Multi-Story Buildings Going Up in Oregon Using CLT
The use of cross-laminated timber (CLT) in multi-story buildings is no longer just something people are talking about. In Oregon, two new buildings that feature CLT are almost complete, and construction on a much taller 12-story building is set to begin next year.
CLT has been making a lot of headlines lately, as some architects and contractors want to use it to build tall buildings because of its sustainability benefits, especially its ability to store carbon dioxide. CLT is made from long pieces of lumber glued together and then layered perpendicularly to form thick panels which can be as large as 10’ wide and 50’ long.
Technology developed by USNR has helped D.R Johnson become the first company officially licensed to produce CLT panels in the United States.
So what’s so great about CLT? CLT is six times lighter than concrete, cost competitive with steel and concrete, and fire rated to meet current building codes requiring material to pass a 2-3 hour fire rating. Also, it is thinner than concrete, which saves space.
By being lighter, CLT allows for construction on plots of land that otherwise would not be feasible with steel or concrete. For example, softer soils near bodies of water might allow for taller construction or on existing aquatic structures, such as The Library at the Dock in Melbourne, Australia. Lower weight also reduces foundation costs.
Daniel Hindman, an associate professor in the Department of Sustainable Biomaterials at Virginia Tech, is leading the university’s research efforts on CLT. Hindman suggested, “Architectural engineers are really getting excited about CLT due to the sustainability aspects, quick construction and low building weight.”
A common concern when people first hear about CLT is fire. However, the material is fire rated to meet current building codes requiring material to pass a 2-3 hour fire rating. Robert Smith of Virginia Tech explained, “In a catastrophic fire, steel loses its tensile strength and collapses, and concrete cracks up, but wood beams this large will smolder and put themselves out.”
Even if panels do burn, charring on the outside protects the interior wood, leaving the panel structurally sound. Finishing the panels with wallboard or another material further improves fire protection.
A major benefit of CLT is the way it can be quickly put into place allowing for modular construction, similar to building with Legos.
Also, CLT allows for the warmth and beauty as well as the natural feel of wood to be used more in construction. Michael Green, an architect and pioneer of CLT, said in a TED talk, “Every time that people go into my buildings made from wood, I have noticed that they act completely differently. I have never seen anyone go in and hug a concrete or steal column. But I have seen that happen in a wood building.”
Green pointed out that no two pieces of wood can ever be the same anywhere on earth. He explained that wood puts Mother Nature’s finger prints in our buildings in a way that no other building material can. You should watch Green’s TED talk, it is both inspiring and enlightening. You can view it at http://tinyurl.com/jfuutmm
Besides the aesthetic beauty of wood, it solves some serious environmental issues. Green pointed out that steel and concrete have very high energy requirements and lead to very high greenhouse gas emissions.
Green added, “In USA about 47% of CO2 emission come from buildings compared to 33% for transport and 19% from industry.”
And the world housing growth is clashing with the climate change challenge, and Green believes wood may be the answer. He explained that wood is grown by the power of the sun and it stores carbon. One cubic meter of wood will store one ton of CO2.
Green said, “The only way to limit CO2 in the atmosphere is to reduce emissions and find storage. Wood is the only major building material that does both of those things.”
Also, wood construction can help spur job growth in rural communities, which is a major benefit. By finding markets for wood, you also encourage more land to be used for growing trees.
There are still a few major roadblocks to widespread CTL adoption. Building codes need to be modified to allow for CLT construction. Much of the research required to commercialize CLT has been done or is in the works. Now, the forest products industry just needs to invest in building capacity and production. Also, customers have to start asking for CLT and preferring it to the conventional methods. Significant media buzz is helping in this regard. But it still may be years off before CLT results in a building revolution in the United States. However, the technology shows promise, and it could be a huge market opportunity in the future.
Richard Woodcock Education Center
When the Richard Woodcock Education Center officially recently opened at Western Oregon University (WOU), it became the first multi-story building in the state constructed with CLT. CLT panels were used in limited areas of the two-story structure including the stairwell and around the fireplace.
The $18.6 million building features “creative usage of wood through wood moment frames and timber hybrid structures, and will also promote the use of cross-laminated lumber,” according to Lisa Catto, a WOU media relations spokesperson. It will not only serve as the new College of Education building for the university, but has also been designated as a demonstration project to promote the innovative use of Oregon wood products by former Governor John A. Kitzhaber.
The CLT panels used at the new center were manufactured by D.R. Johnson Wood Innovations, a division of D.R. Johnson Lumber Co. in Riddle, Oregon. In business since 1951, the second-generation, family-owned business is the first U.S. manufacturer of structurally certified CLT (APA/ANSI PRG 302 Certification Standards), according to the company’s sales manager Todd Black.
“Currently we are certified through the American Plywood Association as a V1 Grade CLT Manufacturer, which means we utilize Douglas fir in all our CLT panel production. The typical Douglas fir we use is 25-35 years old,” he said. “Although these panels are very rigid and structurally stable, they are much lighter than their steel and concrete building material counterparts.”
Approximately 3,032 sq. ft. total of CLT was used on the WOU center, according to Derek Weaver, a project manager with general contractor Andersen Construction. “It’s all five layers of Douglas fir 2×6 for a total thickness of 7″,” he added.
The single largest panel used on the project was 10’x24’, said Black, although in some instances panels were glued together to form even larger panels.
The CLT Production Process
D.R. Johnson worked with USNR to develop a press designed to manufacture CLT panels. USNR had experience making presses for OSB, MDF and plywood, but this CLT process is a different animal altogether.
