Spectaularly transparent two storey high glass stair, cantilever beams cross at the centre of a loadbearing glass drum using moment connections.

The renovation of this historic building presented an opportunity to feature a two storey glass stair, the first of its kind. Extending our single storey glass stair concept to another level involved some modifications to the structural concepts. 

Firstly the stair had to be designed as a gravity supported structure founded on a steel grillage placed beneath the ground floor. The central glass core supports cantilever glass beams which in turn support the outer ring of curved glass stringers. As with our other curved glass stair designs, the outer stringer is laminated from three layers of chemically tempered glass.

The stability of the stair presented possibly the greatest challenge as the building was not particularly stiff in nature. To that end we needed to design a connection between the stair and building to allow enough flexibility so that the lateral distortions of the main building structure would not be transferred to the glass stair. The resulting glass stair does not perform as a stiffening element to the building!

Location
New York

Client
Apple 

Architect
Bohlin Cywinski Jackson