Flax and timber as hybrid pioneers
Two architectural innovations made their debut on the world stage at the Landesgartenschau in southern Germany’s Allgäu region: the self-shaping Wangen Tower made of wood and the Hybrid Flax Pavilion with robotically produced flax sections that reduced the quantity of wood needed for the structure by two thirds.
In 2024, the city of Wangen (Allgäu) hosted the 30th Baden-Wuerttemberg Landesgartenschau, the region’s annual garden show that displays swathes of colourful flowers. Visitors to the grounds were the first to set eyes on two architectural highlights whose designs are global innovations. These parametrically designed lightweight structures have resulted from decades of research at the University of Stuttgart, and show how stable, bio-based constructions can be built with minimum resources. “This is important because although wood is a renewable resource, it must also be used sparingly. Its climate-friendly effect can only be maximized if it is employed as efficiently and economically as possible in each individual construction project,” says Prof. Achim Menges, head of the Institute for Computational Design (ICD) at Stuttgart University.
The self-shaping tower
One of these constructional innovations is the Wangen Tower. At a height of 23 metres, this new landmark forms a striking silhouette against the gently rolling hills of the Argental valley. Its resource-friendly design is a beacon with global reach. According to the University of Stuttgart, it is the “world’s first climbable observation tower using curved, large-scale structural components that self-shape as the wood shrinks”.
Although wood is a renewable resource, it must also be used sparingly. Its climate-friendly effect can only be maximized if it is employed as efficiently and economically as possible in each individual construction project.
Prof. Achim Menges, head of the Institute for Computational Design (ICD), University of Stuttgart
The wooden tower consists of 12 load-bearing, curved segments made of cross-laminated timber, which are only 13 centimetres thick. Prefabricated by Swiss timber engineering company Blumer Lehmann as six structural elements, the tower was assembled in just three days. The most extraordinary factors here are the slimline timber structure with its “active” layers, and also the technique used to curve the wooden components.
It is usually seen as a disadvantage when moisture causes timber to change shape. But this process was incorporated quite deliberately here, as the researchers imitated its natural response. In the same way as spruce cones open up while they dry, this shrinkage was harnessed to produce the curved shape of the wood via controlled warping of bilayer segments. And so in this case, more shape meant less material.
Flax as a building material
Just a short walk from the tower, where the rewilded River Argen meanders, visitors find the second architectural highlight. The Hybrid Flax Pavilion is a round building with an undulating roof that shows no sign of this innovative lightweight construction method from the outside. But once inside, the space is dominated by this extraordinary roof construction.
In the natural world, almost all load-bearing structures consist of fibres. The pavilion is the result of over 15 years of research into biomimetic structures in architecture.
Prof. Achim Menges, head of the Institute for Computational Design (ICD), University of Stuttgart
Besides the principal wave form, many other waves are created by the bulging flax bodies. These elements were robotically wound around a steel frame that moulded their shape, and they consist of a flax fibre composite that was processed while wet and hardened later on. As soon as the structural component dried, it was removed from the frame and the next flax body could be wound. This technique of coreless winding for large fibre structural components was developed by ICD and the Institute of Building Structures and Structural Design (ITKE) at the University of Stuttgart, which received the German Design Award 2025 for these two new buildings.
Imitating nature
The flax was combined with timber beams to produce the roof structure, and here too nature was imitated in many ways. “The pavilion is the result of over 15 years of research into biomimetic structures in architecture at ICD and ITKE,” explains Menges. “In the natural world, almost all load-bearing structures consist of fibres. Over the years, many operating principles in natural systems have been examined in collaboration with biologists at Freiburg and Tübingen universities, with the results then being adopted by construction engineering. These are also encountered in the flax fibre bodies.”
The result is a hybrid structural system with a very economical use of renewable resources. According to the University of Stuttgart, the pavilion is the first building in the world to employ natural fibres in this way. “Fast-growing flax fibres supplement the loadbearing capacity of timber, which grows slowly, as part of the hybrid structural system. This reduces the amount of timber by about two thirds compared to a construction that only uses wood,” adds Jan Knippers, head of the ITKE at Stuttgart University.
Innovation with major potential
There is huge potential behind this innovation. Menges envisages scaling it up above all in the area of “large-span roofs where performance of the structural system is prioritized and fire safety demands are less stringent”. To achieve this, it would require a progressive client, such as the Landesgartenschau in Wangen. “As shown by the pavilion, this innovative hybrid wood-fibre construction method is already viable today.”
Fast-growing flax fibres supplement the loadbearing capacity of timber, which grows slowly, and reduce timber requirements by about two thirds.
Jan Knippers, head of the Institute of Building Structures and Structural Design (ITKE), University of Stuttgart
People are mainly familiar with flax from textile production, which is strongly linked to geographical surroundings. Wangen’s old spinning mill – formerly the processing facility for the plant fibres – was refurbished for the garden show. While the production of textile fibres is steeped in tradition, nowadays flax is also found in many different areas such as insulating material, furniture production and interior panelling for cars.
Indeed, flax has the ability to become the plastic of the circular age. Supply is currently lagging behind, though – in some cases demand has outstripped flax fibre production for years to come, Menges adds. The fact that natural fibres are now being employed for load-bearing construction elements as well reveals the innovative potential slumbering in bio-based raw materials. For timber as a construction material, it shows that wood can be used more efficiently and therefore more frequently in the future. This is truly a further step in the green building revolution.
Text: Gertraud Gerst
Translation: Rosemary Bridger-Lippe
Photos: ICD/ITKE/IntCDC University of Stuttgart, Roland Halbe