Building with earth - Gernot MINKE (1)

8 Direct forming with wet loam
Unlike other building materials, wet loam
has the capacity to be formed into any
shape. It therefore presents a creative challenge
to designers and builders. The manual
shaping of walls from lumps of wet loam
or thick loam paste is widespread in Africa
and Asia, and is also known in Europe and
America. Since no tools are required to
work with earth, it is the simplest and most
primitive technique. The prepared mixture is
used directly (without intermediate products
being formed or intermediate processes). Its
disadvantage is that even lean loam of only
10% to 15% clay shows linear shrinkage of
3% to 6% when drying. The higher the clay
content and the more water employed,
the greater the shrinkage. Thick loam paste
with high clay content may even have a
linear shrinkage ratio of above 10%. Illustrations
8.1 and 8.2 show a bench formed
with wet loam elements where shrinkage
was not taken into account. The following
sections explain how pre-designed shrinkage
cracks of smaller dimensions, or the use
of curved elements can help to reduce or
even avoid such cracks. The theory involving
reducing shrinkage by modifying loam composition
is explained in chapter 4, p. 39.
Traditional wet loam techniques
8.2
8.1
8.1 Forming a bench
from wet loam
8.2 Shrinkage cracks
in the same bench
after drying
8.3 to 8.4 Making
walls using balls of
wet earth, northeast
Ghana (after Schreckenbach,
no date)
8.5 Nankansi courtyard
house, north
Ghana
While in the case of earth block work, dry
elements are built up with mortar joints, no
mortar is used with wet loam work. Plastic
loam is bound simply by ramming, beating,
pressing or throwing.
In southern India, a very simple wet loam
technique is still in use today: using a
hoe, earth is mixed with water to a pasty
consistency, carried to the site in metal
containers balanced on the worker’s head,
and poured on the wall being built. It is
then spread by hand in layers from 2 to
4 cm thick. As the paste dries fairly quickly
in the sun, the wall can be built continuously,
layer by layer.
In northeast Ghana, another technique is
used. Here, balls of wet earth are formed
and then used to construct circular walls
simply by stacking and pressing (8.3 and
8.4). After the wall dries, the surface is plastered
on both sides and then smoothed
and polished using flat stones in a rotary
rubbing movement. Illustration 8.5 shows
72
Direct forming