A Study of Alternative Construction Methods in the Pacific Northwest

Building a residential tower with cross laminated timber could be slightly cheaper than a comparable concrete structure, according to a recent study by three Pacific Northwest firms.

Mahlum Architects, Walsh Construction and Seattle-based structural engineering firm Coughlin Porter Lundeen teamed up for “A Study of Alternative Construction Methods in the Pacific Northwest.” The feasibility study, released in May, examines the cost competitiveness of cross laminated timber versus more traditional building materials for a 10-story residential building.

Cross laminated timber panels are manufactured with lumber that is glued in opposing directions to form a solid slab that can be used for walls, floors or ceilings.

Based on estimates from Walsh Construction staffers, the study found a potential 4 percent cost savings for cross laminated timber over concrete for a 10-story building. The cost could drop more with a mix of traditional wood frame construction and cross laminated timber.

The study focused on Seattle, but the findings can translate to other cities in the Pacific Northwest, said Joe Mayo of Mahlum Architects.

“The theory was: Would this actually be a cheaper alternative and allow the city to build more sustainable?” he said. “That was the impetus.”

Cross laminated timber has gained popularity in Europe over the past 20 years, but it’s still relatively unused in the U.S. Unfamiliarity with the product in the Pacific Northwest is one barrier to it taking off here, Mayo said. Contractors are less likely to have worked with it and most cities don’t address the product in their building codes, he said.

Researchers for the study also worked with Seattle building officials to address lingering concerns about the fire safety and structural strength of cross laminated timber, Mayo said.

“It was really a way to engage the building code officials and put that in front of them saying,

‘If we did anything like this would you be willing to approve this?’ ” he said.