Hitting the roof: the technology behind the world’s newest stadia

First published in T3 magazine, July 2002

Both Korea and Japan are no doubt hoping that the world is admiring the work the two countries have put into their World Cup football stadia.

Korea pushed the boat out, spending 1.95 trillion won (£1.05 billion) on building all its ten stadia from scratch. But the Japanese city of Sapporo has come up with perhaps the most interesting technology.

The Sapporo Dome tackles the biggest problem associated with big football stadia. ‘In terms of pitches and roofs, the two always go together,’ says Simon Inglis, author of ‘Sightlines – a Stadium Odyssey’ (Yellow Jersey Press, £8).

Inglis explains that in the 1960s, artificial grass such as Astroturf allowed permanently-covered ‘dome’ stadia, the first being the Astrodome in Houston in Texas.

But artificial turf is unpopular with players; however, big stadia cause havoc with grass. Even if the pitch is open to the sky, stands roofed for spectators block out much of the light and breeze.

And the lucrative use of stadia for other events such as rock concerts poses further threats to the pitch, even when covered by specially-designed matting. It would be better if the grass could stay open to the elements – it is, after all, a field.

Sapporo solves this by parking its turf outside. For a match, the whole pitch is brought in through a 90-metre-wide opening, using hovercraft-style technology. This way, 40,000 spectators can sit inside, watching football played on a pitch grown to perfection in the elements.

In the UK, the Millennium Stadium in Cardiff already has a removable pitch, although this is accomplished through ‘palletisation’. The grass rests on 1.5 by 1.5 metre pallets, which can be removed for other events or maintenance.

Cardiff also has one of the world’s first retractable roofs – according to Inglis, the first was the Amsterdam Arena in the Netherlands – giving the grass a better chance in life.

But, unlike Sapporo’s site at the edge of the city, most UK football grounds are in urban areas. This is certainly true of Manchester City and Arsenal, two clubs due to move into new stadia. Both have chosen new sites, but are staying in the thick of the cities that have supported them for more than a century.

A moveable pitch would be expensive and space-consuming in a city. So both new grounds have focused on the shape of the roof.

The City of Manchester stadium in east Manchester will first be used as the main venue for the Commonwealth Games. It will then undergo a 10 month transformation. The athletics track will be covered with seating and another main stand will be built, boosting the capacity by 20,000 to 48,000. It should be ready for Manchester City for the start of the 2003 season. The changing rooms and players’ entrance have already been built, although they are below the athletics pitch level.

But much of the design thinking has gone into helping the grass grow. The stands behind the goals are lower, giving the roof a saddle shape. Dipesh Patel, lead architect for the project at Arup Associates, says this is partly as fans prefer to sit at the sides – but one of the low ends faces south, ensuring more sun reaches the pitch.

FA Cup and Premiership winning Arsenal are planning a 60,000-capacity stadium, but have yet to start construction. The club hopes to move during the 2004-5 season to Ashburton Grove, just a few hundred yards from its current home in Highbury, north London.

The club’s architects, HOK Sports, have already adopted similar ideas to Arup Associates regarding the roof. In Arsenal’s case, the roof will be a consistent height at the building’s edge. But it will slope towards the pitch, with the steepest slope on the south side of the ground. This will descend eight metres, allowing the grass to soak up the rays.

Then there’s the material used for the roof, and for the tops of the stands above the seating. ‘We’re looking at a polycarbonate, which isn’t the greatest for light transmission,’ says Christopher Lee, project associate at HOK Sports. Instead, the material will be good at letting through photosynthetically active radiation, the light that helps grass grow.

The Man City roof has large translucent areas, helping the pitch, but also meaning there is less of a contrast between sunlit and shadowed parts of the pitch. Patel says this is good for television pictures, and allows more light to reach the fans.

Grass needs air and water as well as light. Lee says Arsenal’s new ground is likely to follow West Ham in buying a ‘sub-air’ system. ‘There are kilometres of pipes under the pitch, which can push air or draw it back, controlling moisture. It also acts as an under-pitch heating system,’ he says.

The Man City stadium allows air to flow through giant louvers in the sides of the ground, although these will be closed during matches – ‘so if it rains, no-one gets wet,’ says Patel.

Furthermore, the entire stadium design was designed to ensure air moves smoothly. This involved acoustic modelling, so that music and announcements should be heard clearly, without the distortion of many stadia. But it should also minimise gusts and eddies that annoy players and fans, as well as once again helping the pitch.

Author Simon Inglis says that some of this may soon be unnecessary. Artificial weaves already help keep grass roots in place. And research has moved on a long way since Astroturf, towards surfaces that closely replicate grass. ‘It could be, in 10 years, that the only reason for [technology such as] retractable roofs will be for aesthetics and atmosphere,’ he says.

But until then, stadia will be built with the turf in mind. How much difference do these measures have on a pitch’s quality? ‘I think it will be a case of it surviving or not,’ says Arup Associates’ Patel. ‘We’ve taken all the precautions to make sure the grass will grow as it would in the open air.’

Arsenal’s new stadium will incorporate a variety of new technologies; the club is keen to create a stadium smart-card. This would act as your ticket, but also allow you buy drinks, get you access to car-parks or VIP rooms.

HOK Sports has been considering the environment for Arsenal. The stadium will need less heating and cooling than similar buildings, due to a sophisticated management system and use of white, exposed massed concrete, which absorbs heat during the day then radiates it at night. Other possibilities include solar panels to generate electricity.

One rejected idea, which HOK Sports used for the Sydney Olympics’ Stadium Australia, collects rainwater from the stadium roof, and reuses it for the pitch and toilets. Unfortunately, using the water for the pitch requires a treatment plant, and there isn’t room. Instead, ‘we’re looking at the possibility of waterless urinals,’ says Christopher Lee of the firm.

The club is also considering seat-back screens, along the lines of those found in aeroplanes. Lee’s firm also worked on the Docklands Stadium in Melbourne in Australia, where 1,500 seats have screens. ‘They’re the first to sell,’ he says.

These could carry replays of action, interviews and allow you to order food and drink. But author Simon Inglis is dismissive. ‘My personal view is that it’s toys for the boys, and people won’t be interested,’ he says. ‘Screens on the back of the seat – call me an old-fashioned fuddy-duddy, but I think it’s all nonsense.’

The latest mobile phones could be an alternative to seat-back screens, according to Mark Curtis, director of new media firm Fjord. The firm has been discussing ideas with HOK Sports, although Curtis won’t say if these apply to Arsenal.

But Curtis thinks fans want interactivity, rather than broadcasts. ‘We’re thinking about how technology can change the relationship between spectators and sport,’ he says.

Fjord set up a TV series called You’re the Manager, under which Conference League club Stevenage Borough would be ‘managed’ by Channel Four viewers, voting through mobile phones for team changes.

The league authorities pulled the plug a fortnight before it started, but Fjord has got agreement in another European country to go ahead. However, Curtis says his firm is also looking at how fans in the stands could interact with those watching at home.

This seems wise. Arsine Wenger seems unlikely to start asking the fans whether Fredrik Ljungberg should play. But maybe they could chose the colour of his next hair-dye?

Copyright SA Mathieson 2002