By The Roofing Brief Team. Last reviewed: October 2026.
A class A fire rated roof is a roof covering or assembly that passed the severe-exposure level of ASTM E108 (equivalent to UL 790), the highest of three classes, and it is the rating wildfire areas require. Class A means the covering limits 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, which is why the E108 test is built around a burning brand: per the Intertek summary of ASTM E108, the Class A brand is 12 by 12 by 2 1/4 inches, the test blower simulates a 12 mile per hour wind, and the burner runs at 1400°F ± 50°F for Class A and B.
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 fire coming from above, meaning airborne embers and radiant heat from a nearby structure or vegetation: the Intertek summary of ASTM E108 describes E108 as simulating a fire that starts outside the building, with wind. It does not measure fire coming from inside the attic, which is a separate concern for the ceiling and deck assembly.
Ratings apply to a tested product or to a tested assembly, so 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 | One brand, 12 by 12 by 2 1/4 inches | Wildfire zones, WUI code, most jurisdictions |
| Class B | Moderate | Two brands, 6 by 6 by 2 1/4 inches each | Limited use, some commercial |
| Class C | Light | Small brand, 1 1/2 by 1 1/2 by 25/32 inch | 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 brand covers 144 square inches against about 2 1/4 square inches for the Class C brand (dimensions from the Intertek E108 summary), and the burner is set 100°F hotter for Class A and B (1400°F versus 1300°F). Wildfire codes name Class A for that reason.
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.
The rain and weathering tests apply only when the covering relies on fire-retardant treatment, because a retardant that washes out in the first storm is worthless (Intertek E108 summary). When you see “Class A by assembly,” the full tested build, covering plus underlayment plus deck, passed these 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 |
If the installer skips the cap sheet or barrier named in a by-assembly listing, the finished roof is not the tested Class A assembly and can fail inspection. Get the exact underlayment spec from the manufacturer’s listing before you order. Brava, for example, is Class C on its own and Class A only over a rated underlayment, per our Euroshield review comparison table.
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 or C, by product | By assembly (cap sheet) or none | Euroshield is Class C (QAI CERus-1013); Brava is Class A only over a rated underlayment |
| 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.
A Class A rating covers the roof covering, not the openings around it: open eaves, unscreened vents, and the space under the first course of barrel tiles are where embers can reach combustible battens and underlayment, so those details are specified separately.
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.
The same product-versus-assembly logic applies to wind uplift in our best roof for hurricane zones guide.
WUI roof requirements in 2026, including California’s new WUI Code
Homes in a mapped wildland-urban interface (WUI) or fire hazard severity zone must use a Class A roof assembly under wildfire building codes. Nationally, the model rule is the International Wildland-Urban Interface Code (IWUIC). In California, the wildfire construction rules that used to sit in California Building Code Chapter 7A and California Residential Code Section R337 were relocated into Chapter 5 of the 2025 California Wildland-Urban Interface Code (Title 24, Part 7), which took effect January 1, 2026, per the California Building Standards Commission’s State Fire Marshal rulemaking file; Section 504.2 covers the roof assembly. For permits under the 2025 code cycle, expect your building department to cite the WUI Code rather than Chapter 7A or R337. Re-roofing in a mapped zone can also bring the roof under these rules, depending on the scope of work and local amendments. Our guide to roof repair in Simi Valley shows how these rules play out on repairs in one California city.
California’s WUI Code, like the Chapter 7A rules it replaced, 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 adds no line item on fiberglass asphalt shingles, which are Class A as sold. Cost climbs when you move to clay tile, concrete tile, or metal, which are chosen for longevity and looks as much as for fire. For installed $/sq ft by material, use the roofing materials comparison rather than a single figure here.
Wildfire compliance adds scope in the by-assembly details and the ember-blocking work: a rated cap sheet under a composite or metal roof, 1/8-inch mesh vents, and sealed tile ends. Get these itemized in the written quote so the fire-rated assembly in the manufacturer listing is what gets built.
| If your roof is… | Then… |
|---|---|
| Fiberglass asphalt shingle in a WUI zone | Stand-alone Class A; add 1/8-inch mesh vents and blocked edge gaps |
| Metal or stone-coated steel | Class A by assembly; install the rated underlayment named in the listing |
| Recycled rubber such as Euroshield | Class C; not acceptable where Class A is required |
| Clay or concrete tile | Stand-alone Class A; bird-stop or seal the eave course |
| Untreated wood shake | Unrated; barred in most fire zones |
Frequently asked questions
Are asphalt shingles Class A fire rated?
Most modern asphalt shingles are Class A because they use a fiberglass mat, which earns the rating on its own without a special underlayment. Older organic-felt asphalt shingles were only Class C. If fire rating matters, confirm the shingle uses a fiberglass mat and check the manufacturer’s ASTM E108 or UL 790 listing for the specific product.
Is metal roofing Class A fire rated?
Metal roofing is non-combustible and can reach Class A, but usually only as an assembly, meaning it needs a rated underlayment or barrier beneath the panels to carry the full rating. The metal panel alone is not automatically a Class A roof. Ask the manufacturer for the tested assembly listing and install the specified underlayment to keep the rating valid.
What is the difference between Class A, B, and C roof ratings?
The classes describe how much external fire a roof covering resists. Class A withstands severe exposure and a large burning brand, Class B moderate exposure, and Class C only light exposure and a small brand. Untreated wood shake passes no test and is unrated. Wildfire and WUI codes require Class A because a wildfire lofts large embers a Class C roof cannot handle.
Does a Class A roof mean the whole assembly is fireproof?
No. Class A means the roof covering resists external fire under a defined test, not that the home is fireproof. Embers still enter through eave gaps, unscreened vents, and openings under barrel tiles. A Class A covering paired with ember-resistant vents, sealed tile ends, and blocked edges is what actually protects a home in a wildfire, not the covering class alone.
Is wood shake allowed in wildfire areas?
Untreated wood shake is barred from most wildland-urban interface and fire hazard severity zones because it earns no fire rating. Fire-retardant-treated wood shakes can reach Class A or B, but only as a listed, pressure-impregnated product installed in a rated assembly. Check your local building department, since many fire-prone jurisdictions prohibit wood roofing entirely regardless of treatment.
Do I have to upgrade my roof to Class A when I re-roof in a fire zone?
In mapped wildfire zones, re-roofing generally triggers the current standard for the work you perform, so the new covering must meet Class A even if the old roof did not. In California, the wildfire roof rules formerly in Chapter 7A and R337 now sit in the 2025 California Wildland-Urban Interface Code (Title 24, Part 7) for permits from January 1, 2026. Rules vary by state and county, so confirm the requirement with your local building department before buying material.