Ice dams and roof snow removal: what to do

Every winter, snow and ice pile up on roofs across Greater Montréal. Most roofs handle it well, but wet snow, a thaw followed by rain or several storms in a row can add a lot of weight in a few days. In a March 1, 2023 release (in French), the Régie du bâtiment du Québec (RBQ) reminds owners that each of them is responsible for the safety of the people who live in or visit their building.

1. Signs of an overloaded roof

According to the RBQ, the first clues often show up inside the house:

• new cracks in interior walls;
• interior doors that stick or rub;
• unusual creaking in the framing;
• a ceiling that starts to sag or bulge.

If you notice any of these, the RBQ recommends clearing the roof whatever the amount of snow on it. Stay out of the affected room and call a company before the next storm.

2. How an ice dam forms

An ice dam is a ridge of ice along the lower edge of the roof. Heat escaping from the house warms the roof deck, snow melts higher up the slope, and the water refreezes when it reaches the overhang, which stays cold. Water trapped behind the ridge eventually backs up under the shingles. Tell-tale signs: big icicles along the gutters, a thick band of ice at the roof edge, water stains on the ceiling or at the top of exterior walls, sometimes only in spring.

Chopping at the ice with an axe or hammer damages the shingles and fixes nothing. The cause is almost always in the attic: warm air leaks, too little insulation or blocked ventilation. Our guide on attic insulation explains the order of the work, and the one on gutter maintenance shows how to keep gutters from freezing full of leaves.

3. Icicles, carports and exits

The RBQ also asks owners to remove ice and icicles hanging from the edge of their buildings: when they fall, they put cars and pedestrians at risk. It urges the same care with temporary carports, and says emergency exits, balconies, sheds and garages should always be kept clear.

4. Flat roofs and snow thrown off the roof: Montréal and Laval rules

The City of Montréal defines a flat or low-slope roof as one with a pitch under 2:12 (16.7%), on its roofing page (in French). If winter leaves a leak and the membrane has to be redone, its page on renovating a flat or low-slope roof (in French, updated February 2, 2026) says a borough permit is generally required to replace the covering, while maintenance and repairs need none. Several boroughs then require a white or reflective covering, or a green roof.

Snow pushed off the roof has to stay on your lot: in Montréal, snow from private property may not be dumped on the sidewalk or in the street and must be piled on the property (snow removal on private land, in French). In Laval, the City asks residents to report snow left on the roadway by a resident or a contractor through Mon dossier (snow removal priorities and steps, in French). Make this clear to the company that clears your roof.

5. Stay off the roof

The RBQ calls roof snow removal a risky job and suggests leaving it to specialized companies: falls, sliding sheets of ice, power lines near the edge. Ask the company for proof of liability insurance and how it protects the membrane or shingles while it works. If an ice dam has caused a leak, repairing the roofing, insulation or ventilation is construction work: the company must hold an RBQ licence in subclass 7 (insulation, waterproofing, roofing and exterior cladding), which you can look up online.

For the repair, browse roofers in Montréal, in Rivière-des-Prairies–Pointe-aux-Trembles or in Mirabel, or describe the roof problem and get quotes.