City of Seattle approves construction of taller wood buildings

The Seattle City Council this week approved changes to the Seattle Building Code that may bring the city one step closer to allowing tall buildings made entirely of mass timber products, like cross-laminated timber (CLT).

The new law will allow apartment and condo buildings, which are usually built with five floors of wood-frame construction on top of a one-floor base of concrete, to be constructed with more wood floors, according to The Urbanist.

The revised (Seattle Building Code) will allow up to 75 feet wood-frame construction, which is measured above any concrete podium below. This will allow “six-over-two” construction in zones with 85-foot height limits since the first two floors would be concrete with the next six floors as wood frame, in essence providing a new option for eight-story construction. Similarly, the revised construction methods will allow “six-over-one” developments in zones with 75-foot height limits (six wood-frame floors over one floor of concrete).

The Urbanist notes the new law is a positive sign that the city of Seattle supports the use of wood in the construction of tall buildings. The city of Seattle’s law is also a step toward providing builders the “menu of choices” that State Sen. Marko Liias, D-Everett, talked about regarding his successful bill directing the Washington State Building Code Council to adopt rules allowing for the use of mass timber in construction.

“I don’t want just a demonstration project (in CLT,” Liias said.) “I want a way that this is integrated into the code, and we can do it more frequently that just demonstration projects,” he said. “In Scandinavia they’ve been doing this a long, long time and they’ve got it fully integrated into their building code so that as a project designer is designing a building, they’ve got a menu of choices. … So how do we integrate it into the building code so that it is readily accepted, and we know how to use, and building designers can use it alongside all the other options?”

The Washington Legislature approved Sen. Liias’ bill earlier this year, on a 45-2 vote in the Senate and 91-6 in the House. The state building code legislation will lead to an increase in the use of mass timber products in commercial and residential construction.

The prime sponsor of SB 5450 was Sen. Marko Liias, D-Lynnwood, with other key contributions from Sens. Dean Takko, D-Longview, and Guy Palumbo, D-Maltby.

“Mass timber is already being used in countries around the world to construct sustainable, ecologically sound buildings,” said Liias. “Putting people first means taking every step possible to build a greener, more inclusive economy for every Washingtonian.”

“Creating a pathway for greater use of mass timber in Washington embraces our greatest natural resource while bolstering a crucial industry for rural economies,” said Takko. “Timber has long provided family wage jobs in communities across the Evergreen State and I’m proud that the Legislature took action this year to keep that tradition strong.”

More certainty in the permitting process will mean more building projects using mass timber, which in turn will lead to more mass timber production facilities, more demand for timber from sustainably managed forests and more jobs in the rural communities where the forests and production facilities are located.