Skylight Leaking? Causes, Fixes and When to Replace It

In rough order of how often we find them on Airdrie roofs:

• Failed or improperly installed flashing. The step and head flashing around the curb is what keeps water out. If it was cut short, sealed with caulk instead of lapped properly, or has rusted or lifted with Chinook expansion, water gets in at the uphill corners.
• Dried-out seals and gaskets. The rubber or butyl seal between the glass and the frame hardens with UV and cold. After 10 to 15 years it cracks, and water tracks along the frame to the lowest corner.
• Hail-cracked or hail-damaged glazing. Hailstorm Alley is hard on skylights. Older acrylic domes craze and crack; even tempered glass can chip at the edge. The August 2026 storm that ran down the Crossfield to Airdrie corridor left plenty of cracked domes behind.
• Ice dams and snow backup. A skylight is a flat-ish obstacle on a sloped roof. Snow piles up above it, melts on a Chinook, and the water backs up under the head flashing. This is a winter-only leak on an otherwise sound skylight.
• Shingle or underlayment failure uphill. Water entering the roof a metre or two above the skylight runs down the deck and appears at the skylight because that is the first hole in the ceiling it meets.
• Cracked or failed curb. On older site-built curbs, the wood rots or the curb-to-deck seal fails, and water gets in below the flashing entirely.

Notice that only two of the six are actually the skylight. That is why a roofer's inspection, rather than a skylight replacement, is usually the first step. Our roof repair service in Airdrie covers all six.

Condensation vs leak on a skylight is the question that saves the most money, because the fix for condensation is free or nearly so. Skylights are the coldest surface in a room, and in an Alberta winter, warm indoor air hits that glass and drops its moisture. Enough of it, and water runs down the glass, pools on the frame and drips onto the floor, looking exactly like a leak.

If it is condensation, the fix is to reduce indoor humidity and warm the glass: run the bathroom fan longer, keep the humidifier lower, open the skylight blind so warm air reaches the glass, and consider a double or triple-glazed replacement if the unit is single-pane or old. Condensation between the panes of a double-glazed skylight, on the other hand, means the sealed unit has failed and the glass needs replacing.

If it happens during rain or a thaw, it is a leak, and the next question is where.

Few things are more frustrating than a skylight leaking after a new roof. The homeowner assumes the roofer broke something, and sometimes that is true, but the more common story is that the roofer reused an old skylight, or reused old flashing on a new roof, and the weak point simply carried over.

The usual scenarios:

• The old skylight was left in and the new shingles were worked around it. Its seals were already tired, and the disturbance of the reroof finished them.
• The original flashing was reused instead of a new flashing kit, because a kit costs money and the old one "looked fine".
• Generic step flashing was site-bent for a skylight that needed a manufacturer-specific kit.
• The ice-and-water membrane was not carried up and around the curb, so the first ice dam of the winter found the gap.
• The curb height ended up too low after a thicker shingle went on, and snow now sits over the head flashing.

This is why we recommend replacing any skylight over about 15 years during a reroof, and why every quote should say in writing whether the skylight is being replaced, reflashed with a new kit, or left in place. If yours started leaking within a year of a new roof, go back to the roofer first; a written workmanship guarantee should cover flashing. Our guide on how to choose a roofing contractor in Airdrie explains what to look for in that guarantee.

Skylight repair cost depends almost entirely on which of the causes above is at fault. Rough Alberta market guides as of 2026, not quotes; every roof is different and a free on-site visit gives you an exact figure.

The pattern is clear. On a skylight under about 12 years, a repair is usually worth it. On one past 15, you can spend $1,000 reflashing a unit whose seals will fail next year. Our Airdrie roof repair cost guide covers what drives the numbers on the roofing side.

Skylight replacement cost in the Airdrie area as of 2026 runs roughly $1,200 to $3,500 per unit installed, depending on size, whether it is fixed or venting, glazing type, and how much roof work is needed around it; our skylight replacement cost guide breaks that down by unit type. Large, electric-venting or custom units run higher. Doing it during a reroof is cheapest, because the shingles around it are already off.

Replacement usually beats repair when:

• The skylight is more than 15 to 20 years old
• The glazing is an old acrylic dome that has yellowed, crazed or cracked
• Condensation has formed between the panes, meaning the sealed unit has failed
• The frame is corroded or the curb is rotten
• You are reroofing anyway
• It has leaked more than once despite repairs
• Hail has damaged it and insurance is covering the roof (ask your adjuster whether the skylight is included; confirm with your insurer or broker)

Modern skylights are better than what was installed in the 1990s and 2000s. Double or triple glazing, low-e coatings and factory-integrated flashing kits mean less condensation, less heat loss in winter and far fewer leaks. If the unit is in a bathroom or a north-facing room where condensation has been a problem, the upgrade is noticeable. Our skylight replacement service in Airdrie covers the full job, including the roofing around it.

A skylight in Airdrie faces a harder life than one in Vancouver. Hail is the obvious reason; a stone the size of a quarter will crack an old acrylic dome outright and can chip tempered glass. After any storm, look at the skylight from inside for cracks, crazing or a change in how light comes through, and at the flashing from outside for dents.

Chinooks are the quiet one. A 30-degree temperature swing in a few hours expands and contracts the frame, the flashing and the sealant at different rates, and after enough cycles the joints open. Skylights on south and west slopes take the worst of it.

Snow is the third. A skylight interrupts the slope, snow piles against its uphill side, and the meltwater has nowhere to go but under the head flashing. A small cricket or saddle above larger skylights, plus ice-and-water membrane carried well up the slope, solves most of this. If ice dams are a recurring problem on your roof generally, our guide to preventing ice dams in Airdrie covers the attic side of the fix.

• Protect the floor and contents below the skylight, and put a container under the drip.
• Note the timing. Rain, thaw, or cold clear morning? That is the single most useful clue for whoever diagnoses it.
• Take photos of where the water is appearing and any staining on the light well.
• Check the attic if the skylight well is accessible from it; staining on the framing tells you whether water is entering at the curb or uphill.
• Do not caulk from inside. It traps water in the well and hides the evidence.
• Do not go on the roof in rain, wind or frost to look at it.
• Call a roofer, not a window company, first. Most skylight leaks are roofing problems.

If water is coming in fast, or the glazing is cracked open after hail, our emergency roof repair service can tarp or temporarily seal the opening the same day, which keeps the insulation and drywall dry while a proper repair or replacement is arranged. Emergency tarping typically runs $300 to $1,000 as of 2026.

Sometimes. A skylight is a penetration, and penetrations fail first, so a leak there does not automatically mean the roof is done. But if the skylight flashing has rusted through, the shingles around it are curled and bare, and the roof is 20 years old, the skylight is a symptom rather than the disease.

Use the visit to get the whole roof looked at. If the skylight is the only issue, fix it. If it is one of several, our pillar guide to the signs you need a new roof will help you read the pattern, and our roof repair versus replacement guide shows how to put numbers to the decision. Replacing a skylight during a reroof costs a fraction of doing it separately a year later.

The worst outcome with a skylight leaking is paying for the wrong fix: a new skylight when the problem was flashing, or a flashing job when the problem was condensation. A free roof inspection from Apex Roofing Airdrie traces the water to its source, checks the flashing, seals, glazing, curb and the roof uphill, and gives you an itemised written quote for the repair or replacement that actually solves it.

If it is a repair, it comes with our written workmanship guarantee. If it is time for a new unit, our skylight replacement service installs it with a new flashing kit and membrane, so the next roofer has nothing to work around.