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Cross-Laminated Timber (CLT) is a wood-based building material. It's manufactured by gluing planks of lumber together to make a panel. These panels are then used to construct the walls, floors, and ceilings of low-, mid-, and high-rise buildings. While the mass timber industry has been moving aggressively to secure subsidies and mandates for engineered wood products like CLT, recent studies are casting serious doubt about the safety, resiliency, sustainability, and efficiency of these products. 

As a matter of fact, preliminary results from a Washington State-funded pilot project raise serious questions about CLT’s performance. CLT materials substantially increased construction costs, were difficult to source locally, were less energy efficient than claimed, and are questionable with regard to safety; something which is of utmost importance when constructing schools and community facilities. (1)

Impulsive mandates and subsidies for mass timber and CLT will almost certainly increase project costs, pose safety risks, and unfairly alter design, engineering, and construction material selection for yet unproven environmental benefits. More information is needed.

The sustainable elements of CLT are overblown.

The majority of wood used to make CLT is harvested from U.S. forests that are not certified as being managed sustainably, (2) and the industrial timber industry is a massive carbon emitter. (3) CLT is laminated using chemical adhesives and provides uncertain carbon accounting in Life Cycle Assessments (LCA). (4)


Amid climate crisis, a proposal to save Washington state forests for carbon storage, not logging

"Nothing we currently know of works better than allowing trees to suck carbon from the atmosphere when they are living, and store it in their branches, roots and the forest soil for centuries after their death. Trees — especially mature forests — are the cheapest, fastest, most reliable form of carbon storage."


Mass Timber in the Age of Mass Extinction

"Green and other equally enthusiastic wooden skyscraper advocates ignore that if mass timber technology exists simply to offer powerful real estate interests and tech giants an easy [material] alternative ... in their well-funded projects, it will almost certainly increase carbon emissions through rapid deforestation as demand for wood products goes up ... With wood, the stakes are incredibly high, considering the potential for ecological decimation via increased harvesting and deforestation."


Cross-laminated timber is today’s hottest sustainable construction material, but can it really slow climate change?

"But CLT’s Pacific Northwest juggernaut is lacking in one crucial element: Proof that it will really help slow climate change ... Some forest scientists and climate experts are raising tough questions about the carbon-cutting dividends of cross-laminated timber construction in the Pacific Northwest, and the wisdom of boosting the region’s wood harvests."

CLT raises serious
safety concerns.

The material is at risk for delamination, rolling shear failure, and fire damage, with the International Association of Fire Chiefs (IAFC) having issued a statement rejecting proposed building code changes that would allow CLT in tall wooden buildings. (5)


'Regluing' Oregon State's Showcase for Mass Timber: The project has turned out to be a complicated cautionary tale

"On March 14, work stopped at Peavy Hall after two layers of a cross-laminated-timber floor panel came unglued and fell 14 ft from the third to the second floor. There were no injuries but the failure triggered an investigation that has lasted nearly six months."

CLT will increase construction costs and extend schedules.

The cost of lumber continues to rise and CLT manufacturers can’t even meet current demand, slowing down productivity and putting projects on hold. (6)


Warped Lumber, Failed Projects

"Another issue that has caused friction among clients are cost overruns. One problem, former employees say, was a flawed process the company used to price jobs ... Some projects have been abandoned altogether. Internal documents obtained by TRD show that of 57 projects [the company] was overseeing in the U.S. at the end of January 2019, nearly a dozen appear to be dead or have halted."


Katerra finds it's not easy to become the Tesla of prefab, mass timber construction

"Like Tesla, Katerra burst onto the scene with high hopes and the promise that technology could redefine an industry ... In its first few years, Katerra found that the Silicon Valley approach to revolutionizing a highly competitive industry through technology and rapid expansion is difficult and expensive. Welcome to the big leagues.".

More data and analysis are needed before awarding CLT preferential treatment.

Washington state's cross-laminated timber pilot project resulted in smaller, more expensive classrooms with inefficient material transport and lackluster energy efficiency. We need more information.


What Happened When a Public Institute Became a De Facto Lobbying Arm of the Timber Industry

"The research, published that March, calculated for the first time how much carbon was lost to the atmosphere as a result of cutting trees in Oregon. It concluded that logging, once thought to have no negative effect on global warming, was among the state’s biggest climate polluters ... The findings alarmed forest industry leaders in Oregon, who quickly assembled scientists and lobbyists to challenge the study and its authors. Among the groups leading the fight was the Oregon Forest Resources Institute, a quasi-governmental state agency funded with tax dollars that is, by law, restricted from influencing or attempting to influence policy."

Risks, Liabilities & Supply Chain Challenges


1. 2017 and 2018 House Capital Budget Committee Report on CLT pilot projects.

2. Monahan, Rachel. “Environmental Groups Blast New City-Funded All Timber Building for Shirking Environmental Standards.” Willamette Week. February 2, 2018.

3. Segerstrom, Carl. “Timber is Oregon’s Biggest Carbon Polluter.” High Country News. May 5, 2018.

4. Stiebert, Seton, et al. “Emission Omissions: Carbon Accounting Gaps in the Built Environment.” International Institute for Sustainable Development. April, 2019.

5. Canadian Concrete Masonry Producers Association. “Making the Cut: Is Cross-Laminated Timber Safe?” August 23, 2018.

6. Slothower, Chuck. “Supply Crunch for Mass Timber.” Daily Journal of Commerce. January 9, 2020.

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