Last month, a tornado that reached wind speeds of up to 210 km/h tore through the south of Barrie, Ont., affecting over 100 homes in the area; many of which had roofs upended, windows smashed, and cars flipped.
Some of this damage could have been mitigated if extra precautions were introduced to the Canadian Building Code, argues Greg Kopp, lead researcher for the Northern Tornadoes Project and an engineering professor at Western University in London, Ont.
“The national building code for housing is kind of weak on wind loading,” he says. “I think it’s great for snow loading. It’s great for energy efficiency, which are two things that we really care about in Canada, but I think wind loading has been kind of secondary.”
This is a growing issue. While the Northern Tornadoes Project hasn’t collected enough data to confirm whether climate change is causing an uptick in tornadoes across Ontario, Kopp says there is an increased chance of people being hit by a tornado. This is due to population growth. Since we’re building more infrastructure and taking up more space, populated areas are more likely to be hit by a tornado, Kopp says.
The Ontario Building Code, which is informed by the Canadian Building Code, has few precautions in place to deal with this.
“Nothing I have read in the Ontario Building Code or the Building Code Act talks about construction to resist tornadoes,” says Huntsville architect Duncan Ross in an email. “In over 30 years as an architect, anything I have ever read has generally indicated that tornadoes are difficult to design against and that reinforced concrete is the most successful at resisting those forces, but nothing is enshrined in the Ontario Building Code.”
In Barrie, homes were primarily affected by the tornado, but according to Karl Korpela, chief building official for the municipality of Dysart et al, cottages, which abide by the same building code, are just as vulnerable.
Korpela reminds anyone building a cottage that the Ontario Building Code is the minimum standard for building a safe structure. “I always tell people nobody should build to the minimum set of rules,” he says.
The building code does stipulate a minimum nailing requirement for rafters into the top plates of the walls to deal with wind load, but according to Kopp it wouldn’t be enough to protect against the wind speeds that occurred in Barrie.
As a result, Kopp is advocating for hurricane ties—a steel strap that helps anchor roofs to wall connections—to be added to the Canadian Building Code. “When a roof fails in a tornado, it makes the walls more vulnerable to collapse, and those collapsing walls are a threat to life,” he says. “[Hurricane ties] are relatively low cost and a simple measure to increase life safety.”
For cottages, the lack of a foundation can also be a problem during a tornado. “In the early ‘80s, there were cottages on Lac Blue Sea in Quebec, and a tornado lifted a cottage into the air that wasn’t fastened to a foundation, and someone was in it and drowned,” Kopp says.
If a cottage has a foundation, Kopp recommends ensuring it’s fastened to the base of the walls. And if your cottage is sitting on the ground, he says it’s worth thinking about putting in a foundation.