The Urbach Tower by itke/ICD Stuttgart is a unique wood structure. The design of the tower emerges from a new self-shaping process of the curved wood components. This pioneering development constitutes a paradigm shift in timber manufacturing from elaborate and energy-intensive mechanical forming processes that require heavy machinery to a process where the material shapes entirely by itself. This shape change is driven only by the wood’s characteristic shrinking during a decrease of moisture content.

Components for the 14 m tall tower are designed and manufactured in a flat state and transform autonomously into the final, programmed curved shapes during industry-standard technical drying. This opens up new and unexpected architectural possibilities for high performance and elegant structures, using a sustainable, renewable, and locally sourced building material.

The Urbach Tower constitutes the very first structure worldwide made from self-shaped, building-scale components. It not only showcases this innovative manufacturing approach and resultant novel timber structure; it also intensifies the visitors’ spatial involvement and landscape experience by providing a striking landmark building for the City of Urbach’s contribution to the Remstal Gartenschau 2019.

In timber construction, moisture typically causes problems with cracking and deformation; hence, moisture changes and stress development must be carefully controlled. In contrast, in this project wood is programed and arranged in a way to utilize this powerful, naturally occurring deformation to trigger a designed self-shaping behavior. In the same way that machines can be programmed to perform different movements, wood parts can be programmed to transform into predetermined shapes when dried.

While methods of bending wood into different shapes for structure and aesthetics have existed for centuries and have become recognized industrial processes, they still mostly rely on brute mechanical force for the shaping process. Similarly, an understanding of how wood deforms due to changes in moisture content is well known in practice and academics. However, a shift in design thinking, as well as new computational simulations for more accurate prediction, now allow designers to use this moisture induced swelling and shrinking to design and program specific self-shaping movements at larger and larger scale.

The pioneering development of large-scale self-shaping constitutes a paradigm shift in timber manufacturing from elaborate and energy-intensive mechanical forming processes that require heavy machinery to a process where the material shapes entirely by itself. This shape change is only driven by the wood’s characteristic shrinking during a decrease of moisture content. The curved Cross Laminated Timber (CLT) components for the tower’s structure are designed and produced as flat panels that deform autonomously into predicted curved shapes when dried.

The 5.0 m x 1.2 m spruce wood bilayers parts are manufactured with a high wood moisture content and specific layups and dried in an industry standard technical drying process. When removed from the drying chamber the parts are precisely curved. The parts are overlapped and laminated together to lock the geometry in place, forming larger curved CLT components with form stable geometry. Material specific computational mechanics models have been developed to both design, predict, and optimize the material arrangement required to produce different curvature types and radius.

The technology of self-shaping manufacturing for solid timber boards and the rapid adaptability of the process to different curvatures open up new and unexpected architectural possibilities for thin shell wood structures, using a sustainable, renewable, and locally sourced building material. The Urbach Tower is the very first implementation of this technology on building-scale, load-bearing timber parts.

The self-shaping components are made entirely of spruce wood boards sourced regionally from Switzerland. Individual components span up to 15 m with a radius of 2.40 m and a structural thickness of only 90 mm. The components are 5-Axis CNC cut and detailed from half cylinder blanks and pre-assembled into building groups of three components for transport, including water barrier and external wood cladding.

The Urbach Tower consists of 12 curved components made from cross-laminated timber. The tower’s load-bearing structure exhibits a thickness of 90mm while cantilevering over 14 meters resulting in a span to thickness ration of approximately 160/1. The inherent curvature enables a highly slender and lightweight tower structure of only 38 kg per square meter surface area. In the assembled state, the tower acts as a surface-active structure through its expressive curved geometry.