A masterpiece made of architectural concrete
Extension of Kunsthaus Zurich places great demands on master builders
Data & Facts
- Extension of Zürich Art Museum, Zurich (CH)
- Project management / principle
- Zürich, Amt für Hochbauten
- Marti AG, construction company, Zurich
- MEVA systems
- Engineering and support
- MEVA Schalungs-Systeme AG, Seon (CH)
High-quality concrete finishes
Based on a design by star architect David Chipperfield, an open, light-flooded, cuboid-shaped building has been erected in the Swiss city of Zürich. The construction company Marti AG took on the architectural and structural engineering challenges together with MEVA and created a structure that resembles a concrete sculpture.
Approximately two years after the start of construction, Marti AG completed the building shell according to plan. In the meantime, the extension of the art museum has become a resplendent eye-catcher in the centre of Zürich. As of this October, art lovers from around the world will be able to wander around the superb new building. Carefully located height differences between the rooms create a pleasant atmosphere. The clear geometrical concept and large-format architectural-concrete surfaces offer the perfect setting for numerous works of art.
The extension with a usable area of approximately 18,700 m² houses numerous smaller rooms that are designed to offer the optimum conditions for the sometimes rotating exhibitions. “An important aspect of the planning and implementation in the entire building was the stipulation that all corners be sharp-edged,” explains Marti AG’s construction manager Franz Bütler. For this reason, the walls in the entire building were uniformly produced using the tried-and-tested wall formwork Mammut 350.
Due to the dimensional accuracy of the formwork and the high fresh-concrete pressure capacity of 100 kN/m², it was possible to pour concrete up to a height of 4 metres without taking the rate of placing into account, making things a lot easier for Marti’s building professionals, who always had to keep a close eye on the details during this project.
The slabs of the exhibition rooms were implemented using the standard slab formwork MevaDec. Due to the system’s arbitrary grid pattern, it was possible to freely select the beam orientation, thus reducing the number of compensations and making the work easier and quicker. In more spacious rooms the slabs were formed using the MevaFlex slab formwork supported by the flexible MEP shoring tower. Particular attention was also given to the atrium, which was constructed over five concreting cycles. The oval recess in the building's ceiling was planned in three dimensions by the MEVA engineers and created using special formwork.
High-quality concrete finishes
The modern museum building stands out due to the excellent architectural-concrete finish on all surfaces. Particularly high requirements applied in the meeting rooms, the shop, and the cafeteria. To fulfil these uniformly, MEVA organised its own training course on-site with regard to the preparation and maintenance of the alkus all-plastic facings used. As the facing can be repaired using the same material, scratches and holes can be plugged flawlessly; at the same time, the facing retains its fundamental properties, preventing discolouration and enabling smooth, uniform surfaces to be achieved. The environmentally friendly all-plastic facing with its long service life is fitted as standard in MEVA’s formwork systems. In many areas of the museum the joint pattern of the Mammut 350 wall formwork produced an extensive and wished-for pattern in the architectural concrete.
With great care
The formwork engineers’ masterpiece is, however, the new building’s central hall. With its high atrium and all-round galleries, it enables the visitors to easily get their bearings in the four-storey building. When standing in the hall, the concept of the new building as a light-flooded cuboid can be easily perceived. And the Mammut 350 joint pattern is also visible here. “Alongside the high architectural-concrete quality, that was an important requirement for this project,” says MEVA engineer Volker Götz, who supervised the project right from the start. “The architect drew inspiration from this pattern and specified it for the entire building,” explains Volker Götz. “This was a significant challenge in the large hall. Despite openings and flights of stairs in various locations, the joint pattern had to extend precisely and without offsets over the entire height.” Construction manager Franz Bütler adds: “The work required exact planning and had to be performed with great care, but together we managed to do a good job.”
The Mammut 350 wall formwork proved to be an absolute all-rounder in the entire hall. Thus, 3.50 m x 2.50 m panels were used horizontally in order to form the tall flights of stairs first of all and later on also the 2.50 m thick concrete beams under the roof of the large hall. The KLK 230 climbing scaffold was mounted on the wall to enable alignment of the formwork. Once again, the architectural-concrete quality was the top priority – and the uniform pattern even continued on the large concrete beams as if created by the Mammut 350 frame imprint.
The tried-and-tested MevaFlex slab formwork system was used to produce the slab at a height of 28 metres. Correspondingly dimensioned 3S shuttering panels were prepared in order to create the desired pattern as if it had been produced by the imprints left by Mammut 350 panels. The excellent results required were achieved using new shuttering panels. After first use, the panels were turned over so that the clean, unused side could be employed for the next cycle. It is also remarkable how regular the results are here. Not only does the pattern extend uniformly across the entire ceiling; the openings for the lamps are also always in the middle of the shuttering panel imprint.
In other areas, the precise planning groundwork is less conspicuous. However, especially for the 1-metre-thick outer walls, it was necessary to work meticulously, as misalignment of the formwork joints was only permitted in a tolerance range of 1 to 2 mm. That corresponds to about one quarter of the dimensional tolerance specified in the SIA standard 414/1. The reason for this is the natural stone façade that was precisely designed in the vicinity of the high window façades and columns. A greater deviation would have caused the concrete wall to protrude underneath the façade. The requirement to achieve a 3.50 x 2.50 m frame imprint also applied indoors. The schedule required rapid progress of the construction work. Using two Mammut 350 formwork sets, the 28-metre-high walls were formed in four 7-metre cycles. The KLK 230 climbing scaffold was used to erect and precisely align the formwork. Reinforced with Triplex heavy-duty props, the KLK 230 served as a scaffold for the alignment of the high formwork units.
With the newly built extension, Zurich now has a new architectural eye-catcher and an outstanding port of call for art connoisseurs. Franz Bütler, construction manager at Marti AG, expressed his satisfaction with the project: “The art museum was a very interesting construction site. Thanks to reliable partners such as MEVA, we have done a really good job here.”