Story at a glance:

  • Cross-laminated timber (CLT) serves as a sustainable and lighter substitute for steel and concrete.
  • In London, Dalston Works is built almost entirely of CLT, reducing construction waste by an estimated 80%.
  • Exposed CLT on the exterior of the building 69 A Street creates a much warmer exterior than standard steel.

These examples of cross-laminated timber (CLT) architecture show why CLT is an up-and-coming replacement for heavier materials like steel and concrete.

Cement and concrete manufacturing is responsible for around 8% of global greenhouse gas emissions—more than any country except the US and China. The iron and steel industry are responsible for another 5%, according to a report by the Netherlands Environmental Assessment Agency. To lessen a building’s carbon footprint, architects may try swapping concrete or steel for CLT.

CLT is a type of mass timber that is made from layering boards in alternating directions and bonded with structural adhesive. The alternating fibers make it a lightweight yet strong material. CLT is also fire-resistant.

We created a list of examples of cross-laminated timber architecture that both reduces waste and creates a finished look.

1. Timber Lofts, Milwaukee

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Milwaukee’s first mass timber building harmonizes a neighborhood’s history with renovation through the addition of CLT to the original hardwood flooring. Photo by Roost Photography, courtesy of Engberg Anderson

Timber Lofts—a five-story, 60-unit multi-family complex and 2021 Wood Design Awards winner—is the first mass timber building in Milwaukee. As an adaptive reuse project, the complex with ground-floor retail is a direct reflection of its historic yet trendsetting locale.

“The idea from the onset was to harmonize the existing building with new construction,” Tim Wolosz, principal at Engberg Anderson, told gb&dPRO member Think Wood. “The [developer and contractor] wanted to use cross-laminated timber, and I was thrilled. We were excited about the technology of mass timber and the opportunities it could provide.”

A defining characteristic of the renovation is the preservation of original wood flooring. Individual boards were meticulously deconstructed, stacked, and set aside for cleaning and sandblasting to remove paint, exposing the wood’s maple grain. After subflooring and sound control materials were added, the original wood floor was reinstalled.

After the Timber Lofts project’s completion in Spring 2020, residential units were 90% leased six months after opening, and retail leasing is expected to increase after the pandemic.

2. 69 A Street, Boston

Architecture firm Margulies Perruzzi used CLT to add two floors to an existing brick building in Boston. Photo courtesy of Margulies Perruzzi

Margulies Perruzzi, one of New England’s most innovative architectural and interior design firms, added two stories to an existing 1920s-era brick and beam building by using CLT.

The building at 69 A Street in South Boston was originally designed for industrial use with three floors. The design team at Margulies Perruzzi selected CLT for their construction, as it aligns with the industrial brick and beam nature of the building.

CLT offers new possibilities in wood construction due to its superior strength and stability. Nordic Structures, a company dedicated to engineered wood products in the construction industry, says wood is five times lighter than concrete and 15 times lighter than steel. This allows teams like the one at Margulies Perruzzi to retain the existing structure without replacing or reinforcing the existing foundations. The team left the CLT exposed on the upper floors, creating a much more warm exterior than standard steel.

3. Sideyard, Portland, OR

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Skylab’s Sideyard project in Portland, Oregon, is a commuter-accessible building tailored to the working class. Photo by Stephen Miller

Sideyard emerged from an empty 9,000-square-foot berm to form a gateway between Portland’s urban core and the city’s Eastside. With a focus on commuter accessibility, Sideyard provides retail on the ground floor along Third Avenue and open floor plans above that provide adaptable office and workspace.

“The goal was to provide a noble stage for community activity and future public/private uses. Creating a series of comfortable and inspiring spaces simply framed with a palette of masonry, wood, glass, and concrete,” Jill Asselineau, project director with Skylab, said in a release.

A prominent material used was CLT, particularly inside the building. General contractor Anderson Construction championed the timber for its regional relevance, availability, and simplicity of assembly. It minimizes onsite construction waste and offers high seismic and thermal performance.

Most of the space’s visitors are commuters, considering it is located on the corner of a popular bicycle commuter route. The openness of the communal space promises adaptability to suit the neighborhood’s needs over time.

4. Andy Quattlebaum Outdoor Recreation Center at Clemson University, SC

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The Andy Quattlebaum Outdoor Recreation Center at Clemson University boasts exposed timber throughout the indoor-outdoor building. Photo by Jonathan Hillyer

A combination of beautiful local nature and mass timber construction brings the Andy Quattlebaum Outdoor Recreation Center at Clemson University to life as the university’s first mass timber structure.

Students’ mental and physical health was at the heart of this project by architecture firm Cooper Carry. The firm collaborated with Clemson University’s Wood Utilization + Design Institute on the project. “As advocates for sustainable, wood-based architectural design, the team was armed with a breadth of research to help inspire the Clemson leadership community to have an open mind to this level of innovation,” Brian Campa, principal at Cooper Carry, said to gb&d in a previous interview.

Cooper Carry used CLT slabs for the floors and roof structure. According to Campa, CLT offers significant sustainable advantages, including a lower carbon footprint. “The material is lauded for its ability to achieve long spans. This was one reason the cost of the material was competitive,” Campa said.

Exposed timber throughout the building, coupled with expansive views of the lake and tree canopies, supports student engagement with nature.

5. Dalston Works, London

Dalston Works is one of the world’s largest CLT buildings, featuring 10 stories and 121 residential units. Photo by Daniel Shearing

Dalston Works in London is built almost entirely of CLT, reducing the building’s carbon footprint in both material production and onsite energy consumption.

