Fire resistant roofing is roofing that carries a Class A, B, or C fire rating under ASTM E108 or UL 790, and for wildfire exposure you want Class A, the highest rating. Class A means the covering resists flame spread across its surface, survives repeated flame contact, and stops a burning ember (a “brand”) from igniting the deck underneath. In mapped wildfire zones, a Class A roof assembly is not optional. It is code.
The roof is the largest surface a home presents to falling embers, and embers, not the wall of flame, start most structures burning in a wildfire. This guide breaks down the three fire ratings, the three tests behind them, which materials earn Class A on their own versus only as part of a layered assembly, and what wildland-urban interface (WUI) code actually requires in 2026.
What does a Class A fire rating mean for a roof?
A Class A fire rating is the highest of three roof-covering fire classifications defined by ASTM E108 and its identical counterpart UL 790. A Class A roof covering resists severe fire exposure from outside the building, limits how far flame spreads across the surface, and prevents a burning brand from penetrating to the roof deck. Class A is the rating wildfire codes require.
The rating measures how a roof handles fire coming from above, meaning airborne embers and radiant heat from a nearby structure or vegetation. It does not measure fire coming from inside the attic. That is a separate concern handled by the ceiling and deck assembly, not the roof covering.
Ratings apply to a tested product or to a tested assembly. That distinction, covered in detail below, is where most homeowners and even some contractors get tripped up. A shingle stamped “Class A” is not automatically a Class A roof once it is on your house.
Class A vs Class B vs Class C roof ratings
The three roof fire classes describe descending levels of resistance to external fire. Class A withstands severe exposure, Class B moderate exposure, and Class C light exposure. A fourth category, “unrated,” covers materials like untreated wood shake that pass no test at all. For a wildfire area, only Class A is a defensible choice, and it is the only class WUI code accepts.
| Class | Fire exposure resisted | Burning brand size (test) | Typical use |
|---|---|---|---|
| Class A | Severe | Large brand, about 12 by 12 inches, ~2,000 grams | Wildfire zones, WUI code, most jurisdictions |
| Class B | Moderate | Medium brand, about 6 by 6 inches | Limited use, some commercial |
| Class C | Light | Small brand, about 1.5 by 1.5 inches | Low-risk areas only |
| Unrated | None | No brand test passed | Untreated wood shake, banned in most fire zones |
The class gap is real, not cosmetic. The Class A burning brand weighs roughly twenty times the Class C brand and represents the kind of flaming debris a wildfire lofts onto a roof. A Class C roof that shrugs off a small ember can still ignite under the ember load of an actual wildfire.
How ASTM E108 and UL 790 test fire resistance
ASTM E108 and UL 790 are the same test protocol, and a roof covering earns its class by passing three separate fire exposures. The three tests are the spread-of-flame test, the intermittent-flame test, and the burning-brand test. A material must pass all three at a given class to carry that rating. The burning brand is usually the hardest to pass and the most relevant to wildfire.
- Spread of flame. A gas flame plays across the roof sample on a slope, and testers measure how far fire travels over the surface. Class A allows the least spread, no more than roughly 6 feet.
- Intermittent flame exposure. The flame is applied and removed in repeated cycles to simulate a fire that flares, dies down, and flares again. The covering must not sustain flaming or expose the deck.
- Burning brand. A flaming wood block, the “brand,” is set on the roof and left to burn out. This mimics an ember landing. Class A uses the largest brand. The roof passes only if the brand does not burn through to the deck or spread flame.
Some assemblies also face a rain-and-weathering conditioning step before testing, because a fire retardant that washes out in the first storm is worthless. When you see “Class A by assembly,” it means the full tested build, covering plus underlayment plus deck, passed these three exposures together, not the shingle alone.
Stand-alone Class A vs Class A by assembly
A “stand-alone” Class A material earns the rating by itself, on a standard deck, with no special fire barrier underneath. A “by assembly” Class A material earns the rating only when installed over a specified underlayment or cap sheet that carries the fire. This is the single most misunderstood point in fire resistant roofing, and it changes what you have to buy.
| Rating path | What earns the rating | Examples | Installer risk |
|---|---|---|---|
| Stand-alone Class A | The covering itself, on a code deck | Fiberglass asphalt shingles, concrete tile, clay tile, most slate | Low, hard to void by underlayment choice |
| Class A by assembly | Covering plus a required fire barrier below | Aluminum and some steel panels, recycled rubber/plastic tiles, fire-retardant-treated wood shakes | High, wrong underlayment voids the rating |
The practical failure looks like this: a homeowner buys a “Class A” recycled-rubber shake, the installer skips the specified glass-fiber cap sheet or gypsum barrier to save a few hundred dollars, and the finished roof is not a Class A assembly. It fails an inspection or, worse, fails in a fire. Always confirm whether your covering is stand-alone or by-assembly, and if by assembly, get the exact underlayment spec from the manufacturer’s listing.
