1. Flashing failures (the champion)
Flashing is the metal that seals every place your roof meets something else: chimneys, walls, valleys, skylights. When it cracks, rusts, or pulls away, water has a straight path in. If we had to bet sight-unseen on any leak in the metro, we'd bet flashing. (The full flashing breakdown.)
2. Worn pipe boots
Every plumbing vent pipe through your roof wears a rubber boot. Oregon sun and weather dry that rubber out in 10 to 15 years, and when it cracks, water follows the pipe straight down into the house. Cheap part, classic leak, easy fix when caught early.
3. Missing or wind-lifted shingles
Our winter windstorms peel shingles up or off entirely, and the exposed underlayment only holds out so long. If you've found shingle pieces in the yard, the roof is telling you where to look.
4. Skylights
We love skylights. Water loves them more. Debris collects on the uphill side, seals age, and the flashing around them works loose. They earn their own guide: why skylights need extra attention.
5. Clogged valleys and standing water
Valleys carry more water than anywhere else on the roof, and under Oregon trees they collect needles until water dams up and starts probing the seams. (How standing water kills shingles quietly.)
6. Moss-lifted shingle edges
Moss grows into the gaps between shingles and pries the edges up, breaking their seal. Then a wind-driven storm finds the opening. If your leak is on a green, shaded slope, moss probably set the table. (The Moss Handbook covers it all.)
7. Nail pops
Roofing nails can work their way up over years of temperature swings, lifting a little tent in the shingle above. Each one is a pinhole opportunity for water. One nail pop is trivial; a roof full of them says the install was rushed, and that's worth a professional look.
8. Ridge caps and aging seals
The cap shingles along the ridge take the most wind on the roof, and the various sealants up there have shorter lives than the shingles themselves. On roofs past 15 years, tired caps and seals make the list.
Notice a theme: almost everything on this list is a seam, an edge, or a penetration. Shingle field leaks are rare; interruption leaks are the rule. That's where any good leak hunt starts, and it's where our free assessments look first. For the whole journey from drip to fix, start with the Roof Leak Guide.