May 28, 2010

DIAMOND AND SCHMITT ARCHITECTS

In addition to the physical constraints of the Evergreen site, the client wanted integrated architectural, structural and mechanical systems. The project garnered a Canadian Institute of Steel Construction award of excellence in the green building category.

FEATURE | Steel

Don Valley Brick Works project builds upon its legacy of steel

PETER KENTER

correspondent

The Evergreen Commons project at Toronto’s Don Valley Brick Works has restored a group of heritage industrial buildings and added a new one — the Centre for Green Cities, a five-storey LEED Platinum office building incorporating a visitor welcome centre, retail and amenity space, administrative offices and program workspace.

“The Don Valley Brick Works is obviously about brick, but the buildings have been transformed many times over more than a century,” says project architect Michael Leckman, a principal at Diamond and Schmitt Architects.

“Most of the heritage industrial buildings are steel sheds and part of the magic of the site before the Evergreen project was the experience of these very primary and elemental buildings constructed with steel columns and trusses. It wasn’t just the way that the steel accommodated function — a lot of the enjoyment was derived from the buildings in their current state of rust and decay. We used steel throughout the new building to make sure that this continuity was maintained.”

The new Centre for Green Cities building stands apart from the heritage structures on the site of a former brick kiln. Leckman notes while the site provided plenty of excellent raw material for the production of bricks, it provided less than optimum conditions for building a foundation for the new building. The site soil is made up of about eight metres of river sediments and more than a metre of crushed brick rubble.

“That’s just the way they used to adapt the site in the early part of the last century,” says Leckman. “To create a new building, you would knock down the old one and spread the rubble in the soil.”

Reaching bedrock using traditional steel piles was out of the question because the vibrations associated with their installation threatened the integrity of the brick walls of the nearby heritage buildings.

Instead, the foundations were built using steel micropiles, which are installed by drilling through the sediment until they socket themselves into the bedrock.

“The micropiles are only about the size of a person’s forearm and threading these slender elements into the bedrock below causes little vibration,” says Leckman.

But the use of micropiles required the lightest possible structure to rest on them. Again the relative lightness of structural steel supporting precast concrete floor slabs achieved the design parameters.

The voids in the precast concrete floor doubled as wiring and HVAC conduits. This integrated approach also helped the client to achieve the goal of making the project both efficient and sustainable.

Steel was also used in laser-cut sunshades, which grace the building, and on the centre’s front canopy.

Exposed steel was used wherever possible, again, to tie into the structural steel elements of the heritage buildings on the site.

“These steel elements are normally wrapped in drywall or coated with an insulated layer of fire protection,” notes Leckman. “In this case, we used intumescent paint, an engineered coating that provides thermal resistance by expanding only when exposed to a certain level of heat.

This maintained both the aesthetic appeal of the building while meeting the requirements of the fire protection rating.”

Although the new building is integral to the site, it is not structurally tied into any of the heritage buildings.

“We could only use moment joints between the structures because the existing foundations were built traditionally,” says Leckman.

“The existing structures will move slightly as they age, so we need to let them continue to do what they’re doing.”

The general contractor for the project was Eastern Construction.

Structural engineers on the project were Halsall Associates.

Norak Steel Construction Limited provided both steel fabrication and steel detailing.

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