Innovation - Spring 2024

occur. “That’s not unique to mass timber; any kind of construction can have that failure,” said Ager. In addition, a large majority of fires have historically burned due to intentional ignition or human error, rather than defects in building design. Only two percent the 3,928 BC structural fires in 2021 were caused by construction, design, or installation deficiency and 12 percent had a stated cause of mechanical or electrical malfunction. Meanwhile, Jackson’s experience in building exposed mass timber buildings convinces him that relying on char is an acceptable solution that will preserve lives and structures as a last resort, with or without encapsulation. “There’s a clean, clear codified path to success for structural engineers to calculate char, and check the reduced cross section that has burned against a smaller load case,” he said. “That’s very well defined and understood in structural engineering circles. There’s lots of safe and pragmatic movement away from full encapsulation towards partial encapsulation and even full exposure.” Considerations for wildland-urban interfaces A mounting risk, not accounted for in typical discussion on structural fires, is structures compromised by wildfires. There is an increasing number of buildings damaged by wildfires in wildland-urban interfaces or areas that are in between wilderness and fully urban spaces. Last year, in one of BC’s worst wildfire seasons, 189 structures were burned in the Okanagan’s McDougall

Mass timber buildings emit less carbon and are easier to build, but carry fire risks that need to be addressed. Photo: Bruder/ natually:wood

Innovation Spring 2024

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