Advancing Market Acceptance of CLT

A CLT panel, freshly laid up and glued, being readied for insertion into the hydraulic press in the D.R. Johnson manufacturing facility (all photos by me unless noted otherwise).

 

The construction industry, particularly here in the U.S., is often slow to adopt new and promising technologies. That said, recent decades have witnessed the growing urgency of implementing earth-friendly, sustainable strategies in buildings. Much of this impetus is attributable to an increasing awareness about how huge the carbon footprint of the built environment is (by some estimates accounting for as much as half of the world’s CO2 emissions and likewise half of its energy consumption). Regardless, owners, architects, engineers, builders, and lenders in this country continue to prioritize financial return and risk-aversion above experimentation. This is why we should applaud businesses who are willing to step up, pioneer new ways of doing things, and who champion the cause of carbon neutral efforts. 

 

 

D.R. Johnson Lumber Co. is one such company. D.R. Johnson is fully committed to the acceptance of advanced wood products in the construction industry, most notably cross-laminated timber (CLT). It is also dedicated to making the most of our state’s greatest natural resource and providing new jobs for rural communities. The key to D.R. Johnson’s strategy is promoting CLT as both a cost-effective and environmentally friendly alternative for buildings customarily constructed primarily of steel and concrete. 

 

Cross-laminated timber is conceptually very simple. Like glue-laminated beams, CLT is a “mass timber” product comprised of layers of wood planks glued together to form strong and fire-resistant structural panels for use in walls, roofs, and floors. I find it surprising CLT hasn’t previously been extensively utilized. Governments in Canada and Europe have subsidized CLT research, manufacturing, and construction of buildings for years; consequently, the majority of CLT projects to date are located abroad rather than here in the United States. If D.R. Johnson is on the right track, that’s about to change very soon. 

 

 

I joined dozens of my AIA-Southwestern Oregon colleagues as well as students and faculty from the University of Oregon’s Department of Architecture last Wednesday for a visit to D.R. Johnson’s plant in Riddle, OR. The facility is only one of two in the country (the other belonging to SmartLam in Whitefish, MT) producing CLT panels for use in structural applications. We not only enjoyed the opportunity to witness D.R. Johnson’s manufacturing processes but also learn a great deal about mass timber construction in general via a series of presentations both en route and at our destination. 

 

Judith Sheine, head of the UO Department of Architecture, and Mark Donofrio, AIA, assistant professor of architecture (and also current member of the AIA-SWO board of directors), described the work of their joint studio in which students explored the properties and potential of CLT construction in the design of a parking structure for the Glenwood district between Eugene and Springfield. Notably, the studio was part of a collaborative effort involving both the University of Oregon and Oregon State University’s College of Forestry. Judith and Mark explained how, with support from the State of Oregon, the collaboration is leveraging academic resources to create and test new applications for CLT in the construction of modular and tall buildings. A byproduct of UO/OSU alliance is the newly formed National Center for Advanced Wood Products Manufacturing, which will help accelerate use of CLT in this country. The Center’s goals are to assist Oregon’s timber industry by growing the market for mass timber products, expand the design profession’s stellar reputation for sustainable design, and establishing Oregon as North America’s hub for expertise in innovative wood building design.

 

Glenwood Mass Timber Parking Structure: UO studio project by Tom Adamson, Ryan Kiesler, and Tom Moss (Judith Sheine & Mark Donofrio, professors)



Valerie Johnson, president of D.R. Johnson, presented the sustainability case for CLT, which is premised upon its smaller environmental impact when compared to other common building materials. She pointed to how life cycle assessment studies show that wood products outperform steel and concrete in terms of embodied energy, as well as air and water pollution produced. Wood also has better thermal performance properties than common alternatives, making it more energy efficient. And wood is the only common building material derived from a renewable resource. 

 

Valerie Johnson

 

Valerie argued wood products have a significantly smaller carbon footprint, because they sequester carbon from the environment. As trees grow, they absorb carbon dioxide from the atmosphere, storing the carbon in wood fiber and releasing oxygen. The stored carbon remains in the wood after the trees are converted to wood products, and the cycle starts over when new trees are planted to replace those that were harvested. 

 

She described how D.R. Johnson is working with the National Center for Advanced Wood Products Manufacturing and the American Plywood Association (APA) to manufacture and test CLT panels to obtain third-party certification and assist with the development of consensus-based product and design standards. 

 

Valerie clearly relishes the opportunity the advent of CLT presents her company. For her, it’s a once-in-a-career opportunity to be on the cutting edge of something new and beneficial for our planet. 

 



Completed CLT panel. CLT is generally manufactured in slabs that are 3, 5 or 7 layers thick, and that are 10 feet wide and up to 60 feet long.

 

Tom Williamson, PE, of Timber Engineering LLC, further enumerated the advantages of CLT. These include its lower material weight at comparable strength—up to six times lighter than concrete. The lighter weight is advantageous in the case of earthquakes and also for transportation and onsite assembly. CLT panels act as plates with dimensional stability and static strength in all directions. CLT projects can be erected very quickly, reducing onsite construction time. They produce minimal jobsite waste, require smaller footings, and are versatile and easily integrated with other building materials. CLT also allows the use of shorter pieces of wood that can’t be used in traditional glulam beams, as well as lumber from smaller trees harvested from managed and sustainable forests. 

