt to aggregate single-family data with

regularly spaced intervals within the clusters (for example,

the multifamily data provided by StEER.

every other or every third structure).

Grouping Resilience Practices

StEER provided the following damage frequency data in

Figure 2, which focuses on the primary building components

The Wind Task Group believed that licensed design

with visible exterior damage, stratified by hazard intensity and

professionals and subject matter experts would be able to

structure occupancy. Please note that damage to large door

prioritize resilient construction practices without much

openings was calculated using only structures that contained

guidance.

large door openings (as a result, it is a smaller sample size).

The most basic prepackaged system of resilient construction

Prioritizing High-Frequency

practices could be as simple as selecting the basic practice for

each of the one-pagers in the Wind Guide to encourage some

Damage for Resilience

baseline level of resilience. The Task Group also explored a

Because these resilient construction practices are intended for

“Good, Better, and Best” approach to grouping the one-

low-risk areas that need additional resilience to wind hazards,

pagers, in which the basic levels of resilience would be

several participants on the Technical Advisory Group

branded as “Good,” the more advanced practices could be

recommended prioritizing high-frequency-damage areas of the

combined with those basics to offer a “Better” option, and the

HUD.GOV

WIND | 3

Table 1. Example of “Good, Better, and Best” Approach to Resilient Construction Practices for Wind

USING MULTIPLE 1-PAGERS

GOOD

BETTER

BEST

Openings—Shutters

High Frequency

High Frequency

High Frequency

Roof Deck & Underlayment

High Frequency

High Frequency

High Frequency

High-Wind Roof Covering

High Frequency

High Frequency

High Frequency

Continuous Load Path

High Frequency

High Frequency

High Frequency

Garage Doors

High Frequency

High Frequency

High Frequency

Wall System

X

Moderate Frequency

Moderate Frequency

Soffit

X

Moderate Frequency

Moderate Frequency

Pressurization Design

X

Moderate Frequency

Moderate Frequency

Chimney

X

X

Low Frequency

Roof-Mounted Equipment

X

X

Low Frequency

most comprehensively resilient practices could be considered

A closer look at the graph indicates that the roof structure and

a “Best” level of resilience. Table 1 provides an example of this

substrate have clearly improved, but roof covering damage is

type of approach for Wind Resilience, in which the one-pagers

not much different, whether the residential building is newly

are grouped on the basis of the frequency of occurrences.

built or a much older existing residential building. This type of

in-depth granular analysis of damage data can improve

In this example, the bundling strategy is to prioritize high-

building products and focus resilience practices where the

frequency occurrences such that a “Good, Better, and Best”

damage is occurring.

program adds more improvements that might be less likely to

occur until a builder or developer is doing everything in this

StEER states, “Finally, hazard intensity is clearly correlated

guide. Again, this is just one example; other approaches can be

with increasing damage overall.” Even within the lowest wind

developed and deployed.

speed bin, however (65–90 mph), roof cover damage is still

NEXT STEPS AND FUTURE

frequently observed. The data show that, considering all

hazard intensities and years of construction, 26 to 50 percent

RESEARCH

of the roof cover on a single-family home is typically damaged

in an extreme windstorm.

As resilient construction practices evolve, the one-pagers

Considering the damage data available across hazard types,

within this guide should be updated to reflect improvements

StEER’s data should be considered invaluable to understanding

or modifications. To improve the damage frequency metric,

how buildings are performing, and more data like this should

additional data mining can be done with StEER’s damage data.

be gathered for other natural hazards.

The Wind Task Group discussed correlating

damage data against the age of the house as a

way to illustrate if the building code has improved

house performance over time. StEER provided the

following graph as an example of how their

damage data can be evaluated to see if older

houses are at greater risk of damage compared

with new homes in the same vicinity of a specific

windstorm event. See Figure 3, which illustrates

the frequency of damage for different building

components for homes built before 2002 and

those built after that date.

Figure 3. Single-Family Home—Damage Frequency

Source: StEER Network

4 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

OPENINGS—SHUTTERS

Window shutter styles for hurricane protection include colonial, Bahama, roll-up, and accordion-style shutters.

Adequate window and door protection is vital for keeping your family and your home safe. Exterior doors and windows that have not been designed to withstand severe weather events provide a significant entry point for major wind damage to a home. Openings can be damage amplifiers, in some cases causing structural failures when breached. This product improves the resilience of the structure.

