Cross Laminated Timber is Changing the Way Urban Builders Scrape the Sky
November 19, 2020
From London to Tokyo, the race is on to build the tallest wood-framed skyscraper in the world.
How High Can CLT Go?
For high-rise builders with an eye on CLT, the only question left seems to be how high can it go? At 18 stories, the Brock Commons student dormitory at the University of British Columbia in Vancouver is currently the tallest wood-framed building in the world (see a time-lapse video of construction here). Architects in Chicago (River Beech Tower) and London (The Oakwood Tower) are racing to more than quadruple that height with plans for 80-story residential towers, but could be bested by Sumitomo Forestry, which expects to complete construction of a 1,148-foot tower in Tokyo by 2041.
Dubbed the W350, Sumitomo’s mixed-use plyscraper is designed so CLT components can be replaced across a rolling, multiyear schedule to extend the building’s lifespan and allow for additional recycling of the CLT into smaller dimensional pieces or biomass products. Engineered for both fire resistance and seismic resiliency, W350 will cost twice as much as a conventional steel tower, but Sumitomo expects CLT costs to ultimately fall in line with concrete and steel as the construction practice proliferates.
CLT is normally an assembly of dimensional studs glued together at right angles to create massive wood slabs that can be used for load-bearing wall or floor elements, achieving a structural integrity comparable to those of steel or concrete but with the benefits of wood. This unique composition allows CLT to have strength in two directions, as opposed to glulam, which generally has one-directional strength. Heat-resistant glues aim to make CLT as fire safe as concrete or steel, and the comparatively light weight means CLT is easier to transport, resulting in lower freight costs and reduced carbon emissions.