Metal roofing and fire: the ratings, explained

Two tests, one rating system

Roof fire classification runs on a Class A, B, or C scale, based on two largely equivalent test standards, ASTM E108 and UL 790, each involving a flame-spread test and a burning-brand test. Class A is the most fire-resistant rating on that scale, Class C the least.^[1]

The deck matters as much as the panel

A metal panel installed over a noncombustible deck, such as steel or concrete, or directly over noncombustible framing with no deck at all, is treated as Class A without additional testing. Install the same panel over a combustible wood deck, though, and the full assembly, not just the metal, has to be tested and listed together under ASTM E108 or UL 790.^[1]

A narrow exception worth knowing

Heavy-gauge copper, at 16 ounces per square foot or thicker, is treated as Class A over a combustible deck without separate testing, an exception most other metal roofing materials don't get.^[1]

What the code actually requires

It's a common assumption that every roof needs a Class A rating, but the building code doesn't universally require one for every type of construction; a Class A requirement typically shows up in wildfire-prone areas specifically, rather than as a blanket nationwide rule.^[1]

What to ask your installer

Ask for the specific tested assembly your installer is proposing, not just the panel's own rating in isolation. A UL-listed assembly ties its fire rating to every layer in the system, deck, underlayment, and panel together, so swapping one component for an untested alternative can void the rating even if the metal itself is unchanged.^[1]

Fire rating and wildfire risk are related, not identical

A Class A roof assembly is one piece of wildfire hardening, alongside ember-resistant vents, noncombustible siding near the ground, and cleared vegetation close to the structure. A homeowner in a wildfire-prone area is generally better served thinking through the whole assembly of defenses than treating the roof rating as a complete answer by itself.

Where insurance sometimes enters the picture

Some insurers in wildfire-prone areas ask about roofing material and rating as part of underwriting a policy. Confirming your specific assembly's rating with documentation, rather than just describing the roof as metal, is worth having ready if that question comes up, since "metal roof" alone doesn't specify which fire class the finished assembly actually earned on paper.

Questions people ask

Does metal roofing material itself resist fire better than shingles?

The metal itself doesn't burn, but the assembly's rating depends on the deck and underlayment beneath it too, so the panel alone isn't a complete fire-safety answer.^[1]

Is a Class A rating required where I live?

It depends on your local jurisdiction and wildfire exposure; ask your local building department directly rather than assuming either way.^[1]

Can I swap in a cheaper underlayment if the panel is already Class A rated?

Not without checking the listed assembly; the rating applies to the tested combination of deck, underlayment, and panel together, so an untested substitution can void it.^[1]

Does a metal roof lower my fire insurance premium?

Some insurers factor roofing material and rating into wildfire-related pricing, but the effect varies by carrier and location, so ask your own insurer directly rather than assuming a fixed discount.

Does the color or finish of a metal roof affect its fire rating?

No; fire classification is about the assembly's structural and material makeup, not its paint color or finish, which instead relate to heat reflectivity and appearance rather than flame resistance in a wildfire scenario.