Material Disruption

Material Disruption

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Ulrich Dangel
Contributed by:
Ulrich Dangel
AIA

Material Disruption: Mass Timber in the Lone Star State

With the attention that buildings made of mass timber have recently received in trade publications and the popular press, most architects and designers are likely familiar with the concept of this new method and its potential to inflict change in the construction industry.

The trend of timber construction in the United States can be traced to the introduction of one particular building product: cross-laminated timber, or CLT.

Originally developed in Europe in the 1990s, cross-laminated timber consists of several layers of lumber board that are stacked at right angles to one another and glued face-to-face to form large-format structural panels up to 10 feet wide, 60 feet long, and 12 inches thick. This cross-lamination yields exceptionally strong and dimensionally stable products with bi-directional load-bearing capacity, particularly suitable for floors, walls, and roofs in multistory applications.

CLT panels have opened up the potential for residential and commercial mid- and high-rise buildings with primary structural systems that are made almost entirely of timber. By combining these planar panels with glulam beams and columns, this novel approach competes with conventional building systems for structural performance. Most important, building with mass timber takes advantage of one of the greatest benefits of wood: its ability to store, or sequester, significant amounts of atmospheric carbon.

Substituting wood for energy- and carbon-intensive materials such as steel and concrete can therefore result in substantial carbon savings over time. Although wood is not necessarily the appropriate choice for all construction, there are clear environmental advantages to using it when possible.

Contrary to popular belief, using wood does not contribute to deforestation as long it is obtained from responsible sources, making it a truly renewable building material. Each log harvested from a sustainably managed forest and processed into lumber makes room for new trees to grow, with the ability to absorb more carbon dioxide from the atmosphere. That’s why well-managed forests can provide greater climate change mitigation than unmanaged forests while also preserving wildlife habitats, increasing biodiversity, and improving water and soil quality. The widespread deforestation occurring in the tropics is rarely related to harvesting wood for construction but instead for clearing land primarily for agriculture, particularly commodity crops and cattle ranching.

While many European countries have used cross-laminated timber products for almost 20 years, the U.S. has been slow to adapt. Pioneer projects here relied on European manufacturers for their panels. CLT fabrication in North America started in 2011, when Canadian companies Structurlam in British Columbia and Nordic in Quebec began operations. The U.S. trailed its northern neighbor by four years, with DR Johnson in Oregon and SmartLam in Montana starting commercial production in 2015. Since then, International Beams (now SmartLam in Alabama) and Katerra in Washington have begun production.

But in Texas, concrete and steel are the building materials of choice. Although dimensional lumber is used extensively for residential and small commercial light wood framing, timber construction has played only a minor role in the state’s architectural discourse.

That’s partly because trees large enough to supply large-scale commercial production don’t grow in much of Texas. Regardless, architects, engineers, developers, and clients today, recognizing the environmental challenges of our times, are looking for new ways to improve the performance of the built environment. As the operational energy consumption of buildings has been vastly reduced, the need to lower their embodied energy becomes more apparent since it makes up a considerable portion [l1] [UD2] of a building’s life-cycle energy use. This is where mass timber and its potential for carbon sequestration comes in.

Fisrt United Fredericksberg | Photo Credit: Taylor Colmen, Gensler

Early Adopters of Mass Timber

Eager to undertake aspirational building projects, enlightened clients have proved instrumental in teaming with Texas architecture firms to employ these novel technologies.

The firm Lake Flato Architects of San Antonio has been at the forefront of bringing engineered wood products to the state. In 2018, the firm’s rooftop addition to the Museum of Fine Arts in Houston — the Sarah Campbell Blaffer Foundation Center for Conservation — featured the first installation of dowel-laminated timber panels in North America. Dowel-laminated timber, or DLT, is created from softwood lumber boards stacked on edge and fastened together using long hardwood dowels, making it an all-wood mass timber product.

Two more of Lake Flato’s DLT projects, the Hotel Magdalena in Austin and the Soto Building in San Antonio, are scheduled for completion in 2020. The latter, a collaboration with BOKA Powell, consists of a glulam post and beam frame supporting dowel-laminated timber floor panels and will be the first six-story, mixed-use mass timber building in Texas. Its well-thought-out systems integration strategy features a raised floor plenum with underfloor air distribution. The result not only maximizes flexibility for tenants, but also removes the visual impact of suspended air ducts while highlighting the beauty of the exposed structural components.

