A high-precision graft on the Philharmonie

The Philharmonie had reached the limits of its capacity. To support its development while preserving Christian de Portzamparc's original work, an extension was designed in continuity with the existing building. Far from a showy enlargement, it fades behind the original architecture, echoing its curves, its lightness and its architectural language.

Located on the Place de l'Europe side, the extension will house, over two levels, a multipurpose hall dedicated to educational and cultural activities, a restaurant opening onto the square and a larger cafeteria for artists and staff. Proof of the care taken to ensure architectural continuity: a full-scale prototype of the façades — a "mock-up" — was submitted to Christian de Portzamparc in person. "At 82, he travelled from Paris himself to approve it," says François-Paul Gioria, site manager at Félix Giorgetti.

The first of these is that the Philharmonie is not closing its doors. Concerts, events and activities continue throughout the works. Access for the public and for emergency services must be maintained at all times, requiring meticulous organisation. Set up on the Place de l'Europe, the site also has very little space for facilities or material storage. Added to this is an invisible but decisive constraint: the extension is being built directly above the Trois Glands car park. "Because of the weight, installing a tower crane would have involved too many constraints. Instead, we are using lighter mobile cranes," explains our site manager.

A surgical operation

Graft. That is the term our teams use to describe the extension and the precision it requires. "It's like a graft on every level. It has to feel as if it had always been there," sums up François-Paul Gioria. The operation is at once structural, technical and architectural: the new spaces must connect to the existing building without any visual or functional break. The works began with excavation down to a depth of nine metres, followed by a load-distribution slab — a concrete platform that spreads the weight of the extension above the car park — before the new foundations were laid. The iconic granite slabs of the Place de l'Europe were removed, cleaned and stored so they can be reinstalled once the works are complete.

There are 250 of them, but they are slimmer and filled with concrete to limit their weight while guaranteeing their strength. The steel framework, designed in an elliptical shape, precisely follows the geometry of the extension and incorporates all the roofing layers. Nearly 1,500 m² of roofing will be built, along with a fully glazed 500 m² façade and vast glass balustrades. The project also includes a major restructuring of the existing spaces. Due to the lack of room, some operations were carried out almost by hand. "Because of the tight space, 40 tonnes of steel beams were brought in 'the old-fashioned way', using chain hoists and trolleys. The walls were built with solid bricks to preserve the building's acoustics," illustrates our site manager.

This project illustrates the full complexity of working on an iconic building that remains in operation. A precision operation where every detail counts, with a single goal: to deliver, in July 2027, an extension that will seem to have always been part of the Philharmonie.