However, the 10-story, 121-unit residential building designed by Waugh Thistleton Architects doesn’t even appear to be made of CLT. The outside of the building—done in clad brick with steel balconies—was designed to fit in with other buildings in the neighborhood.

When constructing Dalston Works, all CLT components—including floors, walls, stairs, and shafts—were prefabricated and then transported to the construction site. Prefabrication meant less noise and dust onsite, along with less waste and onsite deliveries—which were reduced by an estimated 80%, according to Andrew Waugh, partner at Waugh Thistleton Architects and lead architect on the Dalston Works project.

“Architecture is about humanity. It is about far more than choosing the color of the windows. It is about understanding the implications of your actions as an architect,” Waugh previously told gb&d. “The production of concrete and steel are responsible for 18% of the greenhouse gases in the world. It’s about fulfilling your professional role as an architect and refusing to be marginalized.”

6. The Ecology School, Saco River, Maine

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The Ecology School by Kaplan Thompson Architects contains wall panels from a local white pine company. Photo courtesy of Kaplan Thompson Architects

The Ecology School—a nonprofit ecology education center for students of all ages—is on a historic 105-acre farm on the Saco River in Maine.

The Ecology School, designed by Kaplan Thompson Architects, is made of low-embodied energy materials, including Forest Stewardship Council-wood. The FSC wall panels came from Hancock Lumber, a local white pine company that harvests from their own timber land and manufactures their own wood products.

The school was designed to achieve the Living Building Challenge 3.1 certification. The goal is to create design solutions that actually improve the local environment rather than simply reducing harm. The building will have more than 700 solar panels onsite to support the goal of producing 105% net positive energy.

“Rising to the Living Building Challenge and asking for spaces to give more than they take from the environment around them is a ‘live what you learn’ experience,” Caitlin Brooke, marketing manager at The Ecology School, previously said to gb&d. “You become a living example of how all systems in our world are connected and how daily living can have a positive impact on our environmental health, not a drain.”

7. FABRIC, Reykjavik, Iceland

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Basalt Architects designed FABRIC, an ongoing project in Reykjavik that uses low-carbon construction materials. FABRIC incentivizes alternative and communal ways of living and working—mixing housing, office space, public space, service, and retail. Photo courtesy of Basalt

Well-known Icelandic firm Basalt has been at work on a project called FABRIC since 2017. FABRIC is an eight-story building complex that is deeply rooted in the city’s shift toward co-living and co-working.

Located on the direct route of the new city bus line, FABRIC will soon be home to shared and private co-living spaces, co-working offices, urban farming, retail, a bike shed, and more.

Beyond using geothermal energy like many other Icelandic buildings, the design team at Basalt chose to build with CLT due to its design flexibility and low environmental impact.

“It’s a really active hub—not only the building itself but also how it channels the city through it,” Marcos Zotes, partner at Basalt Architects, said in a previous gb&d interview. “It should promote a healthier way of living. The aim is to have services that reflect this—medical offices, psychology offices, et cetera.”

8. The Environmental Nature Center and Preschool, Newport Beach, California

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The new 8,000-square-foot, three-classroom Environmental Nature Center (ENC) Preschool is the second LEED Platinum Net Zero building on ENC’s 4.7-acre campus in Newport Beach. Photo by Cris Costea Photography

The Environmental Nature Center and Preschool in Newport Beach, California is the region’s first LEED Platinum building.

The building designed by LPA Design Studios features timber FSC-certified wood as the primary building material. The timber in the primary structure and framing system offers a longer life cycle.

The single-story wood frame preschool has been operating net positive since 2008, generating 60% more energy than it’s using. No natural gas is used in the building, and PV panels supply 100% of the school’s power.

9. Yellowstone National Park Youth Campus, Wyoming

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Hennebery Eddy Architects plans on using CLT construction throughout the Yellowstone National Park Youth Campus. Rendering courtesy of Hennebery Eddy Architects

Although not yet completed, the Yellowstone National Park Youth Campus—anticipated to be finished in 2022—is targeting 115% net positive energy and designing to Passive House standards.

The building by Hennebery Eddy Architects uses hydronic radiant heat in the floor and heat recovery ventilators. The team also plans on using CLT not only for practical reasons, but aesthetics too.

“We’re exposing a lot of the interior wood timber and CLT construction throughout to keep the material palette really clean and natural,” Camilla Cok, member of Hennebery Eddy Architects’ sustainability committee, told gb&d in a previous interview. “Then we’re bringing natural daylight in and providing views out to the natural landscape.”

10. Platte 15, Denver, CO

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Platte 15, Denver’s first CLT building, is estimated to achieve a potential carbon benefit of 5,580 metric tons by using CLT as a building material. Photo by JC Buck

Platte 15, a five-story retail and office space, is Denver’s first CLT building. The development team behind Platte 15 was drawn to use CLT because of its sustainable, insulating and cost-effective properties.

“This building will store 1,790 metric tons of carbon dioxide within the wood. Another 3,800 metric tons of carbon dioxide greenhouse gas emissions will be avoided for a total potential carbon benefit of 5,580 metric tons,” says Conrad Suszynski, co-CEO of Crescent Real Estate. “We have proven wood is a cost-viable, sustainable structural option with regenerative benefits for mid-rise commercial construction. That’s a genuine evolution, and that’s a big deal.”

Timber is an insulator, as compared to steel and concrete, which are thermally conductive. Buildings built with mass timber require less energy to heat, cool, and maintain temperature. CLT’s lighter weight also saves money and waste, as it makes the material easier to transport after production.