Wood innovations: Mass timber
Most wood used in buildings is harvested from live, mature trees—but much of what we need to remove from forests to reduce fire risk is small diameter trees and dead woody debris. That’s why Forest Service scientists are innovating ways to use and profit from less merchantable forest products. One of these innovations, mass timber, is an amalgam of small diameter trees bonded together that rivals steel and concrete in strength and durability. Structures made of mass timber can be prefabricated and go wherever there’s a housing crunch: near forests, in rural communities, in growing cities.
Why is mass timber useful?
Buildings made of mass timber go up more quickly than those made of concrete and steel. They’re also easily moved―meaning they’re an option for emergency and temporary housing.
When used alongside other building materials, mass timber is durable in the face of fire, high winds, and earthquakes.
Mass timber is lighter than concrete and steel, reducing transportation costs.
When sustainably sourced, mass timber emits much less carbon throughout its life cycle than concrete and steel do.
How is the Forest Service pioneering mass timber use?
Through a shared patent, the Forest Service and PathHouse LLC pioneered a mass timber modular floor cassette. This watertight base houses all utilities as well as a fire suppression system―itself a co-owned, patented product. This cassette streamlines design, permitting, and construction timelines, and units are available on-demand.
The Willamette National Forest in Oregon is replacing employee houses lost to fire with mass timber units. Other communities and Tribes are considering modular homes for similarly urgent needs. Forest Service grants are sparking these projects across the nation, including in Seattle.
Agency researchers designed a ready-to-assemble tornado shelter from mass timber that can resist winds up to 250 mph. Agency scientists have even created a panel made entirely of laminated wood that can stop bullets.
With WoodWorks, agency scientists are finding ways that mass timber buildings can soar as high as their concrete and steel counterparts. They’re filling knowledge gaps around mass timber structure and design that may enable its widespread use.
Agency scientists are testing how different treatments might protect mass timber from termites and fungi. In a study lasting two years, mass timber samples treated with borates and left to their own devices in a Mississippi experimental forest showed much less decay and termite damage than similar samples left untreated or treated with insecticide only.
Currently, most mass timber is made from softwood—but new research from agency scientists may encourage mass timber made from hardwood, bolstering a lagging market. They found mass timber from hardwood to be effective, attractive, and potentially plentiful given the right economic conditions. They recommend further research on the barriers to using hardwood in mass timber, including cost and durability.
Agency scientists assemble mass timber leaders during the North American Mass Timber Research Needs Workshop, most recently held in 2022, to discuss innovation and research needs in the industry.
Mass timber buildings are made of wood—and wood burns. Forest Service researchers have teamed up with university, industry, and government partners to study how mass timber buildings, plus the furniture and appliances in them, hold up to fires. Other research indicates that mass timber can resist fire long enough to meet international building codes.
A mass timber building system developed in part by agency scientists and partners is resistant enough to earthquakes and high winds to comply with US building codes. In fact, the system holds up so well that it’s informing international building codes.
