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Fostering invention at a Swiss ski resort

TIMBER IN ARCHITECTURE

At glitzy St Moritz, Foster and Partners has mixed parametric design with traditional technology to produce a curvaceous apartment building

If your idea of buildings in ski resorts is of Alpine chalets or of rather blocky concrete buildings that make up in internal luxury for their unprepossessing exteriors, you'll be in for a surprise next time you go to glitzy St Moritz in Switzerland. It is there that Foster and Partners has designed the Chesa Futura apartment building, which combines an unusual rounded form that could only have been designed with the latest in computer technology, with traditional construction techniques applied to materials sourced locally.

Although timber is not the material one immediately associates with the practice, it has used it before, notably for a house in Corsica completed in 1993 for the then-deputy mayor of Nimes, Jean Bousquet.

But it is on the more familiar steel and glass buildings that Foster has developed its use of parametric modelling, a 3D modelling process that allows the designer to specify or capture the geometric relationship between design features. The parameters that control those relationships can be modified to generate new versions of the design almost instantaneously. Fosters has now applied the lesson learned on the development of some of its more curvaceous buildings, such as the Sage Music Centre in Gateshead, Swiss Re and City Hall in London, to a relatively modest apartment building in Switzerland's Engadin valley.

With these non-orthogonal buildings, it has striven to achieve the greatest efficiency of form and performance. Foster has written:

'The rapidity with which alterations can be made to a design generates a degree of creative freedom, allowing options to be worked up, assessed and improved upon in an organic fashion, providing important lessons along the way.'

This approach also gives more authority to the architect, allowing them to engage in a detailed dialogue with the engineers and cost consultants, and at the same time drawing the contractor and the construction process into relatively early-stage discussions. This mathematical modelling approach also has implications for manufacture, helping to solve the problem of how to make up a complex, curved form from simple and, ideally, flat elements.

Although Swiss Re, which is seen by anybody who lives in or visits London, will remain the most visible representation of this approach, Chesa Futura is at least as interesting an example, because it demonstrates that the approach does not have to be restricted to enormous buildings or to the traditional high-tech palette of materials.

Chesa Futura is a flexible building that can be subdivided into between six and 12 apartments. These apartments make the most of their orientation in terms both of views and environmental performance, as well as exploiting the envelope determined by the planning regulations. The slightly alien nature of the building is appropriate for St Moritz, a resort whose native population swells tenfold at the height of the skiing season, mostly with moneyed foreigners. For some it is the epitome of glamour, although the more cynical Rough Guide to Switzerland says that it 'sticks out like a sore thumb.

Seemingly plopped down unceremoniously amidst the quiet villages of the Engadin - although, of course, it was here long before they were, a spa as far back as the Bronze Age - St Moritz is a brassy, in-your-face reminder of the world beyond the high valley walls, the kind of place that gives money a bad name.'

Love it or hate it, you can't get away from the fact that St Moritz is densely built, and Foster's first concern with its apartment project was to create a building that could sit within the urban envelope rather than sprawling out into the surrounding countryside. It is lifted on eight pilotis. This classic Modernist move ensures that all the apartments have views, and is part of a Swiss tradition, protecting wooden buildings from prolonged contact with moisture from long-lying snow.

Planning requires that at no point should the building be more than 15.5m above the ground - a complex constraint, given the sloping nature of the site, and one that the curved form exploits better than a rectilinear building would have done. Similarly, the curves reduce the apparent bulk, which is important since, by effectively eliminating the first two floors, the architect was obliged to make the three floors of accommodation larger.

The frame of the accommodation consists of prefabricated glue-laminated beams, with a skin of plywood sheets. The malleability of wood makes it easier to achieve the building's doubly curved shape. Environmentally, it has good credentials, since timber is an entirely renewable material and, by sourcing the material locally, the architect was able to minimise the transport costs and fuel consumption. Compared to steel or concrete, the elements are relatively small and light, making it easier to bring them in on narrow mountain roads. Two concrete cores, housing the lift shafts and stairwells, provide further stability.

This superstructure sits on a lightweight steel structure, supported on the eight steel sloping pilotis. The foundations consist of a sunken concrete box, which houses the plant rooms, car parking and storage spaces.Wherever possible, the architect has used prefabrication, since the winter holiday season restricted construction to eight months a year.

By wrapping the windows around this curved form, the architect was also able to take maximum advantage of the views of the town and the lake. The building sits to the north of the town, so that balconies are on the southern side, exploiting the view and letting in sunlight. On the north, which faces the mountains and the bleakest weather, the windows are small openings in the walls, which have a 40cm-wide cavity containing insulation. Picking up a traditional Engadin design detail, the window surrounds are chamfered to allow in the maximum amount of light.

The building is clad in larch shingles, which will weather and change colour with time. A traditional material, they will help the building blend in with its surroundings.

A local family that has practised the craft for generations cut the shingles by hand.

By cutting the timber both laterally and radially, it made the most efficient use of the material, so that only 80 trees were needed to provide the required 240m 3of shingles. The two different cuts combine the water-draining characteristics of one cut with the structural strength of the other, and provide a variegated visual appearance.

By using trees at the same altitude as the finished building, and cutting them in the winter when the wood is dry and contains no sap, it could be guaranteed that the shingles would not shrink. They were applied by hand, using nails, and have a life expectancy of 80 years. The roof is made from copper, another traditional material locally. It is malleable enough to be formed on site, even in low winter temperatures.

The 10 apartments have their bedrooms against the highly insulated northern facade, and living areas to the south to benefit from the sunlight and the views. Bathrooms and kitchens are in the middle section of the building where there is less daylight.

Having a building with walls that curve in two directions is a challenge for the interior design. There is no storage against the external walls, only on the internal partitions, which radiate from the cores.

For the occupants (one should not say residents, since they are unlikely to be there all year round) of these apartments the experience will doubtless be delightful. There is no denying that the architect has also taken the environmental credentials seriously.

It remains to be seen how much influence this project will have on other developments in ski resorts.

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