The malleability of PVC membranes offers significant architectural potential. A prime example is this municipal building on the Mediterranean coast, where waterproofing serves aesthetics for a stunning result.

Led by the Terre de Camargue inter-municipal authority and the town of Grau-du-Roi, the project for the new community center and media library in the town center represents a major step in the urban renewal of the district. Spanning a total area of 1,900 m², the public facility combines a 1,300 m² community hall on the ground floor and a 600 m² media library on the first floor, designed to welcome the local community and offer a multi-purpose space dedicated to social interaction, culture, and community spirit. The architecture firm Ateliers A+ conceived this project as a landmark for the town, drawing inspiration from the maritime heritage of Grau-du-Roi and the characteristic landscapes of the Camargue. The undulating roof, a true signature of the building, evokes the movement of waves, while two accessible roof terraces echo the planted dunes and the pontoons of the seaside.

Technical Expertise and Rigorous Planning

To bring this unique approach to life, professionals comfortable with the technical aspects were needed. The Soprema Entreprises agency in Montpellier was chosen to handle the waterproofing of the entire building. On the main roof, covering 1,350 m², the teams installed a Flag single-layer PVC membrane (Flagon SR Silver Art) over a curved steel deck, complemented by double-layer rock wool insulation. The roof terraces, also waterproofed, were equipped with supports for future tiling, thus providing future users with outdoor relaxation and reading areas, offering an unobstructed view of the tiered planters that compensate for the 20% slope. The technical implementation was meticulously planned down to the smallest detail. The steel tray, nailed to the metal frame and stitched every meter with self-drilling screws, formed the basic support. On top of this, the team installed a Sopravap Stick S16 elastomeric bitumen vapor barrier, followed by two layers of 100 mm thick insulating panels, providing a thermal resistance of R = 5.20 m².K/W. The panels were laser-cut for precise alignment with the overhangs, ensuring a perfect finish and complete waterproofing. Over 2 km of 1.8 mm thick Flag PVC membrane were installed on the main roof, supplemented by Flagon CSL membrane for specific points and upstands. Pyramidal profiles, spaced 60 cm apart, enhance the aesthetic appeal and replicate the effect of standing seam zinc. The Glossy finish offers a brilliant gray that reflects light and blends with the surrounding landscape, while also providing an economical alternative to traditional zinc.

Coordinating the construction site required meticulous planning and perfect logistical anticipation. Materials were received and stored according to the installation phases, and teams were organized into pairs to maximize safety and efficiency. Creating a prototype before work began allowed for validation of the membrane's weldability and the fixing of the pyramidal profiles. Training the roofers in these specific techniques was key to guaranteeing the final quality of the undulating roof.

Safety First on the Construction Site

This construction site is distinguished by the complexity of its roof: “Every construction site has its own unique characteristics. For this one, it’s undoubtedly the atypical shape of its roof, which reaches a height of 16 meters, with slopes ranging from 15% to over 50%,” recalls Hugo Fournel, site manager at Soprema Entreprises Montpellier. To comply with the weight restrictions imposed by the structure and ensure the safety of the workers, a maximum of three or four roofers worked simultaneously on the roof, always securely attached to temporary longitudinal and transverse lifelines. Deploying the materials required the use of a crane truck on two of the four sides, followed by handling to the highest points. The combination of a high-performance membrane, specific profiles, and high-performance insulation provides not only durable waterproofing but also optimal thermal comfort for future occupants.

A membrane designed for both aesthetics and performance

Soprema's Flag PVC waterproofing membrane (Flagon SR Silver Art) combines technical performance, durability, and aesthetic appeal. At 1.8 mm thick, it is designed to withstand harsh weather conditions, including wind, hail, and UV rays, while maintaining the flexibility needed to adapt to the complex and undulating shapes of roofs. Ideal for standard sections and upstands of exposed flat roofs, it is reinforced with a polyester mesh and installed using semi-independent mechanical fasteners. It ensures a perfect seal, even in the most complex areas, and its strength guarantees maximum durability. Designed to maintain its performance over time, it offers flexibility at low temperatures, puncture resistance, and the safety of a flame-free worksite. Its two colors (Copper for the copper look and Silver for the silver look) allow for the faithful reproduction of certain material aesthetics, like the zinc in the construction site opposite.

By Brice-Alexandre-Roboam

Photo credits: Drone OPS-Soprema Enterprises

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