By Chris Dunlap
Wood is the newest – and oldest – material employed in base building construction. Now making a comeback, wood is even replacing steel and concrete in high-rises across the world.
This growing trend is gaining traction as early adopters find success in wood’s sustainability and its ability to shorten construction schedules, reducing labour costs. The world’s tallest wood structure to date, the University of British Columbia’s Brock Commons student residence, rises 18 stories. Completed four months ahead of schedule, the construction minimized labour and resulted in a 2,432-metric ton reduction in CO2 emissions, equivalent to taking 500 cars off the road for a year. Wood also performs extremely well in earthquakes, compared to other high-rise building materials such as concrete, which is a significant benefit for British Columbia and America’s West Coast.
In addition to the economic and environmental benefits, the case for mass-timber wood construction is also aesthetic. Companies find that more and more workers want to be connected to nature in a warm, open wood-look environment. As these companies compete for talent, mass-timber buildings seem more attractive. Now in development across the North America, mass-timber buildings are being proposed in Chicago, Vancouver, New York City, Edmonton, Newark, NJ and Portland. They’re going to be skyscrapers, arenas, mixed use developments and residential complexes.
But what about the fire risk? Isn’t a building with wood construction a major liability for building owners, operators and developers?
The answer is: Yes.
In fact, the National Building Code of Canada is expected to allow wood construction up to 12 storeys. The BC Building Code has already allowed it. Developers who want to bypass this rule and build taller need to demonstrate to the AHJ that their building can withstand the local code’s equivalent fire rating requirements for high-rise buildings, typically two to three hours for various structural components. Builders are doing this by engineering large pieces of wood with sheet rock or drywall around beams, or making the wood thicker by binding multiple planks together with fire-retardant glue. Others are using engineered or pre-fabricated wood composite, designing hybrid wood/steel structures.
Even with these modifications, the potential for liability remains.
The increased risk of fire. Every building material will be negatively impacted by exposure to fire. Steel buckles, concrete spalls and wood, of course, burns. The idea of building with larger pieces of wood is to allow the outside of the wood to char before the internal wood structure is compromised. This process typically takes two to three hours, with a single plank of wood. Therefore, it’ll take longer with a double plank, or one covered with a heavy building material. Each AHJ will rule on a case-by-case basis if wood construction should be permitted.
Don’t forget about water damage. A second challenge is the water damage caused by a building fire. All mass-timber buildings constructed so far are outfitted with sprinkler protection. But some questions remain: Will water damage accelerate the rotting process? Will it warp the wood or affect the fire-retardant glue, and therefore, the building’s fire rating?
Insuring wood buildings. These big risks make insuring wood buildings, and their surrounding properties, a great challenge. Currently, research on mass-timber buildings and their survival during a fire is limited and doesn’t disprove the known risks.
What is known is that obtaining private insurance for buildings with a wood base infrastructure can cost as much as 7.5 times more than buildings built with a concrete foundation. The increased rates are a direct result of: greater fire risk, higher moisture risk, the rise in extreme weather globally and difficulty in obtaining insurance for wood framed structures. When it’s difficult to find insurance, rates rise.
If you are considering a wood construction, contact your HUB advisor to find out about your potential increased risk, and how HUB can help insure you.