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How SOS put a glass and mirror roof over AKG Art Museum, Buffalo

Studio Other Spaces’ sculptural dome enclosing the New York museum’s courtyard creates a reflected kaleidoscope of scudding clouds to animate visitors beneath

Common Sky’s faceted mirrored inner surface creates kaleidoscopic visual effects for the museum’s visitors.
Common Sky’s faceted mirrored inner surface creates kaleidoscopic visual effects for the museum’s visitors. Credit: Marco Cappelletti

Common Sky is a canopy of glass and mirrors enclosing the internal courtyard at the Gordon Bunshaft-designed AKG Art Museum in Buffalo, New York, to create a new space for public events.

Designed by Studio Other Spaces and inspired by the city’s intense weather, the canopy is designed to work both as a site-specific sculpture and a fully functioning roof. ‘We went for a clearly sculptural language because we wanted something distinct from museum’s modernistic design that, at the same time, offered a maximum experience of being exposed to the outside,’ says Sebastian Behmann, architect and SOS co-founder with artist Olafur Eliasson.

At its perimeter, the canopy’s steel structure rests lightly on new beams carefully concealed in the roof of the listed 1960s museum. Its domed skin of tessellated glass triangles curves gently upwards before plunging steeply ground-wards at a single, off-centre funnel-shaped column, positioned asymmetrically within the space at the precise point in the courtyard where its only tree once stood.

The clever double skin structure allows the structure to have a very low arch.
The clever double skin structure allows the structure to have a very low arch. Credit: Marco Cappelletti

The funnel’s tapering diagrid verticals of interconnected steel members, like an angled, hollow tree-trunk supporting the canopy’s steel branches, minimise the additional load imposed by the canopy on the existing structure. Says Behmann: ‘up to 50%’ of the load is carried by the funnel, with the remainder distributed equally around the edge of the roof. ‘It was a nice coincidence that the one major load-bearing point also allows rain and snow to enter the space at the funnel to be a part of the structure,’ he adds.

On the canopy’s underside, a tubular steel second structural layer adds strength and rigidity. Designed by structural engineer Herwig Bretis, MD of Art Engineering, this double layer allows the dome to have a flatter, less intrusive profile – and can support a design snow load of 1000kg/m² from the 5m deep drifts common in the lakeside city.

SOS has interspersed the inner structural layer with myriad mirrored triangular panels to create a fragmented, reflected kaleidoscope of scudding clouds for visitors in the courtyard below.

Bringing steel structural nodes together as hexagons avoids unsightly weld concentrations.
Bringing steel structural nodes together as hexagons avoids unsightly weld concentrations. Credit: Marco Cappelletti

The roof’s slender steel members are welded together in what Behmann calls ‘hexagonal decentralised nodes’. It is a clever solution: normally with a triangular grid structure all six steels meet at a single node which he says makes it difficult to weld. But here only two members meet at any one point on the hexagon, greatly simplifying the canopy’s construction – and welcome no doubt to German fabricator Hahner Technik.

Behmann says early involvement of  the structural engineer and fabricator was key to a design that was feasible from both a construction and cost perspective. ‘The structure becomes affordable because you take out all the risk,’ he says,  while tendering it would hit the price because ‘they would say it is too complex’.

The canopy was built in Germany, cut into sections and shipped in standard containers. ‘Transportation was part of the design process because you can only cut the structure in certain areas, which must be defined early in the design,’ explains Behmann. Flanges were welded to the cut steels to be bolted together when the structure was reassembled. Then the cut steels were welded back together and flanges removed. ‘Only a few welds were needed on the construction side, but not too many,’ he says. 

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