Wood you? New tech may help timber industry
RIDDLE, Ore. — John Redfield watches with pride as his son moves a laser-guided precision saw the size of a semi-truck wheel into place over a massive panel of wood.
Redfield's fingers are scarred from a lifetime of cutting wood and now, after decades of decline in the logging business, he has new hope that his son, too, can make a career shaping the timber felled in southern Oregon's forests.
That's because Redfield and his son work at D.R. Johnson Lumber, 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.
“We believe that two to five years out, down the road, we could be seeing this grow from just 20 percent of our business to potentially 60 percent of our business,” said Redfield, D.R. Johnson's chief operating officer. “We're seeing some major growth factors.”
From Maine to Arkansas to the Pacific Northwest, the material is sparking interest among architects, engineers and researchers. Many say it could infuse struggling forest communities like Riddle with new economic growth while reducing the carbon footprint of urban construction with a renewable building material.
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.
But challenges remain before CLT becomes as common in the United States as it is in Europe and Canada, and not all builders are sold.
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 under way on critical questions of how these buildings withstand fire and earthquakes in high-seismic regions.
Building codes in Oregon allow cutting-edge designs using new technology like CLT in some cases, but only after rigorous testing and an intensive approval process. That can make such projects cost-prohibitive, said Peter Dusicka, an engineering professor at Portland State University.
