This document was prepared by

URS Group, Inc.

200 Orchard Ridge Drive, Suite 101

Gaithersburg, MD 20878

Acknowledgements

Federal Emergency Management Agency (FEMA)

L. Gina White, FEMA Region IV, Mitigation, Project Monitor

David Kennard, FEMA Region IX, Mitigation

Daniel Powell, FEMA Region IX, Mitigation

Dennis Tewksbury, FEMA Region I, Mitigation

Christopher Hudson, FEMA HQ, Mitigation

State of California

Ernylee Chamblee, California Department of Forestry and Fire Protection

Greg Griswold, California Department of Forestry and Fire Protection (San Diego Unit)

Tom O’Keefe, California Department of Forestry and Fire Protection (San Bernardino Unit)

Ken Worman, Governor’s Office of Emergency Services

Local California Officials

Cliff Hunter, Rancho Santa Fe Fire Protection District

Clay Westling, City of San Diego

Bill Metcalf, North County Fire District

Technical Assistance Contractor Team

Christopher M. Barkley, PE, URS Group, Inc., Task Order Coordinator

Diana Burke, ELS, URS Group, Inc.

Sherry Crouch, PE, URS Group, Inc.

Michael Gayrard, URS Group, Inc.

Rich Schell, RPF #1978, RWS Consulting

Thomas L. Smith, AIA, TLSmith Consulting, Inc.

Chris White, Anchor Point Group

Cover photo: Anchor Point Group, Boulder, CO

FS No. 1 – Wildland/Urban Interface Construction	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08	 Page 1 of 5

Wildland/Urban

Interface Construction

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 1

Purpose 

To provide information about wildfire behavior and recommendations for building design and

construction methods in the wildland/urban interface. Implementation of the recommended

design and construction methods can greatly increase the chances of a building’s survival in a

wildfire (see Figure 1).

Background

Wildfires are a common, natural, and essential occurrence in the forests, woodlands,

brushlands, and grasslands of the United States. When conditions are acceptable, fire

professionals use fire to revitalize the ecosystem and reduce accumulated vegetation that can

fuel a wildfire under certain conditions.

Although the severity and timing of fire seasons vary widely from region to region, wildfires often

pose a threat to lives, property, and resources. During an average fire season, hundreds of

homes are damaged or destroyed by wildfire, and in extreme fire conditions, thousands of homes

can be damaged or destroyed. Severe fire weather in areas with significant amounts of wildland

fuels can lead to extreme fire behavior.

Wildland fuels vary throughout the United States. In the Pacific northwest and the Lake States,

forests are the predominate wildland fuel. In southern California, chaparral brush predominates.

The plains states have grass and oak woodlands, New Jersey has Pine Barrens, and the

southeast has pine and hardwood forests.

Figure 1. A home in the wildland/

urban interface that survived

a wildfire (Anchor Point Group,

Boulder, CO).
Page 2 of 5	 09/08	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 1 – Wildland/Urban Interface Construction

Wildfires can damage buildings through direct flame contact, convection (heat that rises from

a fire and creates a smoke column), conduction (heat that transfers through material such as

metal roofs and railings), and radiation (heat from a fire next to the building). Wildfires can also

create burning embers that rise in the smoke column and fall on buildings. Firebrands (large

pieces of wind-driven, burning material) can be blown through windows or lodged against a

building and lead to ignition of the building.

Traditional efforts to protect buildings from wildfires have focused on fighting the fire before

it reaches the buildings. With the expansion of residential construction into previously

undeveloped forests and wildlands, more buildings are now at risk from wildfires. Fighting

or suppressing the fire is often difficult or impractical; buildings must therefore also be

constructed to be fire-resistant. No building can be completely fireproof, but implementing the

recommendations that are described in these Fact Sheets should greatly reduce the potential for

damage to a building and greatly increase its chance of survival.

Construction in the Wildland/Urban Interface

The following factors affect the probability that a building will survive a wildfire:

•	 Topography and weather

•	 Defensible space

•	 Building envelope

•	 Community infrastructure

Topography and Weather

Wildfires generally follow or are driven by terrain and weather. Buildings at the top of a canyon

or ridgeline, at mid-slope, or in a ravine have a higher risk for damage from a wildfire due to the

interaction of these features with strong winds than at locations such as valley bottoms. When

a construction site is selected, the topographic features on and surrounding a site should be

evaluated for their potential contribution to the exposure of a building to a wildfire. A building’s

configuration and location on a site should be predicated on minimizing the risk from these

topographic features.

See Fact Sheet #3, Selecting the Construction Site.

Defensible Space 

Wildfires travel quickly in areas where vegetation is dry and abundant. A defensible space

around a building can improve the probability that the building will survive a wildfire. A defensible

space is an area where combustible material, including vegetation, has been treated, cleared or

modified to slow the rate and intensity of an advancing wildfire and to create a safer area for firesuppression operations to occur. Buildings surrounded by zones of non-vegetated areas or areas

populated by fire-resistant vegetation are more likely to survive.

See Fact Sheet #4, Defensible Space.
FS No. 1 – Wildland/Urban Interface Construction	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08	 Page 3 of 5

Building Envelope 

During a wildfire, combustible exterior building components such as roof coverings, siding, and

decks can ignite, leading to severe damage to or total loss of the building. Therefore, the use

of noncombustible or fire-resistant materials should be considered for exterior components.

Figure 2 shows the components of the building envelope.

Also critical is the configuration of the noncombustible or fire-resistant materials. Unless

construction measures that provide protection from a wildfire are implemented, heat and

embers can penetrate the building envelope at vents, unsealed mechanical or electrical

openings, and through windows broken by heat or wind-blown firebrands. When these openings

are penetrated, the building can burn from the inside out.

If the envelope has been designed and constructed to be fire-resistant, both the exterior and

interior of the building will be more capable of resisting a wildfire long enough for the danger to

pass or for firefighters to arrive.

See Fact Sheets #5 through #16.

Community Infrastructure

A home that has been constructed to be fire-resistant and has a defensible space may not

be sufficient to prevent damage from a wildfire. Surviving a wildfire may also depend on

infrastructure such as local water resources for firefighting and roads that are designed for

emergency vehicle access. The building site should also have adequate infrastructure to ensure

access for firefighting crews.

See Fact Sheet #17, Community Infrastructure.

Figure 2. The building envelope.

Building Envelope

Vents

Garage door Exterior door

Siding

Roof Deck

Fence

Windows

Eaves

Foundation

Gutters
Page 4 of 5	 09/08	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 1 – Wildland/Urban Interface Construction

Prioritizing Fire-resistant 

Construction Techniques

The risk of wildfire varies greatly and depends

on local fuels, weather, and topography. The risk

at a building site must be determined before the

appropriate design and construction methods

for a new or existing building can be selected

and the measures can be prioritized.

Hazard and Risk Assessments

The foundation of an accurate hazard and risk

assessment is information on wildfire fuels,

weather, topography, assets at risk, and the

probability of a wildfire occurrence. A site can

be in an area with a very high hazard (highly

vulnerable to wildfire) but have a low risk of

wildfire, such as a site at a high altitude. This

information can be used to designate Fire

Severity Zones. The zones can then be given

a rating, from low to extreme, as shown in

Figure 3.

A hazard and risk assessment can help

determine the level of mitigation that is needed for a building. The assessment, which can be

conducted at a regional, state, or local level, needs to be both credible and professional to

ensure that the analysis is accurate, comprehensive, and verifiable. Some regional, state, and

local agencies produce hazard risk maps similar to those shown in Figures 3 and 4. These maps

may be found in state, tribal, and local agency hazard mitigation plans that have been approved

by the Federal Emergency Management Agency (FEMA).

New Buildings

For new construction, FEMA recommends following the design and construction guidance

provided in this series of Fact Sheets.

Existing Buildings

FEMA recognizes that it may not be financially possible for the homeowner to implement all

of the measures that are recommended in this series of Fact Sheets. FEMA recommends

that homeowners consult with local fire and building code officials or other fire management

specialists to perform a vulnerability assessment and develop a customized, prioritized list of

recommendations for remedial work on defensible space and the building envelope.

Helpful information about the vulnerabilities of the building envelope is available at http://

firecenter.berkeley.edu/default.htm. The Homeowner’s Wildfire Assessment survey on this

Figure 3. Example of a fire hazard rating map.

Fire hazard ratings can help determine the

level of mitigation that is necessary for wildfire

management (Anchor Point Group, Boulder, CO).
FS No. 1 – Wildland/Urban Interface Construction	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08	 Page 5 of 5

website is a helpful tool that property owners can use to learn about the specific risks a

particular building has and the measures that can be taken to address them.

Construction Standards

Many communities enforce regulations regarding where and how buildings may be sited,

designed, and constructed. The regulations, however, refer to minimum standards. Individual

property owners have the option to exceed these standards, and doing so very often increases

the probability that the home will survive a wildfire.

Resources

Center for Fire Research and Outreach. University of California, Berkeley: College of Natural

Resources. http://firecenter.berkeley.edu/default.htm.

Christman, L. 2008. Trial by Fire: Can Your Home Take the Heat? Redding.com: Home & Garden.

http://www.redding.com/ news/2008/Feb/16/trial-fire-can-your-home-take-heat/.

Underwood, J. 1995. “Fire-Resistant Details.” Fine Homebuilding 96: 90–93. http://www.

taunton.com/finehomebuilding/how-to/articles/fire-resistant-details.aspx.

Figure 4. Example of a fuel model

map. Fuel models that demonstrate

the location of combustible

vegetation are part of the foundation

for fire behavior calculations (Anchor

Point Group, Boulder, CO).

FS No. 2 – Summary of Recommendations	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 5

Summary of Wildfire 

Construction 

Recommendations

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 2 

State and local codes should include requirements for wildfire mitigation for both new

construction and upgrades to existing buildings in wildfire zones. In areas where buildings are

particularly vulnerable to the risk of wildfire, implementing measures that exceed the codes can

improve the probability that a building will survive a wildfire.

The Unified Hazard Mitigation Assistance Guidance and the Wildfire Mitigation Policy for the

Hazard Mitigation Grant Program (HMGP) and Pre-Disaster Mitigation (PDM) Program provide

information on which activities are considered eligible for funding by the Federal Emergency

Management Agency (FEMA) for wildfire mitigation activities.

This series of Technical Fact Sheets from FEMA provide information about how to minimize the

potential for damage to or destruction of buildings in wildfire zones from wildfires. The information

pertains to both new and existing buildings.

The Fact Sheets are available on the FEMA website (www.fema.gov) as Adobe Portable Document

Format (PDF) files. You must have Adobe Reader to view the PDF files. The latest version of Adobe

Reader is recommended and can be downloaded from www.adobe.com.

The following is a summary of the recommendations contained in Fact Sheets #3 through #17.

Fact Sheet #3: Selecting the Construction Site

Topographic features such as slopes and canyons, local

vegetation, and weather can greatly influence wildfire behavior.

Homebuilders should consider these factors carefully when

selecting a construction site
Page 2 of 5	 09/08	 Home Builder’s Guide to Construction in Wildfire Zone	 FS No. 2 – Summary of Recommendations

Fact Sheet #5: Roofs

Of the components of the building envelope, the roof is the most

vulnerable in a wildfire because of its size and orientation. The

probability that a home will survive a wildfire is greatly influenced

by the components of the roof assembly. Class A rated roof

assemblies with noncombustible coverings are recommended.

Fact Sheet #6: Eaves, Overhangs, and Soffits

Windborne embers and convective and radiant heat can be

trapped near eaves and soffits, which can ignite if not constructed

of noncombustible or fire-resistant materials. Eaves with short

overhangs and flat soffits with a minimum of a 1-hour fireresistance rating are recommended.

Fact Sheet #7: Exterior Walls

How well exterior walls are able to resist a wildfire depends largely

on the materials used to construct the wall. Exterior wall coverings

that are noncombustible or fire-resistant and not susceptible to

melting are recommended. A minimum fire-resistance rating of

1 hour for the wall assembly is recommended

Fact Sheet #4: Defensible Space

Creating a defensible space, which can often be done by the

homeowner, is recommended. A defensible space is an area

around a home in which vegetation, debris, and other types

of combustible fuels have been treated, cleared, or reduced.

Landscape management creates a barrier between a home and a

wildfire. Without a defensible space, firefighters may not attempt to

protect the home because doing so would be too hazardous.
FS No. 2 – Summary of Recommendations	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 3 of 5

Fact Sheet #9: Gutters and Downspouts

Combustible debris such as leaves and pine needles can become

trapped in gutters. The debris can be ignited by flying embers or

firebrands during a wildfire, and the fire can spread to the roof.

Noncombustible leaf guards over gutters and gutters constructed

of noncombustible materials are recommended.

Fact Sheet #10: Windows and Skylights

Flames, firebrands, radiant heat, and failed frames can cause

glazing to break or otherwise fail. Glazing (glass, plastic, or

translucent material) that fails allows easy passage of embers and

hot gases into the interior of a building. Insulated glazing units are

recommended. The fire rating of window assemblies should be

commensurate with the fire rating of the wall.

Fact Sheet #11: Exterior Doors

Combustible doors and frames can be ignited in a wildfire, and

openings between the door and frame and glass in the door can

be penetrated by flames, hot gases, or embers. The fire rating of

the door should be commensurate with the fire rating of the wall.

Weatherstripping and noncombustible or fire-resistant trim are

recommended. 

Fact Sheet #8: Vents

Embers and hot gases can be blown or pulled into vent openings

and enter attic spaces, crawlspaces, and ductwork, leading to

ignition of the interior of the building. Vents that are a minimum

of 10 feet from property lines and other buildings, constructed of

metal products, and have corrosive-resistant metal mesh screens

are recommended.
Page 4 of 5	 09/08	 Home Builder’s Guide to Construction in Wildfire Zone	 FS No. 2 – Summary of Recommendations

Fact Sheet #14: Landscape Fences and Walls

Once ignited, a fence constructed of combustible materials that is

attached to or near a building can ignite the building. Fences and

walls constructed of noncombustible materials such as concrete,

stone, and masonry are recommended. Attaching a fence or

wall to the building should be avoided unless the fence or wall is

constructed of noncombustible materials

Fact Sheet #15: Fire Sprinklers

The interior of a building can ignite from a wildfire even when the

exterior does not. Interior and exterior fire sprinklers can prevent

substantial damage to the building, protect nearby buildings, and

prevent the fire from igniting nearby combustible vegetation.

