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Urbach Tower Pioneers “Self-Shaping” Wood Construction Technique

The elegant, curved lines of the Urbach Tower in Germany’s Rems Valley and the idyllic landscape around it are certainly worth your attention, but the real story here is in how the 46-foot tower came together. Created by a team from the University of Stuttgart’s Institute of Computational Design and Construction (ICD) and Institute for Building Structures and Structural Design (ITKE), it’s the first example of a “self-shaping” wood construction process.

Though various methods of bending wood have existed for centuries, those typically involve elaborate mechanical forming processes that require heavy machinery. Looking for a less energy-intensive method, the team thought to harness the characteristic shrinking of wood as it loses moisture to essentially “trigger” the wood to twist itself into shape.

“An understanding of how wood deforms due to changes in moisture content is well known in practice and academics,” the team explains. “A shift in design thinking, as well as new computational simulations for more accurate prediction, now allow us to use this moisture-induced swelling and shrinking to design and program specific self-shaping movements at larger and larger scale.”

It all starts with flat panels of cross-laminated timber (CLT) made of spruce wood sourced in Switzerland and manufactured with a high wood-moisture content of roughly 22 percent. That level is brought down in an industrial drying chamber before the pieces are laminated to create the 12 large panels that make up the final structure. Computational models were developed to design, predict, and optimize the material arrangement required to produce the desired curvature.

“While making this work is relatively simple, predicting the outcome is the real challenge,” said ICD head Achim Menges. “Being able to do so opens up many new architectural possibilities.”

A layer of glue-laminated larch wood is added on the outside to protect from UV radiation and fungi. The larch wood will allow the structure to take on an even, white color over time—resembling the traditional white chapels of the area.

Once the desired curvature was achieved, the components were put together on site by only four craftsmen, who were able to assemble the tower in a single working day without a huge scaffold or any formwork.

Installed as one of 15 small structures for the Remstal Garden Show, the tower is already a landmark in the city and will be on view permanently.