In detail

Renovating a raw earth building

Renovating a raw earth building

Raw earth has been used in construction for thousands of years and on all continents, including Europe. Today, it is experiencing renewed interest and damaged mud buildings, rather than being demolished, are now gladly restored. What you need to know to renovate in the rules of art.

The origin of the raw earth

Raw earth is one of the oldest building materials in the world. The first cities discovered in ancient Mesopotamia were built of raw earth before the invention of writing. But as it degrades faster than stone, the remains are less common. There are nevertheless very beautiful ones in Iran and Syria. Pre-Columbian civilizations in Central and South America also used the raw earth. In North America, there are many remains in the south of the country, clinging to the cliffs. The adobe and adobe constructions have also experienced a rebound since the 1960s in California, Arizona and New Mexico. In Europe, the first traces of raw earth construction date from 6000 BC in Thessaly. Raw earth was also used a lot in the Middle Ages, with half-timbered houses, and especially in the Age of Enlightenment, with real adobe and cob houses. Today, the French heritage in raw earth is very important: in Rhône-Alpes, with adobe, the South-West with adobe, Nord-Pas-de-Calais with mud and Brittany with cob.

What is raw earth?

The term "raw earth" highlights the difference with terracotta from which bricks or tiles are made, in particular. Raw earth, adobe or mud are three words to designate earth that has undergone little transformation and is used as a building material. It consists of pebbles, gravel, sand and clay mixed with a little water. It is also sometimes associated with straw or animal hair. There are several construction techniques with raw earth: adobe, mud, adobe and compressed earth brick. Raw earth is also used as a filling material, often between sections of wood: cob, earth-straw or earth-wood chips. Finally, raw earth is also used as a coating.

The advantages of raw earth

Raw earth is an abundant material, which requires little energy to make it, much less than lime, terracotta or cement. It generates very little CO2 and no waste. Thanks to its excellent thermal inertia, it regulates internal differences, for example by restoring the daytime the freshness stored at night. It also regulates the humidity of indoor air very well thanks to its permeability to water vapor, which makes it a particularly suitable material for people suffering from asthma or allergies, for example. It is also a good sound insulator. In addition, if the raw earth is well protected from the rain, it resists well over time. However, its implementation is quite long, resulting in a fairly high labor cost.

The restoration of the raw earth

Restoring the raw earth is delicate. It is necessary to identify the reason for the deterioration of the building (humidity is the main risk of deterioration of the raw earth), to correctly dose the composition of the material and to choose well its coating. So many parameters that make it often better to call a professional. To protect a raw earth wall, you must choose a quality coating, and above all not too rigid to let the earth breathe. Glue or cement-based coatings and paints are therefore to be banned. The choice of plaster also depends on the quality of the soil and the climate of the region. It is best to favor natural coatings based on clay, sand and straw.

Find a raw earth professional

Fortunately, there are more and more raw earth specialists since the construction sector takes ecological dimensions into account. The Confederation of Handicrafts and Small Building Companies (CAPEB) has created the Eco-Artisan label. The French Architecture, Town Planning and Environment Councils (CAUEs) offer training and therefore must be able to direct individuals to craftsmen trained in the various techniques, as well as associations specializing in ecological constructions. Finally, the national association of raw earth professionals offers an online directory of professionals. To know more : www.asterre.org