Does fire retardant spray work on a house?

Not for long. Gels work only while wet, and in red-flag conditions they lose half their water in under 1.5 hours. Long-life exterior coatings lost their benefit within 3 to 12 months in IBHS and US Forest Service tests.

Can I fireproof my house with paint?

No. California's wildfire code says coatings are "not an approved method of protection," and a Class A rating on the label comes from a 10-minute flame spread test, not a wildfire test.

Should I gel my house before I evacuate?

Researchers recommend leaving gel to first responders and focusing on getting out. IBHS found dried petroleum-based gel can make wood easier to ignite than untreated wood.

Do roof sprinklers work in wildfires?

Possibly, as a supplement on a house that's already hardened. There's no US performance standard, wind can carry off up to 40 percent of the water, and protection from embers entering vents is unknown, according to IBHS.

Should I leave my sprinklers on when I evacuate?

No. LA County Fire says leaving sprinklers or water running can drop the water pressure firefighters need. Connect your garden hoses so crews can use them.

Do I need a pump, tank and generator for an exterior sprinkler system?

For any serious system, yes, according to IBHS, because hydrant pressure and grid power often fail during a fire. Each of those parts needs its own protection.

What does Class A mean on fire-retardant paint?

It's an ASTM E84 rating for how fast flame spreads across a surface in a 10-minute lab test, the same rating used for interior finishes. It doesn't measure embers, radiant heat or weathering.

Paint, gels and sprinklers

Do fire-resistant paint, gels and sprinklers work? Not as a substitute.

Sprays, gels and roof sprinklers are easy to buy and easy to believe in. The testing is less kind. Here's what IBHS, the US Forest Service and California code say, and where these products fit, if anywhere.

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Updated November 10, 2026

3 months

of outdoor weathering, and IBHS found fire-retardant coatings gave no benefit over bare wood.

Under 1.5 hrs

for fire gel to lose half its water in red-flag wind and humidity, IBHS found.

Up to 40%

of the water from exterior sprinklers can blow downwind in a wildfire, with up to 20 percent more evaporating, per IBHS.

The short answer

Harden the house first. These come last, if at all.

California's 2025 wildfire code says it outright: "Use of paints, coatings, stains or other surface treatments are not an approved method of protection." Long-life coatings lost their benefit within months in testing. Gels work only while wet, which is hours. Sprinklers have no US test standard, and IBHS says passive hardening "should never be replaced" by them.

At best they're event-day supplements on a house that's already hardened. The same money usually does more on vents, gutters and the first 5 feet.

Paint and coatings

Fire-retardant paint doesn't last outdoors.

IBHS coatings tests (2017): Five products that each claimed "up to five years" outdoors and a Class A rating. Two "did not enhance fire-retardant performance over uncoated wood, even in baseline testing." The other three showed no benefit after just three months of outdoor weathering.
US Forest Service (2026): After one year of natural weathering, "no char expansion of the intumescent paint occurred." In other words, the swelling layer that's supposed to protect the wood never formed.
Code and certification: California's wildfire code doesn't accept coatings (503.2.5). IBHS doesn't accept treated wood roofs at any level of its standard, or treated wood siding at its Plus level, because of the uncertain service life of treatments and coatings. The 2024 Headwaters cost study left coatings out entirely for the same reason.
Enforcement in California: In 2019 the Santa Barbara District Attorney and the LA City Attorney sued the maker of a spray-on fire retardant over claims it lasted "5+ years" after one application. Their expert found treated and untreated wood performed about the same.

The Class A label

Class A on a paint can isn't a wildfire test.

Many coatings advertise a "Class A" rating. That comes from ASTM E84, a 10-minute tunnel test of how fast flame spreads across a surface, the same rating used for interior finishes. Class A means a flame spread index of 0 to 25. It doesn't test embers, radiant heat or how the coating holds up in sun and rain, and it doesn't make a material noncombustible.

California's ignition-resistant standard for building materials is a much tougher 30-minute version of that test, run after accelerated weathering, and coatings can't be used to meet it. A Class A roof rating is a different test again (ASTM E108), which is covered in our roof guide.

Fire gels

Gel works while it's wet. That's hours.

