Building with earth - Gernot MINKE (1)

11 Loam plasters
11.2 11.3
11.1
Loam plasters consist mainly of sand and
silt with only as much clay as is necessary
(usually between 5% and 12%) for developing
their adhesive and binding forces. It is
difficult to determine the proportions of an
ideal loam plaster, because not only the proportions
of clay, silk and sand influence a
mixture’s properties. Other factors affecting
the composition are the grain size distribution
of the sand fraction itself, the water content,
the type of clay, the method of preparation
and the additives. In order to test the
appropriateness of loam plasters, samples
with varied compositions should be tested.
If the surface is rough enough, then loam
plasters stick well not only to loam surfaces,
but also to those made of brick, concrete
and stone. For the ability of loam plasters to
balance indoor air humidity see chapter 1.
sufficiently rough in order to develop a
good physical bond. If masonry is to be
plastered, especially when using larger and
very smooth bricks, it is recommended that
a 45° groove be cut with a trowel into the
joints, as shown in 11.1. Another method of
obtaining a good bond when rammed loam
walls are to be plastered is to wet them sufficiently
until surfaces are soft, and to then
scratch diagonal patterned grooves into
them with a small rake or a nail-trowel (11.2
and 11.3).
In order to ensure that the plaster adheres
well, plaster supports can be applied in the
form of galvanised wire mesh, plastic mesh,
reed mats etc.
Composition of loam plaster
Preparation of ground
As loam plaster does not react with the
ground chemically, the surface has to be
In order to keep loam plaster free of shrinkage
cracks, the following points must be
kept in mind:
• The loam should contain enough coarse
sand.
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Loam plasters