Is vinyl siding fire resistant?

No. Vinyl is combustible. It sags and falls away in heat, exposing the sheathing behind it, so a vinyl wall performs only as well as what's underneath.

Is Hardie board fire resistant?

Yes. James Hardie fiber cement siding is classified noncombustible under ASTM E136 with a flame spread of 0, and California's wildfire code accepts it. It isn't fireproof, though: windows, vents and eaves in the same wall can still let fire in.

Is LP SmartSide fire resistant?

Only as part of a State Fire Marshal listed assembly with LP FlameBlock fire-rated sheathing. That listing expired June 30, 2026 and we couldn't confirm a renewal, so check the current listing with LP or your building department first.

Three-coat stucco is noncombustible and held up well in the 2025 LA fires. Stucco homes still burned when embers or flames got in through windows, vents and eaves.

Can I paint my siding with fire retardant?

It won't count. California's wildfire code says coatings are "not an approved method of protection," and IBHS testing found coated wood performed no better than bare wood after three months outdoors.

Is the 6-inch rule just for insurance?

No. It's in California's 2025 wildfire code for new homes (504.5.1), it's required for IBHS Wildfire Prepared Home, and it's an insurance discount factor.

Do I have to replace my siding?

Not on an existing home. The siding rules apply to new construction and rebuilds. For an older home with combustible siding, start with the 6-inch base, sealing gaps and clearing the first 5 feet. Full residing pays off most when another structure is within about 30 feet.

Siding and walls

Fire-resistant siding for LA homes. Start with the bottom 6 inches.

Most LA homes are already stucco, which doesn't burn. The wall still fails at its weak spots: windows, vents, eaves, and the base where mulch, fences and debris touch it. Here's how common siding materials rate, what the code asks for, and the cheap fix most homes can do first.

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Updated November 10, 2026

80%

of LA homes IBHS surveyed after the 2025 fires had stucco walls.

6 inches

of noncombustible material at the base of the wall is now California code for new homes, an IBHS requirement and an insurance discount factor.

About $4,000

to reside one 480 sq ft wall in fiber cement with house wrap and fire-rated gypsum, per the 2024 Headwaters study.

The short answer

Noncombustible siding helps. The wall is a system.

Stucco, fiber cement, brick, stone and metal don't burn. Vinyl and plain wood do. But IBHS found after the 2025 fires that noncombustible siding "is sometimes insufficient on its own": in one case the siding got hot enough to crack while the wood window frame beside it caught fire. So the whole wall matters, including its windows, vents and eaves.

If your siding is combustible, the first step is the cheapest: give the bottom of every wall at least 6 inches of noncombustible material where it meets the ground, a deck or a lower roof. Full residing matters most when a neighbor's house or a shed is within about 30 feet, according to the 2024 Headwaters study.

Materials compared

How common siding actually rates.

Fire performance of common siding materials
Material	Fire rating	What to know
Three-coat stucco	Noncombustible	Performed well in the LA fires; IBHS saw stucco hit by a burning fence show only scorch marks. One-coat systems depend on the specific product's evaluation.
Fiber cement (James Hardie)	Noncombustible	HardiePlank, Artisan and HardieShingle are classified noncombustible under ASTM E136 with a flame spread of 0 (ICC-ES report ESR-2290, March 2026), and accepted under California's wildfire code.
Brick, stone, metal	Noncombustible	Fine on their own; seal gaps and keep fuel off the base.
Vinyl	Combustible	Sags and falls away, exposing the sheathing behind it. UC's fire network says performance depends largely on the sheathing underneath.
Plain wood lap or board	Combustible	UC's fire network says plain bevel lap joints are vulnerable to flame getting through. Usually needs fire-rated sheathing behind it to meet code.
LP SmartSide (engineered wood)	Code-compliant only in a listed assembly	Its State Fire Marshal listing paired it with LP FlameBlock fire-rated sheathing, and that listing expired June 30, 2026. We couldn't confirm a renewal, so check the current listing before relying on it.
Fire-retardant-treated wood	Can meet code if labeled for exterior use	Passes California code, but IBHS's top-level Plus standard doesn't accept any wood siding, treated or not.

Sources: UC ANR Fire Network; ICC-ES ESR-2290; LP SmartSide code documentation; IBHS 2025 LA report and Wildfire Prepared Home standard.

The 6-inch base

The cheapest siding fix is at the bottom.

Fire reaches walls from the ground up: burning mulch, a fence, debris against the house, or a deck. California's 2025 wildfire code (504.5.1) requires "a minimum of 6 inches of metal flashing or noncombustible material applied vertically on the exterior of the wall" at the ground, deck and roof intersections of new homes.

