Last week, we addressed the issue of resilient architecture, in connection with climate change. While the heavy spring precipitation, combined with a rapid thaw, once again made the headlines, is it time to rethink the way we build our homes in Quebec? Yes, answer several experts.
Emmanuel Cosgrove is categorical: “For new construction in the suburbs or in the countryside, we strongly recommend houses on slabs. Digging a basement should be avoided,” says this specialist from ÉcoHabitation, an organization dedicated to sustainable construction.
Water is never far away when digging a basement. It is sure that it will go up. It’s like jumping in puddles in the schoolyard: you have to put on rubber boots; but there, our houses are in runnings.
Emmanuel Cosgrove, EcoHabitation
Moreover, the habit of digging a basement is more a cultural phenomenon than a technical necessity, he adds. “It has nothing to do with the Building Code. »
“In theory, it’s to go below the frost level. But if you lay rigid insulation panels on the ground, you prevent the frost from going down under the building. This avoids a lot of problems and insurance claims,” he points out.
Water damage is the number one cause of home insurance claims in Quebec, the Insurance Bureau of Canada pointed out last March, which encourages citizens to take the appropriate protective measures now.
PHOTO MARCO CAMPANOZZI, THE PRESS
Patrick Ranger, CEO and co-founder of Belvédair
Patrick Ranger, of the firm Belvédair, also recommends the concrete slab rather than the basement. Not only for its virtues against water infiltration, but also for its environmental merits.
“A basement requires a lot more concrete, a very polluting material. According to our calculations, it represents 70% of the carbon footprint for the lifetime of a bungalow, including its energy consumption,” he says. “It is certain that the quantity must be limited. »
That said, building a house on a slab isn’t always the best option, says Ranger. “In the case of sloping land, the excavation and backfilling work to build an embankment or a retaining wall would be excessively expensive. »
In these situations, the firm Belvédair recommends the garden level, with one side buried and another above ground.
PHOTO EDOUARD PLANTE-FRÉCHETTE, THE PRESS
Two houses almost submerged by water in Baie-Saint-Paul
Flood zones
Another basic precaution, adds Patrick Ranger: first consult the maps of flood zones, available at city halls and on the Geo-Floods site of the Quebec government. If there is a risk of flooding, the first level must be at least one meter above the level of a bicentenary flood, ie one that has occurred once in the last 200 years.
“We built a house near Lake Champlain. To protect it, we raised the ground to place it on a podium. The owners will not be able to reach it in the event of a rise in water, but they will find it intact, ”explains Mr. Ranger.
Moving away from a watercourse is not enough, he continues. “A river located in a plain can come out very far from its bed. »
The spring floods of 2017 and 2019, which forced evacuations in several municipalities, also prompted Quebec to revise the delimitation of flood zones.
In parallel with this revision, Public Security undertook a major project in 2019 to simulate various complex scenarios of meteorological disasters. The results will push municipalities to strengthen the resilience of their neighborhoods and the residences of their citizens, says Isabelle Thomas, director of the AriAction research group.
“Each neighborhood can have different challenges, which require different adaptations. In some cases, should the use of the basement be abandoned? Yes of course. In the case of Sainte-Marthe-sur-le-Lac [dévastée à la suite de la rupture d’une digue en 2019]it is obvious that children’s rooms should no longer be set up in basements,” she believes.
In the worst case, the relocation of certain complete neighborhoods will have to be considered, adds the professor at the University of Montreal.
PHOTO HUGO-SÉBASTIEN AUBERT, LA PRESSE ARCHIVES
A dike broke in 2019 in Sainte-Marthe-sur-le-Lac, causing immense damage.
Social debate
That our homes are increasingly threatened by water should not surprise us, says Gonzalo Lizarralde, professor at the University of Montreal and author of the book Unnatural Disasters. “In the past, municipalities have accepted the construction of houses in risk areas. They have also concreted and asphalted ecosystems that once served as sponges in front of rising waters. »
Building a water-resilient home “is the easy part,” he adds. “We know the recipe: raise the houses, no basement, no electrical panels in the lower parts, etc. The difficult question is: what to do now with the current houses built in the wrong places? »
Possible relocations will meet – with good reason, he says – strong opposition from the population emotionally attached to their land and heritage. In addition, building new houses also has an environmental cost.
“This question is not a politically profitable issue, but it still requires a debate in society,” concludes Mr. Lizarralde.