Modular superslim tower solves an increasing problem in high-density cities
Collins House by Australian architecture and interiors firm Bates Smart shows the potential that can be unlocked when technologically innovative prefabricated construction solutions are applied to small footprint innercity sites, allowing them to become viable for redevelopment.

Australia’s first ‘flat-packed’ slender skyscraper
Collins House, a new 184m residential tower on Melbourne’s Collins Street, is built on a footprint of just 480 sqm. With a height ratio of 1:16, it is Australia’s slimmest tower. Sandwiched between two buildings, its street frontage is only 11.5m wide, which is equivalent to one netball court. It is the first tower in Melbourne to integrate with and cantilever 4.5m over an existing heritage building to increase the accommodation in the sky. A self-supporting H shape plan (with the lifts unusually positioned to the side) enables the whole building to be column free allowing the floor-plates to fill its width.

While some of the innovation lies in the way that the land deals were done, in particular developer Golden Age buying the air rights over the adjacent heritage building to enable the use of the cantilever, most of the achievement is down to design and structural innovation.

Modular construction cut programme from 40 to 30 months
Prefabrication was used extensively to keep the construction period as short as possible. Offsite construction substantially reduced the amount of material and labour onsite which enabled the site to function effectively with one tower crane and one hoist. Each precast floor comprising 150mm thick floor, precast post-tensioned beams and pre-installed facade was craned into place in two-three hours. Coupled with the time saved in setting up and altering the jumpform* meant an overall saving of three-four days per floor.

A prospective milestone for future development
The project has highlighted that prefabrication is particularly useful on small footprint sites with limited access, where the logistics of delivering materials and equipment on site can be particularly challenging.

This design approach solves a problem in Melbourne that is increasingly affecting cities around the world – as city centres become more highly developed, and particularly as more towers are built, sites with large footprints are being ‘used up’ and developers are having to look at sites that previously they would have dismissed. The superslim tower allows them to do this. These methodologies have the potential to be replicated widely elsewhere and could be applied to narrow city sites with limited access around the world.

Hickory’s methodology involved using a mixture of precast panels with insitu components that did not require a jumpform

Quote from Simon Swaney, Managing Director, Bates Smart
“We have been honoured to work alongside Golden Age, Hickory and 4D Workshop to design and deliver Collins House. It is the first superslim residential tower in Australia designed using modular components, a solution that enabled construction on a site that was previously deemed undevelopable. This makes it an extremely unique building. As superslim towers rise in the world’s best cities, Collins House reflects how our firm harnesses innovation and strong collaborative relationships to set new global architecture benchmarks.” --Simon Swaney, Managing Director, Bates Smart