Une œuvre d’art en béton de parement

The goal

Create an openwork concrete sculpture with a high-quality finish According to the plans of star architect David Chipperfield, the new extension of the Kunsthaus in Zurich was to take the form of a cube bathed in natural light. To materialize this vision, a number of technical requirements had to be respected, such as a clean edge finish in all angles, high-quality architectural facings and a homogeneous materialization of the joint of the formwork at the level of the walls and the floors.

The project

Summary :
With a particularly detailed preliminary study, MEVA and the construction company in charge of the work, which was to create an architectural jewel in exposed concrete, had to deal with a number of technical requirements.

Challenge :
The complex geometry of the building and the execution of the works with respect for detail led to aesthetic and technical constraints, difficulties that required a great deal of creativity, know-how and dexterity.

Solution

1. 1. Attention to detail
       
      a) Homogeneous materialization of formwork joints
      During the planning and execution of the work, it was necessary to master an essential aspect: all the corners of the building had to be finished with a clean edge finish. In addition, the layout of the formwork joints was defined by the architect for the entire building. The implementation of these requirements was difficult at the level of the central hall. Despite the openings and flights of stairs scattered here and there, the joints had to respect the layout exactly, without misalignment, over the entire height – even at the level of the imposing sub-beams. The work therefore had to be well planned, then carried out by scrupulously respecting the layout plans for the formwork.

      It is for this reason that all the walls of the building were made with Mammut 350 wall formwork, forms that have already proven their worth. Thanks to the precision of execution, the materialization of the joints was in accordance with the expectations of the architect. The slab, sub-beams included, was made with MevaFlex formwork .

      b) The new formwork panels give excellent results
      To draw the desired pattern from the imprints left by the large panels of the Mammut 350 formwork , three-glued panels were prepared and cut to the right size. The use of new skins made it possible to achieve the desired aesthetic quality. After the first casting, the skins were simply turned over, so that the clean, still unused side of the skin could be used for the next rotation.

      Without forgetting the regularity of execution which is also quite remarkable, because, in addition to the homogeneous materialization of the joints over the entire ceiling, it was also necessary to center the reservations intended for the lamps on the imprint of the formwork panels.
       
      

   2. Quality facings thanks to alkus formwork skins
      To meet the requirements of the project, all the concrete facings had to be of very high quality. In the meeting rooms, the shop and the cafeteria, the aesthetic criteria were particularly high. To guarantee the homogeneity of the facings, MEVA organized on-site training to prepare and maintain the alkus polypropylene skins implemented on site.

      These skins, which can be repaired identically (holes and scratches can be closed with the original material), retain their essential properties, which makes it possible to avoid discoloration and to obtain flat and homogeneous surfaces. All MEVA formwork systems are equipped with this polypropylene skin, an environmentally friendly skin with a long service life.
      

   3. Exceptional precision
      In other places, the precision of the plans made upstream is barely perceptible. The realization of the exterior wall, which is one meter thick, required a lot of meticulousness, because the tolerances at the junctions of the formwork were only 1-2 mm, which corresponds to about a quarter of the Swiss standard SIA 414 /1 (relating to dimensional tolerances). This is due in particular to the natural stone facade, which at the level of the high glass faces and the posts has been the subject of meticulous study. With larger gaps, the concrete veil under the facade would have formed a protrusion.

      The 28m high sails were cast, in four 7m high rotations, using two sets of Mammut 350 formwork. The placement and exact alignment of the formwork was carried out using the KLK 230 climbing bracket . Supported with Triplex oblique props, the KLK 230 bracket served as scaffolding to align the formwork trains.

      

   4. Easy to use despite the constraints of the project
       
      a) The high resistance of the formwork to the pressure of fresh concrete facilitates and speeds up the work
      Thanks to the high dimensional stability of the formwork, with a resistance of 100 kN/m² to the pressure of fresh concrete, it was possible to cast sails 4m high without paying attention to the filling speed – a little respite for the Marti construction professionals who had to think of everything, without forgetting the smallest detail.

      b) Adaptability at the service of efficiency
      Mammut 350 wall formworkproved to be very versatile, especially during the realization of the hall. The 3.50 mx 2.50 m panels were first implemented in a lying position to make the large flights of stairs, panels which were then used to form the 2.50 m sub-beams of thickness located under the roof of the great hall. The KLK 230 climbing platform was attached to the wall to align the formwork.

      c) Time savings thanks to modular slab formwork
      The ceilings of the showrooms were executed with the modular slab formwork MevaDec. This frameless system reduces compensations, as it allows you to freely choose the direction of laying the beams, which also facilitates and speeds up the work. In the larger rooms, the slabs were made with the MevaFlex slab formwork and propped using the MEP modular shoring tower . Particular attention was also paid to the realization of the atrium, which took place in five rotations.

      
      

The result

Thanks to this extension, the city of Zurich now has an architectural attraction, an essential site for art lovers. La Marti AG and MEVA jointly mastered the technical difficulties of the project and created a structure that looks like a concrete sculpture.

Featured Products

• Mammut 350 Wall formwork 
• MevaDec Slab formwork 
• MevaFlex Slab formwork 
• MEP Shoring Tower 
• Triplex Props 
• KLK Climbing systems 

Construction company :
Marti AG Zurich

Project :
Extension of the Kunsthaus Zurich

Site location :
Zurich, Switzerland

Client :
Zurich, Building Office

Formwork planning :
MEVA Schalungs-Systeme AG, Seon