In Austin, TB/DS, a joint venture between Thoughtbarn and Delineate Studio, worked with ambitious client Endeavor Real Estate Group to reimagine a turn-of-the-century warehouse aesthetic for a contemporary five-story office building in its eclectic East Side context.

Completed in 2019, 901 East Sixth is the first Texas project to use cross-laminated timber as part of a composite structural system. Steel beams and columns with bolted connections provide flexible, column-free spaces with an industrial feel while mass timber floor decks add warmth and form the finished ceiling. The hybrid structure went through a yearlong alternate materials and methods approvals process with the city, paving the way for future CLT projects.

For the First United Bank branch in Fredericksburg, Gensler’s Dallas office completed the state’s first full mass timber structure in 2019. The forward-thinking client wanted a building that not only reflected the bank’s strong presence[UD3]  in rural communities but that also aligned with their sustainability goals. Using Southern yellow pine CLT from Alabama, the architects delivered a net-zero energy design with a vernacular yet modern look, showcasing that any building can be a steward for the environment. Gensler is also behind the company’s two other mass timber buildings: an additional retail branch bank in Shawnee, Oklahoma, and a two-story branch bank and office building in Sherman, scheduled to open in January 2021[UD4] .

Kirksey Architecture in Houston is leading the way in the higher education sector with several mass timber university projects in East Texas. Construction for a three-story, 120,000-square-foot classroom building for the San Jacinto College Central campus commenced in November[UD5] . Featuring a glulam post and beam frame, CLT floor plates and CLT staircase enclosures, it will be the nation’s largest instructional building constructed from mass timber when it opens for the 2021-22 academic year.

The firm is also collaborating with American/German architectural practice Barkow Leibinger on a dormitory for Rice University. The five-story, 166-bed Hanszen College dorm will replace an aging building with the goal of making on-campus living more attractive for upper-level students. The university hopes that the innovative design of the building will benefit the well-being of its inhabitants since early studies show that mass timber buildings can positively affect physical and mental health.

Most recently, Kirksey Architecture has begun working on a four-story, 338-bed dormitory on the Stephen F. Austin State University campus. The scheme is in its early planning stages and will include a new dining hall, welcome center, and an addition as well as renovation for the school’s fine arts facilities.

All three higher education projects are supported by federal funding from the Mass Timber University Grant Program, a cooperative partnership established by the U.S. Department of Agriculture Forest Service and the U.S. Endowment for Forestry Communities. This initiative aims to break barriers related to the design and construction of cost-competitive, code-compliant mass timber buildings while showcasing the architectural and commercial viability of these materials in sustainable construction. It also seeks to clearly demonstrate the direct relationship between the use of mass timber products, the health and resilience of American forests, and the potential for economic development in rural communities.

While there are currently no mass timber projects under construction in the Dallas area, several are in the works. Mark Bartlett, regional director of WoodWorks, an organization that provides free technical support for the design of commercial and multifamily wood buildings, is tracking 12 projects at various stages of development in Dallas-Fort Worth.

First United Regional Headquaters | Photo Credit: Alicia Spaete, Gensler

Regional Production

Many mass timber buildings have been completed with cross-laminated timber from European suppliers. Despite the disadvantage of long transportation distances and panel sizes limited by the dimensions of international shipping containers, these products have been very cost-competitive, thanks to the manufacturers’ high production volumes and significant market shares.

North America’s most established CLT production facilities are concentrated in Canada and the northern U.S., which can still present procurement challenges to early adopter projects in more distant states, including Texas.

Each manufacturer offers proprietary panel sizes with different spanning capacities. This means that design teams are often forced to settle on a particular product early in the design process to maximize the most efficient use of material. While selecting a specific company provides access to a wealth of expertise, it also reduces the ability to obtain the most competitive pricing.

There are no CLT production lines yet in Texas that manufacture for building applications, but several suppliers are nearby. SmartLam’s Dothan, Alabama, plant, operating since 2018, is the first one to offer certified CLT products made of Southern yellow pine. Located in Magnolia, Arkansas, Texas CLT[l6] [UD7]  gets its raw materials from within a 100-mile radius of its facility. The company just received final certification and plans to set up a second plant in Jasper, in the Piney Woods of East Texas. [UD8] 

Canadian company Structurlam is expanding its operations to Conway, Arkansas, for its first U.S. CLT and glulam plant, scheduled to open in 2021. About 40% of the facility’s entire manufacturing output will be solely for Walmart for the first three years. The world’s largest retailer has pledged to build its home office campus in Bentonville out of mass timber, and Structurlam will serve as its exclusive supplier.

