NIKO Design Studio Completes Sculptural Timber Guesthouse in Chiba, Japan
A circular facade and curved sauna define this unique residential project in Japan.
1Architectural Landmark in Chiba
NIKO Design Studio recently completed Umino Marumi, a two-story wooden guesthouse located on a hillside overlooking the Pacific coast in Chiba, Japan. Finished in 2025, the structure serves as a second home for the owners, designed to facilitate gatherings with friends and family while maintaining a welcoming presence within the local residential neighborhood.
2Circular Facade Design Concept
The house is defined by an enormous circular opening cut into its dark exterior facade. This architectural feature reveals a complex network of timber columns and raised walkways. Approximately one-third of the building is dedicated to an engawa, a traditional Japanese veranda that allows visitors to move between levels without entering enclosed rooms.
3Traditional Timber Construction Methods
The structural frame utilizes substantial cedar logs measuring 400 millimeters in diameter, assembled using traditional kanuki joinery. Horizontal timber members pass through openings in the round columns to create a durable, geometric frame. Carpenters used chainsaws to cut the specific holes, drawing inspiration from forestry techniques to ensure the wood's natural integrity remains.
4Craftsmanship in Landscape Design
To address the sloping site, the team constructed a stone retaining wall using the nozumi technique, which involves traditional stone-stacking methods. This project was completed during a two-day workshop, integrating rough stonework alongside the large timber structure. This hands-on approach highlights the studio's commitment to craftsmanship and communal building practices throughout the site.
5Sauna Hut Design Inspiration
The garden features a small, freestanding sauna hut designed to accommodate the surrounding vegetation. Architects noticed a neighboring palm tree extending over the property boundary, which inspired the building's unusual curved roof profile. By sourcing naturally bent timber from hillside trees, the structure rises and dips to avoid interfering with the existing local landscape.
6Compact Sauna Spatial Efficiency
Despite its expressive exterior, the sauna occupies only five square meters of ground space. The foundation measures two by two meters, yet the interior accommodates up to six people due to its tall ceiling and tiered bench layout. The hut utilizes both electric and wood-fired heating systems, complemented by a skylight for natural illumination.
7Integration of Structural Details
During the sauna construction, the team received timber beams that were thicker and longer than originally anticipated. Rather than trimming them, the architects decided to retain the excess length, allowing the beams to project beyond the roofline. This unexpected detail adds significant character to the small building while showcasing the raw, organic material properties.
8Dual Scales of Architecture
The Marumi project explores two distinct scales of wooden architecture within a single property. While the main guesthouse opens itself toward the neighborhood through its large circular frame, the sauna hut adjusts its form to respect the existing trees. Together, these buildings demonstrate a thoughtful balance between communal living and environmental integration.