EUGENE, Ore. — For a growing crop of revolutionary constructions in Oregon, wood is the new steel.
The canopy of a redesigned Hayward Field is built from mass timber, a category of wood construction material that can replace steel and concrete for primary load-bearing functions. And the first deliveries of cross-laminated timber arrived a few weeks ago for construction at the University of Oregon’s Knight Campus for Accelerating Scientific Impact, where it will be used to build its mezzanines.
When the city of Springfield planned a four-story parking garage in Glenwood, hopeful designers looked to that super-strong wood. And though voters rejected a bond issue to build it, Lane County’s new courthouse would likewise have risen from mass timber products.
Mass timber — also called engineered or composite wood — is increasingly popular in construction projects across the country, but especially in the Pacific Northwest, where most of the product’s American research, manufacturing and building is concentrated.
“Economically and environmentally, it’s really a winner for the state,” UO architecture professor Judith Sheine said.
Mass timber is generally made by binding together sheets of wood, creating a kind of plywood capable of replacing steel even in high-rise buildings. Though construction with such engineered wood became popular in Europe during the 1990s, its use in the United States is new.
But using engineered timber products is catching on in large part because it’s seen as a more sustainable construction material.
Oregon is home to mass timber manufacturers, such as DR Johnson Lumber in Riddle and Freres Lumber Co. in Lyons. The state was the first in the country to change its building code to allow for timber structures higher than six stories, primarily because of mass timber’s growing popularity.
WoodWorks, which provides design assistance for wood builders, counts nearly 600 mass timber projects finished or being built in the United States since 2011. At 44, Oregon has the fourth most of those buildings behind California, Washington and Texas, respectively. Portland has Oregon’s greatest concentration of mass timber buildings.
Ethan Martin, a Woodworks regional director involved in Oregon projects, said he recently canceled a vacation because of mass timber’s popularity.
“There’s too many projects coming up,” Martin said. “I was getting four to five a day coming in.”
Martin said American builders are becoming more familiar with mass timber, counting it now as a “tool in their toolboxes.” Its advent is giving designers a new way to work, but he said there still are many too unfamiliar with mass timber to use it extensively.
“You’ll see a much grander adoption as people get more comfortable with it,” Martin said.
Cross-laminated timber, made from gluing solid-sawn lumber together, is used in more than half of all U.S. mass timber projects, according to Woodworks statistics. That’s what’s going into construction at the Knight campus, but only in parts of the building.
Vibration concerns
Sheine, director of design at the UO/Oregon State University collaborative TallWood Design Institute, said there was unease about using cross-laminated in the building’s science labs for fear vibrations through the wood might damage expensive scientific equipment. So the Knight campus mezzanines alone will be built from the mass timber product, she said.
But UO is using glued laminated timber, an older kind of mass timber product sometimes called glulam, to build the canopy going up around Hayward Field. Glulam beams are being used to sandwich hollow steel box beams for that project, Sheine said.
“Given the history of Oregon and timber, it just seemed appropriate,” Sheine said.
At OSU, the George W. Peavy Forest Science Center is being built of mass timber. But new monies are allowing designers there to reimagine a future building in wood.
Last month, the U.S. Department of Agriculture Forest Service awarded $1 million through the Mass Timber University Grant Program to 10 institutions in seven states. One was OSU, which will use the funds to decide if it can build a new arts and education complex from mass timber.
“We don’t know the answer yet,” university architect Libby Ramirez said.
The arts and education complex was born from a $25 million anonymous gift, though more funding will be needed to build it, Ramirez said. The project is in its schematic design phase, but the federal grant is letting the university go back to the drawing board.
Part of the decision will involve bringing in experts on acoustics to determine what effects a mass timber construction might have on sound quality for an arts complex, Ramirez said. Mass timber also may be able to bring down the cost of the building, she said.
“This could be a really great opportunity,” Ramirez said.
Mass timber products can be made from smaller trees because it is a composite material, something Martin said increases its long-term viability as a building material as people spend more time and energy on seeking sustainable solutions to environmental concerns.
“We’re not cutting down old growth trees,” Martin said. “Mass timber really has become a competitive product.”
Though it’s possible to use trees with a diameter as small as 4 inches, Martin said the demand for mass timber products hasn’t yet made it economically viable to harvest trees that small. But the wood felled for mass timber products still can be smaller than old growth.
Sheine said this is because wood is capable of carbon sequestration, because each piece of mass timber can be digitally manufactured to reduce waste and because a lighter building requires less concrete be poured onto its foundation.
