Why is my roof leaking in winter?
In Edmonton, a winter roof leak almost always comes from one of three things: an ice dam pushing meltwater under your shingles, attic rain (frost inside the attic melting during a warm spell), or a true roof leak through damaged flashing, vents or shingles. They look the same from inside your house, a stain or drip on the ceiling, but each one has a different cause and a different fix. Getting the cause right matters. Homeowners often pay for a roof repair when the real problem is attic moisture, or seal an attic when the real problem is a cracked vent boot. Either way, the leak comes back next winter. This guide shows you how to tell the three apart in a few minutes, what to do in the first hour, and what a winter roof leak repair in Edmonton usually involves. Ice dam, attic rain or roof leak? How to tell in 5 minutes Match what you see to the most likely cause. Timing and location of the water are your best clues. What you notice Most likely cause Why Water near exterior walls or above windows, thick ice along the eaves, icicles Ice dam Meltwater backs up behind ice at the roof edge and runs under shingles Drips in many spots on the top-floor ceiling, starting on the first mild day after a cold snap Attic rain Frost built up on the underside of the roof deck melts all at once Wet spots around bathroom fans or light fixtures, frost or ice on nails in the attic Attic rain Warm, moist air is escaping into the attic and freezing Leak in the same spot every time, near a chimney, skylight or plumbing vent Roof leak (flashing or vent) Water gets in through a failed seal, usually during melts or rain Leak started after a summer storm or high winds, stain grows during thaws Roof leak (storm damage) Lifted, cracked or hail-bruised shingles let water through Fog or water on a skylight or sun tunnel, no stain around it Condensation Indoor humidity is collecting on cold glass, not a roof leak Quick test: if the drips appear in several places at once on a sunny, mild day after a long cold spell, think attic rain first. If water shows up in one spot every time snow melts, think flashing or vents. If you can see a ridge of ice along the eaves, think ice dam. Cause 1: Ice dams An ice dam is a ridge of ice along the edge of your roof that traps meltwater behind it. Heat escaping from your house warms the upper roof, snow melts, the water runs down to the cold eaves and refreezes. The trapped water then works its way under the shingles and into your walls or ceiling. Edmonton’s winters are made for ice dams, because temperatures often swing above and below freezing within a few days. Signs it’s an ice dam: What to do: don’t chip at the ice with a hammer or shovel; you’ll tear the shingles and eavestroughs. A roofer can remove the dam safely with steam. The long-term fix is stopping heat loss into the attic and making sure your eavestroughs drain. Our full ice dam prevention and repair guide covers this step by step. Cause 2: Attic rain — the “leak” that isn’t your roof Attic rain happens when frost builds up inside your attic during a long cold snap, then melts all at once when the weather warms up. The water drips through the insulation and stains your ceiling, so it looks exactly like a roof leak. But the water came from inside your house, not through the shingles. Here’s how it builds up. Everyday moisture from showers, cooking and laundry rises as warm air. If that air leaks into the attic through gaps around the attic hatch, pot lights, bathroom fans or plumbing stacks, it hits the cold underside of the roof deck and freezes. After a week of -25°C weather, an attic can be coated in frost. The first mild, sunny day melts it faster than the attic can dry out. Signs it’s attic rain: What to do: Attic rain won’t be fixed by new shingles. That’s why diagnosis comes before any repair quote. Ventilation helps, but on its own it rarely solves the problem if humidity and air leaks aren’t dealt with too. Cause 3: A real roof leak A true roof leak means water is getting through the roof itself, usually at flashing, vent boots or damaged shingles. In winter these leaks show up mostly during melts, when snow on the roof turns to water and finds the weak spot. The most common sources on Edmonton homes: Signs it’s a roof leak: the leak shows up in the same spot each time, sits below a chimney, vent or skylight, and gets worse during thaws or winter rain. Many of these are covered in our list of warning signs your shingles need repair. What to do in the first hour of a winter roof leak Whatever the cause, these steps limit the damage until a roofer arrives: What not to do: Can a roof be repaired in an Edmonton winter? Yes. Leaks can and should be fixed in winter, but some repairs are temporary until warmer weather. Roofers can remove snow and ice, replace vent boots, re-secure flashing and install cold-weather sealants or temporary membranes. Some materials, like shingle sealant strips and torch-on membranes, bond best above certain temperatures, so a permanent fix may be scheduled for a milder day. Typical winter costs in Edmonton (approximate, 2026): Winter repair Typical cost (CAD) Emergency tarp or temporary seal $350 – $900 Ice dam steam removal $500 – $1,500 Vent boot or small flashing repair $200 – $800 Leak repair with decking damage $1,000 – $2,500 Attic ventilation improvements $300 – $1,500 After-hours and storm-day calls usually cost more. See our full roof repair cost guide for every repair type. If your roof is
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