Recently I spoke with a Vancouver architect who specializes in cross laminated timber buildings. As he described the benefits of the structural material, he made an important point about the current american seismic code. As it stands, the seismic code mandates that all structures are built to allow inhabitants to escape safely after a major seismic event. However, there is no requirement that buildings stay functional after a major seismic event. There is no incentive to engineer buildings beyond the code requirement and thus, if a major earthquake were to hit Seattle, much of the city’s building stock would be deemed unusable.
When concrete buildings are under seismic pressure, they are engineered to sway but not fall down, allowing inhabitants to escape but making no further guarantees about the structure’s integrity. As the building sways, the concrete cracks making it unsafe and difficult and expensive to repair. Buildings built with cross-laminated timber are less likely to crack under seismic pressure due to the inherent flexibility and self-levelling properties of wood. If we were to build skyscrapers out of wood, they would be much more likely to withstand an earthquake and remain usable after the fact.
It’s difficult to imagine every building in the seattle area being deemed unusable after a major earthquake. Until we were able to rebuild, we would need to completely rethink the way we conducted business. It is also mind boggling to think of the cost that would be incurred by property owners, insurance companies, investors and local government in order to rebuild that much infrastructure. While CLT construction may not be Seattle’s silver bullet solution to seismic resilience, if I were an investor or insurance provider, I would sleep better knowing that my buildings were constructed with CLT and likely to be some of the last ones standing after “the Big One” hit.