Steel staircase with steel and slate treads
The prototype office building is a threestorey-high steel-frame structure with blockwork cavity walls clad with cedar boards and coloured render. The main entrance, lift and staircase are housed in a three-storey glazed curtain wall enclosure which projects from the main facade.
The lift shaft, an L-shaped wall of fairfaced cast in situ concrete, stands in one corner of the enclosure; the moving lift car can be seen through it.
The staircase half-landings occupy the other corner. The steel strings and the steel frame supports to the half-landings are welded to projecting120 x 80mm RHSs, welded in turn to two 219.1mm diameter CHS columns which rise between the staircase flights from ground floor to roof level.
Each flight consists of a series of 37mm thick slate treads bonded to 12mm steel plates which are welded to stepped 15mm steel strings.The slate treads have a honed finish with a non-slip, grit-blasted strip close to the edge.Landings and halflanding floors are 37mm thick slate strips - matching the entrance foyer floor.Light fittings with diffusers are integrated into the steel structure.
The shaped 80 x 15mm steel-plate balusters stand proud of the treads and landings. They support 15mm ss spigots welded to a continuous 40mm dia ss handrail.Between the balusters run 10mm toughened glass balustrades clamped in steel plates.
At each floor, a 160 x 60mm RHS runs behind the transoms at the inside perimeter of the glazed wall, fixed with cleats to the mullions. The RHS is welded to the balusters at landings and to the lift shaft so that both help to brace the curtain wall. This 'value engineering'solution was cheaper and lighter in appearance than the initial proposal of steel reinforced mullions.