Roofing and Quebec Winter: Ice, Snow, and Ventilation
Winter in Gatineau averages 250 cm of snow, multiple freeze-thaw cycles, and winds that can top 90 km/h. A residential roof takes more stress between November and April than during six months of summer. Here's what happens above your head during the cold months and how to avoid expensive problems.
Ice dam phenomenon
An ice dam forms when attic heat melts snow at the middle of the roof, the water runs to the eave (where it's colder), and refreezes there. Ice builds up, eventually lifts the shingles, and water following finds its way directly into the deck.
It's the leading cause of winter damage on Gatineau homes, especially bungalows and low-pitch roof homes built between 1970-1995, which often have inadequate attic ventilation.
Visible signs: thick icicles hanging from gutters, a continuous slab of ice along the eave, dampness appearing inside near exterior walls after a warm spell.
Why attic ventilation is critical
A well-ventilated attic stays close to outside temperature. Snow doesn't melt underneath, the ice dam doesn't form, and the roof lasts longer.
To work, ventilation needs two things: air intake at the soffits (bottom of the roof) and air exhaust at the top (roof vents, ridge vents). If either is blocked — by insulation blocking soffits, or vents plugged by leaves — the system fails.
Current Quebec standard: 1 sq ft of ventilation per 300 sq ft of attic floor area, split evenly between intake and exhaust. Most homes built before 1990 are below this standard.
How much snow a roof can hold
A modern Quebec residential roof is designed for about 1.5 kPa of snow load, roughly equivalent to 70-90 cm of compacted wet snow. Most Gatineau winters don't exceed that as simultaneous accumulation — snow melts and slides off in segments.
The real risk: a heavy wet snowfall (sleet + snow), followed by a light dump on top. There, you can exceed designed load within hours.
If you see new cracks in interior walls, interior doors that start to stick, or new creaks in the structure — these are signs of abnormal load on the roof. Time to consider professional snow removal.
Roof snow removal: when and how
For a standard residential roof, snow removal is almost never necessary if the frame is in good shape and snow releases naturally. It's mostly for flat (commercial) roofs and low-slope sections.
If you decide to clear: don't climb on the roof yourself. Use a telescoping roof rake from the ground to clear the first row at the eave. That's the zone that matters for ice dams, not the centre of the roof.
For commercial buildings with flat roofs or low-pitch bungalows, call a professional — too risky to climb on an icy surface even with experience.
Pre-winter maintenance
Clean gutters in mid-October. Leaf-clogged gutters worsen edge ice dams and damage the gutters themselves when frozen water overflows.
Inspect sealant around roof penetrations (plumbing vents, range hoods, chimneys). Sealant turns brittle after 8-10 years and that's where water starts entering.
If you see moss or lichen on the north slope, treat before first snow. Under wet snow, this growth accelerates shingle degradation.
Winter tests your roof every year. An inspection in September-October, before first snow, costs one visit and prevents January leaks that cost ten times more to repair. Request your free fall inspection.
Related guides
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