Broken window from wind -borne

debris.

Damage Frequency

HIGH

Construction Practice

Install window shutters to protect

from wind-borne debris.

Mitigation Strategy

Storm shutters minimize the risk of

windows breaking from wind-borne

debris.

WINDOW SHUTTERS

Cost & Benefit

Cost range to implement: $–$$$

Benefit: Shutters are built

specifically to help guard windows

against flying debris, wind, rain, hail,

and other extreme forces associated

with a tropical storm. Potentially

avoids the cost of repairing major

damage.

WIND | 5

GUIDANCE

DIFFICULTY COST

Install window shutters to protect from wind-borne debris.

Moderate

$$

Eliminate mulled windows. [1]

Easy

$

Outside swing doors are recommended. [2]

Easy

$

The door and windows, as an assembly, must be rated for the design pressure. [3]

Easy

$

For the door assembly (door and all associated hardware and components), meet the design wind Easy

$$

pressure for the site. [3]

All glazed openings (windows, patio doors, skylights, glass block, etc.) must be able to resist or be Moderate

$$

protected from wind-borne debris. [3]

All exterior door assemblies must be pressure and impact rated or protected by a system that is rated for the exposure category, design wind speed, door size, and door location on the building. Assembly Moderate

$$$

includes door, door frame attachment to wood frame, and lock. [3]

RESOURCES

1. GM-0501: Rainwater Management Performance of Newly Constructed Residential Building Enclosures During August and

September 2004. Building Science Corporation.

2. 2020 FORTIFIED HomeTM Standard. Insurance Institute for Business & Home Safety (IBHS).

3. Section R609, Exterior Windows and Doors. 2018 IRC.

6 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

ROOF DECK AND UNDERLAYMENT

The roof is the most frequently damaged system of a structure in a severe weather event. Roof damage can be an amplifier, causing additional failures beyond the roof. Wind damage can result in extensive and costly water intrusion damage from water infiltration.

Use a minimum of 7/16 in. plywood or oriented strand board (OSB). For nailing decking—4 in. on center (o.c.) along the edges and 6 in. o.c. in the field, with 8d round head 2-1/2 in., .131 ring shank nails. Follow product installation according to the manufacturer’s instructions to maintain warranty Roof deck, cover, & underlayment

and to reduce potential failure.

damage.

Damage Frequency

1

2

HIGH

3

Construction Practice

Proper decking and flashing

installation are highlighted in the

4

construction details.

5

Mitigation Strategy

6

Strengthen the roof by installing a

system built for high-wind events.

Cost & Benefit

Cost range to implement: $–$$

Benefit: Installing additional layers

of protection from water infiltration

decreases the chance for potential

1. One layer of ASTM D226 Type II,

6. Annular ring or deformed shank nails

costly water damage.

ASTM D4869 Type IV, or ASTM D6757

with metal or plastic caps. Cap

2. 4 in. wide (minimum) self-adhering

diameter not less than 1 in. Nail shank

modified bitumen tape at sheathing

diameter not less than 0.083 in. Metal

joints

cap thickness not less than 32-gauge

sheet metal or 0.01 in. for power-

3. 4 in. overlap

driven fasteners. Plastic cap outside

4. Metal drip edge

edge thickness not less than 0.035 in.

5. Stagger runs

WIND | 7

GUIDANCE

DIFFICULTY COST

DECKING

Use a minimum 7/16 in. plywood or OSB. [1]

Easy

$–$$

Nailing decking—4 in. o.c. along the edges and 6 in. o.c. in the field, w/8d round head 2-1/2 in., Moderate

$$

.131 ring shank nails. [1]

SECONDARY WATER BARRIER AND UNDERLAYMENT

Install a 4-in.-wide (nominal) ASTM D1970 compliant self-adhering polymer-modified bitumen or AAMA 711-13, Level 3 roof deck flashing tape over all roof horizontal and vertical roof deck seams, then cover the deck with a #30 felt or an equivalent synthetic underlayment. Lap up the side walls Easy

$

4–6 in., and tape with flashing tape. Fasten underlayment with button cap nails at 6 in. o.c. along the laps and 12 in. o.c. spacing, vertically and horizontally, between the laps. [1]

