Two-storey helical stair which resolves torsional forces within its spanning ribs.
A Boston Harbour private residence required a centrepiece staircase to connect three levels of a newly renovated condominium.
Eckersley O'Callaghan was charged with designing the structure and aesthetic with minimum connection to the existing building fabric. The result is a two storey helical stair, cantilevering out over a double-height void with no intermediate support between floors.
The structural challenge was to create a delicate appearance, maximising light coming through the bay windows, while maintaining rigidity. This was achieved by the use of two parallel steel spines rigidly connected together by profiled ribs. All torsion forces are taken up by this arrangement, transferring minimal torsion forces into the flexible building steelwork.
Glass treads sit directly on the profiled ribs, supported at two points, and free-standing glass panels make up the handrail and balustrade.