Webb Yates Engineers completed the structural design for a series of cantilevered stone staircases for a private dwelling in Knightsbridge, London. The stone was hand cut from Branco do Mar limestone using traditional tools and techniques and designed using complex 3D finite element analysis.
The first stair was designed using centuries-old principles but refined with a thin elegant stringer line and a geometric soffit profile. Each tread tapers from wall to tip creating an origami effect which adds geometric interest to the stair soffits, and also reduces the weight of the stone treads. A cantilevered glass balustrade with a notched edge is set into a groove cut directly into the solid stone, avoiding the need for expensive and unsightly fixings and giving a clean, elegant fascia.
The second stair is suspended by a folded steel strap hanging each tread from the tread above. The steel ribbon works largely in tension and is connected via a series of discrete steel dowels with recessed pattresses. These dowels act to embed the strap into the stone and transfer tensile loads from the steel, to compressive loads in the stone harnessing the best qualities of each material. The design pushes the properties of stone to its limits but allows light to penetrate through the stair through a glazed floor to a basement swimming pool below.