The Materials Behind This Ethereal Floating Glass Stair + Skylight
Overlooking the side of Hong Kong Island, this stand-alone glass staircase and skylight within a two-floor apartment appears to float between the walls of the apartment. Designed by Carpenter Lowings Architecture & Design, the installation, which has an overall height of 5.5 metres, creates an ethereal effect while maximizing light into the apartment and acting as a unifying architectural element. Beautiful indeed. So how did they do it?
According to the architects, the stair is formed entirely from heat-strengthened laminated glass, with titanium fittings bonded into the glass during the fabrication process. Each stair tread comprises three sheets of glass supported by three fittings. The silhouetting of opaque elements is avoided by minimising the number of metal fittings used. As a result, the design achieves the maximum interaction of light and glass.
All components were manufactured off site – the staircase in Germany (with titanium fittings from the USA), and the skylight in the UK – and assembled on site by the Carpenter Lowings team in four stages to coordinate with the rest of the building work over a period of more than a year, as part of a design & build contract. The glass fittings have to be made from titanium because the expansion and
contraction of the metal when heated in the laminating process closely matches that of the glass itself, thus reducing the risk of cracking.
The glass for the stair structure was laboratory-tested to comply with the Hong Kong building regulations, and calculations were required to prove that the building frame could sustain the loads despite the stair’s apparent weightlessness.
The space between the highly-finished glass elements of the stair and the crude concrete and steel base building structure uses complex adjustable brackets which are sensitively hidden from view behind the wall finishes, the latter completed after the stair was installed.
Meanwhile the skylight – measuring 4.4 metres by 1.5 metres and opening onto a roof terrace above – provides an unobstructed view of the sky from within. When in a closed position, the skylight frame is invisible from the apartment below, creating a view of the sky which appears to double in width when seen reflected in two large structural glass screens partially enclosing the staircase. These screens incorporate a vertical reflective pattern – printed inside the glass – which evokes the depth of light created by falling rain.
Luke Lowings, of Carpenter Lowings Architecture & Design says: “This staircase acts as a discrete and subtle sculptural element in its own right. It is both aesthetic – providing a strong visual focus for residents and visitors – and practical – modulating daylight to reduce the harsh glare and intense heat of the Hong Kong climate. The design demonstrates how significant amounts of natural light can be brought into small, relatively compact spaces and transform them into bright, welcoming areas. The staircase’s apparent weightlessness also helps to create the impression of a floating, ethereal structure rather than one which dominates the living areas. The light of the sky is reflected from the structural glass panels, through the clear treads of the stair itself deep into the lower floor.”
The design was recognised with a Special Mention in the 2016 Architizer A+ Awards: ‘Details: Architecture + Glass’ category.