Mizrahi DevelopmentsThe One is being followed more closely than any other project on the UrbanToronto Forum. Located on the southwest corner of Bloor and Yonge streets, the building is central to where several UrbanToronto Forum contributors live or work, and where many pass by on the street, so the number of photos being posted on a daily basis keeps us watching.

Now up to its 11th floor, we have been seeing construction practices of late that we have not seen on project sites elsewhere, so with some explanations from Mizrahi's team and expert contributors from the UT Forum, we're going to take a look at what's been going on lately, in two parts. Today; as crews work on the hotel levels of the building — the 6th through 16th — Forum readers saw that that the outer sections of levels had begun to rise without work happening in the core of the building. Never having seen this happen before, UrbanToronto reached out to Mizrahi, to ask about why this approach is being taken here. 

Levels pictured above the height of the elevator core, image by UT Forum contributor BloorMan

Most high-rise buildings in Toronto have entire floors built through the fly-forming process: forms are created for walls, columns, and slabs that will be used on floor after floor as a building rises. Affixed in place, once they have had conduits and rebar placed between the form sides, concrete mix is poured in and then left to cure. In a few days once sufficient curing has occurred, the forms are disassembled, and their component parts are 'flown' by a crane to the next floor to start the process again. This typical process is how the outer sections of The One's floors are being constructed, with the exception being the corners of the building, where the floor construction is coming quite a bit afterwards: we'll look at that in another story later this summer.

Normally the core of a building is created with the same fly-forming process. Not here though, and because of that, we've seen photos like the ones above and below show a three-storey gap gradually form in the middle of the building where they have not been forming.

A closer look at the levels above the elevator core, image by UT Forum contributor Benito

At The One, Mizrahi's construction team tells us that instead of creating the core of the building with fly forms, they are using an ACS Self-Climbing System that does not need to disassembled after each floor is formed, but the climbing units — comprised of wall formwork and platforms — will rise through their integrated hydraulic systems, without requiring the crane assistance. Using an ACS system for the outer edges of slabs (we've seen this practice in place in a number of buildings in Toronto before), plus building cores/shaft structures is safer while it also speeds up the construction, and so is more cost-effective.

In order to assemble the ACS system in the core of The One, crews need four floors around it. Seen below, crews recently installed 'anchors'…

Anchors installed to be used to attach structure that would support interior floor forms, image by UT Forum contributor Benito

…to which a framework was soon assembled. 

Elaborate anchor structure being installed to be used to form the interior levels, image by UT Forum contributor Thaivic

With the framework assembled, ACS sections were then placed, with this stage resulting, as wall formwork is put in place for a fourth floor around the three-floor gap: 

Floors pictured formed above the elevator core, image by UT Forum contributor Benito

We will be back tomorrow for the next stage in the process.

The One designed by UK-based architects Foster + Partners with Toronto's Core Architects for Mizrahi in Toronto

Designed by UK-based architects Foster + Partners with Toronto's Core Architects, The One is approved at a height of 85 storeys, 308.6 metres. The building is among the pair of projects currently contending for the title of Canada's tallest building, along with the 312.5-metre SkyTower at Pinnacle One Yonge, which is now under construction a couple of kilometres south. Mizrahi Developments has applied for an increase in height and density for The One to rise to 94 storeys and 338.3 metres. If the increase is permitted, The One would take the record as the tallest building in the country.

UrbanToronto will continue to follow updates for this development, but 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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