Builders of wooden construction projects are looking up.
While lumber has traditionally been the material of choice for low-rise buildings, architects and engineers are increasingly looking to it for vertically oriented projects, experts say.
“There’s a lot of investment and research into going higher,” said Matthew Church, an engineer with the Davis & Church firm.
Church and other experts recently gathered in Portland, Ore., at the Wood Solutions Fair on Oct. 15. The event was organized by WoodWorks, an organization that promotes the use of lumber in commercial, multi-family and institutional projects.
The cost advantage of using wood instead of steel and concrete has prompted more project managers to build structures 5 stories and taller with lumber, said Scott Lockyear, national director of design and construction services for the group.
“That’s a national trend,” he said.
Tall wood buildings are expected to continue growing in popularity now that a wood material new to the U.S. — cross-laminated timber — has been approved under the 2015 International Building Code, he said.
The material, commonly known as CLT, is created by gluing several panels of wood together so the grains run perpendicularly to each other from layer to layer.
As a result, the material is strong, flexible and less prone to shrinking and movement than regular wood products, said Church.
The material is already used in Europe for 8-story buildings, but it can be used for structures of 12 stories or more.
The slabs are cheaper than using concrete and steel and are also convenient during construction — their exact dimensions can be pre-fabricated off-site, Church said.
“Every little notch can be done in the shop so that very little has to be done in the field,” he said.
If on-site adjustments are necessary, however, they’re much easier to make compared to cutting concrete or torching through steel beams, Church said.
When used in conjunction with concrete and steel, this “plywood on steroids” can theoretically be used to build structures of 30 to 40 stories, depending on the design, said Nick Bevanda, architect with CEI Architecture.
“Sometimes the best solutions are the hybrid systems,” he said.
Wooden multi-story buildings were once common during the turn of the 19th Century, but large fires caused cities to adopt restrictive codes that limited the use of lumber, he said.
With modern fire detectors, sprinkler systems and emergency exits, this risk is greatly alleviated, Bevanda said. When sprinklers are activated, they’ve been found to be 97 percent effective in extinguishing fire.
“It will minimize death and property damage as well,” he said.
The perception that wooden buildings are less safe is a major impediment in public perceptions, Bevanda said.
In fact, wood can outperform concrete and steel in earthquake-prone regions because it’s lighter and more flexible, he said.
“There’s a high strength-to-weight ratio with wood,” Bevanda said. “Wood actually responds wonderfully in seismic conditions.”
The promise of materials like CLT is that they will also be competitive on price, he said.
The material can decrease costs by 10-50 percent, depending on structure design, according to WoodWorks.
“If we’re going to see buildings like this, they need to be affordable,” Bevanda said. “If I’m going to be building with wood, there can’t be a premium for it.”
Currently, there are two CLT manufacturing plants in Canada, Church said. The price for builders would be even more attractive if U.S. companies began producing it, thus reducing freight costs.
“We’re anxious for them to open up a plant here,” Church said.
Municipalities in the Northwest and elsewhere have been willing to incorporate the material into their building codes, said Kris Spickler, heavy timber specialist with Structurlam, which makes CLT.
Spickler said he expects about two or three new CLT factories to open in the U.S. within the next five years.
“I think it will become a core building product,” he said.