||RAW CLAY STRUCTURES
Definition characters description and diffusion
Adobe constructions allow fuel saving which would otherwise be necessary to fire bricks, and also provide better thermal insulation of the buildings. The material used is easily found and treated.
General characters description and diffusion
In the Sahara, the red soil of the desert is still ground and mixed with water and with straw that increases its binding capacity. By means of wooden moulds it is shaped into rectangular bricks, the so-called Arabian tub. Through Andalusian Spain the term adobe (al-toub) derives from tub, which is generally used to indicate raw earth-brick structures. Dried in the sun, the bricks become resistant, thus no trees need to be cut down for firing them. The thick walls of the dwellings are made of these bricks, which create a perfectly insulated inner environment, suitable for both torrid summer days and cold winter nights. The rooms inside the dwellings do not have an exact function, but their use depends on the seasons and climate changes. The terraces too, surrounded by high adobe walls, turn into ventilated bedrooms with the starry sky as a ceiling on hot summer nights. In the Sahara, the most archaic building system of adobe walls uses semi-spherical raw earth-bricks. This technique is still used for the perimeter walls of the cropping areas. Both their shape and the method of laying them make these walls very similar to the 'herringbone' masonry work, made of plano-convex bricks and produced in Mesopotamia in the 3rd millennium. A wicker basket is used as a mould, and the bricks, after having been dried in the sun, are arranged in alternate oblique strips, thus shaping a herringbone design. The interstices in the wall form a sort of decorative 'open-work', which is above all the most suitable protection against sandstorms. A completely closed barrier, in fact, would cause heaps of materials carried by the wind and the plots would be progressively buried in sand. This building technique is supposed to provide gardens with a greater water supply. At night, the wind blows against the convex sides of the bricks and releases humidity into the earth the walls are composed of. During the day, the hot wind penetrates the interstices in the wall and reaches the garden, where heat is absorbed and the temperature decreases. Other types of bricks still in use in sub-Saharan Africa are mere hand moulded spheres. In southern Arabia, instead, by directly pressing wooden moulds on the rolled-out mud mixture, wide and flat bricks are made. Long muddy 'sausages' are also made, hand shaped and arranged in consecutive spirals to form a wall. However, a technique that does not use bricks is the so-called pisé: the raw earth mixture is poured into wooden moulds and pressed. Once the mixture has dried up, the wooden planks are taken off and used again to make another form. This practice is shown in the ancient Egyptian drawings. The sites of Çatal Hüyük in Anatolia near Konya and of Jarmo at the foot of the Zagros mountains in Iraq are all Neolithic settlements, made of adobe bricks only, just like the first constructions in Jericho. In particular, due to its size and the complexity of its structures as well as to the quality and quantity of findings, the site of Çatal Hüyük is so important that it is thought to have been the first town ever built, the cradle of civilisation. Buried in a tell of about 7 hectares, only a very small part of which has been excavated and with huge difficulties, the large built-up area consists of a series of closely clustered habitats made of adobe bricks only. The site plan and the materials used in Çatal Hüyük are very similar to those of the thousands of adobe-construction settlements in the Saharan oases, which are still inhabited. Adobe constructions and clustered habitats are used here because they suit the local environment and climate conditions and the need for a careful use of natural resources. This kind of close-built structure continue to be used in California for valuable adobe houses and in Southern Italy and in the Loire in France, where the houses in the caves are the most appreciated and costly. In the Hadramaut valley, in southern Yemen, the old knowledge is perpetuated in order to build a complex adobe city system along the arid course of the wadi, transformed into a rich valley full of life and cultivations. Each family can inhabit elaborate buildings since the low cost of the materials and the social cooperation enable everyone to erect beautiful constructions.
Advantages and sustainability
Raw clay bricks are beneficial because the materials needed to construct them are easily found and do not need to be heated or cooked which allows for fuel savings. These raaw clay bricks also provide better insulation for the structures in which they are used.