IBHS tested fire-retardant gels in 2019. Fully wet gel raised the time to ignition "from 15 seconds to over 7 minutes." But at 10 percent humidity and 22 mph wind, typical red-flag conditions, the gel reached "50% dehydration in less than 1.5 hours and full dehydration in 7 hours."

Worse, IBHS warned that "a completely dehydrated petroleum-based mixing agent gel may create a hazardous condition more susceptible to ignition than untreated" wood. A 2021 study in Fire Technology concluded gels should be applied only by first responders, and homeowners should focus on evacuating.

Exterior and roof sprinklers

Sprinklers are unproven, and wind steals the water.

Little research, no standard: IBHS's 2024 review says "limited methodical research exists on their real-world effectiveness," and there's no US test standard. Plastic irrigation parts are prone to failing in heat.
Wind and power: Up to 40 percent of the water can drift downwind and up to 20 percent can evaporate. Any serious system needs its own water supply, a dedicated pump, and a generator or battery, since hydrant pressure and grid power often fail in a fire. IBHS calls protection from embers entering vents "unknown."
Don't leave them running: LA County Fire says: "Don't leave sprinklers on or water running. They can affect critical water pressure." Connect garden hoses so firefighters can use them instead. Fire Safe Marin says garden sprinklers can lower water pressure for a whole neighborhood.
The Palisades water system: LADWP's preliminary report blamed extraordinary demand on one trunk line, which drained three large tanks. Residents' sprinklers and hoses, and broken pipes in burning homes, added to that demand. They were one contributor, not the cause.

Fire Safe Marin's view sums it up: hardening "is likely to be more effective than any exterior sprinkler, foam, or gel system." If you do buy a system, treat it as a supplement on a hardened house, with its own water and power, and be wary of performance claims that haven't been independently tested.

What works better

Where the same money goes further.

Ember-resistant vents: About $53 to $421 per vent installed. Compare vent types.
Gutters and roof edge: Metal guards about $4.50 per foot plus a metal drip edge. Roof and gutter guide.
The first 5 feet: Gravel in place of bark mulch, about $2,800 for a typical house. Plants and landscaping.
The fence at the house: A metal gate or section where the fence meets the wall. Fences and decks.

How RF1 helps

We start with what's proven, and say so.

An RF1 assessment ranks your fixes by protection per dollar using the research on this page. That almost always means vents, gaps, gutters, the first 5 feet and fence connections before any spray or sprinkler. If you want a fire-resistant spray or a sprinkler system as an add-on once those are done, we'll tell you where it fits and what it can't do.

Book a free assessment

Questions

Paint, gel and sprinkler questions we hear most.

Does fire retardant spray work on a house?: Not for long. Gels work only while wet, and in red-flag conditions they lose half their water in under 1.5 hours. Long-life exterior coatings lost their benefit within 3 to 12 months in IBHS and US Forest Service tests.
Can I fireproof my house with paint?: No. California's wildfire code says coatings are "not an approved method of protection," and a Class A rating on the label comes from a 10-minute flame spread test, not a wildfire test.
Should I gel my house before I evacuate?: Researchers recommend leaving gel to first responders and focusing on getting out. IBHS found dried petroleum-based gel can make wood easier to ignite than untreated wood.
Do roof sprinklers work in wildfires?: Possibly, as a supplement on a house that's already hardened. There's no US performance standard, wind can carry off up to 40 percent of the water, and protection from embers entering vents is unknown, according to IBHS.
Should I leave my sprinklers on when I evacuate?: No. LA County Fire says leaving sprinklers or water running can drop the water pressure firefighters need. Connect your garden hoses so crews can use them.
Do I need a pump, tank and generator for an exterior sprinkler system?: For any serious system, yes, according to IBHS, because hydrant pressure and grid power often fail during a fire. Each of those parts needs its own protection.
What does Class A mean on fire-retardant paint?: It's an ASTM E84 rating for how fast flame spreads across a surface in a 10-minute lab test, the same rating used for interior finishes. It doesn't measure embers, radiant heat or weathering.

Keep going

Home hardening in Los AngelesThe full order of work, costs and who inspects Fire-resistant roofs and guttersClass A, tile roof gaps, gutters, and LA's wood shake ban Fire-resistant sidingStucco, Hardie, vinyl and LP, plus the 6-inch base fix 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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