Install a two-layer #30 felt underlayment. To achieve a double layer, cut 17 in. off one side of the roll, and install the remaining 19-in.-wide strip of underlayment. Tack in place. Install a 36-in.-wide roll of underlayment over the 19-in.-wide course of underlayment along the eave. Continue, overlapping the Easy

$

sheets 19 in. (leaving a 17-in. exposure). Attach underlayment with button cap nails at 6 in. o.c. along the laps and 12 in. o.c. spacing, vertically and horizontally, between the laps. Lap up the sidewalls 4–6 in., and tape with flashing tape. [1]

Install a self-adhered (peel-and-stick) membrane meeting ASTM D1970 requirements over the entire Moderate

$$

roof deck. Lap up the sidewalls 4–6 in. [1]

FASTENERS FOR UNDERLAYMENT

Metal cap nails— 32-gauge cap with minimum 1 in. diameter — minimum ring shank 0.083 in. or smooth Moderate

$$

shank 0.091 in. Length not less than 3/4 in. into roof sheathing. [2]

Plastic cap nails— 0.035 in. edge cap with minimum 1 in. diameter — minimum ring shank 0.083 in. or smooth shank 0.091 in. Length shall be sufficient to penetrate the roof sheathing or not less than 3/4

Moderate

$$

in. into roof sheathing. Fasteners shall be corrosion resistant. [2]

Fasten underlayment with button cap nails at 6 in. o.c. along the laps and 12 in. o.c. spacing, vertically Moderate

$$

and horizontally, between the laps. [2]

RESOURCES

1. 2020 FORTIFIED HomeTM Standard. Insurance Institute for Business & Home Safety (IBHS).

2. Chapter 9, Roof Assemblies. 2018 IRC.

8 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

HIGH-WIND ROOF COVERING

During a hurricane, tornado, high winds, or hailstorms, roof shingles can be damaged or blown off the roof, exposing the underlayment and the sheathing as the only protection against rainwater. Exposed sheathing will eventually succumb to water damage. Unsealed joints or holes in the roof sheathing due to storm damage can allow rainwater to enter the building, causing severe damage, including saturation of insulation and ceiling drywall, potentially leading to collapsed ceilings and extensive damage to interior finishes and household contents. Properly select and install asphalt shingles when installing roofing on new construction to minimize the risk of water intrusion Roof deck, cover, and

due to shingles being damaged or blown off the roof during high winds or underlayment damage.

hurricanes. Follow product installation according to the manufacturer’s instructions to maintain warranty and to reduce potential failure.

Damage Frequency

HIGH

Construction Practice

High-wind roof covering installation

details improve the performance in

high-wind weather events.

Mitigation Strategy

2

Install roof coverings specifically

designed for high-wind zones.

1

Cost & Benefit

Cost range to implement: $–$$$

Benefit: Installing additional layers

of protection from water infiltration

decreases the chance for potential

costly water damage.

1. Asphalt shingle nailing zone (varies

the manufacturer. If the shingle does

according to manufacturer; some use

not have a nail zone or nail line, nails

nail line instead of a zone).

should be installed close to the

2. Nails should be installed in the nailing

shingle centerline to secure the

zone or on the nail line, depending on

shingle below.

WIND | 9

GUIDANCE

DIFFICULTY COST

ROOF COVER

Asphalt shingles should be high-wind rated and be installed with six nails, per high-wind installation Easy

$

instructions. [1]

For shingle roof installations, seal the drip edge at eaves using a self-adhering starter strip or applying Moderate

$

an 8-in.-wide layer of flashing cement, maximum 1/8 in. thick. [1]

Use asphalt roof cement to glue and ensure bonding to enhance the attachment of hip and ridge Moderate

$

shingles. [2]

All other roof coverings (metal, concrete and clay tile, low-sloped roofs, wood shakes, or shingles) should Moderate to

be rated and installed per the manufacturer for the site-specific wind speed and design pressures.

$$–$$$

Complex

Use the ASCE 7-16 FORTIFIED™ Wind Uplift Design Pressure Calculator on fortifiedhome.org [1]

DRIP EDGE and FLASHING

Install drip edge on top of the underlayment (except where instructions or the building code stipulate a different method), extend a minimum of 1/4 in. below roof sheathing, and extend onto the roof deck Easy

