In theory, developers could propose larger CLT buildings before codes are changed, but they would have to invest time, money and coordination to get this new building type through Seattle’s Department of Construction and Inspections, with no guarantee that their designs would be approved. “It takes a very special project and specific client and certainly a very ambitious design team to take it on,” says Mayo.
Unless that client steps forward, builders will be waiting for the International Code Council (ICC) to work through the fire and earthquake issues and develop the necessary code changes before mid-rise and higher CLT buildings spring up in the city.
“We know there’s been a lot of interest in this construction type,” says Stevens, “so we’re trying to be responsive to the demand without giving up safety.”
As with so many innovations, another problem for developers is that material costs for CLT can be high because there are so few North American CLT manufacturers. Developers wait for the price to go down, but manufacturers need more demand for a product. To alleviate this problem, some businesses and legislators are working to help bring CLT mills to Washington state. An Oregon lumber company, D.R. Johnson Lumber, in Riddle, Oregon, recently became the first certified manufacturer of CLT for construction material in the U.S.
Clt was developed in the 1990s by researchers in Austria and Germany who were looking for a use for pieces of surplus wood. The material is created by layering smaller pieces of wood together into a kind of sandwich that offers the strength and insulation found in the massive timbers of the past, and that can be used for the walls, floors, roof beams and posts that make up a building.
One of the most touted aspects of this material is its role in fighting carbon emissions. Trees absorb carbon and use energy from the sun to grow, which makes them a lower carbon choice than concrete or steel, which not only don’t absorb carbon, but require much more carbon-emitting energy to manufacture. Trees are also a renewable resource, as long as they are harvested from a sustainably managed forest. And CLT can be made from otherwise underused or damaged woods, such as the vast forests of domestic pine that have been killed by mountain pine beetles.
Another selling point, particularly in urban areas, is that CLT panels are prefabricated—bring them to the building site, and your building goes up quickly, with less noise, pollution and traffic delays than with other materials. The eight CLT stories of London’s nine-story Murray Grove apartment building went up in nine weeks.
But building with CLT is not all about practical considerations, says Susan Jones, who owns the Seattle architecture firm Atelierjones and designed her family’s home as the first (and so far only) CLT home in Seattle’s Madison Valley in 2015. The material itself—in the case of her house, CLT primarily from white pine and left unpainted—is a sensual pleasure, from the quality and patina of the wood to the subtle pine smell in the house.
“It’s been incredibly satisfying to live with it,” Jones says. “That’s what architects are asked to do—we create beautiful spaces for people. What’s better than to immerse yourself into this incredibly rich natural environment of wood?”
Here in Washington, there’s enough raw material to immerse us all in that environment. But only a handful of projects in the state have used the material so far—for example, in Jones’ CLT house, in the walls of the Bellevue First Congregational Church sanctuary designed by Atelierjones and on a building project at Washington State University in Pullman. In Oregon, Joe Mayo recently worked on the design for what is to be the first use of U.S.-made CLT on a two-story building project, using panels manufactured by Oregon’s D.R. Johnson.