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September 29, 2023
Mass timber is an umbrella term for a class of engineered wood building materials, including those created by layering and bonding wood. The best-known example of mass timber is cross-laminated timber, which can be made from small-diameter or diseased trees to create a strong, lightweight building material. Other types of mass timber include nail-laminated timber, glue-laminated timber, laminated strand lumber, and laminated veneer lumber.
Unlike lumber, which is typically used in traditional stick-frame construction of houses and low-rise buildings, mass timber is strong enough to construct much larger structures. The world’s tallest mass timber structure is a 25-story apartment building that opened in Milwaukee, Wisconsin, in 2022.
Although mass timber is relatively new in the United States, it has been used in Europe for decades. The number of U.S. mass timber construction projects is rapidly increasing, with 1,860 completed or planned as of June 2023.
Builders are turning to mass timber because of its benefits. In addition to having a lower carbon footprint than traditional steel and concrete, it is often cost-competitive with them.
Carbon Storage. Trees sequester and store carbon from the atmosphere as they grow. When these trees are used to make mass timber products, some of that carbon continues to be stored and not released into the atmosphere.
Emissions Displacement. The cement and steel industries are notoriously greenhouse gas emissions-intensive and difficult to decarbonize. Building with mass timber instead of concrete and steel could reduce the emissions associated with building materials by 13% up to as much as 26.5%.
Forest Management. Mass timber can promote healthy forest management by incentivizing the removal of small-diameter trees that present a wildfire hazard.
Improved Construction. Mass timber building construction can be faster, quieter, and less temperature-sensitive than other builds. Mass timber also can be more fire-resistant than traditional wood construction, cheaper than concrete and steel, and better at handling earthquakes than other high-rise construction.
Workforce Growth. The global cross-laminated timber industry is expected to have a market size of $3.56 billion by 2030, which could create jobs across the United States. In Oregon, for example, if mass timber design grew to 5% of the state’s construction market share, 2,048 direct manufacturing jobs would be created.
Waste Management. Lower-grade mass timber panels, such as those from diseased or insect-infested trees, are used in non-structural applications like temporary roads and construction platforms, which prevents otherwise undesirable wood from being wasted.
Is mass timber fire safe? Mass timber can provide better fire resistance than traditional light-frame wood construction, but architects must still carefully consider the fire hazards of individual projects. Fire testing has been conducted on cross-laminated timber buildings by the International Code Council (ICC), the Fire Protection Research Foundation, and the U.S. Forest Service, which also conducted successful blast testing. Features like early warning systems, redundant sprinkler systems, and gypsum wallboard can help mitigate fire risk.
How does mass timber affect U.S. forest management? While deforestation is a pressing global concern, the U.S. forest land base has been stable for the last 100 years, and sourcing timber domestically can allow for better sustainability transparency. Sustainable mass timber is transparently sourced from responsibly-managed forests that preserve biodiversity, water quality, and ancient old-growth trees. Mass timber can be made from smaller diameter and less commercially-desirable trees. Regularly “thinning” such trees, which already occurs as a fire mitigation measure, can sustainably supply fiber for mass timber production when done responsibly.
How can we be sure that carbon storage of mass timber is long-lasting? Deconstructing mass timber buildings at the end of their lives and reusing materials for similar purposes is one way to ensure that carbon remains stored and not emitted. Mass timber products can be upcycled as load-bearing columns, beams, and panels, repurposed as furniture, or downcycled into particle board or wood chips. Building projects with a “design for destruction” approach helps architects and designers plan exactly how materials can be recovered, reused, and recycled.
Are there any downsides to mass timber as a building material? Many common types of mass timber tend to dry out more slowly than conventional lumber, which can increase potential for fungi, insects, and mold. Proper moisture-excluding techniques, like the use of naturally-durable wood species and preservative-treated wood, fungicidal and insecticidal shallow barrier treatments, and processes that alter moisture behavior on the wood, can help mitigate moisture problems.
The U.S. Forest Service’s 2022 report, Research Needs Assessment for the Mass Timber Industry, emphasized the importance of “comprehensive, significant, and strategic investments” in mass timber research and development to help support the growing industry and the sustainability and performance of its construction.
The U.S. Department of Agriculture’s Wood Innovations Program creates and expands markets for wood products. Wood Innovations Grants worth more than $14 million have supported at least 60 projects that studied or supported mass timber cost-effectiveness, seismic resilience, fire performance, mold and decay resistance, and more. One grant helped the American Wood Council perform fire safety tests on taller mass timber buildings, leading ICC to allow expanded use of exposed timber ceilings in buildings as high as 12 stories.
The Farm Bill provides further opportunities for mass timber development. Provisions of the Timber Innovation Act of 2017 (S.538/H.R.1380) were included in the 2018 Farm Bill, setting the stage for increased investment in domestic facilities to manufacture mass timber, as well as providing research and technical support to code officials and designers and incentivizing new wood construction buildings.
Authors: Molly Brind’Amour, Savannah Bertrand
Editors: Daniel Bresette, Amaury Laporte, Anna McGinn
For the endnotes, please download the PDF version of this fact sheet.
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