It isn't just a building rule. IBHS's Wildfire Prepared Home standard requires at least 6 inches of noncombustible material at the base of every wall (and at the base of combustible deck posts). And California's Safer from Wildfires rules list "at least six inches of noncombustible vertical clearance at the bottom of the building's exterior surface" as an insurance discount factor.

Installed costs for siding work
Item	Typical installed cost
Metal flashing over the bottom course	About $4.10 per linear foot
Noncombustible material replacing the bottom 6 to 12 inches	About $6.70 per sq ft
Fire-rated caulk for gaps wider than 1/8 inch	About $4.40 per linear foot
Fiber cement siding, installed	About $6.70 per sq ft (about $7 for woodgrain lap)
One 480 sq ft wall in fiber cement with house wrap and gypsum	About $4,000
Fiber cement soffit replacing a combustible soffit	About $4.50 per sq ft; one 40-foot side with vents about $4,000

Source: Headwaters Economics and Quarles (2024), Northern California prices. Southern California tends to land within 10 percent.

What the research shows

Siding matters most when houses are close.

LA 2025 fires (IBHS): Noncombustible siding was on 76 percent of surveyed homes in the Palisades and 89 percent in Eaton. It was one of the most common protective features, but often paired with vulnerable windows, vents and eaves.
Neighbors within 10 feet: IBHS found that with a neighboring house within 10 feet, even homes with all four key hardening features had less than a 50 percent chance of no damage. Each extra 10 feet of separation added 7 to 13 points, up to 30 feet.
California losses, 2013 to 2018: A study of more than 40,000 structures found siding mattered less than exposed eaves, vents and windows, but fire-resistant siding still showed consistently lower risk.
UC Berkeley (2025): Separation between structures was the most influential factor, and "exterior siding and window materials substantially contributed" to a home's vulnerability.

What the code says

Noncombustible or ignition-resistant.

For new homes in fire zones, California's 2025 wildfire code accepts wall coverings that are noncombustible (they pass ASTM E136), ignition-resistant and labeled for exterior use, fire-retardant-treated wood, or a wall assembly that passes a 10-minute direct flame test. Ignition-resistant materials must pass an extended 30-minute flame spread test after accelerated weathering.

One thing never counts: "Use of paints, coatings, stains or other surface treatments are not an approved method of protection" (503.2.5). No existing home has to reside under state rules. These requirements apply when you build new or rebuild.

How RF1 helps

We find the weak walls and plan the fix.

Mark walks every wall during the assessment, checking siding type, the base where it meets soil, decks and roofs, gaps around vents and windows, and how close neighbors and sheds sit. You get a plan in order of protection per dollar. RF1 coordinates the vent, gap-sealing and Zone 0 work around the walls, and helps you scope larger siding projects with a qualified contractor.

Book a free assessment

Questions

Siding questions we hear most.

Is vinyl siding fire resistant?: No. Vinyl is combustible. It sags and falls away in heat, exposing the sheathing behind it, so a vinyl wall performs only as well as what's underneath.
Is Hardie board fire resistant?: Yes. James Hardie fiber cement siding is classified noncombustible under ASTM E136 with a flame spread of 0, and California's wildfire code accepts it. It isn't fireproof, though: windows, vents and eaves in the same wall can still let fire in.
Is LP SmartSide fire resistant?: Only as part of a State Fire Marshal listed assembly with LP FlameBlock fire-rated sheathing. That listing expired June 30, 2026 and we couldn't confirm a renewal, so check the current listing with LP or your building department first.
Is stucco fireproof?: Three-coat stucco is noncombustible and held up well in the 2025 LA fires. Stucco homes still burned when embers or flames got in through windows, vents and eaves.
Can I paint my siding with fire retardant?: It won't count. California's wildfire code says coatings are "not an approved method of protection," and IBHS testing found coated wood performed no better than bare wood after three months outdoors.
Is the 6-inch rule just for insurance?: No. It's in California's 2025 wildfire code for new homes (504.5.1), it's required for IBHS Wildfire Prepared Home, and it's an insurance discount factor.
Do I have to replace my siding?: Not on an existing home. The siding rules apply to new construction and rebuilds. For an older home with combustible siding, start with the 6-inch base, sealing gaps and clearing the first 5 feet. Full residing pays off most when another structure is within about 30 feet.

Keep going

Home hardening in Los AngelesThe full order of work, costs and who inspects Fire-resistant windowsTempered vs dual pane, frames, screens and shutters Fire-resistant fences and decksThe fence-to-house connection, decking and under-deck rules Home hardening rankedEvery measure by what it does and costs

Sources

Facts checked November 10, 2026. Costs are rounded from the 2024 Headwaters Economics study for CAL FIRE (Northern California prices; Southern California tends to land within 10 percent). They're a benchmark, not RF1 quotes.

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