Several years ago, a very competent engineer, Eric Karsh, and Michael Green put together a paper called “The Case for Tall Wood Buildings”. It looked at three ranges of tall wood—up to 12 to 14 storeys, up to about 22 to 24 storeys, and up to 36 storeys. The principal concern around building with wood is not the strength of the material. When you get to around 50 or so, then you have a lot of wood and not a lot of space inside. The principal concern is around fire.
There are two ways to address fire in these buildings. One is to coat it with something like drywall, which was used in the Brock Commons Tallwood project. The other is to have a lot more wood than the fire can consume before the people get out, so there's the charring effect, which is combustion and encapsulation—or you can use a combination. Strength is not really the concern. It's principally around fire. That's where it gets into the perceptions.
If I were a building inspector and I had never seen a 16- or 18-storey building, I'd be justifiably concerned, because my local government would be on the hook if that building failed. This is where it's an iterative process. If we have a success with the 18-storey building in Brock Commons, that will probably make it easier for a 12-storey building to get built. I know there is a 12-storey building that a large company was approached to build in Toronto. That's wonderful. I think that's great. It's that kind of thing.
Wood is actually stronger on a strength-to-weight ratio than is steel or concrete by about a factor of two, but it combusts. That is usually the limiting factor. I think there are opportunities but we have to educate ourselves. We have to have confidence in the materials. We have to have success with buildings. Then we have to emulate that and duplicate that and expand that knowledge.
It makes it easier for us when there's a 10-storey building built out of cross-laminated timber in Austria or Australia. Then we can look at it and say, why can't we do that? There's a very friendly, collaborative, and competitive process going on among wood engineers to see who can build the tallest one. There's a 22-storey building in Vienna, and I know of a 34-storey one being planned for Vancouver. So who knows?