The 2005-06 competition for the design of Absolute Towers in Mississagua just outside Toronto in Canada was a privately-run competition open to anyone interested in entering. The following jury shortlisted six proposals from 92 entries.

Thanks to sites such as competitions.org and to domusweb.it, we can still see the six shortlisted proposals.

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The domus.it site listed MAD Office as a USA-based practice and, though there’s probably some reason for that, it’s nobody’s perception of the company.

Nevertheless, the jury chose MAD’s proposal, basically on the back of enthusiasm on the part of the developers, who then instructed the engineers and architects of record to not kill what they liked about the design. The identical floor slabs in the Stage 2 Identical floor plates meant construction could be by usual slip-form construction, but with a rotational displacement for the outer edge formwork. The submitted drawings – the two on the right, below – showed a building with a 360° twist and a structural system for how that might be achieved. [Canadian Competitions Catalogue has more information on the proposal as submitted in Stage I and Stage II.]

Canadian Competitions Catalogue has more information on the proposal as submitted in Stage I and Stage II, but the competition was an ideas competition and so working out how to build and plan the winning proposal came later, with Toronto-based Sigmund Soudack & Associates Inc. appointed as structural engineers. They kept some things and changed or changed back others.

• Their final building isn’t as twisty at 209° but it’s a faithful interpretation and, to my mind, all the better for not going full-circle.
• Their structural followed the idea present in the Stage 1 proposal [left, above], with shear walls simply extending or contracting to suit the rotational position of the floor slab.
• The identical floor slabs in the Stage 2 Identical floor plates meant construction could be by usual slip-form construction, but with a rotational displacement for the outer edge formwork. This idea was also present in the Stage 2 proposal.
• They made the distribution of those shear walls more regular.
• They made the core square to give it symmetry in two directions. (Splitting the elevator bank into two is not ideal but I can see how it would have helped even up the forces when the floors are moving around.)
• They added four more staggered columns that move in and out along the diagonal grid lines, their horizontal moments cancelling at the doubled core.

The architects of record were Burka Architects Inc. (formerly Burka Varacalli Architects) who were architects for three shorter towers on the same site. Internal planning was their responsibility and, though some of the apartments are small, there’s probably a mixture of sizes and their respective numbers as determined by a marketing consultant. Here’s a CBTUH case study paper for further reading.

The apparent fluidity of shape is produced by floor slabs resting on a three-dimensional grid of concrete planes, none of which are particularly thick when compared with those of other twisting towers such as SOM’s Cayan Tower in Dubai. I put this down to the core of Absolute Towers being well integrated with the shear wall structure whereas, in Cayan Tower, the offset columns create torsional forces that attempt to screw the building into the ground, and that can only be countered by “engineering the problem away” – a cute industry euphemism for “more concrete!” – to increase the torsional resistance of the core.

Another problem with twisting towers is what to do with the facade when living spaces extend to the edge of the slab. The image on the right above shows how the load-bearing facade of Cayan Tower is faceted, as it would have to be if you are using parallelepiped-shaped panels to clad between two floor slabs with non-parallel edges. (Calatrava’s Twisting Torso building in Malmo gets around this by having flat glazing units set into specially-curved aluminum panels. $$)

Absolute Towers avoids compromise or complex solutions such as these by the simple decision to set the glazing back from the edge of the floor slab. This leaves balcony edges free to create the shape but also means that external walls can be created by conventional panels and glazing. It also means those exposed balcony slabs become huge reverse radiators sucking cold into the building. The engineers’ website notes that “to address the thermal transfer between the open balconies and the interior, a new kind of thermal break was devised where the balconies meet the wall in two-foot segments alternating with four-foot gaps.” Here’s how it’s done.

The diagram on the left below shows how the incrementally offset walls require additional insulation on the inside when part of the ceiling becomes a roof when the floor above is set further in, and on the outside when part of the floor becomes an external surface. This is just one of those things architects of record are there to sort out.

The visual continuity of that balcony edge isn’t upset by eye-height partitions separating balconies of adjacent apartments. People will surely put chairs and tables and hardy potplants on their balconies but I don’t think it will much affect how the building looks on the outside or how the residents use it for most of the year.

Let’s take another look at those apartments. MAD had eight per floor. Now there are ten, eight of which are between parallel walls and the other two occur when the spaces along the diagonal grid lines are too large to simply be added to adjacent ones. There can’t be twelve apartments because, when two of those spaces are too large, the other two spaces along the other diagonal grid line are too small to be used for anything other than a small triangular bedroom opening directly off the living area. This is simply the price one pays. However, all apartments have living rooms with parallel walls for a sofa and opposing flatscreen, as is customary.

The core is as close as it can get to being bi-axially symmetrical and this must surely decomplicate the structure when the floor slabs keep moving around. The resultant “circular” corridor around an island core allows more flexibility for apartment entrances but, at approx. 49m² per 205m² floor plate excluding balconies, the unsellable area is high at approximately 25%. This and the additional construction complexity meant a build cost 20% higher, but this was recouped by higher selling prices, presumably after maintaining normal profit margins.

The competition winners were announced in 2006 and construction began in 2007 and was expected to have been completed by 2010 but because of the 2008 Global Financial Crisis, only the first 22 storeys of the first tower were completed by 2010. This project could very easily have stopped there and the fact it didn’t, and was completed and opened in 2012 is to the credit of its developer. Half finished buildings still litter Dubai.

No architect wants to get a reputation as developer’s friend so all that remains is to find out what the architect has to say about the project.

Unfortunately, the 1,000 words of text on the competition panels is too small to read. ArchDaily is now the closest thing architecture has to a collective memory and, accompanied by photographs (by Iwan Ban no less), the theoretical argument for the building is made.

It’s a big ask of a simple building with a twisty shape. The argument is that buildings with high energy performance are good, but happier and more sustainable societies will result if buildings are shaped like natural objects that people relate to emotionally. The developer client certainly related to MAD’s proposal emotionally. There must have been phenomenal off-plan demand for Nature because a second tower was duly commissioned, designed and constructed with so little delay that many people believe the two buildings were conceived of as a pair.

This is a link to the developer’s website, showing Absolute Towers as completed and marketed.

This next is a YouTube video of the drive from downtown Mississagua to Toronto. In the first fifteen seconds, you get a feel for the building in context.

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[Cite]

The Uncompleted

Carbon Offset

Spiral Binding