The new centre has been created from a six-storey warehouse-like structure. An octagonal tower of red sandstone at the north-west corner housed a water tank for the sprinkler system. As part of the refurbishment, the tank has been removed and a new staircase inserted in the tower from the third floor upwards. It leads to a viewing gallery set behind the parapet. Made of massive sandstone blocks, the tower structure has been stiffened with 305 x 89mm rsc ring beams where floors have been removed.
The helical staircase is designed as a delicate lightweight structure which 'floats' through the massive cylindrical masonry of the tower. A pair of 10mm steel plate stringers form the helical curve; triangular brackets welded to them support steel tread and riser plates, wedge-shaped in plan. 30mm thick oak treads rest on the tread plates. Each baluster, a 15 x 50mm steel flat, is welded to the front edge of the upper tread and to the riser below it, passing through slots cut in the oak treads. The balusters support a balustrade of panels of 3mm perforated steel, and a 42mm diameter stainless steel handrail.
The staircase is suspended from the roof of the tower by four 20mm diameter solid stainless steel rods. The topmost rods are fixed to a beam structure in the tower roof; the lower rods are screwed to support plates at each quarter-turn of the stair. The plates, welded to the stringers, extend beyond the stair and are resin-anchored to the masonry walls.
Cables for low voltage lighting and emergency lighting are concealed between the stair strings. Transformers are set within the oak treads.