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BY-NC-ND 4.0 license Open Access Published by De Gruyter 2023

HYGROSHELL – In Situ Self-shaping of Curved Timber Shells

From the book Advances in Architectural Geometry 2023

  • Dylan Wood , Laura Kiesewetter , Axel Körner , Kenryo Takahashi , Jan Knippers and Achim Menges


Curved, surface-active, shell structures are known for material efficiency and slenderness but typically require complex manufacturing and formwork in combination with intricate on-site construction processes. The presented research proposes an alternative approach: a self-shaping building system for deploying lightweight, curved surface structures made from timber. The system uses the inherent hygromorphic properties of wood which naturally shrinks through drying. This anisotropic shape change is embedded into large-scale bilayer sheets - produced, machined, and shingle clad in a flat state with their later curved shape and connection detailing physically programmed within the material build-ups. When placed on-site, these sheets actuate through air drying to a final curved and interlocked geometry. Geometrically the structure is integratively designed from variable single curved surfaces using key material parameters (end grain angle and moisture content change) within a material stock, in relation to both the self-shaping and the final structural configuration. Each surface is modeled in the curved state using a board specific algorithmic calculation of curvature potential in parallel to a flat fabrication model. Emphasis is placed on investment in early-stage planning and intelligent material arrangement as a method to produce useful curvature. As a result, the curved shell shapes and interlocks without formwork or external mechanical force, with little onsite work. The outcome is a lightweight, longspan roof structure built from single curved wood surfaces with a thin cross-laminated build up. The project demonstrates a tangible new method of low impact, light touch self-construction and an ecologically effective use of material and geometry.

© 2023 Walter de Gruyter GmbH, Berlin/Boston
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