Open rainscreen of weathering steel panels
The three-storey building has four 30m x 12m wings of precast floor slabs, supported on reinforced blockwork piers set between window openings.
The external walls of the upper two floors are clad with white insulated acrylic render.
The external walls at groundfloor level are clad with a series of 4mm-thick weathering steel Cor-Ten panels. The piers are clad with single panels, 930mm wide x 2,603mm high and the window spandrels are clad with single panels, 1,637mm wide x 840mm high. The panels act as an open rainscreen. They are flanked by aluminium window sills and jambs clad with insulated acrylic render.
A series of cladding support brackets of heavy duty hot-dip galvanised steel was bolted to the blockwork piers and spandrels.
Each bracket was specially pressed, profiled and fitted with drain holes to encourage rainwater to run off away from the cladding panel. The brackets were sealed to the blockwork and both were waterproofed with a liquid bituminous membrane. A 70mm layer of aluminium foilfaced insulation was then fixed to the blockwork, with the brackets projecting through it.
The upstand leg of each bracket was wrapped with a separating membrane to prevent panel and bracket touching and to cushion the panel, preventing it from rattling. The membrane overlaps the bracket by 10mm on each side to direct rainwater beyond its edges.
The backs of the Cor-Ten panels were pre-welded with 4mm-thick Cor-Ten 'hooks' - flattened Z-shaped sections - to correspond with bracket positions. Pier panels have six hooks. They were lifted manually into position and 'hooked' on to the brackets.
Lightning protection is achieved by using Cor-Ten connecting bars fixed to studs pre-welded to the backs of adjacent panels.