The only place you can't do it is in the polar regions, for obvious reasons.

LECTURE/Jean Dethier, 'Building with Raw Earth: An Eco Revolution?'

Fitzwilliam College, Cambridge, UK, 17 February 2009 www.eartharchitecture.org

'Let's look at a piece of earth', says Jean Dethier, flashing up a cross section of sod on PowerPoint. It's nothing special but, according to Dethier, 'this was the building block of human civilisation.' A former director of the Pompidou Centre in Paris, Dethier is now an evangelist for earth architecture, the oldest means of making buildings, currently enjoying a modest revival for its simplicity, economy, versatility and impeccable environmental credentials. Though Dethier clearly owes a styling debt to the late chanteur George Melly [purple jacket, red trousers, pink shirt and fetching red fedora], he is un homme serieux when it comes to mud. In his view, it's the only way to build, and it has contemporary applications beyond the familiar milieu of Africa.

As Dethier explains, earth architecture is everywhere -from the mud mosques of Mali to the cob cottages of Devon, from the adobe casas of the New World to the towering, painted cities of Yemen. Since humans first walked upright, successive civilisations have discovered the properties of earth architecture, putting it to all sorts of uses. Earth structures can adapt to different scales [Yemen boasts a 65m-high minaret] and different climates, from equatorial Africa to Iceland. 'The only place you can't do it is in the polar regions, for obvious reasons,' asserts Dethier. 'No raw material.'

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In the modern era, earth architecture has undergone some curious developments. During the Second World War the Nazis set up special units under Hitler's chief architect Albert Speer to investigate how to make buildings without using steel, as it was needed by the war effort. By this quirk of history, Germany is now highly advanced in the practice of building with earth. Scandinavia and Austria are not far behind and France can point to CRATerre, a Grenoble-based institute founded in 1979 which undertakes surveys of building types and trains architects in the techniques of earth architecture. These include adobe [mud bricks], pise [rammed earth in formwork], cob [clay, sand and straw] and infill [earth compacted in timber or steel frames]. Thirty years on, CRAterre is still training and exporting a new generation of architects to spread the mud gospel. But the older generation were no slouches: Frank Lloyd Wright and Corb both dabbled in it and in Egypt, Hassan Fathy memorably revived the techniques of his ancestors. Today, Dethier sees wider cause for optimism as architects in environments as diverse as Arizona [Rick Joy] and Bangladesh [Anna Heringer] get to grips with earth structures. Heringer in particular has given fresh impetus to traditional techniques, engaging with communities to build small-scale schools and houses that connect intimately with place and climate [AR December 2008].

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'As the world is changing, how can earth architecture help?' asks Dethier, who is eager to extol its environmental benefits. The raw ingredients-clay, gravel, sand, silt, soil, loam-are everywhere, and compared with other materials, a mud brick has a minute embodied energy [the energy used to manufacture and transport a unit of material]. It is also thermally efficient. Scale is not necessarily a limitation; the Yemenis, among others, regularly build up to seven storeys. To underline his point, Dethier pulls out a Saudi Arabian banknote depicting the Al-Murabba'a palace in Riyadh. With its massive earth walls, it looks as if it's been there for centuries, but was actually built in the late 1930s.

'Society shapes architecture and architecture shapes society,' concludes Dethier, quoting Grameen Bank founder Muhammad Yunus, whose microcredit loans have transformed life for the very poorest in the Asian subcontinent. Things can and do change, he asserts, and the revival of interest in earth architecture as a response to the current environmental crisis has the potential to spark new ways of adapting old techniques. Dethier is a compelling [not to say kaleidoscopic] crusader for this most immemorial of building methods and his arguments deserve a wider audience.

+ An impeccably eco-friendly approach to building

- Will today's architects be keen to get their hands dirty?