The new staircase - a light and elegant steel structure - rises in an enclosed void which extends from the basement to the fourth floor of the foundation, a late nineteenth-century furniture warehouse. The original cast iron columns have been cleaned and painted, the brick walls have been sandblasted and the enclosure has been lined on one side with a dry-lined plasterboard partition to comply with fire regulation standards.
The stair enclosure is lit by new rooflights, by original windows on each floor and by a new glazed 'slot' at the ground and first floor levels which gives views of the entrance foyer.
A series of landings and half-landings are connected by pairs of steel strings - 200 x 75mm PFC channels - with angles welded between them to support solid ash treads.
Alternate landings are braced by the main structure. Each half-landing, a semi-circular frame of 200 x 75mm PFC channels, is welded to a central support, a 139.7mm diameter CHS column.
Fabricated from sections connected by spigots, the column rises from basement to roof level, tied at first and second floors to the brick walls on the south side and the RHS support framework of the glazed slot on the north side.
The stair has open risers and 35mm balusters with a 21mm diameter balustrade rail - permitted as it will not be used by children. The treads extend beyond the line of the strings 'to express the construction'. They have chamfered nosings to screen the open risers. The asymmetrical handrail, designed to fit the clasp of a hand, was hand carved with turns and 'basketball hoops' at the landings; it terminates in 'dolphin-nose' ends.