Rammed Earth

Building the Old-Fashioned Way

One of the world's oldest building techniques, rammed earth has quickly gained favor with the advent of greener lifestyles and economy. The technique consists of compacting a mixture of clay and sand (sometimes with the addition of a stabilizer) within wooden forms to create the walls of a structure. The process has been used on longstanding structures like the Great Wall of China. Once cured, rammed earth walls are nearly as strong as solid rock.

Rammed earth provides great sound reduction and has adequate thermal mass, much like that of concrete. Subsequently, rammed earth is most often used in arid or semi-arid climates where temperatures do not dip too low. Nowadays, most rammed earth homes are built on concrete foundations, especially in wet climates, where water could cause erosion of the walls. However, rammed earth has been used everywhere, from the wet climates of England to the most arid regions of Africa, so it is a viable building material. Also, insulation can be added for those looking to employ the technique in colder climates.

Where is Rammed Earth Used?

In the US, regulations can be restrictive of rammed earth dwellings. Texas, New Mexico, Arizona and Colorado are the most building code-friendly states, so the material is commonly used in these four. California has a fair share of rammed earth buildings, but permitting is more difficult. With the evolution toward green living, there are attempts to write the material into ASTM standards, which would allow for more widespread use. 

Material Specifics

Rammed earth usually consists of a thick wall  of at least 12", much like that of a cob house.  The mixture, usually about 30% clay and 70% sand, is then added and compacted to half of its original height.The process is repeated until the wall is of desired height. Modern methods of mechanical compaction are favored, but human-driven methods do still work. You can use concrete as a stabilizer if you wish, but concrete manufacturing typically accounts for 10% of man-made carbon emissions, which dampens its green audience.Lime is a great alternative for stabilization.

http://www.greenhomeimprovement.com/materials/rammed-earth