Class A is the highest roof fire classification under ASTM E108 and UL 790, and it is what Colorado's wildfire code requires in mapped areas. The distinction that trips people up is stand-alone versus by-assembly: some materials pass on their own over a standard deck, while others only earn Class A when installed with specific listed components. For code compliance, the complete assembly as installed is what counts.
What the test measures
ASTM E108 and UL 790 are the same fire test. Roofing gets exposed to a spread-of-flame test, a burning-brand (ember) test and an intermittent-flame test. The class reflects how severe an exposure the roof survived, and no passing test allows fire to penetrate the roof deck.
- Class A: effective against severe fire exposure, flame spread of no more than 6 feet, high degree of protection to the deck, no slippage, no flying-brand hazard. This is the code requirement.
- Class B: effective against moderate exposure, flame spread up to 8 feet.
- Class C: effective against light exposure, flame spread up to 13 feet.
Stand-alone Class A
A stand-alone Class A material passes the test on its own over a standard deck. Modern asphalt fiberglass-mat shingles, concrete and clay tile, natural slate and fibrous cement products fall in this group. Older organic-mat asphalt shingles rated Class C and have essentially left the market.
Class A by assembly
A by-assembly material only earns the rating when installed with the additional components named in its test report, such as a 72-pound mineral-surfaced cap sheet, Type X gypsum board or a specific fire-rated underlayment. Most metal roofing, including steel, aluminum and stone-coated steel, is Class A by assembly, as are fire-retardant-treated wood shakes.
This is where compliance fails quietly. A steel panel over a bare wood deck with ordinary felt may only rate Class C, because heat conducts through thin metal and can ignite the deck. A Class A shingle installed over a non-compliant assembly does not automatically produce a compliant Class A roof either. Match the installed stack-up to the manufacturer's listed assembly, and keep the paperwork.
The ember-space rule
Where the covering profile creates a space between covering and deck, which happens with tile, some metal panels and wood-look products, Section 403.2.1 requires that space to resist flame and ember entry. There are three compliant paths: firestop the space with noncombustible material, install one layer of ASTM D3909 cap sheet over the combustible deck, or install a listed Class A classified roof assembly.
Documentation is part of the job
Your insurer, and eventually a buyer's inspector, will want proof of what is on the roof. Keep the product listing, the assembly documentation and the permit and inspection records together. We hand that package over at the end of every wildfire-area project because it is what turns a good roof into a documented mitigation credit.
Two misconceptions worth correcting
First, "any asphalt shingle is automatically Class A" is mostly true for modern fiberglass shingles but not a rule you can lean on, because compliance is about the whole assembly as installed and by-assembly materials such as metal need the correct underlayment.
Second, "a Class A roof makes my home fire-safe" is false. The covering is necessary and not sufficient. Ember intrusion through vents, debris igniting in gutters and combustible material in the first 5 feet are the dominant ignition pathways. The honest framing used by IBHS and fire agencies is home hardening, not fireproofing.
Requirements vary by jurisdiction
Colorado's wildfire code is a state minimum, but adoption and enforcement happen locally, and adoption is uneven. Some counties, towns and fire districts adopted the code, some adopted amended or more stringent versions, and some declined. Nothing on this page tells you what applies to your specific address. We confirm the current adopted code and map with your building department before every project in a wildfire area, and we put the answer in writing with the estimate.
Common questions
- Is my asphalt shingle roof Class A?
- Virtually all modern fiberglass-mat asphalt shingles carry a stand-alone Class A rating, so most recent asphalt roofs qualify on the covering. Compliance still depends on the installed assembly, so verify the specific product listing rather than assuming.
- Are metal roofs Class A?
- Metal roofing is usually Class A by assembly, not stand-alone. It needs the listed fire-rated underlayment or barrier from the test report. Steel over a bare deck with ordinary felt can rate as low as Class C.
- What is the difference between Class A, B and C roofs?
- They describe how severe a fire exposure the roof survived in the ASTM E108 or UL 790 test. Class A withstands severe exposure with flame spread of no more than 6 feet, Class B moderate exposure up to 8 feet, and Class C light exposure up to 13 feet.
Talk to us about your roof
We work out of 9822 Titan Park Cir, Littleton, and cover the Front Range foothills where this code matters most. Call (303) 738-1032 or book an inspection and we will confirm the local requirements, walk the roof, and put the 25% answer in writing with your estimate. Our neighborhood guides and service areas show where we work, and the insurance claim guide covers the documentation side.