In the base section (ground floor to third floor), used for storage and archives, the in-situ-concrete facade is placed in front as a second shell. The seamless reinforced-concrete facade warps horizontally and vertically as a result of shrinkage and temperature fluctuation. The complex differential movements between the different building sections require the facade to be almost completely decoupled from the building shell by means of plain bearings and (where possible in terms of static loading) individual fixed points.

The transition from the grid to the outer base shell was a tough nut to crack with regard to static loading. Inclined struts transfer the grid’s weight into the base, and horizontal pressure and tension components arise at the foot and head of each strut. At the same time, the struts’ upper and lower ends must be supported in such a way that they can be moved horizontally, vertically and sometimes outside the plane. The balcony slab above the struts, together with the parapet, forms a ring around the building, which deflects forces such that, at all horizontal support points at this height, only compressive forces are transferred to the building shell’s slabs. Here, this is the only possible way to realise the seamless exposed-concrete design.