By Kiersten Ahrns and Robyn Whitney
Cross-laminated timber (CLT), a wood panel product made from layers of lumber stacked at 90-degree-angles, is gaining market share in the construction world. The durable, cost-effective, and environmentally sound material is a viable alternative to more traditional building materials, and pending what looks like a forthcoming policy change, could be the future of building construction in the United States.
“Mass timber is a new category of wood product that will revolutionize how America builds,” said Robert Glowinski, American Wood Council President and CEO. “Beyond its aesthetic qualities, wood is among the most energy-efficient and environmentally friendly of all building materials. Wood products store carbon, keeping it out of the atmosphere indefinitely, thereby reducing a building’s environmental footprint.”
CLT resists compression and is exceedingly strong, even when subjected to fire, earthquakes, and explosions. When a seven-story CLT building was tested on the world’s largest shake table in Japan, it survived several consecutive earthquake simulations with almost no damage, performing just as well as concrete and steel buildings. In terms of fire, CLT does not burn easily due to the wood’s thick properties — in particular, low density and high permeability — which serve to insulate and protect the wood. Imagine trying to start a campfire by lighting large logs on fire — it doesn’t work. When subjected to fire, large-panel wood like CLT will char on the exterior leaving the interior structurally sound, whereas steel will absorb the heat and deteriorate faster.
CLT is cost-effective. CLT panels are prefabricated and assembled to size off-site, so CLT building projects can be completed in half the time of projects that rely on traditional construction materials. Additionally, the pre-made panels mean jobsite construction waste is virtually eliminated and construction noise and traffic impacts are lower. Reseachers have found that job safety on CLT building sites is also dramatically increased, and reduced installation costs by up to 50% compared to other plate materials.
CLT offers an environmentally sustainable alternative to traditional building materials. CLT production does not require burning fossil fuels like traditional building materials. In fact, CLT buildings sequester carbon, and the overall carbon footprint for a CLT building is up to 75% lower than traditional constructed buildings of the same size. CLT also provides opportunities to improve forest conditions by creating markets for the wood removed from overstocked forests, all while creating jobs and sustaining rural communities.
CLT production is currently concentrated in the Northwest with major companies like DR Johnson and SmartLam leading the way, but that’s expected to change. In addition to Katerra and Vaagen Timbers’ plan to open CLT production facilities in Washington state next year, International Beams recently opened a 227,000-square-foot factory in Alabama. Montana-based SmartLam and LignaCLT Maine LLC also plan to open new manufacturing facilities in Maine, and Sterling Lumber of Chicago is building a large CLT production facility in Lufkin, Texas.
One of the biggest obstacles in using more CLT in North American construction has been international and municipal building codes. Right now, fire and building codes often cap wood commercial buildings at six stories and wood residential buildings at five stories. This week, the International Code Council (ICC) preliminarily approved a proposal to include wood buildings up to 18-stories-tall in the 2021 International Building Code, effectively allowing high-rise CLT construction. The ICC will make its final decision to approve the proposal in December, but Thursday’s announcement has CLT advocates hopeful.
In the meantime, the City of Portland is leading the way in implementing mass timber projects. Carbon12, a 12-story CLT building, and Albina Yard, a four-story office building were both finished last year. In Milwaukee, T3, a seven-story commercial building opened in 2016 and a 21-story apartment tower is planned for 2020. In Chicago, a six-story office building is in the works, and in Newark, developers have announced plans for an 11-story office space.
“The widespread use of CLT translates to big benefits for builders, communities, and the environment,” said Rick Cantrell, staff for the NASF Forest Markets Committee. “NASF is committed to helping maintain and expand markets for CLT and other forest products and expects to see many more mass timber buildings in the near future.”
Robyn Whitney is NASF’s policy director and can be reached at rwhitney@stateforesters.org. Kiersten Ahrns is NASF’s 2018 Fall James Hubbard Intern for Policy and Communications. She can be reached by email at intern@stateforesters.org.