In an age of shimmering glass and steel mega-structures, the idea of wooden high-rise buildings seems almost quaint. Since the concept of modern engineered-wood buildings was proposed more than a decade ago, however, the idea has caught on in a big way. Today, there are around 50 wood and wood-hybrid buildings proposed, under construction or completed, according to the Council on Tall Buildings and Urban Habitat (CTBUH). In its report, Tall Timber: A Global Audit, CTBUH noted that the phenomenon has gained worldwide interest.
Why construct wood high-rises in the 21st century? In addition to these buildings offering fire protection and seismic resistance, structural strength, easy assembly and weighing far less than concrete and steel, these structures are environmentally friendly: a ton of concrete used in high-rise construction spews a ton of carbon into the air during production; a ton of wood used in a wood mass building has the potential to remove from the air and store up to two tons of carbon for the life of the project.
Further, engineered-wood systems typically use 2X6 lumber to create larger load-bearing components that are culled from sustainably managed forests. According to Sustainable Forestry in North America, less that 2 percent of the standing tree inventory is harvested each year, while the net tree growth in that same period is 3 percent.
The engineered-wood systems used in these high-rise buildings include:
- CLT or Cross-laminated Timber, consisting of three to seven boards that are stacked in alternating directions;
- Glunam, which is two or more layers of boards glued together;
- NLT or Nail-laminated Timber, which is made by stacking lumber together on its edge and nailing it together;
- PSL or Parallel Strand Lumber, which is a composite of wood strands with fibers. It is the stiffest and strongest of the engineered-wood products available and the best for making large beams.
While many tall timber buildings are in the proposal stage, here are two examples that have been successfully completed in the U.S. and Canada and a third one in the proposal stage for Newark, New Jersey.
Brock Commons: Brock Commons, an 18-story student housing project for 400 students at The University of British Columbia’s Vancouver campus, was designed by Acton Ostry Architects. It was completed in 2016 and opened for students in September 2017. Steve White, AIA, principal, Fentress Architects, writing in the Spring 2017 issue of Development magazine, said that it was the tallest building constructed of cross-laminated lumber at that time. He noted that research was underway to explore super tall wood structures with heights of up to 80 stories.
T3 Minneapolis: T3 Minneapolis [T3 stands for timber, technology and transit] is a recently completed Hines project — a 224,000-square-foot, seven-story mass timber office building in the North Loop neighborhood of Minneapolis, designed by Michael Green Architecture in conjunction with the DLR Group. Based on the success of this project, Hines is developing T3 Goose Island, a six-story, 270,000-square-foot mass timber office project on Goose Island in Chicago. Hines noted that the project will be the first wood structured office building developed in Chicago since the 1800s.
Riverfront Square: In February, 2018, Lotus Equity Group proposed an 11-story timber high-rise for its Riverfront Square project, which is a 4.8-million-square-foot mixed-used development on the site of the former Newark Bears and Eagles Riverfront Stadium in Newark, New Jersey. Designed by Michael Green Architecture, the building will rise in steps, ascending from six to eight and then 11 stories. When completed, the 500,000-square-foot building would be among the largest engineered-wood projects in the U.S.