Fact Sheet #13: Decks and Other Attached Structures

Embers, firebrands, and hot gases can become trapped under

decks and other attached structures. Decks constructed of heavy

timber or noncombustible materials are recommended. Isolating

the attached structure by surrounding it with noncombustible

material such as gravel, brick, and concrete pavers, and enclosing

the underside of the deck with fire-resistant skirting are also

recommended.

Fact Sheet #12: Foundations

Embers, firebrands, and hot gases can ignite combustible

foundation walls and penetrate crawlspace vents and breached

basement windows. Walls, vents, and windows in closed

foundations should be constructed in accordance with the

guidance in these Fact Sheets. In homes with open foundations,

protecting the underside of the floor structure with fire-resistant

materials is recommended.
FS No. 2 – Summary of Recommendations	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 5 of 5

Fact Sheet #17: Community Infrastructure

Access roads and driveways that are wide and strong enough

to accommodate emergency vehicles and provide access for

firefighting efforts are necessary. Water resources for wildfire

suppression must be accessible. Roads and water sources should

be well marked on signs constructed of fire-resistant materials for

ease of use by emergency response personnel.

Fact Sheet #16: Utilities and Exterior Equipment

Most utilities require penetration of the building’s envelope

for ducting and conduit. Utility connections should be installed

underground, if possible, and gaps and penetrations in exterior

walls and roofs should be sealed with fire-resistant products. Fuel

should be stored underground or surrounded by a noncombustible

barrier.

FS No. 3 – Selecting the Construction Site	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 4

Selecting the 

Construction Site

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 3

Purpose

To help property owners who plan to build homes or other structures in wildfire zones understand

the relationship between wildfire behavior and fuels, weather, and topography so they can select

construction sites that minimize the potential for damage from wildfires. The guidance listed in

this Fact Sheet applies only to new buildings.

Key Issues

•	 Wildfires spread more quickly on upsloped terrain than

on level terrain (see Figure 1). Topographic features such

as slopes, saddles, ridges, and canyons can therefore

influence wildfire behavior (see below for a description of

these features). The interaction of wind and radiant heat

with some of the features is also an important factor in

wildfire behavior.

•	 The direction a slope faces influences the growth of

vegetation, and vegetation influences wildfire behavior

because it provides fuel for the wildfire.

•	 Implementing the fire-mitigation measures described in

the other Fact Sheets cannot entirely offset the potential

for damage from a wildfire at high-risk sites with

topographic and vegetation features that can contribute

to extreme fire behavior.

Topography 

•	 Sloped terrain. Wind-driven wildfires follow wind direction and are minimally influenced by

topography. In the absence of a strong wind, wildfire follows topography, burning primarily

upslope and up-canyon. Wildfires spread upslope quickly because heat rises and preheats

and ignites fuels such as buildings and

vegetation.

•	 Saddles. Where a valley crosses a ridge,

a saddle is created between two peaks

(see Figure 2). Saddles act as wind funnels

and are one of the most hazardous

locations for homes in terms of wildfire.

Figure 1. Fire spreads more quickly on

upsloped terrain than on level terrain.

Fuel, topography, and weather are the three

principal environmental elements that affect

wildfire behavior. Fuels (vegetation) and

local topography should be considered when

choosing a site for a home to increase the

chance the home will survive a wildfire.
Page 2 of 4	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 3 – Selecting the Construction Site

•	 Ridgetops and hilltops. Wind speeds on 

ridgetops and hilltops can be unpredictable

but tend to be higher than those in the

surrounding lower areas because of the

higher elevation and because wind speed

increases as it flows over abrupt changes

in topography. Buildings in these locations

can have 360-degree downhill exposure to

wildfire.

•	 Canyons. A wildfire at the bottom of a

vegetated canyon can lead to extremely

hazardous conditions upslope. A canyon

acts like a chimney, collecting hot gases

and directing superheated convection and

radiant heat upslope. Canyons funnel winds

(see Figure 3) that can fan a fire and lead to

extreme fire behavior (rapid spread of the

wildfire and ignition of an entire area). An

entire canyon can pre-heat from rising hot air

and gases and explode in flames, creating a

firestorm.

Vegetation

•	 Vegetation acts as a fuel for wildfires. Vegetation both on and adjacent to a site can affect

the probability of damage to a building from a wildfire. Characteristics of vegetation such as

density, continuity, and type can influence wildfire behavior (see Fact Sheet #4, Defensible

Space, for more information).

•	 South- and west-facing slopes generally retain less moisture, produce less vegetation, and

dry out earlier in the year than north- and east-facing slopes. Fires on dryer slopes tend to

ignite more easily, travel more rapidly, and burn out faster as light fuels are consumed. The

more heavily vegetated moist slopes have a lower potential for ignition but can sustain a more

intense fire of longer duration than dry slopes.

Guidance 

By understanding how topography and vegetation can influence wildfire behavior, property owners

can select construction sites in wildfire zones that reduce the potential for damage to a building

from a wildfire. Following the guidance listed below can increase the probability that a building will

survive a wildfire.

•	 Avoid selecting a construction site along a gully or in a narrow canyon.

•	 Avoid selecting a construction site in or adjacent to a saddle or narrow mountain pass.

•	 Avoid constructing a home adjacent to or on a steep slope. If a ridgetop site is selected, choose

Figure 2. Wind behavior over a saddle.

Figure 3. Wind behavior through a canyon.
FS No. 3 – Selecting the Construction Site	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 3 of 4

an area that allows for a minimum

50-foot setback from wildland

vegetation on the downslope side

(see Figure 4). Increase the setback

at sites with heavier fuels such as in

a forested environment. Implement

the measures in Fact Sheet #4,

Defensible Space; Fact Sheet #12,

Foundations; and Fact Sheet #13,

Decks.

•	 Orient the narrowest wall of the

building toward the likely path of

a wildfire to minimize the risk of structural ignition. Orient the building based on wind and

fuels so that debris, embers, and firebrands do not accumulate next to the building’s walls,

especially near the inside corners of entries and other off-set walls.

•	 Minimize the number of windows on the side of the building facing the likely path of a wildfire

to reduce the risk of radiant heat or firebrands and flying debris breaking the windows, allowing

the fire to enter the building.

Considerations

•	 Consider the vegetation characteristics on and adjacent to the site including density, continuity,

and type. If the site has heavy, continuous vegetation, a vegetation management plan may be

needed to reduce the hazard. Creating a defensible space can enhance fire resistance (see

Fact Sheet #4, Defensible Space).

•	 Consider access to the home. Steep driveways and narrow roads can limit accessibility by firefighting equipment (see Fact Sheet #17, Community Infrastructure).

•	 Evaluate the vulnerability to fire of neighboring properties. If the neighboring properties have

fire hazards but the neighbors are unwilling to cooperate in developing a mutual defensible

space, consider that information in selecting fire-resistance measures for the building.

Effectiveness

The effectiveness of the recommended measures can vary significantly, depending on the

interaction of fuels, weather, topography, and wildfire behavior.

Resources

Barkley, Y.C., C. Schnepf, and J. Cohen. 2005. Protecting and Landscaping Homes in the 

Wildland/Urban Interface. Station Bulletin #67. Moscow, Idaho: Idaho Forest, Wildlife and

Range Experiment Station. www.treesearch.fs.fed.us/pubs/22257.

California Department of Forestry and Fire Protection. www.fire.ca.gov.

California Fire Safe Council. www.firesafecouncil.org.

Figure 4. Example of setback from wildland vegetation.

50 feet
Page 4 of 4	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 3 – Selecting the Construction Site

Firewise Communities Program. www.firewise.org/newsroom/faq.htm.

National Wildfire Coordinating Group. www.nwcg.gov.

Slack, P. 2000. Firewise Construction Design and Materials. Colorado State Forest Service.
FS No. 4 – Defensible Space Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 4

Defensible Space

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 4 

Purpose

To provide information about creating a defensible space to reduce the potential for damage to

homes from wildfires. Guidance pertains to both new and existing buildings.

Background

A defensible space is an area around a building in which vegetation, debris, and other types of

combustible fuels have been treated, cleared, or reduced to slow the spread of fire to and from

the building. Information about local vegetation, weather, and topography is used to determine

the Fire Severity Zone of an area, which can help determine the most effective design of a

defensible space.

A defensible space is one of the most cost-effective ways to protect a building from a wildfire and

can often be created by the property owner.

Key Issues 

•	 Wildland vegetation such as grass, brush, and timber can be extremely combustible. The

vegetation can burn with great intensity and produce firebrands and burning embers that can

become wind-driven hazards.

•	 Landscape vegetation can be as combustible as wildland vegetation.

•	 Combustible plants have these characteristics:

– Volatile resins and oils (generally aromatic

when crushed)

– Narrow leaves or long, thin needles such as

conifer needles

– Waxy or fuzzy leaves

– An accumulation of dead leaves and twigs on

and under the plant

– Loose or papery bark

•	 A wildfire can move horizontally from shrub to

shrub and tree to tree.

•	 A wildfire can also travel vertically from the ground up into the treetops, resulting in a

catastrophic crown fire (a fire that can travel at an incredible pace through the top of a forest).

Figure 1 shows a fire that is spreading vertically from grasses to shrubs to low branches.

•	 Accessory buildings and structures and other items commonly found in yards that are made

Figure 1. Fire spreads vertically through

vegetation (Anchor Point Group, Boulder, CO).
Page 2 of 4	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 4 – Defensible Space

of combustible materials can also put an

otherwise fire-resistant building at risk of

ignition and destruction.

•	 Combustible vegetation and materials around a

building (see Figure 2) can:

– Increase the risk of building ignition

– Restrict the space necessary to provide

firefighters a relatively safe place to protect

a building

– Increase the chance that a building on fire

will ignite adjacent wildlands

Guidance

•	 Assess both the horizontal and vertical aspects of vegetation when designing the defensible

space.

•	 To prevent the horizontal spread of wildfire, thin shrubs and trees so the crowns do not

intersect and there is space between individual shrubs and trees.

•	 To prevent the vertical spread of wildfire, keep the lowest tree branches pruned and trimmed

to maintain vertical separation from the top of shrubs and grasses to the lowest tree branches.

The vertical distance needed will vary significantly, depending on the species of tree and

composition of the understory.

•	 Create three concentric zones around the building (see Figure 3). Zone 1, the zone closest

to the building, normally has the greatest need for fuel modification with progressively less

modification in the other two zones. The higher the Fire Severity Zone, the larger the concentric

zones should be. Consult the local or state fire agency for assistance. The three zones are

discussed further below.

Zone 1

•	 Eliminate all combustible materials in Zone 1 (within 30 feet of the home) such as fire-prone

vegetation, firewood stacks, combustible patio furniture, umbrellas, and dimensioned lumber

decking (see Figure 4). Desirable substitutions include irrigated grass, rock gardens, stone

patios, metal patio furniture, and noncombustible decking (see Fact Sheet #13, Decks and

Other Attached Structures).

•	 Before fire season begins, remove combustible litter on roofs and gutters and trim tree

branches that overhang the roof and chimney (see Fact Sheet #9, Gutters).

Zone 2

•	 Ensure that Zone 2 includes only individual and well-spaced clumps of trees and shrubs

and/or a few islands of vegetation that are surrounded by areas with noncombustible

materials.

Figure 2. Combustible materials adjacent to a

building create a hazard (Anchor Point Group,

Boulder, CO).
FS No. 4 – Defensible Space Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 3 of 4

•	 Use hardscape features such as driveways and paved or gravel walkways or patios to create

firebreaks throughout the yard.

•	 Plant fire-resistant, low-volume vegetation that retains moisture well and needs minimum

maintenance such as pruning and removing dead and dying branches.

•	 Separate auxiliary structures such as a detached garage, pump house, pergola, and utility shed

from the home by at least 50 feet. Increase the distance if the structure is used for the storage

of combustible materials.

•	 Comply with recommended construction practices related to fire resistance for auxiliary

structures. See Fact Sheets #5 to #16 for guidance on planning and designing a structure in a

wildfire zone.

•	 Ensure that patio furniture is either made of

noncombustible material such as metal or is

at least 30 feet away from the building. Store

patio furniture in a location that is protected

from ignition by a wildfire.

•	 Place woodpiles at least 30 feet from the

building and store the wood in a vegetationfree zone such as a graveled area.

•	 Store fuel tanks away from a structure at the

minimum distance that is required by code

or greater (see Fact Sheet #16, Utilities) and

place underground or on a noncombustible

pad.

Figure 4. A noncombustible ground cover in Zone 1

helped this home survive a wildfire (Anchor Point

Group, Boulder, CO).

Figure 3. The three concentric zones of defensible space.
Page 4 of 4	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 4 – Defensible Space

Zone 3

Reduce fuels that are farther than 100 feet from the building by thinning and pruning vegetation

horizontally and vertically as discussed above. Thinning and pruning in Zone 3 can be more

limited than in Zone 2. The goals in Zone 3 are to improve the health of the wildlands and help

slow an approaching wildfire. Zone 3 is also an aesthetic transition between the more heavily

modified Zone 2 and the unmodified surroundings.

Considerations

•	 Consult the local or state fire agency or qualified fire management specialist about codes,

requirements, and standards related to defensible space. Codes, requirements, and standards

normally represent the minimum that should be done. Consideration should be given to

providing enhanced protection measures beyond the minimum recommended or required.

•	 Maintaining a defensible space requires routine maintenance of vegetation, which includes

pruning and removing dead branches and leaves. Characteristics of low-maintenance

plants are:

– Drought-resistant

– Pest-resistant

– Native to the area

– Noninvasive

– Slow-growing

– Wind-resistant

– Sustainable without supplemental fertilization

•	 Vegetation modification must be performed in compliance with local, state, and federal

environmental regulations.

Effectiveness

All mitigation measures listed in this Fact Sheet are effective in all Fire Severity Zones.

Resources

Barkley, Y.C., C. Schnepf, and J. Cohen. 2005. Protecting and Landscaping Homes in the 

Wildland/Urban Interface. Station Bulletin #67. Moscow, Idaho: Idaho Forest, Wildlife and

Range Experiment Station. www.treesearch.fs.fed.us/pubs/22257.

