Wood is making a comeback: let’s talk about mass timber

Used in construction for thousands of years, wood is one of the longest standing building materials. In the mid to late 1800s, builders began replacing it with concrete and steel, which were gaining a reputation for strength and durability. But today, wood is making a comeback: mass timber, a relatively new way of using wood in the U.S., is making headlines thanks to its many benefits. This structural framing system, made of solid heavy timber or engineered wood members, is most often used for wall, ceiling and roof panels. Sustainable, cost-effective and schedule friendly—mass timber is a building material worth considering.

1 / 4 –Our Bend Metro Parks and Recreation District’s Administration Building project in Bend, Oregon is LEED® Gold certified and uses both wood and steel framing, which adds a welcoming, park-like experience. The large outdoor terrace creates an inviting entry to an information lobby and large community room. Sustainable features were important to the client, and along with the use of mass timber, the project features radiant floor heating, daylight harvesting, an eco-roof and solar hot water.

2 / 4 –Our 203,000 square-foot Vancouver Public Schools, McLoughlin Middle and Marshall Elementary School project in Vancouver, Washington is one of the largest mass timber projects in the Pacific Northwest. The school district decided on mass timber due to its sustainable features, along with the warmth and natural aesthetic it brought to the schools. The project features a variety of unique structural components including exposed slab-on-grade concrete slabs, complicated exposed concrete tilt panels, steel hollow structural sections with wood framing and exposed cross-laminated timber (CLT) diaphragm supported by glue-laminated beams.

07-mass-timber-structure-at-the-kendeda-building_48911397482_o

3 / 4 –The Kendeda Building for Innovative and Sustainable Design is the first academic and research building in the Southeast to pursue Living Building Challenge 3.1 certification. Located on Georgia Tech’s campus in Atlanta, Georgia, this net-energy-positive building is the first global example of using salvaged materials in a mass timber project. Kendeda incorporates nearly 500 nail-laminated panels crafted from salvaged 2x6s and 2x4s (previously used for local movie and TV productions) for both structure and interior surfaces.

4 / 4 –Our City of Beaverton, Public Safety Center project is a three-story public safety center for the Beaverton Police Department and Emergency Management Operations in Beaverton, Oregon. Built to higher-than-standard seismic resiliency, this hybrid structure features a steel frame with CLT floor and ceiling panels. The natural wood brightens the building’s interior and adds to the strength of the structure.

Lower carbon emissions

Over the next ten years, approximately 80 to 90 percent of the carbon emitted from new construction will be embodied carbon—the emissions associated with building construction, including extracting, transporting and manufacturing materials.

Building with mass timber—when compared to concrete or steel—reduces a structure’s carbon footprint because wood is a lower carbon material. Additionally, mass timber is a renewable resource that can be sourced locally from sustainably managed forests, reducing vehicle miles traveled. A team at the University of Washington recently ran a lifecycle analysis comparing a “hybrid, mid-rise, cross-laminated timber (CLT) commercial building” to “a reinforced concrete building with similar functional characteristics.” They concluded that the CLT building represented a 26.5 percent reduction in global warming potential.

Reduced cost and schedule

Using mass timber in buildings can speed up the construction schedule because it requires less labor, equipment and tools on the jobsite. The wood can be detailed, designed and prefabricated in an offsite shop, so when it’s delivered to the site, workers are simply linking pieces together.

When it comes to using mass timber for beams and columns, the mechanical and electrical penetrations can be drilled offsite. It’s much safer, quicker and cost effective to have these penetrations performed within a controlled environment than to have the work performed onsite. With field cutting eliminated, further work simply requires mechanical, electrical and plumbing subcontractors on site to place the ducting, electrical cables and other items.

Mass timber panels can be fabricated in a variety of widths and up to 40 feet long, so this type of building material is very conducive to large, rectangular-shaped buildings. When used in buildings that are more symmetrical, mass timber is erected faster than traditional concrete and steel structures, reducing time and contributing to a more cost-effective system.

Enhanced performance and safety

Because mass timber panels, posts and beams are glued together under high pressure in stacked, perpendicular layers, it’s a strong and reliable building material, quite comparable to concrete and steel. Mass timber buildings may also feature a hybrid of materials and systems, including a structural steel system with CLT floor and roof panels, concrete shear walls or CLT panels for shear walls.

Mass timber has fire-resistant properties: during a fire, a char layer forms on the material, which creates a protective layer around the wood, preventing further damage.

Design aesthetics

The aesthetics of a building material should never be discounted as they can add striking elements to any project. Mass timber may be left unfinished—a purposeful choice that adds a rustic, natural and even streamlined look, while eliminating added costs such as wall finishes. The aesthetic nature of wood allows for unique architectural designs to stand out in building interiors and exteriors.

Considerations and limitations

Though mass timber is common throughout Europe and Canada, it’s a relatively new construction method in the U.S. When it comes to building with mass timber, experienced design and construction teams provide added value to an owner who is interested in using this system. To date, Skanska teams have completed 12 mass timber projects across the country with more on the horizon. This includes the McLoughlin Middle and Marshall Elementary Schools in Vancouver, Washington, one of the largest mass timber projects in the Pacific Northwest.

Building for a better society

At Skanska, we aim to improve the communities in which we live and work, recognizing that we’re accountable to future generations. Combatting climate change by reducing carbon emissions is a critical focus area for industries and companies across the world—and Skanska is no different. We see mass timber as an important step in reaching our group-wide goal of achieving net-zero carbon emissions by 2045 within our own operations and across our entire value chain.

If you’re interested in learning more about developing a mass timber structure, reach out to myself or Senior Vice President – Regional Director of Preconstruction Steve Clem. Meet the rest of our Portland team here.