CMYA Finalist

Employer: Mace

Project: Vauxhall Sky Gardens

Chris Harrison built this mighty residential tower on a site footprint that was tiny in comparison by breaking down the potential adversarial barriers to form between client side and construction team.

Chris Harrison’s 36-storey residential tower project posed the mother of all logistics challenges. The development covered the entire site footprint, access was available only via a 50m-long drop-off zone, the main railway line into Waterloo ran alongside, and there were local businesses in the arches under the viaduct, a nightclub and six different adjoining owners, all requiring party wall awards.

Rotating the tower by 22 degrees during planning simply threw a few more spanners in the works, requiring an oversail agreement with Network Rail. An even bigger problem was that the rotation halved hoisting capacity and vertical transportation for the works. Chris dealt with this reverse by increasing the amount of prefabrication to bring the site operative count down to a manageable level in line with the new hoisting limits. For example, by having most of the service risers and plant made off site, he reduced the total on-site services workforce to a maximum of 70.

He minimised the safety risk to operatives and the general public from structure and envelope construction by deploying perimeter screens and full-height edge protection. He created a clear safe zone between trades by progressing the cladding eight floors behind the concrete frame until the structure was complete. He coordinated the just-in-time bathroom pod deliveries with the progress of the cladding to keep the floorplates as clear as possible, moving the pods into their final position when the floors were encapsulated. The services work started when the structure reached level 5, with riser installations following three floors behind.

The spherical floorplate increased the risk of constructing the tower out of tolerance with the 2,100 cast-in channels needed for the external cladding. Chris dealt with this by prefabricating the steel edge shutters for the concrete floor slabs off site in sections to the exact spherical shape, and adding locating pins to the top of each with dedicated co-ordinates to allow precision installation on each floor. The position of the cast-in channels could then be located exactly by the bolt-on plates that securely held them in place. This approach allowed the channels to be installed to a tolerance of 2mm.

He also prevented the introduction of a mezzanine floor in the basement from delaying the programme by designing it from structural steel members that could be installed using a spider crane. He held back the mezzanine’s construction, sequencing the installation of services and other elements to allow for extra design time. He then used the hole formed for the car lift to lower the steel into the basement, moving it around on trolleys. His solution ensured works progressed as programmed.