Firewise Communities Program. www.firewise.org/newsroom/faq.htm.

National Fire Protection Association (NFPA) 1144: Standard for Reducing Structure Ignition

Hazards from Wildland Fire. 2008. http://dnrc.mt.gov/forestry/Fire/Prevention/documents/

WUIrewrite/ NFPA1144.pdf.

National Wildfire Coordinating Group. www.nwcg.gov.
FS No. 5 – Roofs Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 1 of 5

Roofs

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 5

Purpose

To provide general guidance on the design and construction of roof assemblies on buildings in

wildfire zones. Guidance pertains to both new and existing buildings.

Key Issues 

•	 Roof assemblies are the most vulnerable

component of the building envelope in

a wildfire because of their horizontal

orientation and size.

•	 Embers and firebrands can ignite the roof

covering, other roof components, and debris

on the roof. Once the roof has ignited, the fire

commonly propagates into the interior of the

building, resulting in substantial damage to

or total loss of the building.

•	 The probability that a home will survive a wildfire is greatly influenced by the components of the

roof assembly. The type and arrangement of the components govern their potential for ignition

and their propensity to transfer heat into the interior of the building.

•	 The complexity of the roof’s shape also influences the potential for ignition. A roof with valleys

and roof/wall intersections where combustible debris such as leaves and needles can collect

has more potential for ignition than a roof without them.

Fire-rated Roof Assemblies

The resistance of roof assemblies to external fire

is rated by the American Society of Testing and

Materials (ASTM), using test method E108. The

method includes measurements of the surface

spread of flame, the ability of the roof assembly to

resist fire penetration from the exterior of the building

to the underside of the roof deck, and the potential

for the roof covering to develop flying brands of burning material. Roof assemblies are rated

Class A (highest rating), B, or C. Assemblies that fail the test (do not meet the Class A, B, or C

criteria) are unrated.

Class A provides the greatest degree of fire resistance, but there is a range of protection within

the Class A rating. For example, some Class A rated assemblies have noncombustible roof

Roof covering: The exterior roof cover or

skin of the roof assembly (e.g., shingles,

tiles, slate, metal panels, roof membrane).

Roof assembly: An assembly of interacting

roof components, including the roof deck,

vapor retarder (if present), insulation

(if present), insulation cover boards (if

present), and the roof covering.

ASTM E 108 test conditions do not

replicate actual wildfire conditions. In

many cases, actual wildfire exposures

are much more severe than those

induced during the testing.
Page 2 of 5	 09/08	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 5 – Roofs

coverings (such as clay or concrete tiles and metal panels), while others have combustible

coverings (such as asphalt shingles and low-slope membranes).

Guidance for New Buildings

Many types of roof assemblies are rated Class A. Recommendations for various components of

roof assemblies that are rated Class A are provided below.

Steep-slope Roof: Covering

A steep-slope roof is a roof with a slope greater than 3:12. The following design and installation

practices are recommended:

•	 Tile. Clay and concrete tile are noncombustible and because of their relatively large thermal

mass, retard the transfer of heat. Lightweight tile products are available, but normal-weight

tiles are recommended because of their greater mass. If tiles are installed over wood battens,

embers may be blown under the tiles and ignite the battens. Fire-retardant-treated battens are

therefore recommended. If tile is used, the following are also recommended:

– Eaves, hips, and ridges. Embers can be blown

under tiles at the eaves, hips, and ridges.

Birds can build nests in the space between

the underlayment and the bottom of the tiles if

the space is accessible, providing combustible

debris that can be ignited by embers. Installing

birdstops at eaves and fully mortaring hips and

ridges are both recommended to avoid the

accumulation of debris under tiles and to keep

embers out (see Figure 1).

– Valleys. Unless special metal flashing is

installed, combustible debris can accumulate in

valleys and then under the tiles. Flat and plain

tiles should be specified to be tightly butted to form a closed valley, and pieces of metal

flashing should be installed under each tile course along the valley centerline. For profiled

tile, lead or flexible flashing should be used, as recommended by the tile manufacturer

(see Figure 2).

•	 Metal shingles and panels. Metal shingles and panels are noncombustible, but they readily

transfer heat. If they are installed over wood battens, fire-retardant-treated battens should be

specified and installed. If shingles or panels are installed over wood decking, 5/8-inch gypsum

Figure 1. A birdstop at the eave.

Birdstops prevent debris 

from accumulating under tiles

Only Class A rated roof assemblies

are recommended for homes in

wildfire zones.
FS No. 5 – Roofs Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 3 of 5

roof board complying with ASTM C 11771 should be

installed over the decking.

•	 Fiberglass-reinforced asphalt shingles. Although a

roof assembly that has fiberglass-reinforced asphalt

shingles can be rated as Class A, these shingles

contain combustible material (e.g., asphalt). If this

type of shingle is used, a 5/8-inch gypsum roof

board that complies with ASTM C 1177 over the

wood decking should be installed for enhanced

protection of the decking. Care needs to be taken

when the shingles are nailed that the nails are not

overdriven.

•	 Wood shingles and shakes. Roof assemblies that

have wood shingles and shakes can be rated

Class A if the shingles or shakes are fire-retardanttreated and a specific cap sheet underlayment is installed. Without the underlayment, the

maximum rating is Class B. Note that when shingles or shakes are fire-retardant-treated, they

cannot be impregnated with preservative treatment.

If fire-retardant-treated shingles or shakes are installed over wood decking, installing

a 5/8‐inch gypsum roof board that complies with ASTM C 1177 over the decking is

recommended in addition to the special underlayment that is required to achieve a

Class A rating.

Steep-slope Roof: Underlayment 

Embers can be blown under some types of steepslope coverings such as tile, slate, and metal

shingles and panels. If tiles become dislodged or

cracked, embers can land on the underlayment

below (see Figure 3). Installing an underlayment

that has enhanced fire resistance is recommended

to provide protection from embers that reach the

underlayment.

An example of an enhanced underlayment is a

mineral-surface cap sheet that is rated for use in

a Class A rated assembly.2 If a mineral-surface

cap sheet is used under metal panels or shingles,

measures should be taken to prevent the metal from bearing directly on the cap sheet and the

cap sheet from abrading the metal (thereby making the metal susceptible to corrosion).

1	Boards that are 5/8-inch thick are type X (“special fire-resistant“). Boards that are 1/2-inch and 1/4-inch thick are

not type X.

2	Although cap sheets are normally the finished surface of a built-up or modified bituminous roof covering, a cap sheet can

also be used as an underlayment.

Figure 3. Displaced tiles allow ember entry.

Figure 2. Special valley flashing to avoid

debris accumulation between and below

tiles (photograph courtesy of MonierLifetile).
Page 4 of 5	 09/08	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 5 – Roofs

Steep-slope Roof: Decking 

Most homes have roof decks that are constructed of wood, typically plywood or oriented strand

board. Fire-retardant-treated decking can be specified to avoid ignition of the deck. For more

protection, 5/8‐inch gypsum roof boards can be specified in addition to the fire-retardanttreated deck.

Although not common in homes, noncombustible decks such as steel or concrete, including

concrete topping over steel decking, can be specified. In addition to being noncombustible,

concrete decks offer great resistance to heat transfer and fire penetration through the deck from

the exterior.

Low-slope Roof: Covering and Underlayment

Low-slope roofs have slopes less than 3:12.

A variety of low-slope roof coverings and

assemblies are available with a Class A

rating.

If a low-slope assembly is selected, the

following recommendations should be

followed:

•	 Polyisocyanurate roof insulation should

be specified (see Figure 4).

•	 A 5/8-inch gypsum roof board that

complies with ASTM C 1177 immediately

below the roof membrane (see Figure 4)

should be specified.

•	 For enhanced fire resistance, in addition to the above recommendations, the roof membrane

should be protected with heavyweight (i.e., 17 pounds per square foot minimum) concrete

pavers (see Figure 5).

– If pavers are placed over a built-up or modified bitumen membrane, a layer of extruded

polystyrene insulation (intended for protected membrane systems) over the membrane

should be specified.

Figure 5. Concrete pavers over

membrane (FEMA 55).

Mortar-faced 

extruded polystyrene

Roof

parapet

Extruded 

polystyrene

Concrete 

pavers

Membrane

Polyisocyanurate 

insulation

Roof 

membrane

5/8-inch 

gypsum board

Roof deck

Figure 4. Components of a low-sloped roof.
FS No. 5 – Roofs Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 5 of 5

– Additionally, for smooth-surfaced built-up and modified bitumen membranes, a sheet

of polyethylene (minimum of 4 mils) should be specified between the membrane and

polystyrene to keep the polystyrene from bonding to the membrane.

– To protect the base flashings, a mortar-faced extruded polystyrene board should be installed

over the base flashing (see Figure 5).

Low-slope Roof: Decking

Roof decking design and construction are the same for steep-slope and low-slope roofs. See the

discussion under steep-slope roofs above.

Guidance for Existing Buildings

For homeowners with roof assemblies that are not Class A rated, the only long-term, reliable

way to reduce roof vulnerability to wildfire is to reroof. Reroofing normally involves removing the

materials above the roof deck and replacing them with new materials. The recommendations that

are listed above for new buildings are applicable to reroofing design and installation.

Roof assemblies that have wood shingles or shakes and are not rated Class A and roofs with

organic-reinforced asphalt shingles are vulnerable to a wildfire. These types of roofs should be

replaced as soon as possible.

Considerations

•	 The homeowner should have roof debris removed from the roof surface and gutters regularly.

•	 Aging does not affect the ignition potential of tile. However, some roof coverings, such as wood

or fiberglass-reinforced asphalt shingles, become more susceptible to ignition as they age. The

roof covering should be replaced before deterioration of the covering significantly degrades

resistance to ignition.

•	 Birdstops should be inspected annually to ensure that they have not fallen out of place.

•	 For recommendations on vents, see Fact Sheet #8, Vents.

•	 For recommendations on gutters and downspouts, see Fact Sheet #9, Gutters and

Downspouts.

Effectiveness

All mitigation measures recommended in this Fact Sheet are effective in all Fire Severity Zones.

Resources

American Society of Testing Materials (ASTM). 2007. Standard Test Methods for Fire Tests of Roof 

Coverings. ASTM E108-07a.

FEMA. 2003. Coastal Construction Manual. FEMA 55.

FS No. 6 – Eaves, Overhangs, and Soffits	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 3

Eaves, Overhangs,

and Soffits

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 6 

Purpose 

To provide guidance on the design and construction of eaves, overhangs, and soffits in wildfire

zones. The guidance pertains to both new and existing buildings.

Key Issues

•	 Windborne embers, convective heat, and radiant heat can be trapped under overhangs and

in the upper portion of exterior walls. Overhangs and walls can ignite if not constructed of

noncombustible or fire-resistant materials.

•	 Typical construction materials for eaves, overhangs, and soffits are not fire-resistant and are

therefore susceptible to ignition by embers and hot gases.

•	 Once an eave, overhang, or soffit has ignited, fire can spread onto the roof, into the attic, or

onto and through the exterior wall.

•	 Soffits normally have vents as part of the attic ventilation system. Unprotected vents can allow

embers and hot gases to enter the attic (see Fact Sheet #8, Vents).

Typical Design and Construction

Eaves. Eaves are located at the down-slope edge of a sloped roof and serve as the transition

between the roof and fascia/wall. An eave typically has a metal edge flashing and gutter that are

attached to a wood fascia trim board.

Overhangs. Overhangs are extensions of the

roof beyond the exterior wall (i.e., the joists,

rafters, or trusses and the decking they support

cantilever past the wall). An overhang protects

the upper portion of the wall that it is attached

to from rainfall, and it also shades the windows

under it from the sun. Overhangs can be open,

in which the trusses/rafters and decking are

exposed (see Figure 1), or enclosed by a soffit.

Soffits. A soffit encloses the underside of slopedor flat-roof overhangs. Soffits are commonly

constructed from fiber-cement panels, metal

panels, stucco, vinyl panels, or wood sheathing.

Metal panels, untreated wood panels, and vinyl

Attic vents

Figure 1. An open overhang. The exposed timber

rafters and decking are susceptible to ignition, and

embers and hot gases can enter the attic through

unprotected vents.
Page 2 of 3	 09/08	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 6 – Eaves, Overhangs, and Soffits 

panels are vulnerable to damage from wildfires. Metal panels conduct heat and can distort and

allow passage of embers and hot gases. Untreated wood panels can ignite, and vinyl panels can

melt and fall away.

Guidance for New Buildings

•	 Consider designing the building without

overhangs (see Figure 2) to avoid the firerelated problems associated with soffits or

minimize as much as possible the extent

of the overhang to reduce the potential for

entrapment of embers and hot gases.

•	 If no overhangs or short overhangs are

unacceptable because of aesthetics or

a desire to protect the walls from rainfall

or windows from the sun, implement the

following recommended measures:

– Enclose overhangs with soffits that have

a minimum 1-hour fire-resistance rating

to prevent embers and hot gases from making contact with the joists, rafters or trusses, or

the underside of the roof decking.

– Use flat, horizontal soffits (see Figure 3) instead of attaching the soffits to the sloped joists,

which creates sloped soffits. A flat soffit reduces the potential for entrapment of embers

and hot gases.

•	 For the fascia, use noncombustible or fire-resistant materials (e.g., fire-retardant-treated

lumber, fiber-cement board).

•	 For eave vents, follow the guidance in Fact Sheet #8, Vents.

Embers and 

hot gases 

from fire

Exterior wall 

cladding

Fascia

Gutter

Rafter

Underside of 

roof deck

Figure 3. An enclosed 

overhang with a

horizontal soffit.

Figure 2. An eave with essentially no overhang.

Gutter

Embers and hot

gases from fire

Horizontal

soffit

Exterior 

wall 

cladding

Fascia

Rafter

Underside 

of roof deck

Soffit 

framing
FS No. 6 – Eaves, Overhangs, and Soffits	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 3 of 3

Guidance for Existing Buildings

•	 Install a soffit under open overhangs according to the guidance provided above.

