This is an article from our special November timber issue.
The notability of this project is not just its size, but its ability to be a competitive, marketable, environmentally responsible alternative to increasingly affordable steel and concrete construction—an ability we might not associate with mass timber structures. The $130 million project offers 434 units, 130 of which are rental.
According to U.S. Market Development Manager Jean-Marc Dubois at Nordic, a Quebec-based company that, among other services, supplied wood for the project, “The market in Montreal is more suppressed than Vancouver and Toronto. To be able to build means you must have a design that is viable and efficient—something that brings value to the developer. There’s a lot of press surrounding high-rise wood construction, but Arbora shows there’s a place for affordable, viable mid-rise construction.”
Arbora involves cross-laminated timber (CLT), composed of layers of dimensional lumber stacked perpendicularly and glued together to create structural panels. CLT panels are typically made of layers of three, five, or seven, and, because they offer two-way span capabilities, can be used for floors, walls, and roofs. The result is a material that is lightweight, strong (up to seven times the strength of concrete), efficiently shipped, and less labor-intensive than its steel and concrete counterparts. “With mass timber structures, you can use less employees and get more work done,” said Dubois. “There’s a shortage of skilled labor across North America, so the fact that you can raise structures with considerably less skilled employees is very critical. Typically we operate with as few as four to six tradespeople on a jobsite. The output per person is much greater.”
These benefits come with a cost, however: increased upfront coordination and design time. Engineered wood components are designed, optimized, cut to millimeter precision, and then shipped to site for assembly. Dubois reports that Nordic is involved on multiple fronts of mass timber projects like Arbora, coordinating design, engineering, fabrication, construction sequencing, and regulatory parameters. “This is one of the things that distinguishes Nordic,” he said. “There’s a tremendous amount of involvement and engagement with our team that you don’t necessarily see as you’re looking at the construction process. We’re taking an active role in the design process, in addition to sitting in meetings with local authorities.”
The key to Arbora’s commercial success in a competitive housing market is design efficiency, and an acknowledgement of the inherent structural properties of CLT from the outset of a project. “There are efficiency gains in replication,” Dubois said. The project was organized around a 20-foot grid, an ideal structural span and shipping dimension for the beams and panels. The consistency of the grid allowed an efficient manufacturing process, and abbreviated on-site assembly time.
Early adopters of CLT in North America have tended to be more custom projects like schools and sports venues, but Dubois sees demand for mass timber shifting into commercial real estate, namely office workplace typologies, where the unique look of a wood structure can offer differentiation in the marketplace.
Mass timber adoption in the United States has lagged behind that in Canadian markets. Dubois attributes this to a number of factors including the litigious nature of the United States, and the tendency of Canadian authorities to be receptive to performance-based design. “In Quebec, we don’t promote one building material over another, so we have to make a market against steel and concrete, which is exceedingly inexpensive,” he said. “We have to be economically viable and prove we are meeting the same structural and safety requirements that other systems must abide by.
“Performance-based design typically runs into more red tape in the United States,” he continued. “I think it’s a fear of the unknown. This has led the American Wood Council, the U.S. Department of Agriculture, and the wood industry to promote the tall wood agenda, to try and get coded options so that it is prescriptive as opposed to alternative means and methods.”