Clockwork precision in timber construction

Interview with Taro Okabe, Fabian Scheurer and Felix Holenstein

Digital transformation is one of the key themes at BAU 2021. The new headquarters of Swatch, the Swiss watch manufacturer, is a good example of just what this new digital future could look like. Taro Okabe (Shigeru Ban Architects), Fabian Scheurer (Design-to-Production) and Felix Holenstein (Blumer-Lehmann) explain in an interview the special features of this spectacular building in the Swiss town of Biel, and outline the challenges involved in this collaborative project.

© Swatch
Particularly impressive at night: the Swatch Group’s new HQ in Biel, Switzerland

The interview

The new headquarters of Swatch has attracted much attention because of its free-form building skin. Not all of it positive. Loud lamentations rose from some quarters, while others rejoiced in the “Japanese playfulness” of this new structure. Can you tell us, Mr. Okabe, why your practice chose this particular language of forms? Shigeru Ban´s design for the Centre Pompidou (2007) in Metz also features a spectacular curved roof, but other buildings, such as the Nicolas G. Hayek Center in Tokyo, follow a strictly orthogonal grid.

Taro Okabe: There are a number of reasons why we chose this form. Firstly the project encompassed several buildings which we brought together in one volume, and this follows the L-shape of the plot. Secondly Shigeru Ban already knew Biel: That is where the mock-ups for the roof frame of the Centre Pompidou you mention was fabricated. When he visited the site for the building, he remembered that. In Switzerland there are experts and companies with unique capabilities in designing and fabricating complex constructions in wood. With the form of this building we reacted to the location and to the specific possibilities that Switzerland offered us as designers.

Our architecture is always developed around the particular context with its specific characteristics, and that is why the language of forms is so different from building to building. We design free forms when they are appropriate for the commission and for the site – not because we lean towards a certain aesthetic, or wish to express any socio-cultural attitude, as perhaps other bureaus do.

Felix Holenstein: It´s a paradox: In Switzerland there is a concentration of experts in creating free forms, yet still these forms only have a few fans in our architectural landscape. At the moment most of the projects with multi-curved surfaces that we are engaged in worldwide, are designed by architects from outside Switzerland.

Fabian Scheurer: I think there is interest in free forms in Switzerland. The problem is that although many architects can model these with Rhino and Grasshopper, they don´t know how to actually turn these visions into reality afterwards.

How did this collaboration come about and what was it like?

Fabian Scheurer: We were brought in by IttenBrechbühl, Shigeru Ban´s local partner. The special thing was that we had already started on digital modeling even before the tendering and contract stages. We know Shigeru Ban and Blumer-Lehmann AG, like what they do and have enjoyed working with them. Our first project with Mr. Okabe´s bureau was the Centre Pompidou in Metz, that was fabricated with another firm of timber constructors. With the golf clubhouse in Yeoju in South Korea (2008) we then all worked together for the first time. It is important to mention that with all these projects, the engineering, too, came from Switzerland: With Swatch also, Hermann Blumer and the timber construction engineers at SJB Kempter Fitze AG were a part of the well-functioning team.

Taro Okabe: From our point of view Design-to-Production and Blumer-Lehmann were a strong unit. We gave Mr. Scheurer and his team a Rhino model on the basis of which they then produced a 3D model for fabrication at Blumer-Lehmann. A number of things had to be adapted, above all the axes, but nevertheless the form remained virtually unchanged. Without this intermediate step, the design would have been very difficult to successfully implement. What impresses me is how close the finished building looks to the original design idea that we gave to our partners.

© Swatch
The complex timber construction was fabricated by Blumer-Lehmann AG on the basis of a 3D model

What were the biggest challenges that you had to master?

Felix Holenstein: It was difficult to guarantee the required precision. We had to achieve a tolerance of maximum five tenths of a millimeter. That was important because the node points in the construction are highly complex and the over 2,800 interstices were finished in three different ways. The filler elements are technically very sophisticated, in order to meet the high standards of insulation that apply in Switzerland. There are opaque, translucent and transparent panels. Some elements can be opened in case of fire to let the smoke out, others are fitted with photovoltaic cells. In the case of the translucent panels, these are pneumatic cushions that are fitted with polycarbonate panels for thermal insulation. The transparent elements are made up of four panes of glass with roller blinds in between. These elements are ventilated all the time to avoid condensation forming. As you see even the smallest inaccuracy would have led to many and major problems.

