Cardboard isn't just for Blue Peter. Buro Happold thinks it's the green building material of the future, and is testing its theory on an Essex school. Thomas Lane finds out how to build with giant toilet rolls – and asks what happens if it rains
It may sound like an episode of Blue Peter, but, in Essex, a team led by engineer Buro Happold is making a building out of cardboard.

The structure, an after-school club for Westborough Primary School in Westcliff-on-Sea will be Europe's first permanent cardboard building when it is completed at the end of the month.

It isn't Buro Happold's first work in cardboard. The firm, which has spent the past 20 months on the Westborough project, used cardboard panels and tubes in its design for the Local Zone at the Millennium Dome. Andrew Cripps, Buro Happold's research co-ordinator, believes that cardboard is the green material of the future.

"It's made from waste paper, it's cheap and very green," he enthuses.

Despite cardboard's green credentials and Cripps' obvious enthusiasm, the research team was faced with a serious challenge: to create an easily manufactured cardboard product with good structural and thermal performance, but that was also easy to build with. "Designing a permanent external wall was a real challenge," says Cripps. The school had to last 20 years and the cardboard also had to be fully recyclable to conform with the project's green aims. Then there was the matter of convincing planners and the local community that the project was viable and serious.

Cardboard is used for two main components in the school. Cardboard tubes, effectively giant toilet rolls, support a roof truss running the entire length of the building; they also support the lintels above the window openings. The walls and roof are clad in cardboard panels that have both structural and insulating properties.

The product design was a team effort, involving the expertise of architect Cottrell & Vermeulen, Buro Happold, contractor Franklin Building and the cardboard manufacturers. One of the main difficulties was dealing with fire and water resistance and making sure the building wouldn't fall down or blow away. Safety was obviously a major priority. As Cripps says: "If we were unsure about anything, we always had to err on the side of caution." To verify its practicality, a series of panels were constructed and tested for fire resistance, strength and insulation. These tests showed that exposed parts of the cardboard needed to be treated with a fire retardant. However, this treatment was kept to a minimum to reduce the project's environmental impact.

The research team was also faced with what Cripps terms the "moisture issue". Cardboard loses its strength if it is not kept dry, a problem compounded by the fact that it is hydroscopic, meaning that it absorbs moisture from the air.

To stop the cardboard acting like a sponge, a chemical was added to the basic pulp to make it more water-resistant. Making the material fully water-repellent would have prevented it from being recyclable, so the panels also incorporate a vapour barrier on the inside.

A breathable membrane on the outside provides additional protection.

Another problem with cardboard is its tendency to deform under a sustained load over time – a process known as "creep". The research team found that this can be eliminated if the cardboard is designed to carry only one-tenth of its maximum possible load.

Wear and tear from scuffing could cause the cardboard to deteriorate on the exterior of the school. To get around this, the exterior was clad in Eternit Duraco wall board (Workshop, page 88) fixed onto battens attached to the cardboard walls. This looks similar to cardboard, so it is protected with a clear lacquer. Internally, the walls are covered with Sundeala pinboard, made using recycled paper. The ceilings will be left unpainted to demonstrate the building's origins.

Getting cardboard to perform as a building material was one thing, but getting it past conservative planners and building control officers was another. Initially, the planners said the building should be constructed from brick, but they relented once the details of the scheme were explained. The local community was divided over the school, but eventually the project got the go-ahead – with the curious proviso that frosted glass be used in the exterior doors.

With the building material developed, planning permission obtained and local residents convinced, work could start on construction. Franklin Building was selected as contractor because it was enthusiastic about cardboard's possibilities as a building material. Also, it had worked with project architect Cottrell & Vermeulen on previous schemes at the school.

The most challenging part of the project for the contractor has been the complex detailing. Tony Vincent, contracts director at Franklin, sums it up as "a complex design with simple fixing". The school has straight and folded walls, while the roof has a range of design details, including a dormer, a mansard and a number of eaves details. By comparison, the cardboard construction was straightforward, not least because the lightweight panels were so easy to handle.

Vincent adds that it was more difficult to convince subcontractors of the project's merits. But, after a morning's work on the building, they saw that traditional jointing techniques were used and were converted.

Construction work started in January. Building the external envelope of the school will take about seven weeks, but Greg Franklin, managing director of Franklin, thinks that on future projects, this amount of time would be enough to complete the whole building, including the interior fit-out. This project has taken slightly longer because of delays in getting the panels delivered and, of course, because it is so unusual.

Part-funded (about 40%) by the DETR as a Partners in Innovation research project, the scheme has a projected budget of £180,000. The rest of the funding has been contributed by the project team and principal suppliers, a tribute to their enthusiasm for the project.

Cripps has yet to carry out a detailed analysis of the costs involved, and the environmental benefits of using cardboard compared with other materials. But cardboard is undoubtedly cheap, and he believes that it has a definite future in construction. He even goes so far as to say that it would be possible to build a 25-storey building from cardboard, but quickly adds that it would be mad to do so.

Cripps ultimately hopes that a cost-effective system can be developed so people can have a very green building they might not otherwise be able to afford. Who could argue with that? A one-hour programme about the cardboard school, Live Lab, will be broadcast at 7pm on 21 March on BBC1 as part of Science Week.

Using cardboard as a material

Westborough is not the world’s first cardboard building. Japanese architect Shigeru Ban has worked with cardboard on schemes such as the Japanese Pavilion at Expo 2000 in Hanover and a giant arch that acts as a pavilion in the gardens at the Museum of Modern Art in New York. The Japanese Pavilion, which Buro Happold also worked on, had a cardboard gridshell covered with a paper membrane. Ban has also developed refugee shelters for use in Rwanda and Turkey that use cardboard tubes and can be erected very quickly. Of course, unlike the school, these are all temporary structures. Indeed, the Japanese Pavilion has already been recycled. Cardboard has other uses in construction. Quinton & Kaines, the manufacturer of the Westborough panels, markets its standard panel for use in exhibitions and displays. Internal doors are often made from a cardboard honeycomb structure covered with thin plywood. This gives a strong, lightweight and cheap door. Cardboard tubes are used as disposable formers for casting reinforced concrete columns. They are also used as slip sleeves for piles used in clay soils to prevent heave. Buro Happold has successfully used short, capped tubes as void formers to reduce the weight of concrete floor slabs.

How the panels are made

The cardboard panels are made up of a basic honeycomb, edged with wood so they can be incorporated into buildings using conventional joinery methods. This means that if the concept is a commercial success, builders will be able to use the panels without having to learn new techniques. The timber edging also improves the structural performance of the panels, acting as a simple frame while the panels act as the skin, stiffening the structure. The team considered using cardboard tubes instead of timber edging, but this would have complicated the manufacture of the edges, as they would need to be semicircular to accommodate the tubes. The panels in the full-sized mock-up had angled timber edges so they would meet perfectly where an angled joint was required – at the apex of the roof, for example. This proved too complex to get right at the manufacturing stage, so the finished panels for the school are square-edged. Any gaps can be filled with shaped wooden fillets.