The Weird, Wooden Future of Skyscrapers

The first thing you notice when you walk into the office of Lever Architecture, in Portland, Oregon, is the smell: fresh, sweet, and vaguely Christmassy. That’s because Albina Yard, the year-old building that houses the office, was built out of fragrant Douglas fir. “It’s a space people immediately respond to on an emotional level,” says Thomas Robinson [1], Lever’s founder and the building’s architect.

Robinson is a pioneer in designing tall buildings that use wood, not concrete or steel, to bear their weight. Albina Yard is only four stories, but it’s the prelude to a more ambitious project: Framework [2], a 12-story mixed-use tower that will soon rise in Portland’s Pearl District. When it’s finished (likely in 2019), it will be the country’s tallest human-occupied all-wooden structure.

Although we’ve been building with trees since prehistoric times, they are having a moment, architecturally. Wooden structures similar to those in Portland have recently been built in Sweden, Finland, and the U.K., and a 24-story wooden building is under way in Vienna. Architects are even dreaming up wooden skyscrapers, such as a 35-story tower proposed for Paris [3] by Michael Green Architecture, a Canadian firm that designed an eight-story timber office building in British Columbia and a seven-story one in Minneapolis. (Although U.S. building codes generally bar wooden structures more than 85 feet tall, the federal government has recently promoted research into building with wood, hoping to revive the domestic timber industry.)

There are reasons we originally moved away from building tall with wood, of course, among them fires like the one that devastated Chicago in 1871. The new high-rises aren’t made of regular two-by-fours, however. Rather, they use a high-tech wood product known as mass timber. Framework’s skeleton [4] will be made of glue-laminated timber—pieces of lumber bonded together into massive beams and columns—while the walls and floors will be made of cross-laminated-timber (CLT) panels, in which layers of wood are stacked in alternating directions. [5]

Robinson’s team put both components through rigorous fire testing. A joined beam, column, and CLT panel were placed in a furnace, then weighed down with 25,000 pounds, to see how strong they would be after exposure to fire and heat. Two hours later, they emerged charred, but structurally intact. Mass timber doesn’t ignite easily—it’s more like a log than kindling. And the outer char layer that mass timber develops when burned actually insulates the wood.

Another common fear about tall wooden buildings is that in an earthquake, they’d tumble like Jenga blocks. Robinson’s team designed Framework’s CLT panels to rock back and forth with seismic waves, and subjected the panels to extensive strength testing. [6]

Mass timber’s biggest advantage may be environmental. Buildings are by some estimates responsible for a third of global greenhouse-gas emissions. Much of a building’s carbon footprint results from its lifetime energy use, but another big part derives from its construction. The manufacture of concrete and steel accounts for an estimated 10 percent of greenhouse-gas emissions. Trees, however, are “carbon sinks”—they absorb and hold carbon until they decompose or are burned. According to a study in the Journal of Sustainable Forestry, substituting wood for other materials used in buildings and bridges could prevent 14 to 31 percent of global carbon emissions. (This assumes that forests regrow, and that wood is reused or disposed of responsibly at the end of a structure’s life.)

Building this way has local benefits, too. It speeds up construction, because many components are prefabricated—Albina Yard’s parts were assembled [7] in five weeks. It uses a resource that can be grown nearby, and it creates local jobs: Most of Framework’s mass timber will be sourced locally.

The Northwest has a long history of wooden buildings, stretching back to American Indian plank houses, and Robinson considers Framework a part of this tradition. He also sees parallels between wood’s revival and the farm-to-table movement. Thirty years ago, he says, we ate without much thought about how our food was grown. Now “people want to know where their food is coming from. And I think that interest is starting to happen in architecture.”