While most projects involve gable roofs or roof terraces, others offer unusual shapes. This is the case for the Great Nave of Saint-Ouen, in Seine-Saint-Denis, which has regained all its originality since its renovation in 2024.

On the banks of the Seine, between Saint-Ouen and L’Île-Saint-Denis, stands an iconic silhouette of 20th-century architectural heritage: the Great Nave of the Île des Vannes sports complex. Designed in the early 1970s by architects Anatole Kopp, Lucien Metrich, and Pierre Chazanoff, this technical feat—and particularly its vast, suspended, hyperbolic paraboloid roof—symbolized modernity and bold construction. Fifty years later, the aging structure has been restored to its former glory following a renovation initiated in preparation for the Paris 2024 Olympic and Paralympic Games. Closed since 2014 for failing to meet accessibility and energy efficiency standards, the building nevertheless enjoyed strong local attachment. The renovation project, managed by Solideo (the Olympic Works Delivery Company) and entrusted to the Chatillon Architectes agency, aimed to breathe new life into this monumental nave while respecting its original character. The objective was to transform it into an Olympic training space before returning it to the community as a local sports and cultural facility.

A Preserved Technical and Architectural Heritage

Classified as a 20th-Century Heritage Site by the French Ministry of Culture, the Great Nave is distinguished by its suspended roof, stretched between steel cables and creating curved lines. This exceptional configuration demanded a waterproofing solution that was flexible, lightweight, and durable. It was in this context that the choice fell on the Rhenofol CV synthetic membrane developed by FDT, a subsidiary of the Holcim Group. A recognized specialist in waterproofing membranes, FDT joined the Holcim portfolio of solutions in 2023 alongside the Elevate brand, within the Building Envelope division. This synergy now allows the group to offer all single-ply technologies on the market – EPDM, TPO, PVC, and PIB – and to support the most demanding projects, whether contemporary or heritage.

Balas, the company awarded the roofing contract, installed 2,800 m² of white Rhenofol CV membrane. Its lightness – 1.5 kg/m² – was a decisive advantage: the suspended roof could only accommodate a limited number of workers simultaneously, and any excess weight risked compromising the overall structural balance. “The complexity of the project stemmed from the building’s unusual architecture,” recalls Novin Beerunj, group leader for the Paris-region-based company. “This immense hall, 98 m long and 51 m wide, had steep slopes and heights reaching 26 m. All of this on a roof suspended by cables! To comply with the permissible weight, a maximum of five roofers could work on the roof at any one time.”

High-Flying Execution

The work, carried out between January 2022 and June 2024, required meticulous preparation. The existing system – 40 mm insulation on a coated fabric – was first removed. The original steel deck, retained after inspection, was then fitted with new 10 cm rock wool insulation, laid in two cross-layered sections to minimize thermal bridging. Finally, the synthetic membrane was unrolled and heat-welded, ensuring a perfectly continuous seal. Working on such a unique surface was a remarkable feat: the teams operated in exceptional conditions, sometimes on the side of a curve, secured to longitudinal and transverse lifelines specially designed for the operation.

Comprehensive and Respectful Restoration

In addition to the complete replacement of the roof, the renovation included the restoration of the original concrete and the installation of a double skin of translucent polycarbonate on the side facades to regulate natural light. This system, combined with the new watertight envelope, reduces energy needs while restoring the building's original transparency. The membrane's brilliant white color, chosen to recreate the roof's original appearance, gives the Great Nave back its former allure: that of an inverted, light, and poetic shell, floating above the Seine. Balas has delivered an exemplary project where technical expertise serves architectural preservation.

A lightweight, high-performance membrane for complex roofs

The Rhenofol CV waterproofing membrane from FDT (Holcim Group) stands out for its flexibility and lightness (1.5 kg/m² at 1.2 mm thickness). Ideal for roofs with complex geometries, it can be used for new construction and renovation projects with mechanical fixing to load-bearing elements made of masonry, corrugated steel sheets, wood, or wood-based panels conforming to NF DTU 20.12, DTU series 43, or their specific technical approvals. Composed of PVC-P with a polyester mesh reinforcement, it offers excellent mechanical resistance and a lifespan exceeding twenty-five years. Its SRI index of 107 ensures high solar reflectance, limiting overheating and contributing to the building's thermal comfort. Easy to weld with hot air, the membrane guarantees a uniform and durable seal, while meeting the requirements of EN 13956. Tear-resistant, hail-resistant, and UV-resistant, it combines performance, longevity, and aesthetics.

By Brice-Alexandre-Roboam

Photo credits: Holcim and Balas

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