An additional complication was the decision to integrate the ducting for the building´s technical systems into the structural level. The girders had to be milled to make space for this, and that meant the engineers had to redo their calculations.

One other challenge of a practical nature was how to protect the very large structure (it is 240 m long and 35 m wide) from the weather on the building site. We solved this with giant tarpaulins that had to be made specially.

Fabian Scheurer: As well as the high degree of precision, I am proud of the very low error rate that we achieved together. 75,000 individual parts were designed and made for the building skin. And only two pre-assembled elements arrived on site faulty. And even they did not have to be thrown away, as we were able to adjust them. Altogether the error rate was equivalent to just over one part in a thousand.

But back to your question: In the end we not only produced the digital model for fabrication, but even before that, we had assumed a central coordinating role. That was a challenge, but it was also important so that the different trades could all work together, or rather around each other, on site. That would not have been possible without a central digital reference model.

Taro Okabe: The level of precision was also the main reason for working with Blumer-Lehmann. Internationally there are only few firms, if any, who can match them when it comes to implementing such a sophisticated structure and form.

Fabian Scheurer: For all the praise, I would like to mention one thing: Around 900 different cooling panels had to be designed and assembled, and it should have been defined very early on who would fit them, where and how, so that Blumer-Lehmann could have taken this into account in their fabrication, for example by marking the drilling points. We urged this, but were not able to convince everybody of this need. Not a big thing really, it all worked anyway, but it does say a lot: Digital prefabrication needs corresponding planning and adapted processes, and this message still has to get through to most building firms at this moment in time. Many are still stuck in the analog past.

© Swatch

One important theme and one that has had too little attention so far in architecture is sustainability.

Taro Okabe: Here, too, timber construction has advantages. 6,500 spruce and pine trees were used in this building, in other words around 2,000 cubic meters of wood. It has been calculated that this same quantity regrows in the Swiss forests within a few hours. Also, the building has over 442 photovoltaic cells; it has velospots (bikesharing) with charging stations and thermoactive components. Two tanks once used for oil have been re-purposed water storage on site.

© Swatch
A very high degree of precison was required in fabricating the free-formed building skin

What were you able to learn from the project that can be applied to future projects? And what direction do you think digitalization in the building industry will go in the coming years?

Felix Holenstein: We have learned much about complex forms and the use of our CNC machines. That helps us, for example, to save even more raw materials – all of which come from Switzerland, incidentally. And more generally we benefit enormously from such challenging projects – including in our more day-to-day projects. And the project demonstrates very well just what constructive and design potential wood can offer.

As for the second part of your question: I could imagine that in the long term robotics in timber construction could become a big theme. Experiments in this are already being conducted in many places, for example in Switzerland, at the National Centre of Competence in Research Digital Fabrication. Currently, however, with the robot arms available now, it is not yet possible to ensure high enough precision for buildings such as that in Biel.

Fabian Scheurer: What is important is that the planning of buildings and the organization and management of building processes have to be adapted further to the digital fabrication that is already existent. There is much to do here. That applies not only to projects with spectacular free forms, but in general. At the moment, quite simply, mostly old processes are being digitalized. Digital models are being used all too often just to produce 2D plans – that is like replacing the typewriter with a text-processing program and then stopping further innovation before the World Wide Web and hypertext had been invented.

We utilize our experience from projects like the Swatch headquarters in more conventional projects. For example, we have just been working on the construction of the “Crocodile” residential project in Winterthur. That was a tough training ground for us, once again we saw how much still has to change in planning prefabricated timber buildings.

Many thanks, Mr. Holenstein, Mr. Okabe and Mr. Scheurer for your time.

Strong partnership

Japanese star architect Shigeru Ban designed the new headquarters of Swatch in Biel. For the fabrication of the sinuous building skin, he turned to two known and trusted partners: Design-to-Production, specialists in parametric design, and the timber construction company Blumer-Lehmann AG, both from Switzerland.

The frame for this new building represents a milestone in timber construction, and it shows that digital prefabrication requires processes in design and construction that are specifically tailored to digitalization.

Published: April 20, 2020

This interview was conducted by: Elias Baumgarten,