Architect Susan Jones designed the 1,480 square foot home in Seattle's Madison Park out of cross-laminated timber.
Photo by Atelier Jones

Mass Timber: The Innovative Future of our Built Environment

New building codes in Washington State to allow mid and high-rise mass timber buildings up to 18 stories.

On Friday, November 30, the Washington State Building Code Council (SBCC) voted to approve code changes that will allow for the structural use of mass timber in buildings as tall as 18 stories. This makes Washington the first state in the nation to allow tall mass timber buildings into its building code, without pursuing an alternate method.

The alteration of these building codes will support of a new generation of engineered wooden building materials with exciting properties of strength, durability and beauty. With mass timber, architects and builders acquire a new material to create with and rural areas gain the prospect of new high-skilled, high-paid jobs.

For the past four years, Forterra has led a statewide coalition to catalyze a market for Cross Laminated Timber, and early on the Coalition identified updates to the building code as key to accelerating this market in Washington State. These code changes are a huge step forward, and represent the accomplishment of a key goal of the Coalition.

As mass timber becomes more widely utilized, it has great potential to support employment in rural areas, improve forest health on public lands in need of restoration, and enable new and affordable approaches to building for fast-growing urban populations. 
Michelle Connor

What is mass timber?

Mass timber is a category of large-scale, prefabricated engineered wood products, the best-known of which is Cross Laminated Timber (CLT). CLT panels are comprised of multiple layers of lumber, each stacked perpendicularly and bonded with a structural adhesive. The result is a beautiful, lightweight, and durable building material, with favorable fire, seismic and thermal performance. European architecture has been utilizing CLT for over twenty years.

What do the changes mean?

“These code changes will allow for greater use of mass timber here in Washington, and position our state as a leader in the nation,” said Michelle Connor, President and CEO of Forterra. “As mass timber becomes more widely utilized, it has great potential to support employment in rural areas, improve forest health on public lands in need of restoration, and enable new and affordable approaches to building for fast-growing urban populations.

Has mass timber been used in Washington before?

The previously set building code limited mass timber’s structural use to a maximum of 6 stories. Several mass-timber projects below 6 stories have been completed in Washington in recent years, including a set of pilot CLT classrooms funded by the State of Washington. Now, with approval of these code changes, taller wood projects like Brock Commons at the University of British Columbia can move forward. CLT is great for rapid modular construction, and it took less than 70 days for the 18-story wood hybrid Brock Commons building to be completed after the prefabricated components arrived on site—four months faster than an average project of this size.

What are the code changes?

Washington’s code changes will update the 2015 International Building Code to incorporate all of the International Code Council’s Tall Wood Building Code proposals voted on in Richmond, VA in October, 2018. It will permit three new types of mass timber building construction — Type IV A, B, C — allowing for the structural use of mass timber at 18, 12, and 9 stories. The action comes after more than two years of comprehensive research and testing, including full-scale fire tests, completed by the International Code Council Ad Hoc Committee on Tall Wood Buildings.

 

When do the changes happen?

Washington’s code changes, which were officially applied for by the American Institute of Architects Washington Council, are scheduled to go into effect at the conclusion of the next Washington State Legislative Session, which is scheduled for April 28, 2019. This puts Washington years ahead of the national effort to amend the 2021 International Building Code.

The bottom line is that these code changes will allow Washington to embrace more innovative construction practices and lead the nation in long-term sustainable building. Susan Jones, of the architectural firm atelierjones said, “I am so proud of my state of Washington.  As a third-generation Washingtonian, who grew up amongst its forests, I am deeply optimistic about the impact these code changes will have on our forests’ health and long-term sustainability.”

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