Earth As A Building Material

In 1982 a large exhibition and conference took place at the Pompidou Centre in Paris entitled 'A forgotten building practice for the future'. The theme was earth as a building material. Earth is, even today, the second most widespread building material in the world after bamboo. More than 30% of the world's population live in earth houses, mainly in less industrialized and developing countries. However, since the beginning of the 1980s, earth as a building material has experienced a renaissance both in Europe and in Northern America. The most important environmental arguments for earth building are that:

• it is based on a resource that is abundant in nearly all countries. In many cases the material can be excavated on site.

• it requires far less energy than is needed for concrete and fired brick buildings.

Traditional earth buildings in Yemen. Source: Tyabji.

Traditional earth buildings in Yemen. Source: Tyabji.

• if it is carried out correctly, it has a long life expectancy.

• it is based on reasonable and simple building methods which make self-help feasible.

• it provides good indoor climate due to its temperature and moisture regulating properties.

• unfired earth materials can be returned to nature more easily than any other material.

There are two main ways of building earth houses: ramming (pisé) where the earth is rammed between shuttering to make walls, and earth block (adobe) where the earth is first pressed into blocks and dried before use. In addition, there are many variations within these two main techniques.

Argillaceous marine earth is considered the best raw material for earth building. It is also possible to mix clay with other types of earth. Earth can be used in its natural state, and stabilizers such as cement or bitumen can be added to increase cohesion. It can also be mixed with straw, wood fibre or expanded clay pellets for reinforcement or to increase the insulation value. Given a good mixture, homogeneous earth construction has strong structural properties. There are examples of German earth houses up to six storeys high. As with other stone and cast materials tensile strength is poor, and arches or vaults are necessary over openings. Earth structures reach their ultimate strength after a few years. During the first months the walls are soft enough to be chased for electric fittings and to have holes bored for pipes, niches, etc.

The only serious enemy of earth construction is damp - careful design and construction is necessary to avoid damp problems, such as rising damp from the ground. Even a small detailing error can lead to problems. Concrete is tougher than earth in such situations.

Earth-building is very labour-intensive compared to most modern building methods. Within modern economic systems, where all the labour must be paid for, and is expensive, building with earth has become uneconomical.

Earth technology is, however, undergoing intensive development in both Europe and the United States (Figure 8.3). The processes can be simplified and partly mechanized. This includes commercial production of hollow and dense earth blocks at prices much lower than those of brick and concrete. There is now a larger choice of earth and clay based products, including ready-to-use mortars, floor and wall tiles, building sheets and acoustic panels. Pressed products often have natural fibres added for reinforcing and robustness during transport.

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