The architectural concept is a response to what seemed, at first, an almost insoluble design problem: in 2014, more than a year after planning had started, legislation for the preservation of historic buildings in the Marais district of Paris was tightened to such an extent that changes to the building fabric became practically impossible. The glazed steel tower is, therefore, conceptually a pure addition that leaves the existing structure more or less untouched.
The mechanical construction, consisting of two large and two small platforms set above each other, not only creates additional exhibition areas. It allows a three-dimensional exploitation of the entire volume of the courtyard. In 49 different combinations, the four platforms link up with the surrounding galleries or enter into a relationship with each other. An important argument in negotiations with the authority for the preservation of historic buildings was that all levels could be lowered directly on top of each other to the ground level of the courtyard. In other words, the platforms disappear, and the courtyard is left empty as it was before the conversion.
The floor elements, adjustable in height, required a solution for a simple, secure assembly and removal of a safety system against falling at the edges of the galleries and platforms. No regulations existed for the operation of movable platforms bearing people in public buildings. The architects, therefore, developed a system of balustrade modules, consisting of metal gratings that can be inserted in the edges of the floors. When these are fastened in position, a magnetic lock establishes an electrical contact, so that the safety of all balustrades can be controlled by a central alarm system. On removing a balustrade, a flush cover strip closes the recess in the floor. Almost all balustrade elements are identical, with a length of 9.10 m, and can be installed at any point in the structure.
The steel tower, which rises well above the two flanking side wings of the building, is nevertheless not visible from the street. The courtyard is accessible from two sides - via the main entrance and via a rear passage that extends across the entire block. To achieve a maximum spatial effect in this small space, the panes of glass to the tower are up to 6.70 m high and 2.40 m wide without intermediate posts. Rainwater from the gently folded glazed roof flows along gutters and down the four steel corner columns of the tower. At their lower edge, the panes of glass bear on the cornice of the existing building and link up with the rainwater gutter, which drains the existing roof, too. This is the only point where old and new are constructionally united.BF
