Cross-Laminated Timber
These days, the hottest topic in wood research and development (R&D) is CLT, a technology that originated in Europe and is continuing to gain popularity. As things exist today, traditional wood can be used in constructing buildings up to four stories high. However, CLT—if properly manufactured and used—could allow for wood-based buildings to reach from five to even 20 stories tall. Should CLT gain acceptance and popularity in the U.S., a tremendous number of new markets and opportunities would become available for building materials dealers and their customers.
“The system was developed in Austria,” says Stephen Shaler, Ph.D., professor and director of the School of Forest Resources, and associate director of the Advanced Structures & Composites Center at the University of Maine. “CLT can compete with concrete for high-rise structures and would definitely represent new market opportunities for wood products. There are already a couple of manufacturers in Canada.”
Currently, Dr. Shaler and his colleagues are starting to develop research projects and structural composites related to CLT. One project, in conjunction with the Northeastern Lumber Manufacturers Association (NELMA), will look at Norway spruce. “This is one of the most important species in Europe, but it was also planted in the Maritime provinces of Canada and the Northeast U.S.,” he says.
While Norway spruce has been used for pulp, it’s never been tested for use as structural lumber. “We are hoping that our research over the next year or so will show that it can become part of the SPF grade,” Shaler says.
Researchers are investigating Southern pine and some of the Canadian species, as well as Douglas fir, for CLT suitability. “However, we are interested in seeing if Norway spruce can also qualify,” he says.
West Virginia University is also conducting research on CLT. “We are specifically looking at using low-value, lower quality hardwoods that might otherwise be left in the woods because there wouldn’t be enough value to pull them out for saw logs or veneer logs,” says David DeVallance, Ph.D., assistant professor and program director, Wood Science and Technology, Division of Forestry and Natural Resources, at West Virginia University. “CLT is gaining interest in the U.S.,” he says. “In fact, a large residence is being built in West Virginia out of CLTs that have been imported from Europe.”
DeVallance and his colleagues are looking at the adhesion properties of these types of hardwoods for making CLTs. “Each varietal of hardwood has different adhesion properties,” he points out. They expect positive results from the research and they’re also looking into U.S. building codes and their implications for CLT, especially as they relate to fastening systems and connection designs.
According to Patrick Donahue, director of Market-Oriented Wood Technology, Natural Resources Research Institute, at the University of Minnesota, the CLT market has some real upsides. However, he believes that the way it is manufactured may be headed in the wrong direction. Donahue cites information from an extremely large European–based CLT manufacturer. “My source tells me that the big master panels are not the way to go,” Donahue says. “They say it makes more sense to build logical components.”
Though Weyerhaeuser doesn’t currently manufacture CLT, the technology is on the company’s radar. “There is a lot of discussion and research going on in this area,” says Allan Bradshaw, director, Wood Products R&D. “It seems to have some fascinating opportunities for wood. However, at this point, we don’t have any direct investments in it.”
