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Hardening Your Home Against Wildfire

A wildfire-safe home is an ember-resistant home. Wind-driven embers can travel a mile or more ahead of a fire and ignite homes long before flames arrive. Hardening your home means choosing materials and closing the entry points so embers find nothing to ignite.

Research after the 2007 Witch Creek Fire in San Diego County found that about two out of three destroyed homes were ignited directly or indirectly by embers, not by the fire front (Maranghides and Mell, NIST, 2009). Every major WUI fire since, from the Camp Fire to the 2025 Los Angeles fires, has repeated the pattern. The University of California publication Home Survival in Wildfire-Prone Areas: Building Materials and Design Considerations (PDF) summarizes the science.

Hardening and defensible space work as a system. Defensible space guards against flame contact and radiant heat and removes the fuels embers land in. Home hardening closes the pathways embers use to ignite the structure itself. Skip either one and the fire will find the weak link: an unmaintained yard produces exposures that even a hardened home may not survive, and a hardened home next to a juniper hedge is not hardened.

Hardening Priorities, Component by Component

Roof

The roof is your home's most exposed surface. Wood shake and shingle roofs are the single greatest cause of home loss in wildfires.

  • Roof or re-roof with Class A materials: composition shingle, metal, or tile.
  • Block openings between roof decking and covering (bird stops on tile roofs) so embers cannot lodge.
  • Keep the roof and gutters free of leaves and needles, and screen or enclose gutters.

Fire-resistant roofing

Vents, Eaves, and Soffits

Vents are direct openings into your attic and crawl space, and embers follow the airflow in.

  • Cover all vent openings with 1/16-inch to 1/8-inch corrosion-resistant metal mesh, or install ember- and flame-resistant vents (WUI vents). Never use fiberglass or plastic mesh, which melts.
  • Protect eave and cornice vents with baffles. Mesh alone is not enough in these locations.
  • Box in open eaves, or protect eaves and soffits with ignition-resistant or noncombustible materials.

Ember-resistant vents

Windows

Radiant heat can break windows before flames reach the home, letting embers ignite the interior.

  • Install dual-pane windows with at least one pane of tempered glass.
  • Limit the size and number of windows facing large areas of vegetation.
  • Use noncombustible or metal-clad frames and screens.

Fire-resistant windows

Walls and Siding

Combustible siding gives flames a path from the ground to the eaves.

  • Build or remodel with ignition-resistant materials: stucco, fiber cement, or fire-retardant-treated wood.
  • Extend noncombustible material from the foundation up at least 6 inches, and keep siding clear of the ground.
  • Maintain caulking and replace warped or deteriorated boards where embers can lodge.

Fire-resistant siding

Decks

Decks collect embers on top and shelter them underneath.

  • Build deck surfaces within 10 feet of the building with ignition-resistant, noncombustible, or other approved materials.
  • Remove everything combustible from under the deck, and screen the underside where practical.
  • Keep the deck surface and the gaps between boards free of debris.

Fire-resistant decks

Fences and Gates

A wood fence attached to the house is a fuse that carries fire to the wall.

  • Replace at least the last 5 feet of any fence that attaches to the house with a noncombustible section or metal gate.
  • Choose ignition-resistant or noncombustible materials for new fencing near structures.
  • Keep fence lines free of vegetation and stored materials.

The Rest of the Property

Chimney
Cover chimney and stovepipe outlets with a noncombustible spark arrester screen, openings between 3/8 inch and 1/2 inch, to keep your embers in and wildfire embers out.
Patio covers
Use the same ignition-resistant materials for patio coverings as for a roof.
Garage
Weather-strip around and under the garage door so embers cannot blow in. Store flammable liquids away from ignition sources, and keep a fire extinguisher and hand tools (shovel, rake, bucket, hoe) available.
Driveways and access roads
Maintain driveways and access roads to state and local codes so engines can reach your home: at least 10 feet of clearance on each side where possible, gates that open inward and are wide enough for emergency equipment, and trees trimmed so apparatus can pass.
Address numbers
California requires address numbers at least 4 inches tall on a contrasting background. Firefighters may be looking for your home at night, in smoke, with no time to spare. Illuminate the numbers if possible and place them so they are visible from both directions of travel.
Water supply
Keep garden hoses long enough to reach every part of the home and outbuildings. If you have a pool or well, consider a pump with a backup power source.

What Does Retrofitting Cost?

Headwaters Economics and IBHS have analyzed the cost of wildfire retrofits, and the results are encouraging: the highest-value actions are among the cheapest. Ember-resistant vent covers, gutter maintenance, a noncombustible Zone 0, and replacing the fence section that touches the house cost far less than a roof, and together they close the most common ignition pathways.

Get Recognized: Wildfire Prepared Home

The Insurance Institute for Business & Home Safety (IBHS) offers the Wildfire Prepared Home designation, a third-party-verified standard covering the roof, vents, Zone 0, deck, and fencing measures described on this page. The designation documents your mitigation for insurers and qualifies for discounts under California's Safer from Wildfires regulation. Start with the How to Prepare My Home checklist (PDF).

Structure-to-Structure Fire Spread

In developed neighborhoods, the largest fuel near your home may be your neighbor's home. NIST research on structure separation distance quantifies how fire spreads between buildings and what spacing, sheds, and fences contribute. NIST prepared a summary of this work for the San Mateo County FireSafe Council: NIST Structure Separation Distance findings for San Mateo FireSafe Council (PDF). The practical implication: accessory structures, fences, and stored combustibles between homes are part of your defensible space, and coordinating with neighbors matters. See Fire Safe Marin's Harden Your Home resources for more Bay Area-specific hardening guidance.

*Ignition-resistant building materials resist ignition or sustained burning when exposed to embers and small flames. Examples include noncombustible materials, exterior-grade fire-retardant-treated wood, and materials tested to State Fire Marshal Standard 12-7A-5. See the OSFM Building Materials Listing for approved WUI products.

Sources: CAL FIRE, Hardening Your Home; NIST Technical Note 1635 (Maranghides and Mell 2009); University of California ANR Publication 8393; IBHS Wildfire Prepared Home standard.