TECHNIQUES

Rammed earth construction, also known as pisé de terre
or simply pisé, is an age-old building method that has seen
a revival in recent years as people seek low-impact building
materials and natural building methods. Traditionally,
rammed earth buildings are common in arid regions where
wood is in scarce supply.

Walls are constructed from a mixture of earth that has
suitable proportions of sand, gravel and clay sometimes
with an added stabilizer, cement has been the stabilizer of
choice for modern times.

Formwork is set up creating the desired shape of the
section of wall, damp material is poured in to a depth of
between 100 to 250mm (4 to 10 inches). A pneumatically
powered backfill tamper - something like a hand-held pogo
stick with a flat plate on the bottom - is then used to
compact the material to around 50% of its original height.
Further layers of material are added and the process is
repeated until the wall has reached the desired height. The
wall is so solid that if desired the forms can be removed
immediately. This is necessary if wire brushing to reveal
texture is desired otherwise walls become too hard to brush
after around 60 minutes. Walls take some time to dry out
completely, but this does not prevent further work on the
project. Any exposed walls should be sealed to prevent
water damage - there are several proprietary products
specifically designed to seal earth walls.

In modern variations of the method the rammed earth walls
are constructed on top of conventional footings or a
reinforced concrete base, sometimes with extra ground
insulation from a horizontal layer of styrofoam. Some
builders also add coloured oxides or other items such as
bottles or pieces of timber to add variety to the structure.

Once completely cured the walls are very workable. It is
easy to drive a nail or screw into them and they can be
patched if necessary with the result being undetectable if
the same material was used.

One of the significant benefits of rammed earth
constructions is its excellent thermal mass; it heats up
slowly during the day and releases its heat during the
evening. This can even out daily temperature variations
and reduce the need for air conditioning and heating. On
the other hand, rammed earth is not a good insulator. Like
brick and concrete (which also have excellent thermal
mass), rammed earth is often insulated in colder climates.
The thickness and density of the walls lends itself naturally
to soundproofing and the materials used in the walls make
them virtually fireproof.

Prior to the use of cement as a stabilizer, rammed earth
buildings were most successful in dry climates with limited
availability of building materials other than earth. Rammed
earth has become a viable material in wetter climates, either
through the use of cement stabilisation, through placing the
earth walls within the weatherproof fabric of the building, or
by the application of external insulation and
weatherproofing.

VAULTED STRUCTURES

Elie Mouyal is the pioneer in architecture to work to revive
and integrate in the 21st century the techniques used in
past centuries and millennial, such as those developed in
ancient Egypt, in Spain during the Arab golden Age or
during the period of Gothic architecture in Europe.

Over the ages, people developed first many types of arches
and later on many kinds of vaults and domes. Arches were
mainly used to easily span openings without using wooden
beams. This was done according to their cultural and
technical developments and the available materials.

Vaults and domes were not only developed for technical
reasons or to avoid the use of wood. As we have seen, they
manifested also a spiritual dimension, as happened with the
development of Gothic architecture in Europe. In this period
of time, there was such a religious fervour, that architects
and builders could find the way to transform the heavy and
massive Roman style into structures of lightness with the
Flamboyant Gothic architecture. Barrel and groined vaults
evolved into the rib system of the pointed vaults. These
developments were often the result of technical experiments
which were not always immediately successful.
An almost infinite variety of arch types, styles and shapes
can be found all over the world. This variety evolved with
the available local materials, and know-how of the time, but
especially with the particular creativity and preferences of a
culture.