Which Roof Holds Up to Columbia River Gorge Wind in Oregon?

Why does the Columbia River Gorge wreck roofs that last fine in Portland?

The Gorge is the only sea-level cut through the Cascades, and it works like a pressure valve between two climates. When the Willamette Valley is warm and the Columbia Plateau is cold, air pours west through the gap; when the pattern flips, it pours east. Either way the wind funnels through a corridor a few miles wide, which is why the same weather system that gives Portland a breezy afternoon gives Cascade Locks, Hood River, Mosier and The Dalles a full day of sustained wind with gusts on top. The county figures show the split. Hood River County averages 42 inches of rain, 76 inches of snow, 55 freeze-thaw days a year and recorded gusts to 68 mph. Wasco County, in the rain shadow, averages only 18 inches of rain and 22 inches of snow, 48 freeze-thaw days, and gusts to 52 mph. Those gust numbers are single-station ten-year figures, not the worst any ridge lot has seen, and homeowners on the exposed benches above Mosier or on the bluffs east of The Dalles will tell you the wind at their eave is stronger than the airport reading. What matters for a roof is not one peak gust but hours of sustained loading, day after day, in both directions. A roof in Beaverton might see a handful of strong wind events in a winter. A roof on the west edge of Hood River sees wind as a normal condition, and it also cycles through freeze and thaw 55 times a year on top of that. Fasteners work loose, sealants fatigue, and any edge that can flutter eventually does.

Why do tabbed asphalt shingles peel in a Gorge east-wind event?

A three-tab or laminated asphalt shingle has an exposed lower edge held down by a strip of factory adhesive and by nothing else. The nails sit higher up under the course above. When wind hits a roof it does not push the shingle flat; it creates negative pressure over the surface and, more important, it drives air under that exposed edge. Once the edge lifts even a quarter inch, the adhesive strip has already failed and the tab becomes a flap. The next gust bends it back over the nail line, the mat cracks at the fold, and the tab tears off or lets water in underneath. This is a free-edge failure, and it explains why shingle damage in the Gorge shows up first at rakes, eaves and ridges, on the west and east faces, and on older roofs where the seal strip has gone brittle. The 55 freeze-thaw days in Hood River County speed that up. Cold makes the adhesive stiff; sun and warm afternoons soften it; the cycle breaks the bond long before the shingle itself is worn out. Many Gorge roofs also carry a second layer of asphalt over the first, which gives the top layer a lumpier bed and more edges for wind to find. Shingle manufacturers do publish wind ratings, and some laminated products carry a 110 or 130 mph label when installed with extra nails and a specific starter strip. Those ratings assume the seal strip is fully bonded and the installation is exact. In practice, on a roof at Cascade Locks that sees sustained wind through most of the winter, the seal strip is the weak link and it is the part nobody inspects.

What does four-way interlock actually mean on a metal roof?

An interlocking aluminum shingle is folded along all four edges. The top edge and one side edge are fastened directly to the deck with nails or screws that are then covered by the next panel. The bottom edge and the other side edge hook under the folded edges of the neighboring panels. Every panel is therefore both fastened and locked, and no panel has an edge that faces the wind unsupported. To lift one shingle, the wind would have to lift the panel above it, the panel beside it, and the fasteners under both. That is the practical difference from a tabbed roof. There is no adhesive strip doing structural work, no exposed edge for air to get under, and no single fastener carrying the load. The panels are 3105-H24 or 3003-H24 aluminum, which is light enough that a Gorge roof gains no dead load and stiff enough that the folds hold their shape under repeated cycling. The same principle applies to the slate, shake, cedar shingle and tile profiles; only the surface pattern changes. It is fair to say what interlock does not do. It does not make the roof silent; wind across any metal roof, or any roof, makes noise, and aluminum over open framing without a solid deck can drum. It does not stop oil-canning on long flat standing seam panels in direct sun, which is cosmetic but visible. And it does not protect a house whose edge metal and underlayment are done badly, which is where the next two sections go.

How do uplift ratings, psf and a 120 mph warranty fit together?

Homeowners in Hood River and The Dalles ask for a roof rated to a wind speed, and the honest answer takes a minute. ICC-ES ESR-1790 is the evaluation report for the Interlock aluminum shingle system, reissued in September 2025. It documents wind uplift resistance to 177.5 pounds per square foot in the tested assembly. That is a pressure, not a wind speed. Converting pressure to miles per hour is not a straight arithmetic step; it depends on the building's height, the roof slope, the exposure category of the site, whether you are at a corner, an edge or the field of the roof, and the safety factors in the building code. The same 177.5 psf covers a far higher design wind at a sheltered valley lot than at an exposed bluff above Mosier. The Guardian Lifetime Limited Material Warranty is a separate document and it states a warranted wind resistance of 120 mph. That is the manufacturer standing behind the product in plain language a homeowner can hold them to, and it is deliberately more conservative than the test data. The two numbers are not a contradiction. One is what the assembly did in a laboratory under a controlled uplift test; the other is what the company will put its name on in the field, across every roof shape and every installer. For a Gorge homeowner the useful comparison is this: the highest ten-year gust on record in Hood River County is 68 mph and in Wasco County 52 mph. A 120 mph warranted roof carries real margin over that. The 177.5 psf test result is what a structural engineer or a county plans examiner will want to see, and it is the number that gets a permit through when the site is in a high exposure category.

What should a Gorge homeowner check before signing a roofing contract?

Start with the county. Both Hood River County and Wasco County issue roofing permits under the Oregon Residential Specialty Code, and the code assigns a wind exposure category to the site based on terrain and shelter. A home tucked in the trees at Cascade Locks and a home on an open bench above The Dalles are not the same exposure, and the fastening schedule should reflect that. Ask the contractor which exposure category they are designing to and whether the county will want the ESR on file. If the answer is a shrug, keep looking. Confirm the Oregon CCB license is active while you are at it. Next, look at the edges, because that is where Gorge roofs fail regardless of material. Ask what the drip edge and rake metal are, how they are fastened, and how the first course locks to them. On an interlocked aluminum roof the starter and edge trim are part of the wind system, not decoration. Ask for the fastening pattern in writing: fasteners per panel, fastener type, and whether the edge zones get more than the field. Ask what underlayment goes under the panels and whether the eaves get ice and water membrane, because 76 inches of snow and 55 freeze-thaw days in Hood River County mean ice dams are a real event, not a valley rumor. Finally, ask about the roof you are covering. Many Gorge homes have a second layer of asphalt that should come off, and a soft or delaminated deck will not hold fasteners no matter how good the panel above it is. There are 13 interlocked aluminum roofs on record in Hood River and 12 in The Dalles since 1999, so there are local roofs to look at and local owners to ask how they have done through a January east wind. Cost is higher than shingles up front, and the case for it here is not appearance; it is that the roof you put on in the Gorge should be the last one you fasten down.

Common questions