By Lisa Larance, Preconstruction Manager, Swinerton Denver
The mass timber movement continues to gain popularity across the United States as a sustainable and viable option when compared to traditional steel, concrete, and masonry structural systems.
Mass timber buildings, including cross-laminated timber (CLT) and glue-laminated beams, have been constructed in Canada and Europe for decades. Locally, the Denver market presently has two buildings underway; one of which is being built by Swinerton for the Viega US Headquarters in Broomfield. Designed by OZ Architecture, this CLT project consists of a three-story headquarters building and a single-story training center, totaling 78,000 square feet between the two structures.
Despite being fairly new to the US, mass timber structures are no stranger to Swinerton as we are completing a 156,000-square-foot headquarters for First Tech Federal Credit Union in Portland. We are seeing much industry interest as several clients across the country are seeking our knowledge to determine if mass timber is the best structural system for their upcoming developments.
One key to a successful mass timber undertaking is understanding the inherent challenges and intricacies of designing and erecting these structures. Each project team participant faces different questions when considering mass timber. As the owner, is this the structure type you want for your building? As the designer, since mass timber offers a different aesthetic with a greater connection to the environment, is this your vision for the project? For the builder, are you ready to shift your project delivery methodology, enhance your use of technology to lead the industry, and build first? Answers to these questions facilitate the path forward with mass timber.
To begin, the design team should determine if mass timber is the structural system before the Schematic Design phase because it is important to understand how the bay spacing complements the owner’s program. Also, mass timber provides an open wood ceiling condition, and if taking advantage of this option, design for the exposed infrastructure is best determined early in the process. The general contractor is required to understand the most cost-effective way to build a mass timber structure and find schedule efficiencies.
Developing the project team in early design fosters a cohesive environment for making cost-efficient decisions. The mass timber manufacturer should be involved in early design phases too. Each manufacturer, whether Canadian or European, has its own design strategy and framework, and evaluates the project using its own proprietary design guidelines and wood species. For these reasons, including the mass timber manufacturer early in the design process enhances the overall team’s ability to collaborate, design and build efficiently.
Mass timber structures allow engineers to get creative in their design with lighter structures, custom connections and exact production tolerances. The project team must operate with a collaborative attitude to develop the precise structural tolerances that mass timber requires. For example, on the First Tech project in Portland, engineers were challenged to design multiple offsetting connection points to due to the use of larger, heavier beams. Because mass timber structures carry the load more efficiently via different bay spacing than structural steel or concrete, this design differential allows for potential elimination of perimeter beams, resulting in a cleaner, lighter structure which translates into less material to erect, saving time and money.
Building Information Modeling (BIM) is the industry standard for verifying design elements and their spatial requirements within buildings. Now, as mass timber manufacturers integrate during the schematic design phase, the team can ascertain design and production information directly from the BIM model. This aspect is critical as connection tolerances for mass timber shrinks to 1/8” from the typical 1/2” – 3/4” in steel structures. This situation requires development of custom connections – both in size and placement to properly accommodate the building design.
In today’s busy design and construction marketplace, builders are erecting structures at a greater pace, with less room for error. Understanding the challenges of building a mass timber structure takes a dedication to learn, research and collaborate early with partners to deliver unmatched expertise.
This article originally appeared in Building Dialogue magazine.