The inner courtyard of Kufstein Castle in the Austrian Alps forms a natural amphitheater for music, theater and special events—when the unpredictable mountain weather isn’t a show-stopper. Restoration of the medieval Kufstein castle and grounds, begun in 1997, featured terraces and seating for an amphitheater audience of 4,500, but weather-related ticket cancellations crimped profits and kept patrons away. It wasn’t until 2006 that Kugel + Rein Architekten und Ingenieure, architects based in Stuttgart, Germany, raised a retractable roof that allows the show to go on.
The roof consists of a radial cable-stayed fabric canopy that opens or closes like an umbrella on demand within four minutes, providing reliable shelter for amphitheater events. Kugel + Rein faced stiff restrictions for the landmark site, including prohibition of any anchorage into the existing fort or interference with the castle’s striking visual appearance. The design, a smooth, translucent white membrane disk that protects without restricting the breathtaking views, met all the criteria. Along the perimeter of the structure, scalloped cables and tangential webbing connect to trolleys that tension the fabric when fully extended, eliminating wrinkles and ponding. Rainwater is channeled down the sides and collected along the perimeter in flexible rain gutters. When closed, the draping white membrane looks something like a floating tiara.
Sefar® Architecture’s Tenara® fabric, woven from high-strength expanded ePTFE fluoropolymers and fluoropolymer-coated, was used to create the retractable circular shelter over the 21,000 sq. ft. courtyard. “The fabric roof is the most important part of our facility,” says Emanuel Praauer, marketing and communications director for the Fortress Arena Kufstein. “Because of it, we can effectively use the facility year-round, allowing us to hold many more events.” The Tenara fabric offers 38 percent light transmission, to retain the outdoor feel of the arena, and will flex and fold without wear or losing strength.