Signs You Need a New Roof in Oregon: What to Look for Each Season

What are the signs you need a new roof in Oregon?

Oregon west of the Cascades has a different killer, and it is moss. Multnomah and Clackamas counties take roughly 58 inches of rain a year, most of it between October and May. A north-facing slope in Portland or Eugene never really dries in those months, and moss roots down between the asphalt granules, wicks water under the tab, and slowly pries it up. Once you can slide a finger under a tab because a moss mat is holding it open, that shingle is no longer shedding water. The second Oregon sign is what comes out of the gutters after winter. The 36 freeze-thaw days Multnomah averages, or the 39 in Marion County around Salem, loosen the granule bond. When you clean the downspout in March and find a cup of black grit, that is the wear surface of your roof washing away. Bald spots follow, and bald asphalt cracks in the first hot week of July. The third sign gets missed because people assume a wet climate means no heat damage. Willamette Valley summers are dry, and afternoon sun on a south or west slope bakes shingles that spent eight months saturated. That wet-then-cooked cycle is why tabs on a Beaverton or Hillsboro ranch curl at the corners by year fifteen even though the roof looked fine in May.

How do you know when cedar shake or coastal steel is going bad?

Cedar shake is common on older homes in Lake Oswego, Tigard, the West Hills and the Cascade foothills, and it fails differently from asphalt. Shake does not curl and shed granules; it goes soft. Push a thumb into a shake on the shaded north side and if it gives like a sponge, the wood has been holding water long enough to rot from the inside. Green algae film and moss cushions on the butt ends are the visible version of the same problem. By the time shake is green and soft on top, the felt underneath has usually been wet for years. On the coast the material to watch is steel. Clatsop County takes about 72 inches of rain with gusts to 91 mph, Tillamook about 81 inches, Lincoln County about 71, and all of it arrives with salt in it. Salt aerosol holds a damp film against the metal, and any exposed iron begins to oxidize. It shows first not in the middle of a panel but at the cut edge of a rake or valley and at the head of every exposed fastener. Brown streaks running downslope from a screw line on a Seaside or Newport roof mean the barrier has been breached and the steel underneath is rusting. Many steel roof warranties restrict oceanfront exposure for exactly this reason. Aluminum contains no iron and does not rust, which is why it is the metal we install on the coast. A documented 34-square Deep Charcoal cedar shingle install in Cloverdale, Tillamook County, in April 2026 replaced a roof that had reached exactly this stage.

What do Gorge wind and Hood River snow do to a roof?

Hood River, The Dalles and Cascade Locks sit in a wind funnel, and the west faces of a roof there take sustained wind the Willamette Valley only sees in a winter storm. On asphalt, the sign is tabs that have been lifted and folded back, sometimes creased so they no longer lie flat after the wind drops. Look along the west-facing slope after a strong east-wind event for tabs that are pale on the underside where the seal strip has torn loose. Once the seal strip fails, the next storm takes the tab entirely. Wasco County averages only about 18 inches of rain, so a Gorge roof can look dry and healthy from the driveway while the wind is quietly unzipping it. Four-way interlocked aluminum has no free edge for wind to catch, and ICC-ES ESR-1790 documents uplift resistance to 177.5 psf. That is what we put on the 13 documented roofs in Hood River since 1999. Snow is the other Gorge and Mt Hood foothills problem. Hood River County averages roughly 76 inches of snow and 55 freeze-thaw days a year. Snow melts over the heated attic, runs to the cold eave, refreezes, and the ice dam backs meltwater up under the shingles. The sign is a brown stain on the ceiling or the top of an exterior wall within a few feet of the eave, usually in February or March. Once you see those stains you will see them every heavy winter until the roof and its underlayment are dealt with together.

Is a sagging roofline on an older Portland house a sign you need a new roof?

Yes, and it should not wait for the next dry season. Portland's Craftsman bungalows, foursquares and Victorians from the 1900s through the 1920s were framed with rafters often spaced wide and sized for a single layer of wood shingle or early composition. A great many of these roofs now carry a second asphalt layer laid over the first. Each layer adds weight the framing was never sized for, and each layer traps the moisture from the one beneath it. Stand across the street and sight along the ridge. A ridge that dips in the middle, or a slope with a visible belly between rafters, means the deck or the rafters have deflected under the load. In the attic, the same problem shows as dark, punky sheathing you can push a screwdriver into, especially along the north eave where the roof has been damp for a century. The 19 inches of snow Multnomah can see in a bad winter is enough to turn a two-layer roof on softened framing into a structural question. A second layer also hides the sign you would otherwise catch. Curling on the top layer is visible, but the first layer underneath has been rotting quietly and the sheathing with it. Any replacement on a house of this age in Portland, Oregon City or Salem should plan on a full tear-off so the deck can be inspected and repaired first. Weight matters here too. Aluminum shingles are light enough that a 1910 foursquare can carry them without sistering the rafters, which is not true of concrete tile or slate.

What should you check on your Oregon roof after each season?

Oregon's roof year has four checkpoints and each exposes a different failure. When the fall rains start in October, walk the north side and look for moss returning in the shade and for needles packed in the valleys, since a valley that stays wet all winter is where the first leak usually starts. In March, clean the gutters and read what came out; heavy granule loss in Marion, Polk or Linn County, where freeze-thaw runs 37 to 40 days a year, tells you the shingles are near the end. In the Gorge and around Mt Hood, March is also when to look for ice-dam staining near the eaves. In September, check the south and west slopes for curled and cracked tabs and, on the coast, walk the rake edges and fastener rows for rust streaks the dry months have made easier to see. After any east-wind event in Hood River or The Dalles, look at the west face for lifted or missing tabs before the next rain drives water under them. When two or three of these signs appear in the same year on an asphalt roof older than fifteen years, or on cedar shake that has gone soft, the honest answer is replacement rather than another wash-and-treat or another handful of tabs. We have 374 roofs on record in Portland since 1998 and 64 in Eugene, and the oldest one still photographed in our gallery, a black aluminum slate in Eugene, shows none of these signs because interlocked aluminum gives moss nothing to root into, has no iron to rust and no free edge for wind. It is not cheap and it will dent under a dropped ladder like any thin metal, but it takes this seasonal checklist off your calendar.

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