Cross-Laminated Timber [CLT] is still a buzz word for many people—similar to LEED when first introduced to the industry nearly 20 years ago. My two cents for the day: it's time to familiarize yourself. This construction type is poised to change our regional construction and real estate industry significantly over the next 10 to 20 years.
For those new to this term, CLT is a manufactured timber product consisting of dimensional lumber [think 2x4s] stacked in a Jenga-like pattern between 3- to 7-layers thick. This assembly is press-glued together to form a panel that builders can cut through to place mechanical and electrical systems. The panels are prefabricated off site and easily attach to one another once they arrive to a project, expediting construction of the building structure.
As a promotor of sustainable practices who is always curious about the progression of new product types, I stepped away from the job site on November 20 to attend Forterra's Building for a Sustainable Future 2017 where regional and national experts educated attendees on how CLT and the mass timber market will change our state and industry for the better in the coming years.
TOP 5 TAKEAWAYS | THE FUTURE OF CROSS-LAMINATED TIMBER
- Opportunity for denser, economically feasible buildings.
Brock Commons, a residence hall at the University of British Columbia, holds the claim of tallest CLT building in the world at 18 stories [174’]. With concrete shear cores, it is considered a “hybrid” CLT building. This achievement is promising for future developments. Many of Seattle’s recent up-zones in the 85’ to 200’ range are often considered a no-mans-land for developers as concrete and steel building types are too expensive. Without CLT, these areas could end up under-densified in the future.
Improved entitlement process.
One of the biggest barriers to constructing a CLT building is the entitlement process. As of today, the International Building Code [IBC] does not have a provision for CLT under heavy timber. Developers have to follow the prescriptive path, which limits height to six stories or 85 feet, or the performance-based design method where peer review and other engineering requirements add significant duration to the design process. To address these issues, the International Code Council [ICC] established an ad hoc committee to review amendments to the IBC to include CLT. Look for some of the amendments in the 2018 IBC. The goal? Gain full approval for CLT structures in the 2021 IBC. The City of Seattle is also exploring changes to the city code in order to speed up adoption of this building type.
Proving CLT safety.
Authorities Having Jurisdiction [AHJs] are apprehensive in ensuring that new, taller buildings composed of CLT are safe for their occupants. Taller buildings = more occupants = more lives at risk in a life safety event. However, various parties are making progress in proving CLT's safety. Researchers at Washington State University recently received a grant to study seismic events on CLT buildings. The American Wood Council is working with companies like Hilti and 3M to gain approval of rated building assemblies and also recently completed fire testing of a large-scale CLT mock-up.
Resources in our own backyard.
The Pacific Northwest is well-positioned to become the leader in CLT construction given our progressive attitude towards new ideas and the regional abundance of the building material [local materials = reduced carbon footprint]. Researchers at Washington State University concluded that there are multiple locations in the PNW with sufficient timber stock to support a CLT manufacturing plant, potentially creating new jobs in rural communities and helping further distribute the wealth created in Seattle’s current building cycle. In addition, Katerra, a regional supplier, developer, and contractor broke ground on a CLT manufacturing plant in Spokane, WA earlier this year.
Think. Plan. Build.
Unlike high-rise steel and concrete, CLT panels are much easier to prefabricate. However, the prefabrication process requires additional preplanning, trade coordination and building modeling in order to successfully install the panels once they make it to the job site. CLT also requires early involvement of key suppliers and subcontractors to help coordinate the work prior to installation. Many of these traits are already rooted into GLY's preconstruction DNA. I'm looking forward to seeing how GLY's efficiencies and competitive advantages come into play once CLT becomes a construction material of choice.
Continue to look for technological and jurisdictional developments in CLT over the next few years. There are multiple projects in our region poised to begin construction with this new building method.