Earth Structures

13.18

A six storey earth building erected in Weilburg (Germany) in 1827. Photo: Oliver Abels.

13.18

A six storey earth building erected in Weilburg (Germany) in 1827. Photo: Oliver Abels.

Basic info is found in Chapter 8.

Earth structures consist either of rammed earth executed on site between shuttering (pisé), or of earth blocks laid in mortar (adobe). These two main techniques are suitable for buildings of domestic scale and considerably larger (Figure 13.18). Even with large amounts of plant fibres mixed in, the material is fireproof. Earth is also an excellent regulator of humidity. The oldest complete earth building in Europe, dating from 1270, is in the town of Montbrisson in central France. It now houses a library for moisture-sensitive books.

Earth buildings have many ecological advantages. Earth is a perfect material in terms of resources, pollution and indoor climate, and when the building is no longer needed, it simply reverts back to the earth.

Earth has, however, structural limitations as a building material since its compressive strength is fairly low. This is compensated for by building thicker walls. The increase in the amount of material used does not really matter if the source of earth is near the site.

Earth in itself does not have a particularly high thermal insulation value; better than concrete, and close to brick. However, the versatility and thermal capacity of plain earth constructions is good. By adding organic fibres or expanded clay aggregate the insulation value can be improved. Solid earth walls are best for buildings with low internal temperatures, or with external two-leaf walls containing a cavity. An exception to this is lightweight straw loam, see page 283.

As earth constructions are voluminous and heavy they should be based on local resources. Transport of adobe blocks is also subject to considerable wastage, since the blocks are not particularly strong.

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