A handful of architects want wood to usurp concrete and steel as the key material for building skyscrapers. From Vienna’s HoHo tower to Stockholm’s Trätoppen and Minneapolis’s 18-story T3 project, wooden skyscrapers are being constructed as a way to make building quicker and more environmentally friendly.
Wooden skyscrapers have speed on their side, as they don’t require concrete floors, which can take weeks to dry. And they offer an environmental advantage. Experts believe concrete and steel buildings create about 8 percent and 5 percent of global emissions respectively. Trees, however, absorb CO2 and lock it away from the atmosphere.
The most obvious drawback would seem to be wood’s flammability. Indeed, the use of timber-frame blocks in construction has come under increasing scrutiny in recent years, with some experts in fire protection claiming that any type of wood in a structure raises concerns, and is dangerously vulnerable.
However, the new timber that architects are excited about is quite different from straight-up wood. First developed and used in the 1990s, cross-laminated timber (CLT) is comprised of small pieces of wood criss-crossed together and set with fire-resistant glue. Supposedly as strong as structural steel, and sometimes described in the industry as “plywood on steroids,” CLT’s unique composite allows architects to build with timber at heights previously deemed impossible.
CLT can be used to make huge pieces of timber, and even entire walls. “If you’re making a fire, everyone knows you don’t start with giant logs,” Anthony Thistleton, a founding director of Waugh Thistleton Architects, told the BBC in October 2017. “It would take a lot to ignite them.” Plus, unlike concrete and steel, it will not melt under extreme heats.
Weight is another consideration when it comes to using wood to create skyscrapers. Wind speeds increase at higher levels and so the taller the wooden building, the less secure it will be. “The need to build the highest is just a manifestation of the ego of the architect,” Thistleton told the BBC. “We should be building in timber for environmental reasons.
“The 20th century was the concrete age, it was all about the dominion of man over nature,” he continued. “Now we’re transitioning towards a different attitude, a more nurturing one.”