Skylight Leaking in Plano? How to Find the Cause Before You Fix It

Is your skylight leaking, or is it just sweating? Settle that first when you find a drip on the floor or a brown ring around the light well, because the two look almost identical from below and need completely different fixes. One is a roofing problem. The other is a humidity problem that no amount of caulk will solve.

A skylight leaking in a Plano home usually comes down to one of four sources: condensation forming on the inside of the glass, failed flashing where the unit meets the roof, a worn seal between the glass and its frame, or a crack in the glazing itself. The steps below take them in the order that wastes the least time and money.

Step 1: Rule Out Condensation Before Anyone Climbs a Ladder

Condensation is water that forms on the inside of the skylight when warm, moist indoor air meets cold glass, and it is a common reason a sound skylight gets blamed for a leak. The giveaway is a fine, even film of droplets across the whole inner pane, sometimes running down to the bottom of the frame and dripping off the lowest edge. A true leak usually shows up in one place, follows a path, and tends to appear during or just after rain.

Timing is the most useful clue. If the water appears on cold, dry mornings, after long showers, or while a pot has been boiling on the stove, and the roof has had no rain for days, you are almost certainly looking at condensation. The EPA's guidance on household moisture notes that condensation on windows can be a sign of high indoor humidity, and recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent.

A cheap hygrometer will tell you where your house sits. If the reading is high, the fix lives indoors: run bathroom exhaust fans, use a range hood that vents outside, and keep air moving across the skylight shaft. A skylight over a bathroom or kitchen is the one most likely to sweat.

Step 2: Map Exactly Where and When the Water Appears

Mapping the leak means recording where the water shows up, during what kind of weather, and how long after it starts, because each of the remaining causes leaves a different pattern. Photograph the stain now and again after the next storm.

• Water at the upper corners of the light well, or a stain on the ceiling just uphill of the opening, points toward the roof-side flashing or the shingles above the unit.
• Water that beads along the joint where the glass meets the frame points toward a failed seal or gasket in the skylight itself.
• Water that drips from the middle of the glass, or a stain that appears only after hail or a hard wind-driven storm, raises the possibility of a cracked pane.
• A wide stain with no clear drip line can be water travelling along the roof deck, so the true entry point may sit well above the skylight.

Step 3: Check the Flashing Where the Skylight Meets the Roof

Flashing is the layered metal or membrane collar that sheds water around the skylight, and on a residential roof it is a frequent source of a genuine skylight leak. The skylight manufacturer VELUX says in its overview of why skylights leak that an ill-fitting skylight will cause the unit to leak, whether the cause is a rough opening cut to the wrong size, the wrong-sized skylight, or not using the proper flashing for the unit.

Through binoculars from the yard, look for lifted or missing shingles above the skylight, rusted or bent metal at the corners, roofing cement smeared over joints as a past patch, and debris piled on the uphill side, which holds water against the flashing long after a storm passes.

Do not walk a pitched roof to check this yourself. Binoculars and a few photos give a roofer everything they need to know where to start.

Step 4: Inspect the Seals Between the Glass, Sash and Frame

A failed seal is a break in the gasket or sealant that joins the glazing to the skylight frame, and it lets water through the unit itself rather than around it. The Department of Energy's Building Science Education checklist for inspecting skylights for water damage tells inspectors to look for signs of water leakage through the unit itself or between the frame and sash, which is exactly this failure.

The skylight glass sits in direct sun through long Plano summers and then cools quickly during winter cold snaps, and that repeated expansion and contraction fatigues sealant and gaskets. Fogging between the panes of a double-glazed unit means the insulating seal has failed, even if no water reaches the room yet.

Step 5: Look for Cracked or Hail-Damaged Glazing

Cracked glazing is any fracture in the glass or plastic dome that lets water pass directly through the skylight, and in Collin County hail is the usual culprit. VELUX notes plainly that hail can cause damage to the glass where water can flow through.

From inside, a hairline crack in tempered or laminated glass can be hard to see until light catches it at an angle, so look up at the pane at different times of day. Older acrylic domes turn brittle and yellow with UV exposure and can split at the edges; one that has been through several hail seasons is near the end of its life even if it has not leaked yet.

If a storm cracked the glazing, have the surrounding shingles and flashing checked at the same time, since hail rarely hits only one part of a roof.

Step 6: Confirm the Source With a Controlled Hose Test

A hose test is a deliberate wetting of the roof in sections, from the bottom up, while someone watches inside, and it is the most reliable way to prove where water is getting in. The same DOE checklist recommends testing for water leakage by spraying the skylight unit and surrounding roof covering with a garden hose.

Order is what makes the test useful. Start by wetting the roof below the skylight, then the sides, then the glass, then the roof above the unit, giving each zone several minutes before moving up. If the drip starts while only the area above the skylight is wet, the water is entering upslope and travelling down, and the skylight itself may be blameless. It needs someone on the roof, so it belongs in a professional inspection.

Rain is the real test, and Plano gets a fair amount of it. The National Weather Service office in Fort Worth lists a 1991-2020 normal annual precipitation of 37.01 inches for Dallas/Fort Worth, much of it arriving in the heavy spring storms that also bring hail, so a marginal seal or flashing joint rarely stays hidden for long.

Step 7: Match the Fix to What You Found

The right repair depends entirely on which of the four sources the earlier steps pointed to, and the most expensive mistake is fixing the wrong one.

• Condensation: lower indoor humidity with ventilation and exhaust fans, and consider whether the skylight shaft needs better insulation. No roofing work is needed.
• Flashing: the lasting fix is removing the surrounding shingles and reinstalling or replacing the flashing kit made for that unit. Surface sealant is a temporary patch, not a repair.
• Failed seal or gasket: some units can be resealed or have the glazing replaced, but an older skylight with a failed seal is often a better candidate for full replacement.
• Cracked glazing: replace the glass panel or the whole unit, depending on its age and whether replacement parts are still made.

Any repair that changes the opening, the framing, or the size of the unit is more than maintenance. In that case, check with the City of Plano's Building Inspections department about whether the work needs a residential permit before it starts. For leaks traced to the flashing or the roof around the unit, our roof leak repair service covers the diagnosis and the fix, and a roof inspection is the sensible first step when you cannot tell which of the four problems you have.

Skylight Leak Questions Plano Homeowners Ask

Can I fix a leaking skylight with caulk?

Only as a short-term patch. Most skylight leaks come from flashing or failed seals, and caulk over the top tends to trap water and hide the real problem.

Why does my skylight only leak in heavy storms?

A leak that appears only in hard, wind-driven rain usually points to flashing or a sash seal that holds against ordinary rain but not against water pushed sideways or uphill. Note which direction the storm came from, because that tells a roofer which side of the unit to examine first.

Is water on my skylight in winter a leak?

Usually not. Droplets spread evenly across the inner glass on a cold morning, with no recent rain, are condensation from humid indoor air. Check indoor humidity and ventilation before calling anyone about the roof.

Should I replace my skylights when I replace my roof?

In most cases, yes. Tearing off and re-laying shingles around an existing skylight disturbs its flashing, and an older unit that survives the reroof may start leaking soon after. Replacing it while the roof is open avoids paying for the same access twice.