Kamegaike Onsen by Yano Aoyama Architecture Design

Kamegaike Onsen is a carefully considered reconstruction project that repositions a traditional Japanese bathhouse as a contemporary engine for regional revitalization. Designed by local practice Yano Aoyama Architecture Design, the project emerged from a national competition following a lightning strike that severely damaged the original hot spring facility. Rather than pursuing an iconic replacement, the architects proposed a modest yet imaginative rehabilitation rooted in community participation, local materials, and environmental responsibility.

Located in the Kamegaike district of Ikata—an area facing population decline and economic challenges—the renewed onsen extends beyond its role as a bathing facility. It operates as a multifunctional social hub where residents and visitors can bathe, eat, shop, stay overnight, and interact, reinforcing everyday life while attracting new activity to the region.

A participatory design process played a central role in shaping the project. Local high-school and university students were involved early on, contributing to a spatial strategy that distributes small, cloistered rooms across the preserved bathhouse structure. These dispersed spaces host diverse programs, transforming the onsen into a porous socio-economic magnet rather than a singular destination.

Material selection anchors the architecture firmly in its context. Timber dominates both structure and finish, reflecting Ehime Prefecture’s rich forestry resources. Locally sourced cedar, treated using traditional yakisugi charring techniques, clads the exterior, ensuring durability while referencing regional building traditions. Interior elements incorporate aoishi stone partitions and kumaishi rammed-earth walls, constructed from soil excavated directly from the site, further reinforcing material continuity with the landscape.

Structurally, the project preserves existing foundations, adopting a lightweight timber grid system supported by glulam horizontal members and slender 105 × 105 mm columns. An ascending-beam roof (nobori-bari) spans the central areas, creating a generous interior volume beneath which earthen walls conceal services and guide circulation without disrupting spatial continuity.

Sustainability strategies are integral rather than supplemental. Discarded lumber supplied by local sawmills fuels new firewood furnaces that complement existing oil boilers, while rooftop solar panels contribute significantly to energy production. Together, these measures enable renewable sources to provide approximately 76% of the facility’s operational energy. A newly installed lightning rod addresses the cause of the original destruction, ensuring long-term resilience.

Through close collaboration with local craftsmen, builders, and stakeholders, Yano Aoyama Architecture Design expanded the scope of the initial competition brief, embedding ecological systems and community management into the project’s future. Kamegaike Onsen stands as a model of contemporary hospitality architecture—one that balances tradition and innovation while anchoring itself deeply within place, people, and memory.

All the Photographs are works of Nishikawa Masao