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.
