Dive Brief:
- Real estate company Brookfield Properties has announced plans to build the largest mass timber office building in North America at its 28-acre Pier 70 waterfront development in San Francisco. The company predicts construction will take six months less than erecting a concrete building of the same size.
- When finished, the office will stand 85 feet tall, with six floors totaling 310,000 square feet, according to Brookfield. The building will be the first new office at the development, a $3.5 billion waterfront site with housing, parks and rehabilitated historic buildings.
- The mass timber structure will utilize cross laminated timber (CLT) for floor slabs, glue-laminated timber (glulam) columns and beams, steel lateral seismic framing and metal cladding. CLT is a relatively new building material that can be used for mid-rise buildings, and the building's CLT floor panels laminate layers of solid wood that change direction in each subsequent layer, making the panels strong in two directions and giving them comparable strength to traditional building materials like steel or concrete, according to the firm.
Dive Insight:
At the end of last year, the University of Arkansas announced the construction of what it said was the country’s largest mass timber structure: Adohi Hall. The residence hall will be about 202,000 square feet, less than Brookfield’s planned office building.
The new San Francisco building will feature CLT panels that will hide utilities from view, with cables and pipes running between slabs. At the ground level, Brookfield plans to include a retailer, restaurant and bike lounge.
The lead designer for the building is Portland, Oregon-based Hacker Architects, which specializes in mass timber use and is headquartered in a CLT building.
Mass timber can be costlier to build with than steel, Brookfield said in a press release, but total construction costs can be offset by lower foundation costs. Plus, offsite prefabrication is done in advance of the building assembly, speeding up construction.
Wood structures perform well in seismic events since they are light and flexible, making the material more attractive in earthquake-prone areas like California, Brookfield said.
The use of mass timber for building projects has created controversy, often due to fire safety concerns. The development of new safety codes have begun to set parameters for using the material. Later this year, the International Code Council will release 14 new code changes for tall wood construction that will be incorporated into the 2021 International Building Code.
The building technique will soon be used on a Washington, D.C., office project as well. Columbia Property Trust recently announced it will build the first commercial office building in the city featuring mass timber construction.
The 105,000-square-foot vertical expansion of 80 M Street, an existing 286,000-square-foot office property in the Capitol Riverfront District, will consist of two new floors and a penthouse to be built atop the existing property.
