acme installs massive timber staircase with winding mirrors in its london studio

london-based acme studio has completed a staircase prototype combining modern methods of construction with an adaptive design approach, created to work with minimum intervention within any building. the massive timber staircase was designed in 48 weeks, manufactured in four weeks and constructed in just five days, and has been installed in the architects’ own office, leading from the ground to the first floor.

all images © ed reeve

since the existing building had no usable stair between floors, a hole was first cut into the first floor slab to create a connecting void. it became clear during demolition that the existing first floor concrete slabs had no further load capacity, necessitating a new approach to the stair design. rather than relying on connections of the stair at its top and bottom, it is designed as a free-standing cantilever, with no connection to the floor above. in order to reduce its carbon footprint and to provide enough counterweight for the cantilever, acme‘s staircase is made from layers of cross-laminated timber, CNC cut in switzerland, where each of the 20 steps is made from six timber elements.

once the interlocking pieces for one step are assembled, they are simply fixed with screws to the step below. it was designed to be self-supporting during assembly to ensure that it can be built without scaffolding or temporary works, and all elements were designed to be light enough to be assembled directly by the designers. the bifurcating twin spiral form of the staircase serves a number of functions. the shape creates its own structural integrity, the bifurcation allows people to make destination choices on the stair, the widening of the stair provided a place to stop and converse, and the inward rake of the upper steps provides stability and functions as a handrail.

in order to economize, the shape and the resulting timber cutting list was carefully optimized to achieve minimum cutting wastage. influenced by coco chanel’s mirror stair on 31 rue cambon in paris enabling anyone perched at the top to observe the comings and goings on all levels of her atelier, two sides of the stair have been clad in mirrors to ensure the link is a visual as well as physical link.

‘the stair is a prototype to show how very humble elements of solid timber, simply fixed together, can form an interesting sculptural solution to the everyday task of going up and down, and solve a complex structural problem with an intelligently engineered solutions and an interesting use of timber technology,’ explains friedrich ludewig, acme director. ‘simple structures can be simultaneously beautiful, economical and practical, and help to create inspiring spaces in which to live and work.’

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edited by: lynn chaya | designboom