For more than 500 years, Biberach an der Riss, in the Bavaria region of Germany, has catered to Europeans looking to reap the healing effects of the area’s mineral-rich thermal waters. Among the destinations was Jordanbad, a site once occupied by a hospital that appears in historical documents dating to 1470. In 2003, a hotel built on the site in 1912 was renovated into the Parkhotel Jordanbad, with its spas, saunas, and thermal pools remaining signature amenities.
In 2012, Jordanbad’s sauna village, a collection of rustic log cottages, reached the tail end of a rather rapid decline. Just a decade old, the buildings had rotted beyond repair due to the perpetually damp environment. Plus, “they were pretty cheap,” says Christina Jeschke, principal of Jeschke Architecture and Planning, the Munich-based firm hired to renovate the village.
Although nothing could be salvaged, Jeschke, an expert in spa architecture, had plenty to draw on, including the hotel’s sylvan setting and the area’s vernacular architecture. Biberach is part of Germany’s Fachwerkstraße, or Half-Timbered House Road, which connects towns with exemplary timber-framed structures.
To create a place that felt both modern and welcoming to the hotel’s well-heeled guests, Jeschke maintained the concept of a “village around a lake,” with three sauna buildings and shower facilities clustered around a pond. In a nod to the region’s heritage, the gable-roof, residential-scale structures make extensive use of wood. At the same time, the buildings are simple, concrete boxes with floor-to-ceiling windows that face the pond. Each is wrapped in a wood lamella of black locust (Robinia pseudoacacia) slats, oriented horizontally and vertically.
Given the fate of the cottages’ predecessors, Jeschke knew that specifying the right type of wood was crucial. For interior finishes, she chose SaunaPly, a plywood manufactured by Austria-based RoHol whose adhesive is unaffected by hot, humid air, thereby reducing formaldehyde emissions. For the saunas’ benches, she selected lightweight obeche wood, a poor conductor of heat. “You cannot use just any wood for a sauna bench because you will burn [yourself],” she says.
The infusion sauna posed the biggest challenge. It had to accommodate up to 120 people at a time without obliterating the intimate scale of the surrounding 400-square-foot saunas. A supersized version of the gable-roofed form “looked somehow ridiculous,” Jeschke recalls. Eventually, she cleaved the infusion sauna, creating two 900-square-foot volumes that intersect near their midpoint, creating a sufficiently large communal area while also offering secluded areas for everyday use. The final design “didn’t just come to me,” Jeschke says. “I had at least 40 versions.”
The intersecting form required her team to 3D model in ArchiCAD everything from the angles of the intersecting rooflines to the placement of the hemlock planks that finish the infusion sauna’s walls and ceiling. Building the model required significant work, she says, “but there were some things I wanted to see before [it was constructed].”
Jeschke’s work on the front end paid off. Because the hotel owners wanted to reopen for the fall season, the contractors had just five months to complete the sauna village. With the 3D model, they were able to prefabricate a majority of the buildings’ components, including the wood skins. Made out of 1.5-inch-wide slats spaced 1.5 inches apart, the preassembled lamella was hung in 7.5-foot-tall panels ranging in width from 5 feet to 9 feet.
Schreinerei Harald Geng, one of two timber contractors, continued the look on the interior. In the herbal sauna building, the SaunaPly, which provides a backing for horizontal walnut slats in the fireplace sauna, is left exposed. In the large infusion sauna, 3- to 8-inch-wide hemlock planks create horizontal bands that further animate the dramatic geometries created by the roof planes.
Between the interior wood panels and the precast concrete walls is 5 inches of Foamglas insulation. Despite being impervious to moisture, the rigid insulation was coated with a waterproofing paste on its interior face for added protection. For exterior walls, liquid waterproofing was applied the concrete. Interior and exterior wood finishes are held at least 1 inch off the wall substrates to allow for continuous ventilation.
Opened in 2015, the Jordanbad sauna village is a modern update to a centuries-old pastime. The saunas rely solely on the waste heat recovered from of the hotel's combined-heat-and-power facility, a first for a German spa, Jeschke says proudly. Her biggest accomplishment, however, may have been convincing her client that wood was not a liability. “It was quite some process to get the client on the [same page],” she says. Based on the owner’s response thus far, the architecture appears to have struck the desired balance between comfortable and contemporary.