Basement-free buildings are better for the future climate

In July, torrential rains flooded basements across Ontario, causing $940 million in insured damages, and weeks later, caused nearly $2.5 billion in insured damages in Quebec, the Insurance Bureau of Canada says.

As climate change boosts the risk of extreme rainfall and flooding in many parts of Canada, including southern Ontario and southern Quebec, some Montreal-area politicians have implemented or proposed bans on basements — the most flood-prone part of a house — in vulnerable parts of the city.

Research also shows that all the concrete that goes into building basements adds greenhouse gases to the atmosphere and helps speed up climate change. Is it time to stop building them?

In June, the Montreal borough of Ville-Marie passed regulations banning homeowners from turning basements into habitable spaces in neighbourhoods at risk of flooding unless they ensure that the building is waterproofed to withstand heavy rains.

Then in August, the remnants of Tropical Storm Debby unleashed massive rains on southern Quebec, flooding huge swaths of the province and causing the costliest weather disaster in Quebec history, surpassing even the 1998 ice storm.

A month later, Maja Vodanovic, mayor of the Montreal borough of Lachine, advocated for banning the new construction of basement apartments in flood-prone areas of Montreal.

"We don't want to create a problem that we know is going to happen," Vodanovic told a city council meeting.

Such government regulations aren't without precedent. Craig Stewart, vice-president of climate change and federal issues for the Insurance Bureau of Canada, said when homeowners along the Ottawa River were flooded a few years ago, the province of Ontario offered them disaster relief funds to rebuild. But the money came with a catch: homeowners had to elevate their homes with stilts or build on higher ground. 

"No basement … so that it's well above the possible flood level," he said. "We've seen examples of municipalities and provinces [that] put these stipulations in place and, obviously, we think it's a good thing."

Traditionally, most buildings in Canada have been built with basements, a lower floor partially or completely below ground. It's one way to put a home's foundation below the frost line, as is recommended to prevent it from freezing, thawing and shifting with the seasons.

But times have changed. Environment Canada says storms that used to happen once in a century at a given location may now happen every 20 years, and those that used to happen every 20 years may now happen every five — and it's only getting worse.

Meanwhile, urban infrastructure is aging, and wasn't built for the growing population and warmer, wetter climate we're experiencing.

Bernard Deschamps, who worked in the insurance industry for 35 years, said that means the risk of flooding, especially in basements, is increasing.

"We need to do something about it," he said.