How often should you reseal a skylight?
Updated July 2026
Plan to refresh the flashing seal and check the gaskets on a skylight about every 10 years, and immediately if you spot the first brown stain on the light-well drywall. The skylight units themselves last 10–20 years, but the sealant and flashing that tie them into the roof age faster than the glass. A skylight sits at the wettest, most sun-baked spot on the roof, so its seals are the part that decides whether it leaks.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Curb-mounted with step flashing | Reseal every 8–12 years | The raised curb sheds water well but the flashing joints still age |
| Deck-mounted flashing kit | Every 10 years | Sits lower and flatter, so the perimeter seal works harder |
| Older acrylic bubble skylight | Every 5–8 years | Plastic domes yellow, craze, and lose their seal sooner than glass |
| Staining on the light-well drywall | Reseal or replace now | That stain is water already getting past the flashing |
| Re-roof in progress | Reflash at the same time | New flashing installed with new shingles is the durable, cheap moment |
The cost of skipping it
What skipping it costs: a skylight leak does not drip onto a floor you will notice, it runs down the light well into a finished ceiling, staining drywall ($500–2,000 to repair and repaint) and growing mold inside the shaft where you cannot see it. Let it run and you are replacing the skylight and the flashing together at $900–2,500 installed. A flashing kit and a resealing visit are far cheaper, and cheapest of all done during a re-roof.
How to do it (Roof work; hire a roofer unless you are comfortable up high)
- From inside, inspect the light-well drywall for brown stains, bubbling paint, or any musty smell after rain.
- From the roof (or with binoculars), look at the flashing and the bead of sealant around the frame.
- Note any cracked, shrunken, or peeling sealant, and lifted or corroded flashing at the corners.
- Clear leaves and debris from the uphill side, where water and ice back up against the curb.
- Reseal the flashing joints with a roof-grade sealant, or have a roofer reflash if the metal has failed.
- On an acrylic dome, check the gasket where the dome meets the frame, a common entry point as plastic ages.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing skylight resealing schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
How do I know the leak is the skylight and not the roof?
Skylight leaks usually show as a stain right at the top or corner of the light well and worsen with wind-driven or heavy rain. Roof leaks tend to appear farther from the opening. The most common culprit is not the glass but the flashing, so check the sealant and metal around the frame first. If staining tracks straight down the shaft from a corner, the flashing seal is the prime suspect.
Should I reseal or just replace the skylight?
If the unit is under about 15 years old and the glass and gaskets are intact, resealing or reflashing is the fix, often a few hundred dollars. If the skylight is near the end of its 10–20 year life, the seals are fogging, or the flashing has corroded through, replace the unit and flash it fresh; doing both at once at $900–2,500 avoids paying twice for roof access.
When is the best time to reseal a skylight?
During a re-roof, without question. New flashing woven into new shingles is the most watertight and cheapest way to do it, since the roofer is already up there and the surrounding roofing is open. Short of that, tackle it on a dry, mild day, and never wait for a ceiling stain, which means water has already been getting in for a while.