Endless Stair, a towering structure of 15 Escher-like interlocking staircases made from American tulipwood cross-laminated timber, has won a Judges’ Special Award at the Wood Awards 2014.
The Endless Stair was a project commissioned by the American Hardwood Export Council (AHEC) during the London Design Festival in 2013 and was showcased to the public in front of the iconic Tate Modern gallery in London. The stairs were reconfigured and also shown at Interni’s ‘Feeding New Ideas for the City’ exhibition during the FuoriSalone in Milan, Italy in 2014.
Designed by de Rijke Marsh Morgan Architects (dRMM) and engineered by Arup, Endless Stair was both a sculpture and research project advancing the knowledge of timber technology and sustainability.
The judges said:
“The Endless Stair was a real one-off, a project that combined being an exciting and accessible piece of public art with research into innovative new ways of using a material, adding to the sum of knowledge as well as providing delight.”
David Venables, European Director of AHEC, said:
“I know how competitive and rigorous these awards are, so for this group of highly experienced judges to give a special award to the Endless Stair is fantastic news. This project was very innovative and experimental and was the first-ever use of hardwood cross-laminated timber (CLT). The environmental profiling we undertook was also unique. So to get the recognition for the contribution we have all made to the debate on timber in construction is very important.”
Faced with the challenge from the American Hardwood Export Council to produce a sculptural installation using slender tulipwood CLT panels, Alex de Rijke of dRMM quickly settled on an idea involving stairs:
“On stairs people interact, they pass each other, they are always interesting places with spatial and social potential. We thought a staircase would be a good vehicle for exploring structure, space and making a sculpture. Stairs are sculpture’s gift to architecture.”
Built by Imola Legno and Nüssli, Endless Stair was made up of a series of timber flights, some veering to the right some to the left, providing many ways to explore the installation, which ultimately led to the top flight that acted as a dramatic viewing platform. Endless Stair pioneered the use of hardwood for cross-laminated timber (CLT). Cross- laminated timber is typically made from softwood, yet this project demonstrated the real potential for using tulipwood, an abundant, relatively inexpensive and structurally impressive American hardwood.
A key objective for dRMM was to make the elements as environmentally friendly as possible, with each flight of stairs built from standard elements creating as little waste as possible in construction, and with the ability to re-use and relocate the design either in part, or as a whole. These laudable aspirations are backed up by hard figures, utilising AHEC’s ISO- conformant life-cycle assessment (LCA) prepared by PE International, leaders in the field of LCA.
Cross-laminated timber (CLT) is an engineered timber product that is increasingly used to build the walls and floors of buildings. CLT is of a ‘sandwich’ construction, normally with an odd number of layers. On each successive layer the fibres of the timbers run in opposing perpendicular directions, so that if you could look through the CLT from above you would see a grid of fibres. It is orthotropic – that is, it has different properties in three directions. This is important because timber is strong along the directions of the fibres, and less so in the cross direction. Building up this structure results in a panel that has equal strength in all directions. It also gives it dimensional stability. Modern offsite manufacturing methods mean that CLT panels can be made in a factory and then delivered to site for assembly in a fast and accurate manner, cutting down on the time needed for construction.