How do you fix a leaking skylight?
Short answer. Fix a skylight leak by first pinning down the source: clear debris from the uphill side, check the flashing and the shingles around the unit, look for failed glass seals or gaskets, and rule out condensation. Flashing leaks are fixed by replacing the flashing kit along with the shingles around it, seal and gasket leaks by resealing or replacing the unit, and condensation by controlling indoor humidity.
Find the source first
- Only during rain, at the top corners or down the shaft: flashing, especially at the head where debris collects.
- From the glass edge or frame: glass seals, glazing gaskets, or a cracked dome.
- On cold mornings or after showers, with no rain: condensation.
- Only on venting units: the sash seal, or a unit left partly open; check the rain sensor.
A gentle hose test, starting below the skylight and working up the sides to the head with a helper inside, confirms a flashing leak.
The fixes
- Debris dam: clear needles and leaves from the uphill side and check for rust or damage beneath.
- Flashing: remove the surrounding shingles, install the manufacturer's flashing kit for that unit with its underlayment collar, and reshingle. Caulking the joints is a short-term patch at best.
- Seals and gaskets: some units allow replacement of exterior gaskets; fogged insulated glass means the glass or the unit needs replacing.
- Cracked dome: replace the dome or the unit.
- Condensation: run bath and kitchen fans, keep indoor humidity in check, and make sure the shaft is insulated.
Repair or replace?
If the skylight is near 20 years old, fogged or leaking at the frame, replacing it, ideally with the roof, beats chasing leaks. Dry out wet drywall in the shaft quickly, since Georgia humidity encourages mold. See replacing skylights with the roof and common roof leak causes, and Robust Roofing's guide to telling a skylight leak from a roof leak.