Monday, July 22, 2019

Tall timber construction code in the United States is still thinking small

Mass timber has been on the move in Europe and Canada for some time, where the intersection of energy savings and renewable resources propels the industry forward. Though the technology has found a market in places like Bergen, Norway; Vancouver, British Columbia; and Stockholm, perhaps the greatest expression of confidence in engineered timber to date is the new 18-story dormitory at the University of British Columbia—the tallest mass timber structure in the world.

And yet, mass timber projects are scarce in the United States. While there has been considerable growth in the domestic production of mass timber products like cross-laminated (CLT) and glue-laminated timber (glulam), there are but a handful of demonstration projects—none, so far, exceeding the International Building Code’s (IBC) six-story limit for Type IV heavy timber construction.

One new office building in Minneapolis by British Columbia–based StructureCraft BuildersT3 (for Timber, Technology, and Transit), reaches only seven stories and includes a concrete podium. Other projects never make it off the boards, despite early buzz and backing. Regardless of this halting progress, innovation is happening with the scale and application of engineered timber.

The University of Massachusetts Amherst’s Design Building opened in January as the country’s largest mass timber framed academic building. Its novel and expressive use of exposed timber in stairwells and in zipper trusses knotted high above the atrium, in lateral and seismic bracing, renders it a key demonstration project.

As with any building code, wide local and regional disparity exists in the recognition of and reception to mass timber. In this regulatory vacuum, states can act as boosters.

The Massachusetts legislature opened funding channels and wrote letters to inspectors in support of the UMass Design Building. “We were not exempted from any code requirements,” says Tom Chung, AIA, principal at Boston-based Leers Weinzapfel Associates, the building’s designer. “Crucially, we engaged inspectors and fire marshals early in the design process.” Chung recommends this course of action for any would-be designer looking to smooth over the approval process. Mass timber is an architect-driven movement based around an unfamiliar technology.

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