Americans often take their fashion cues from Europe; what's hot there can make its way across the pond within weeks. By contrast, European innovations in building materials move more like a glacier than a tsunami. But one idea that has started winning over builders there in the past few years is already generating excitement here: cross-laminated timber (CLT) construction.
CLT is similar to plywood in that it is made from layers of wood glued together. But unlike plywood, where the layers are thin and typically oriented in the same direction, CLT layers are made from much thicker slabs of solid-sawn lumber that are set down in layers at 90-degree angles to each other. Typical CLT blocks are 4 to 12 inches thick and easily can top 25 feet in length.
CLT was used most famously three years ago to construct The Stadthaus, a nine-story apartment building in London. It weighed less than concrete, required fewer workers, and went up much quicker than a traditional steel and concrete building, Stadthaus' architect says. Since then, more than 100 CLT buildings have been constructed in London alone, says Cees de Jager, executive director of the Binational Softwood Lumber Council, a Vancouver-based group set up in part to promote increased use of wood in construction. England also has seen CLT used to construct schools and other buildings throughout the country. And in continental Europe, CLT has been used in several dozen other multi-story buildings, particularly in Scandinavia and Austria.
In America, what is touted as the nation's first use of CLT can be found in Gastonia, N.C., where a 78-foot church bell tower was built from the stuff last fall. The work was the result of a joint venture between the National Center for Sustainability and MDS10 Architects.
The tower was put together in less than a week using prefabricated CLT imported from Austria. It's so sturdy it can stand up to a 90-mile-an-hour wind and only move half an inch, says Woodworks, an organization devoted to promoting the use of wood in residential and commercial construction.
Cross-laminated timbers could make it possible for wood's champions to compete against steel and concrete contractors for the right to build multi-story and commercial buildings on this continent.
CLT offers several upsides that could help it in the American market. The first is its strength. Recent tests have found that buildings constructed with CLT can withstand earthquakes.
"The product has been developed between Italy and Japan as something that can potentially withstand seismic events," says Lech Muszynski, an associate professor at Oregon State University (OSU) who is heading a pilot program to research CLT. "The tests have been very successful. This also has a lot of potential for places that are hit with tornadoes and stuff, and there is lots of structural integrity in [CLT] buildings."
CLT's North American advocates also are likely to tout its green advantages, given that it's made from wood.
Then there's its fire resistance. CLTs are so dense that, during a fire, the wood chars more than it burns. Tests have shown it can withstand flames and remain standing far longer than most fire standards require.
OSU's research, which began as a pilot program last summer, aims to test the strength, energy efficiency, and usability of cross-laminated timbers.
It also is looking into manufacturing techniques, including the search for bonding methods that will work best on wood species found in Oregon. (European CLT is made predominantly from spruce.)
"Our plan is to expand [the research] and help local investors to enter this market," Muszynski says. "... In the [U.S.] there are a couple of companies that are trying to launch the manufacturing of CLT, but there are none that
I actually know of that currently manufactures this material. They are kind of measuring themselves to the market and trying to find manufacturing processes for them."CLT's potential in North America also has been hamstrung by the lack of building codes or standards that support the material's use. In particular, most building codes in North America bar the use of wood for projects of five stories or more.
APA-The Engineered Wood Association (APA) is working on a standard for CLT that will be submitted to the American National Standards Institute. Work on that standard is 90% complete, says APA's market communication director, Marilyn LeMoine. This standard would cover the manufacture, qualification, and quality assurance requirements for cross-laminated timber.
Being able to enter the multistory construction market with CLTs could help boost sales prospects for dealers and mills alike without requiring too much of a stretch in dealer training or mill equipment. After all, use of engineered wood products in America has risen by 7% to 8% each of the past seven to eight years, notes Dennis Huston, general sales manager at Boise Cascade. And in that same time, the use of engineered wood products in framing material has increased about 50%, he says.
As with engineered wood, when it arrives, CLT is likely to win favor first with firms that create and builders that use wall and floor panels. In Europe, CLT buildings typically arrive at the jobsite prefabricated. Assembly at the building site by special crews makes construction simple.
While the products have been a little slow to catch on in America, companies in Europe have found some success in marketing CLT products. One group of companies, Stora Enso of Helsinki, Finland, has begun marketing and selling CLT buildings around the world. Aside from promoting the product, the company also produces and assembles CLT buildings.
Wood's Next Big Thing Is Real, Real Small
The wood industry has launched an Invisible Revolution, one that could see timber interests win back some of the building products market it conceded to plastic in recent decades.
It's invisible because it's taking place at nanometer scale, using objects so small that thousands could stretch comfortably across the width of a human hair. Already, nano-sized particles are helping stains and paints go deeper into wood than ever before and making it possible to invent new products, such as transparent paper.
Douglas Gardner, a professor of wood science at the University of Maine, said nanocoatings also could help improve wood's resistance to scratches and abrasions, as well as provide a way to incorporate sensors into wood.
Gardner was among scientists from around the world who came to Madison, Wis., last month for a conference that devoted a day to nanotechnology. Among the speakers, Carol Clausen of the U.S. Department of Agriculture's Forest Products Laboratory said adding certain nanomaterials to wood proved substantially better than current products in resisting termites, limiting fading from the sun, and stopping leaching into water.
Researchers are working on ways to employ nanomolecules to release biocides at certain temperatures and/or humidity levels. Experiments involving fungus-killing biocides on OSB, MDF, and gypsum board already have produced good results, Clausen said.
Scientists also are figuring out how to extract lignin–the substance binding wood cells–and turn it into a source of carbon nanostructures. The resulting nanotubes are extremely stiff and strong.
Between what nanotechnology can do when it's put in wood and what can be created when nanomolecules are removed from wood, timber interests could see big changes ahead, Gardner believes. "We want to take the sawmills and move them to the nanomills," he says.— Craig Webb