In the conversion of this former university library building in St Denis, cost constraints necessitated the retention of the load-bearing structure, which consists of concrete coffered floors and precast concrete columns. To improve the sound insulation, the floor construction was increased in thickness, acoustic slabs were added to the plasterboard linings and suspended soffits, and the main rooms were separated by corridors and ancillary spaces. The various elements in sheet steel and fixed glazing added to the facade serve to extend the internal space and create a bolder three-dimensional form externally. The prefabricated supporting construction was fixed to the existing structure with injection dowels. Ventilation is provided by integrated steel flaps. The steel external cladding was welded to the projecting elements on site.