•	 Evaluate the fire-resistance of existing soffits and replace soffits that are not fire-resistant

according to the guidance provided above. Some existing soffits (such as those constructed of

plywood) can be covered with a noncombustible or fire-resistant material such as fiber-cement

board or stucco.

•	 In very high Fire Severity Zones, install exterior 5/8-inch fire-resistant gypsum board between

the existing and new soffit materials for enhanced fire resistance.

•	 If the fascia is combustible, cover the fascia board with a noncombustible or fire-resistant

material (e.g., fire-retardant-treated lumber, fiber-cement board).

•	 For eave vents, follow the guidance in Fact Sheet #8, Vents.

Considerations

Planting combustible vegetation under eaves and overhangs should be avoided (see Fact

Sheet #4, Defensible Space).

Effectiveness

All mitigation measures listed in this Fact Sheet are effective in all Fire Severity Zones.

Resources

Under Eave SFM Standard 12-7A-3, 2001 California Referenced Standard Codes (Part 12,

Title 24, C.C.R.). http://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_SFM_12-

7A-3_Test_Standards.pdf.

FS No. 7 – Exterior Walls Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 3

Exterior Walls

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 7

Purpose

To provide guidance on the design and construction of exterior walls in wildfire zones. Guidance

pertains to both new and existing buildings.

Key Issues 

•	 Exterior walls are susceptible to wildfire

flames, conductive heat, and radiant heat.

Flames and heat can ignite combustible wall

coverings. When exterior walls ignite, the

fire can spread to other components of the

building such as the roof, soffit, windows, and

doors, resulting in substantial damage to or

total loss of the building.

•	 Windborne embers and firebrands are also

sources of ignition. Embers can become

trapped in cracks in walls, window openings,

and door trim boards and ignite combustible

materials. Windborne firebrands can ignite

wall coverings.

•	 The fire resistance of exterior walls depends

primarily on what the walls are constructed of and the amount of nearby combustible material.

Some types of construction materials such as vinyl siding do not burn but can melt when

exposed to high temperatures (see Figure 1), allowing the fire to reach the underlying wall

components and penetrate the interior of the building.

Guidance for New Buildings

•	 For the best protection, ensure that exterior wall coverings are noncombustible or fire-resistant

and not susceptible to melting. Concrete, fiber-cement panels or siding, exterior fire-retardanttreated wood siding or panels, stucco, masonry, and metal are recommended materials. With

these coverings, the covering itself should not ignite and fuel the fire. Examples of the types

of coverings that are not recommended are wood siding that is not fire-retardant-treated, vinyl

siding, metal siding susceptible to warping, and an exterior insulation finish system.

•	 Ensure that the entire wall assembly has a fire-resistance rating tested in accordance with

American Society for Testing and Materials (ASTM) E119. Although the above recommended

types of coverings provide an initial barrier to flames, heat may pass through the covering

Figure 1. Vinyl siding that melted and warped

during a wildfire (firecenter.berkeley.edu).
Page 2 of 3	 09/08 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 7 – Exterior Walls

and ignite underlying wall components. A fire-resistance rating indicates how long under test

conditions a wall assembly can prevent flames and heat from passing through the wall. A

minimum fire-resistance rating of 1 hour is recommended, but higher ratings provide greater

protection.

•	 Comply with the requirements of the fire-rated assembly, including using the exact type of

materials, configuration, and attachment used during the testing that established the rating.

•	 For exceptional fire resistance, use insulated concrete form (ICF) walls, cast-in-place concrete,

or fully grouted concrete masonry units. If ICF is selected, use a stucco or masonry wall

covering to protect the plastic foam forms.

•	 If fiber-cement or metal wall coverings are

used, install one layer of 5/8-inch type X

exterior gypsum board with taped joints

underneath housewrap (see Figure 2).

For fiber-cement siding, the gypsum board

provides secondary protection if the siding

decomposes and falls away during a fire. For

metal panels, the gypsum board minimizes

the transfer of heat radiated from the metal

panels to other wall components.

•	 For vinyl siding (note that vinyl siding is not

recommended), install one layer of 5/8-inch

type X exterior gypsum board with taped

joints underneath housewrap. If the vinyl and

housewrap melt during a fire, the underlying gypsum board will provide some protection.

•	 Use noncombustible or fire-resistant material such as exterior fire-retardant-treated wood or

fiber-cement for trim boards around doors, windows, eaves, and corners.

Guidance for Existing Buildings

•	 Replace exterior wall coverings that are combustible, are susceptible to melting, or can readily

transmit heat with one of the recommended coverings listed above. Examples of the types

of coverings that need to be replaced are wood siding that is not fire-retardant-treated, vinyl

siding, metal siding, and an exterior insulation finish system.

– Before replacing vinyl or metal siding, check whether there is an underlying gypsum board

substrate. If so, remedial work may not be needed.

– Determine whether keeping the existing covering and covering it with 5/8-inch type X

gypsum board and a new covering is a viable option.

Considerations

•	 For stud walls, metal studs can be used in lieu of wood studs. Metal studs do not ignite, but

they transfer heat more readily than wood studs and can deform and collapse at temperatures

that can occur in a wildfire. Current data are insufficient regarding the wildfire performance of

Figure 2. Example of a fire-rated wall assembly.

Exterior covering

Wall stud

Sill plate

5/8-inch type X 

exterior gypsum board

Wood sheathing

Housewrap
FS No. 7 – Exterior Walls Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 3 of 3

walls that have wood studs versus metal studs.

•	 Maintaining and removing combustible debris (such as vegetation and leaves) and firewood

near the exterior walls regularly reduce a building’s vulnerability to ignition during a wildfire

(see Fact Sheet #4, Defensible Space).

Effectiveness

A wall assembly with one of the recommended coverings and a minimum 1-hour fire-resistance

rating is effective in all Fire Severity Zones.

Resources

ASTM E119 -08a Standard Test Methods for Fire Tests of Building Construction and Materials.

http://www.astm.org/Standards/E119.htm.

Materials and Construction Methods for Exterior Wildfire Exposure: Exterior Wall Siding and

Sheathing SFM Standard 12-7A-1, 2001 California Referenced Standard Codes (Part 12, Title

24, C.C.R.). http://www.fire.ca.gov/fire_prevention/downloads/%20Part_12_CA_SFM_12-

7A-1_Test_Standards.pdf.

FS No. 8 – Vents Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 1 of 5

Vents

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 8 

Purpose 

To provide information about ways to avoid windborne embers, convective heat, and radiant heat

entering exterior vent openings, which can lead to the ignition of interior building components and

contents. Guidance pertains to both new and existing buildings.

Vent Systems and Vent Openings

Vents can be divided into those for attics; ventilated cathedral ceilings; crawlspaces; and heating,

ventilation, and air conditioning (HVAC) systems.

Attic and Cathedral Ceiling Vents 

•	 Ridge vent — a continuous vent installed along the full length of the roof ridge. Ridge vents

allow exfiltration of attic air, or in ventilated cathedral ceilings or ventilated nailbase boards, the

exfiltration of air from the ventilation cavity of the cathedral ceiling or nailbase boards. Ridge

vents are metal or plastic. Some ridge vents have internal baffle media to avoid the entrance of

wind-driven rain and snow.

•	 Soffit vent — a continuous or intermittent vent installed along a soffit. Soffit vents provide air

intake into the attic or into the ventilation cavity of cathedral ceilings and ventilated nailbase

boards. Soffit vents are metal or plastic and

often have a screen to prevent insect entry.

Vinyl and metal soffits are commonly vented by

intermittently spaced, perforated soffit panels.

•	 Gable-end vent — a vent located in the gableend wall, just below the roof ridge. Gable-end

vents allow air to flow into and out of attics.

Gable-end vents normally have louver blades

to avoid the entrance of wind-driven rain

and snow (see Figure 1). This type of vent is

commonly metal and normally has an insect

screen.

•	 Through-roof vent — a vent that penetrates the

roof to allow exfiltration of attic air; also known

as an eyebrow or dormer vent. Through-roof

vents, including sheet metal “goose-necks,” are also available for kitchen or bathroom exhaust

ducts. Through-roof vents are metal, plastic, or rigid fiberglass.

Figure 1. A louvered vent opening can be used for

gable-end venting or for connection to ductwork.

Horizontal louvers can 

prevent embers from 

entering the ventilation 

system
Page 2 of 5	 09/08 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 8 – Vents

Crawlspace Vents

•	 Crawlspace vent — a vent installed intermittently through the foundation wall several inches

above-grade. Crawlspace vents allow air to flow into and out of the crawlspace.

HVAC System Vents

•	 Through-roof vent (see above).

•	 Wall louvers — a vent opening on an exterior wall (see Figure 1). Wall louvers are connected to

the HVAC ductwork where air enters or is exhausted from the building. Louvers are commonly

metal. The louver blades are normally in a fixed position (i.e., cannot be rotated), but some

have moveable blades that can be rotated to close the vent opening.

Key Issues

•	 Embers and hot gases can be blown or pulled

into vent openings and enter attic spaces,

crawlspaces, and ductwork, leading to ignition of

the interior of the building (see Figure 2).

•	 Debris can accumulate at vent openings and

ignite during a wildfire.

Guidance for New Buildings

All Vents 

•	 Specify and install noncombustible material for all vents. Metal products are recommended for

vents and vent flashing.

•	 Specify and install corrosive-resistant, metal mesh screens with a maximum opening of

1/4 inch at all vent openings.

•	 Specify and install vent openings with a maximum net free area of 144 square inches.

•	 Place all vent openings at least 10 feet from other buildings or property lines to avoid ignition

from embers and hot gases from an adjacent building that has ignited.

Attics (including Cathedral Ceiling and Ventilated Nailbase Boards) 

Protecting attic spaces from wildfires is a challenge because air is naturally drawn into attics

through vent openings. Although insect screens can prevent the entry of many embers, vent

screens and louvers do not prevent the entry of hot gases. Vents that allow air to flow into and out

under normal conditions and also avoid the entry of embers and hot gases in a wildfire can be

provided in the following ways:

•	 Gable-end vent. Instead of using ridge vents, specify and install gable-end vents with specially

designed metal shutters. When a wildfire threatens, the shutters can be placed over the gableend vent. A hinged shutter that can be latched in an open or closed position is recommended

(see Figure 3). A detachable shutter design can be used, but when the shutters are needed,

Figure 2. Embers or hot gases can be blown or

pulled into vents.
FS No. 8 – Vents Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 3 of 5

the homeowner must remember quickly

where they are stored. Shutters should have

a gasket that provides a tight seal between

the shutter and gable-end vent. For a more

conservative shutter, a shutter with an

insulated core encapsulated by metal (similar

to a refrigerator door) can be used.

When gable-end vents are combined with

soffit vents, effective attic ventilation can

be achieved when the attic space is simple

and relatively small, such as a small, gableroofed house. If the house has a complex roof

area or the attic is too large to be effectively

ventilated by gable-end vents, ridge vents or

through-roof vents should be used.

•	 Ridge vent. Continuous ridge vents can

provide effective ventilation, but typical ridge

vents are not highly fire-resistant. Although air is normally exhausted through ridge vents,

hot gases can enter the ridge vent and flow into the attic. Embers can also enter through the

ridge vent if the vent does not have internal baffle media. Typical ridge vents are therefore not

recommended unless the attic configuration or size requires ridge vents to ventilate the attic

effectively. If ridge vents are used, metal vents with internal baffle media are recommended,

but during a wildfire, the internal baffle

material may melt and become ineffective in 

at preventing embers from entering.

•	 Soffit vent. As with ridge vents, typical

soffit vents are not highly fire-resistant, but

because they are a necessary element of a

vented attic, they cannot be eliminated. To

avoid embers and hot gases from entering

the vents, specially designed metal shutters

over the soffit vent openings should be

specified and installed. See the shutter

recommendations for gable-end vents above.

•	 Through-roof vent. Through-roof vents are not

recommended for attic ventilation because

there is no known effective strategy for

avoiding embers and hot gases from entering,

other than blocking the vent. A 1/4--inch

screen is effective at keeping out firebrands

and embers that are larger than 1/4-inch but

will not keep out smaller embers or hot air.

Shutter with

fire-resistant gasket

Shutter latched in

open position

Wall louver vent

Shutter manually latched

in closed position at the

onset of a wildfire

The Unventilated Attic

The most conservative approach to

preventing embers and hot gases from

entering the attic is to eliminate attic

ventilation, but unventilated attics are

controversial. Although allowed by the

International Residential Code, provided

the Code’s criteria are met, unventilated

attics may not comply with local building

codes.

However, when unventilated attics are

allowed by the building code or code

compliance is not an issue, and when

climatic and interior humidity conditions

(e.g., no indoor swimming pools) are

conducive to an unventilated design,

an unventilated attic is a reliable way

to prevent embers and hot gases from

entering the attic.

Figure 3. A hinged shutter.
Page 4 of 5	 09/08 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 8 – Vents

Because of variable reliability of blocking techniques and the potential danger of homeowners

falling from roofs while attempting to block vents, blocking is not recommended.

Crawlspace Vents 

Specify and install specially designed metal shutters over crawlspace vent openings. A 1/4‐inch

mesh screen should also be installed over the vent opening. See the shutter recommendations

for gable-end vents above.

HVAC System Vents

•	 Wall louvers. Specify and install specially designed metal shutters over wall louvers (see the

shutter recommendations for gable-end vents above) or specify and install wall louvers that

have adjustable tight-fitting blades that can be closed when a wildfire threatens.

As an additional conservative measure with either shutters or adjustable blades, specify and

install fire dampers within the ducts immediately behind the wall louvers. If sufficiently high

heat penetrates beyond the louver, the fire damper will automatically close and prevent high

heat from penetrating farther.

•	 Through-roof vents. As discussed in attic ventilation, through-roof vents are not recommended.

Rather than running ductwork through the roof, extend the ductwork to an exterior wall where

it can be fitted with a wall louver and shutter. If it is necessary to penetrate the roof, however,

install a fire damper in the duct at the plane of the roof assembly.

Guidance for Existing Buildings 

•	 If the home has ridge vents or wall louvers and they are not metal, replace them with metal

vents according to the guidance provided above.

•	 If existing vent openings do not have screens or if the screen openings are larger than

1/4‐inch, install metal screens according to the guidance provided above.

