Wood has been a staple in building single-family homes and apartment complexes of up to 85 feet in height for decades.
But the developer of one mixed-use building in Portland, Ore. is looking to change that as part of a burgeoning trend among developers and designers across the U.S. to bring the use of wood to new heights in commercial real estate.
The Framework project, which received approvals over the summer and is slated to begin construction next year, will stand at 12 stories, or 148 feet, tall—63 feet above what’s currently allowed by building code and a record for the United States. It will be constructed out of a mass timber product called cross-laminated timber (CLT), which only a small number of manufacturers in the U.S. can supply. There is also an effort to incorporate mass timber products into new code regulations to build taller structures.
The building received approvals through a rigorous state and local vetting process, and CLT so far appears to hold up to safety and fire testing, says Anyeley Hallova, a partner with the project’s developer in Portland. Hallova hopes the structure, which will house businesses with social missions as well as a retail component and affordable housing units, will help to grow the mass-timber movement.
“We see this project as a catalyst to show that it’s possible,” Hallova says. “And that will obviously trigger a demand, which will influence supply.”
CLT is lumber that is stacked in orthogonal layers, then glued and pressed together to create a material that can be used in the structural components of buildings, such as floors and wall panels, says Andre Barbosa, a structural engineering professor at Oregon State University who has conducted testing for the Framework project. Currently, 12 stories—the height of the Framework project—is likely as high as builders can go using CLT for walls and floors, Barbosa says. But buildings can be taller if CLT is just used for floor systems, he notes, citing the 18-story student residence at the University of British Columbia in Vancouver. That building uses reinforced concrete for its walls and CLT for its floor panels, Barbosa says. The material has been used in Europe for about two decades—and about eight years in Canada—but the push for more wood in U.S. construction stemmed from an oversupply of the product in neighboring Canada, as well as a desire to bring more jobs to rural areas of the Pacific Northwest, hurt by a dwindling timber industry, he adds.
WoodWorks—Wood Products Council, a non-profit that is supported by the wood industry and the U.S. Forest Service, has seen a big increase in mass timber products over the past few years, says Jennifer Cover, the council’s president and CEO. “The growth and interest from the design community has been exponential over the last three to five years, and we expect that to continue,” she notes. In downtown Minneapolis, the T3 building, an office building being developed by Hines, marks the first tall wood building in the U.S., built last year at seven stories tall. So far this year in the U.S., there have been 27 projects that WoodWorks has assisted on that utilize mass timber products that have gone into construction, and there are 227 more projects using WoodWorks’ assistance in the pipeline, Cover notes.
The pros to building taller with wood
The material boasts several benefits, including environmental sustainability, construction ease and aesthetic value, which may lead to cost savings down the road, advocates say.
Mass timber products are more environmentally friendly than fossil-fuel intensive alternatives, says Cover. There is a “wood-use paradox,” where using trees from properly managed forests improves the health of the forests, she says. Trees absorb carbon from the atmosphere as they grow and retain that carbon when the wood is used in buildings. Mass timber products, Cover notes, essentially create a high-value end product out of renewable material with a smaller diameter, and therefore lower value. “Environmentally, it’s a very positive approach,” she says.
Typically, CLT projects are constructed in a panelized system, says Christopher Evans, an operations manager with Swinerton Builders in Portland. Prefabricated panels are created off-site and then reassembled on-site, but in rare cases, CLT panels can be procured as larger panels and cut on-site. This can lead to speedier construction times, mass timber advocates say.
Lendlease, a multinational property developer, owner and builder, opened the country’s first CLT hotel, the Candlewood Suites on Redstone Arsenal in Alabama last year. The project saw a 20 percent faster completion time and was constructed with 30 to 35 percent less workforce, says Ben Symons, general manager of communities and infrastructure at Lendlease.
The four-story hotel, Lendlease’s first U.S. project built of CLT, was a partnership with the U.S. Department of Defense as part of the Privatization of Army Lodging Program. For Lendlease, using CLT for this project was cost-competitive to light gauge steel frame systems, which had been used in other Lendlease hotels, Symons says.
There were other benefits as well, including greater safety measures for the project’s builders because of the panelized system of construction and reduced energy consumption over the long term, Symons says. Now the company has three more four- and five-story hotels either under construction or in the final stage of design in New York, South Carolina and Washington. Lendlease is also considering using CLT to build other property types. “From a business perspective, CLT is a product and an initiative that we’re very invested in,” Symons says. “There’s a real, potential market in it that’s complementary to the other types of construction that we do.”
