Property risk
Ice damming
A specifically chinook-country problem: heat escapes, snow melts, meltwater refreezes at the cold eave.
What happens
Heat escaping into the attic warms the roof deck. Snow on the warm section melts, runs down, and refreezes when it reaches the unheated overhang beyond the exterior wall.
The refrozen ridge builds into a dam. Subsequent meltwater pools behind it, and standing water on a roof designed to shed rather than hold water finds its way under shingles and into the building.
Calgary's chinook cycling makes this worse than a steadily cold climate would. Repeated melt-and-refreeze over a single winter builds and rebuilds dams many times.
Water entering this way appears at the top of exterior walls, in ceilings near the perimeter, and inside soffits — often well away from the actual entry point.
Why vacancy makes this worse
A vacant house is often kept cooler, which changes attic conditions, and nobody notices icicles forming or the first ceiling stain appearing at the wall line.
What a visit can observe
- Large icicles along the eaves
- Visible ice ridge at the roof edge
- Water staining on ceilings near exterior walls
- Damp or stained soffits
- Snow melting unevenly on the roof, with bare patches over heated areas
- Ice in gutters
Reducing the risk
- Ensure attic insulation and ventilation are adequate — the underlying cause is heat reaching the roof deck.
- Clear gutters before winter so meltwater has a path.
- Have roof edges observed from the ground after each chinook cycle.
- Do not attempt roof snow or ice removal without a qualified specialist; it damages roofing and injures people.
Related questions
Do chinooks cause problems for vacant properties?
Yes, and they are underrated as a risk precisely because they feel like relief.
A chinook can raise temperatures 20 to 30 °C within a day, then drop them back overnight. That cycling is harder on a building than steady cold. Snow melts and refreezes, building ice dams at roof edges. Meltwater runs toward foundations and refreezes in downspouts and window wells. Materials expand and contract repeatedly.
Chinooks also bring strong wind — sustained speeds regularly exceeding 100 km/h in west and southwest Calgary and in the foothills. That produces roofing damage, displaced outdoor items, and wind-driven water intrusion at windows and wall junctions.
The practical response is to check the property after chinook events rather than only on a fixed schedule: look at roof edges for ice dam formation, confirm downspout discharge is clear and running away from the foundation, check ceilings near exterior walls for the first signs of intrusion, and confirm nothing has been displaced by the wind.
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