Flood-proofing for Canada’s national building code gets U.S. expert’s advice

Canada’s national building code has guidelines for how to construct homes to defend against wind, snow, rain and earthquakes — but not floods.

That could soon change.

The National Research Council (NRC) is working on potential changes to the National Building Code of Canada that would include information on how to flood-proof buildings.

“That’s a pretty difficult problem to wrap your arms around,” said Bill Coulbourne, president of Coulbourne Consulting, of Annapolis, Md., the team hired by the NRC to help with the building code update.

Coulbourne and his team are “uniquely qualified to carry our this work due to their extensive experience (140 years combined) in the design of flood resistant buildings,” said an email statement from Nic Defalco, communications adviser with the NRC.

Coulbourne Consulting will be paid $564,057 for its expertise.

In Canada, building construction falls under provincial jurisdiction, but the federal government publishes and updates the National Building Code to provide a baseline starting point.

Six provinces have accepted the national code as is. Alberta and British Columbia use the code, but with some variations. Ontario and Quebec have their own provincial codes.

This year thousands of Canadians were affected by floods.

Residents along the Ottawa River were forced to evacuate their homes when water levels rose to record levels in May. The month before, the Saint John River flooded homes throughout New Brunswick. In July, hay crops in British Columbia were destroyed when the Chilcotin River burst its banks.

The Canadian government says the frequency and severity of flooding will likely increase in the years ahead.

Canadian basements

Coulbourne Consulting has helped governments in the United States craft codes to build flood-resistant structures. But Canada’s code needs to be tailor-made.

“In the U.S., one of the prohibitions when you’re building in a flood plain is that you cannot build a basement,” Coulbourne said.

“In Canada, colder temperatures mean deeper foundations for buildings. You pretty much [always] have a basement.”

For homes built alongside bodies of water, Coulbourne suggests assuming that a basement will flood on a semi-regular basis and to plan accordingly.

That would mean using a basement for storage boxes that could be easily moved upstairs when floodwaters rise.

“[It means] keeping the basement in place but using it as a place to collect water when it floods,” he said. “That’s not a popular thing to do, as you can imagine. In some cases, that might be half their living space.”

Water more powerful than wind

For newer construction, keeping floodwaters out of basements is possible but challenging.

“The force of water is usually a lot higher than the load transferred into buildings from high winds and earthquakes,” said Coulbourne. “So water can actually exert quite a force on something like a building wall.”

If the structure is built strong enough to withstand the force of the water, the next step is sealing every entrance.

“The effort in flood-proofing a building is really to search for all those places that water could penetrate the building and figure out how to seal them up,” Coulbourne said.

Providing guidance, not writing policies

Coulbourne says his team is not telling the Canadian government exactly what its code should be.

“I don’t think that’s our place. We are going to stay out of the policy conversation as much as we can,” he said.

“We are working on reports and guidance documents that would provide the NRC with information about what to use and how to consider the current information that’s available in Canada.”

The NRC says the reports and analysis from Coulbourne Consulting “will be provided to codes committees for consideration in future editions of building codes, standards and guides.”