How Long Does a Metal Shake Roof Last in Oregon Compared to Real Cedar?

How long does real cedar shake actually last west of the Cascades?

The lifespan figures printed on cedar shake brochures come from dry climates. In Oregon west of the Cascades, a cedar shake roof is doing well to reach 15 to 25 years, and the ones we tear off in Multnomah and Clackamas counties are usually at the low end of that range. The reason is not storms. Those two counties average about 58 inches of rain a year, and most of it falls between October and May, which means a north-facing shake roof in Southwest Portland or Lake Oswego stays damp for seven or eight months straight. Wood that never fully dries rots from the butt edge back. Moss makes it worse. Cedar is a softwood with an open grain, and moss roots into the surface, holds water against it, and pries the shakes apart as it thickens. Benton County sits at about 60 inches of rain and Lane at 56, so the same pattern shows up on shake roofs in Corvallis and the Eugene hills. Homeowners in those neighborhoods know the cycle: wash, treat, replace a few split pieces, and repeat every few seasons until the roof is more patch than shake. East of the mountains the story is different. Wasco County gets around 18 inches of rain, and a cedar roof in The Dalles dries out between storms. It still splits and cups with 48 freeze-thaw days a year, but it does not rot at the same pace. If you are reading a national number like 20 to 30 years for cedar, that is where it comes from, not from the Willamette Valley.

How long does an aluminum shake roof last in Oregon's climate?

An interlocking aluminum shake roof is rated for a 50+ year service life and carries the Guardian Lifetime Limited Material Warranty, which covers the original owner for life and transfers once to a second owner for 50 years from substantial completion. Those are the defensible numbers. What makes them hold up in Oregon specifically is that the failure modes that shorten cedar do not apply to aluminum. It contains no iron, so it cannot rust, which matters in Tillamook, Clatsop, and Lincoln counties where salt air corrodes exposed steel fasteners. It does not absorb water, so the 58-inch Portland winter has nothing to soak into. And moss, which is the actual roof-killer on this side of the state, has no grain to root into on a factory-finished panel. The finish is the other half of the lifespan question. Interlock panels use a 70% PVDF coating (Alunar, meeting AAMA 2605) with its own 30-year finish warranty, so a Deep Charcoal or black roof in the Cascade foothills keeps its color through decades of UV rather than graying and checking the way cedar does by year eight. The four-sided interlock has no free edge for a Columbia Gorge gust to lift, and ICC-ES ESR-1790 documents uplift resistance to 177.5 psf. The honest caveat is that aluminum is a softer metal than steel. A dropped tool or a heavy limb off a Douglas fir can dent it, and while UL 2218 Class 4 impact testing covers hail to 1.5-inch stones under the warranty, a dent is cosmetic rather than a leak. On a shake profile the embossed texture hides that far better than a flat panel would.

Which Oregon neighborhoods still have cedar shake, and what are they replacing it with?

Cedar shake was the roof of choice for a specific generation of Oregon housing. Lake Oswego's lakefront and Forest Highlands homes from the 1970s and 1980s, the West Hills above Portland, the wooded lots along the Clackamas River, and the Cascade foothill neighborhoods around Sandy, Estacada and Silverton were built under big conifers with shake roofs that matched the setting. Those same trees are why the roofs are failing. Heavy shade, needle load, and constant drip keep the shakes wet, and many of them are now on their second or third cedar roof. When those homeowners look at metal shake, the question is usually whether it will look right on a wooded lot. The aluminum shake profile is embossed with a split-grain texture and comes in the darker CRRC-rated colors that read as weathered wood from the street. Interlock has 19 roofs on record in Lake Oswego since 1999 and 374 in Portland since 1998, and a good share of the West Hills work replaced shake or was chosen because the owner wanted to keep that look without the maintenance. The most recent documented shake-look install is on the coast rather than in the hills: 34 squares of Deep Charcoal cedar shingle profile in Cloverdale, Tillamook County, completed April 2026. Tillamook averages 81 inches of rain and gusts to 85 mph, which is the hardest test in the state for a wood roof and a reasonable proof point for an aluminum one.

Does cedar shake create a wildfire problem under Oregon's SB 762 rules?

Oregon's SB 762 wildfire hazard map and the home-hardening rules that follow it apply mainly to the east side, the south, and the wildland edge, but the wildland edge runs closer to the Portland metro than most people assume. Homes on the forested slopes of the West Hills, in the Cascade foothills, and along the Columbia Gorge sit in exactly the kind of interface the map is concerned with. A cedar shake roof in those areas is a combustible surface that catches embers, and insurers have noticed. Many carriers now surcharge untreated shake, require it to be treated, or decline to write it in mapped hazard zones. Aluminum is non-combustible. On its own that is a big improvement over wood, and where the code or the carrier asks for a Class A rating, the answer is a Class A fire-rated assembly built with the aluminum shake over a GAF VersaShield underlayment, tested to ASTM E108 and documented under ICC-ES ESR-2053. The rating belongs to the assembly, not to the shingle by itself, and any installer who tells you the panel alone is Class A is overstating it. The practical point is that you get the fire class without the weight of concrete tile, which matters on older shake-era framing that was never sized for tile. A UL 2218 Class 4 impact rating may also earn an impact-resistant credit with some carriers. Ask your carrier before counting on it. The wildfire and insurance picture is one of the main reasons shake owners in Hood River and Wasco counties are moving to metal even before their cedar has fully worn out.

What does the maintenance difference look like year to year?

A cedar shake roof in the Willamette Valley is a maintenance schedule, not a one-time purchase. Every two to four years it needs a low-pressure wash to strip moss, a treatment to slow regrowth, and a walk-through to replace split or cupped pieces. Skipping a cycle in a 52-inch Marion County winter costs you years off the roof, because moss that gets a foothold in year ten will have lifted the shakes by year fourteen. Gutter cleaning happens more often too, since shake sheds fibers and hosts more debris than a smooth surface. An aluminum shake roof asks for almost none of that. There is nothing to treat or seal, no exposed fasteners with rubber washers to inspect, and moss does not root into a PVDF finish. What we do recommend is clearing needle load off north slopes and valleys once a year on heavily treed lots in Lake Oswego or the foothills, and checking flashings at chimneys and skylights every few years the way you would on any roof. That is the whole list. The roof is virtually maintenance-free, which is different from saying it needs nothing at all. Over a 50-year span, that difference compounds. A cedar shake homeowner west of the Cascades will typically install two or three roofs and pay for a dozen wash-and-treat cycles in the time one aluminum shake roof serves. That is the lifespan comparison that actually matters in Oregon, and it is the basis for the Never Re-Roof Again.® position. Interlock Metal Roofing (PNW) Inc. is Oregon's authorized Interlock installer, licensed under CCB #130826, and has been putting these roofs on Pacific Northwest homes since 1997.

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