Why skylights leak more than the rest of the roof
Three reasons. First, debris: needles and leaves wash down the roof and pile against the skylight's uphill edge, holding a wet compress against the flashing for months. Second, seals: the gaskets and weather seals around the glass dry out and shrink over 10 to 20 years. Third, the flashing kit itself: it's doing the hardest flashing job on the roof, sealing all four sides of a box against water coming from above.
Oregon adds a fourth: moss loves the shaded, damp margin around a skylight curb.
Leak, or condensation?
Half the 'leaking' skylights we visit aren't leaking. Warm indoor air hits cold skylight glass, condenses, and drips, especially in winter, especially in kitchens and bathrooms. Condensation shows up in cold snaps regardless of rain, beads on the glass itself, and drips from the low corner of the skylight well.
An actual leak tracks with rain, often stains the drywall of the skylight well on one side, and leaves trails from the frame rather than the glass. Knowing which one you have changes the fix from 'roofer' to 'ventilation.'
Keeping skylights watertight
The maintenance is boring, which is the good news:
- Keep the uphill side clear of debris so water flows around, not against. (Part of every roof cleaning we do.)
- Treat moss around the curb before it gets under the flashing edges. (The Moss Handbook covers why.)
- Have the seals and flashing eyeballed during inspections, especially past year ten.
- When reroofing, replace the skylights or at least the flashing kits. Putting a 20-year-old skylight on a brand-new roof is a classic regret.
When a skylight leak shows up
Skylight repairs range from resealing and new flashing kits to full unit replacement, and the right answer depends on the unit's age and the leak's path. We'll tell you which one your situation actually needs, with photos. (Free assessment, as always.)
For tracking the leak to its source first, the Roof Leak Guide has the method.