The Rammed Earth Wall The characteristics of rammed earth are expressed most clearly in walls. Through the ramming and compacting of the material, an element is constructed that is capable of withstanding the influences of both time and weather. At the same time, this earth remains part of the natural cycle: if the wall is exposed to the elements, over the years rain will gradually wear away at the façade. Rammed earth will ultimately return without a trace to the soil from whence it came. Even an appropriately protected wall will eventually change: rain softens the surface, as the water washes away the finer clay granules. The colour of the wall will also alter with time, as loam is rinsed away and the stones begin to emerge. The integration of erosion checks made of trasslime or fired clay helps to control the loss of material.
The challenge in building an earthen wall lies in precisely foreseeing
this balance between ephemerality and permanence, and envisaging all the possible ramifications. And this also constitutes the special allure of earth construction. All these aspects are interrelated; for example, if the rammed earth were stabilized and not water soluble, it would be incapable of absorbing water vapour, which is the source of the pleasant indoor climate it can create. Without the rain eroding fine-grained material from the surface, the resulting patina, which gives the material its vibrant, tactile structure, would not exist. Over time, a balance between durability and transformation occurs naturally. While erosion never completely comes to a halt, the loam becomes harder and the stones in the eroded wall serve to stabilize it – as such, it is unnecessary to further weatherproof the façade with cement or other artificial aggregates. On the contrary, additives can significantly impede the positive natural qualities of earth – for example, its ability to be completely recycled (see section on Calculated Erosion, p. 70).
Nevertheless, there are several basic rules to follow with regard to
weatherproofing. The wall must be capped to protect it from standing water and seepage. Traditional buildings made of rammed earth cover the walls with a projecting roof. For constructions with a flat roof or with free-standing walls, coverings made of sheet metal or similar waterproof materials are appropriate. Since splash and rising damp also affect the wall, the plinths should be water resistant.
Constructing an in situ rammed earth wall requires a significant amount
of time, as the compaction process is labour intensive. In order to coordinate with the strict schedules of modern-day building sites – or if no other method is possible – large-scale earth construction projects are carried out with prefabricated elements. Construction cranes are used to install these rammed earth blocks; afterwards, the faces are grouted and the joints retouched. The horizontal striation of the earth and bands of trass-lime are meticulously finished off by hand until the visual appearance is homogeneous. Even if individual joints are still visible at first, the erosive effects of driving rain will soon create a uniform surface.
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