Atrium Stair

Context

A 1970s office block is being opened up around a new central atrium. The architect wants one stair that people actually choose over the lift - visible from the entrance, generous enough to stop on, and light enough not to fill the void.

Constraints

The existing slabs were never designed to take a stair at their edges. Steel has to come in through a single loading door and a goods lift that is 2.4 m deep. The atrium glazing is installed before the stair, so nothing can be swung in by crane once the building is closed.

Scope

Three flights of 10 mm folded plate on twin plate stringers, two intermediate landings, oak treads fixed from below, and a flat bar balustrade with a solid oak handrail. Fabrication, finishing and installation, coordinated with the joinery and glazing packages.

Process

We surveyed the openings after the slab edges were cut and drew the stair around the measured positions rather than the original drawings. Each flight is split into three sections that fit the goods lift, joined on site with bolted splice plates hidden under the treads. The first flight was trial-assembled in the workshop so the architect could approve the visible joints and the paint finish before the rest went into production.

The balustrade infill was set at 100 mm clear gaps and checked against the design loads supplied by the engineer before production. Where the stair meets the existing walls, we left a shadow gap rather than a sealant joint, so the plaster contractor could finish to a clean line without touching painted steel. Site work took eight working days, with the atrium screen protected throughout.

Handover

The client receives as-built drawings, the paint specification with touch-up instructions, and a short care note for the oak treads. The joinery contractor gets a fixing schedule so treads can be replaced without disturbing the steel.