British Pavilion by Heatherwick Studio, Shanghai, China

By Will Hunter

With the 1851 Great Exhibition staged in London’s Crystal Palace, the British like to view themselves as the originators of the grand exposition

And for the UK’s presence at the forthcoming Expo 2010 Shanghai - the largest event of its kind yet, with 70 million visitors expected between 1 May and 31 October - there has evidently been pressure to live up to this 250-year-old reputation. As Heatherwick Studio’s Katerina Dionysopoulou explains: ‘The brief from the Foreign & Commonwealth Office was very simple: be in the top five.’

Competing with over 200 national counterparts, this was no small challenge. However, Heatherwick’s simple yet ingenious competition-winning proposal for the UK pavilion looks in with a chance. The designers have given over most of the 6,000m² site to a folded landscape, creating the pavilion as an axial focal point. Crucially, instead of an exhibition that bombards visitors with information about the UK, the scheme integrates structure and content.

Externally, the pavilion is a hairy, somewhat amorphous object, with over 60,000 acrylic rods piercing a 15 x 15 x 10m box. Those familiar with Heatherwick’s work will trace this silhouette to an earlier project, Sitooterie II at Barnards Farms in Essex (AR January 2004) in which the designer punctured a cube with 5,000 aluminium tubes. At Shanghai, this precedent is vastly scaled up and the form exponentially more mesmerising, as the rods quiver in the breeze issuing from the nearby river.

The Expo’s theme is Better City, Better Life and the UK explores this through the relationship between nature and cities.

Working with the Royal Botanic Gardens at Kew, the internal space has been conceived as a ‘seed cathedral’.

Over 250,000 different seeds, all arranged randomly, are cast into the ends of the rods. The acrylic acts like fibre-optic filaments, so in the daytime, the tiny exhibits are naturally illuminated. At night, LEDs take over, backlighting the seeds and making the pavilion glow from the outside.

‘Very early on we decided that we didn’t want to do anything advanced technologically, because we felt China could do that better than anybody, so we wanted to do something low-tech,’ says Dionysopoulou, who has worked on the project from competition stage and is now seeing it through to completion. ‘Inside it creates an amazing experience: you can see where the sun is because those rods are glowing more.’

Visitors arrive at the site through a corner entrance, and can either filter into the park and simply look at the pavilion, or enter it by ascending a ramp. From the park, there is a moat-like pool that prevents people walking up to the pavilion and touching it. At the top, where a bridge crosses to the interior, the threshold is screened with a curtain to protect the dramatically-lit experience.

The internal floor area is 100m², which allows 100 visitors at any one time. The floor is a steel structure finished with a concrete screed; it has a glass balustrade and a void in the middle, so you can look down onto the seeds. Looking up, the rods are about 5m above your head, so you can only really perceive the seeds properly at the ends closer to eye level. A guide will give a short talk, pointing out interesting examples.

The structure is 20m high - the maximum height for everybody (except the Chinese, whose pavilion reaches 67m). Heatherwick created a gradual 1m indentation in the flat site, into which the British pavilion was sunk. Excavated earth has been stored under the ramp so the plot can easily be returned to how it was found (another condition of the brief). The pavilion sits on a removable cast in-situ concrete raft foundation.

The box is a timber sandwich structure: plywood on the inside and outside, set 900mm apart, supported with laminated veneer lumber (LVL), creating a space-frame structure in between. So as not to interrupt the dispersal of rods, which are 40mm in section and centred 100mm apart, the LVL couldn’t be wider than 40mm. Five sides of the box are all plywood, except the bottom plane, which also contains steel to bear the weight.

The holes for the rods have been CNC-routed in the exact required position and angle. All the rods are 7.5m in length and extend about 5m outside the building.

Because it’s not an exact cube, you end up with an unexpected silhouette inside.

‘If it were 15 x 15 x 15m, you would get the same shape inside as out,’ explains Dionysopoulou, ‘but because the height is 10m -and the rods are all facing a sort of sphere in the middle - you create a much more interesting interior volume.’

Two thirds of the rod’s length is encased in aluminium. Externally, 1.5m of acrylic remains exposed, and this material shift is obvious, with the clear acrylic appearing as a glowing halo around the metallic silhouette. There are a series of what appear as red dots where the aluminium meets the acrylic, caused by a red plastic extrusion that lets the two materials move without scratching the acrylic. The aluminium stops the acrylic from drooping or snapping off. ‘We did a lot of tests about wind-loading, and typhoon and earthquake conditions,’ says Dionysopoulou. In the event of such a disaster the rods wouldn’t snap, though they might deform.

The acrylic rods were made in two sections: for the most part they were extruded, but because some of the seeds were larger than the 40 x 40mm section, the internal ends were all cast separately and glued on. The distance between the tip of the seed to the structure ranged from 350mm to 1.3m, and an accurate 3D computer model was used on site to check the rods were positioned correctly.

More than 75 per cent of the material was sourced from within a 300km radius of Shanghai. The seeds came from one of Kew’s local partners in China, and all components were prefabricated off-site, in factories around the city.