Chinook Ice Dams in Calgary: Why Your Ceiling Leaks in Winter

Calgarians love a Chinook: a warm, dry wind off the Rockies that can push temperatures up 20 degrees or more in a matter of hours in the middle of winter. Your roof is less of a fan. Rapid melt followed by a sudden refreeze is the perfect recipe for ice dams, and ice dams are one of the most common causes of winter ceiling leaks in Calgary.

How Chinooks Create Ice Dams

1. Snow builds up on the roof during a cold spell.
2. A Chinook arrives: the snow melts quickly, and heat leaking from the attic adds more melt.
3. Meltwater runs down to the cold eaves and overhangs.
4. Temperatures drop again, often overnight, and that water freezes into a ridge of ice at the eaves.
5. Repeat. The ice dam grows with each cycle, and water pools behind it, backing up under the shingles and into the attic, walls and ceilings.

Calgary’s frequent freeze-thaw swings mean ice dams can build up and leak several times in one winter.

Warning Signs

• Thick ice ridges and large icicles along the eaves
• Water stains on ceilings near exterior walls
• Wet or frosty attic insulation
• Peeling paint or bubbling drywall on upper floors
• Water dripping from light fixtures or around windows

Attic Frost: The Other Chinook Leak

During deep cold, warm moist air leaking into the attic freezes on the underside of the roof deck and nails as frost. When a Chinook warms things up, all that frost melts at once and drips onto insulation and ceilings. It’s often mistaken for a roof leak. The fix is air-sealing and ventilation, not shingles.

What to Do When It’s Leaking

1. Put buckets and towels under drips; move furniture and electronics.
2. If a ceiling is bulging, carefully puncture the lowest point to drain it into a bucket.
3. Turn off power to light fixtures with water in them.
4. Don’t climb an icy roof or chip ice with tools; you’ll damage shingles.
5. A roofing pro can steam ice dams off safely.
6. Call a water damage restoration company in Calgary to dry the attic, ceilings and walls before mould starts.

Restoration After an Ice Dam Leak

We locate wet areas with thermal imaging and moisture meters, remove saturated insulation where needed, dry ceilings and wall cavities, apply antimicrobial to prevent mould, and repair drywall and paint once materials are verified dry. Typical costs for ceiling and wall damage run $3,000–$12,000; see the cost guide.

Insurance

Many Alberta policies cover sudden water damage from ice dams, though some exclude or limit it, and damage from long-term neglect may be denied. Report promptly and document everything. See our insurance guide.

Preventing Ice Dams in Calgary

• Air-seal the attic floor around pot lights, attic hatches, plumbing stacks and bath fans.
• Top up insulation to keep heat in the living space.
• Ventilate with soffit and ridge/roof vents to keep the roof deck cold.
• Vent bath and kitchen fans outdoors, never into the attic.
• Rake snow off the lower roof from the ground after big storms, especially before a forecast Chinook.
• Consider heat cable at eaves on problem areas.
• Keep gutters clear before winter.

Also see: frozen and burst pipes · hail damage leaks