Unique wave-like geometry of the roof
The exceptional architecture of the Zentrum Paul Klee is characterised by the steelwork of the roof-bearing structure. The wave-like geometry of the roof, which rises gently from rear to front elevations, is so unique that each individual metre of the 4.2 kilometres of steel girders has a different shape.

The building’s idiosyncratic geometry is such that a section of the steel arches is slightly inclined but always at differing angles. The arches are braced by compression struts directly integrated into the roof structure to prevent the arches from tilting backwards. Likewise the extremities of the steel arches are stressed together with the aid of tiebacks and connected with the floors and the floor slabs to prevent the steel arches from slipping apart at their base. Each of the curved, variable-height steel girders has been constructed individually.

40 kilometres of seams welded by hand
The individual sections were first cut out of large metal plates using a computer-controlled autogenous cutting machine, then formed into their definitive shape and finally welded together. The strong curvature of the steel girders prevented them from being welded by machine, which meant that more than 40 kilometres of seams had to be welded by hand.

After a thorough review of alternative materials such as aluminium, copper and titanium it was decided to use special steel for the roof plate. Ecological, financial and technical criteria were decisive.

The roof-bearing structure together with its foundations and the façade were computer-simulated as a large 3D model and analysed at great length by experts.