l330 Kensington Church Street A modern intervention to a 1920s existing building has been completed recently in west London. The 'front' bays of the structure were kept and refurbished to avoid the need for a facade retention system, with a new exposed structure introduced in parts to rationalise circulation and increase usable space. Structural glass lift cores, stairs and bridges allow light to penetrate deep into the spaces. To enhance this effect a 'four-point'supported glass tread is used with 19mm toughened/19mm float glass. Destructive testing of treads was undertaken as no design data is readily available on this type of support of glass. Deflection and vibrations of the stairs as a whole, a commonly misunderstood criteria, had to be carefully examined to seek the acceptable 'bounce'!