Resources for Design and Building Professionals
As design and building professionals, you have an opportunity to guide affected property owners and build healthy and comfortable buildings that are also more resilient to hazards and risk. We want to make that as easy as possible, and we want to work with you. This website is a work in progress and will be updated as more resources become available.
To review Cal Fire’s proposed updated Fire Hazard Severity Zones, please see this comparison map, which allows you to look at the current zones and proposed zones. State law requires Los Angeles County to adopt the recommended maps by ordinance within 120 days of their issuance, which was March 24, 2025. For a description of the adoption process and to submit public comments, please visit the Los Angeles County Fire Department Defensible Space website here.
* NOTE: The California Fire Code is currently being updated and will take effect July 1, 2025. The Los Angeles County Fire Code will become effective January 1, 2026.
Research on wildfires points to embers and small flames as the leading cause of ignition. Embers are burning pieces of airborne wood and/or vegetation particles can be carried more than a mile by the wind. They can cause spot fires and ignite buildings, debris, and other objects. Construction and landscaping can help buildings withstand windblown embers by minimizing the likelihood of flames touching the building or any attachments and reducing the chance of fire spreading.
Ignition-resistant material shall be labeled for exterior use and shall exhibit a listed frame spread index of not exceeding 25 when tested in accordance with ASTM E84 or UL 723. 2, or with ASTM E or UL723 testing continued for an additional 20-minute-period with the material not exhibiting a flame front that does not progress more than 10 ½ feet (3200 mm) beyond the centerline of the burner at any time during the test period.
Though there are references here to treated and/or fire-retardant materials, it is strongly encouraged to use healthier, non-toxic materials when available and within budget. As our communities recover and rebuild, we should be supporting healthy, efficient, and resilient buildings and properties for the safety of all.
Roofs are highly vulnerable parts of a building during a wildfire, due to the large surface areas.
Use Grade A roof covering materials. Grade A roof coverings provide the best performance against fires. Common Class A roof coverings include asphalt fiberglass composition shingles, concrete standing metal seam, and flat/barrel-shaped tiles. Provide the ICC/UL ESR number of the roofing material selected when getting a roofing permit. Guidelines for Very High Fire Hazard Severity Zone requirements shall be satisfied.
Roofs shall have a roofing assembly installed in accordance with its listing and the manufacturer’s installation instructions. Wood shingles and wood shakes are prohibited in any Fire Hazard Severity Zone regardless of classification. Fire-retardant – treated wood shingles and shakes shall be approved and listed by California State Fire Marshall and have passed the weather test. See CA Fire Marshall Building Material Listing website.
Where the roof profile allows space between the roof covering and roof decking [CRC 337.5.2], The spaces shall be constructed to prevent the intrusion of flames and embers, the spaces shall be constructed to prevent the intrusion of flames and embers, be fire stopped with approved materials, or have one layer of minimum 72-pound mineral surfaced nonperforated cap sheet complying with ASTM D3909 installed over the combustible decking.
Consider a simple shape. Additional architectural details can add additional surfaces, nooks, and corners where embers can collect.
Where roof valley flashing is installed [CRC337.5.3], the flashing shall be not less than 0.019-inch No. 26 gage galvanized sheet installed over not less than on layer of minimum 72-pound mineral-surfaced non-perforated cap sheet complying with ASTM D 3909, at least 36- inch-wide running the full length of the valley.
Study your roof’s aspect ratio. If the widest exterior of the structure faces the direction from which a fire is likely to come, it will be more vulnerable. More fire-resistive materials may be needed on the side that faces the oncoming fire.
Enclose Eaves. Enclose roof eaves and fascias, and screen in soffits and roof vents with 1/8” or smaller metal mesh to resist sucking in embers.
The exposed underside of enclosed roof eaves having either a boxed-in roof eave soffit with a horizontal underside, or sloping rafter tails with an exterior covering applied to the underside of the rafter tails, shall be protected by: noncombustible material, ignition-resistant material, fire retardant material, materials approved for not less than 1-hour fire resistance-rated construction on the exterior side as tested by ASTM E119 or UL 263, one layer of 5/8-inch Type X gypsum sheathing applied behind an exterior covering on the underside of the rafter tails or soffit, the exterior portion of a 1-hour fire resistive exterior wall assembly designed for exterior fire exposure, boxed-in roof eave soffits per Section 337.7.11, when tested in accordance with ASTM E2957, Boxed-in roof eave soffits per SFM Standard 12-7A-3. Exceptions are fascia and other architectural trim boards.
Very High Fire Hazard Severity Zone Eaves Details
Open (Exposed) Roof Eaves. The exposed roof deck on the underside of unenclosed roof eaves shall consist of one of the following: noncombustible material, ignition-resistant material, fire-retardant treated wood; One layer of 5/8-inch Type X gypsum sheathing applied behind an exterior covering on the underside exterior of the roof deck; exterior portion of a 1-hour fire-resistance-rated exterior assembly applied to the underside of the roof deck designed for fire exposure per Gypsum Association Fire Resistance Design Manual and tested in accordance with ASTM E119 or UL263. Exceptions are fascia and other architectural trim boards.
Exterior Porch Ceilings. The exposed underside of exterior porch ceilings shall be protected by one of the following: noncombustible material, ignition-resistant material, fire-retardant-treated wood shall be labeled for exterior use and shall meet the requirements of Section 2303.2 of the California Building Code, materials approved for not less than 1-hour fire resistance-rated construction on the exterior side as tested by ASTM E119 or UL 263, One layer of 5/8-inch Type X gypsum sheathing applied behind the exterior covering on the underside of the ceiling, the exterior portion of a 1-hour fire resistive exterior wall assembly designed for exterior fire exposure, porch ceiling assemblies with a horizontal underside that meets Section R337.7.11, when tested in accordance with ASTM E2957, or porch ceiling assemblies with a horizontal underside that meets SFM Standard 12-7A-3.
