Move over, steel. Wood is taking center stage in a surprising number of tall-building construction projects. In London, England, a developer has proposed a 100-story wooden tower nicknamed “the Splinter.” This year, a £44 million project to build a 276-foot (84-meter) “plyscraper” in Vienna, Austria will enter its construction phase. But as wooden buildings rise to new heights in Europe and North America, project teams are contending with new kinds of challenges, including navigating building code restrictions and overcoming the learning curve of working with a new material.
“Builders have pushed past the old limitations.”
—David Barber, Arup, Washington, D.C., USA
“There's been a resurgence in taller wood buildings globally, and as these new technologies—in engineered wood products and engineering and design—are proven, builders have pushed past the old limitations,” says David Barber, principal engineer, Arup, Washington, D.C., USA.
In Vancouver, British Columbia, Canada, construction is already underway on the US$51.4 million Brock Commons project. Slated to be completed next year, the 18-story student dormitory at the University of British Columbia will be the tallest wood residential building in the world. Project plans combine cross-laminate timber floor slabs with concrete cores and steel connectors. By prefabricating materials off-site, the project team aims to hit a construction speed of one story per week. Thanks to a two-story pilot project successfully completed earlier this year—before the Brock Commons’ full construction-phase schedule was approved—the project team is confident it can maintain the fast pace.
“The design phase for one of these wood projects is comparable to any other material, but the construction is much faster,” says Robert Malczyk, principal engineer, Equilibrium, Vancouver, Canada. Some project teams for tall timber buildings have shaved as much as 10 weeks off their schedules compared with steel projects, says Mr. Malczyk, who has been a part of plyscraper project teams for 15-plus years. Past projects include the Frank Gehry-designed Art Gallery of Ontario in Toronto, Ontario, Canada and the Raleigh-Durham International Airport roof structure in Morrisville, North Carolina, USA. “The construction is much faster, but it's also much quieter,” he says. That's made wood building projects particularly popular in dense urban areas, where noise complaints from community stakeholders can slow or stifle a project's progress. And compared with steel, there's much less construction waste, Mr. Malczyk says, because prefabricated wood products can be precisely milled and designed off-site beforehand.
Brock Commons’ wooden inner structure; below, the building under construction
Location: Vancouver, British Columbia, Canada
Budget: US$51.4 million
Scope: 18-story student dormitory to house more than 400 students. Will include nearly 300 studio apartments, as well as common areas, lounges and study spaces.
Scheduled completion: 2017
Location: Bergen, Norway
Budget: NOK220 million
Scope: 14-story timber tower comprises energy-efficient, stacked prefabricated modular apartments.
Completed: November 2015
Location: London, England
Scope: 10-story, 121-unit residential plywood building will be the largest timber building by volume when it opens.
Scheduled completion: 2017
Location: Vienna, Austria
Budget: £44 million
Scope: 24-story plyscraper containing a hotel, offices and apartments.
Scheduled completion: 2018
Environmental benefits extend to the atmosphere. Building a 20-story plyscraper rather than a concrete or steel building of the same height prevents carbon emissions equivalent to what 900 cars produce in a year, according to Michael Green Architecture, an architecture firm in Vancouver, British Columbia, Canada.
Against the Grain
The faster, more flexible construction phases enabled by wood products seem like a win-win-win. But plyscraper project managers should be prepared for a few unusual requirements. Most local governments have code regulations restricting tall timber buildings, says Mr. Malczyk. Exemptions are common, but most projects must include both funding to contract a code specialist and the schedule flexibility to secure necessary approval.
Because tall timber buildings are less common than steel skyscrapers, project teams face a learning curve related to dealing with unique materials. “Durability, fire and acoustics are the main issues that affect all buildings—but in different ways depending on the materials,” says Mr. Barber, who's served as a fire engineer for several tall timber projects. Sound passes through wooden floors and walls more easily than concrete, for example, raising noise concerns for stakeholders. A project team might have 50 years of collective experience with solving durability, fire and acoustic issues in steel buildings, with a rich library of mitigation techniques. “With wood buildings, the construction and types of materials aren't as familiar, so there isn't that same catalog of solutions,” he says. Eventually, solutions to wood-related challenges in tall buildings will be widely known, but right now, solutions tend to be “more unique and one-off for each building.”
“The design phase for one of these wood projects is comparable to any other material, but the construction is much faster.”
—Robert Malczyk, Equilibrium, Vancouver, British Columbia, Canada
In general, that means project practitioners can expect to allot more of the schedule to the design phase, so engineers, code specialists and fire experts can tackle issues unfamiliar to even veteran team members. But the good news is that extra time up front can likely be made up for during a shorter construction phase, Mr. Barber says. “And less time on-site means less money spent on the building.”
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