Tension Net Stair

ABOUT

The Tension Net Stair is the sculptural centerpiece and only stair in a two-floor penthouse apartment of a mixed-use tower in downtown Chicago.

The thin concrete floor slabs could not support the load of additional construction so the staircase is suspended from steel beams below the ceiling slab. The central tapered and conical tension net of stainless steel rods is stiffened by post-tensioning against the lower floor and a series of integral horizontal compression rings. The mass of the glass stair treads also helps stiffen this net. The delicate woven structure appears as a vortex around which the acid-etched laminated glass treads are spun.

The treads are three-ply lamination of acid-etched and annealed glass with a total thickness of 32mm. They are supported along two of their three sides by nylon strips on aluminium bars. The use of laminated glass achieves a combination of mass (which helps to tension and stiffen the structure) and visual lightness. The acid-etched surface of each tread captures the light falling on it creating an interesting play of light and movement as the stair is used.