Archiplein and Perraudin Architectes build a major project in solid stone in a Geneva suburb

Solid stone construction by Archiplein and Perraudin Architectes.

The aim was to reduce the ecological footprint of the buildings and ensure earthquake safety

Solid construction with natural stone is making waves: since 2021, there has also been a major project in Switzerland in which the walls are built from load-bearing natural stone blocks. There are two buildings in the Geneva suburb of Plan-les-Outtes: each has one section with four floors and one with six floors, and they house a total of 68 apartments. Around 70 % of these are social housing and 30 % condominiums, which shows that solid construction with stone is also possible under particular cost pressure.

The two buildings were planned by the architecture firm Archiplein in collaboration with the French architect Gilles Perraudin. Perraudin is now regarded beyond France as an old master of solid stone construction.

This new scale also required answers to some new questions:
* Which quarries could supply the impressive quantity of around 2070 m³ of stone material?
* Which ones would also have the capacity to cut the 6975 stone elements (rectangular blocks, almost 1200 cornices and 690 slabs)?
* how would the surfaces of the blocks be finished, as many of them bore the marks of the saw or scratches from the factory?

We want to answer the last question straight away: the stone blocks were left rough as they were, thus creating a certain decor for the façade: the position of the sun casts a shadow play over the stones surfaces.

The cornices for draining the rainwater give the façade an additional structure, beyond the grid of the stone blocks.

Solid stone construction by Archiplein and Perraudin Architectes.Solid stone construction by Archiplein and Perraudin Architectes.

Such buildings are erected according to the modular principle: a repertoire of stone elements with specific sizes is defined in the plans, and they are cut precisely by CNC machines at the quarry or in the factory.

Solid stone construction by Archiplein and Perraudin Architectes.Solid stone construction by Archiplein and Perraudin Architectes.

The dimensions here were between 2 m and 1 m long, 70 cm high and 50 cm thick. As the height increased, the bricks could become thinner because they had less load to carry.

Solid stone construction by Archiplein and Perraudin Architectes.

Laying out the walls was easy: “The blocks were lifted by a crane operator with a lifting clamp and received by two masons who adjusted its precise positioning. The masons had to get used to handling structural elements which would also make up the finishing layer, without any plastering, and which required special care”, as said in a description by the architects.

The walls are considered earthquake-proof, which is important for the area around Geneva.

Solid stone construction by Archiplein and Perraudin Architectes.

What is particularly interesting from an architect’s point of view is that this modular construction offers a wide range of design options. Here, for example, the planners have played with the outer corners in the façade: they are designed negatively, as a variant of the Miesian corner by Mies van der Rohe.

The negative corners also appear on the inside.

Solid stone construction by Archiplein and Perraudin Architectes.

There, wood is the defining material. Its brown tone matches the cream tone of this limestone. Concrete was only used for the staircase in the core of the buildings.

Solid stone construction by Archiplein and Perraudin Architectes.

As far as the construction is concerned, the architects speak of three wreaths (in the French description: “Trois Couronnes“): on the very inside is the stairwell area, surrounded by the functional rooms, and on the very outside are the living spaces, following the same principle.

The windows reach down to the floor. This makes the rooms bright and allows a wide view of the Jura mountains and across the Salève river. 

<a href=Solid stone construction by Archiplein and Perraudin Architectes.

Cornices running around the outside emphasize the floors, whose ceilings are made of concrete.

Three types of limestone were used, depending on the intended use: the hard Pierre de Migné for the base and the softer Pierre de Brétigny and Pierre d’Estaillade above.

The banal realization that not all stone is the same was heeded here. Marlène Leroux, architect at Archiplein, puts it a little differently in a video: “You’re dealing with a natural material and you have to say goodbye to the idea that everything will always be the same as before.“

The exterior walls do not require thermal insulation. The thermal inertia of the stone keeps the heat peaks outside in summer and the heat inside in winter.

There is no plaster on the load-bearing walls. This also means that the residents can see from the inside and outside what kind of material is around them.

Solid stone construction by Archiplein and Perraudin Architectes.

According to an interview in the magazine Espazium, the architects had to do a lot of convincing for their concept. “An important part of the work was to reassure everyone involved,“ say Francis Jacquier and Marlène Leroux from Archiplein.

In the end, however, they were surprised that, although there were very heterogeneous opinions on the jury, a consensus emerged, “albeit with very different reasons“: Some particularly liked the urban expression of the stone, others appreciated the real sustainability in the project, others liked the construction with the three wreaths. “Everyone found something that suited them. “

Planning is currently underway for an even larger project in solid stone construction in Geneva, where a former chocolate factory from the 19th century is being extended in the Coulouvrenière district.

Atelier Archiplein, Geneva

Atelier Perraudin, Lyon

Espazium (French)

The stone came from companies France Pierre and Carrières de Provence.

Photos: Adrien Buchet, 11h45: photographie d’architecture
 

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(19.02.2024, USA: 02.19.2024)