C&B Notes

Wood Skyscrapers Are a Thing

Promising labor cost savings and condensed building schedules, timber is re-emerging in the commercial construction industry.  “Mass timber” — which is harvested from small, young trees and engineered into large pieces — is being used in new building projects that are paving the way for amended building codes and new premiumization standards in commercial construction.   

More than a century after steel and concrete became the standard for building high-rise buildings, the humble tree is making a comeback.  Sidewalk Labs LLC, a unit of Google parent Alphabet Inc., is planning to use timber to construct all of its buildings for a mixed-use community along Toronto’s eastern waterfront.  Meanwhile, Oregon became the first U.S. state to amend its building code to permit taller buildings made from timber 

As opposed to the heavy timber construction from 100 years ago, builders are using so-called mass timber from younger, smaller trees that are engineered together, said architect Michael Green, an early proponent of the material.  Unlike traditional two-by-four lumber, cross-laminated timber consists of layers of wood glued together to form solid, thick panels that can be made in custom dimensions for anything from walls and floors to beams and roofs.  Tests have shown the timber has good levels of fire resistance — close to three hours in some cases — even when unprotected, according to Ottawa-based government agency National Research Council Canada. 

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While the raw costs for cross-laminated timber are roughly equivalent to other materials, the real savings come in time, said Robert Glowinski, president and chief executive officer of the American Wood Council, an industry group that represents wood manufacturers.  The modules arrive at the job site labeled and ready to be assembled in a particular spot by crane.  Additionally, cross-laminated timber doesn’t need to cure like concrete, speeding up construction and reducing the on site-equipment needed, Glowinski said.  Mass timber design can achieve a 15 percent reduction in operational costs compared to the baseline, and results in a significant reduction in carbon emissions during operations, according to a November Seattle mass timber tower case study by design firm DLR Group. 

While it still represents a small fraction of the North American lumber market, a shift by the International Code Council, an agency that develops model codes followed by state and local municipalities, could help spur mass adoption, according to ERA Forest Products Research.  Proposed changes to the ICC building code models will allow structures made of mass timber to be built as high as 18 stories, up from the previous limit of six.  If approved, the shift will likely have a “significant impact” on materials that are used for future construction, said ICC Chief Executive Officer Dominic Sims. 

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Timber construction “is a very dramatic shift in how we think about building,” Green, the architect, said by telephone.  “Everybody’s realizing if we really step back and look at the future of construction it’s offsite construction, greater automation, faster timelines.” 

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