Wood's New Wave

Advances in computer software and computer technology make wood more viable as a structural component.
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Nancy B. Solomon, AIA

Mass timber relies on very large, solid prefabricated panels made of wood that can be used for floor, wall, or roof structures in multistory buildings. Advocates of this solid-wood-panel approach liken it more to tilt-up concrete methods than to older wood approaches in terms of its prefabrication and assembly techniques. “Building a wall conventionally with 2x4s requires a lot of work on-site,” explains Michael Green, principal of Michael Green Architects in Vancouver and a leader in wood-panel construction. “With mass timber, however, the wall is already made before you tilt it up.” As with a tilt-up concrete system, mass-timber buildings can be erected very quickly—the prefabricated panels are hoisted into place and bolted together with various connections.

Fast + Epp worked on this addition to Thompson Rivers University in Kamloops, British Columbia. A lightweight, undulating wood roof and mezzanine were added to the existing building.

Photo © Florian Maurer

Technologically speaking, Lisa Podesto—senior technical director of building systems at Woodworks, an educational initiative of the Wood Products Council—credits the development of mass-timber construction to relatively recent manufacturing advances in Europe, including increases in the scale of presses used to fabricate engineered wood and improvements in CNC machinery that allow for the very precise production of components.

Mass-timber advocates are quick to point out that the methodology is still in its infancy, and that there are many ways to fabricate the panel products and to assemble them on-site. “I try to remind people that it's like creating structural-steel systems,” says Green. “You can put steel up in many ways, and each time you do so, you must engineer it.”

Wood-Panel Products

The mass-timber product that has gotten the most attention to date is the glued version of cross-laminated timber (CLT). Developed in Europe about 20 years ago, these panels are typically fabricated by gluing the faces of 2x6 spruce planks oriented in one direction to the faces of adjoining 2x6 spruce planks oriented in the perpendicular direction, repeatedly, to form multiple layers that are then pressed together. A single panel can measure up to 40 feet long and 10 feet wide. Openings for architectural or mechanical features can then be cut out of the panel before it is transported to the site and hoisted into position. CLT is rigid in two directions, so it can span horizontally between beams or vertically between columns without any additional support. According to Larry McFarland of McFarland Marceau Architects in Vancouver, who specified CLT for the floor deck of the Environmental Learning Centre in North Vancouver, the panels provide the equivalent strength of concrete for one-sixth of the weight.

 

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Originally published in GreenSource.
Originally published in March 2013

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