Ondsauna: Redefining Social Wellness in Japanese Forests

Taro Shimokawa’s award-winning sauna fosters connection through innovative design

Ondsauna, designed by Taro Shimokawa, challenges traditional notions of public saunas in Japan by creating a space that balances privacy and connection. Unlike conventional saunas, which often fail to nurture a sense of community, Ondsauna draws inspiration from Japan’s unique cultural approach to closeness. The design employs “non-intrusive” vertical walls that echo the surrounding forest, inviting nature into the space while modulating the intimacy between guests. This approach encourages shared understanding without imposing forced interaction, redefining the social dynamics of sauna culture.

The structure’s most distinctive feature is its vertical exterior walls, which cluster around the sauna room like trees reaching skyward. This motif is further expressed through a spiraling path that ascends to a rooftop relaxation area, allowing guests to experience the forest at treetop height. The journey from the sauna entrance to the cold plunge deck and finally to the open-air rooftop follows a vertical progression, mirroring the natural growth of trees and offering visitors a unique perspective on the surrounding landscape.

Ondsauna’s floor plan is an irregular polygon, carefully designed to guide sightlines and create a variety of scenic views. Research indicates that conversations are twice as likely to occur at 90-degree angles compared to side-by-side seating. To harness this insight, the sauna features obtuse-angled benches that strike a balance between encouraging interaction and preserving privacy. Varied seating arrangements cater to different social preferences, while the central fire becomes a focal point for shared experiences, subtly fostering a sense of community.

From a technical standpoint, the structure utilizes a 150mm CLT (cross-laminated timber) floor slab, which eliminates the need for beams and non-perpendicular joints. This not only streamlines construction but also enhances the rationality and efficiency of the building process. The modular walls are discretely assembled and connected by the CLT slab, resulting in a sociopetal structure—one that naturally draws people together while respecting individual boundaries.

Ondsauna’s innovative design has earned it the Bronze A' Architecture, Building and Structure Design Award in 2025. This accolade recognizes projects that demonstrate creative ingenuity, technical excellence, and a commitment to improving quality of life. By seamlessly integrating art, science, and technology, Ondsauna exemplifies how thoughtful design can transform everyday experiences and foster meaningful connections in contemporary society.

As a testament to the power of architecture to shape social interactions, Ondsauna invites guests to share in the rhythm of the forest, offering a sanctuary where nature, design, and community converge.