One of Paris’ most divisive buildings has been given a new lease of life, in a creative reuse project by David Chipperfield Architects Berlin that adds a graceful concrete arcade and a range of new amenities for the local community.
Built in the early 1960s, the former préfecture de la Seine is a 16-storey concrete-framed block with two nine-storey wings that looms over the north bank of the Seine. Despite having open courtyards on the north and south elevations, its scale was intimidating, dwarfing any other building in the Hausmann-era neighbourhood – after the city administration moved out in 2011, it gradually fell into disrepair and seemed destined for demolition.
But for Chipperfield partner Christophe Felger, it was an irresistible challenge: “In our view, the building had too much quality to tear down,” he says. “We liked the rigour of the stone facade and felt it was a hidden beauty which – because of all the implications of scale, because it was a bit rundown – hadn't been revealed.”
Their opportunity came in 2016, when the Réinventer Paris programme invited architects to reimagine 23 prominent sites in the French capital. Seeing the unused potential of this substantial concrete structure, the practice’s idea was to jump-start the dormant block as a new and all-encompassing slice of city, connecting the Boulevard Morland on the north side to the riverbank on the south.
In addition to a hotel, shops, restaurants, flats and offices, there would be social housing, a nursery, youth hostel, food market, art gallery and public swimming pool, and even a commercial vegetable garden on the roof. “It was not just a design competition, it was a programmatic competition,” says Felger. “It had to give something better back to the city.”
This meant that the architects had to work out how to fit so many new uses into the existing building, ensuring separate access, acoustic and spatial separation as needed. Social housing, the nursery and pool occupy one wing, and private apartments the other, with shops on the ground floor. The main tower has an art gallery and hotel reception at its base, with five floors of offices and seven floors of hotel rooms above.
As much of the original structure as possible was kept, although many areas needed reinforcement – some floors had concrete slabs just 70mm deep. The original steel windows were replaced with aluminium, the stonework cleaned and balconies added to the housing units. New vertical circulation was introduced to provide access to the different users.
At the heart of the scheme, however, lay a conundrum. In order to make the demanding programme stack up financially, the developer needed to create more than 1000m2 additional lettable space. The only possible solution was to insert new volumes into the courtyards. Chipperfield has added two extensions to the complex: on the Boulevard Morland elevation, a six-storey youth hostel runs the length of the site. Facing the river, a narrower, deeper block houses offices as well as the ground-floor food market.
The danger was that this would make the site even less open and accessible, rather than creating the public route that was integral to the original proposal. But the architects came up with a neatly Parisian fix. Both of the new volumes are elevated on a procession of 5m-high structural arches, which invite passers-by to walk beneath them into three new, smaller courtyards and through to the other side of the block, thereby linking the river and boulevard. The arcade continues through the heart of the complex, where it frames shops at the base of the original building wings. “Le Palais-Royal, le Place des Vosges – if there’s a city where arcades play an essential part, I think it’s Paris,” says Felger.
The arcade is made from reinforced concrete, cast in situ, with local aggregates and sand added to match the yellowish tone of the préfecture’s Burgundian limestone. In structural terms, the cast elements are not arches at all, but more like mushroom-head columns that unfurl from a 950mm square base into a 4.5m semi-arch at the top of the shaft. The columns are tied together by the 250mm-deep slab of the new spaces above, and stabilised by the shear walls of the buildings at either end.
Mock-ups of the columns were prepared in a warehouse outside Paris to test surface details such as edges and joints, as well as the connection to the footings. Different formwork systems were also trialled, with steel chosen as the most practical and easiest to reuse. This was coated in a textured paint to give a regular, stone-like finish to the concrete. The site architect, BRS Architectes, worked closely with contractor Bouygues to rationalise the design so that variations in the columns were kept to a minimum.
“A lot of the differences in dimensions were quite small, so we definitely looked to reduce the variations in size,” says project architect Caspar Muschalek. “The columns under the youth hostel are all the same, for example, and so are the ones in the north courtyard. Where they connect different spaces, some of them had to be adapted.” Where possible, he adds, variations were accommodated in the height and orientation of the concrete footing.
Due to the constraints of working on an existing building in a busy city centre, the casting process was tightly orchestrated. The contractor had to work in the minimum possible space, preparing and erecting the falsework and constructing the flower-like reinforcement in an area just three times that of a single arch. And deliveries of the ready-mixed concrete, from a plant 20 minutes away, had to be timed to perfection.
Accurate placement of the columns was also critical: if the footings were 2mm out, that would translate into a 4cm misalignment by the edge of the column heads. An artificial ground level was created across the slightly sloping site to ensure that the formwork was only ever moved on a precise horizontal axis.
The curved form of the arches, with the columns positioned centrally, was crucial to giving the building a more welcoming presence, says Felger. “We didn’t want columns on the building perimeter – it would have felt exclusive. With the arches, you have to step under something, and it’s more inviting. If you just bring a column vertically down, that's probably not going to intrigue people.”
Other subtle touches also lure people in. Access to the arcade is flush to the pavement, and the shops work visually as continuations of the arches, separated only by full-length plate glass. The lushness of the courtyard planting, clearly visible from the street, is another attraction: “It’s like an oasis. I think this will become one of the most important aspects of urban planning and architecture in the future because we have to create an abundance of microclimates.”
Visitors are not only drawn through the building, but also up it. The top two floors of the tower have been returned to their original use as a public restaurant and event space, with an art installation by Olafur Eliasson. On the outside terrace, a mirrored soffit merges the views of Paris with the sky. “The 16th floor is an incredible height. You're kind of above but you're not too distant from the fabric of the city. We knew this should be shared with everyone.”