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An historic transformation is underway at University and Dundas in Downtown Toronto. The heritage 1928-built Maclean Publishing Company and the 1961-built Maclean Hunter buildings that have sat on the northeast corner for decades are currently undergoing quite the process, on their way to being the restored limestone-clad base of what will be Davpart's The United BLDG. Including new retail and office space behind the restored facades, The United BLDG will boast a B+H Architects-designed condo tower rising 52-storeys behind them. The work to bring it all about is requiring North America’s tallest heritage retention development. We took a trip down to see what is going on at the site behind all of the hoarding — read on to learn about what we found!
The site used to hold four office buildings – although only the grander two are being retained as part of the new project. The buildings that formerly sat at the northeast corner of the site on Edward Street and Centre Avenue have been fully demolished, and the space where they once stood is now home to a delivery area, a portable crane, and a scaffold deck. When we visited, crews were busy importing large steel transfer trusses into the first level of the University Avenue-facing building.
"The trusses are roughly 20,000 pounds, or 10 tonnes each," Kevin Ryan, EllisDon Site Superintendent told UrbanToronto.
The trusses are being installed on the first level of the original structure, and are being used to support the weight of the upper levels of the University Avenue building. This is necessary because there is currently one existing underground level below the existing structures… however three more are in the plans for the new development. What must happen is that the weight of those upper ten floors must be borne onto the transfer trusses, which will take the load outside of the building so that crews will be able to dig below the existing structure, without it collapsing.
"At every column line, we're installing a truss in order to pick up the building load, that way we can remove the foundation, and dig underneath it," said Ryan.
Once the trusses are unloaded from a truck, they are lowered onto a specially-built steel dolly that is hooked to a rope. The rope is fed through anchors that are fastened to the floor slab, and finally attached to a motorized cranking machine positioned at the opposite end of the same level, that pulls and coils up the rope. As the dolly is slowly being pulled through the first level by the machine, crews surround it, and guide it into the correct spot, before it is tipped out of the dolly and fastened into place.
"On average, we do two a day," said Ryan. "Today is a good day though, because we already did two this morning, so we'll be able to get four done." "After this," he continued, "we have 12 more to go, since there are two needed per-bay."
The load must be transferred to the exterior perimeter of the existing structure, which had a narrow trench dug around it that is now filled with four to five feet of reinforced concrete — creating what is called a grade beam — that will bear the load as the underground levels are dug.
"The first thing we did was drill piles around the exteriors of both of the facades – the grade beam sits on top of those piles, and that's what transfers the load away from the building's foundation," explained Ryan. "The hardest was Dundas, because of the sidewalk, so we actually had to do the entire thing below grade, and then reinstate the sidewalk."
"All of the retention steel is within one bay inside the building, so we'll be picking up an entire column bay around the whole building to retain the facade," said Mark Hamidi, Davpart Director of Development.
The University Avenue building is a steel structure, so this truss-work will only be necessary to dig below the part of the site that it covers. The Dundas building is a concrete structure, so a different approach must be taken. Ryan told UrbanToronto that they expect the truss work to be done on the University building by the end of this (current) week, weather permitting. He said only then will they start to work on supporting the Dundas building.
Once the first bays of both structures are supported and their weight is transferred to the outside of the building (onto the perimeter grade beams), then the demo of the backsides of the buildings will take place. "After that is done, we will jack the entire building onto some interior piles," said Ryan. Once the debris is removed, the crews will be able to start digging the underground levels.
The United BLDG will eventually be the home of a B+H Architects-designed mixed-use 52-storey condominium, which will have offices and retail at the base within the 10-storey restored heritage facades, with new residences rising from above.
Stay tuned! We will be back next week with a story about the heritage restoration project going on as part of the new development. In the meantime, you can learn more from our Database file for the project, linked below. If you'd like, you can join in on the conversation in the associated Project Forum thread, or leave a comment in the space provided on this page.
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