EWP & Mass Timber By Bill Parsons, WoodWorks
THE EIGHT-STORY Carbon12 in Portland, Or., includes a glulam post-and-beam frame and CLT floors and ceilings. (Photo by Andrew Pogue)
Establishing mass timber as a viable structural solution ass timber is a fascinating study in U.S. market development. First came awareness that other countries were successfully using innovative wood products in high-rises and other atypical building applications. Because of the unique structural and fire-resistance characteristics of large, solid wood members, these products could be left exposed, creating tremendous design potential—along with the possibility of premium lease rates and coveted tenants—which didn’t go unnoticed by North American building designers. Early supporters of mass timber welcomed a sustainable, carbon-friendly addition to the mix of structural solutions for a broader range of building types. Governments in particular appreciated that mass timber can be made from smaller diameter trees and trees impacted by insects and disease, because this could help incentivize forest thinning and reduce the risk of wildfires. Mass timber manufacturing also requires skilled workers, so a robust sector would translate to well-paying jobs and stronger rural economies. Looking at the trajectory, it seems fair to say the growing use of cross-laminated timber in Europe, especially in buildings taller than eight stories, was largely responsible for establishing “mass timber” in the North American lexicon—even though products such as glued-laminated timber and nail-laminated timber had been around for decades. In a relatively short timeframe, there came an abundance of research and testing (it helped that Europe had a long history of performance to learn and draw from), code committees, education, and technical resources. Organizations like the USDA Forest Service and Softwood Lumber
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Board invested in initiatives such as the U.S. Tall Wood Building Prize Competition. Architect Michael Green gave a TED Talk on wood high-rises as a carbon mitigation tool. Projects were built, companies invested in manufacturing, and North American mass timber products are now readily available across the U.S.
Fast Forward to More Than 500 Projects
The program I work with, WoodWorks, provides education and free technical support related to the design, engineering and construction of commercial and multi-family wood buildings, including mass timber, so we’ve seen the trend up close. In 2011, the first commercial CLT building was constructed in the U.S. The product came from Europe, which made sense; at the time, Europe had more than 20 years of CLT history and North America’s was just beginning. In 2015, WoodWorks technical staff supported a handful of buildings where the developer, architect or engineer had an interest in using mass or heavy timber—but we could see momentum building. In 2017, we assisted on 158 of these projects. Last year it was 219. We also track projects not supported by our technical team. As of March 31, 2019, 545 mass timber buildings were complete or in design in the commercial, multi-family and institutional categories across the U.S.
Safety & Performance
Mass timber would not have made inroads as quickly as it has without demonstrable performance. Among the examples, fire testing has been performed at a compoBuilding-Products.com