For the first time since the 1960s Montreal office boom, the tallest building in Canada will soon no longer be located in Toronto's Financial Core. Though many projects are in line to overtake First Canadian Place as the country's tallest, the first tower projected to surpass its height is Mizrahi Developments' The One, a 308-metre, Foster + Partners and Core Architects-designed luxury condominium tower at Yonge and Bloor, a couple kilometres north of the current title-holder.

Aerial view of The One, image by Forum contributor Benito

Roughly two years since construction began, some exciting signs of the building's complex structural engineering are materializing at the base of the site's excavated pit. Following the completion of excavation late in 2018, a specialized crane and wide-bore drilling rig were brought in to begin work on the "mega caissons" designed to transfer the future tower's structural loads deep down into the bedrock below.

Base of large columns visible at The One, image by Forum contributor skycandy

These underground mega caissons—measuring 3.65 metres in diameter and extending 30 metres below the base of the excavated pit—were formed in tightly clustered groups over the course of several months. After having their tops exposed with jackhammers, clusters of four caissons are now being covered in thick reinforced concrete caps. The caps are now in place above the majority of the mega caissons, with the remaining caps to be created in the southwest corner of the pit. 

Aerial view of The One, image by Forum contributor thaivic

Enormous rebar cages now extend from the completed caps, marking where the exoskeleton—a structural frame that will extend up and around the tower's exterior—will be attached to the megacaissons. The exoskeleton will allow for largely column-free interiors, while also marking the tower with a futuristic exterior.

Mega caisson cap at The One, image by Forum contributor skycandy

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 field provided at the bottom of this page.

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