Do skylights leak often?
Short answer. Not when they are installed correctly with the manufacturer's flashing kit; a modern skylight is about as leak resistant as any other roof penetration. Skylights earn their leaky reputation from shortcut installs, old units with failing seals, debris piled on the uphill side, and condensation that drips like a leak.
Why skylights leak when they do
- Installation shortcuts. Caulk or roofing cement instead of a proper step flashing kit, flashing reused during a reroof, or a curb with no underlayment wrap. These usually show up within a few years.
- Aging seals and gaskets. Glass seals, frame gaskets and glazing seals dry out in the sun. Fogging between panes means the glass seal has failed, even if no water is coming in yet.
- Debris on the uphill side. Pine needles and leaves collect behind the skylight, hold water against the head flashing and push it sideways. This is a common Georgia problem under pines and oaks.
- Cracked domes. Old acrylic bubble skylights yellow, turn brittle and crack, especially after hail.
Leak or condensation?
Water that appears on cold mornings, in winter, or after long showers without any rain is probably condensation from warm, humid indoor air meeting cold glass. Water that appears only during rain, especially wind-driven rain from one direction, is a leak. Streaks on the drywall shaft below the frame point to flashing; drips from the glass edge point to seals.
Keeping one dry
- Clear debris from the uphill side a couple of times a year, from a safe position or with a professional.
- Replace the flashing kit every time the roof is replaced, and consider replacing a skylight approaching 20 years old at the same time.
- Run bath fans and keep indoor humidity in check to cut condensation.
See replacing skylights with the roof and common roof leak causes.