•	 Install shutters over gable-end vents, soffit vents, crawlspace vents, and wall louvers. If the

existing wall or soffit is combustible, shutters may not be effective. In this case, installing

shutters is probably cost-effective only if done in conjunction with upgrades to the wall or soffit.

Considerations

•	 Low-profile, through-roof vents have been used in place of soffit/eave vents with great success,

but none of these products have been tested at the time of this publication.

•	 The homeowner should periodically have a professional remove debris that has accumulated

near or on vent openings, vent screens, and louver blades.

•	 The amount of vegetation near vent openings should be limited (see Fact Sheet #4, Defensible

Space).

•	 To minimize the possibility that embers and hot gas will be pulled into the home, the HVAC

system, including exhaust fans, should be turned off when a wildfire threatens. Attic exhaust
FS No. 8 – Vents Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 5 of 5

fans should also be shut down. Attic exhaust fans that are controlled by a thermostat may need

to be deactivated by tripping the circuit breaker.

•	 For soffit construction, see Fact Sheet #6, Eaves, Overhangs, and Soffits.

Effectiveness

All mitigation measures listed in this Fact Sheet are effective in all Fire Severity Zones except as

noted below.

•	 If a ridge vent is installed, the vent opening may be breached during extreme fire exposure by

embers or hot gases, which could result in ignition of the attic.

•	 The effectiveness of shutter-protected vent openings is dependent on the deployment of the

shutters by the homeowner prior to fire exposure.

Resources

Slack, P. 2000. Firewise Construction Design and Materials. Colorado State Forest Service.

Under Eave SFM Standard 12-7A-3, 2001 California Referenced Standard Codes (Part 12, Title

24, C.C.R.). Available at www.fire.ca.gov/fire_prevention/downloads /Part_12_CA_SFM_12-

7A-3_Test_Standards.pdf.

FS No. 9 – Gutters and Downspouts	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 2

Gutters and 

Downspouts

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 9 

Purpose

To provide guidance about installing fire-resistant gutters and downspouts to reduce the potential

for damage to homes and other buildings from wildfires. Guidance pertains to both new and

existing buildings.

Key Issues

•	Debris such as branches, leaves, and pine needles can

become trapped in gutters (see Figure 1). The debris

can be ignited by flying embers or firebrands during a

wildfire, and the fire can spread to the roof.

•	Gutters and downspouts are often constructed of

plastic. Plastic can melt when exposed to the high

temperatures that can occur during a wildfire.

Guidance

•	Install noncombustible leaf guards over gutters to

prevent the accumulation of combustible debris. Types

of leaf guards include metal-mesh screens and metal

hoods that fit into the gutter (see Figure 2).

•	Use gutters and downspouts constructed of

noncombustible materials such as galvanized steel,

copper, and aluminum. Metal hood leaf guards are

recommended because they do not melt and are

relatively effective in keeping debris out of gutters (see

Figure 2).

Considerations

•	Intense heat from a wildfire can distort noncombustible

gutters, leaf guards, and downspouts, and they may need

to be replaced after a wildfire.

•	Some leaf guards can become dislodged over time, reducing their effectiveness.

Figure 2. Leaf guards allow rainwater

into the gutter but keep combustible

debris out.

Leaf guard 

Figure 1. Debris in gutters can ignite

and lead to ignition of the roof or fascia

board.
Page 2 of 2	 09/08	 Home Builder’s Guide to Construction in Wildfire Zones FS No. 9 – Gutters and Downspouts

•	Some types of leaf guards do not prevent all types of debris from accumulating in the gutter.

For example, mesh-type leaf guards allow pine needles to accumulate. Leaf guards and gutters

should therefore be checked regularly and debris removed if necessary.

Effectiveness

Noncombustible gutters, leaf guards, and downspouts are effective in all Fire Severity Zones.
FS No. 10 – Windows and Skylights	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 4

Windows and 

Skylights

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 10

Purpose

To provide information about measures that can be taken to avoid the ignition of interior building

components and contents due to the intrusion of windborne embers, hot gases, and radiant heat

through windows, sliding glass doors, door vision panels, and skylights. Guidance pertains to both

new and existing buildings.

Key Issues

•	 Glazing in homes is typically vulnerable to wildfire

(see Figure 1). (“Glazing” refers to the glass,

plastic, or fiberglass-reinforced translucent

material in windows, sliding glass doors, door

vision panels, and skylights.) Failed glazing allows

easy passage of embers, hot gases, and radiant

heat into the interior of the building. Glazing is

vulnerable to wildfire in two ways:

– Flame impingement and radiant heat can be

severe enough to melt or break many types

of glazing. A single pane of typical residential

glass can fail within 5 minutes of exposure to a

wildfire (Slack, 2000).

– Windborne firebrands can have sufficient

momentum to break many types of glazing.

•	 The frames for windows, sliding glass doors, and

skylights are constructed of metal, plastic, wood,

or a combination of these materials. Plastic and

wooden frames are susceptible to failure from

burning or melting (see Figure 2). If the frame or

sash fails, the entire glazing may fall out.

Guidance on New Buildings

This section provides guidance on glazing, frames,

fire‐rated assemblies, and exterior window shutters.

Figure 1. Potential damage to a window

during a wildfire.

Embers melt vinyl frames 

and ignite wooden frames

Radiant heat and windborne 

firebrands can shatter windows 

and lead to interior damage

Figure 2. Combustible framing (firecenter.

berkeley.edu).
Page 2 of 4	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 10 – Windows and Skylights

Glazing 

A variety of products are available for glazing in windows, sliding glass doors, door vision panels,

and skylights. Glazing can be in a single- or multi-paned configuration. The recommended glazing

products for homes in wildfire zones are laminated glass, tempered glass, glass with a lowemissivity, fiberglass-reinforced translucent glazing, and insulated glazing units (IGUs). Glazing

products that are not recommended are annealed glass, ceramic glass, and plastic glazing.

Recommended

• Laminated glass. Laminated glass provides resistance to windborne firebrands. If a

firebrand strikes with enough momentum to break the glass, the plastic film in the core of

the glass will keep the glazing in the frame, allowing the broken glass to continue to resist

firebrand impacts, embers, and hot gases. If the plastic film in the core gets sufficiently hot,

the pane will delaminate whether or not the glass has been broken. If laminated glass is

specified, it should either be protected by shutters, as discussed below, or combined with

tempered glass in an IGU. See the information on IGUs below.

• Tempered glass. Tempered glass is more resistant to heat and flames than laminated

glass or annealed glass (see below). The resistance of tempered glass can be enhanced

with a low-e coating or a proprietary reflective coating, as discussed below. Firebrands

with sufficient momentum can break tempered glass. To avoid breakage, the glass can be

protected by shutters, as discussed below. Another alternative is to specify and install an

IGU with a laminated glass inner pane.

• Low-emissivity (low-e) coating. Glass with a low-e coating provides a higher level of

resistance to radiant heat than other types of glazing because the coating reflects radiant

heat, reducing the probability that the heat will be able to enter the building. The coating

should be on the inner surface of the exterior pane.

•	 Proprietary fiberglass-reinforced translucent glazing. This product is available for skylights

and walls. The skylight material has a Class A rating. See Fact Sheet #5, Roofs, for a

discussion of this type of rating.

• Insulated glazing unit. An IGU consists of two

or three panes of glass that are separated by a

sealed air space. Double-paned annealed units

last about 10 minutes in a wildfire, twice as

long as single-paned windows. In many cases,

10 minutes is long enough to provide protection

from the fire. If the first pane fails, the second

pane must still be penetrated (Slack, 2000)

(see Figure 3). Laminated glass, tempered

glass, and glass with a low-e coating can be

combined in various ways into an IGU.

Two panes of glass with 

a layer of air between

The first pane may shatter 

within 5 minutes of the

onset of a wildfire

The second pane offers 

5 minutes of additional 

protection

Figure 3. Double-paned glazing.
FS No. 10 – Windows and Skylights	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 3 of 4

Not Recommended

• Annealed glass. Annealed glass (also known as common float glass) is commonly used in

residential windows. Annealed glass is the most susceptible to wildfires of the various glass

types and is not recommended for homes in wildfire zones unless protected by shutters, as

discussed below.

• Ceramic glass. This specialty glass is effective at resisting flames, but it transmits radiant

heat readily. If ceramic glass is used for exterior glazing, heat that is high enough to

cause ignition can be transmitted into the interior of the building. Ceramic glass is not

recommended for homes in wildfire zones.

• Plastic glazing. Acrylic and polycarbonate are often used in skylights and sometimes in

windows. Because plastic glazing can melt during a wildfire, it is not recommended for

homes in wildfire zones.

Frames

A variety of products are available for window and skylight frames. To avoid window failure, frames

should be constructed only of metal or metal-clad wood. Wooden and plastic frames should not

be used.

Fire-rated Assemblies

If a fire-rated wall is specified, windows and sliding glass doors that are commensurate with the

wall in terms of the fire rating are recommended. For example, a window with a 11⁄2-hour rating is

intended to be used in a wall with a 2-hour rating, and a door with a 3/4-hour rating is intended

to be used in a wall with a 1-hour rating. However, a window with a higher fire rating may be used.

See Fact Sheet #7, Exterior Walls, for information about fire-rated walls.

If a fire-rated wall is not specified, an IGU with a metal or metal-clad wooden frame should be

used. See the information on IGUs above.

Exterior Window Shutters

Exterior window shutters can provide protection for

windows and sliding glass doors in a wildfire. Solid

metal shutters are unlikely to ignite or melt and are

therefore recommended over wooden or plastic shutters

(see Figure 4). For enhanced protection, an insulated

metal shutter can be designed and fabricated. If the

building is located in a windborne debris region within

a hurricane-prone region, the shutter should meet the

windborne debris criteria in the American Society of

Civil Engineers standard, ASCE 7-05 (2006). Figure 4. This metal shutter has top

and bottom tracks that are permanently

anchored to the wall (FEMA 577).
Page 4 of 4	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 10 – Windows and Skylights

Guidance on Existing Buildings

•	 Windows and sliding glass doors, including frames, that are susceptible to damage from

a wildfire should be replaced with the components that are recommended above and/or

protected by shutters, as recommended above.

•	 Door vision panels that are susceptible to damage from a wildfire should be replaced with

tempered glass with a low-e or proprietary reflective coating, provided the door has sufficient

fire resistance (see Fact Sheet #11, Exterior Doors).

•	 Skylights with plastic glazing should be replaced with one of the recommended types of

glazing, as described above.

Considerations

•	 Shutters protect the home not only from wildfires but also from extreme weather.

•	 Double-paned glass is more energy efficient than single-paned glass.

•	 A proprietary reflective coating is available for application to tempered glass. The coating acts

like a low-e coating in that it reflects radiant heat, but the proprietary reflective coating may be

more effective. For more information on this product and a comparison of fire ratings of various

types of glass products and sizes, see www.safti.com.

Effectiveness

•	 Window assemblies with 3/4-hour minimum ratings are effective in all Fire Severity Zones.

•	 Metal cladding on metal clad-wood frames may become distorted during wildfire exposure and

require replacement.

•	 Temporary shutters are effective only if the homeowner has sufficient time to put the shutters

into place.

Resources

American Society of Civil Engineers. (2006). Minimum Design Loads for Buildings and Other 

Structures. ASCE 7-05.

Center for Fire Research and Outreach. University of California, Berkeley: College of Natural

Resources. http://firecenter.berkeley.edu/default.htm.

Exterior Windows SFM Standard 12-7A-2, 2001 California Referenced Standard Codes (Part 12,

Title 24, C.C.R.). http://www.fire.ca.gov/fire_prevention/downloads/ Part_12_CA_SFM_12-

7A-2_Test_Standards.pdf.

FEMA. 2007. Design Guide for Improving Hospital Safety in Earthquakes, Floods, and High Winds: 

Providing Protection to People and Buildings. Risk Management Series, FEMA 577.

http://www.fema.gov/library/viewRecord.do?id=2739.

Fire Rated Glazing Solution. www.safti.com.

Slack, P. 2000. Firewise Construction Design and Materials. Colorado State Forest Service.
FS No. 11 – Exterior Doors Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 3

Exterior Doors

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 11

Purpose

To provide basic guidance on the design and construction of exterior doors, including garage

doors, on buildings in wildfire zones. Guidance pertains to both new and existing buildings.

Key Issues

•	 Exterior doors are subject to the same

types of exposure as exterior walls in a

wildfire (see Figure 1). However, exterior

doors are typically much thinner and less

fire-resistant than exterior walls and can

therefore burn through much faster.

•	 Flames and hot gases can ignite

combustible materials in a door and door

frame.

•	 Flames and hot gases can penetrate

openings between the door and frame and

between the door and threshold (or floor if

no threshold exists).

•	 Embers can become lodged in openings

between the door and frame and between

the door and threshold (or floor if no

threshold exists). Embers can also be

blown through the openings into the

interior of the building.

•	 Flames, convective or radiant heat, and

airborne firebrands can break glass in a

door.

Exterior Door Characteristics 

and Ratings

Types of exterior doors include solid entrance doors, entrance doors with glass vision panels,

sliding glass doors, storm doors, screen doors, garage doors, and cellar doors.

Solid exterior doors are typically made of wood or metal. Doors with a solid, noncombustible

mineral core are classified as fire-rated doors and are rated by Underwriters Laboratories

(UL) according to the length of time they can resist fire (UL Standard 10C) (UL, 1998). UL

Figure 1. Types of exposure that exterior doors can be

subject to in a wildfire.

WelcomeWelcome

Embers can become lodged 

in openings and separations

Radiant heat can 

shatter glass

Radiant heat and embers can ignite combustible 

materials and penetrate through openings
Page 2 of 3	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 11 – Exterior Doors

classifications for interior and exterior fire-rated doors and their frames range from 3-hour to

20‐minute ratings. Exterior fire-rated doors are available with a rating of 11⁄2 hour or 3/4 hour.

The fire rating for doors is intended to equal three-fourths of the fire rating of the surrounding wall.

For example, a door with a 11⁄2‐hour rating is intended to be used in a wall with 2-hour rating, and

a door with a 3/4-hour rating is intended to be used in a wall with a 1-hour rating. However, a door

with a higher fire rating may be used.

