It's been a busy few months at the southwest corner of Yonge and Bloor in the heart of Toronto where Mizrahi Developments' flagship project 'The One' has started its 308.6-metre ascent to the top of the Canada's tallest building ranking. We last checked in on the 85-storey project designed by UK-based starchitects Foster + Partners with Toronto's Core Architects in mid-October, when the final structural steel elements had been erected for the ground floor and its lofty retail space. Much has changed in the several weeks since, with several aspects of the project revealing details of the building's hybrid exoskeleton structural system in the process.

In contrast to a standard structural steel system, the hybrid system employed at The One uses steel elements encased in concrete for extra durability. The first supports to be encased were the eight 40-tonne steel 'supercolumns' around its perimeter, accomplished using large hollow forms placed around the steel columns, and then filled in with concrete. To facilitate the forming of the upcoming second floor, a two-level scaffold and shoring post setup now provides access to the upper reaches of what will be the lofty first floor ceiling.

Looking southwest to The One, image by Forum contributor amlem

Most recently, the laying of floor forms and the assembly of rebar has marked the start of work on the second level. Views from above show the exposed crossbeams featured in our last construction update, now surrounded by the decking that will contain the concrete pour for the level two slab. Levels two and three will largely be dedicated to restaurant/event space, and will see the continuation of the canted steel support columns now extending through the spacious ground-floor retail space. 

Looking south over The One, image by Forum contributor thaivic

Things will get even more interesting in the coming months, with an extra-thick slab above the fourth floor to anchor the central elevator core that will be 'floated' over the levels below. The network of canted support columns starting on the ground floor will continue through the soon-to-emerge second and third floors, converging to support the elevator core's base slab, illustrated below.

Diagram showing the angled columns within the wider structure, image via submission to City of Toronto

To the south and west of the tower's footprint, poured concrete construction is forming the surrounding podium structure to meet adjoining property lines. The western podium volume, housing elevators that will shuttle residents between the ground floor and the residential lobby, now stands level with the tower exoskeleton. The southern podium section lags behind the west section, with forming now moving onto the second level--with floor heights much lower than the flagship retail space to the north.

Aerial view of The One, image by Forum contributor Benito

Among the milestones to follow, the yellow 710 Liebherr crane at the north end of the site will soon be relocated to the top of the sixth-floor south podium with the help of the bulky TG2300 crane at the centre of the site. The 710 crane will then assist in the disassembly of the larger central crane, and climb alongside the tower's south side throughout The One's ascent. This will allow for faster and easier climbing and subsequent removal of the crane.

The One, image courtesy of Mizrahi Developments

Additional information and images can be found in our Database file for the project, linked below. Want to get involved in the discussion? Check out the associated Forum thread, or leave a comment in the space provided on this page.

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