Elsewhere in Oregon, Swinerton Builders is overseeing the construction of the largest-known building that uses cross-laminated timber, according to ENR Northwest. The project, which will house the corporate offices of First Tech Federal Credit Union Oregon, will be 156,000 sq. ft. in size and five stories high.
As with any new material, there is a learning curve to building with CLT, Evans says. But it has little to do with actual construction—in many ways, the process is not too different than using precast concrete or structural steel—and more with procurement and planning. In other words, it comes down to understanding the supplies on the market, what they can do and what risks are involved, Evans says. While the number of CLT manufacturers is growing, there are not many in the U.S. or Canada—there is one in Oregon and another in Montana. Procurement time can also take longer, as much of the preparation work is done beforehand—all factors that need to be calculated in advance to make mass timber projects more cost-effective, he adds. “It’s still a process that has to be managed and it’s a potential risk,” says Evans, who adds that Swinerton has other CLT projects in the pipeline.
While Framework was in part supported by funds awarded through a national design competition and some foundations devoted to social projects, Hallova says there are still cost premiums attached to building something with a new product—which would be expected with any new product. But she notes there are other savings that will be realized in the end, such as a quicker construction timeline. “I think there are a lot of opportunities for the industry, but it’s going to take some time for the material to become cost-competitive at a larger scale,” Hallova says.
One advantage with mass timber products that advocates say may not have a dollar figure attached to it—aesthetic value. Increasingly, the public is looking for sustainable and renewable resources in construction, and—especially in the Pacific Northwest—there is a strong appeal for natural, exposed wood buildings, says Juliana Ruble, program administrator of the TallWood Design Institute of Oregon State University. This is especially true in dense cities, where people want to feel connected to nature. “More and more, our public is really looking for that kind of a feel in the spaces that they live,” Ruble says.
Hallova also expects that people will be drawn to the high quality material and the aesthetic of the project. “Whether that brings high rents now or in the future remains to be seen,” she notes.
But is it safe?
Not everyone has bought into the concept of using wood to build taller structures. The National Ready Mixed Concrete Association in 2016 launched Build With Strength, a campaign that seeks to warn of the dangers of building taller structures with any wood or combustible material, arguing that materials like concrete and steel are far safer. Some of the members of the coalition include firefighting associations, local fire departments and the Steel Framing Industry Association. As the U.S. has seen an increase in light-frame wood construction, there has also been an increase in fires, says Kevin Lawlor, a spokesman for the campaign. As for CLT, these products have not been tested enough, Lawlor says. “There’s any number of better materials that people can use,” he adds.
Many of the fires that occur at apartment buildings built with light-frame wood construction happen before the building has been completed, and no fire suppression measures are in place, says Cover. Codes require all buildings—regardless of materials used to build them—to be at the same safety level. “Once it’s built, it doesn’t have the same vulnerabilities,” she says.
In May and June, the International Code Council’s ad-hoc committee on tall wood buildings tested five fire scenarios on a two-story, CLT-constructed building and they were successful, says Kenneth Bland, vice president of codes and regulations for the American Wood Council. “It performed really how we expected it to,” Bland says. A big section of wood is inherently flame-resistant, he notes. When mass timber products materials burn, they char—even after an hour of charring, there is still enough good wood within a cross section to carry a building’s load, Bland says, noting that a building’s structural elements are also overdesigned to anticipate the char forming and reducing the amount of wood available to carry the load. During a fire, steel can quickly elevate in temperature and begin to deform, and concrete can spall—when trapped moisture expands as it turns to steam, causing pieces of concrete to explode and shoot off, he adds.
For years, glue-laminated beams have been allowed in construction, but now the committee, which has been meeting since 2016, is working to change the International Building Code to allow mass timber products to be used to build taller structures, Bland says. Next year, the committee plans to consider changes to the code, which would go into effect in 2021. “That’s why we’re going through this code development process, so that we do address those safety issues that may be raised,” he says.
How the material performs in earthquakes is also being studied, and so far to positive results, Ruble says. Her program, which formed two years ago to focus on the research, education and testing of mass timber products, has about $2 million invested in testing CLT, and about a third of that is specifically related to seismic research, she says.
The Framework project—the tallest in the U.S.—was able to bypass code to get approvals from the state and local levels by following a performance-based path, allowable in Oregon, Hallova says. The team had to prove—several times—that the project meets the same fire and safety standards as structures built with other materials. Once the project is completed, teams of researchers will also study the building to glean more information about how mass timber functions in taller structures. “Were pushing the technology and the research above what has been done in the past,” Hallova says.