Building for a Sustainable Future 2020
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CLT and Other Mass Timber Projects in Washington

Written by Mass Timber Expert Ethan Martin, PE.

Washington is poised to construct several tall mass timber buildings. While Oregon tested and proved the validity of these buildings, Washington is now leading the way.

Washington developers will construct hotels, multifamily homes, and offices. Many of these buildings take advantage of the Washington State building code allowances for tall wood buildings, which went into effect July 2019. The following are code allowances for new construction types allowing mass timber:

  • Type IV-A allows 18-stories with full encapsulation of the mass timber with gypsum-type products and no mass timber exposure. There is currently one in design in Washington.
  • Type IV-B allows 12-stories with partial exposure of the mass timber, and several buildings are pursuing this construction type.
  • Type IV-C allows 8-stories with full exposure of mass timber, and many clients are pursuing Type IV-C with a variety of occupancies.

More and more architects want to build with exposed cross laminated timber (CLT) and mass timber. Construction Types IV-A and IV-B require covering or encapsulating mass timber with gypsum, such that to see a wood finish this would be an added finish on top of the gypsum, potentially leading to higher costs. Several key players in the Seattle and Bellevue market produced studies showing that tall mass timber buildings were more expensive than concrete. However, these were solely based on a cost of materials comparison and did not take into account the reduction of labor force, speed of construction, and potential reduction in carbon emissions.

The increasing number of tall mass timber buildings being designed and constructed in Washington have the potential to support forest health on public lands, support rural economies and re-energize rural manufacturing, and give owners and developers a lower carbon building material. CLT and mass timber allow architects and engineers another tool in the toolkit to create unique buildings and to produce a healthy, warm, and vibrant place for occupants to live and work with scientifically proven health benefits.

Visit WoodWorks to see the state of mass timber projects throughout the United States.

Image Below: Mass timber projects in design, being constructed, or fully built in Washington (December 2019).

CLT and Mass Timber Projects in Washington
Mass timber projects in design and construction in Washington, December 2019