Class A Fire-Rated Roofing in Oregon's Wildfire Zones

What does a Class A fire rating actually test?

Class A is the highest of three roof fire classifications (A, B, C) defined by ASTM E108 and its UL equivalent, UL 790. The test is not a test of a shingle. It is a test of a complete roof assembly built on a deck the way it would be installed on a house, and three separate exposures are run on it. The spread-of-flame test puts a gas flame at the low edge of a sloped sample under a steady wind and measures how far fire travels up the surface. The intermittent-flame test cycles the flame on and off to simulate a fire front passing and returning. The burning-brand test sets a wood crib on the surface and lets it burn down, checking whether anything ignites beneath the covering or falls through the deck. That last point is why the wording matters so much. Aluminum is non-combustible, and by itself it will not burn. But an aluminum panel does not earn a Class A rating by itself either, because the test asks what happens to the deck and the underlayment below the metal when a burning brand sits on a seam for the better part of an hour. Interlock's aluminum shingles, shakes, slate, tile and standing seam earn Class A as an assembly when installed over GAF VersaShield fire-barrier underlayment, and that assembly is what ICC-ES ESR-2053 documents. Anyone selling you "Class A shingles" is describing something the test does not measure. On a Hood River or Bend roof this distinction is not academic. A metal roof laid over the old asphalt without a fire-barrier underlayment may be non-combustible on top and still fail the burning-brand exposure underneath. The rating lives in the layers, and the layers have to be the ones that were tested.

Where in Oregon do the wildfire roofing rules apply?

Oregon's approach came out of Senate Bill 762, passed after the 2020 Labor Day fires that ran through the Santiam Canyon, the McKenzie corridor east of Eugene, and the Almeda fire between Ashland and Medford. The bill directed the state to produce a statewide wildfire hazard map and to adopt home-hardening construction standards, which now sit in section R327 of the Oregon Residential Specialty Code. Those standards apply to new construction and to certain roof replacements in the highest-hazard classification within the wildland-urban interface. Here is the part to be careful with. The map has been withdrawn, redrawn and re-released since its first version, and the rules for which parcels trigger R327 have been revised along with it. A property that was in the top class on one map may not be on the next, and the reverse is also true. Do not take a contractor's word, or this article's, for your parcel's status. The Oregon Department of Forestry publishes the current map, and your county building department is the office that decides whether a permit for your roof carries the R327 requirements. Ask both before signing anything. Geographically the exposure is not evenly spread. West of the Cascades in Multnomah and Clackamas counties, where the ten-year average is about 58 inches of rain, moss kills more roofs than fire ever will. Cross the mountains and the picture flips. Wasco County around The Dalles averages roughly 18 inches of rain a year, and the dry pine and juniper country from there south through Bend, Klamath Falls and the Rogue Valley is where a roof's fire performance matters most. The Cascade foothills above Eugene, Sweet Home and Estacada, and the Gorge towns of Hood River and Cascade Locks, sit at the edge where forest meets subdivision.

Does a Class A roof stop embers from getting into the attic?

Not by itself, and this is the honest limit of any roof covering. Most Oregon homes lost in 2020 were not consumed by a wall of flame reaching the eaves. They were lit by embers carried a mile or more ahead of the fire front, landing in gutters full of fir needles, blowing under lifted tile edges, or drawn through attic vents. A Class A rating tells you the surface will not carry fire and a burning brand on top will not burn through. It says nothing about what gets in at the edges. That is where a flat-lock aluminum shingle has a practical advantage over profiled tile. Concrete and clay tile are Class A on their own, but the rounded and S-shaped profiles leave open channels at the eave and ridge where embers lodge against the underlayment, which is why California-style bird stops and mortar fills exist. An interlocked aluminum shingle lies flat to the deck with a four-way mechanical lock on every edge. There is no channel under it, and no free edge for wind to lift and expose the felt. The rest of the hardening is at the openings and it is mostly inexpensive. Attic, soffit and gable vents should carry ember-resistant screening, typically an eighth-inch or finer mesh rather than the quarter-inch hardware cloth common on older ranches and Craftsman bungalows. Gutters should be metal, not vinyl, and kept clear through fire season. A Class A roof plus screened vents plus clean gutters is the combination that R327 is really describing, and a roofer working in Jackson or Deschutes County should be able to speak to all three.

Is aluminum a better choice than tile for a fire-rated roof in Oregon?

Both reach Class A. The difference is what they ask of the house. Concrete tile is among the heaviest coverings you can put on a roof, and clay is not far behind, so a home framed for asphalt in the 1960s or 1970s will usually need an engineer's review and often added rafters or purlins before tile can go on. That is real money before a single tile is set, and on a mid-century ranch in Medford or a two-story farmhouse outside Redmond it can decide the project. Interlock's aluminum shingles weigh less than the asphalt they replace and go onto the existing framing without reinforcement on nearly every home we see. Snow plays into this on the east side and in the foothills. Hood River County averages about 76 inches of snow and 55 freeze-thaw days a year, and tile carrying a snow load is tile the structure has to hold while also holding itself. Aluminum sheds snow, holds no moisture, and does not spall when water freezes in it the way clay and concrete can. It also does not crack when someone walks it to clean a chimney or clear a valley. The honest trade-offs run the other way too. Aluminum will dent under a dropped tool or large hail, though the UL 2218 Class 4 impact rating covers the sizes that reach Oregon. A dark standing seam panel on a long, low slope can show oil-canning in raking light. And a Class A aluminum assembly costs more up front than a Class A asphalt assembly, which is also available and which many homeowners in the hazard zones will choose. What the aluminum buys is a 50-plus-year service life and a lifetime warranty on a roof you do not expect to replace again, which is the arithmetic that has put 13 documented Interlock roofs on record in Hood River since 1999 and 12 in The Dalles.

What should I ask an Oregon installer to put in writing?

Start with the parcel. Ask the contractor to state in the proposal which wildfire hazard classification your county building department has on file for the address and whether the permit will be reviewed under R327. If they cannot tell you, find out yourself from the county before proceeding, because the requirement follows the permit, not the salesman. Then ask for the rating in the form the inspector will accept. That means the specific ICC-ES evaluation report for the Class A assembly, which for Interlock aluminum is ESR-2053, along with the underlayment it names, GAF VersaShield, listed as a line item on the contract rather than a substitute at the supplier's discretion. Ask for ESR-1790 as well, which documents the wind uplift performance of the interlocked panels to 177.5 psf and was reissued in September 2025. A proposal that says "Class A metal roof" with no report number is a proposal that has not committed to anything the inspector can check. Finally, confirm the licensing and the warranty terms. Every roofing contractor in the state must hold an active Oregon Construction Contractors Board license, and you can look up any number, including ours, CCB #130826, on the CCB website before a deposit changes hands. Ask for the manufacturer's warranty document, not a summary, and note what it requires of you: Interlock's Guardian Lifetime Limited Material Warranty is transferable once to a second owner if registered within 60 days. Insurance carriers in the Rogue Valley and Central Oregon are increasingly asking about roof class and impact rating at renewal, so keep the ESR reports with the closing paperwork and ask your carrier whether the Class 4 impact rating earns anything. Do not let anyone promise you that it will.

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