Skip Navigation
Seeing forests and trees Stephen Shaler is on cutting edge of composite product development by Beth Staples | Photography by Adam Kuykendall

University of Maine wood scientists and engineers are evaluating the performance of cross-laminated timber (CLT) made from solid-sawn and composite lumber from trees grown in Maine and the northeastern U.S. In the 1990s, CLT was developed in Austria as an alternative to stone and concrete. It was recently incorporated in the International Building Code and can be used in building construction in the United States, providing it meets manufacturing standards. It has been described as plywood on steroids.

As a Boy Scout, Stephen Shaler enjoyed camping in the woods and figuring out how things worked. In the 1970s, the environmental movement captured his imagination, particularly as it related to forestry and sustainability.

Today, the University of Maine wood scientist who lives lakeside in a forest setting researches how wood products are made and how they can be improved. He says it’s rewarding to be at a university where forestry is valued and research makes a positive difference in people’s lives.

“Forests are really important to everybody in this world; it’s one of most important ecosystems — it’s important to animals, it’s important to water and it’s also important for the products that it gives,” says the director of the School of Forest Resources.

“If you’ve got a sustainably managed forest, there’s nothing more environmentally responsible than using that forest to make things for people, for society. That’s not all forests are for but that’s certainly one of the things.”

Stephen Shaler

For Stephen Shaler, director of UMaine’s School of Forest Resources and associate director of the Advanced Structures and Composites Center, science is a way to improve products and provide innovative, sustainable solutions.

Shaler is the principal investigator for two projects that involve testing wood and composite materials to determine if they’re suitable for building construction.

One project is a collaboration with the Northeastern Lumber Manufacturers Association (NELMA). After getting feedback from NELMA about what research would help the industry and forestry managers, UMaine won a $300,000 grant from the U.S. Department of Agriculture. The competitive grant includes testing wood from trees that members of the Civilian Conservation Corps (CCC) planted during the Great Depression.

In the 1930s and ’40s, the CCC — formed by President Franklin Delano Roosevelt to provide jobs and promote conservation — planted seedlings of Norway spruce, a species native to Europe. The species adapted to soil conditions and grew relatively quickly in the Northeast climate, says Russell Edgar, wood composites manager at UMaine’s Advanced Structures and Composites Center.

Those trees now top 80 feet and are ready to harvest.


Read transcript


While Norway spruce has long been approved for construction in Europe, it must be approved in the U.S. as well because of climate and soil differences. So at UMaine’s accredited testing laboratory, researchers assessed Norway spruce to see if it met U.S. industry standards.

They employed destructive testing — bending, tension, compression and shearing — to learn the strength values of about 1,200 pieces of lumber milled from Norway spruce grown in Maine, Vermont, Wisconsin and New York.

If the lumber meets industry standards, it will be included in the Spruce-Pine-Fir South grouping of species for construction-grade dimensional lumber.

Preliminary evaluation results look promising, says Shaler, an associate director of the Composites Center and professor of wood science.

This is the first new U.S. species to be tested in over 80 years. There aren’t a lot of new species available for construction material, so historically, it’s very significant on a lot of fronts.”
Jeff Easterling

Jeff Easterling, president of NELMA, says being able to introduce Norway spruce into the lumber market is nearly a once-in-a-lifetime opportunity.

“It’s a big deal. This is the first new U.S. species to be tested in over 80 years. There aren’t a lot of new species available for construction material, so historically, it’s very significant on a lot of fronts,” he says.

It’s gratifying that efforts undertaken in the Depression-era could prove to be a boost for today’s economy, Easterling says.

“We’re reaping benefits of what they (CCC) did,” he says. “It opens up a broader wood basket for mills in the Northeast.”

Jethro Poulin, sales manager at Milan Lumber Co., in New Hampshire, and Alan Orcutt, mill manager at J.D. Irving’s Dixfield Sawmill in Maine, say more lumber translates into added hours for workers, increased production and potentially more jobs.

Having a larger supply of lumber also could enhance East Coast mill operations’ ability to compete, says Orcutt, a UMaine graduate. And if Norway spruce passes the tests, private landowners will be able to sell their timber.

In addition to the economic boost, UMaine students have benefited from taking part in the testing.

Benjamin Farber, a UMaine undergraduate from Danbury, Connecticut, says being a project research assistant has been one of his best academic experiences.

Norway spruce test

University of Maine scientists and students in the Advanced Structures and Composites Center evaluated strength values — including bending and tension — of about 1,200 pieces of lumber milled from Norway spruce that grew in Maine, Vermont, three regions of New York and Wisconsin. The wood is from some of the 3 billion trees the Civilian Conservation Corps planted during the Great Depression that have grown up to 100 feet in height, with diameters of up to 26 inches.

“I’m learning a lot about the mechanical properties of wood — this is basically my entire field put into this one trial and I’m able to learn step-by-step what’s going on and why it is important to my field,” says the forest operations, bioproducts and bioenergy major who’s concentrating in wood science.