Guidance for New Buildings

•	 If a fire-rated exterior wall is specified (see Fact Sheet #7, Exterior Walls), specify and install a

fire-rated door and frame. As explained above, the rating of the door and frame should be at

least three-fourths of the rating of the wall. In addition, specify and install fire-rated hardware.

•	 Follow the guidance pertaining to door glass vision panels and glass sliding doors in Fact

Sheet #10, Windows and Skylights.

•	 To avoid embers and hot gases penetrating the interior of the building between the door

and the door frame, install adjustable weatherstripping on the interior side of the door

frame and specify and install an automatic door bottom or threshold weatherstripping. The

weatherstripping and door bottom should be tested in accordance with UL Standard 10C.

Weatherstripping is relatively inexpensive (see Figure 2).

•	 Garage doors are typically made of wood, aluminum, or steel

and are insulated or non-insulated. Unlike standard egress/

ingress doors, garage doors are not normally tested for fire

resistance (see Figure 3). To protect the garage door and

entire building, follow the guidance listed below.

– Specify and install insulated, metal garage doors.

– To avoid embers and hot gases penetrating the garage,

specify and install weatherstripping that has been tested

in accordance with UL Standard 10C around the entire

garage door.

Figure 2. Example of adjustable

weatherstripping (FEMA 577).

Fire-resistant 

weatherstripping

Noncombustible or 

fire-resistant trim

Insulated metal door

Figure 3. A garage door with

noncombustible and fire-resistant

components.

Door

Adjustable

jamb

weatherstrip
FS No. 11 – Exterior Doors Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 3 of 3

•	 For exterior trim that covers the opening between the door frame and exterior wall, specify and

install noncombustible or fire-resistant material such as fire-retardant-treated wood or fibercement board.

Guidance for Existing Buildings

•	 Add weatherstripping to doors, as described above.

•	 Replace vision panels in doors, if necessary, as described in Fact Sheet #10, Windows and

Skylights.

•	 Replace sliding glass doors and/or protect with shutters, as described in Fact Sheet #10,

Windows and Skylights.

•	 Replace wooden garage doors, particularly if they do not have a solid core.

•	 Replace wooden egress/ingress doors without a solid core, although egress/ingress doors are

often relatively fire-resistant compared to other components of the building and therefore not

normally a high priority for remediation.

Considerations

Metal and metal-clad door frames can transmit heat during a fire, and the heat can ignite the

surrounding exterior wall if the wall is not constructed to fire-resistant standards, as noted above.

For more information, see Fact Sheet #7, Exterior Walls.

Effectiveness

All mitigation measures listed in this Fact Sheet are effective in all Fire Severity Zones except as

follows:

•	 Garage doors are not normally tested for fire resistance and may not provide effective fire

resistance in high Fire Severity Zones.

•	 Under very high heat or prolonged exposure to heat, weatherstripping material can melt or

burn, lowering its effectiveness in preventing embers and hot gases from entering the interior

of a building.

Resources

FEMA. 2007. Design Guide for Improving Hospital Safety in Earthquakes, Floods, and High Winds: 

Providing Protection to People and Buildings. Risk Management Series, FEMA 577. http://

www.fema.gov/library/viewRecord.do?id=2739.

Steel Door Institute (SDI). 2001. Basic Fire Door Requirements. Technical Data Series SDI

118‐01. http://www.steeldoor.org/res/118.pdf).

Underwriters Laboratory (UL). 1998. UL Standard 10C, Positive Pressure Fire Tests of Door

Assemblies.

FS No. 12 – Foundations Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 4

Foundations

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 12 

Purpose

To provide guidance on avoiding the ignition of foundations by windborne embers and convective

and radiant heat in wildfire zones. Guidance pertains to both new and existing buildings.

Foundation Designs

Foundations can be open or closed. Homes normally have only one type of foundation, but some

have both.

Closed Foundation

In a closed foundation, the foundation wall

extends from the footing to the first floor around

the perimeter of the building. The foundation

wall is typically a bearing wall. The below-grade

portion is typically constructed of concrete or

masonry, but preservative-treated wood can also

be used. The above-grade portion may also be

constructed of concrete or masonry, or it may be

a stud wall (commonly referred to as a “cripple

wall”; see Figure 1). The foundation wall encloses

a basement, a crawlspace, or the soil below a slabon-grade.

Open Foundation

In an open foundation, the building is supported

by piles or piers, and the bottom of the first-floor

framing is several feet above-grade (see Figure 2).

Piles and piers are constructed of concrete,

masonry, timber, or steel. Some of the area below

the first floor may be enclosed with walls for an

elevator or to create a small storage area.1 Wood 

lattice is also often placed between piles/piers to

provide a privacy screen (for example, around cars

parked under the building). Manufactured housing

1	If the home is in Flood Hazard Zone V, see Technical Fact Sheet 27, Enclosures and Breakaway Walls, in Home Builder’s 

Guide to Coastal Construction, Technical Fact Sheet Series (FEMA 499). www.fema.gov/rebuild/mat/ mat_fema499.

shtm.

Figure 1. A closed foundation with a cripple

wall (FEMA field team).

Figure 2. An open foundation.
Page 2 of 4	 09/08 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 12 – Foundations

is typically supported on an open foundation, but often a non-bearing wall (skirting) is installed

around the perimeter of the home between grade and the floor.

Key Issues

Closed Foundation 

•	 Direct flame, embers, or hot gases can enter through crawlspace vents or breached basement

windows.

•	 The crawlspace wall or wall covering or the exposed portion of the basement wall or wall

covering can be ignited by direct flame, embers, or hot gases. Once the wall is ignited, the fire

can penetrate the crawlspace or basement and climb up the exterior wall.

•	 Combustible items stored in basements or crawlspaces (such as household goods in cardboard

boxes) can become fuel in a fire.

Open Foundation 

•	 The underside of the first floor can be ignited by direct flame, embers, or hot gases. When piles

or piers are constructed of timber, the pile/pier is normally thick enough to resist ignition. See

Fact Sheet #13, Decks and Other Attached Structures, for information on ignition resistance as

a function of timber width.

•	 Wood lattice screens can be ignited by direct flame, embers, or hot gases. Lattice screens

often trap combustible debris such as leaves and paper, increasing the potential for ignition.

Ignition of a lattice screen can lead to ignition of the underside of the first floor.

•	 Walls and wall coverings around enclosures such as elevator shafts and storage areas can be

ignited by embers or hot gases, leading to ignition of the underside of the first floor.

•	 Combustible debris or storage items (such as firewood or gas in a container) in an open

foundation can be ignited, leading to ignition of the underside of the first floor.

•	 Skirting around the perimeter of manufactured homes can be ignited, leading to ignition of the

underside of the floor and spread of a fire up the exterior wall.

Guidance for New Buildings

Closed Foundation

•	 See Fact Sheet #7, Exterior Walls, for guidance on walls and wall coverings.

•	 See Fact Sheet #8, Vents, for guidance on crawlspace vents.

•	 See Fact Sheet #10, Windows and Skylights, for guidance on windows.

Open Foundation

To avoid ignition of the first-floor framing members (joists) and floor decking, sheath the underside

of the framing as follows:
FS No. 12 – Foundations Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 3 of 4

•	 Attach 5/8-inch thick exterior type X

gypsum board to the underside of the

joists. For energy conservation, install

batt insulation between the joists (see

Figure 3).

•	 Attach fire-retardant-treated plywood,

fiber-cement panels, or metal siding

panels over the gypsum board.

•	 Do not install lattice screens. If screens

are installed, use chain-link fencing with

metal privacy slats instead of wood.

•	 For guidance on enclosure walls

around storage areas and for skirting

on manufactured homes, see Fact

Sheet #7, Exterior Walls. For guidance

on windows, see Fact Sheet #10, Windows and Skylights. For guidance on doors, see Fact

Sheet #11, Exterior Doors.

Guidance for Existing Buildings

Closed Foundation

•	 See Fact Sheet #7, Exterior Walls, for guidance on walls and wall coverings.

•	 See Fact Sheet #8, Vents, for guidance on crawlspace vents.

•	 See Fact Sheet #10, Windows and Skylights, for guidance on windows.

Open Foundation

•	 If the first-floor framing members are timber members less than 3 inches thick (nominal) or if

the floor decking is combustible, sheath the underside of the framing as described above.

•	 Evaluate floor beams and joists that are constructed of steel (not common in residential

construction). Depending on a variety of conditions, it may be prudent to sheath the underside

of the framing as described above or protect the steel with suitable fireproofing.

•	 Remove existing lattice screens or replace them with chain-link fencing with metal privacy slats.

•	 For guidance on enclosure walls around storage areas and for skirting on manufactured

homes, see Fact Sheet #7, Exterior Walls. For guidance on windows, see Fact Sheet #10,

Windows and Skylights. For guidance on doors, see Fact Sheet #11, Exterior Doors.

Considerations

•	 The homeowner should periodically remove combustible debris under buildings with open

foundations.

Figure 3. A 5/8-inch type X gypsum board attached to

the underside of the joists.

5/8-inch 

type X gypsum

Joist

Subfloor

Exterior

cladding

Batt 

insulation
Page 4 of 4	 09/08 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 12 – Foundations

•	 The homeowner should not store combustible items such as gas and firewood under buildings

with open foundations.

•	 If a building is exposed to a wildfire, an engineer should evaluate the structural integrity of the

foundation.

•	 In areas where dry rot is a concern, fire-retardant-treated plywood can be attached over the

gypsum board on the underside of the floor joists, but plywood is affected more by weather

elements than fiber-cement panels or metal siding panels.

•	 If the building is located in a floodplain, as designated by FEMA’s National Flood Insurance

Program, criteria set forth in Title 44 Code of Federal Regulations Part 60 should be

considered.

Effectiveness

All measures listed in this Fact Sheet are effective in all Fire Severity Zones.

Resources

FEMA. 2005. Home Builder’s Guide to Coastal Construction Technical Fact Sheet Series.

FEMA 499. http://www.fema.gov/rebuild/mat/mat_fema499.shtm.

FEMA. 2006. Recommended Residential Construction for the Gulf Coast: Building on Strong and 

Safe Foundations. FEMA 550. www.fema.gov/library/viewRecord.do?id=1853.

Slack, P. 2000. Firewise Construction Design and Materials. Colorado State Forest Service.
FS No. 13 – Decks and Other Attached Structures	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08	 Page 1 of 4

Decks and Other 

Attached Structures

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 13 

Purpose

To provide guidance on the construction of decks and other attached structures on homes in

wildfire zones. Other attached structures include balconies, porches, stairs, and ramps. All of

these structures can be a source of fuel during a wildfire. Ignition by flames or firebrands can lead

to ignition of the exterior of the building, resulting in substantial damage to or total loss of the

building.

Key Issues

•	 Decks are often built at the top of a slope in the direct line of the most likely approach of a

wildfire, putting these decks at a high risk of ignition. Building and deck orientation is therefore

important in reducing the risk of exposure to a wildfire (see Fact Sheet #3, Selecting the

Construction Site).

•	 Decks constructed of dimensioned lumber are combustible and subject to quick ignition.

•	 Embers, firebrands, and hot gases can become lodged or trapped under decks and other

attached structures, where the structures attach to the building, and in the gaps between

board decking. They can also settle against exterior walls and accumulate at railing edges. All

of these things increase the risk of ignition of these structures and ignition of the home.

Guidance for New Decks and Other 

Attached Structures

Siting

Orient decks and other attached structures to avoid

exposure to the path of a wildfire. Avoid constructing

these structures near heavily vegetated areas and

topographic features such as steep slopes, gullies,

canyons, saddles, ridge tops, and narrow mountain passes

(see Fact Sheet #3, Selecting the Construction Site).

Construction Materials 

Use heavy timber or noncombustible materials (see

Figure 1). The following materials are recommended:

•	 For columns, use a minimum 6-inch × 6-inch timber or

concrete block or steel.

Figure 1. Deck constructed of heavy

timber.

Decking: 3-inch 

nominal thickness

Columns: 

6-inch x 6-inch

Joists: 

3- or 4-inch 

nominal thickness

Railing: metal
Page 2 of 4	 09/08	 Home Builder’s Guide to Construction in Wildfire Zones	 FS 13 - Decks and Other Attached Structures

•	 For floor joists and beams, use heavy timber, 3-inch to 4-inch nominal thickness fire-retardanttreated wood, or concrete block or steel framing.

•	 For railings, use minimum 3-inch nominal thickness fire-retardant-treated wood or metal,

cables, or tempered glass.

•	 For decking and stair treads, use exterior fire-retardant-treated wood, minimum 3-inch nominal

thickness, or brick or concrete pavers and a suitable drainage mat over wood decking or metal

grates. Light, poured concrete may also be a suitable deck covering.

Due to insufficient data comparing the performance of plastic and composite materials to heavy

timber decking when exposed to flames and heat, FEMA does not recommend the use of plastic

or composite decking in high Fire Severity Zones. However, the University of California’s Center

for Fire Research and Outreach (Berkeley) has conducted some testing on plastic and composite

materials used in decks. Results are as follows:

•	 Plastic and composite products with channels on the underside of the decking degraded early

when exposed to under-deck fires.

•	 Products with hollow construction exhibited board collapse when exposed to firebrands.

•	 Some products with a solid construction performed similarly to 2-inch thick nominal wood

decking, but many did not perform as well as heavy timber decking.

More information on the testing is available at http://www.fire.ca.gov/fire_prevention/

downloads/Part_12_CA_SFM_12-7A-4_Test_Standards.pdf.

Construction Techniques

•	 Isolate the attached structure by surrounding it with

noncombustible material such as gravel, brick, or

concrete pavers to prevent vegetative growth and

reduce fuel in a wildfire (see Figure 2).

•	 Enclose the underside of the deck with fire-resistant

skirting that acts as a shield against embers and

reduces the probability that radiated and convected

heat will ignite the deck (see Figure 2).

•	 To prevent ember intrusion in gaps between the

decking and home (such as in offset ledger board

construction), cover the gaps with 1/8-inch metal

screening. Install flashing on ledger boards that are

attached without gaps to create a barrier to embers

and prevent water from penetrating (see Figure 3).

