Why Your Skylight Leaks and How to Fix It

Updated January 2025 • 5 min read

Skylights are great – until they leak. Then they're just holes in your roof that drip on your head. But before you assume the whole thing needs replacing, let's figure out what's actually causing the problem.

First: Is It Really a Leak?

Plot twist: many "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
Improve attic ventilation
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 the most common cause. The flashing around your skylight directs water away from vulnerable joints. When it fails, water gets in.

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
Foggy glass (indicates seal failure)

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

General rule: If your skylight is under 15 years old and the glass is fine, repair is usually the right call. If it's 20+ years old or the frame/curb is damaged, replacement often makes more sense.

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 20+ years old
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

Here's some important advice: if your roof is being replaced and your skylights are more than 10 years old, seriously consider replacing them at the same time.

Why? The flashing gets replaced anyway. The area is already open. Labor to install a new skylight during a roof job is way less than doing it separately. And an old skylight in a new roof often becomes the first failure point.

Many roofers recommend this, and it's not just to sell you something. It really does make sense.

DIY or Pro?

You can DIY:

Clearing condensation issues
Applying sealant to small gaps (temporary fix)
Clearing debris around the skylight

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 involves being on the roof and maintaining waterproof integrity. It's not a great DIY project unless you really know what you're doing.

Skylight Giving You Trouble?

Get an expert assessment from Knoxville roofers who know skylights.

Get Free Assessment

Preventing Future Problems

Inspect yearly – look for cracked sealant, debris buildup, damaged flashing
Keep the area clean – leaves and debris trap moisture
Address small issues early – a tube of sealant now beats a replacement later
Control indoor humidity – reduces condensation issues