In a related project, Shaler and colleagues evaluated the performance of cross-laminated timber (CLT) made from solid-sawn and composite lumber from trees that grow in Maine and the northeastern U.S.

CLT is sometimes referred to as plywood on steroids.

The plywood product consists of two-by laminated lumber or composite — two-by-fours, two-by-sixes, or two-by-eights — stacked at right angles — with as few as three and as many as nine laminated layers — and bonded with an adhesive.

The strong, stable panels are used as full wall segments, as well as in floors and roof systems. The massive timber construction product — developed as an alternative to stone and concrete in the 1990s in Austria — is used in homes and mid-rise commercial buildings in Europe and Canada.

In Europe, CLT has had building code approval for a couple decades. Shaler says CLT structures of 10 or so stories have been built there, and designs have been made for a 60-plus-story CLT and steel building. In Italy, CLT buildings have been erected because of their demonstrated structural integrity during earthquakes, he says.

And since CLT was incorporated in the 2015 International Building Code, it now can be used for construction in the U.S., providing it meets manufacturing standards.

Testing Norway spruce

The Advanced Structures and Composites Center has an ISO 17025-accredited testing laboratory that is a valuable resource to collaborators such as the Northeastern Lumber Manufacturers Association. Norway spruce was tested to determine if it meets industry standards and can be included in the Spruce-Pine-Fir South grouping of wood species for construction-grade dimensional lumber. Preliminary results look promising, say UMaine wood scientists.

Two firms in the West are approved for manufacturing CLT made with Douglas fir and larch — tree species native to that region, Shaler says.

Enter UMaine to test how CLT made with tree species that grow in Maine and the northeastern forests of the United States fare. University scientists are evaluating the strength, thermal and moisture properties of CLT made with Spruce-Pine-Fir South.

Provided Norway spruce passes U.S. industry standards, it, too, will be part of the Spruce-Pine-Fir South grouping. Pleasant River Lumber in Dover-Foxcroft, Maine has provided the SPF-South lumber for testing.

UMaine also is testing a hybrid CLT panel made from a combination of solid-sawn SPF South lumber, as well as an engineered wood composite — laminated strand lumber (LSL) — produced by Louisiana-Pacific in Houlton, Maine.

In summer 2015, UMaine graduate student Nicholas Willey led a student team that carefully built about 45 4-foot-by-8-foot CLT panels. They then proceeded to break the panels during tests for flexure, shear, block shear, delamination and fatigue.

Willey and Shaler are collaborating on the project with colleagues in a variety of fields, including Edgar; Bill Davids, professor of civil engineering; Doug Gardner, professor of forest operations, bioproducts and bioenergy; Roberto Lopez-Anido, professor of civil engineering; Robert Rice, professor of wood science; Mehdi Tajvidi, assistant professor of renewable nanomaterials; and Jaya Tripathi, a master’s student in wood science.

In addition to large-scale testing at the world-class UMaine Composites Center, CLT and LSL are being examined on a smaller scale in Nutting Hall. As well as gauging a structure’s stability, Shaler says it’s necessary to know what the indoor environment of a CLT structure will be like.

That’s where Tripathi comes in. The resident of Nepal is evaluating hygrothermal movement — heat and moisture transfer — and thermal insulation value in an LSL-spruce-LSL hybrid CLT design. Sensors embedded in CLT panels measure moisture content, humidity and temperature under a variety of conditions.

If CLT made of SPF South and LSL stacks up well, that could translate into new markets and increased commercial value of forests in the Northeast.

The construction industry is interested in this building system, Shaler says, because crane operators can quickly erect prefabricated CLT structures that have had door and window openings precut at the factory.

Students working with wood material

University of Maine students build a 4-foot-by-8-foot cross-laminated timber panel. In summer 2015, they built about 45 panels then broke them during tests for flexure, shear, block shear, delamination and fatigue. Graduate civil engineering student Nicholas Willey is evaluating CLT for his master’s project.

CLT has other advantages, Shaler says, including pleasing aesthetics. CLT structures also result in a smaller carbon footprint than structures built with energy-intensive materials, such as steel or concrete.

Trees pull carbon dioxide out of the atmosphere, says Shaler. And when trees are turned into wood for lumber, the absorbed carbon remains sequestered. And after mature trees are harvested in sustainable forests, newly planted trees also remove carbon from the atmosphere.

At the University of Massachusetts, for instance, a four-story, nearly 90,000-square-foot facility being built with cross-laminated timber and a wood-concrete composite is expected to have zero carbon emissions.

Habib Dagher, founder and director of the UMaine Composites Center, says the university’s research on new uses for local wood species could open the door for a CLT manufacturer to locate a plant in the state.

“We are now exploring opportunities to build a pilot CLT building in Maine, a project that will bring together Maine architects, engineers, contractors and wood suppliers to build this expertise in Maine,” he says.

Back to top


Back to the Spring-Summer-2016 Issue