$

2 in. [1]

Drip edges must be mechanically fastened to the roof deck at a maximum of 4 in. o.c. [1]

Easy

$

Install flashing at wall and roof intersections at each change in roof slope or direction and around roof openings. A flashing shall be installed to divert the water away from where a roof intersects a vertical sidewall. [3]

Moderate

$

Base flashing against a vertical sidewall shall be continuous or step flashing and shall be not less than 4 in. in height and 4 in. in width and shall direct water away from the vertical sidewall onto the roof or into the gutter. [3]

RESOURCES

1. 2020 FORTIFIED HomeTM Standard. Insurance Institute for Business & Home Safety (IBHS).

2. Coastal Construction Manual: Principles and Practices of Planning, Siting, Designing, Constructing, and Maintaining Residential

Buildings in Coastal Areas, 4th ed. Volume I. FEMA P-55. 2011.

3. Chapter 9, Roof Assemblies. 2018 IRC.

10 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

CONTINUOUS LOAD PATH

Designing a structure to withstand the forces of wind is one of the greatest challenges a builder can face. Much like breaking the weakest link in a chain, high wind at the weakest point in the load path may cause a home structure to fail.

A complete load path ensures that all of the parts and systems of a home work together—a properly designed roof should be tied to a properly designed wall system, which is tied to a properly designed foundation. Each home and site will have a unique load path and conditions and need to be Failure due to lack of load path.

considered individually. This general image illustrates connecting the Source: FEMA

different structural systems together.

Damage Frequency

HIGH

Construction Practice

Using connectors, attach adjacent

wood structural sheathing over

common framing to provide lateral

and uplift load continuity.

Mitigation Strategy

Use continuous load path

connections.

Cost & Benefit

Cost range to implement: $–$$

Benefit: Good connections that tie

the floor, walls, and roof together

provide continuity in the load path

and more reliable building

Connectors:

performance. Potentially avoids the

cost of repairing major damage.

Roof Member to Top Plate

Stud to Sill Plate

Top Plate to Stud

Sill Plate to Foundation

Floor to Floor

Shear Load Transfer

FOR WIND LOADING ONLY

WIND | 11

GUIDANCE

DIFFICULTY COST

Attach adjacent wood structural panel wall sheathing over common framing to provide lateral and Easy

$

uplift load continuity. [1]

Have a licensed engineer design the load path to consider site-specific conditions.

Easy

$$

Roof Sheathing Attachment: Increase the nailing to 4 in. at panel edges and 6 in. along intermediate Easy

$

supports (from a 6/12-in. pattern), and use ring/screw shank nails to increase withdrawal strength. [2]

Gable End Walls: Brace gable end walls at both the top and bottom, and ensure that they are properly Easy

$

attached to the roof and wall, respectively. [3]

Gable End Walls: Sheathe all gable ends with wood structural panels that have the same performance Easy

$

category as the walls. [4]

Roof Truss/Rafter Attachment: Attach roof framing member to the wall top plates with a fastener that Easy

$

resists loads in all three directions. [5]

Bracing of Roof Framing: Ensure that trusses and rafters, especially those with taller heels, are properly braced with solid blocking between the top plates and roof sheathing to transfer the loads from the Easy

$

roof to the walls. [6]

Floor-to-Floor Connections: Ensure that upper and lower floors are properly attached to resist uplift Easy

$

loads and create a solid lateral connection. [7]

Wall System Design: Ensure that walls are properly designed to resist all loads. [8]

Easy

$

Wall-to-Foundation Connection: Attach sill plates to the foundation with 1/2 in. anchor bolts at 32-48 in. o.c. Provide a 3x3-in.-square plate washer at each anchor bolt. Ensure that the wall sheathing Easy

$

is attached to the properly anchored sill plate with the nailing pattern of the edge of the sheathing, as required by the wall design. [9]

RESOURCES

1. Building for High-Wind Resistance in Light-Frame Wood Construction. Form No. M310E. APA – The Engineered Wood

Association. August 2018.

