Skylight Leaking in Heavy Rain? What Is Really Leaking
When a skylight leaks in heavy rain, the water is usually getting in at the flashing where the skylight meets the roof, not through the glass. Hard rain and wind push water against that sealed edge, and a dried or loose seal lets it slip behind.
Call or text photos to (725) 502-3114 for a free, no-pressure inspection and a written estimate before any work begins.
What seals a skylight
A skylight is a hole in the roof with a window in it, and the roof has to seal around all four sides. Metal flashing laps under the roofing on the high side and over it on the low side, and it turns up the sides of the frame so water runs around the skylight instead of into it.
On a tile roof, the flashing sits under and against the tile, and the underlayment beneath ties into it. On a flat roof, the membrane turns up the curb the skylight sits on.
Every one of those joints depends on a seal or a bend in metal. Desert roofs fail in predictable places, and we check them in turn, starting with the flashing at walls, chimneys and skylights.
Why it leaks only in heavy rain
Light rain runs down the roof and around the skylight. Heavy rain puts far more water on the roof at once, and it piles up on the high side of the skylight, where the water hits the frame first.
Monsoon wind pushes rain sideways and upslope, into the edges that face the wind. If the seal has dried or pulled loose, water pushed against it in a storm can slip behind it.
Desert sun and heat do the rest over the years. Sealants dry and crack, and rubber hardens and splits. Leaves and grit that collect on the high side hold water against the flashing.
Our article on leaks that show up only in heavy or wind-driven rain covers the other places these gaps hide.
Leaking after a new roof
If the skylight started leaking after the roof was replaced or repaired, look at the flashing first. When a roof is redone, the flashing around the skylight has to be tied back into the new underlayment and roofing. If old flashing was reused, or the new layers were not lapped correctly around the frame, water can get behind them.
If that roof work is still under its own warranty, call the company that did it first.
Water on the inside of the frame
Water on the inside of the skylight frame is not always a leak. On a cold morning, warm air inside the house can condense on the cold glass and run down into the frame. If it shows up with no rain, and the inside of the glass is wet, condensation is a likely cause.
Water that shows up only when it rains, drips from the edge of the frame, or stains the drywall around the skylight shaft points to the roof. A cracked dome, broken glass or a failed seal between the glass and the frame is a problem with the skylight itself.
What you can check from inside and from the ground
Stay off the roof. Desert roofs are hot, steep and slick with grit, and a wet roof is worse.
Inside, write down when the water shows up, how long after the rain began, and whether the wind was blowing and from which direction. Look at the glass or dome from below for cracks. Remember that the stain is rarely right under the entry point.
From the ground, you may see leaves piled on the high side of the skylight, or tiles around it that are cracked or out of place. Take photos of the stain and the skylight, and text them to (725) 502-3114.
What we do
We trace the leak from the stain back up the roof. We check the flashing at the skylight along with everything else on that path, and when the roof does not give the answer away, controlled water testing confirms the entry point before we repair. Our roof leak detection page explains the process.
Flashing at skylights is part of our flashing and valley repair work, along with chimneys, walls and roof-to-wall transitions. We show you what we found and why it leaks. Every leak repair we perform is backed by a 5-year warranty. If a leak we repaired returns within that period, we come back and make it right.
A repair or a bigger job?
Often the fix is the flashing. A failed flashing edge is resealed or rebuilt, and the tile or roofing around the skylight is reset.
It is a bigger job when water has been getting in for a long time and the underlayment around the skylight has failed, or when the whole roof's underlayment is near the end of its life. We will tell you honestly whether your roof needs a targeted repair or has reached the end of its service life. See residential roof repair for the repairs we do, and how we find a roof leak for each step of the search.
Frequently Asked Questions
Why does my skylight leak only in heavy rain?
Heavy rain and wind push water against the sealed edges around the skylight. A small gap there stays dry in light rain.
Is it condensation or a leak?
Condensation shows up on cold mornings with no rain and wets the inside of the glass. A leak shows up with rain.
My skylight started leaking after a new roof. Why?
The flashing around the skylight has to be tied into the new roof. If it was reused or not lapped correctly, water can get behind it.
Do I need a new roof?
Usually not. Most leaks come from a repairable spot. We only recommend a re-roof when the roof has reached the end of its service life.
Who do I call for a leaking skylight?
If it leaks when it rains, start with the roof around it. Call or text photos to (725) 502-3114.