 

Tom touched upon the development of various CLT design standards and the integration of provisions within the model building codes specific to the use of CLT. These include code pathways and considerations for the use of CLT in tall buildings (greater than six stories in height). He cited the recently published CLT Design Handbook, which includes useful information for architects and engineers on topics ranging from detailing connections between panels to fire performance of CLT assemblies. 

 

 The U.S.CLT Design Handbook is available for free download at www.masstimber.com.

 

Tom didn’t shy away from identifying the drawbacks of using CLT, which are primarily associated with our current unfamiliarity with the product and its associated design standards and codes, its lack of performance history in North America, the fact its use under wet conditions has not yet been extensively studied, and its cost relative to competing systems. 

 

The cost issue figured heavily during a presentation by John Rowell, AIA about his firm’s decision to use CLT in the design of the 33 East Broadway project in downtown Eugene. John along with his partner Greg Brokaw, and businessman Kaz Oveissi, are the developers of the proposed office building. Rowell Brokaw Architects will occupy one whole floor of the four-story design, furthering the company’s commitment to working downtown. John sees 33 East Broadway as appealing to like-minded companies, who will be attracted to its urban setting, innovative use of exposed CLT, and the natural, creative vibe of the design. 

 

John said RBA used cost models to compare the benefits and shortcomings of various structural material and system options. In the end, the draw of using CLT—its innovativeness, aesthetic potential, and sustainability as a building material—outweighed RBA’s unfamiliarity with the technology and concerns about its expense. The arrival of D.R. Johnson on the CLT scene during RBA’s design of the project proved serendipitous. With D.R. Johnson as a local manufacturer for the panels, the cost for sourcing them would be reduced significantly. Opportune too was the State of Oregon’s eagerness to support CLT projects and the ongoing research by the Center for Advanced Wood Products Manufacturing. 

 

John elaborated upon several aspects of CLT building design that are unique to the technology. These include how to detail and protect the connections from exposure to fire, and also how to accommodate distribution of MEP systems and address acoustical concerns. John hopes to see the project break ground very soon. 

 

 33 East Broadway (rendering by Rowell Brokaw Architects)

 

Mariapaolo Riggio is an assistant professor in the Wood Science and Engineering (WSE) department in Oregon State University’s College of Forestry. She is a key member of the Center for Advanced Wood Products Manufacturing, conducting research on mass timber technologies, including CLT. Mariapaolo brings an interdisciplinary perspective to her research, with a particular emphasis upon the long-term performance of mass timber buildings using integrated monitoring methodologies. She described how her investigations and those of her associates will contribute significantly toward the increasing acceptance of CLT as a building material here in the U.S. The proliferation of CLT will benefit not only companies like D.R. Johnson but also create jobs in Oregon and move the construction industry toward a more carbon-neutral future.  

D.R. Johnson’s newly installed Hundegger PBA “gantry” style saw. The saw efficiently cuts the CLT panels, using up to 9 different cutting and milling tools for roof profiles, wall details, and openings.

Something that surprised me during our tour of the D.R. Johnson facility was how low-tech the production of CLT panels actually is. As described above, it really does just consist of gluing up lumber in (perpendicular) layers, pressing them together, and then cutting them to the desired size and shape. At the moment, much of the assembly process still requires manual labor (a notable exception being the Hundegger PBA computer numerical controlled (CNC) saw). If CLT really takes off, I can imagine D.R. Johnson further investing heavily in robotic technology to increase efficiencies. It wouldn’t surprise me if heavily capitalized lumber industry giants (such as Weyerhaeuser or Georgia Pacific, or perhaps one of the established European or Canadian manufacturers) jump in once the commercial viability of CLT in the U.S. market is established. As America’s CLT pioneer, I hope D.R. Johnson is rewarded for its efforts and corners its fair share. 

 

The Vine & Wine Center at Abacela Winery 

A definite treat along our journey back to Eugene was a stop at the Abacela Winery, just outside of Roseburg. Sited astride the Klamath/Coastal Range fault, the winery’s sloping, scenic site boasts soil and climate conditions most conducive to the production of the Tempranillo, Syrah, Grenache, Malbec, Tannat, and Albrino grape varietals. In keeping with the sustainability theme of the road trip, Abacela uses a geothermal system for heating and cooling its Vine & Wine Center, practices sustainable viticulture, and has set aside 300 acres of its property as an oak savannah nature preserve. 

Following our visit to Riddle, I’m much better informed about cross-laminated timber, how it is manufactured, its benefits, and the potential for its applications. D.R. Johnson’s CLT venture is highly promising. In my opinion, the increased use of mass timber products like CLT is good for Oregon and good for our natural world.  I know I speak for everyone who participated in the tour when I say kudos to each of our speakers, the tour organizers, and our hosts at D.R. Johnson for a well-conceived, enjoyable, and highly informative road trip.