Fire-Resistant Roofing for Oregon Homes: How the Materials Compare

Which roofing materials actually earn Class A in Oregon?

Class A is a rating for a roof assembly, tested under ASTM E108 (the same method as UL 790), and it describes how the covering, the underlayment, and the deck behave together under a spreading flame, a burning brand, and an intermittent flame. No shingle of any material is Class A by itself. That distinction matters in Oregon because the SB 762 wildfire hazard map and the home-hardening rules that follow it are written around the assembly, and a building official in Jackson County or Deschutes County is going to ask for the listing, not the brochure. Four material families reach Class A in ways a Willamette Valley or east-side homeowner can actually buy. Concrete and clay tile do it through mass and non-combustibility. Steel panels do it as non-combustible sheet over a rated underlayment. Fiberglass-mat asphalt shingles do it because the glass mat and mineral surface slow flame spread enough to pass with a rated cap sheet beneath. Interlocking aluminum shingles and standing seam do it as a documented assembly, with GAF VersaShield fire barrier under the panels per ICC-ES ESR-2053.

Is tile or steel the safer choice for a wildfire-zone home in Oregon?

Concrete and clay tile are non-combustible, and a tile field does not ignite under an ember shower. The problem is what is underneath. Tile is by far the heaviest covering discussed here, and most of Oregon's housing stock, the Portland foursquares and Craftsman bungalows, the mid-century ranches in Salem and Eugene, the farmhouses across the Willamette Valley, was framed for a single layer of composition shingle. Many of those roofs already carry a second asphalt layer. Putting tile on that framing means a structural review, often sistered rafters, and a full tear-off. Tile also has an ember problem of its own: the channels under barrel and S-profile tile are open at the eave and the ridge unless they are bird-stopped and mortared, and those channels are exactly where wind-driven embers lodge against the underlayment. Steel is light and non-combustible and makes a straightforward Class A assembly. On the east side, in Wasco County or around Bend where salt is not an issue, it performs well for fire. West of the Cascades it brings the usual steel trade-offs: exposed-fastener panels open up over freeze-thaw cycles, and any cut edge or scratch that reaches the base metal starts to rust, which matters more in the 58 inches of rain Multnomah and Clackamas counties see than in the 18 inches at The Dalles. Steel warranties commonly restrict coastal exposure, so a steel Class A roof is a reasonable answer in the Cascade foothills and a poor one in Lincoln County.

Does a Class A asphalt roof hold up in Oregon's climate?

A fiberglass-mat asphalt shingle with a Class A underlayment is a legitimate Class A assembly, and it is the least expensive way to satisfy SB 762 hardening requirements on paper. The shortfall in Oregon is not the fire test. It is that west of the Cascades, moss is the roof-killer, and moss is hardest on asphalt. Benton County averages 60 inches of rain and Lane County 56, and the north slope of a roof in Corvallis or Eugene stays damp from October into May. Moss roots between the granules, lifts the tab edges, and holds water against the mat. A Class A asphalt roof that should have gone 25 years is often being pressure-washed and treated every few seasons and replaced somewhere past year 15. That shortened life has a fire dimension that is easy to miss. A moss-lifted asphalt roof has raised tab edges, cracked granule surfaces, and debris trapped in the gaps, and that is precisely the surface an ember wants to land on. The assembly was Class A when it was new. Ten wet winters later, with the granule surface eroded and needles packed against every lifted edge, it does not behave like the roof that passed the test.

Why is interlocking aluminum a Class A assembly without the tile weight?

Aluminum does not burn, and an interlocking aluminum shingle over GAF VersaShield fire barrier is a listed Class A assembly under ICC-ES ESR-2053. The reason this matters in Oregon rather than in the abstract is weight. An aluminum shingle roof weighs a small fraction of a tile roof, which is why it can be installed over existing framing without a structural upgrade and, where the code official allows it, over one existing asphalt layer. For the Portland bungalow with a second layer already on it, or the 1970s ranch in Beaverton with rafters that were never sized for masonry, aluminum is the Class A option that does not start with an engineer. The four-way interlock is the other half of the fire argument. Every panel is folded into the panels beside, above, and below it, so there is no free edge for an ember to slip under and no exposed fastener head for a gust to work loose. That is the same feature ESR-1790 documents at 177.5 psf of wind uplift. An ember that lands on an aluminum field has nothing to ignite and nowhere to lodge. Aluminum also contains no iron, so the same roof that satisfies a hardening inspector in Medford will not rust at Cloverdale or Warren, where documented installs went in with 81 and 59 inches of annual rain respectively. The awkward parts are real. Aluminum can dent under a dropped tool or a heavy limb, though the shingle profiles carry UL 2218 Class 4 impact certification. Standing seam can show oil-canning on wide flat runs in low sun. The cost is higher up front than a Class A asphalt roof. What you get for that is a 50+ year covering with a lifetime warranty that does not need a moss treatment cycle to keep its fire performance, and 374 roofs on record in Portland since 1998 to look at before you decide.

Where in Oregon does the roofing material actually decide the outcome?

Cedar shake belongs at the bottom of any Oregon fire comparison, and that needs saying plainly because shake is still common on coastal shingle-style homes and older foothill houses. Shake ignites from embers, burns on its own, and throws new embers downwind. Fire-retardant treatments wear out with weather, and 40 to 80 inches of winter rain washes them out faster here than almost anywhere. Inside an SB 762 high-hazard zone, replacing a shake roof is the single most effective hardening step available, and in the valley it is failing to moss regardless. The places where this choice carries weight are not evenly spread. The Rogue Valley around Medford, Ashland, and Grants Pass sits in dry summer air with grass and oak fuel on every slope. The east side from The Dalles through Bend has 18 to 22 inches of rain and a long ember season. The Cascade foothills above Molalla, Silverton, Eugene, and Oregon City are where valley subdivisions meet timber. The Columbia Gorge adds sustained wind that carries embers miles ahead of a fire front, which is why the roof at Hood River, with 76 inches of snow and 55 freeze-thaw days on top of the fire exposure, needs a covering that handles all three at once. Ember entry deserves the last word because it is how most Oregon homes are actually lost. Roofs seldom ignite from a wall of flame; they ignite when embers pile up in a gutter full of fir needles, in the open end of a tile channel, under a lifted asphalt tab, or through an unscreened attic vent. A Class A covering is necessary but not sufficient. Keep the gutters and valleys clean, use metal drip edge and flashing, fit ember-resistant vent screens, and choose a covering that gives an ember no gap, no fuel, and no fastener to lift. On an interlocked aluminum roof, most of that last requirement is built into the panel.

Common questions