Maintenance & Repairs

Why Your Skylight Leaks and How to Fix It

Updated October 2026 · 4 min read · By the Knoxville Roofing Quotes team

Skylights are great until they leak. Before you assume the whole thing needs replacing, figure out what's actually causing the problem. Sometimes it isn't a leak at all.

First: Is It Really a Leak?

Plot twist: some "skylight leaks" aren't leaks at all. They're condensation.

Warm, moist air from your house rises and hits the cold glass. Water condenses and drips down. It looks exactly like a leak, but the water is coming from inside, not outside.

Signs It's Condensation:

• Water appears on cold mornings, not during rain
• Moisture is on the inside of the glass
• Problem is worse in winter
• You have high humidity inside (from cooking, showers, etc.)

Condensation Solutions:

• Run bathroom fans during and after showers
• Use range hood when cooking
• Add a dehumidifier
• Check that bath fans vent outdoors, not into the attic. Our ventilation guide explains why
• If skylight has weep holes, make sure they're clear

If It's Actually a Leak

Real leaks happen during or shortly after rain. Here's where to look:

1. Flashing Failure

This is a common culprit. The flashing around a skylight directs water around the opening, much like the flashing around a chimney. When it fails, water gets in. Our chimney flashing guide explains how step and counter flashing work.

What goes wrong:

• Sealant dries out and cracks
• Metal flashing rusts or lifts
• Flashing wasn't installed correctly in the first place
• Roof shingles settle or shift, exposing flashing

The fix: Flashing can often be re-sealed or replaced without replacing the skylight. A roofer experienced with skylights can assess whether it's a repair or replacement situation.

2. Seal Around the Glass

The seal between the glass and the frame can fail over time, especially on older skylights. UV exposure, temperature changes, and age all take their toll.

What to look for:

• Visible gaps between glass and frame
• Cracked or missing rubber gasket
• Fog between the panes of double-glazed glass, a sign the glass seal has failed

The fix: Sometimes the seal can be replaced. On older skylights, it might make more sense to replace the whole unit.

3. Cracked Glass or Dome

Impact damage, hail, or just old age can crack the glass or acrylic dome. Even tiny cracks let water in.

The fix: Cracked glass or domes need replacement. On many skylights, just the glass panel can be replaced, not the whole unit.

4. Problems with the Curb or Frame

The wood curb that the skylight sits on can rot over time, especially if there have been small leaks for a while. Metal frames can corrode.

Signs:

• Soft or spongy feel around the skylight
• Visible rot or water damage
• Skylight seems to sit unevenly

The fix: Curb damage usually means removal and replacement. The good news is you can often upgrade to a newer, better skylight at the same time.

Repair vs Replace

Lean toward repair if:

• Skylight is relatively new
• Problem is clearly flashing-related
• Glass and frame are in good condition
• It's a simple, common skylight

Lean toward replacement if:

• Skylight is old and showing its age
• Multiple problems (leaking AND foggy glass AND failing seals)
• Curb or frame is damaged
• You're already replacing the roof
• You want energy efficiency upgrades

If You're Replacing the Roof

If your roof is being replaced and your skylights are getting old, ask for a price to replace them at the same time.

Why? The shingles and flashing around the skylight are coming off anyway, so the opening is already exposed. Replacing a skylight during the roof job avoids tearing into a brand-new roof later, and an old skylight in a new roof can become the first weak point. Get the skylight replacement listed as a separate line in each quote so you can decide. Our roof replacement timeline covers what else happens on the job.

DIY or Pro?

You can DIY:

• Dealing with condensation from inside the house
• Keeping an eye on it from the ground and the attic
• Protecting the inside with a bucket and plastic until a pro can look

Call a pro for:

• Flashing repair or replacement
• Glass or dome replacement
• Anything requiring work on the roof
• When you can't identify the source

Skylight work means being on the roof and getting the water-shedding details exactly right. Our guide to which roof jobs are safe to DIY explains why roof work is best left to pros.

Preventing Future Problems

• Look it over once a year from the ground and the attic for stains, debris and damaged flashing
• Keep leaves and debris from piling up on the uphill side
• Fix small issues early, before water damages the curb and ceiling
• Control indoor humidity to reduce condensation

Not sure where a leak is coming from? Our guide on when to repair a leaking roof covers how to track it down, and our roof leak repair page explains what a leak repair typically costs.