FAYETTEVILLE, Ark. (AP) — A construction method rarely used in the United States underpins a new student housing project at the University of Arkansas, Fayetteville.
Large panels of wood and glue-laminated wooden beams from a European supplier will form the main structural elements of two five-story halls built to house 710 students, said Daniel Clairmont, the university’s director of engineering and construction.
The alternative to steel framing and concrete is expected to add roughly $1.3 million in construction costs to the estimated $79 million project, with UA officials describing it as a way to possibly boost the state’s timber industry should the method — hailed as having benefits that include increased environmental sustainability — catch on widely.
“It’s an opportunity to maybe generate interest and kick-start investment,” Clairmont said.
The 202,000-square-foot Stadium Drive Residence Hall, which will consist of two halls connected by a ground-level common area, is the first U.S. campus housing project built using what’s known as cross-laminated timber, industry experts said. Despite cross-laminated timber being used in Europe and elsewhere, including for some student housing, the method remains far from commonplace in the United States, the Arkansas Democrat-Gazette reported.
The UA student housing project amounts to “basically real-time investigative science,” said Elizabeth Stokes, a Mississippi State University assistant professor in the university’s sustainable bio-products department.
Researchers, often backed with federal funds, continue to study how cross-laminated timber withstands wide-ranging scenarios like earthquakes and intense fire.
Stokes, with federal grant money, is studying how termites affect cross-laminated timber compared with other materials.
“I think that people who are willing to step up and start using materials and monitor their progress is one of the best ways that we can go about learning how to optimize these products for our specific needs,” Stokes said. Researchers are working “to learn as much as we can, as quickly as we can, because this is an exciting, interesting product that we’re very interested in.”
The safety of cross-laminated timber in a fire is not unanimously agreed to be as good as concrete and steel, but those who work with it describe intensive testing and good fire resistance.
“As engineers, we can design these type of members to resist fire and therefore meet code” requirements, said David Barber, a principal with Washington, D.C.-based engineering consulting firm Arup.
Mike Johnson, UA’s associate vice chancellor for facilities, said no one at the university thinks there is added safety risk because of the design “or we wouldn’t be building it to house students.” Concrete and steel will be used in stair towers and elevator shafts, he said.
UA’s architecture dean, Peter MacKeith, said in an email that the project “is aspirational and inspirational — and it indicates to a regional, national and international investment pool the potentials of the state to be a leader in the rapidly emerging technology.”
UA System trustees last November approved the project, with wood construction discussed as a possibility.
This fall, Chancellor Joe Steinmetz included the project among campus goals, to “use novel timber products in partnership with Arkansas’ timber industry in construction of a new residence hall.”
But no Arkansas wood will be used in the main structural components following a competitive bid process managed by contractor Nabholz, Clairmont said. The low bidder at about $5.3 million was a firm called Holzpak, Clairmont said. Holzpak is a partner with European manufacturer Binderholz Bausysteme GmbH, headquartered in Austria.
APA – The Engineered Wood Association, a trade association for U.S. and Canadian manufacturers, lists six companies in its directory as makers of cross-laminated timber, none with locations in Arkansas or neighboring states.
With the other main structural element, glue-laminated beams, “in the state of Arkansas, they have the ability to make these beams,” Clairmont said. But not to make beams large enough for the project, he added. While some bidders in North America offered to use wood from Arkansas, ultimately it was less expensive to have a European supplier, he said.
MacKeith said Arkansas wood will likely be used in interior finishes and furnishings. An advocate for timber construction since arriving at UA in 2014 from Washington University in St. Louis, MacKeith, who has worked as an architect in Finland, noted the state’s abundant forests, which cover about 57 percent of the state, according to the Arkansas Forestry Commission. UA can be a leader “to advance a market for this production,” he said.
MacKeith said the technology, which dates back to the 1990s, is in use in Europe and elsewhere, including Australia and Japan.
Stokes said cross-laminated timber is used “fairly frequently” in Austria and Germany for low-rise and mid-rise projects. Cross-laminated timber was used in framing a 72-room student residence project completed last year at Cambridge University.
UA is also building a library storage facility using a similar method, and, in Canada, the University of British Columbia this year opened an 18-story student residence hall called Brock Commons built using a hybrid of cross-laminated timber methods and concrete and steel.
Cross-laminated timber consists of multiple layers of smaller pieces of wood like two-by-fours. Pieces forming each layer are rotated to be aligned differently from the layer beneath it, said Chris Baribeau, principal architect with Fayetteville-based modus studio, one of three architecture firms on the project. The layers are glued or otherwise bonded together.