Fire resistant roofing materials by rating
Most mainstream roofing materials can reach Class A, but the path differs. Fiberglass asphalt shingles, concrete and clay tile, and slate are typically stand-alone Class A. Metal, recycled composites, and treated wood usually need a rated assembly. Untreated wood shake earns no rating and is barred from most fire zones.
| Material | Best achievable rating | Rating path | Wildfire notes |
|---|---|---|---|
| Fiberglass asphalt shingle | Class A | Stand-alone (fiberglass mat) | Most common Class A roof; organic-mat asphalt is only Class C |
| Concrete tile | Class A | Stand-alone | Excellent; seal the ends of barrel tiles to block ember entry |
| Clay tile | Class A | Stand-alone | Non-combustible; bird-stop the eaves so embers cannot lodge under tiles |
| Slate (natural) | Class A | Stand-alone | Non-combustible and long-lived; heavy, needs framing check |
| Metal (steel, aluminum) | Class A | By assembly (needs rated underlayment) | Non-combustible panel, but a rated barrier below is required |
| Stone-coated steel | Class A | By assembly | Metal fire performance with a tile look |
| Recycled rubber/plastic composite | Class A | By assembly (cap sheet) | Rating voids if the barrier is skipped |
| Fire-retardant-treated wood shake | Class A or B | By assembly | Treatment must be listed; verify it is a pressure-impregnated product |
| Untreated wood shake/shingle | Unrated | None | Banned in most WUI and fire-hazard zones |
Note the asphalt subtlety: the fiberglass-mat shingles sold today are Class A, but older organic-felt asphalt shingles were only Class C. If you are matching an existing roof or buying salvage, confirm the mat type. For a broader side-by-side on cost and lifespan across these materials, see our roofing materials comparison, and for the panel and profile options within metal, our guide to metal roofing types.
What is the best roof for wildfire areas?
The best roof for wildfire areas is a Class A assembly with no gaps where embers can lodge, and among Class A options, non-combustible coverings like concrete tile, clay tile, and metal give the widest safety margin. Fiberglass asphalt shingles are the most affordable Class A choice and are fully code-compliant. The covering class matters, but ember-blocking details often decide whether a home survives.
Field investigations after major California fires repeatedly found that homes ignited not through the roof covering but through gaps: open eaves, unscreened vents, and the space under the first course of barrel tiles. A Class A tile roof with unsealed tile ends still lets embers reach the combustible battens and underlayment.
Because of that, the strongest wildfire roofs pair a Class A covering with these details:
- Bird stops or mortar at the eave course of tile roofs to close the openings under barrel or S-tiles.
- Ember-resistant (1/8-inch mesh) vents so the attic cannot pull embers in.
- Non-combustible drip edge and eave/fascia detailing so flame cannot creep up under the covering.
- Class A rated underlayment, especially for any by-assembly covering.
For a parallel look at how code-driven roofing works in another disaster zone, our best roof for hurricane zones guide covers the same product-versus-assembly logic applied to wind uplift.
WUI roof requirements and Chapter 7A in 2026
Homes in a mapped wildland-urban interface (WUI) or fire hazard severity zone must use a Class A roof assembly under wildfire building codes. In California, that requirement lives in California Building Code and Residential Code Chapter 7A; nationally, the model rule is the International Wildland-Urban Interface Code (IWUIC). As of January 1, 2026, California’s WUI provisions apply to new construction and to re-roofing in mapped zones.
Chapter 7A does more than name a roof class. It also governs the edges and openings where embers actually get in:
- Class A roof covering or assembly is mandatory, with no exception for wood shake.
- Roof valleys must have a listed valley flashing (typically a corrosion-resistant metal at least 0.019 inches thick) under the covering.
- Roof-to-wall and edge gaps must be blocked so embers cannot enter the space between the covering and the deck.
- Vents must resist ember and flame intrusion, generally meaning corrosion-resistant mesh no larger than 1/8 inch.
Re-roofing usually triggers the current standard for the work you touch, so replacing a roof in a mapped zone means bringing the covering up to Class A even if the old roof predated the rule. Requirements vary by state and local jurisdiction, and some counties adopt amendments stricter than the state baseline, so confirm the rule with your local building department before you buy material. For context on how much of the national housing stock still carries older, lower-rated roofs, see our US housing stock roof age and material report.
Does a fire resistant roof cost more?
Choosing a Class A roof rarely adds cost, because the most common material, fiberglass asphalt shingle, is already Class A at standard pricing. Cost climbs only when you move to premium non-combustible coverings like clay tile, concrete tile, or metal, which are chosen for longevity and looks as much as for fire. The rating itself is not a line-item upcharge on asphalt.
Where wildfire compliance does add money is in the by-assembly details and the ember-blocking work: a rated cap sheet under a composite or metal roof, ember-resistant vents, and sealing tile ends. These are typically hundreds of dollars, not thousands, on a re-roof, and far cheaper than losing the assembly rating. Prices vary by region, roof size, and pitch, so treat any single figure as a starting point rather than a quote.
Reviewed by The Roofing Brief Team. Last reviewed July 2026.