Limestone masonry repairs and restoration work to the first three floors of the exterior of one of Toronto’s major hospitals downtown on University Avenue — the Princess Margaret Cancer Centre — is proceeding on schedule.
But the contractor in charge, Colonial Building Restoration, has made discoveries during the restoration process that have thrown a few surprises its way.
Some of the limestone blocks on the façade, for example, are 17 inches deep. That’s 12 to 14 inches deeper than drawings indicate, says Edward Humphries, project manager, Colonial.
Removing these stones to evaluate the conditions behind them is "a slow and methodical process," he says, noting the 850-pound stones took upwards of five days to remove – including one day just to figure out the best removal method without damaging it or its surrounding limestones.
"We have had to be very mindful that they can crack or break fairly easily."
A 20-inch-long flat metal bar custom fabricated to fit into a power chipping hammer to slice into the mortar joints along with wood wedges loosened and eventually freed up the big stones.
Humphries says much of Colonial’s work has started with an exploration into the source and extent of damage. Some of the stones in the walls have, quite simply, moved because of water penetration, entering through rusted metal flashings or shelf angles which were installed to support the stone’s weight and transfer the load to the structure.
Shelf angles in poor condition will be replaced with new ones with rust protective coatings.
A lot of the damaged support shelves are at third floor parapets over the hospital’s main entrance, says Humphries.
Water penetration through deteriorating mortar joints is a major cause; in other instances, cracks in the limestone are the culprit.
Water is also penetrating through undermined window flashings, he says, noting that when the granite base of the hospital was removed for evaluation the structure behind it "was extremely wet."
Humphries says before Colonial was awarded the repairs/restoration contract, few repairs had been done to the building over its 58-year lifespan. One of Colonial’s challenges is performing the work while the hospital remains fully operational. Grinding, drilling and chipping out masonry without disturbing occupants has involved weekend work for Colonial’s crews. Workers have had to be on the ready to move to a different location on the building to manage noise complaints.
"Clinics need to remain in operation during the work and noise complaints can close down the work at any time," Humphries points out.
But noise is difficult to quell during Colonial’s removal of nine large original aluminum windows, says Humphries, noting that the interior job involves breaking masonry joints and ripping out old and deteriorating metal flashings.
While working inside, the contractor must meet stringent infection prevention and dust control protocols, which includes installing enclosures around work spaces as well as sealing all openings (doors and air vents) and hospital equipment.
Colonial’s scope of work also includes removing the portico’s suspended grid ceiling (a modern addition) and overseeing its replacement with a stepped fibre reinforced ceiling that is in keeping with "the age and style" of the hospital, he says. Colonial has subcontracted this work to Formglas Inc.
The masonry contractor also subcontracted work to the Age of Bronze to restore the bronze frame around the glass block wall over the front entry door.
Although Colonial has had access to a condition report (provided by ERA Architects) of the hospital’s exterior prior to bidding on the contract, Humphries says coming up with an accurate estimate of the work is always difficult on older buildings like the hospital until you start peeling back the layers.
The contract is phase three of a multi-phase project for removal of sections of the masonry façade and to review the condition of the existing shelf angles. The next phase – up for tender soon – involves removal of stones to evaluate shelf angles at various parapet levels and the roof. That contract should start in summer.
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