•	 Cover exposed floor framing at the underside of

attached structures with a fire-resistant soffit such as fiber-cement panels. The soffit should

have weep holes with a maximum diameter of 1/4 inch to allow water that leaks through the

decking to drain out of the soffit space.

Figure 2. Deck isolated by a patio.

Surround deck with 

noncombustible patio

Enclose the deck with 

fire-resistant skirting
FS No. 13 – Decks and Other Attached Structures	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08	 Page 3 of 4

Guidance for Existing Decks and Other Attached Structures

To enhance the performance of existing decks and other attached structures, the following are

recommended:

•	 Replace combustible materials with noncombustible or fire-resistant materials.

•	 Replace dimensional timber railings with railings constructed of fire-resistant materials such

as metal, tempered glass, cables, or 3-inch nominal thickness fire-retardant-treated wood

(see Figure 4).

•	 When the deck, balcony, stairs, or ramp can accommodate or be reinforced to accommodate

additional load, install brick or concrete pavers and a suitable drainage mat over the existing

decking (see Figure 4).

Figure 3. Deck flashing.

Figure 4. Concrete pavers

over existing deck.

Deck flashing

Deck joist

Exterior wall 

cladding

Exterior wall 

sheathing

Fiber-cement board

Flashing

Waterproof 

membrane

Concrete pavers

Existing deck

Existing joist

Gypsum soffit

Metal railing
Page 4 of 4	 09/08	 Home Builder’s Guide to Construction in Wildfire Zones	 FS 13 - Decks and Other Attached Structures

•	 Construct deck skirting around the deck using fire-resistant or noncombustible material such

as fiber-cement boards and/or construct a patio on the ground around the deck, stairs, or

ramp.

•	 Install a soffit at the underside of balconies, decks, stair landings, or ramps when skirting is not

installed (see Figure 4).

Considerations

•	 Maintenance and removal of combustible

debris and vegetation around and under

decks and other attached structures is a key

factor in reducing vulnerability to ignition

during a wildfire (see Figure 5). For more

information on defensible space, see Fact

Sheet #4, Defensible Space.

•	 Decks and other attached structures should

be maintained by replacing deteriorated

components before they lose their fireresistance.

•	 Decks enclosed with fire-resistant skirting

must be vented for moisture control (see

Fact Sheet #8, Vents).

Effectiveness

All mitigation measures listed in this Fact Sheet are effective in all Fire Severity Zones.

Resources

Decking: SFM Standard 12-7A-4. 2001 California Referenced Standard Codes (Part 12, Title 24,

C.C.R.). http://www.fire.ca.gov/fire_prevention/downloads/Part_12_CA_ SFM_12-7A-4_Test_

Standards.pdf.

University of California Agriculture and Natural Resources. Fire Performance Testing: Decks.

http://firecenter.berkeley.edu/quarles/deck_kit-SQ.pdf.

Figure 5. Combustible debris under this deck ignited

and led to the destruction of the deck. Although the

siding is noncombustible, the fire spread from the

deck through a window to the interior (firecenter.

berkeley.edu).
FS No. 14 – Landscape Fences and Walls	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 1 of 3

Landscape Fences

and Walls

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 14 

Purpose

To provide guidance about landscape fencing and walls that are attached to or near buildings in

wildfire zones to reduce the potential for damage to the buildings from a wildfire.

Key Issues 

•	 Landscape fences and walls function as

physical or visual barriers or architectural

statements. Property owners do not always

consider the potential that landscape fences

and walls can have in contributing to the

spread of a wildfire.

•	 The common wooden post-and-board fence

can become fuel for a wildfire, especially

when the fence is old and weather-beaten.

This type of fence can also collect embers

and firebrands in a wildfire and act as a

horizontal ladder fuel by allowing the fire

to travel along the fence toward the main

building (see Figure 1).

•	 Once ignited, a fence or wall constructed of

combustible materials that is attached to or near a building can ignite the building through

radiant or convective heat or by direct flame contact.

Guidance 

•	 Use noncombustible materials for fences and walls. Fences and walls vary in shape, size, and

construction materials, all of which provide varying degrees of protection or risk in a wildfire.

Typical materials used in fences and walls are wood, plastic, composite, metal, wire, concrete,

stone, and masonry. Of these materials, wood is the most combustible, while concrete, stone,

and masonry are noncombustible.

– Wood. Fences that are constructed of wood or have wooden components are combustible

and therefore provide no fire resistance. Combustible materials such as soft woods and

pine treated with preservatives should be avoided if the fence is attached to the building.

Dense hardwoods such as red oak, white oak, hickory/pecan, and walnut are more fireresistant than pines and other softwoods.

Figure 1. The gate that was attached to the garage

at the corner ignited and led the fire to the home,

causing the damage seen here (firecenter.berkeley.

edu).
Page 2 of 3	 09/08	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 14 – Landscape Fences and Walls

– Plastic. Plastic fences are more fireresistant, more durable, and often

stronger than wooden fences, but

plastic fences can melt in a wildfire from

temperatures that are below the maximum

a wildfire can generate (see Figure 2).

– Metal. Metal fences are more fire-resistant

than plastic fences. Wire fences such

as barbed wire, hog wire, and chain link

have little or no effect on fire passage.

However, if combustible materials have

accumulated in or around the fence or the

fence contains combustible materials such

as wooden posts, the fence can act as a

horizontal ladder fuel by allowing the fire

to travel along the fence toward the main

building

– Concrete, stone, or masonry. Concrete, stone, and masonry fences and walls are

noncombustible and can act as a barrier to a wildfire by deflecting flames away from a

building, but the passage of airborne embers and firebrands will not be significantly altered.

These materials are the most effective at minimizing the potential for damage to a building

from a wildfire.

•	 Avoid attaching fences and walls constructed of combustible materials to a building.

•	 For fences and walls that are attached to a building, ensure that all combustible components

are at least 10 feet from the building to prevent heat and flames from igniting the building.

•	 Avoid fences that have gaps, such as wooden slat fences, because airborne firebrands can

become trapped in the gaps and ignite the fence (see Figure 3).

Figure 2. Plastic fences can melt even under

moderate wildfire temperatures (FEMA field

team).

Figure 3. Key guidance

for fences.

Avoid fences with gaps because 

airborne firebrands can become 

trapped in the gaps and ignite 

the fence

Clear combustible debris and 

vegetation near the fence 

regularly; vegetation growing 

on or around a fence can ignite, 

leading to ignition of the fence 
FS No. 14 – Landscape Fences and Walls	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 	 Page 3 of 3

Considerations

•	 The physical condition of the fence or wall should be maintained.

•	 Combustible debris near the fence or wall should be cleared regularly (see Fact Sheet #4,

Defensible Space).

•	 The type of landscape vegetation that is planted next to a fence or wall should be considered,

and the vegetation should be maintained regularly. Unmanaged landscape vegetation can

increase the probability that the fence will ignite, especially a fence that is constructed of

combustible materials (see Figure 3). For more information on defensible space, see Fact

Sheet #4, Defensible Space.

Effectiveness

Masonry, concrete, stone, metal, and hardwood landscape fences and walls are effective in all

Fire Severity Zones.

Resources

American Hardwood Information Center. http://www.hardwoodinfo.com/species_ guide/

brochure_44-45.pdf

Center for Fire Research and Outreach. University of California, Berkeley: College of Natural

Resources. http://firecenter.berkeley.edu/default.htm.

Firesafe Council. http://www.firesafecouncil.org/.

Firewise Communities Program. http://www.firewise.org/.

FS No. 15 – Fire Sprinklers	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 1 of 4

Fire Sprinklers

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 15 

Purpose

To provide guidance on the installation of interior and exterior fire sprinkler systems on buildings

in wildfire zones. The guidance pertains to both new and existing buildings.

Key Issues

•	 During a wildfire, firebrands and airborne debris can breach windows, and convective heat and

embers can penetrate utility openings, gaps around doors, and other openings. The interior

of a building can ignite even when the exterior does not. Fire sprinklers are not common in

residential construction, but they can be effective in preventing damage from a wildfire.

•	 Exterior building components that are combustible such as overhangs and recessed alcoves

can trap embers, firebrands, and hot gases, leading to ignition of the building. Exterior

sprinklers can help extinguish flames before the building has been substantially damaged.

•	 A building that has ignited can endanger nearby buildings and contribute to the spread of a

wildfire. Interior and exterior sprinklers can prevent substantial damage to the building, protect

nearby buildings, and prevent the fire from igniting nearby combustible vegetation.

Interior Fire Sprinklers 

Common Misconception Fact

All sprinklers in a system activate

simultaneously.

Only sprinkler heads that are in an area of high heat are

activated. Typically, only one or two heads activate during a

fire. Sprinkler heads are activated only by heat, not by smoke.

Sprinklers can activate accidentally. According to the U.S. Fire Administration, only 1 in 16 million

sprinkler heads activates accidentally.

Water damage from sprinklers

is more expensive to repair than

damage from the fire.

Water damage from sprinklers is usually considerably less

expensive to repair than damage caused by water from fire

hoses, smoke, and fire. Quick-response sprinklers release

8 to 24 gallons of water per minute, while fire hoses release

50 to 125 gallons per minute.

Interior sprinkler systems are

obtrusive and not aesthetically

pleasing in residences.

Interior fire sprinklers for single-family residences are smaller

than traditional commercial or industrial fire sprinklers and

can be coordinated with any room décor. Sprinkler heads

come in a variety of styles, models, and colors and can be

mounted flush with the ceiling (see Figure 1) or concealed

behind covers.
Page 2 of 4	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 15 – Fire Sprinklers

Characteristics

•	 Interior fire sprinkler systems can detect a developing

fire quickly and activate automatically. Systems do not

require manual intervention.

•	 Interior sprinkler systems can include a warning system

that notifies occupants and emergency response

personnel of a developing fire.

•	 Interior sprinklers can be installed during new

construction or in an existing home.

Guidance

•	 Installing sprinklers in unoccupied, enclosed spaces

such as attics should be considered because doing so can provide additional protection if fire

penetrates the exterior of the space.

•	 Water pressure and supply must both be adequate for an interior sprinkler system to be

effective. Water is typically supplied by the water main from the municipal water supply. During

a wildfire, firefighting resources often exhaust the available water pressure. If existing water

pressure is inadequate or the source of water is a well, a holding tank can be used as a water

source. To ensure that water is available to the system during a wildfire, a pressurized holding

tank should be considered, even if the structure is connected to the municipal water supply.

Considerations

•	 The majority of the cost of an interior sprinkler system is associated with the piping material.

Options for materials include steel alloys, copper, and fire-resistant plastics. Plastic piping is

less expensive than steel alloys and copper, but its melting point is as much as five times lower

than copper piping.

•	 Hazard insurance rates are typically discounted for homes with interior sprinkler systems.

•	 An interior sprinkler system is relatively easy to install during new construction. The system

increases the total cost of construction by approximately 2 percent; complex and multi-story

installations may increase the cost more. Installing an interior sprinkler system can be done

when the roof is replaced or upgraded, and doing so may cost less than standard installation.

•	 The cost of installing an interior sprinkler system during new construction is about half the cost

of installing a system in an existing building.

Effectiveness

Internal sprinklers extinguish the fire at an early stage and prevent substantial damage from heat

and smoke or total loss of the structure. They are effective in all Fire Severity Zones.

Figure 1. A concealed, aesthetically

pleasing fire sprinkler.

Sprinkler head 

ceiling cover
FS No. 15 – Fire Sprinklers	 Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 3 of 4

Exterior Fire Sprinklers

Characteristics 

•	 The purpose of an exterior fire sprinkler system is to saturate the exterior of the building.

•	 Exterior sprinkler systems can be installed during new construction or on existing buildings.

They are commonly installed on the roof along the ridge line or underneath the eaves and

along soffits.

•	 Exterior sprinklers can be activated automatically by low-voltage heat detectors or manually by

occupants before they evacuate the home.

•	 Exterior sprinklers can include a warning system that notifies occupants and emergency

response personnel of a developing fire.

•	 Some landscape sprinklers are designed and installed to provide protection from a wildfire to

landscape areas immediately surrounding a building.

•	 An exterior sprinkler system can be installed so that it is substantially hidden from view.

Guidance

Exterior sprinklers mounted on the

building can be configured to use water

piping through the attic or roof or to use

piping on the exterior of the structure. If

interior pipes are used, exterior sprinklers

can be installed in conjunction with

interior sprinklers (see Figure 2). A standalone system that includes a pressurized

holding tank can be considered to ensure

an adequate water supply. See the

information about water supply under

interior fire sprinklers above.

Considerations

•	 If exterior sprinklers are installed in

areas where freezing temperatures

occur, special provisions such as dry sprinklers are required to prevent water in the piping from

freezing and rupturing it. In a dry sprinkler system, the portion of piping that is vulnerable to

freezing is not charged with water until a fire opens a valve and releases water into the piping.

•	 Exterior sprinklers can provide added protection when used in conjunction with fire-resistant

construction materials (see Fact Sheets #5–14) and defensible space (see Fact Sheet #4,

Defensible Space).

•	 Polymer gels, Class A foam products, and other long-term fire retardants can be applied to

structures prior to fire impingement and provide greater thermal protection than water alone.

Figure 2. Interior and exterior fire sprinklers can be

installed in conjunction with each other, such as this

system with a sprinkler in the attic and along the eave.

System is connected 

to the water main or a 

pressurized holding tank

Sprinklers can be 

installed in the attic 

and in the eaves
Page 4 of 4	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 15 – Fire Sprinklers

Many of these products are available to homeowners in self-contained application units and

can be applied with an attachment to a garden hose or integrated into the home’s exterior

sprinkler systems.

Effectiveness

•	 If exterior fire sprinklers require manual activation, occupants must activate the system

expeditiously for the system to be effective.

•	 High winds that are frequently a byproduct of major fire activity can significantly degrade the

effectiveness of an exterior sprinkler system.

•	 Manually applied fire-protection materials such as Class A foam products can be effective if

time is available to treat the home. To be effective, the fire-protection material must be applied

within the time frame identified by the product manufacturer.

Resources

FireSafety.gov. Residential Fire Sprinklers. http://www.firesafety.gov/citizens/ sprinklers/index.

shtm.

