[WORKING DETAIL 29.04.10] Staircase detail
Leaf House − The main staircase, which rises from the basement to the second floor in three flights, is less simple than it appears. It has invisibly jointed matt sealed walnut handrails with a diameter of 40mm – the minimum required by Part M of the Building Regulations. These splice with matt-lacquered steel handrails in the curved sections that form the transition from the flights to the landings. Steel is a more suitable material for the construction of the subtle curved sections of the handrail. It also sends a tactile signal at the ends of the flights for the benefit of people with visual impairment.
The handrails are supported by 15mm-diameter lacquered steel balusters, at 127mm centres on the straight sections of the balustrade, which pass through pre-drilled circular holes in the limestone treads and sit in steel housings at the connections to the concrete structure. These connections comprise steel plates bolted to the vertical faces of the concrete. The balusters on the flights and landings are carefully aligned with each other.
Initially, the contractor aligned and adjusted the balustrades, treads, landings and the landing flooring on site. The balustrades were then returned to the factory for completion and application of the finishes by their manufacturer, Specialized Fabrications. At the final installation stage, the balusters were resin-bonded to their housings and flush-grouted into the openings in the treads with stone-coloured mastic.
The soffits and sides of the slabs are clad with skimmed gypsum board, fixed to timber battens and dabs. This cladding conceals the connections to the concrete and is flush with the edges of the stone treads, risers and landing floor, with a 10mm shadow gap at the junction.
James Gorst, principal, James Gorst Architects