as a building material
Raw earth is « an always unique mixture of various types of grains, which give it a wide variety of aspects, colours and textures - abundant advantages giving it the ability to adapt to numerous construction techniques. »
Fontaine L., Anger R., Bâtir en terre. Du grain de sable à l’architecture, Belin, Cité des sciences et de l’industrie, 2009.
Earth comes from the mother rock, which for millions of years has been transformed through a slow degradation process and complex particle migration mechanisms. The result is multiple characteristics, the variations of which are endless. Because of this diversity, being able to recognise the properties of a particular earth is fundamental in order to use it properly as a building material.
Earth consists of grains of varying sizes, air and water. More specifically, the earth is a clay concrete. It is a composite material made of aggregates (gravel, sand, silts) agglomerated by the addition of water on a binder matrix, the finest fraction of the earth: clay. These elements then form a material that, when dry, becomes compact, solid and with which one can build a wall, a building, a city.
Traditional and contemporary raw earth construction techniques are numerous. Among the most common are: adobe (dried raw earthen brick), rammed earth (monolithic wall of compressed earth), wattle & daub (plant structure and infill of fibered earth) and cob (monolithic wall of stacked earth mixed with fibers).
Why build with raw earth?
« For human habitat one can only use materials that are on the earth's crust - where man lives. Like earth, stone, brick, wood, reed. The essential thing for the materials used is the relation of man and material. All energy, all love invested in the material by human labour, any dialogue between the user and the material remains as a reflection, as a permanent radiance of the material and has a positive effect on the future user. »
Hassan Fathy, Construire avec le peuple. Histoire d'un village d'Egypte: Gourna (1970). Ed. Sindbad ACTES SUD.
Raw earth has been used for millennia. Building with this material is first and foremost a continuity process, while respecting the traditional cultures of construction and showing that the techniques of construction in raw earth are not a thing of the past and can adapt very well to current contingencies and needs.
Globally, cement production accounts for about 5% of total CO2 emissions (Fontaine L., Anger R., Bâtir en terre. Du grain de sable à l’architecture, Belin, Cité des sciences et de l’industrie, 2009.). Reducing the use of cement in construction can thus significantly reduce the negative impact of the building industry on the environment. This reduction must be made in favour of materials with low energy footprint and excluding synthetic materials or those containing chemical substances that contaminate soil, air, water, animal and plant species, and of course, humans. Raw earth accumulates these qualities because it is entirely recyclable, requires very little energy for its transformation into building material and constitutes a completely healthy material. Using local earth also means avoiding energy-intensive transport and combating global standardisation of construction.
The advantages of earth as a building material are multiple: hygrothermal regulation (permeability to water vapour, regulation of temperature by its capacity of sorption / desorption of water vapour), capacity of odour absorption use as acoustic buffer, adaptability to ancient and contemporary buildings, etc.
All these advantages contribute to the increase in the comfort of the inhabitants of buildings and constitute a healthy solution for people and the environment.
Architecture in raw earth is beautiful: on an aesthetic level, it offers colours and textures whose nuances are inimitable by synthetic products.
Finally, the development of a raw earth building sector at the local, regional or national level multiplies the potential for sound economic development.