A wide thatched roof seems to lift in the wind over a field edge in Ibaraki Prefecture, Japan. Beneath it sits the Kagaku no Sato Main House, a 137-square-meter wooden building designed by Kengo Kuma & Associates (@kkaa_official). This building was completed in September 2025, and it has since received the Encouragement Award (Jury Chairperson’s Award) at the Wood Design Awards 2026.
The house anchors Kagaku no Sato, a long-running effort to restore a satoyama, the rural landscape in which farming and managed woodland exist side by side. The site lies among cultivated fields at the edge of a dense forest. For this project, Kuma studied the region’s traditional thatched dwellings. He took their rounded forms and their reliance on locally available materials as his starting points.
Kuma’s respect for traditional Japanese building forms has a parallel in Hanamurasaki’s Modern Revival of a 125-Year Ryokan, which shows how historic wooden architecture can be updated with contemporary design.
Twenty-eight logs hold up a wind-shaped thatch
The roof rises and dips around a circular plan, and its curve is not symmetrical. The asymmetry responds to the prevailing north-south winds and lets sunlight in from the south. Twenty-eight logs, harvested through local forest thinning, fan outward beneath the thatch to form the structural shell. Two heavy timber columns and a single ridge beam support them.
The geometry called for a mix of old and new methods. Each timber was 3D-scanned, so local craftsmen could cut the joints and assemble the radial framework with accuracy.
The thatch follows an Ibaraki technique that combines rice straw with reeds and grasses, the kind of craft found in thatched house japan villages. Skilled thatchers installed around 5,000 bundles. The layers form a thick, continuous surface, and that surface defines the building’s silhouette.
Earth, washi and stone inside the kengo kuma thatched house
Full-height windows sit beneath the deep eaves of this house and look out over the fields and forest. A continuous tataki floor runs between the interior and the exterior. Workers made it by compacting earth taken from the field directly in front of the house. The same soil was mixed into the outer walls, so the building’s color and texture come from its surroundings.
Inside the building, the exposed timber structure rises overhead. It reveals the bamboo framework and the rope bindings that hold up the thatch. The walls are finished with handmade washi paper, a craft recognized as an Intangible Cultural Property of Ibaraki Prefecture. Persimmon tannin treats the paper, which gives the walls their brown tone.
Locally sourced Makabe and Shirakawa stone appear through the building. A narrow upper level follows the slope of the roof. From there, visitors can see the radial timber arrangement up close, where it forms a dense canopy overhead.
A ridge that grows grass
At the roof’s peak, the team built a shibamune, a grass-covered ridge formed from soil collected on the site. Plants grow directly from the crest, and their roots help bind the earth. As the planting matures, the vegetation will spread across the roof and change with the seasons.
The thatch is also meant to be maintained within the landscape’s cycles. When sections age and need replacing, the removed plant material can be returned to the fields as compost. Timber thinned from the neighboring forest supports the house, and grasses cut from the surrounding land form its covering.
Timber used as both structure and public space appears again in A Timber Pavilion Turned Permanent Art Hub in Bergamo, a useful comparison for anyone curious about wood construction at a larger scale.
The house applies that view at a working scale. Its forms, materials and maintenance all draw on what the site already supplies.
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Frequently asked questions
Who designed the Kagaku no Sato Main House in Ibaraki Prefecture?
The Kagaku no Sato Main House was designed by Kengo Kuma & Associates. The 137-square-meter wooden building was completed in September 2025.
How many logs support the wind-shaped thatch roof?
Twenty-eight logs support the thatch roof, and they were harvested through local forest thinning. They fan outward beneath the thatch to form the structural shell, with two heavy timber columns and a single ridge beam supporting them.
What finishes the walls inside the Kagaku no Sato house?
The walls are finished with handmade washi paper, a craft recognized as an Intangible Cultural Property of Ibaraki Prefecture. Persimmon tannin treats the paper, which gives the walls their brown tone.
What happens to the thatch when sections need replacing?
When sections of the thatch age and need replacing, the removed plant material can be returned to the fields as compost. This allows the thatch to be maintained within the landscape’s cycles.
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