Maintain your roof. Keep your roof clear of debris and vegetation, including gutters, solar panel attachments, and corners.
The sides of a building are vulnerable to embers casts and radiant heat from burning vegetation or highly flammable items like parked cars parked.
Screen Vents. Install metal mesh screens with a maximum opening of 1/8 inch to all exterior vent openings to prevent embers from entering attics, crawlspaces, or HVAC ducts. The materials shall be noncombustible except vents located under the roof covering, along the ridge, with noncombustible wire mesh and corrosion resistant.
Ventilation openings shall be fully covered with Wildland Flame and Ember Resistant (WUI) vents approved and listed by the California State Fire Marshal, or WUI vents listed to ASTM E2886.
Upgrade Windows and Doors. Windows and glass doors can blow out due to heat. Install or upgrade to double or triple-paned windows with tempered glass that is resistant to separating, even when cracked. Noncombustible metal framed windows are the best choice.
Exterior windows and exterior glazed door assemblies shall comply with multi-pane glazing with a minimum of one-tempered pane meeting the Safety Glazing requirements of CBC Sec. 2406 and R308; Residential Green Building Notes from LA County Exterior doors shall comply with the exterior surface or cladding shall be of noncombustible or ignition-resistant material, or constructed of solid core wood that has stiles and rails shall not be less than 1- 3/8 inches thick, or raised panels shall not be less than 1-1/4 inch thick, except for perimeter of the raised panel that may taper to a tongue not less than 3/8-inch think. Fire resistant doors shall have not less than 20 minutes of fire resistance. Exterior door surface or cladding shall meet the performance requirements to Section 707.A.3.1 when tested in accordance with ASTM E2707 or State Fire Marshall (SFM) Standard 12-7A-1.
Use Fire-Resistant Siding, Roofing & Insulation. Choose siding and roofing materials that are fire resistant. Use insulation that is fire resistant such as cellulose or rockwool, not fiberglass or foam.
Install Gutter Guards. Choose noncombustible gutter guards that shed leaves and needles while still letting water through rather than letting leaves and needles accumulate. Roof gutters shall be provided with the means to prevent the accumulation of leaves and debris in the gutter. [R337.5.4]
Add a facade. Adding a 5-foot exterior wall made of fire-resistant materials (e.g. brick) to all perimeter walls may keep embers from damaging the sides of buildings.
Exterior wall covering or wall assembly shall be one of the following: noncombustible material, ignition resistant material, heavy timber construction, log wall construction, complies with ASTM E2707 and SFM Standard 12-7A-1, exterior fire exposure with a 1-hour fire-resistance rating, rated from the exterior side, as tested in accordance with ASTM E119 or UL 263, exterior fire exposure containing one layer of 5/8-inch (15.9 mm) Type X gypsum sheathing applied behind the exterior wall covering or cladding on the exterior side of the framing. Exterior wall coverings shall extend from the top of the foundation to the roof and terminate at 2-inch nominal solid wood blocking between rafters at all roof overhangs, or in the enclosed eaves, terminate at the enclosure. The following are exempt: architectural trim, fascia and gutters; roof or wall corner projections or similar, and deck walking surfaces complying with Section 337.9.
Garage Door Perimeter Gap. Exterior garage doors shall resist the intrusion of embers from entering by preventing gaps between doors and door openings, at the bottom, sides and tops of doors, from exceeding 1/8 inch. Gaps between doors and door openings shall be controlled by weather stripping hazards, door overlaps onto jambs and headers, and garage door jambs and headers covered by metal flashing.
Decking. The walking surface material of decks, porches, balconies and stairs when any portion of such surface is within 10 ft of the building shall be ignition resistant, noncombustible, or made of materials complying with fire testing conditions of ASTM and SFM standards.
How plants and structures around a building can also help reduce risks from fires.
Clear the First Five Feet (Zone 0). Remove vegetation and mulch from the first five of a building to help reduce burning vegetation from the sides and vents of the building. Use noncombustible ground cover like gravel or rocks within these first 5 feet. This action is a cheap and effective way to make a building more resilient.
Enclose Under Decks. Use mesh screens with a maximum opening of 1/8 inch to enclose the area under decks so embers do not fly under and collect. Do not store combustible materials (i.e. firewood, plastic furniture, etc.) underneath the deck.
Build Fire-resistant Fences. Use concrete/stone or metal fencing material to help direct flames from structures and reduce fire from traveling along the fence.
Residential Green Building Notes from LA County. Group U occupancy accessory buildings and miscellaneous structures that have potential to pose a significant exterior fire exposure hazard during wildfires shall be constructed with ignition resistant, noncombustible, or fire-retardant treated materials.
Cut Fuel Bridges. Use masonry or metal barriers to separate decks, fences, porches, and outbuildings made with combustible materials from the house.
The California Energy Commission (CEC) provides educational assistance to building industry professionals on energy code compliance.
Energy efficient equipment incentive research tool for property owners and contractors.
Incentive Lookup for Customers | The Switch Is On Incentive Finder
LA County Public Work
- LA County PW Publications
- LA County PW Residential Plan General Notes
- LA County PW Very High Fire Severity Zone Notes
- LA County PW Green Building Standards Code Notes
NOTE: The California Fire Code is currently being updated and will take effect July 1, 2025. The Los Angeles County Fire Code will become effective January 1, 2026.