Cross Laminated Timber: ‘The greatest thing since sliced wood’Posted: January 4, 2018
Source: The Daily World by DAN HAMMOCK
Cross laminated timber, or CLT, is being touted as a revolutionary and environmentally friendly building material that can support structures reaching 12 stories and potentially higher, and could a game-changing economic factor that timber communities have been looking for since the industry began to decline three decadesago.
“It’s the greatest thing since sliced wood; that’s my tag line,” said former state senator Brian Hatfield, Gov. Jay Inslee’s personal pick as his go-to guy for studying ways to breathe life back into the state’s wood products industry.
CLT’s potential economic impact on a timber area like the Twin Harbors is not lost on Hatfield, or 6th District Congressman Derek Kilmer, a Democrat from Gig Harbor.
“God knows we’ve got proximity to the natural resource base,” said Kilmer. “This has the potential to be a real win-win for the area; certainly a win for the economy. The timber industry has been around a long time. We’ve taken some shots to the chin over the last few decades, but I think this provides an opportunity to have the Olympic Peninsula” take the initiative and show the world that timber towns can be relevant, and innovative, in the 21st Century.
What is CLT, and what makes it such a promising alternative to more traditional wood and steel – and even heavy timber – construction?
The CLT Handbook, produced by Canada-based FP Innovations in 2013, describes cross laminated timber as “several layers of lumber boards stacked crosswise (typically at 90 degrees) and glued together on their wide faces and, sometimes, on the narrow faces as well.”
CLT can be manufactured from about any time of solid wood, as long as it is adequately kiln dried beforehand. The wood is planed to a thickness that varies depending on the end use of the finished product, glued with adhesives similar to those used to make plywood, laid out in the crosswise fashion and finished with a hydraulic press. It is then cut and marked for its specific use. The Austrians and Germans developed CLT in the early 1990s. It was met with mild interest at best, but as green building initiatives gained popularity, so did CLT. Here was a building material made from a renewable resource that is said to be as sturdy, fire-resistant and seismically sound as heavy timber, concrete and even steel construction.
It gained momentum in Europe, then began to see more use in Australia and eventually Canada. As word spread of its functionality, as well as the obvious aesthetic appeal of an all wood structure, more buildings began to pop up, including the 12-story tall Forte apartment building in Melbourne, Australia, the tallest CLT high rise at the time. Structurlam, a Penticton, B.C., company, opened the first CLT plant in the western North America at Okanogan Falls in 2011 and quickly expanded to include another plant in Oliver, B.C. The first CLT manufacturing plant in the United States opened in Columbia Falls, Mont., in 2012. Smartlam has a 40,000 square foot facility that produces about a million board feet of CLT product a month and uses primarily Douglas fir, western larch, Engelmann spruce, lodge pole pine, and alpine fir — all locally sourced. In 2015, D.R. Johnson in Riddle, Ore., became the first company in the U.S. to receive official certification to manufacture structural CLT panels by the nation’s leading manufactured wood association, meaning that their CLT met standards to be used as the primary structure for buildings in the U.S. The D.R. Johnson plant can manufacture panels as large as 10×75 feet and beams up to a maximum of 20×9 inches that are 130 feet long.
D.R. Johnson’s facility is providing the CLT panels for a new Oregon Forest Science Complex at Oregon State University. “CLT panels will be integrated into the design,” said Nick Houtman, Assistant Director of Research Communications for the university. The project has a $65 million price tag, $30 million of which will be absorbed by state bonds, approved in the governor’s capital budget in the 2015 legislative session. The complex is slated to open in 2018.
The 4,277 square foot Washington State University visitor center in Pullman is built with “a number of materials largely developed at WSU,” including cross laminated timber. According to the university’s website, “WSU’s Composite Materials Engineering Center developed the testing and grading methods used on the oriented strand board, cross laminated timbers, and glue-laminated beams that are used throughout the new visitor center. CLT was used for the gallery roof assembly, which is exposed on the interior and supported by glued-laminated beams. The 3,800-square-foot roof uses only 15 factory-cut panels, allowing for faster construction and requiring virtually no cutting or alterations on the jobsite.” The panels, which are eight feet wide and up to 32 feet long, were fabricated in Penticton, British Columbia, and trucked 300 miles to Pullman. All wood in the CLT assemblies are from Forest Stewardship Council-certified regional forests and, “unlike steel or concrete, CLT has the added benefit of sequestering carbon, since atmospheric carbon dioxide taken in by the trees remains in the finished product.”
CLT manufacturer Smartlam has provided a list of facts about CLT that answer many common questions related to the building material. For instance, what about strength and stability? According to the company, CLT panels outperform anything currently available in the USA. As for earthquake resilience, researchers have conducted extensive seismic testing on CLT and found it performs exceptionally well, particularly in multi-story applications. And CLT panels have excellent insulator qualities. “The solid panels mean nearly zero air infiltration into the building envelope. Interior temperatures of a finished CLT structure can be maintained with just one-third the normally required heating or cooling energy.”
CLT appears to be environmentally sound as well. Wood is of course a renewable resource, and according to Lemke, studies consistently show that wood outperforms steel and concrete in terms of embodied energy, air pollution and water pollution, and engineered wood manufacturing requires significantly less energy to produce than concrete and steel.
The way CLT products are put together makes them attractive to builders and to properties near construction sites.
“A lot of people want to call it “pre-fab,” but I think it’s a little more hi-tech and fancier than that,” said Hatfield. “The panels are made as the building is being designed and everything is showing up at the construction site numbered and ready to be put together. I actually think for some of the urban backfill – taller construction that needs to take place to house denser populations in urban areas with dwindling space for building – it is going to be a lot more acceptable because the construction is so quiet and quick.”
While Europe, Canada and Australia have been quicker to accept CLT as a safe, durable and attractive building material for large structures, the U.S. has been a little slower in providing clear standards for builders. The Engineered Wood Association based in Tacoma, in conjunction with the American National Standards Institute, recently released “The American National Standard for Performance-Rated Cross Laminated Timber,” a document that should help builders and those who pass building code regulations see the product is indeed an acceptable – and in some cases preferable – alternative to more traditional materials.
“We had an architect from London come and speak to one of our groups about building with CLT in the U.K.,” said Hatfield. “He told me as of the first of the year there were about 520 buildings that utilized CLT in the U.K. We then sat with the mayor of Seattle, Ed Murray, and the first question the mayor had was about fire.”
As one would expect when talking about construction using a wood product, fire is often the first concern that comes up when promoting the use of CLT.
“This architect, Andrew Waugh, lectures all around the world about CLT,” said Hatfield. “His answer was, well, they’re consolidating a lot of the old fire stations in the U.K., closing down the smaller ones and building new facilities — building them out of CLT. So if it’s good enough for fire halls, it’s probably good enough for commercial and residential construction.”
(This is part one of a two-part series on CLT. The second installment will feature the potential economic impact a cross laminated timber production facility could have locally, and what steps are being taken by industry and government leaders to encourage investment in such an enterprise)