Timber Towers Reach for the Skies

Opening this summer on the University of British Columbia campus, Brock Commons is an 18-story cross-laminated timber building.

Are 20-story timber high-rises the future of building? Perhaps, if code changes under development by a committee of the International Code Council (ICC) are eventually approved for the 2021 International Building Code (IBC).

The ICC’s Ad-Hoc Committee on Tall Wood Buildings recently held its third in-person meeting to consider adding new provisions for mass timber buildings exceeding the traditional height and area limits for “heavy timber” construction.

ICC established the committee at the request of the American Wood Council (AWC) and other stakeholders following considerable debate over several proposals during the hearings for the 2018 International Codes. The committee includes structural engineers, architects, building and fire officials, and representatives from the wood, concrete and steel industries.

During two and a half days of meetings, committee members and industry stakeholders engaged in serious and substantive conversations about fire safety, structural performance and architectural design. Smaller work groups have had regular conference calls to develop draft code language for discussion by the full committee.

Mass timber construction uses solid, built-up, panelized or engineered wood elements with cross-sections exceeding the typical studs, joists and posts used in light-frame construction: for example, 6-inch by 8-inch columns, 6-inch wide by 10-inch deep beams, or 5-inch thick floor panels.

Mass timber includes such products as glued-laminated beams and columns, cross-laminated timber (CLT) wall and floor panels, and nail-laminated timber (NLT) panels, as well as traditional solid-sawn heavy timber elements.

CLT panels consist of side-by-side sawn lumber boards stacked in alternating layers, bonded together with structural adhesives and pressed into panels typically 3 to 7 layers thick. CLT has been an approved option for one- and two-family dwellings under the International Residential Code (IRC) and multifamily buildings up to five stories and 85 feet in height under the IBC since the 2015 editions of those codes.

The ANSI/APA PRG-320 Standard for Performance-Rated Cross-Laminated Timber, a consensus standard developed by APA-The Engineered Wood Association, provides manufacturing, testing and quality assurance requirements and is referenced in the IRC and IBC.

Meanwhile, innovative builders, architects and engineers are forging ahead with taller CLT projects in the United States and Canada.

T3, a nine-story office building, recently opened in Minneapolis, and Brock Commons, an 18-story student housing project at the University of British Columbia, is nearing completion. Framework, a 12-story mixed-use building in Portland, Ore, is under design and just received its building permit from the state.

For information about the committee’s activities or mass timber construction, contact Gary Ehrlich at 800-368-5242 x8545.

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