Residential building material dealers historically have been shut out of the market for building mid-rise and high-rise buildings. But that could end if a study from Canada changes contractors’ and architects’ minds. “The Case for Tall Wood Buildings” argues that it’s not only possible but preferable to erect both mid-rise (six-12 stories) and high-rise (around 30-story) buildings using what it calls “Mass Timber” construction—combining thick, cross-laminated timber blocks for the vertical structure, other wood materials for the lateral shear walls and floor slabs, concrete for the foundation, and steel beams bolted to the mass timber panels to help keep the building flexible.
In this 240-page report, architect and co-author Michael Green dubs his new approach “FFTT,” for Finding the Future Through Timber. He argues that FFTT buildings would meet building codes and be price competitive with traditional concrete-and-steel structures with the extra benefit of helping fight climate change by using a green, renewable resource.
While wooden skyscrapers are an old concept (there’s a 19-story pagoda in Japan built 1,400 years ago, the study notes), fire and other structural concerns have limited construction of new wooden buildings in North America to about five stories. Now wood’s champions are fighting back by promoting the use of cross-laminated timber, or CLTs. These are thick slabs of solid-sawn lumber set down in layers at 90-degree angles to each other. Typical CLT blocks can be made as thick as 16 inches, and thinner panels can be as big as 64 by 8 feet. The thick blocks have proven to be strong, safe in a fire (because they char rather than burn), and easier to work with than steel beams.
CLT is getting a workout in Europe; the nine-story Stadthaus condo complex in London went up a few years ago (see “The Future of Wood,” September 2008), and the report says there are plans to build a 10- to 12-story wooden building in Australia, a 17-story building in Norway and a 30-story timber-and-concrete building in Austria. But in the United States, the only major example of CLT construction was a 78-foot church bell tower in Gastonia, N.C. (See “X Marks the Opportunity,” June 2011) Even Green’s report suggests further studies to help win favor for his FFTT concept.
The Tall Wood report was sponsored by the Canadian Wood Council and announced March 12. Download it here.