Highlight at the National Horticultural Show in resource-conserving timber design

The topping out ceremony for the viewing tower in Wangen was celebrated on 25 March 2024. Comprising six curved cross-laminated timber components and erected in just three days, the tower provides a panoramic view over the Allgäu landscape and is sure to prove a future highlight for the National Horticultural Show. In terms of its construction, this tower is unique – it is the first accessible tower in the world to use curved wooden components made up of glued cross-laminated timber formed by the natural shrinkage process of the wood. Beyond this year’s National Horticultural Show, the tower will stand as a symbol for a building culture in which ecology and progressive technology are combined.

Innovative design

This innovatively designed tower is the product of a collaboration between project partners ICD University of Stuttgart – Prof. A. Menges, ITKE University of Stuttgart – Prof. J. Knippers and the associated Cluster of Excellence Integrative Computer-aided Design and Construction for Architecture (IntCDC), the Wangen National Horticultural Show in Allgäu 2024, and Blumer Lehmann. As general contractor, we were responsible for the production and structural implementation of the project, as well as contributing to the development of the execution schedule and production methods. Development of the production methods for these highly complex elements was completed in a very short period of time. The curved cross-laminated timber and specialised connections were tested by the Materials Testing Institute in Stuttgart, and an inspection was even carried out at our business premises. All relevant production stages had to be documented and safeguarded through an in-house production control.

Focus on sustainability

Our project team was prominently involved in detail development and the formulation of solutions, including factory and erection planning, as well as the development and production of the curved CLT components. The team’s assignments also encompassed the framing, preassembly, final assembly and mounting of the external cladding. Sustainability is also at the forefront of the 22 m-high tower with its base area of 50 m2: the foundation is made of recycled concrete and cement produced with low CO2 emissions. The rear-ventilated, 20 mm thick exterior cladding consists of vertically mounted solid larch wood panels.

Biology as a role model

According to Professor Achim Menges, Head of the Institute for Computational Design and Construction at the University of Suttgart, the design of the viewing tower is based on two principles of biology. Firstly, shrinkage of the timber for a controlled change in shape is used to full advantage for the self-forming components – in a similar process to that of pine cones opening up as they dry. And secondly, more shape means less material. The form of the tower thus allows for a resource-conserving timber construction.