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Cross-Laminated Timber

Evaluating whether the Seattle Building Code should allow more height for buildings designed with cross-laminated timber.

What is Happening Now?

Our Seattle Building Code currently limits buildings made of wood products to no more than 85 feet in height and no more than 6 stories (depending on use of the building). With the aid of the Construction Codes Advisory Board’s (CCAB) Innovation Advisory Committee, we are deciding whether to allow bigger buildings built of cross-laminated timber (CLT).

CLT is an engineered product made of sheets of boards placed in layers perpendicular to one another in a manner similar to plywood. However, unlike plywood, CLT is made of thick layers of lumber with enhanced structural and fire-resistive performance.

Large CLT buildings have been built in other parts of the world. The Graphite Apartments in London is a nine-story CLT building, and a 10-story residential building, Forté is nearing completion in Melbourne, Australia.

Proposed Benefits

  • Carbon negative construction
  • Sustains local materials and industries
  • Reduces construction time
  • Cost competitive with concrete and steel
  • Clean and quiet construction process
  • Ideal for tight urban sites

The End Result

Seattle is participating in an International Construction Code’s (ICC) ad hoc committee to explore the building science of tall wood buildings. The scope is to investigate the feasibility of and take action on developing code changes for tall wood buildings in the national codes. To receive more information and to research the meeting minutes, please go to the ICC web site.

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 Ask Us

Kathleen Petrie
Sustainable Codes Analyst
(206) 615-0541

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