There are 15,522 pieces of sandstone covering the exterior of Calgary's Historic City Hall, a well-known landmark in the city's downtown that was built between 1907 and 1911. Of those pieces of sandstone, 15,142 pieces will be "touched" in some way, as part of the rehabilitation of the 106-year-old building.
"We're touching virtually every one of them," says Darrel Bell, the Manager of Facility Infrastructure at the City of Calgary, explaining that some bricks only require cleaning, while others need to be replaced entirely.
The question begs to be asked: How does one know there are 15,522 sandstone blocks?
Bell says the answer is technologically simple: They were counted. "Professional heritage conservators went around and evaluated each piece of sandstone. We're investing the time and money now so the building will be around for another 100 years. That's the treatment the building deserves, and that's what it's getting," Bell says.
The city has been working on the $34.1-million Historic City Hall rehabilitation project since 2015 after a piece of sandstone fell from the building near a light rail transit platform. Bell says that served as the catalyst for the city to start looking at the structure and deciding what needed to be done.
"A lot of things had happened to hasten its deterioration," Bell says, noting there had been some "well-intentioned" attempts at preservation in the past that had only exacerbated problems. Furthermore, nearby buildings were causing shading, inhibiting the sandstone from drying out, another factor contributing to deterioration.
So far, crews have finished refurbishing the foundation blocks underground and have installed a rainwater management system around the building.
Currently, crews are erecting scaffolding around the sandstone edifice in preparation for the exterior rehabilitation. "Everything needs to be protected from the weather, so the entire building will go under a PVC wrap," Bell explains. And it won't emerge out from under its temporary covering until July 2020, when work on the building is expected to be complete.
"This is the second-largest project of its kind in Canada today. A project like this doesn't happen very often," Bell says, noting that Calgary's Historic City Hall is the only surviving city hall of its period in Western Canada.
And that presents some challenges. Among them? Securing the necessary trades, from architectural conservators to stone masons to woodworkers. "We've gone country wide in our search for trades," Bell says, adding that Toker + Associates Sustainable Architecture + Interior Design is serving as the primary consultant with Montreal-based Evoq Architecture working as a sub consultant on the project. (The general contractor is EllisDon.)
Another challenge? The sourcing of materials. "Because it's a national, provincial and municipal heritage resource, there are regulations governing how it can be rehabilitated," explains Bell.
While modern technology doesn't come into play much with a historic rehabilitation project, it does in the sense that crews will reference an electronic model of the building — storing the information the historical conservators gathered — to see what actions need to be taken to restore each brick of the building to its former glory.
While replacement sandstone will arrive pre-cut, stone masons will be on site to do the detailed carving to ensure each new block will fit in with its surroundings. This is the kind of precise work that takes time, says Bell, and accounts for the fact the Historic City Hall rehabilitation project is more than three years away from its completion date.
Bell says the building's original window frames will be preserved and restored, but the glass window panes will be replaced. The project will also see the roof re-done, structural rehabilitation of verandas and balconies, and new structural steel inside the 100-foot clock tower from the third floor and up.
The City of Calgary will be posting project updates on the rehabilitation of Historic City Hall at Calgary.ca/HistoricCityHall.