Formby Helical Stair

Structural Designer

Webb Yates Engineers

Client Name

Private client


Formby, UK


The Stonemasonry Company 


RAL Architects


A breath-taking, two-storey stone staircase that springs from one landing and sweeps unsupported through 320 degrees to the next. The total weight of French Combe Brune limestone making up the stairs is approximately 6.6 tonnes.

The shape of the stair was sculpted to maximise impact by making the edges of the treads as thin as possible, while along the central spine two post-tensioned cables hold the entire stair together.

Judge's comment:

The judges were amazed by the grace and audacity of this post-tensioned stone stair that twists through space from floor to floor. The engineer has fully understood and exploited the limited tensile capacity of stone by augmenting it with just enough steel to form a wonderful hybrid.