At first glance, Hamilton City Hall (HCH) looks like many other civic administration buildings nestled into downtown areas of cities across the country. Indeed, it shares a problem with many buildings of its vintage in that it was originally clad in a material that was never suited to the Canadian climate. The fact that it had also been designated a Heritage building provided at once a daunting challenge for designers, and a golden opportunity for precast material to once again shine as a versatile problem solver.

Heritage buildings are typically presumed to be those from the first decade or so of the last century. Hamilton City Hall, on the other hand, was built in 1960, and represents the beginning of a new wave of heritage buildings of this ilk that are coming to the point in their lifespan where refurbishment is required.

Although it had undergone minor repairs over the years, the main building and internal systems had not been touched. In May 2007, renovations - including to that of the exterior cladding - were approved to bring HCH up to current code and sustainability requirements. Its Heritage designation also dictated that the structure also retain the “International Style” of Stanley Roscoe’s original design that incorporated some 40,000 square feet of white, gold-veined Georgia Marble that created problems - including anchor failures - from the very beginning.

Because marble wasn’t suitable for the northern climate, designers — heritage consultants VG Architects, included — looked at a number of alternatives. “There are metal panel systems that we could have used to replicate the jointing pattern of the marble,” explains Ross Hanham of Garwood-Jones & Hanham Architects, “but the city was very sensitive to the issue of durability, so metal panels weren’t really considered for very long. We looked at other natural stones, including limestone and other white marble, but they would have cost two and a half and between six and eight million dollars more, respectively, than using precast, which provided the necessary durability, and kept us on-budget.”

Once the team chose the precast solution, there were other challenges to address, including trying to match marble with a precast product. “We had to produce the precast using all-white materials to match the original marble, explains Marc Bombini, Project Manager for precast contractor Tri-Krete Limited, “and we had to give it a very fine finish for the same reason. At the beginning, we were grinding up the existing marble — crushing it and putting it into the precast — working at trying to get samples approved like that, which they didn’t go for, but that was the original intent.”

“When you’re putting on a masonry-type unit onto a structure that is not exactly square and true,” adds Hanham, “you can work with your veneer to make it look square and true because you’ve got all of these little pieces and you can gradually fudge it as you go, so that, to a layperson, it all looks true, but with the precast, because the panels were that much higher, there was some fiddling around required to make sure that the panels went onto the building as square as possible, and to keep the joints as consistent as possible.”

Beyond those issues, it was a piece of cake. . . except for the fact that the back-up wall of the original structure had been retained. The team began to research solutions before selecting one that involved making 16-inch by 12-inch hand holes through the back-up wall, craning the panels into place, reaching through the holes to make the structural connections before filling them back in.

There were pros and cons to that approach, according to Hummel. The pros including the money and timesaving aspect of negating the need to fabricate a structural steel stud back-up. “That was a bit of a pain as far as the site condition,” he notes, “but overall, it was an advantage because we save the city a lot of money in not having to replace the back-up wall, so it was a bit of a trade-off.”

Still another challenge — in this case, for Tri-Krete — was the fact that spray foam was deployed behind the precast, making it tricky to install the precast after the foam had been sprayed. “When you use that spray foam,” Bombini points out, “it’s supposed to expand four inches, but that stuff will keep expanding, so there are a lot of complications and challenges with the foam hitting the back of our precast panels. After we realized this was happening, EllisDon would have to go out and measure everything on site before we came in, and start cutting back the insulation in certain areas just to make sure that it didn’t expand past the four inches that it was supposed to be.”

Arguably the ultimate challenge — one that so often proves the value of precast — was that the building that is already in service. “Everyone — including council chamber, councilors and staff — was decanted to other locations in the city,” says Hanham, “so there was huge amount of pressure to finish the job as quickly as possible; from the time we began to design to when they began to move back into the building was only 22 months.”

OWNER: City of Hamilton, ON
ARCHITECT: Garwood-Jones & Hanham Architects
ENGINEER: ABE Consortium - Ellis Don Corporation and Black and McDonald Ltd.
CONTRACTOR: Schorn Consultants Inc.
PRECASTER: Tri- Krete Limited