Extension of the Bündner Kunstmuseum, Chur, Switzerland

An imposing grey cube rises above the square on Bahnhofstrasse in Chur. Its clean lines and substantial volume contrast sharply with the neighbouring Villa Planta, the historic home of the Bündner Kunstmuseum. Yet the two buildings do not compete with one another. Instead, architectural practice Barozzi Veiga has given the extension a distinct architectural identity while establishing a visual connection with the existing building. «We wanted an extension with its own identity and character,« explains Alberto Veiga, describing the architects' approach.

Villa Planta was built between 1874 and 1876 to designs by architect Johannes Ludwig for cotton industrialist Jacques Ambrosius von Planta. Inspired by Venetian Palladian architecture and Oriental architectural styles, the villa features elaborate façade ornamentation, sphinx-like sculptures and a domed atrium. When an international competition was launched in 2011 to design a new museum extension, Fabrizio Barozzi and Alberto Veiga won with a proposal that draws on the historic architecture without attempting to imitate it.

A detailed study of Villa Planta became the starting point for the design of the extension. »It is a very interesting interpretation of a Palladian villa, full of ornamentation inside. The idea of ornamentation was omnipresent in Chur,« explains Veiga. Together with Barozzi, he sought an architectural element that would give the understated building its own identity while responding to its historic surroundings. 

The idea of ornamentation was about adding the defining detail to the design.

While the extension's basic cubic form was established early in the design process, the concept for its façade emerged at a later stage. »We were looking for something that would enrich the design while remaining contemporary and modern,« says Veiga.

The result is a relief-like concrete façade composed of numerous repeating square coffered elements. Only on closer inspection does the complexity of this seemingly simple geometry become apparent: each element consists of three nested squares set at different depths. The square is a recurring feature not only of the façade but also of the building's overall form and the geometry of its interior spaces.

The three-dimensional relief gives the substantial façade a varied appearance, while the geometric ornament establishes a visual connection with the historic villa, whose architecture is equally defined by decorative details. »Without the ornamentation, the volume would have a completely different effect,« Veiga emphasises.

Realising the intricate façade geometry required close collaboration between the architects, Zurich-based engineering firm Feroplan Engineering, precast concrete manufacturer Sulser AG and RECKLI. Five different façade designs were tested before the final solution was selected. The process from the initial concept to the completed façade took 36 months.

RECKLI first became involved in January 2014 at the Swissbau construction trade fair. There, an engineer from Feroplan approached RECKLI representative Elmar Pallasch to ask whether the proposed façade elements could be produced using elastic formliners.

Having already collaborated with RECKLI on several projects, Sulser AG had extensive experience in manufacturing custom polyurethane moulds. The decision was therefore made to produce the formliners directly in Switzerland. RECKLI supplied the required PUR Elastomer, while Sulser manufactured the moulds in-house.

Following initial plaster and wooden models, Sulser produced the master pattern for the façade detail in its own joinery workshop. This formed the basis for the moulds used to cast the precast concrete elements. From May 2016 onwards, RECKLI supplied the required material to the Swiss precast manufacturer in several batches.

One of the main technical challenges was reproducing the three nested squares with absolute precision. To achieve the intended relief effect, the formliners needed to be almost eight centimetres deep. Wooden reinforcements were cast into the polyurethane to ensure that the complex geometry could be reproduced accurately.

Dimensional accuracy was equally important. Each mould had to reproduce the elements precisely to ensure consistent spacing and alignment across the finished concrete façade. The completed precast elements were delivered and installed on site in summer 2016.

The completed façade reveals different qualities depending on the light and weather conditions. As the sun moves across the sky, the stepped squares cast changing shadows that accentuate the depth of the relief. Rain and natural weathering will also leave different traces on each side of the building, gradually altering its appearance over time.

For Barozzi Veiga, these changes are not an unwanted consequence of ageing but an integral part of the architectural concept. Light and water allow visitors and passers-by to experience the building in different ways, while each façade will gradually develop its own character.

Veiga says:

Time changes all our lives, and in the same way, it changes a building.

Rather than viewing ageing as an inevitable process that begins once construction is complete, the architects consider it an essential aspect of their design.