Renovation and atypical elevation, the new higher education building based on a nursery on the Beaugrenelle slab in Paris symbolizes the beauty of the new architecture of the climate and its isolation.
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50 years ago, the very Corbusian Beaugrenelle operation started with a complex designed by Grégoire and Choquart including a residential tower of almost 100 m, a swimming pool, offices, parking lots, a cafeteria and a nursery, in concrete and on a concrete slab which should lead to a shopping center. In addition to the massive concrete structure of the nursery, which is cantilevered and which frees the facades, these construction elements incorporate asbestos.
The nursery moved in 2021, the cleaning made it possible to recover a structure capable of accommodating an elevation, with clear facades. L’Nunc agencywhich had just completed the large housing complex with MOB facade on rue René Clair (18th) in Paris, decided to push away from the cursors which now seem obvious to us.
Some resemblance to the renovation, but the initial facade had aged well. © 11:45 a.m.
An almost passive project
The concrete structure blends into a whole whose facade gives a limpid expression which makes you forget theheavy renovation operation. The facade designed at the time in larch breaks its regularity with a monochrome effect which will nevertheless evolve over time. Behind, straw boxes with front side one Siniat Weather Defense plate protectionvery dispersive and therefore perfectly suited to biosourced insulation like straw.
On the interior side, the vapor barrier is masked by Wienerberger raw earth bricks, undoubtedly intervened in appeal after the cessation of Cycle Terre in Sevran, and which offers bricks stabilized in the lower part and not stabilized in the upper part. Thus, the depth of the bays acquires a noble character and the bricks provide inertia. THE bales of straw bring the project closer to the de facto passive level, and the intervention of BE Solares Bauen seems to testify to an original intention which was not carried out.
A very practical working base for straw bales. © Luc Boegly
Consistent biosourced facade
The carpenter Méha de Valenton (the numerically controlled cutting machine closest to the zero point of Notre-Dame) uses a global facade solution that Piveteaubois, in the presentation made on the Share is More site, claims as an example of its global proposals for bio-sourced walls. Guardrails are part of reused materials for reusethe objective being to reuse everything possible, and has not been contaminated by asbestos.
Once again, the Nunc agency offers, despite this reuse, a timeless facade which seems to have been designed as such. It is not only a question of reusing to limit carbon emissions, but also of strengthening the link between the project and all architectural context of the Keller slab.
The image that says it all, the structure, the exterior protection of the straw, the cladding, the alignment. © Luc Boegly
Exemplary work
The roof seems to rest on thin posts which delimit deep balcony terraces of the raised level and extend into the spine of the facade for a perfect and fluid load descent. However, the roof greeningwhich complements that planned for the entire Keller slabis facilitated by the pre-existing concrete structure (circulations). The large deflectors are forgotten by the depth of the last level and the facade should benefit from this double protection, knowing that the cladding is itself placed back from the spines. The rigor of the project and its reuse elements fit well with the initial architectural approach of the slab, even with its attempts at modernization under Valode and Pistre. After 50 years, we gradually arrive at something that makes sense. And this project becomes a must of the teaching of wood construction.
An auspicious renovation-extension
THE Keller pavilion has a lot of class and it has already been the subject of numerous visits, notably in September 2025 as part of the Happy Frugality Meetings, or visits by FiBois IDF and the late CNDB. For La Poste Immobilier, which has developed the space under the slab for its own services, the transformation of the crèche to accommodate an extension of a higher education school already present on the slab is a start with regard to thewooden real estate. Starting with a work of this beauty foreshadows other projects from this powerful client, even if, despite delivery delays, there is nothing in progress at the moment.
A Keller slab for 2050
The delays are due, among other things, to asbestos removal as well as to the difficulty of carrying out the work at the heart of a slab which does not support lifting equipment like those that the carpenter Méha is used to using. It’s not Grégoire’s fault, but the concept that prevailed almost everywhere at the time, with a raised slab for pedestrians when it was inconceivable that the Parisian street would be confiscated to cars like today, and where no one calculated the emissive weight of this type of structure. But now that they are here, the worst thing is to “recycle” it after crushing it to make more roads. There Keller slab seems set to meet the challenges of the climate catastrophe without adding to it.
Jonas Tophoven / © Luc Boegly
