Cross-laminated timber made by an Oregon company continues to create buzz over its potential
John Redfield watches with pride as his son moves a laser-guided precision saw the size of a big rig wheel into place over a massive panel of wood.
Redfield and his son work at D.R. Johnson Lumber Co., one of two U.S. timber mills making a new wood product that’s the buzz of the construction industry. It’s called cross-laminated timber, or CLT, and it’s made like it sounds: rafts of 2-by-4 beams aligned in perpendicular layers, then glued — or laminated — together like a giant sandwich.
The resulting panels are lighter and less energy-intensive than concrete and steel and much faster to assemble on-site than regular timber, proponents say. Because the grain in each layer is at a right angle to the one below and above it, there’s a counter-tension built into the panels that supporters say makes them strong enough to build even the tallest skyscrapers.
Visually blemished wood that currently goes to waste can be used in the middle layers of a CLT panel without sacrificing strength or look. Supporters say it could bring sawmills back online while improving forest health through thinning dense stands and making use of low-value wood and local tree species. Trees as small as 5 inches in diameter at the top and those damaged by pests and wildfire are prime candidates.
U.S. building codes generally place height limits on all-wood buildings for safety reasons, though a special committee of the International Code Council is investigating potential changes to address the use of CLT in such structures. And research is still underway on critical questions of how these buildings withstand fire and earthquakes in high-seismic regions.
“The early adopters are looking at it and seeing it as a good opportunity,” but before CLT can take off, there will have to be more examples to get people excited and more mills producing it, said Thomas DeLuca, professor and director of University of Washington’s School of Environmental and Forest Sciences.
SmartLam in Montana is the other company producing CLT panels.
This spring, cross-laminated timber will get its ultimate test in the United States when a Portland architectural firm breaks ground on a 12-story wood building in the city’s trendy Pearl District. It would be the tallest all-wood building in the world constructed in a seismic zone and the tallest all-wood building in North America.
An all-wood building in Norway is taller, but it’s not in a seismic zone. An 18-story wood building in British Columbia is also taller, but rests on a traditional concrete core.
Lever Architecture is using $1.5 million it won in a tall wood building competition sponsored by the U.S. Department of Agriculture and the softwood industry that’s intended to promote CLT as a domestic building material. A 10-story residential tower in New York City also got $1.5 million.
The Portland firm has been working with scientists at Portland State University and Oregon State University to test the panels’ strength by subjecting them to hundreds of thousands of pounds of pressure. They are also testing various methods for joining the massive panels together.
“We’re looking at creating a resilient design, a design that could withstand a major earthquake — basically the earthquake that we all worry about — and be repaired,” said Thomas Robinson, founder of Lever Architecture.
The 125-employee company has been inundated with visitors from around country interested in touring their new CLT business expansion.