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Timber gridshell slithers into place for Swatch

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Words:
Stephen Cousins

Shigeru Ban’s snaking timber gridshell for Swatch reflects the transparency, flexibility and fun of the watchmaker’s brand

Pritzker prize-winner Shigeru Ban is a master of experimentation with building materials and his latest project, the headquarters for Swiss watchmaker Swatch, in Biel, Switzerland, pushes the physical limits of glulam to create one of the world’s largest and most complex hybrid timber structures.

At 240m long, the cocoon-like double-curved gridshell facade incorporates 7,700 unique pieces of timber engineered to a precision of 0.1mm to fit perfectly onsite. 

Swatch challenged Shigeru Ban Architects (SBA) to develop a building that combines elements of its brand, such as transparency, movement, and unexpected and surprising details, with a sense of fun and playfulness. 

The 11,000m2 vaulted structure rises gently towards a glass entrance before bridging a street to meet a five-storey building, also designed by SBA and completed in 2017, which houses the Cité du Temps museum and exhibition centre and the Omega Factory. 

Carlo Giordanetti, creative director at Swatch, explains: ‘The intention was to create a dialogue and a juxtaposition between tradition – as represented by [parent company] Omega and the rational architecture of its new building (inspired by the firm’s historic HQ building) – and the dynamism and innovation of Swatch, where a completely new architectural gesture is accomplished.’

SBA’s idea for the timber structure has its roots in a previous collaboration with Frei Otto to create a cardboard and paper gridshell for the Japanese pavilion at the 2000 Hannover Expo. Engineered timber gridshells were explored on subsequent SBA projects, including Centre Pompidou Metz and Aspen Art Museum.

Visitors pass through the main entrance into a triple-height atrium lobby where three storeys of office space, a zigzagging white staircase and glass elevators are enclosed by the vortex-like wooden roof. The self-supporting gridshell spans the entire reinforced concrete frame used for the core and floor slabs.

At third floor level a  glass pedestrian bridge extends back through the entrance facade and over the street to connect to the Cité du Temps. At the ‘tail’ end of the building office floors step down towards an open plan area on the ground.

Timber was chosen for its sustainability and speed of construction, and because it can be processed flexibly and cut to very precise dimensions. 

  • Over 2,800 diamond-shaped elements – opaque, transparent or translucent – populate the gridshell.
    Over 2,800 diamond-shaped elements – opaque, transparent or translucent – populate the gridshell. Credit: Swatch
  • Over 2,800 diamond-shaped elements – opaque, transparent or translucent – populate the gridshell.
    Over 2,800 diamond-shaped elements – opaque, transparent or translucent – populate the gridshell. Credit: Swatch
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SBA has long advocated the use of wood as the only truly renewable construction resource. Giordanetti adds: ‘The carbon footprint of timber buildings is generally half that of concrete buildings and a third of steel. All the wood for the construction is Swiss spruce and despite the huge amount employed, the equivalent amount grows back in Switzerland in just two hours.’

The building’s facade lattice features 2,800 diamond-shaped elements, and glulam beam heights vary from 760mm to 925mm. The biggest beam cross section is 220mm by 925mm. 

Each element has a different cover – either opaque, transparent or translucent – to control levels of light and privacy inside. Some can be opened for smoke extraction, others are equipped with photovoltaic cells. 

SBA director Taro Okabe explains: ‘Each facade element comprises multiple components. For example, the transparent glass element is a closed cavity system that contains a shading device in a sealed environment between glass panels. The cavity space is slightly pressurized with dry air to avoid condensation and to protect the cavity from any dust entering.’

Translucent diamond shapes cover 40% of the facade and each one contains an ETFE cushion with a polycarbonate panel fitted inside. ETFE was chosen for its playful organic shape and, crucially, to reduce the overall weight of the gridshell structure. The cushions are lightly ventilated to put them under tension with the strength to withstand the weight of snow or ice.

Significant development work was needed for the ETFE to meet thermal and acoustic performance required on an office facade. Okabe comments: ‘The low mass of ETFE made acoustic insulation a challenge and thermal insulation was not enough so we added the polycarbonate layer inside the cushion to solve both issues.’ 

There were a few headaches during design due to the need for the gridshell structure to discreetly integrate a complex network of services, including electric cables and pipes for sprinklers, air, and heating and cooling water. Beams were CNC milled to create precise spaces for services and to enable intersecting beams to tightly interlock. 

  • Timber gridshell stretches over a highway to join up with Shigeru Ban’s 2017 museum and exhibition centre.
    Timber gridshell stretches over a highway to join up with Shigeru Ban’s 2017 museum and exhibition centre. Credit: Swatch
  • Swiss spruce used for the external structure counterpoints the high tech exteriors.
    Swiss spruce used for the external structure counterpoints the high tech exteriors. Credit: Swatch
  • The gridshell of the Swatch building complements the timber structure of Shigeru Ban’s 2017 Omega building on the opposite side of the road.
    The gridshell of the Swatch building complements the timber structure of Shigeru Ban’s 2017 Omega building on the opposite side of the road. Credit: Swatch
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Parametric design software was critical to co-ordinate the building services and define the precise shape and positioning of beams in the facade. All data related to the timber structure was input to a 3D parametric model, which generated timber elements semi-automatically to reduce manual design effort and duplication.

It is intended that the project’s environmental credentials will serve as a benchmark for future buildings. A total of 442 individually-manufactured curved solar PV elements were inserted into the coffered structure of the facade, enough to generate around 212.3 MWh per year,  equivalent to the average annual consumption of 61 Swiss households.

Autonomous operation of ventilation, cooling, heating and basic lighting in both the Swatch HQ and the Cité du Temps was achieved using a combination of solar panels and ground source heat pumps, which extract energy from nine underground wells, and two former oil tanks converted into water reservoirs. 

Energy demand is reduced using technologies such as radiative cooling and heating with activated ceiling panels and water pipes cast into the concrete slabs to provide draft-free air conditioning.  Charging stations, LED lighting and Velospot bicycle sharing add to the sustainable credentials.

As a showcase of low carbon construction and cutting edge design, the Swatch HQ is truly a building of its time. ‘Working with Shigeru Ban we have learned a huge amount about new solutions, materials and processes, and witnessed the architect’s fascination with Switzerland and the ability of Swiss manufacturing, ‘ says Giordanetti. ‘We’ve seen the Swatch brand philosophy coming to life in a completely unexpected dimension and in architecture, which is unprecedented for us as a brand.’ 

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