A courtyard between two listed buildings was to be covered with a transparent all-glass roof and used as a foyer. The roof was not to cost more than a good-quality steel structure with a glass covering. A gently sloping construction was spanned across the almost square space at a height of about 15m. The load-bearing structure comprises a grid of beams. The five compound primary beams are roughly 14 m long and consist of offset parallel glass fins, the zigzag, splayed form of which is based on an approximation of the moment curve and on available glass sizes. In comparison to an arched form, these elements could be manufactured without laser cutting, and there is also less waste through offcuts.