The first new office tower constructed in Montreal, Quebec, Canada, in 20 years, Deloitte Tower will have 27 levels above grade and one below. Cadillac Fairview Corporation Limited
Designers are using sloped columns and posttensioned cantilevers to mold an office tower around an existing landmark structure.
May 28, 2013—The first new office tower to be constructed in Montreal in 20 years is being erected directly adjacent to a structure that forms part of a historically important site and therefore must be preserved. The tower will thus feature unconventional framing to ensure that its large floor plates do not interfere with the cultural landmark.
Under construction in the city’s downtown, Deloitte Tower will be bordered by Windsor Station (Gare Windsor), a former train station that has been designated a national historic site of Canada, to the east; Centre Bell, a sports and entertainment complex, to the west; Saint Antoine Street (rue Saint-Antoine) to the south; and a plaza to the north. Cadillac Fairview Corporation Limited, a real estate investment firm headquartered in Toronto, owns the project, which has been designed by Kohn Pedersen Fox Associates, an architecture firm headquartered in New York City. Entuitive, an engineering firm headquartered in Toronto, is the structural engineer on the project in collaboration with Pasquin St-Jean & Associates, an engineering firm based in Montreal.
The 133 m tall tower will have 27 levels above grade and 1 basement level. The building will for the most part house offices but will have retail space on its first and fourth levels, the latter also accommodating the main lobby. The tower’s arrangement will be unusual in that it will have parking on its second and third levels. A three-level parking garage that is being constructed as part of the project below the plaza will offer additional parking. By placing some parking within rather than below the tower, excavation at the site is minimized, says Martine Patenaude, a project management director at Cadillac Fairview. “We’re not going very deep into the ground, so we have a very limited amount of rock to excavate,” she says. The tower will be founded on conventional concrete spread footings, while the parking garage will be founded on steel piles driven to rock.
Sloped columns at levels five, six, and seven will support
posttensioned cantilevers up to 7 m long. Cadillac Fairview
An existing structure on the site known as the Bush train shed must be preserved as part of the project. The last remaining covered canopy of Windsor Station, the shed is part of a national historic site. To protect it, the shed will be dismantled while the tower is being constructed; it will then be repainted and reinstalled at its exact location, directly parallel to what will be the tower’s north side. But because the shed will be so close to the tower, an adjustment had to be made so that the tower’s large floor plates would not compromise it. As a result, the tower will have smaller floor plates at its first through fourth levels to accommodate the shed. Then at the fifth, sixth, and seventh levels, the posttensioned-concrete floor plates will be extended, supported by sloped columns and cantilevering by as much as 7 m. “We had to do this because if we continued vertically, the floor plates of the office tower would be too small,” Patenaude explains. “So we extended the size of the floor plates by extending over the Bush shed.”
The tower will be framed using cast-in-place concrete, and the strength of the concrete in its reinforced core and perimeter columns will reach 80 MPa, Patenaude says. Flat slabs with an average thickness of 200 mm and slab bands with an average thickness of 250 mm form the tower’s floor spans, and 150 mm thick drop panels will increase the strength around the perimeter columns. Each level will have 3.975 m of clearance from floor to floor, typical for an office tower. Raised flooring will cover the tower’s structural system, leaving a 450 mm space for heating and air-conditioning ducts, electrical cables, data wiring, and other mechanical components.
The tower’s south face will also contain sloped columns, but in contrast to those on the north side, these will be sloped to create an architectural effect along the building’s doubly glazed curtain wall facade, Patenaude says. “It’s not a straight, typical curtain wall,” she explains. “It has some articulation.” A recess, or “zipper,” down the center of the facade will impart additional interest. The facade will extend to the top of the tower, where a sloped architectural roof will mask the rooftop mechanical systems and add to the visual interest of the tower. A steel grate structure will cover the sloped roof, protecting the mechanical systems without impeding air circulation.
Deloitte Tower will be bordered by a historical train station to the
east, a sports and entertainment complex to the west, Saint
Antoine Street to the south, and a plaza to the north. Cadillac
Fairview Corporation Limited
The tower’s core and shell are being designed to meet the requirements for platinum certification in the Canada Green Building Council’s Leadership in Energy and Environmental Design rating system, making it the first building of its kind to attain this status in Montreal, Patenaude says. Its energy-efficient features will include sensors that will automatically turn the lights off when a room is unoccupied, and its rainwater collection system will provide water for outdoor irrigation and some bathroom fixtures. “This building has an energy consumption that is at least forty percent less than the standard building and [will] also [offer] a 40 percent reduction in water use,” Patenaude says.
Completion of the tower is expected in the spring of 2015. Patenaude says that when the project is complete, Montreal will have an addition to its downtown that will meet the demands of a 21st-century office. “There’s a new trend in the office environment now where people work with less [enclosed] space, more open space, more collaborative space,” Patenaude says. “This building will be a part of that trend . . . because we don’t have that many columns, and the design of the floor plates makes it easy to create an open-space arrangement.”