Anyone interested in building with wood in Texas will surely welcome a ramp-up of production capacities. Broader availability of mass timber products throughout the Southern states will facilitate material procurement, reduce transportation costs, and foster healthy competition between manufacturers. As the number of built projects made possible through regional production grows, the increased visibility is likely to lead to wider acceptance of timber buildings by the public and rising demand for their construction by future clients.

901 East Sixth | Photo Credit: Casey Dunn

Building Taller in Wood

Most mass timber buildings completed in Texas have been permitted as Type III and Type IV construction under current applicable building codes. For these construction types, the 2018 International Building Code, or IBC, allows building heights of up to 85 feet with a maximum of five stories for residential and six stories for office occupancy.

While both types are similar in allowable height and number of stories, there are some notable differences. Unlike Type IV, Type III requires char rate calculations for member sizes to determine residual cross sections for load capacity calculations, which can lead to oversizing of structural members to achieve the necessary fire rating. Exposed steel connections also are not permitted under Type III and require protection. Just these two examples highlight the potential impact of code limitations on architectural expression.

Therefore, it is advisable to engage the local Authority Having Jurisdiction [UD9] early in the design process since it can serve as a valuable partner in selecting the most appropriate construction type. Mass timber structures taller than 85 feet and exceeding six stories are currently only possible in Texas if they undergo an Alternative Materials and Methods Request, a provision in the IBC. That gives local building officials the flexibility to address new concepts, innovations, and developments that may not yet be formally recognized by the current code. Depending on the extent of the request, this can potentially be a lengthy, costly process that might require structural tests as well as fire resistance testing.

In response to the growing interest in tall timber construction, the International Code Council approved a set of proposals in 2019 to allow tall wood buildings as part of the upcoming code changes. Based on the previous Heavy Timber construction type, which will be renamed Type IV-HT, the 2021 IBC will include three new construction types: Types IV-A, IV-B, and IV-C, arranged from the highest fire resistance and safety requirements to the lowest.

For business occupancy, Type IV-A will allow buildings with 18 stories up to 270 feet tall with no exposed mass timber components. Type IV-B will allow 12 stories up to 180 feet with some exposed mass timber elements, and Type IV-C will allow nine stories up to 85 feet with almost all interior mass timber exposed.

Denver, Oregon, and Washington state are among jurisdictions that have already adopted the code changes as a basis for design, before publication of the 2021 IBC. The Real Estate Council, or TREC, a trade organization representing the commercial real estate industry, is exploring early adoption of these tall mass timber provisions in the Dallas-Fort Worth area. Supported by WoodWorks, the American Wood Council, and industry groups, TREC has formed a working group that is in discussions with the city of Dallas and the North Central Texas Council of Governments, an association that promotes the standardization of model construction codes for the region.

The Soto | Photo Credit: Taylor Coleman, Gensler

The Potential of Mass Timber in Texas

As one of the fastest-growing states in the nation, Texas will continue to experience a substantial increase in its population. Most of this growth will be concentrated in urban areas, and the increasing density of our cities will play a critical role in reducing our impact on climate change. Sustainable urban development will need to focus on affordable, healthy environments for living and working while also reducing carbon emissions.

Building with responsibly sourced timber can decrease our reliance on fossil fuels and turn our buildings and cities into carbon sinks rather than sources of CO2 emissions. With wood deemed unsuitable for dense urban environments for so long, the recent development of engineered wood products and amendments to building codes have allowed its return to the city.

Innovative strategies for structural design and fire protection have enabled the construction of multistory buildings that satisfy the most stringent standards, offering opportunities for the emergence of a new type of urban architecture. Increasing demand for timber buildings in our cities will not only ensure that forests remain sustainably managed, but also drive economic development in Texas’ rural areas through new jobs from the manufacturing of wood products. Building with mass timber has the potential for positive impact on the environment, local economies, and our building culture at large.

Uli Dangel, AIA, is associate professor and program director for architecture at The University of Texas at Austin.