A skylight is an incredible architectural feature. By pulling pure, natural sunlight into dark interior corridors or vaulted living rooms, it can dramatically transform the ambiance of a home.
However, in the world of roofing, a skylight is essentially a giant hole intentionally cut directly into your primary waterproofing barrier.
In Calgary's brutal climate, that hole is subjected to intense freeze-thaw cycles, battering summer hail, and deep winter snow loads. Eventually, every skylight will fail. But when you look up and see a drip, you must determine: Is it just a cheap roof repair, or do I need to spend thousands on a full skylight replacement?
Here’s how to diagnose your skylight leak.
Scenario A: The Metal Flashing Has Failed
A skylight doesn't just sit flat on the roof; it is sealed to the surrounding shingles using an intricate system of stepped metal, called flashing.
In Calgary, this metal expands furiously during a +30°C July afternoon and shrinks violently during a -30°C January night. Over a decade, this constant movement can cause the caulking to crack or the metal flashing to literally pull away from the wood.
Symptoms of Flashing Failure:
- ✅ The leak only happens when it rains or right as snow rapidly melts.
- ✅ The water typically drips from the drywall corners around the skylight opening, not from the center of the glass.
- ✅ The glass itself remains perfectly clear and transparent.
The Verdict: REPAIR. You do not necessarily need a new skylight frame or glass. A professional roofer can carefully strip the shingles away from the perimeter, install a heavy-duty Ice & Water shield, custom-bend brand new metal step-flashing, and seal the unit tight without touching the glass.
Scenario B: The Thermal Seal is Broken
Modern skylights are made of double-paned insulated glass filled with argon gas. This prevents the freezing outside air from mixing with your warm interior air. However, over time, the rubber gaskets holding the glass separate. The argon gas leaks out, and the thermal seal is irrevocably broken.
Symptoms of Thermal Failure:
- ✅ The glass looks permanently "fogged up," milky, or filled with condensation between the panes of glass.
- ✅ You feel a significant, freezing cold draft sinking down from the ceiling in winter.
- ✅ The skylight constantly drips water onto the floor in December, even when it is not raining or snowing outside (this is indoor condensation forming on freezing glass — see condensation vs roof leak to confirm the diagnosis).
The Verdict: REPLACEMENT. Once the internal seal fails, it cannot be "re-glued" or re-filled with gas. The unit has lost 100% of its insulating R-value. You must order an entirely new, modern, energy-efficient skylight unit to drop into the existing hole.
Scenario C: The Acrylic Dome is Cracked
Older homes in Calgary frequently feature "bubble" skylights made of acrylic or heavy plastic. While plastic is cheaper, it degrades extremely poorly under intense UV radiation.
Over 15 to 20 years, the sun bakes the plastic until it becomes incredibly brittle. When an August hailstorm rolls through, standard hail stones easily shatter or crack the weakened acrylic dome.
Symptoms of Acrylic Failure:
- ✅ Visible hairline cracks crawling across the plastic.
- ✅ The skylight has turned cloudy or severely yellow.
The Verdict: REPLACEMENT. A cracked dome cannot be siliconed back together reliably. The structural integrity is gone, and the next storm will shatter it completely. Upgrade immediately to shatter-resistant tempered glass for absolute peace of mind.
Our Honest Recommendation
If you are planning to undergo a complete residential roof replacement, we unconditionally urge you to replace your skylights at the exact same time—even if they aren't leaking yet.
Why you shouldn't wait: If your old skylight begins leaking two years after we install a brand new roof, we will have to tear up your beautiful new shingles and underlayment to install the new flashing kit. Replacing the skylight simultaneously ensures the entire roof system is integrated flawlessly under one contiguous warranty — read understanding roof material warranties before signing.