Leaking Skylight? Flashing, Seal or Replacement

Leak or condensation? Reading the symptoms

Start inside. Note when the water appears, where on the skylight it collects and what the weather was doing at the time.

Bathroom and kitchen skylights are the usual condensation suspects. Shower steam and cooking moisture rise into the shaft and meet glass that cooled overnight. In the San Gabriel Valley that happens most on clear winter mornings, which is why it often gets mistaken for a rain leak.

How does water get past skylight flashing?

A skylight is a hole in the roof with a box around it. Flashing is the metal that turns water around that box: a head piece on the uphill side, step flashing woven into the shingles or tile along both sides, and an apron that laps over the roofing below. Leaks start when any piece is missing, short, face-nailed or held in place only by sealant.

• Sealant doing flashing's job: caulk dries and cracks within a few hot summers, and many older installs rely on it alone.
• Debris dams: leaves and needles collect against the uphill side, hold water and push it under the head flashing.
• Reroof shortcuts: old flashing bent back around a new roof instead of a kit matched to the unit.
• Tile roof details: water runs under clay and concrete tile on the underlayment, so worn felt beside the curb leaks even when the tiles look perfect.
• Low curbs: a curb that barely rises above the roofing lets water splash over during heavy bursts.

How do roofers trace a skylight leak to its source?

A skylight leak gets traced the same way every time, from the evidence inside to the joints outside, before anyone lifts a shingle. Our order of work:

1. Ask when the drip appears, how long into the storm, and which way the wind was blowing. A leak that starts only after hours of rain points to saturated underlayment rather than an open joint.
2. Go into the attic and look at the shaft framing from behind: water lines, dark wood and wet insulation usually sit below the point of entry, often on the uphill side.
3. Walk the roof around the curb and check the head flashing, both runs of step flashing, the apron and the dome or glass for cracks.
4. Run a hose test on a dry day, starting at the downhill apron and moving uphill one side at a time while someone watches inside. Wetting the top first would send water over every lower joint and hide the real gap.
5. Inspect the glazing itself: fog between panes, a lifted frame gasket or a clogged weep channel on factory units.
6. Photograph each finding and write up the repair options with what each one costs.

Most leaks show themselves by step 3 or 4. The hose test earns its time on skylights with a history of repairs, where several layers of roof cement make every joint look suspect.

What our crews find when a skylight is opened up

On the post-war homes common in Rosemead and San Gabriel, the leaking unit is often a plastic dome on a site-built wood curb, sealed with layers of roof cement from past repairs. Peeling those layers back usually shows flashing that was never woven into the roof, just tucked under the shingles and tarred. The curb wood beneath is often soft at the uphill corners.

Another pattern is the skylight that was fine until a reroof. The new roofing went on, the old flashing stayed, and the first long storm found the gap. On tile roofs, the underlayment beside the curb can wear through while the tiles above still look fine from the street.

Each of those situations calls for a different fix, so we photograph the curb, the flashing and the attic side before recommending anything.

Reflash the old unit or replace it? Where we draw the line

Most of the labor in a skylight repair goes into lifting and relaying the roofing around the curb, not the flashing metal. That shapes the advice. If the unit is an acrylic dome that is already yellow or crazed, reflashing it means paying for that labor now and again when the dome cracks, so replacing the unit during the same visit usually costs less over a few years. If the unit is glass with clear panes and a firm frame, new flashing alone is the better spend.

Tile roofs tip the decision further, because lifting and resetting tile is slow and some tiles break. We would rather open a tile roof around a skylight once than twice. The case for repair over replacement is strongest on a shingle roof with a sound unit and a single failed joint.

Skylight repairs from least to most involved

Clear and reseal

If the dome and flashing are sound and one sealant joint has opened, cleaning and resealing it is a short-term fix. It buys time; it does not correct flashing that was built wrong.

Reflash the skylight

We lift the roofing around the curb, install new underlayment and a flashing kit or custom-bent metal, and relay the roofing. This is the right fix when the unit is in good shape and the leak is at the roof joint.

Replace the glazing or the unit

A cracked dome, fogged glass or warped frame means the unit itself has failed. Replacing it brings new flashing at the same time, and it is the moment to choose laminated, low-E glass that limits heat and condensation.

Rebuild the curb

Soft curb wood holds fasteners poorly and keeps wicking water. We replace the curb and any rotted sheathing around it before setting the unit.

Our skylight repair service covers all four. When the unit needs to go, skylight replacement is priced separately, side by side with the repair.

What should you do while a skylight is leaking?

1. Move furniture and set a bucket or towels under the drip; plastic sheeting taped across the shaft opening keeps water off the ceiling.
2. If you can reach the attic safely, pull back wet insulation around the shaft so it can dry.
3. Stay off the roof in the rain. Wet shingles and tile are slick, and stepping near a skylight risks a fall through the dome.
4. Take photos and note the time and wind direction; that record helps pinpoint the failure later.
5. Call for a repair once the storm passes, and if water is coming in fast, ask about an emergency roof tarp.

Fix the cause first, then the ceiling

Most leaking skylights can be repaired without a new unit if the glazing is sound, and most condensation problems are solved inside the house rather than on the roof. When the dome is cracked, the glass fogged or the curb rotted, replacement is the cleaner answer. If you are not sure which one you have, call (725) 745-8803. We will check both the roof side and the room side, take photos, and put the repair options in a written quote.