The foundations for this concrete structure are 450and 600mm-diameter CFA piles, founded at about 22m. The basement's temporary retaining system was a mixture of sheet piling and vibration-controlled contiguous mini-piling in the zone adjacent to the nearby petrol station. The basement slab is suspended between pile caps and, like the walls, is 250mm thick and designed to Grade 2, Type B water-ingress protection, in accordance with BS8007.
Structural stability is provided by in situ concrete shear walls at the main stair and lift cores. The ground floor consists of 250- and 300mm-thick reinforced concrete slabs in internal and external zones respectively. Between the ground floor and the first floor are 270mm-thick walls that act as deep transfer beams to shift the column grid from one suitable for car parking in the basement to one for the apartments above. These walls divide the units at ground floor. Upper floors are 225mm-deep reinforced concrete flat slabs, but 1,500mm-wide x 350mm-deep beams are introduced to transfer the column offsets due to the floor plate reductions from the fifth floor up. All transfer structural elements are designed as 'key elements', to take accidental loading as specified by BS6399 Part 1. The superstructures are designed to minimise the risk of disproportionate collapse. Staircases are precast concrete supported by in situ concrete landings. Balconies are precast concrete, 150mm deep, insulated from the interior concrete by Halfen HIT balcony construction system.
Peter Matthew, Matthew Consultants