Civil Engineering Reference
In-Depth Information
forgotten. They are now on the march
again, soon at full speed in France,
Germany and the USA.
The aspects of earth building that
make it popular are:
• It is based on a resource which is
abundant in most countries. In
many cases the material can be
excavated on site
• It requires much less energy, a
small percentage of the energy
needed for concrete building; if car-
ried out correctly, it also has a long
life expectancy
Figure 8.2: Traditional earth building by the pisé method in
Bhutan, 1996. Photo: C. Butters
• It has reasonable and simple build-
ing methods which make self-
building feasible
• The earth buildings create a good indoor climate because of their good mois-
ture-regulating properties
• Buildings can be recycled more easily than those in any other material.
There are two main ways of building earth houses: ramming (pisé) where the
earth is rammed between shuttering to make walls, and earth block (adobe)
where the earth is first pressed into blocks and dried before use.
Argillaceous marine earth is considered the best raw material for earth build-
ing. It is also possible to mix clay with other types of earth. Earth can be used in
its natural state, and stabilizers such as cement or bitumen can also be added to
increase the cohesion. It can also be mixed with straw, sawdust or light clinker
for reinforcement or to increase the insulation value. If it is a good mixture,
homogeneous earth construction has strong structural properties. There are
examples of German earth houses up to six storeys high. As with other stone and
cast materials the tensile strength is poor, and arches or vaults are necessary over
openings. Earth structures reach their ultimate strength after a few years. During
the first months the walls are soft enough to be chased for electrics and to have
holes bored for pipes, niches made, etc. The only enemy of earth construction is
damp - very careful design and construction is necessary to avoid damp prob-
lems. Even a small detailing error can lead to big problems. Concrete is tougher
than earth in such situations.
