March 12, 2009

COLONIAL BUILDING RESTORATION

Carving of damaged and worn pieces of limestone, full-depth backpointing and replacing existing mortar with a soft-lime mortar are all part of the painstaking job of restoring the façade of the Royal York Hotel to its former glory.

Colonial Building Restoration restores the lady by the lake

Intricate craft required on Royal York job

DON PROCTER

correspondent

These days, Toronto’s Fairmont Royal York is dwarfed by shimmering glass condo towers shooting skyward around the waterfront, but the 79-year-old landmark is still the stately lady by the lake. And Colonial Building Restoration is helping to make sure it maintains its status.

The big Toronto restoration/preservation contractor has started work on the second phase and half of the third phase of an ambitious restoration project that involves extensive masonry repairs and restorative work to the building’s limestone façade.

The contractor hopes to assemble scaffolding this month over a two-week period (depending on weather) and complete its contract commitments by December, says Andrew Lough, president of Colonial. The work continues where phase one (also awarded to Colonial) left off: restoring the rest of the main entrance and the two high towers to its east and west. The work will require a crew of about 20 during peak periods.

The job includes full-depth backpointing, then replacing existing mortar with a soft lime-based mortar between the limestone panels. The existing Portland-cement based mortar, installed about 15 years ago, was “too hard” and caused damage to the limestone, says Lough.

Colonial uses a historic soft mortar recipe that is compatible with the limestone. With any historic masonry structure, a soft mortar ensures that the masonry won’t be damaged when the building moves during weather changes.

“We’d rather have the joint break then the stone break.”

Major jobs like this one require a historical consultant, who provides the mortar recipe and other direction on the work.

In this case, the mortar is made up of one part lime, two parts Portland-cement and eight parts sand — the lime mortar mix for historic commercial buildings like the hotel, says Lough, noting that it is good for the industry to require historic consultants because it helps to ensure that the work is done properly.

To remove existing mortar, a diamond-blade is used to cut through the centre of the joint with the remainder of the mortar removed with hand tools. It is labour-intensive work. For every square foot of limestone, there are two lineal feet of mortar to be removed. Once the new mortar is applied, it is covered with burlap and kept moist with a light mist of water spray for three days to prevent it from curing to fast and cracking, says Lough.

The work is time-consuming, made even more so by the fact the mortar to be removed contains lead. To meet occupational health & safety regulations on lead abatement, the site requires an airtight tarp over the scaffold with negative air pressure machines to prevent dust from migrating outside the workspace. Workers must be certified and wear full respirators, protective suits, gloves and they are required to take showers after each shift.

After each day, the site has to be cleaned and vacuumed with the garbage taken away in hazardous waste removal vehicles to an authorized site, adds Lough.

Minor cracks in the limestone are repaired with an injection of epoxy but more serious damaged stone require “Dutchman” repairs — in which an actual piece of limestone is fitted tightly into the damaged area. Stainless steel pins and lime mortar hold the Dutchman in place, he says.

The contractor will also install a helical tie anchor system to hold the limestone to the structure. A hole smaller than the tie is drilled, then the anchor pin is inserted. The recessed anchor head is covered with a “limestone dust” and epoxy or if it is practical it can be installed in the masonry joint.

On both phases of the contract Colonial will do some Jahn mortar repairs, which is a “patching mortar” that can be molded to the shape of the architectural stone. The mortar is “color-matched” by a specialty lab in Montreal and held in place with a bonding agent.

Lough says while unforeseen circumstances are a part of restorative work, one issue that caught Colonial by surprise in phase one won’t catch them off guard in the next two phases. In the first phase, when crews took down a balcony on the north face they found the limestone cladding was eight inches thick, not four inches thick as it is on the south facing exterior.

To remove the thicker stone for repairs required a chainfall (a pulley hoist secured from the rooftop) because the scaffold couldn’t support the weight of the thicker segments. Lough says a mobile crane wasn’t an option because it would cause too many traffic disruptions. “We chose to do it the old-fashioned way.”

During the next two phases, a key issue will be deciding when to use wall climbers at the two towers. Wall climbers are less expensive than scaffolding and hold only eight to10 workers; scaffolds typically hold a crew of 20 or more. Lough says it is a “fine balancing act,” calculating which method will be less expensive.

Where a reproduction of architectural elements is required, Colonial orders them from specialty shops to make moulds, but they are also prepared to carve elements by hand on site in cases where it is more practical or the stones simply don’t fit as intended.

Lough says one of the biggest challenges at the hotel job is scheduling work so it doesn’t interfere with the hotel’s ongoing operations. In phase one, areas of the work were shut down for up to a week by hotel management.

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