Watch for early warning signs to avoid roof collapse, says Montreal home inspector

While winter is starting to weigh on Quebecers' spirits, the snow and ice is also weighing on our roofs.

Quebec homes are built to withstand accumulation of ice and snow on roofs, but it still pays to be wary

A worker looks over the scene after heavy snow accumulation caused the roof of a two-storey building to collapse Saint-Jérôme, leaving several people homeless on Sunday. (Ryan Remiorz/The Canadian Press)

While winter is starting to weigh on Quebecers' spirits, the snow and ice is also weighing on our roofs.

In the wake of a spate of collapses across the province, Andrée Laforest, Quebec's municipal affairs and housing minister, said that building owners need to be vigilant.

"We can't emphasize enough that owners are responsible for the safety of people who live in or enter their buildings," Laforest said. "Owners need to look out for warning signs in order to prevent a collapse." 

If there is a risk of collapse, in most instances owners should consult an expert. 

Quebec's workplace health and safety board (CNESST) warns that those who attempt do-it-yourself rooftop snow removal risk injury from falls and other hazards.

Ian Towers, a Montreal home inspector, says there are plenty of warning signs to be on the lookout for before a roof will collapse under the weight of ice and snow. (CBC)

Ian Towers, owner of a residential building inspection company called Inspectrum, said while it might be tempting to take matters into your own hands, it's not worth the potential risk.

So it's important to keep an eye out for early signs before disaster strikes.

It starts small

Heavy ice and snow can throw a building's framing out of square, causing plaster to crack and doors to stick, he said.

Doors not opening or closing properly are signs of trouble, as are ceiling cracks or sags. Water leaks or unusual creaking sounds are also cause for worry.

Roofs in Quebec are required to hold-up against up to 21 pounds per square-foot worth of accumulation, he said.

Workers clear off a flat roof to ensure the weight doesn't cause the building to collapse. (Radio-Canada)

Even though collapse is unlikely, homeowners should still be on the lookout for tell-tale signs things could be going wrong on their roofs.

The trick, he said, is to monitor the situation and plan ahead — to take action before the situation becomes serious.

Safety first

Towers said it's better to hire professionals or, at the very least, use an extendable snow rake that allows the user to reach the roof from the ground without actually climbing on top.

Removing snow accumulation is no simple task because, if done carelessly, the roof can be damaged or someone could be hurt.

"People who scrape their roofs with a shovel can damage the shingles and the roof covering themselves and cause leaks or rip the shingles off," he said. "So, it's like having more damage than if they hadn't gone up there in the first place."

It's important to monitor the situation, he explained, and schedule a contractor in advance because a homeowner can't just call up a company in the middle of a late-night snowstorm expecting immediate service.

Sloped roofs generally don't have issues in the winter, Towers said. However, ice damming can sometimes occur and this can eventually lead to structural issues.

The Jules-Émond school in Val-Bélair, a northeast Quebec City suburb, was closed Monday for preventive rooftop snow removal. (Guillaume Croteau-Langevin/Radio-Canada )

That snowmelt can freeze before it drips off the roof, causing leaks and damming. A lot of icicles hanging on the roof's edge may be a sign of ice damming, he said.

Flat roofs most at risk

Long periods of rainy weather during the winter season don't just lead to icy sidewalks — it can mean substantial ice accumulation on roofs.

"That's a tremendous amount of weight," he said. "Keeping drains open in the wintertime is very important."

Drains can become blocked, he said, adding to the problem.

Flat-roofed buildings are generally engineered to handle the weight, but the structure can become damaged by water infiltration or weaken with time.

The workplace health and safety board offers instructions for snow removal from flat roofs (in French).

The denser the snow, the higher the risk

It's not just the depth of snow that matters, but the density.

"If the snow is light and fluffy, the roofs can handle quite a bit," he said. "Snow can weigh between two pounds per cubic foot to 20 pounds per cubic foot."

If the snow weighs 20 pounds per cubic foot, he said, that's like a dense slush.

"If you do have concerns, and you really want the snow removed, you should call a professional," he said. "You shouldn't be doing it yourself."

With files from Arian Zarrinkoub