As an integral part of the urban block forming the site of the Ecole Normale Supérieure, the extension project is located in a courtyard to the rear of the entrance and the main buildings. This rear courtyard is a platform overhanging one of the three streets running around the university. Thanks to this highly particular urban layout, the new building reveals itself either as a roof terrace pavilion on the courtyard side or as an eight storey building giving onto the street. Consequently, the extension is placed in an intermediate situation, between two levels and between two elevations, much like a passage built between the upper level of the school and the lower level of the street, between the neo-classical elevations giving onto the courtyard and the buildings on the other side of Rue Rataud, between the private space of the school and the public space of the street. The new project triggers a physical and visual relationship by and through the void that it fills. It generates a unique architectural and urban space that, rather than seeking insertion or integration, develops urban interference and intrusion. This type of incursion simultaneously allows the project, as an autonomous contemporary object, to fairly brutally reveal the breaks and discordances of the concerned urban setting while also being its indispensable mediator.
The building has 8 storeys on the street side and 6 on the courtyard and school main entrance side. It is the superimposition of different surface strata, whose reference level is that of the courtyard. Further back and narrower, the three upper storeys house rooms. The courtyard level is the same as the cross-concourse, which is as transparent as possible, the light calling you into the arts library above, and the sciences and maths libraries below. Both of these are on a double level, with a mezzanine.
Through this horizontal stratification, it is a question of finding vertical dimensions, in order to give air to the dense shelving used for storage and also consultation and to make the distribution clearer. These verticals are deployed along the glass façades, on the street at the lower levels and on the top double level.
The building would appear to be clothed in a thick cloak of light, which blurs the edges and contributes to distorting and softening the perception of its scale. This guiding line is highlighted by a screen made of high vertical strips made of polished stainless steel sheets sandwiched between two glass sheets, with neither frame nor rim. These “shutters” (220 cm x 90 cm) can be swivelled and are fixed to the façade by moulded cast aluminium clips. They filter or provide more natural light. Few materials are used, these being crude concrete, zinc- plated aluminium sheet facing and false ceilings, aluminium sheet guardrails, plum carpeting. The books can now be consulted day and night by the boarders and researchers in this reading wing of the Rue d’Ulm.