Wildfire-Resistant Siding and Windows in California

Much of the Sierra foothills, the Tahoe Basin and the hills around the Bay Area sit in mapped wildfire hazard zones. This page explains what California’s wildfire construction rules actually require in 2026, with sources, and gathers our guides on fire-resistant siding, windows and rebuilding. For mountain homes generally, see our Tahoe and foothill guides.

What the rules say in 2026

California’s wildfire construction rules changed on 1 January 2026, and much of what is published online still describes the old ones. This is the short version, with its sources. Rules change and local departments add their own, so treat this as orientation and confirm with your building department before you buy materials. Checked against the sources below on 25 September 2026.

The code has a new name

Wildfire-resistant construction is now governed by the 2025 California Wildland-Urban Interface Code (Title 24, Part 7), Chapter 5, in effect since 1 January 2026. It replaced Chapter 7A of the California Building Code and Section R337 of the Residential Code, which now just point to it. (BSC, 2025 Part 2 Chapters 5, 7, 7A and 8; California Building Standards Commission, 2025 Title 24 code changes.)

Where it applies

The code applies to new buildings in State Responsibility Areas, in areas the State Fire Marshal identifies as High or Very High Fire Hazard Severity Zones in local responsibility areas, and in areas a city or county designates itself. Local agencies can add areas, and some do: the Town of Truckee, for example, is treated in full as a Very High zone. You can look up an address in the State Fire Marshal’s hazard zone viewer; the State Fire Marshal released updated local-area maps in 2025, and each city or county adopts them by ordinance. (BSC emergency rulemaking SFM EF 01/25; Office of the State Fire Marshal, Fire Hazard Severity Zones; Town of Truckee 2025 WUI Code conformance checklist.)

Re-siding or replacing windows on an existing house

This is the question most homeowners actually have, and the honest answer is that your local building department decides. The state code’s application section covers new buildings; a general rule for alterations to existing buildings has been proposed but, as of 25 September 2026, not adopted. Re-roofing is the one alteration the state code explicitly covers. The old exemption for remodels of homes built before July 2008 was removed on 1 January 2026, and many departments now specify fire-zone materials on re-siding permits. In practice, a re-side in a hazard zone is usually specified to the same standard as new construction. (BSC emergency rulemaking SFM EF 01/25.)

Siding

For new construction, exterior wall coverings must be noncombustible or ignition-resistant material, exterior-rated fire-retardant-treated wood, or part of a wall assembly that has passed the required fire tests. Paints, coatings and stains do not count as protection. Fiber cement siding such as James Hardie is noncombustible when tested to ASTM E136, and James Hardie products are listed by the State Fire Marshal for exterior walls. Vinyl is combustible and generally qualifies only as part of a tested assembly. (OSFM Building Materials Listing; ICC-ES evaluation report ESR-2290.)

Windows, vents and eaves

Windows and glazed doors must have multiple panes with at least one tempered pane, or be glass block, 20-minute fire-rated glazing, or glazing that meets the State Fire Marshal’s test standard. A change requiring the inner pane to be the tempered one has been proposed but was not in effect as of 25 September 2026. Vents must be ember- and flame-resistant vents listed by the State Fire Marshal or tested to ASTM E2886; the familiar 1/16 to 1/8 inch mesh specification is the rule for certain roof vents and an insurance-discount criterion, not the general vent requirement. Eaves and fascias have their own material list.

Zone 0: the first five feet

State law requires 100 feet of defensible space in state responsibility areas and in Very High zones, including a 5-foot ember-resistant zone once the Board of Forestry’s regulations take effect. The Board adopted those regulations on 19 August 2026, but as of 25 September 2026 they were not yet in effect. For existing homes, the adopted text would phase in, with some items required immediately and others over three to five years. It governs vegetation, mulch, fences and stored material near the house, not the siding itself. Keeping the first five feet clear is CAL FIRE’s guidance today regardless. (Public Resources Code §4291; Government Code §51182; Board of Forestry, Zone 0 rulemaking.)

Lake Tahoe Basin

The Tahoe Regional Planning Agency exempts replacing siding and windows from its own review, but on houses visible from scenic travel routes and designated recreation areas, siding and paint must be subdued earth tones. The county or city building department still handles the permit. (TRPA Code of Ordinances §2.3.2.C and §36.6.1.D.)

Insurance

California’s Safer from Wildfires regulation requires insurers that rate for wildfire risk to recognize specific mitigation measures, including a Class A roof, ember-resistant vents, enclosed eaves, upgraded windows and 6 inches of noncombustible material at the base of exterior walls. These are insurance criteria, not building code, and each insurer files its own discounts. The IBHS Wildfire Prepared Home program offers a separate third-party designation. (California Department of Insurance, Safer from Wildfires; IBHS Wildfire Prepared Home.)

Start here

Our main guides to choosing siding for a wildfire zone.

• Best siding for California wildfire zones — materials compared for Tahoe, El Dorado and foothill homes.
• Do I need fire-resistant siding?
• Is James Hardie siding fire-resistant?
• Why fiber cement suits wildfire-prone areas
• How fire season affects siding — home hardening beyond the siding itself.

By region

Hazard maps, local amendments and building departments differ from county to county.

• Fire-resistant siding in the Tahoe Basin
• Tahoe siding permits and fire codes
• Fire-resistant siding in El Dorado County
• Arnold and Angels Camp
• Paradise — rebuilding and renovating on the ridge.
• Bay Area wildfire risk

Rebuilding and restoration after a fire

• Fire-resistant siding and windows after a wildfire — including code-upgrade insurance coverage.
• Fire-safe siding and windows after house fire damage
• Fire and water damage restoration
• Heat damage from grills and fire pits

Insurance and commercial buildings

• How siding affects home insurance in fire-prone areas
• Fire-resistant siding for commercial buildings

Talking to us about a fire-zone project

We check your address against the hazard maps and your building department’s current requirements before we specify anything, and we put the materials and the permit path in writing. Ask us for an estimate, or read our glossary for the terms above.

Rules summarized on this page were checked against the linked primary sources on 25 September 2026. Codes, maps and regulations change, and cities, counties and fire districts can adopt stricter local rules, so confirm current requirements with your building department and fire district. This page is general information, not legal advice.