This lightweight and delicate concrete staircase at Somerset House in London is a modern, elegant and ethereal intervention within the existing historic listed building. The stair comprises distinct elements: the central cylinder is a filigree and reflective network which supports the minimally sculpted treads, with a glass balustrade tying the whole assembly together. The cantilevered pre-cast stair treads are in ultra-high-performance concrete (the first such application of this material) and the design expertly exploits the material's strength and dimensional stability to produce a stair of refined size, which is a complicated yet economic assembly.
The judges were impressed by the innovative use of materials and structural form to generate this dynamic and dramatic spiral staircase. The delicate filigree mesh of the central cylinder belies its ability to support the 4 storey height stair, and the refined detailing of the ultra-high strength precast stair treads and glass balustrade are a testament to the engineer's art.