Peter Zumthor’s Serpentine Gallery Pavilion blacks out the noise and smells of London to lead the visitor to a tranquil garden of light.

Architect Atelier Peter Zumthor & Partners
Location Kensington Gardens, London WC2
Completion date June 27, 2011

Peeping through the gaps in the hoardings, designed to give only oblique views of the 11th Serpentine Pavilion as it rapidly takes shape, the first impression is an intense smell of wood.
The black pavilion is entirely constructed from timber – a simple prefabricated system clad in sheets of plywood.

But once the pavilion opens to the public on July 1, this aroma will no doubt be replaced by an intoxicating scent of flowers wafting from a sunken internal garden – the main focus of the temporary structure.

This year’s pavilion has been designed by Swiss architect Peter Zumthor and is the first in the series to incorporate a garden. The idea sprang from Zumthor’s concept of the “hortus conclusus” or enclosed garden – a place of sanctuary and contemplation.

The 5.3m-tall pavilion is 12m wide x 33m long. A passageway resembling a cloister will encircle the garden, separating the external wall from the inner wall. Staggered doorways on the long sides of the structure provide access to the garden, with the move from one to the other designed to create a dramatic contrast as visitors emerge from an intensely black interior into a colourful, light-filled space.

“The building acts as a stage, a backdrop for the interior garden of flowers and light,” says Zumthor. “Through blackness and shadow one enters the building from the lawn and begins the transition into the garden, a place abstracted from the world of noise and traffic and the smells of London – an interior space within which to sit, to walk, to observe the flowers. This experience will be intense and memorable, as will the materials themselves – full of memory and time.”

Zumthor has collaborated with Dutch garden designer Piet Oudolf on the design of the 252sq m garden. This will be densely planted with over 30 varieties of shrubs, flowers and grasses, each chosen for its form, texture and colour to emphasise the plants’ natural architecture and to evolve as the season changes.

The pavilion will be Zumthor’s first completed building in the UK. His other British project, a holiday home in Devon for Alain de Botton’s Living Architecture initiative, is set to complete at the end of next year.

Timber structure

Zumthor's Serpentine pavilion

Pavilion early on in construction process, showing simple pine structural system.

”Peter [Zumthor] chose timber because he wanted a simple, honest material that reflected the temporality of the pavilions,” says project architect Anna Page. “He wanted something appropriate to the site and programme that would still hold a poetic resonance, and timber did all this.”

The result is a simple prefabricated structural system, made of pine and standard 8ft x 4ft (2.4 x 1.2m) panels of spruce plywood for the skin, which is cheap and easy to erect on site.
The primary structure and frame use a prefabricated roof truss construction nailed together with the frames positioned at 600mm centres. The 18mm-thick plywood skin is then nailed to the frame on site. The timber structure rests on a concrete foundation of two simple strip footings, which run continuously around the building’s perimeter.

Zumthor wanted the pavilion to create a space with an overhanging roof above a timber bench that would encircle the garden.

This roof overhang and resulting frame geometry presented a technical challenge to the engineers, as it makes an unstable structure that wants to fall forwards towards the garden.

To overcome this, Ted Featonby, project manager with contractor Stage One, devised a 600mm x 600mm timber plate, which forms a stiff connection between the floor and the primary timber upright, making an inverted T shape. This “Featonby plate” both stabilises the building and forms the profile for the bench.

Both inside and out the corners have a curved profile – an effect which is achieved externally by routing and internally through the application of timber beads.

Timber treatment

Zumthor's Serpentine pavilion

Hessian scrim without a coating of Idenden (left) and with a layer of Idenden applied (right).

Zumthor desired a depth of blackness to the timber that could not have been achieved simply by painting it.

“Peter wanted something really black, with a depth and shadow to it, rather than the flat black that paint would achieve,” says project architect Anna Page. “He also wanted a finish with a memory to it so that when people looked at it, it would be familiar in some way”.

Finding the right solution took time. The first serious contender was black roofing felt, but this wasn’t durable enough to be used as a flooring material, nor sufficiently fire-proof to be an internal wall lining. Other solutions considered were charring the timber and using black rubber, but these too failed to achieve the depth of black that Zumthor wanted.

In the end, a combination of black Idenden – a polymer emulsion often used as a vapour barrier coating for pipework – and rolls of hessian scrim have been used for the entire pavilion apart from the bench.

First a layer of Idenden is painted over the timber, then a layer of the hessian scrim is stuck over it, starting from the pavilion’s base, and rolled over the roof and under the overhang. This is followed by several more layers of Idenden until the dark black is achieved.

In contrast to the blackness of the pavilion, the timber bench which encircles the garden will be stained a rich Prussian blue.

The top of the bench will be fitted with solid 400mm x 60mm pieces of pine finished with rounded edges. The timber will be secured underneath with hidden mechanical fixings and will project forward 100mm. It is then finished with two stains which react on the Swiss Pine to create a luminous Prussian blue.