USNR’s CLT press uses pneumatic pressure to produce 10’ wide CLT panels up to 24’ long and 10.5″ thick. The panels are assembled using from three to seven layers of cross-laid timbers. Adhesive is applied between the layers prior to the panel entering the press.
This press follows a “window frame” design consisting of 16 identical steel frames spaced 18″ apart, with each frame having an opening (or “window”) which allows CLT panels to pass through the press. Once the panel has been fed into the press via a set of pop-up rolls, it comes to rest on platens within the press opening.
A set of pneumatic cylinders then applies pressure from the sides to ensure a minimal gap between timbers within a given layer. Meanwhile, a set of channels carrying 8 large diameter pneumatic hoses is lowered to rest on top of the CLT panel. Once the panel is configured correctly within the window of the press, the 8 hoses are brought to pressure (typically to 100 psi, though it’s capable of delivering up to 150 psi of pressure). Press time depends largely on the time it takes to lay-up the panel, with a ratio of approximately 2.5:1 (press time to lay-up time).
The unique curvature of USNR’s press opening allows it to redistribute stress and withstand the tremendous pressures required to produce APA-certified CLT panels. While most CLT presses utilize hydraulic cylinders to achieve the necessary pressures, and USNR offers that option, the standard USNR press applies pressure pneumatically instead, thanks to a heavy-duty hose which takes advantage of recent material advancements in the oil and gas industry.
This method is robust, extremely cost-effective, and more environmentally friendly than the hydraulic alternative commonly used in Europe. An additional advantage to the USNR design is its modularity – although the press is currently configured to produce 24’ panels, it could easily be modified to any desired length by simply adding or removing window frame segments.
“The real genius of USNR’s design is putting the window frames in 18-inch increments,” said Valerie Johnson, co-owner of D.R. Johnson. USNR’s modular press design enables it to be expanded infinitely along its length, giving D.R. Johnson the flexibility to grow its press.
“If USNR had not come up with that, I don’t know if we would have ever pulled the trigger because we didn’t know exactly what we needed at the time,” Valerie Johnson remembered. “We started out wanting to make an 8 x 16’ panel, then it went up to 10 x 16’, and over time we finally settled on 10 x 24’. The fact that USNR designed it with frames that could be added in a modular way is sheer genius. It was the answer for us.”
Laura Meeker, USNR Mechanical Engineer on the project explained, “The modularity evolved from the fact that the project began with a smaller press, and when we realized they needed a bigger press, it seemed like a natural solution.”
In addition to the press, D.R. Johnson uses a Hundegger PBA CNC machine in its CLT production process. That machine provides the ability to customize each CLT panel with precise routing and cutting based on the project’s computer-aided design (CAD) files, which can include electrical and plumbing.
The customization of panels to precise specifications will further reduce construction timelines and costs. D.R. Johnson expects the market to require this level of prefabrication because there isn’t an economical way to move these panels around on the jobsite to do this work. A 10 x 24’ panel of 5-ply weighs almost 5,000 lbs.
Also, a pure melamine formaldehyde resin with no urea or urea-formaldehyde additives is added to form the panels. There is no question that the innovation by USNR was critical to this process. “There were a number of things that fell into place for us to make this a reality,” Johnson explained, “but without USNR we’d be nowhere yet.”
Albina Yard Project
CLT produced by D.R. Johnson is also being used in the Albina Yard Project, a four-story, 16,000-square-foot mixed-use office building in Portland. It is two stories taller than the Woodcock Center and is said to be the first commercial building in the country with a structural system made from domestically produced CLT. The project is on schedule and slated to be completed by the end of this summer, commented Black.
“The CLT panels used in the Albina Yard Project ranged in size from 9’x20’ to10’x22’,” he said. “The CLT arrived on the jobsite completely fabricated and ready to set directly from the truck onto its location within the project. By the third floor, the 4,000+ sq. ft. of floor panels were craned off of the truck and placed on the project in two hours.”
“There were three floors and one roof structure that were approximately 4,000 sq. ft. a piece. Eighty to 85 CLT panels were set on the D.R. Johnson Glulam beam/column structural frame to complete the project. The bottom (ceiling) side of the CLT panels and all Glulam beams/columns will remain exposed while the top side of the CLT panels will have a gypcrete topping slab and traditional flooring material applied,” he explained.
More About D.R. Johnson
The division behind the CLT started in 1967 with glulam production. CLT is now being sold under the name D.R. Johnson Wood Innovations. The glulam business started 16 years after the related sawmill began. D.R. Johnson later acquired Prairie City Lumber, Grant Western Lumber and Umpqua Lumber, and expanded into biomass power production with the construction of two co-generation plants in Prairie City and Riddle in the mid-1980s.
Prior to the economic collapse of 2008, the combined sawn lumber production was 1,000,000BF per day and Glulam production was 50,000BF per day.
After D.R. Johnson, who started the company, passed away in 2010, his daughters Valerie Johnson and Jodie Westbrooks took over the company. After huge investments in machinery, technology and expansion of their Riddle facility, the company started producing CLT in 2015.
In addition to its CLT projects, the company has provided Glulam beams and columns for a number of high-profile projects including the Google headquarters in Mountain View; Pixar Studios in Emeryville; Jay Leno Vintage and Classic Car Collection Building in Beverly Hills; and the Bob Hope Foundation Center, in North Hollywood, all in California; the University of Washington Intellectual Building in Seattle; and the Portland Trailblazers Practice Facility in Tualatin, Oregon, in addition to others.
For more information on CLT, visit http://oregonclt.com/