Building real buildings with cardboard

Dr Andrew Cripps, Buro Happold Consulting Engineers, 17 Newman St, London,In partnership with: www.cardboardschool.co.ukCottrell and Vermeulen Architects ArchitectWestborough School ClientEssex Tube Winding Ltd Manufacturers of card tubesPaper Marc Manufacturers of paper and boardQuinton and Kaines Manufacturers of panel productsC G Franklin Building ContractorDept of the Environment, Transport and the Regions Government Sponsor

Introduction - why build with cardboard

Cardboard is a material with an imageproblem. People think of it as a disposable,short life packaging material with poorproperties. In reality it can perform very wellover an extended period if it is designedcorrectly and treated properly. Perhaps mostimportantly from an environmental andsustainability point of view it is also madefrom a waste product for which there are fewalternative uses - paper. This makes efforts tofind appropriate construction uses ofcardboard appealing in environmental terms,as well as offering an interesting challenge.

There are already several common uses ofcardboard in construction, and more still inthe furniture sector. A large proportion ofinternal doors are filled with a cardboardhoney-comb, covered with a thin laminate.Tubes are used for column forming becausethey are cheap and available in large numbers.This not only reduces cost compared to othersorts of form work, but can save time as well.Tubes are also being used to help the processof pile driving. Panel products are widelyused in temporary and Exhibition structures.

Cardboard dominates the packaging industry,because of its low cost, but also its ability togive enough protection to the object beingpackaged. There is no need for greaterstrength for breakfast cereal boxes; theseproducts normally reach us in good conditionso it is clearly doing its job. But by coatingcardboard it is possible to use it fortransporting frozen fish. Perhaps most strikingis its dominance of the fruit drinks market,

where a vast quantity of liquid is transportedin cardboard boxes lined with aluminium andplastic.

What these examples show is that like anyother material, cardboard, when engineeredcorrectly, can do the job it is asked to do.

Figure 1:Card beam under two man test load!

Environmental issues

The process of paper and cardboardproduction is interesting from anenvironmental point of view, and has oftengenerated debate. All of the materialsinvolved are relatively cheap and bulky, sothat transportation is a key issue forconsideration. However fundamentally, usingcardboard products must help to find a securemarket for the waste paper that is otherwisefinding its way into landfill sites.

Worldwide the annual use of paper and boardis about 300 million tonnes, and this requiresa lot of trees. The card industry is one of thelargest users of post consumer waste paper.

The issues to consider in terms of paperrecycling are the collection and movement ofthe material, and any waste products removedin the process. These wastes are both solids,like plastics or any stray metal, and liquids,including any inks or water repellents. Theenergy balance of recycling also deserveschecking, as if it is carried out sufficientlyinefficiently it might be less energy intensiveto use new trees instead.

Overall I am confident that wider appropriateuse of cardboard in construction will have apositive impact on the environment.

What has been done before

The largest number of cardboard buildingshave been designed by the Japanese architectShigeru Ban, most recently the very largegridshell for the Japanese pavilion at theHannover Expo. However, in my opinion, themost important work he has done has been inemergency shelters. These have been used inAfrica and more recently in Turkey followingthe earthquake there, and have been based oncardboard tubes.

Figure 2: Local Zone in the Millennium Dome

Buro Happold has experience of large scaleconstruction with cardboard, with threeimportant projects being the Local Zone (alsocalled Shared Ground) in the MillenniumDome, the Japanese Pavilion for theHannover Expo in 2000 and a cardboard arch

in the garden of MOMA (Museum of ModernArt) in New York. All three of these examplesinvolved the architect Shigeru Ban again,although others were also involved.

Our project

One of the features of most of the previousexamples is that they are short lifetimebuildings. At Westborough school we wantedto develop something more modest in termsof size, but with a longer useful life.

The Westborough school, near Southend tothe East of London, is a large school for theunder 11s, with over 700 pupils. The projectis for an 'after school club', which alsoprovides toilets for the playground, and ageneral purpose space for the school.

Our current design thinking is shown in thetwo images below. The intention is to makean interesting building, so that people havefurther reason to take note of it. Its formreflects the nature of cardboard, in particularthe corrugated nature of the South facingwall. The main approach is to use 50 mmthick honeycomb card built up in three layersto make a complete wall or roof panel. Theseare timber edged to aid jointing. Across thecentre there is a wooden truss, necessary tospan the width of the building. This issupported by cardboard tubes; other tubessupport the roof on the side with the largewindows.

Figure 3: Internal view from design concept

Figure 4: Aerial view of design concept

Dealing with fire and water and otherhazards

Water

When you talk with people about buildingwith card, they nearly always ask somethinglike, 'Won't it get soggy when it rains?' Theanswer is of course yes - unless you dosomething to stop it. In this case we haveopted for a 'belt and two sets of bracesapproach', we do not have time to test options.

First we are treating the card with a waterrepellent chemical, to prevent the cardabsorbing moisture from the air, and to allowit to survive any accidental wetting. Thischemical is removed in the re-pulpingprocess, so allows recycling, although in anideal world it would be avoided.

Secondly, each panel is coated with a plasticlayer, to keep moist air or liquid water out.This coating is also removed by the pulpingprocess.

Finally, on both the inner and outer faces ofthe panel, there will be a protective top layer.On the outside this will serve as a rain-screenor tile, and on the inside as a pin-board for theclassroom. This outer layer may well need tobe replaced every few years, as it will bear thebrunt of footballs on the outside, andwhatever the children are doing on the inside!

Fire

Although cardboard obviously does burn, it isactually very similar to wood in its fireperformance. This means that it tends to charon the surface, and therefore although it isdamaged, it does not contribute significantlyeither to the heat of the fire nor to the spreadof flame. Hence, in this case at least, the issueof fire is not as critical as might be expected.

Other hazards

The description of the panel system coveredthe approach to natural wear and tear with theouter and inner layers. The outer layer is notfully specified yet, but will also need to betough enough to discourage deliberatedamage. However the school does not have aproblem with vandalism so this aspect doesnot need to be excessive.

In other locations there could be more of aproblem with vermin of various types. Care isneeded in the detailing to make it difficult forany to gain access. We can learn from thestraw building community in this respect.

Conclusion: Environmental impacts

One particular benefit of using honeycombcardboard as the main structural component,is that it provides good insulation at the sametime. Calculations show that the panelstructure we plan to use has a U value ofaround 0.3 W/m2 and this is sufficient toexceed the UK building regulations.

In setting out on the project, we set ourselvesthe target of achieving 90% recyclability, and90% recycled material input. It is important toemphasise that the need to deliver a viablebuilding supersedes those targets, but we arestill confident we will be close to achievingthis through the use of so much card.

Everything in sustainable constructioninvolves some compromise, and we arecomfortable with where this project is takingus - but believe others could go further.