Why long, heavy Northwest rainstorms find the weak spots in a roof, where leaks usually start and how to get your roof ready before the next big storm.
Why long storms find weak spots
Seattle is known for drizzle, but the storms that cause the most roof leaks are the long, heavy ones. Atmospheric rivers are narrow bands of moisture that carry warm, wet air from the Pacific to the West Coast, often in fall and winter. When one stalls over Puget Sound, it can rain hard for a day or more.
A roof that handles a light shower fine can start leaking when water keeps pouring onto it for hours, especially with wind behind it. Small weak spots that stayed dry all summer suddenly have enough water to find their way in.
Where leaks usually start
- Clogged gutters and downspouts: needles, leaves and moss block the flow, water backs up at the eaves and can run under the roof edge and into the walls.
- Flashing: the metal around chimneys, skylights, walls and vents is the most common leak source. Old sealant cracks and lets water in.
- Pipe boots and vents: rubber collars around plumbing vents crack with age and send water straight down the pipe.
- Valleys: where two slopes meet, a lot of water flows. Debris in a valley makes water spill sideways under the shingles.
- Wind-driven rain: strong gusts push water sideways and even uphill under lifted or loose shingles.
- Worn shingles and underlayment: on an older roof, the layers that keep water out simply wear thin.
Leaks that aren’t really leaks
Not every wet spot comes from outside. Warm, moist air from bathrooms, kitchens and dryers can condense on the cold underside of the roof in winter, especially if fans vent into the attic or the attic is poorly ventilated. The result looks like a leak: damp insulation, stains on the ceiling or dripping nails.
If wet spots show up when it hasn’t rained, or only on cold mornings, condensation may be the cause. The fix is better ventilation, not new shingles.
Get your roof ready before storm season
- Clean gutters and downspouts in fall, and again after the leaves and needles drop.
- Make sure downspouts carry water away from the foundation.
- Clear needles, leaves and moss from the roof and valleys.
- Look for missing or lifted shingles and cracked pipe boots from the ground or with binoculars.
- Check the attic with a flashlight after the first big rain for stains or damp wood.
- Trim branches that hang over the roof.
Don’t climb on a wet roof. If you can’t see well from the ground, a professional inspection is safer.
If your roof leaks during a storm
- Move furniture and valuables away from the leak and catch the water.
- Take photos of the damage inside and out for your records.
- Call a roofer about emergency tarping to stop more water getting in.
- Once the rain stops, have the leak traced to its real source, not just patched where it dripped.
Water travels along rafters and decking before it drips, so the stain on your ceiling is often far from the spot where water gets in. Our roof repair page explains how we trace leaks properly.
Get an honest answer
If heavy rain found a weak spot in your roof, we will find the source, show you photos and tell you whether it needs a simple repair or something bigger.
Book a free roof inspection or call (737) 307-1960.