2. Building for High-Wind Resistance, Figure A.

3. Building for High-Wind Resistance, Figure B.

4. Building for High-Wind Resistance, Figure C.

5. Building for High-Wind Resistance, Figure D.

6. Section R602.10.8 Braced Wall Panel Connections. 2018 IRC.

7. Building for High-Wind Resistance in Light-Frame Wood Construction, Figure E.

8. Building for High-Wind Resistance, Figures F and G.

9. Building for High-Wind Resistance, Figures H and I.

12 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

GARAGE DOORS

Adequate garage door protection is vital for keeping your family and your home safe. The garage door, the largest and weakest opening in your house, is the area of your home most likely to fail first. Garage doors can be damage amplifiers, in some cases causing structural failures of the roof when breached. The garage door must be rated for high winds with reinforced components.

Broken garage door from

wind-borne debris.

Damage Frequency

HIGH

Construction Practice

Install additional brackets and rails

in the garage door. Brackets

reinforce the frame, and the rails

reinforce the garage door.

Mitigation Strategy

1

Additional structural support for

garage door.

3

Cost & Benefit

4

Cost range to implement: $–$$$

2

Benefit: A wind-rated garage door

can minimize damage to the home.

1. Heavy gauge metal track

3. Heavy-duty panel section

2. Horizontal structural reinforcement

4. Heavy-duty brackets and hinges

WIND | 13

GUIDANCE

DIFFICULTY COST

Install additional brackets and rails in the garage door. Brackets reinforce the frame, and the rails Moderate

$$–$$$

reinforce the garage door.

For garage doors without glazed openings (windows), the door assembly (door and all associated hardware and components) must meet the design wind pressure for the site or protect the garage Moderate

$$

door with an impact-rated shutter/screen product that meets the design wind pressure for the site. [1,2]

For garage doors with glazed openings (windows), the door assembly must be rated for the design pressure and impact, or the garage door shall be protected with an impact-rated shutter/screen Moderate

$$–$$$

product that meets the design wind pressure for the site. [1,2]

RESOURCES

1. 2020 FORTIFIED HomeTM Standard. Insurance Institute for Business & Home Safety (IBHS).

2. Section R609, Exterior Windows and Doors. 2018 IRC.

14 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

WALL SYSTEM

Designing a structure to withstand the forces of wind is one of the greatest challenges a builder can face. A continuously sheathed, well-designed wall system resists racking. This guidance provides information on constructing and installing the wall system components, which include framing, sheathing, water-resistive barriers (WRBs), windows, and doors.

Exterior wall damage from high

winds.

Damage Frequency

MODERATE

Construction Practice

Use a full wrap of oriented strand

board (OSB) or plywood around the

exterior of the home, running from

roof to foundation. Nail per IRC 6 in.

o.c. on all four edges and 12 in. o.c.

in field.

1

Mitigation Strategy

3

5

6

4

Continuous load path connections,

2

sheathing, a weather-resistant

barrier, and wind-rated windows

and doors can improve the wall

system performance.

Cost & Benefit

1. House framing

4. Weather-resistant barrier

Cost range to implement: $–$$$

2. OSB or plywood sheathing

5. High-wind-rated entry door

Benefit: A continuously sheathed,

3. High-wind-rated windows

6. High-wind-rated garage door

well-designed wall system

minimizes structural and water

penetration damage.

WIND | 15

GUIDANCE

DIFFICULTY COST

Use a full wrap of OSB or plywood around the exterior of the home, running from roof to foundation.

Moderate

$$–$$$

Nail per IRC 6 in. o.c. on all four edges and 12 in. o.c. in field. [1,2]

Increase interior and exterior shear walls nailing pattern to 4 in. o.c. on edges and 6 in. o.c. in field. [3]

Easy

$

Inspect nailing patterns for exterior structural panels and shear walls.

Easy

$

Corrugated Brick Ties:

Anchor into studs, not sheathing. [1]

Easy

$

--OR--

For anchoring into sheathing, refer to IRC 2018 Section Table 703.8.4(2). [1]

Use reinforced CMU/ICF for exterior walls of the home, running from roof to foundation. These Moderate

$$–$$$

concrete wall systems are also applicable to foundation/basement walls. [4]

Use vinyl siding that complies with the 2017 edition of ASTM D3679 (2017), and verify that selected Moderate

$

siding has a design wind pressure rating that equals or exceeds the required design wind pressure. [5,6]

Use high-wind-rated fiber cement products for exterior cladding (no blind nailing) and trim in lieu of Moderate

$–$$

vinyl siding. [7]

Verify that selected fiber cement products and attachment schedules are designed or tested to meet NA

NA

the design wind pressures in the 2018 IRC or ASCE-10. [5]

NA = not applicable.

