Building with earth - Gernot MINKE (1)

• In order to decrease the curing time,
Mixtures
gypsum, lime or cement can be added.
As an alternative to loam fillers, all materials
As these additives also make the mixture
that can be commonly used for plasters
leaner, the shrinkage is reduced. The disad-
can be used as fillers. High-hydraulic lime,
vantages while adding these substances
cement, gypsum, casein, cellulose and
might be that the binding force and the
double-boiled linseed oil can be used as
compressive strength are reduced.
binders. Silt, sand, and gravel as well as
Joints and cracks in internal elements
organic aggregates like cork, sawdust, cereal
can be filled with a mixture of 1 part loam,
and rice husks, and shredded newspaper
0.5 to 1 part hydraulic lime and 0.5 to
can be used as fillers. When repairing exter-
1 part gypsum.
nal joints, organic matter should not be
If the joints are exposed to weather, gyp-
used except when the mix has a high
sum should not be used, but cement, high-
pH-value (which prevents growth of micro-
hydraulic lime or a mixture of these totalling
organisms). Acrylic or silicone elastic syn-
from 8% to 20% can be used as an addi-
thetic mixes can also be used as fillers.
tive. Instead of these binders 4% to 7%
Silicone bonds with loam, provided the joint
double-boiled linseed oil can also be added.
surface is dry and free of loose particles
This filler stays plastic for several weeks.
before application.
Application of filler
In order to get a good bond between the
Repairing larger areas of damage
old loam surface and the filler material,
cracks should be opened up to 1 cm with
Repairing with loam
loose particles brushed away and the edges
Larger eroded or flaked areas should be
of the joints sufficiently moistened so that
repaired by scraping off all loose loam and
the loam swells and gets plastic on the sur-
then wetting the surface before applying
face. When double-boiled oil loam is used
new loam, as described in chapter 11 on
as filler for repairing, the surface has to be
loam plasters.
treated with linseed oil.
In order to reduce shrinkage, each layer of
The plastic filler is first applied with a knife
loam plaster should not be thicker than
to both sides of the joint, and the opening
1 to 1.5 cm. If the damage is more than
then filled with a drier mixture of the same
2 cm deep, it is advisable to scrape the area
filler, tamped or hammered into the joint
to a depth of 4 to 6 cm. This is then filled
13.2
13.1 Pumping lightweight
mineral loam
13.2 Additional interior
thermal insulation
layer of lightweight
mineral loam in a
timber frame wall
(see 8.29). It is advisable that the joint is
filled with more material than is necessary,
so that when after the filler shrinks on drying,
it can be compacted again when still
slightly moist.
Repair of cracks and joints with other
fillers
with broken adobes and lean mortar. In
areas prone to frost, green bricks are not
advisable as they are not frost-resistant.
Coatings
If the coating of a loam surface is to be
repaired, the old coating should first be
scraped off. The area is then primed before
the new coating is applied. For this, limecasein
milk can be used, as described in
The repair of cracks and joints with a loam
chapter 12, p. 99.
filler is very time-consuming and requires
If the surface is very sandy and soft, a
some experience. However, other fillers
primer of lime-casein glue is better. This is
which show less shrinkage and better
prepared from 1 part hydraulic lime and
bonding qualities and require less labour
5 parts fat-free cheese mixed intensively for
and skill are described in this chapter.
two minutes without the addition of water.
The mixture is allowed to stand for a while
105
Repair of loam components