The other architecture firms are Boston-based Leers Weinzapfel Associates and St. Louis-based Mackey Mitchell Architects.
Panels used in the Stadium Drive residence hall project will be about eight-feet wide and 40-feet long, Baribeau said, some forming exposed wooden floors for the structure.
“It’s a beautiful, natural material, organic in nature that people like to be around. So exposing that is part of the attraction for us,” Baribeau said.
He said that he knew of only one project away from the UA campus planned using cross-laminated timber, an office project he’s working on. He said he expects that to change, however.
“I think in the future, it will be as common as any other available option to us,” Baribeau said.
When it comes to adoption of cross-laminated timber in North America, a team of researchers in a paper presented at a timber conference last year said it is “a time of great opportunity and challenges.”
Shiling Pei, an assistant professor of civil and environmental engineering at the Colorado School of Mines, and co-authors added that “engineers and researchers have to be vigilant about the potential risks associated with these brand new building types.”
They noted gaps in knowledge relating to how moisture affects the panels during construction. While citing many fire tests already done leading to acceptance under certain building codes, the authors said more fire research is needed.
As far as durability, “there is a lack of data on how large scale CLT buildings perform in the long run,” they stated.
The U.S. Forest Service’s Forest Products Laboratory this year published findings from the burning of a two-story test building, concluding that exposed cross-laminated timber “essentially self-extinguished” after fire consumed the building’s furnishings.
In a phone interview, Pei, who leads federally-funded research into how tall wooden buildings respond to earthquake conditions, said “the process is probably a little bit ahead of the code and research.”
But the timber “is only going to perform much better than light-frame wood,” Pei said. Sustainability benefits exist because the wood retains carbon dioxide, a greenhouse gas, he said. In contrast, researchers have described heavy carbon dioxide emissions during concrete production.
A concrete industry trade group, the National Ready Mixed Concrete Association, has launched a publicity campaign, “Build with Strength,” to counter pushes in states including Washington for more cross-laminated timber.
Glenn Corbett, an associate professor of security, fire, and emergency management at John Jay College of Criminal Justice, not affiliated with the trade group, has written about fire safety concerns in very tall buildings.
Even with smaller-scale construction, “steel and concrete typically don’t contribute to the fuel of the fire,” Corbett said, calling the issue one of “relative risk.” With cross-laminated timber, “the actual building itself becomes part of the fuel for the fire,” at least potentially, he said.
Barber, with the Arup engineering firm, said he has worked on a Portland, Oregon, 12-floor high-rise project set to be built using cross-laminated timber.
Building codes require testing to develop a fire rating, so materials are burned to see how they perform and then rated accordingly, he said.
A combination of the natural properties of wood and the sheer size of CLT components help resist fire, Barber said.
Wood exposed to fire will char, and this charred layer naturally resists fire, he explained, in addition to thickness contributing to fire resistance.
“A CLT floor will typically be about 7-inches deep,” Barber said, contrasting the size of CLT construction parts with two-by-fours used in building a single-family home. “It’s a massive piece of wood,” Barber said.
In Arkansas, the Fire Marshal’s Office of the State Police, which ultimately must sign off on the project, has been aware of the plans and has no problems with general materials, spokesman Bill Sadler said. The state uses a fire prevention code based on a 2012 version of the International Building Code.
Emails released by UA under the state’s public disclosure law show communication about the project.
“Our current involvement leaves me very comfortable with the approach you are taking,” Andy Branton with the state police wrote in a March email to architects and the campus fire marshal, Wayne Brashear. Sadler said a fire marshal’s office review of the project could be completed by this week.
Site work began near the beginning of September, with the residence expected to open by August 2019.
Flo Johnson, UA’s assistant vice chancellor for university housing, said two older dormitories, Buchanan-Droke and Gladson-Ripley, will close in 2019, so capacity will increase by about 500 beds.
UA has a housing capacity of 5,726, according to data published online for 17 residence halls and campus apartment housing. As of Oct. 16, 23 students were living in temporary assignments — typically a converted study area — because of limited space.
“I anticipate the (new) building will be full,” Johnson said, with the facility to include performing arts rehearsal space and room for galleries and academic areas.
Johnson said he expects the life of the building to be roughly 35-50 years.
With the glue-laminated beams and cross-laminated timber, “the way they’re built, the way they’re inside and protected, I think you get as much longevity out of those as a lot of concrete and steel products,” Johnson said.
MacKeith said that federally-funded research at UA into timber technology could involve studying the residence hall once its built.
“It will be a beautiful, beautiful building when it’s all done,” Clairmont said.
Information from: Arkansas Democrat-Gazette, http://www.arkansasonline.com