RESOURCES

1. Section R703, Exterior Covering. 2018 IRC.

2. Full-Scale 3D Wall Bracing Tests. APA Report T2007-73. APA—The Engineered Wood Association. November 2007.

3. APA Engineered Wood Construction Guide. Table 23. APA E30. APA—The Engineered Wood Association. 2019.

4. PCA100-2017 Prescriptive Design of Exterior Concrete Walls for One and Two-Family Dwellings. Portland Cement Association.

5. Best Practices for Minimizing Wind and Water Infiltration Damage, Hurricane Michael in Florida. FEMA. 2019.

6. Mitigation Assessment Team Report: Hurricane Irma in Florida: Building Performance Observations, Recommendations, and

Technical Guidance. FEMA P-2023. 2018.

7. BSD 111: Flood and Hurricane Resistant Buildings. Building Science Digests. Building Science Corporation. 2006.

16 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

SOFFIT

Attics are vented (cooled) three ways: (1) vents on the roof, (2) gable end vents, and (3) vents under eaves or overhangs (soffit vents). Hurricane winds can drive large amounts of water through attic ventilation openings. During major storm events, if gable end vents are present, they should be covered or closed (similar to other building envelope openings). The following information is intended to help minimize water intrusion through attic ventilation systems, not to change from a ventilated to an unvented system.

Damaged soffit.

Damage Frequency

MODERATE

Construction Practice

Install additional nailing strips for all

1

types of soffit materials.

Mitigation Strategy

Soffits should be fastened securely

2

to the eave structure; they should

not be loose in the channels.

Cost & Benefit

Cost range to implement: $–$$

3

Benefit: Prevents further damage, as

wind-driven rain can push into the

building, causing damage to attic

insulation and interior walls.

1. Vent on the roof

2. Gable end vents

3. Soffit vents under

eaves or overhangs

WIND | 17

GUIDANCE

DIFFICULTY COST

Additional nailing strips for all types of soffit materials. [1]

Easy

$

With vinyl and metal soffit, follow manufacturer-recommended high-wind application. [1]

Easy

$

Use fiber cement or wood soffit material (confirm nailing patterns). [2]

Moderate

$$

Use fiber cement soffit material applied over additional nailing strips. [1]

Moderate

$$

RESOURCES

1. Technical Fact Sheet No. 7.5, Minimizing Water Intrusion Through Roof Vents in High-Wind Regions. Home Builder’s Guide to

Coastal Construction. FEMA P-499. 2010.

2. BSD 111: Flood and Hurricane Resistant Buildings. Building Science Digests. Building Science Corporation. 2006.

18 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

PRESSURIZATION DESIGN

Designing a structure to withstand the high forces of wind is one of the greatest challenges a builder can face. Proper design is critical to resist high wind. This guidance provides designers and builders with information and resources such that they will consider wind- and water-resistant building envelopes.

Structure failure due to wind

pressurization.

Damage Frequency

-15 psf

Flat or gable, up to 7" roof slope,

MODERATE

-37 psf

no overhang

Construction Practice

-20 psf

+15 psf

Attachment to roof should not

-16 psf

compromise roof system and should

be engineered on the basis of site

-20 psf

location.

Mitigation Strategy

-15 psf

Encourage the use of wind-resistant

Gable, >27" to 45" roof slope,

roof shapes (for example, hip over

overhang all sides

gable design).

Cost & Benefit

-27 psf at perimeter, corners, and ridge line

Cost range to implement: $–$$$

Benefit: Proper roof design can

-46 psf at corners

-23 psf at hip and ridge lines

minimize damage to roofs from high

winds.

-27 psf at perimeter

-13 psf

Hip or gable, 7" to 27" roof slope,

overhang all sides

WIND | 19

GUIDANCE

DIFFICULTY COST

Do not distribute concentrated loads in walls around openings.

