What does a leaking skylight cost if you wait?
Updated August 2026
← What skipping home maintenance costs
A skylight that weeps at the flashing costs $200–600 for a fresh flashing kit or reseal, but $1,000–5,000 once the water has soaked the light well, ceiling, and framing and started mold. The gap between those two numbers is time: acrylic domes and their gaskets last only about 10 to 20 years, well short of the roof over them, so a seal gone brittle keeps letting rain in every storm until someone acts. On a roof already near the end of its own life, the smart move is often to swap the unit during a reroof for $1,000–3,000 installed rather than reseal a skylight that will outlive its glazing by a season or two. Here is how a corner stain climbs into a five-figure repair.
The escalation ladder
Every row below is the same leak, left a little longer. The top is a cheap warning; the bottom is a claim.
| What happens | Typical bill | How fast |
|---|---|---|
| You reseal the frame or add a new flashing kit early | $200–600 pro, or $30–80 in sealant DIY | Same weekend |
| A tired glazing gasket gets resealed with new hardware | $300–700 with seals and fasteners | A day |
| The leak runs a full rainy season into the drywall shaft | $1,000–2,500 in ceiling and light-well repair | 3–6 months |
| Water reaches the framing and mold sets in | $2,000–5,000 with remediation and refinishing | 6–18 months |
| The skylight is past its life and gets replaced | $1,000–3,000 installed, best bundled with a reroof | When the roof goes |
| Rot spreads into the rafters around the curb | $4,000–8,000+ in structural carpentry | Years of neglect |
Warning signs
A leaking skylight almost always shows itself indoors first, at the four corners of the drywall shaft where it meets the ceiling. Watch for brown or yellow stains that appear or darken after rain, a musty smell in the room below, or paint that bubbles along the light well. Drips during a storm but not on humid, still days point to a flashing or seal failure rather than condensation, which fogs the glass from the inside and streaks straight down the pane. Peeling exterior sealant, rust on the flashing, and shingle granules washed against the curb are the outdoor tells. Any stain means water is already inside the assembly.
The prevention math
The whole prevention budget is a $30–80 tube of the right sealant and a look at the flashing once a year, or a $200–600 professional reseal every decade or so as the gaskets age. Run that check each fall when you are already clearing the roof and you catch a failing seal while it is a caulk job instead of a rotted ceiling. Set against the table above, an afternoon on the roof costs roughly one percent of the mold-and-framing repair it heads off. Fold the skylight into your skylight maintenance checklist and your seasonal home maintenance checklist, and see how often to reseal a skylight for the interval.
Every line in that table starts with a skipped 10-minute task. OnOtto keeps the 10-minute version on your calendar so the $2,000 version never happens.
Get the nudge before the billFrequently asked questions
Is my skylight leaking or just collecting condensation?
Condensation forms on the inside of the glass on cold mornings and runs straight down the pane, worst in a bathroom or kitchen, and it clears as the room warms and dries. A true leak shows up at the drywall corners of the shaft, appears during or right after rain, and leaves brown water stains that spread. If the drip tracks with storms rather than with indoor humidity, it is a flashing or seal problem that needs a reseal ($200–600), not just better ventilation.
Should I repair or replace an old skylight?
Reseal it if the unit is under 10 years old and the glazing is intact; a fresh flashing kit or bead of sealant runs $200–600 and buys years. Replace it if the skylight is near or past its 10 to 20 year service life, the acrylic has hazed or cracked, or you are already reroofing, since a new unit is $1,000–3,000 installed and doing it with the roof avoids paying twice for the flashing. See repair or replace a skylight for the full breakdown.
Why do skylights leak at the flashing so often?
The flashing is the metal that weaves the skylight into the surrounding shingles, and it takes the same sun, ice, and thermal movement as the roof while sitting where water naturally concentrates. Sealant hardens and cracks in 5 to 10 years, nails back out, and cheap tar patches from a past owner trap water rather than shed it. A skylight installed with a proper step-and-counter flashing kit leaks far less than one caulked in place, which is why a reflash beats another smear of roofing cement.
How long do skylights last before they need replacing?
Most residential skylights last about 10 to 20 years, with acrylic-dome and gasket-sealed units on the lower end. That is shorter than the 20 to 30 years an asphalt roof gives you, so plan to replace the skylight at least once during the life of the roof, ideally during a reroof. A unit past 20 years that has started staining the ceiling is usually cheaper to replace at $1,000–3,000 than to keep chasing leaks on. Check its age with how long a skylight lasts.