In the serene landscapes of Ibaraki Prefecture, Japan, renowned architecture firm Kengo Kuma and Associates has completed the Kagaku no Sato Main House. This 137-square-meter wooden building, set beneath a sweeping, circular thatched roof, bridges ancient architectural vernacular with cutting-edge digital fabrication. Completed in September 2025, the project has recently earned industry recognition, receiving the Encouragement Award—also known as the Jury Chairperson’s Award—at the Wood Design Awards 2026.
Situated at the edge of a dense forest and framed by cultivated fields, the structure is defined by its broad roof, which curves gently upward at the edges to appear almost lifted by the wind. The building serves as the architectural centerpiece of Kagaku no Sato, a long-running regional initiative dedicated to the restoration of a traditional Japanese satoyama. A satoyama represents a deeply harmonious rural landscape where sustainable agriculture and managed woodlands coexist in a delicate ecological balance. In designing the main house, principal architect Kengo Kuma looked directly to the region’s historical thatched dwellings, drawing profound inspiration from their rounded organic forms and their time-tested reliance on locally available materials.
28 Timber Logs Form the Sweeping Roof
The defining architectural feature of the Kagaku no Sato Main House is its enormous thatched roof, which dynamically rises and dips around a circular floor plan. The asymmetric curvature of the roof is not merely aesthetic; it is meticulously engineered to respond to prevailing north-south wind patterns while inviting abundant sunlight deep into the interior from the southern exposure.
Beneath the dense layers of thatch, twenty-eight structural timber logs—harvested directly through local forest-thinning initiatives—fan outward to create a resilient structural shell. This radial framework is unified and supported from within by two hefty timber columns and a single central ridge beam, showcasing an elegant economy of means and materials.
Realizing the architects’ unusual and complex geometry required a seamless synthesis of traditional carpentry and advanced digital technology. Each individual timber log was thoroughly 3D-scanned, allowing local craftsmen to precisely shape the intricate joints and assemble the radial framework with a level of accuracy that bridges historic craftsmanship with modern computational design.
The roof itself honors regional Ibaraki thatching traditions, utilizing an expert blend of rice straw combined with local reeds and grasses. Approximately 5,000 individual bundles of thatch were meticulously installed by skilled traditional thatchers, resulting in the thick, continuous, weather-resistant surface that grants the building its striking silhouette.
Earthen Floors Connect the House to Its Surroundings
Beneath the deep, protective eaves of the roof, full-height windows open up wide views toward the surrounding agricultural fields and the adjacent forest. A continuous tataki floor—created using traditional techniques by compacting earth collected directly from the field immediately in front of the house—blurs the physical boundaries between interior living spaces and the exterior landscape.
This same local soil was thoughtfully incorporated into the composition of the outer walls, imbuing the structure with a natural color palette and tactile texture drawn straight from its immediate environment. Stepping inside, the exposed timber structure rises overhead to reveal the intricate bamboo framework and natural rope bindings that securely hold the thick thatch in place from below.
The interior spaces are rich with the warmth and honesty of unpretentious natural materials. Handmade washi paper, crafted via a regional method officially recognized as an Intangible Cultural Property of Ibaraki Prefecture, is finished with traditional persimmon tannin, washing the walls in deep, organic brown tones.
Locally sourced Makabe and Shirakawa stone appear thoughtfully throughout the building, anchoring the architecture to the geological specifics of the locale. A narrow upper level follows the sloping interior contour of the roof structure, offering occupants an intimate vantage point from which to experience the dense canopy of the radial timber framework up close.
A Living Ridge Grows Above the Thatch
At the highest structural apex of the roof, Kengo Kuma and his team introduced a traditional shibamune, a living, grass-covered ridge constructed using soil harvested from the surrounding land. Indigenous plants grow directly from the crest of the roof, their root systems weaving through the earth to naturally stabilize the ridge against weathering. As the seasons change and the vegetation develops, the roof actively evolves, effectively extending the surrounding flora onto the architecture itself.
The thatched surface similarly participates in the cyclical rhythms of the local landscape. As sections of the thatch inevitably age over time and require maintenance or replacement, the removed plant material can be returned directly to the adjacent fields to serve as nutrient-rich compost. This circular relationship between construction, maintenance, and agricultural cultivation lies at the very heart of the Kagaku no Sato project. Timber thinned from the neighboring woodland supports the shelter overhead, while grasses harvested from the open landscape form its protective crown.
The completed building successfully translates these longstanding regional practices into a contemporary architectural idiom, proving that the most compelling design features can emerge directly from the resources, ecology, and heritage craftsmanship of the surrounding region.
The project was realized through the collaborative efforts of Kengo Kuma & Associates, alongside structural engineering by Ejiri Structural Engineers, construction by Eiwa Construction Company, and building services by Studio Nora. The design team included Tomonori Kusagaya, Koichi Hirabayashi, Fumiya Kaneko, and Kazuya Tachibana, with photography provided by NTV and Ryohei Sawaki.
