At 200 Rideau Street in the nation’s capital stands a new addition to the Ottawa real estate inventory in the two phases of the Claridge Homes-owned Claridge Plaza. At 25 stories apiece — and with a visual juxtaposition of blue-green glass and limestone-coloured façades — these two buildings add an imposing and impressive feature to the Ottawa skyline.
One thousand pieces of precast were used in the building envelope, predominantly 140 mm thick — the largest being roughly 4.29 m x 2.85 m, and weighing in at 5,000 kilos – except for the cornice, for which special forms were made. The colour of the precast was accomplished without using pigments, which helped to maintain consistency. Instead, a combination of locally sourced sands and stones, coupled with a light sandblasting, resulted in a look described by Magda Zakarian, partner with DCYSA Architecture and Design, as “traditional Montreal limestone.”
Those are the specs, but this project posed several challenges for designer, precaster and contractor.
As the lead architect, Zakarian “had a field day”. Drawing inspiration from similar-looking buildings that DCYSA designed for tony Montreal, she envisioned what she calls a “prestigious and noble” look for the structure, akin to the look of buildings from the 1920s, allowing for much more detailing than a brick tower would employ. “There are a lot of cornices and details,” she says, “especially at the podium level, and in the crowning of the building that you’re not able to do with brick. You are able to create more articulations in the walls; you’re able to do bull noses and a lot of things that you wouldn’t be able to do with a brick building. It’s also a huge complex — especially because of it’s two towers with the connection in between. We really needed all of these details to make the whole thing look richer and articulated.”
All of that articulation created a challenge for Central Precast, according to Lead Estimator Todd Vine. “They had beaks on some of these cornice pieces that stuck out about two feet,” he says, “and in each piece, there were two or three different curves, including some pieces where the curve went the other way.” Vine says they overcame that challenge by creating concrete moulds in lieu of the typical wooden ones. “We actually had to get a product made that was the shape of the piece,” he explains, “and then we poured the concrete around it to make our mould, then we played with it to smooth it all out so that no imperfections would come through.”
There was another wrinkle for the precaster to overcome, according to Joe Zito, Project Manager for Central Precast. “We had some 45-degree corners at the main residential entrance, and that was a little challenging because there was a column immediately behind that was the same width or length as the precast, but connections were designed accordingly to suit that area.”
In fact, those connections also factored into the logistics of hanging over 1,000 precast panels on an infill site where working time was reduced to a 9 a.m. to 3 p.m. schedule - between rush hours, since no streets could be closed for construction. “We had to make the fasteners so that you could quickly pre-hang one panel and then go on to the next,” says Vine. “It’s bolted onto the structure,” adds Zito, “but not into its final position in terms of plumb and level; the connections are designed so that the panel can be adjusted after initially pre-hanging it. The actual final adjustment and welding into place might happen a few hours later or even the next day.”
This system allowed crews to hang a typical complement of 15 panels per day, versus the eight or nine that might have been possible within those restricted hours using traditional fasteners.
Construction was also quickened because precast allowed crews to work through the winter, which of course, would have been impossible with masonry.
The result could be described as majestic. As Zakarian says, precast allowed Claridge designers to “play at another scale and do something impressive in all levels of the building.”
OWNER: Claridge Homes, Ottawa
ARCHITECT: DCYSA Architecture & Design Ottawa & Montreal
PRECASTER: Central Precast, Ottawa