A structure of copperclad curved steel ribs
The café structure takes the form of a series of eight steel 'ribs' that curve - each tilted in relation to its neighbour - to create the enclosure. The curve continues below the floor and emerges as a low wall that acts as the servery; the continuity maintains the structural integrity of the shape.
The construction involved two individual curved ribs of 15mm steel plate, laser-cut and welded between a series of diagonal CHS struts. The resulting frames were taken to site and the ribs of adjacent curved frames were bolted together into pairs, some reinforced with an additional 15mm plate rib.
On the outside, the rib structure is clad with 0.7mmthick post-patinated copper sheet with standing seams, laid on to a bitumen 'sandwich' waterproof membrane and a ply deck, with 20mm highperformance foil-lattice insulation. The internal finish - panels of lacquered bronze sheet on a vapour-control layer - is also laid on a ply deck; both ply decks are curved to follow the rib profile.
The ribs of the structure project beyond the bronze panels and taper at the upper edge to a delicate bull-nose; this incorporates a notch in which the glass panels are restrained.
The 12mm toughened lowiron glass panels are fixed with Planar stainless steel bolts to toughened glass fins. They are supported from below and only restrained at roof level; that is, the roof is not supported on the glass.
The existing reinforcedconcrete terrace structure was adapted to support the weight of the new building and to provide some extra terrace space around it. A new pit incorporating a concrete beam spans between points of support to provide the main foundation.