
Attached to the Petite Ceinture, the old railway line surrounding Paris, the building of the social landlord Habitat Social Français, a subsidiary of the real estate agency of the City of Paris, has completely changed its appearance: gone is the mustard plaster and blue ceramic tiles around the windows, replaced by an off-white façade topped with two new floors covered with anthracite gray cladding.
From the outside, you might think that this building in the 20th arrondissement has always been five stories high, but until last year it was only three.
Sixteen apartments ranging from studios to three-room apartments were built on the roof, at the same time as thermal insulation work was carried out on the facade of the building dating from 1980. All for a total of 5,7 million euros.
In its local urban planning scheme, which will be put to the vote on Wednesday, Paris City Hall has set itself the objective of creating 1.000 homes per year by raising the height of existing buildings.
The main advantage of these elevations: they do not use undeveloped land, which is useful as green spaces to limit heat islands. The challenge is significant for the city of Paris, where finding accommodation is a headache for tenants, in addition to being very expensive.
The new apartments were built with a wooden frame - a detail that is not insignificant for the sense of smell - and according to the criteria of the "high environmental quality" certification.
Calvary and water damage
"We always use wood for elevations because it is light," explains Alexis Joly, president of the company SNERCT Construction, which carried out the work. He also puts forward an ecological argument for the City of Paris, which wants to use bio-sourced materials as much as possible.
Even with a lightweight material, the operation remains complex: "the walls were not strong enough to support the weight of two additional floors, so we reinforced all the basement beams with carbon plates and rods," explains Valentin Mention, architect at the Atelier Choiseul firm.
In other cases, "sometimes it is necessary to reinforce the foundations," which involves "breaking the slab" of concrete at the base of the building, he continues.
A resident of the residence for forty years, Sana "was scared when the work began, our walls were vibrating and moving," she says.
More frightened than in favour of the idea of adding floors to a building that has already been built, she concedes that "we are short of housing" and so much the better if "people will benefit from it".
As for the work, "frankly it was an ordeal," says the resident, who suffered water damage, like all her neighbors.
To build on the roof, it was necessary to strip it bare and remove all the layers of insulation, which encouraged water infiltration, in the middle of the rainy winter of 2023-24.
"We offered to rehouse the tenants on the top floor, we provided noise-canceling headphones, we agreed to repair the damage and we were present throughout the work to listen to the residents," explains Marie-Camille Auger, director of project management at HSF.
The 60% reduction in the energy consumption of apartments, made possible by the insulation of the building, helps to make the pill easier to swallow.
The technical complexity of such work, the management of residents and the high cost are putting off many builders and landlords for the moment.
The deputy mayor of Paris responsible for housing, Jacques Baudrier, points out that adding floors is less profitable outside Paris, where land prices are lower and plots of land are less scarce.
After ten years of experience in elevations within the HSF social housing stock, the solution "has proven itself" for Jacques Baudrier. Now he would like to bring on board the co-ownerships that are carrying out energy renovation work, via the CoachCopro support platform. The elevations will take off "in three or four years", he hopes.
Illustrative image of the article via Depositphotos.com.