Steel and curved glass house spiral grass-roofed museum

As we count down the days and months to a return to normal life unimpeded by coronavirus, it seems fitting that a museum dedicated to time and watchmaking is one of the most talked about architectural projects of the year.

The Audemars Piguet Museum coils up from the floor of the idyllic Joux Valley in Switzerland in an elegant spiral inspired by tiny watch springs. 

Bjarke Ingels Group’s kaleidoscopic design is an extension to the founder’s original home where the luxury watch brand was established in 1875. 

Continuous floor-to-ceiling glazing offers stunning views of the landscape and provides the sole structural support for a 470-tonne green roof that twists like apple peel from the hillside.

The Danish studio won a competition to design the project back in 2014 and developed it in collaboration with interior designer/ scenographer Atelier Brückner, structural and facade engineer Lüchinger+Meyer, and landscape architect Muller Illien. Swiss practice CCHE was the local architect, which also refurbished the historic building it links into.

Visitors to the museum follow a spiral route through the 2,500m² interior, channelled by internal glass walls along a path from street level down to the centre of the exhibition, before reversing direction to walk up and out again. 

On display are some 300 heritage timepieces, ranging from jewelled pocket watches, to complex astronomical and chronograph devices, each displayed in a futuristic golden dome. At the heart of the spiral is the ‘Universelle’, produced in 1899, the most complicated watch Audemars Piguet ever created, with 1,168 individual parts. 

On one side of the museum, visitors can observe watchmakers at work behind a glass wall inside the Grandes Complications Atelier. 

Finely tuned

Mainsprings and hairsprings provide the energy to turn gears and regulate movement in watches and must retain their physical characteristics in all temperatures to maintain accuracy. In a similar vein, the structure of the museum is finely tuned to enable the frame­less curved glass walls to provide full support to the unitised steel roof – there are no columns or masonry walls – and withstand high winds and extreme cold, down to -20^oC in winter.

Other recent buildings have relied on load-bearing glass for structure, such as Apple’s Steve Jobs Theatre in California, but the approach taken here is exceptional and innovative. 

Matt Oravec, project architect at BIG, explains: ‘Previous buildings are either more repetitive or located in more forgiving climates. The Apple auditorium has a repetitive facade, every glass panel is the same, but every panel here is different, the roof rises and falls, so each panel had to be cut individually before it was bent. We are in an earthquake zone and a high snow load zone, so the roof needs to take up to 2m of snow without a problem. Everything has to brace together to make the structure work.’ 

Curved glass is normally tempered by bending it back and forth in the kiln, but this can create optical issues such as a zebra-like striping. BIG made the decision to use float glass, which though weaker, would provide strength and rigidity when laminated together in several layers. 

The exterior glass wall and the two internal partitions feature three layers of laminated glass; panels on the exterior incorporate two air gaps filled with argon. Each panel is about 2.4m wide and heights range from 2.4 to 6m.

Philippe Willareth, project manager at  Lüchinger+Meyer tells RIBAJ: ‘There’s a lot of redundancy in the design because safety was such a vital consideration. The glass at the centre of the plan is thicker to increase support for more concentrated loads created by the large 12m span.’

The roof of the museum appears to float over the curved glass and comprises two circular metal plates inclined in opposite directions to form clerestory windows towards the centre that bring in natural light.

Code violation

That the roof exists at all is remarkable given that it violated strict regional building codes. Switzerland normally favours a traditional angled pitch roof, but the fact the planning system is weighted in favour of local decision making worked to BIG’s advantage explains Oravec– because residents in the town were ‘thrilled with the project and super optimistic, nobody voiced any dissent’.

A regional custom of driving timber stakes into the proposed construction site to delineate the high points of the roof also helped assuage peoples’ fears, when they saw that the building would be partially excavated into the earth.

The all-glass structure posed technical challenges when designing the steel roof, most notably the fact that mechanical and electrical services were unable to cross the glazing and so had to follow the line of the double spiral. In addition, the absence of regular walls meant electrical conduits had to be incorporated into the ceiling void. Workshops had to be dust free and pressurized slightly, which required ventilation to come from above to prevent air currents. 

‘BIG took over a lot of the planning and ­design of the mechanical systems to get the thickness of the roof down to a minimum. There’s not a square inch to spare up there,’ says Oravec.

Provision for a gravity-based drainage system added further complications. The roof slopes inwards towards the middle so a ‘slight massaging of the roof form’ was required to run two drainage pipes through the inside of the roof from the facade edge. 

The roof was manufactured off-site by subcontractor Frener & Reifer (which also did the facade) in wedge-shaped sections dimensioned to match the 2.4m width of the glazing panels and to fit on the back of a lorry.

Other materials were considered for the roof deck instead of steel, including lightweight timber and concrete, to create downward pressure on the glass and prevent uplift. However, steel won out for its relative lightness, ability to achieve long spans and compact section. 

Back-to-front

An unconventional construction process saw the roof erected before the facade. The pie-shaped wedges were erected on temporary shoring and bolted together, before the glass panels were inserted into slots in the concrete foundation and the entire roof lowered onto the glass. 

‘This approach was more forgiving because the glass can withstand significant movement without any cracking or impact problems,’ says Oravec.

‘We had to get everything right regarding the loading,’ adds Willareth. ‘The steel roof had to create an even load distribution onto the glass – the average area will have around 500 kilos of snow sitting on top in the winter months.’

A carpet of regional grasses covers the roof in spring to help control the building’s temperature and absorb rain.

The building’s external glazing is treated to reduce solar gain, but a physical shading element was required to create a comfortable environment for employees working on intricate timepieces.

A brass-and-steel mesh sunscreen was developed to wrap around the exterior, suspended from the fascia. It changes in height and thickness depending on the direction of the sun and its location on the building.  

Welding in lead is banned in Switzerland, so the German fabricator had to come up with a new approach that used a lead-free brass alloy as the welding material.

The Audemars Piguet Museum was due to open to visitors this summer, but like many public buildings at present, the opening had to be pushed back until the end of the year. A museum dedicated to timepieces, even if it is designed by one of the world’s most  prestigious architects, would need to become a time machine to avoid the effects of a rampaging virus.