Easy

$

Stack openings of each level. [1]

Easy

$

Shear walls should have low aspect ratios (height-to-width ratio). [2,4]

Easy

$

Shear walls/protections should be at corners. [3,4]

Easy

$

Ask engineer to optimize shear wall lengths.

Complex

$$

Easy to

Larger openings should be parallel to main roof joists (in non-load-bearing walls).

$–$$$

Complex

RESOURCES

1. Advanced Framing Construction Guide. APA M400. APA—The Engineered Wood Association. April 2016.

2. ANSI/AWC 2015 Special Design Provisions for Wind and Seismic (SDPWS). American Wood Council.

3. 2018 Wood Frame Construction Manual (WFCM). American Wood Council.

4. Wind Safety of the Building Envelope. Whole Building Design Guide. National Institute of Building Sciences. June 15, 2017.

20 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

CHIMNEY

The chimney is an integral part of the overall structural performance and considered part of the load path requirements. Proper anchoring of a masonry chimney structure within the framing of the roof system is critical to resist high wind, prevent damage to roof cover, and prevent chimney from overturning or becoming flying debris.

Chimney and wall damage due to

high winds.

Damage Frequency

1

LOW

2

Construction Practice

Proper reinforcement of chimney.

Mitigation Strategy

4

Chimney structure should be

3

anchored correctly to the roof

system.

Cost & Benefit

Cost range to implement: $–$$

Benefit: A properly anchored

chimney can prevent costly damage

to the roof structure.

5

6

1. Chimney cap

4. Roof/wall system

2. Drip edge

5. Interior fireplace area

3. Chimney flashing

6. Exterior wall of chimney

WIND | 21

GUIDANCE

DIFFICULTY COST

Masonry chimney adjacent to the building envelope should be properly reinforced and anchored back Easy

$

to the wood framing. [1]

Chimney must be less than 5 ft. unless engineered.

Easy

$

Masonry chimney sitting on top of a deck and that penetrates the balloon frame should be properly Easy

$$

reinforced and engineered.

Framed chimneys that penetrate roof structure around metal flue on top of roof should be properly Easy

$$

anchored, balloon framed, and engineered.

Framed chimneys adjacent to the building envelope around metal flue should be properly anchored Easy

$$

and attached to the structure.

RESOURCES

1. 2020 FORTIFIED HomeTM Standard. Insurance Institute for Business & Home Safety (IBHS).

22 | WIND

HUD.GOV

VOLUME 1: WIND

DESIGNING FOR NATURAL HAZARDS

A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

ROOF-MOUNTED EQUIPMENT

Proper fastening of equipment is critical to resist high wind, prevent damage to roof cover, and prevent equipment from becoming flying debris. Damaged equipment can impair the operation of the facility, and the equipment can detach and become damaging wind-borne debris. In addition, water can enter the building where equipment has been displaced or damaged. The most common problems typically relate to inadequate equipment anchorage, inadequate strength of the roof structure to support the equipment, and corrosion of equipment and connectors.

Damaged HVAC unit.

Damage Frequency

LOW

Construction Practice

Attachment to roof should not

compromise roof system and should

1

be engineered on the basis of the

roof truss system.

Mitigation Strategy

2

Proper fastening and anchoring of

equipment.

3

Cost & Benefit

Cost range to implement: $–$$

Benefit: Minimizes damage to the

roof system.

1. Corrosion-resistant material

2. Anti-vibration mounts and supports

3. Roof drainage features

WIND | 23

GUIDANCE

DIFFICULTY COST

HVAC attachments to roof should not compromise roof system and should be engineered per site Easy

$

location. Proper flashing is critical. [1,2]

Ground mounting of solar panels is optimal wherever possible. [3]

Easy

$$

Solar (photovoltaic [PV]) should be installed at “zero tilt.” Panels should be rated for wind zone and designed for building location design wind speed. Panels should be rated for snow/hail as appropriate Easy

$

for location. Attachment to roof should not compromise roof system and should be engineered per site location. Proper flashing is critical. [3]

Ground mounting of HVAC is optimal wherever possible. [1,2]

Easy

$

Ground mounting of deck is optimal wherever possible. [1,2]

Easy

$

Deck attachments to roof should not compromise roof system and should be engineered per site Easy

$$

location. Proper flashing is critical. [1,2]

RESOURCES

1. Attachment of Rooftop Equipment in High-Wind Regions. USVI-RA-2. FEMA. March 2018.

2. Section 5.1.3.4, Rooftop Equipment. Mitigation Assessment Team Report: Hurricanes Irma and Maria in Puerto Rico.

FEMA P-2020. October 2018.