National Fire Protection Association. 2007. NFPA 13D: Standard for the Installation of Sprinkler 

Systems in One- and Two-Family Dwellings and Manufactured Homes. http://www.nfpa.org/

aboutthecodes/AboutTheCodes.asp?DocNum=13D.

National Fire Sprinkler Association. Information about residential sprinkler systems. http://www.

nfsa.org.
FS No. 16 – Utilities Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 1 of 3

Utilities and Exterior 

Equipment

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 16 

Purpose

To provide information about measures that can be implemented to protect utility connections

to buildings and exterior equipment from a wildfire. Guidance pertains to both new and existing

buildings.

Description

Utilities of all types that penetrate a building can be a threat to a building in a wildfire. Exterior

equipment, such as solar panels and receiver dishes, can be vulnerable to damage by the high

temperatures generated by a wildfire. The following utilities and equipment are particularly

susceptible to damage in a wildfire:

Electrical Utilities and Exterior Equipment 

Electricity is delivered to homes through aboveground conductors and drop lines (the majority

of homes) or through underground cables. Electricity is then provided to exterior equipment by

cables that are connected to the equipment from inside the home.

Fuel-related Utilities and Exterior Equipment

Many homes use pressurized gas (liquid petroleum gas, such as propane and butane, or natural

gas) or liquid fuel (fuel oil or kerosene) for heating, hot water, and cooking. Propane and butane

are stored in pressurized vessels. Natural gas is delivered through pressurized pipes that are

connected to the home. Liquid fuel is delivered to the home by gravity from on-site storage tanks.

Key Issues

General

•	 Exterior equipment often contains combustible

components that increase the risk of ignition of the

equipment and the building it is attached to.

•	 Most utilities and exterior equipment require penetration

of the building envelope for ducting and conduit (see

Figure 1). The openings may allow heat, hot gases,

and embers to enter the building and cause ignition of

combustible materials in the building interior.

Figure 1. The gap around utility

penetrations such as this one should

be filled.
Page 2 of 3	 09/08 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 16 – Utilities

•	 Combustible debris can collect around exterior equipment, increasing the probability of ignition

of the equipment and building.

Electrical Utilities and Equipment

•	 Wildfires can affect power transmission by conduction, convection, direct flame contact, and

heavy smoke. Wildfires can damage equipment such as power poles and power lines or cause

a short circuit in the lines.

•	 Power surges and power outages caused by wind and fire can damage electrically powered

equipment in homes that are miles away.

•	 As with any electrical power supply, water well power supplies are vulnerable during a wildfire.

Water well systems can be essential to domestic and fire-protection needs.

•	 Equipment mounted on roofs has the same ignition potential as the roofing assembly.

Fuel-related Utilities and Equipment

•	 Exposed, combustible delivery lines are vulnerable to wildfire. For example, gas meters are

vulnerable to wildfire damage if pipe connections include a rubberized gasket.

•	 Pressurized and liquid fuels are flammable and explosive.

•	 Venting of fuel under pressure may cause significant damage or total destruction of a building,

depending primarily on the location of the fuel container.

Guidance

General

•	 If possible, install utility and equipment connections underground, including all entry points

into the building.

•	 If a utility or equipment connection cannot be installed underground, seal gaps and

penetrations in exterior walls and roofs with fire-resistant caulk, mortar, or fire-rated expanding

foam. Fill large gaps with intumescent or fire-protective sheets or pillows. Fire-resistant wrap

may be used around ventilation features that are built into and penetrate exterior walls (such

as air conditioners).

Electrical Utilities and Equipment 

•	 Shield power cables and other wiring with noncombustible or fire-resistant materials to protect

the cables and wiring from convection, radiation, and conduction heat, and direct flame

contact.

•	 Use noncombustible or fire-resistant materials for mounting systems of roof-mounted

equipment.

•	 Use surge protectors to protect sensitive electronic equipment.
FS No. 16 – Utilities Home Builder’s Guide to Construction in Wildfire Zones	 09/08 Page 3 of 3

•	 Install Class A rated solar cell systems

for the greatest protection. Solar

cell systems are tested and rated

under the same conditions as roofing

assemblies and are available with

Class A and Class C ratings (see Fact

Sheet #5, Roofs).

Fuel-related Utilities and Equipment

•	 Bury or shield fuel lines to protect

them from radiation, conduction heat,

and direct flame contact.

•	 Bury pressurized storage vessels

underground (see Figure 2).

•	 Place fuel storage vessels 30 feet from the home and away from downhill slopes and enclose

them behind a noncombustible masonry wall.

•	 Shield gas meters from hot air and gases, convection and radiant heat, and direct contact by

flame, using noncombustible materials such as masonry or concrete.

•	 Ensure pressurized storage tanks have a pressure relief valve. As the outside temperature

rises in a wildfire, the pressure inside the tank can increase. When the pressure setting is

exceeded, the valve will open and relieve the pressure, preventing an explosion.

Considerations

•	 Replacing pipes, cables, and other installations can damage sealants for wall penetrations.

Fire-resistant sealants and noncombustible mortar must be removed and replaced each time a

cable or pipe is reinstalled.

•	 Using defensible space for the location of utilities and exterior equipment (for example, electric

water pumps, fuel tanks) should be considered (see Fact Sheet #4, Defensible Space).

Effectiveness

All measures listed in this Fact Sheet are effective in all Fire Severity Zones.

Resources

Fire-resistant expanding foam standards: ASTM E814, UL 1479, BS 476, Part 20.

Pressure relief valve standards: ASME (American Society of Mechanical Engineers) Boiler &

Pressure Vessel Code, Section VIII Division 1 and Section I.

Fuel storage tank

Filler pipe

Vent

Buried fuel lines

Figure 2. Buried fuel storage tank.

FS No. 17 – Community Infrastructure Home Builder’s Guide to Construction in Wildfire Zones 09/08 Page 1 of 5

Community 

Infrastructure

 Home Builder’s Guide to Construction in Wildfire Zones Technical Fact Sheet No. 17 

Purpose

To provide guidance about neighborhood and community-wide fire-safe practices that will

enhance fire protection in wildfire zones. Guidance pertains to community infrastructure,

including roads used for evacuation routes and emergency access, and emergency water supply.

Although a home builder may not have control over these elements, community officials and

homeowners should be aware of measures that can be taken on a community-wide basis to

increase the chances of an entire neighborhood’s survival in a wildfire.

Background

•	 Poorly designed or inadequate infrastructure can hamper fire-suppression efforts and put

citizens and firefighters at risk. Reducing the risk of wildfire damage and destruction requires

implementing measures beyond those involving an individual building or parcel. It is also

essential to enhance mitigation measures at the neighborhood and community levels, which

will effectively expand the zone of protection beyond the individual parcel or building.

•	 The local fire agency, state forestry or natural resources departments, the local office

of emergency management, or other local organizations should be contacted to obtain

information about the hazards and risks in an area.

Key Issues 

•	 Emergency response vehicles may need to access a wildfire area at the same time evacuation

traffic is leaving the area. Firefighters need safe access along roads to reach the wildfire and

access water resources.

•	 Visible street signs and property addresses provide firefighters with critical response and

location information. Property addresses are often not visible, and a road name may occur

more than once in a jurisdiction.

•	 Wildland fuels and landscape vegetation along roads can place firefighters in extremely

hazardous situations.

•	 Water resources for wildfire suppression are vital and need to be accessible.

Guidance for Roads and Driveways

•	 Roads should be wide enough to allow evacuation and emergency vehicles simultaneous

access. Minimum width is 20 feet for access roads and 12 feet for driveways (see Figure 1).
Page 2 of 5	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 17 – Community Infrastructure

•	 The maximum grade of roads and driveways

should be determined by the local

jurisdiction but in general should not exceed

a grade of 16 percent.

•	 Roads and driveways should provide

sufficient vertical clearance to allow for

large emergency vehicles. The minimum

is 13.6 feet (see Figure 1).

•	 Roads should support a minimum

of 40,000 pounds to allow for heavy

emergency vehicles.

•	 Appropriate signage, including but not

limited to weight and vertical clearance

limitations and one-way road and singlelane conditions, should be posted and fully

visible on noncombustible signs and posts.

•	 Gated access from a public roadway should

be set back from the roadway at a distance

that is sufficient to allow emergency

equipment to clear the traffic lane. A

distance of 50 feet should be adequate for

most equipment (see Figure 2).

•	 Turnarounds should be at the end of roads

and on driveways that are longer than

150 feet. The minimum inside turning

radius should not be less than 30 feet, and

the outside turning radius for a turnaround

should be 45 feet from the center line of the

road. If a hammerhead/”T” is used, the top

of the “T” should have a minimum length of

60 feet (see Figure 3).

•	 Roads and driveways should provide

all‐weather access, which may require

asphalt or concrete surfacing.

Address and Signage 

•	 Public and private roads and streets should be identified by a name or number through a

consistent jurisdiction-wide system that provides for sequenced or patterned numbering

and/or non-duplicating naming within each jurisdiction.

Figure 1. Road with adequate width for emergency

vehicles.

Figure 3. The top of the “T” used for a turnaround

(Anchor Point Group, Boulder, CO).

Figure 2. Gated access with a 50-foot setback that

allows emergency vehicles to clear the traffic lane.

13.6-foot

minimum 

clearance 20-foot minimum 

width for access roads

12-foot minimum 

width for driveways

50 feet
FS No. 17 – Community Infrastructure Home Builder’s Guide to Construction in Wildfire Zones 09/08 Page 3 of 5

•	 Size of letters, numbers, and symbols for street and road signs should have a minimum 4‐inch

letter height and 1/2-inch stroke, be reflective, and contrast with the background color of the

sign. The sign and sign support should be constructed of noncombustible materials.

•	 Street and road signs should be visible and legible from both directions of vehicle travel for a

distance of at least 100 feet and be mounted at a height of 7 feet from the road surface to the

bottom of the sign.

•	 All buildings should have a permanently posted address at each driveway entrance and should

be visible from both directions of travel along the access road.

Fuel Modification

•	 Reducing the volume and density of

combustible vegetation reduces the

intensity of wildfire. Strategic fuel

modification along access and egress

routes increases safety for emergency

fire equipment and evacuating citizens

(see Figure 4).

•	 Areas such as golf courses, schools,

and large parking lots should be labeled

as safety zones for citizens unable to

evacuate or for firefighters. It is critically

important that these areas be evaluated

by fire professionals before a safety zone

is designated.

Guidance for Emergency 

Water Supply 

•	 Community-wide water supplies need to be available and accessible.

•	 Signs should be provided indicating access to each water source.

•	 Vegetation should be maintained at each water source to allow safe access to the source.

Water Tanks and Pressure Systems

Some community water systems use tanks and cisterns to store emergency water supplies.

Individual properties may be supplied with potable water through on-site wells or limited

distribution systems due to the dispersed nature of the community or the cost of installing a

major water delivery system.

•	 Water tanks should be constructed of highly fire-resistant materials such as steel, concrete, or

ferrocement. Fiberglass tanks may be placed underground. All cisterns or water tanks used for

Figure 4. Example of a map depicting areas for planned

fuel modification along evacuation routes/fire access

roads (Anchor Point Group, Boulder, CO).
Page 4 of 5	 09/08 	 Home Builder’s Guide to Construction in Wildfire Zones	 FS No. 17 – Community Infrastructure

emergencies should have a fire department connection. The local jurisdiction may specify the

size and type of fire department connection.

•	 Pressurized systems with hydrants should conform to the local jurisdiction’s requirements or

recommendations for spacing, flow, and pressure.

•	 Installation should meet National Fire Protection Association standards at the minimum.

Dry Hydrants

Many rural areas do not have access to the pressurized hydrants that are common in larger

communities for firefighting. When pressurized systems are not available, dry hydrants are

recommended. Dry hydrants are a relatively inexpensive way to provide a ready source of water

for firefighting

A dry hydrant is a non-pressurized pipe system that allows fire equipment access to a nearby

source of water such as a lake, stream, pond, residential pool, or cistern with a minimum water

depth of 2 feet, or a water source such as a tank that is not directly accessible to a fire apparatus

(see Figure 5).

Considerations

The fire-suppression capabilities in the area, as discussed above, should be considered when

selecting a construction site (see Fact Sheet #3, Selecting the Construction Site).

For more information about infrastructure, see FEMA’s Wildfire Hazard Mitigation Handbook for

Public Facilities.

Effectiveness

The effectiveness of the recommended measures varies significantly, depending on the

infrastructure elements that are present in the community.

Figure 5. Dry hydrant designs.

2-foot minimum

Anticipated low-water level

Normal waterline elevation

Installation below frost depth

18-foot

maximum

2 feet

Strainer

Design using two 

45-degree elbows

Design using two 

90-degree elbows
FS No. 17 – Community Infrastructure Home Builder’s Guide to Construction in Wildfire Zones 09/08 Page 5 of 5

Resources

California Administrative Code Title 14, Division 1.5, §1270–1276.

International Code Council. 2006. 2006 International Wildland-Urban Interface Code.

National Fire Protection Association. 2001. NFPA Standard 1142: Standard on Water Supplies for 

Suburban and Rural Fire Fighting.

Natural Resources Conservation Service. Dry Hydrant Design Drawings. http://www.sc.nrcs.usda.

gov/technical/dryhydrant.html.

Lagucki, T. and K. Mancl. Fire Protection in Rural Areas: Dry Hydrants for Ponds. The Ohio State

University Fact Sheet: Food, Agricultural and Biological Engineering. http://ohioline.osu.edu/

aex-fact/0422.html.

Rancho Santa Fe [California] Fire Protection District. Standard for Driveways, Dead-Ends and

Looped Access Ways. http://www.rsf-fire.org/prevention/access_requirements.asp. Includes

information on fire access road and fire hydrant specifications (specifications and ordinances

may be different for other states, cities, and districts).

State of Minnesota. The Dry Hydrant Concept. http://files.dnr.state.mn.us/ assistance/backyard/

firewise/dryhydrant_advantages.pdf.

Winter, A., S. Holman, S. Kett, and R. Dolan. 2006. Taylor [Florida] Community Wildfire Protection

Plan. http://www.fl-dof.com/publications/fire_pdfs/taylor_fl_cwpp_complete.pdf. Includes

improvements to wildland fire response, such as installation of dry hydrants and upgrades to

communications equipment.