Curved CLT at Blumer Lehmann's new "Stammhaus" headquarters

In Gossau, Switzerland, the Blumer Lehmann company has opened its new headquarters, a wooden construction that is out of the ordinary. Dubbed the "Stammhaus" (Trunk House), the impressive four-storey edifice is distinguished by a free-form central staircase in the atrium, which rises like a modern tree trunk, inspiring the building's name.

Why does this building deserve our attention?

The new headquarters combines three important elements: innovative construction techniques, modern workspace and impressive architecture. Designed by K&L Architekten, the building brings wood to the forefront as the main material, demonstrating its versatility and architectural potential.

The centerpiece and focal point of the building is the free-form staircase in the atrium, made of massive curved wooden panels. This construction was developed in collaboration with Institute for Computational Design and Construction (ICD) of the University of Stuttgart. The staircase is not just a decorative element - it also has a structural role, connecting the four floors of the building in a spectacular way.

What makes this building technically special?

The curved components of the central staircase are made of the new curved CLT material (Cross Laminated Timber - curved cross-laminated timber) developed by Blumer Lehmann. This innovative technology enables the creation of complex, curved shapes in solid wood that are both rigid and structurally strong.

The impressive atrium structure, with its curved and flowing elements, demonstrates the technical and aesthetic potential of this new material. The curved panels not only provide an outstanding visual appearance, but also fulfill an important structural role in the building.

The wood material comes from the company's own factory, making this project an example of sustainability and local resource efficiency.

How does the building work in practice?

The "Stammhaus" houses 180 workstations on the four floors, a spacious entrance hall, an event hall and a café with adjoining terrace on the ground floor. The building combines the functionality of a modern office space with the elegant aesthetics of an innovative timber construction.

The office spaces are located along the facades, benefiting from natural light, while the central staircase connects all levels, facilitating circulation and interaction between employees.

How does the building address sustainability?

The building uses smart air conditioning solutions, avoiding conventional air conditioning systems:

• Natural ventilation and night-time cooling via ventilation flaps
• Active pylons that extract heat from the soil or dissipate it into the ground
• Front balconies with vertical slats offer natural protection from the sun
• Wooden stacking elements supplement sun protection where more comfort is needed

The façade of the building is inspired by traditional techniques of stacking wood for drying. It is not just an aesthetic element, but also has a functional role as a sunscreen, made of spruce slats resting on some 10,000 small supports similar to those used in wood storage.

From research to reality

The free-form atrium was an opportunity for Blumer Lehmann to extend its collaboration with the University of Stuttgart. For the researchers, the project enabled the development of computational design and production methods for curved wooden elements. For the company, the challenge has been turning this vision into reality.

The complex geometry and the thousands of holes drilled at different angles required extremely precise manufacturing, an effort that paid off at the assembly stage, when all the joints were perfectly matched.

Blumer Lehmann is now developing curved CLT as a commercial product, aiming for international approval for this technology.

The new 'Stammhaus' demonstrates that wood, a traditional material, can be reinvented with modern technologies, opening up new possibilities for the sustainable architecture of the future.