The Grande Mosquée de Paris dons its retractable roof

On Friday, the architecture practice Dubois Jeanneau, working with the engineers at AIA, handed over the retractable roof of the Grande Mosquée de Paris. Measuring 29 metres long by 20 metres wide, it is designed to protect worshippers from the weather, and has the particular feature of being hidden from view once folded away.

The Grande Mosquée de Paris, completed in 1926, is listed on the supplementary inventory of Monuments Historiques. The patio lies at the centre of the building and is open to worshippers on Fridays and feast days. The historic character of the building led to consultation with the Ministère de la Culture, so that the roof would be as discreet as possible.

The Grande Mosquée de Paris dons its retractable roof – © SCP DUBOIS JEANNEAU — © SCP DUBOIS JEANNEAU

"The engineer has to approach the work with great subtlety in order to respect, as far as possible, a historic site with recognised architecture. We designed the way the roof is installed, and the way it opens and closes, to be as unobtrusive as possible, both in terms of the existing fabric and visually. As a result, only very slight alterations were made to the original building to allow the arches to fold away, and once lowered, they are almost invisible " explains Jean-Marc Marion, Complex Structures Engineer at AIA Ingénierie.

The engineers' answer is a metal and fabric structure made up of five metal arches to the north and four to the south. These arches form two half-roofs. The first arch is fitted with two motors that drive the other arches through the operation. The arches run on two rails supported by eight posts anchored in the floor slab. The system is guided by pantographs.

Once the roof is folded, the whole structure (arches and rails) is lowered by 1.80 metres on the posts that support it.

The roof is made of high-tenacity polyester fabric coated with PVC and protected by layers of finishing varnish to limit the build-up of dirt.

The roof unfolds and folds automatically. A safety device prevents the arches from being deployed when the structure is in its lowered position, and likewise makes it impossible to lower the rails while the roof is unfolded.