3. Wind Design for Solar Arrays. PV2-2017. Structural Engineers Association of California.

24 | WIND

HUD.GOV

REFERENCES

FEMA’s Interactive Strong Wind Risk Map illustrates the risk by county: https://hazards.fema.gov/nri/strong-wind.

Federal Emergency Management Agency (FEMA)

Mitigation Assessment Team Report: Hurricane Michael in Florida. FEMA P-2077. 2020.

https://www.fema.gov/sites/default/files/2020-07/mat-report_hurricane-michael_florida.pdf.

Mitigation Assessment Team Report: Hurricane Harvey in Texas. FEMA P-2022. 2019.

https://www.fema.gov/sites/default/files/2020-07/mat-report_hurricane-harvey-texas.pdf.

Mitigation Assessment Team Report Hurricanes Irma and Maria in Puerto Rico. FEMA P-2020. 2018.

https://www.fema.gov/sites/default/files/2020-07/mat-report_hurricane-irma-maria-puerto-rico_2.pdf.

Best Practices for Minimizing Wind and Water Infiltration Damage. RA 2. FEMA. 2019.

https://www.fema.gov/sites/default/files/2020-07/minimizing-wind-water-damage_hurricane-michael_florida.pdf.

Wind Damage vs. Water Damage: What You Need to Know When Filing a Claim.

https://www.fema.gov/fact-sheet/wind-damage-vs-water-damage-what-you-need-know-when-filing-claim.

FEMA’s interactive Tornado Risk Map illustrates the risk by county:

https://hazards.fema.gov/nri/tornado.

HUD.GOV

WIND | 25

Manufactured Housing Institute (MHI)

Review of HUD’s Report of the Impact of Hurricane Charley on Manufactured Homes. MHI. 2006.

http://www.manufacturedhousing.org.php56-9.dfw3-2.websitetestlink.com/wp-content/uploads/2016/09/513temp.pdf.

National Institute of Standards and Technology (NIST)

Technical Investigation on the May 22, 2011, Tornado in Joplin, Missouri. NIST. 2011.

https://nvlpubs.nist.gov/nistpubs/NCSTAR/NIST.NCSTAR.3.pdf.

Structural Extreme Events Reconnaissance (StEER) Program

StEER Hurricane Michael P-VAT Report. 2018.

https://www.floridabuilding.org/fbc/publications/Research_2018-2019/STEER_Hurricane-Michael-P-VAT-Report.pdf.

26 | WIND

HUD.GOV

MAY 2023

Document Outline

VOLUME 1: WIND DESIGNING FOR NATURAL HAZARDS A RESILIENCE GUIDE FOR BUILDERS & DEVELOPERS

ACKNOWLEDGMENTS

HUD’s Office of Policy Development and Research:

Technical Advisory Group:

USERS

PRODUCERS

PUBLIC INTEREST

Additional Wind Task Group Members

Authored by Home Innovation Research Labs

DISCLAIMER

FOREWORD

TABLE OF CONTENTS

INTRODUCTION TO VOLUME 1: WIND

BACKGROUND

HOW TO USE THE GUIDES

Defining Wind Damage and Resilient Construction

Frequency of Damage Type

Prioritizing High-Frequency Damage for Resilience

Grouping Resilience Practices

NEXT STEPS AND FUTURE RESEARCH

OPENINGS—SHUTTERS

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

ROOF DECK AND UNDERLAYMENT

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

HIGH-WIND ROOF COVERING

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

CONTINUOUS LOAD PATH

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

GARAGE DOORS

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

WALL SYSTEM

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

SOFFIT

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

PRESSURIZATION DESIGN

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

CHIMNEY

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

ROOF-MOUNTED EQUIPMENT

Damage Frequency

Construction Practice

Mitigation Strategy

Cost & Benefit

RESOURCES

REFERENCES

Federal Emergency Management Agency (FEMA)

Manufactured Housing Institute (MHI)

National Institute of Standards and Technology (NIST)

Structural Extreme Events Reconnaissance (StEER) Program