Taking mass timber mainstream

Taking mass timber mainstream
The Washington State Building Code Council unanimously approved new rules for the construction of buildings using cross-laminated timber (CLT). Photo: Forterra

The Washington State Building Code Council took a major step last week toward broader use of cross-laminated timber (CLT), or “mass timber, in building construction after unanimously approving rules allowing for the use of CLT for buildings up to 18 stories. The new building technology is regarded by state officials and conservationists as one of several ways to remove unhealthy trees in a financially-sustainable manner while simultaneously improving fire-resiliency for state forestland.

“We see Washington as having the potential to be a national leader on mass timber,” Forterra Director of Government Affairs Matt Ojala said. “Supporting rural communities, supporting forest health efforts – this is something we’ve identified early on in terms of helping increase the demand for these products in our state.”

A growing CLT market could help make it easier to remove small-diameter trees contributing to overly-dense forestland that can be used to make CLT but are unsuitable for traditional commercial use. Because of that, pre-commercial thinning to harvest those trees result in either a negligible profit margin or require money to conduct.

Although Oregon became the first state to approve building code requirements for CLT in August, it was through a separate process known as the “statewide alternate method.”

“With these code changes…we’re positioning ourselves to be the first state in the nation to vote on (this) through our normal code cycle.”

The revisions to the 2015 International Building Code were preceded by ESSB 5450 a measure that was approved this session and sponsored by Majority Floor Leader Marko Liias (D-21). The bill directed the council to incorporate CLT into residential and commercial building. However, work on code revisions had apparently been in the works for several years in order to incorporate emerging CLT technology. The code changes create separate design rules and regulations for buildings made of CLT that are nine, 12 and 18 stories high.

Technically, the changes will need to go through a legislative session before they go into effect. However, Ojala told Lens that “obviously given the support through the legislature and the vote they took earlier this year…it’d be hard to imagine them taking any action to change this.”

As one of the state’s largest land conservation organizations, Forterra has been one of several groups spearheading the effort to integrate CLT into the construction industry. Last year, the organization oversaw the construction of four modular classroom buildings in the Sequim School District using timber harvested from the Olympia Peninsula.

2016 study by Forterra concluded that “growing interest in CLT and anticipated, expanded allowances for CLT-based construction … suggest a market will emerge.” Construction company Katerra recently built a 29-acre CLT factory in Spokane, with plans to begin production early next year. The Vaagen Brothers recently formed Vaagen Timbers to build a CLT facility in Colville; construction on the site began earlier this year.

In October, Seattle-based architect Susan Jones spoke at an Energy Study Institute (EESI) briefing on CLT, citing numerous examples of its use in the Seattle metro area. Jones is the owner and founder of atelierjones, LLC, an architecture, planning and design firm.

Making these thinning projects profitable could aid the state Department of Natural Resources in its effort to restore millions of acres of state forestland. In addition to project costs, another challenge is the lack of mill infrastructure in key regions where much of the work is needed. DNR’s 20-year forest health plan notes: “Ensuring a reliable and consistent supply of forest products is critical in attracting private investment and supporting rural economic development. Emerging opportunities, such as the use of cross-laminated timber (CLT) sourced from small diameter trees, could support buildings designed and built in our cities with products responsibly sourced and milled in our forest communities.”

In a statement, Commission of Public Lands Hilary Franz wrote that “the building council has taken a great step toward a healthier, more resilient, more prosperous state today. Allowing the construction of mass timber buildings will provide much-needed affordable, sustainable housing in Washington’s growing cities while also boosting the health of our forests and timber industry by building demand for the small-diameter trees that pose tremendous wildfire hazards in eastern Washington forests.”

At the federal level, a Senate bill known as the Timber Innovation Act of 2017 would call on the Department of Agriculture to research the use of CLT for construction. The bill has not yet been assigned to a committee.

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