Building with earth - Gernot MINKE (1)

Rammed earth floorings
Hard-wearing floor surfaces need to meet
very high standards. They must resist pressure
abrasion, be waterproof and show no
cracks. It is very difficult to build such surfaces
from loam, but if carefully done, it is
not impossible. The most difficult criterion
is to achieve sufficient strength against abrasion
or surface hardness (see chapter 2,
p. 34). It is often easier to avoid the effort
involved in achieving this by using brick,
timber or stone floor tiles over the loam,
or by covering the loam with a carpet, rug,
fabric etc.
cement plaster surface, loam plaster that
contained loam with a high clay content
and large amounts of coarse sand and
fine gravel was used. This was applied in
a 7-cm-thick layer and compacted by beating.
In order to harden the surface, it was
sprinkled with Fe 3 O 4 flakes (flakes produced
by forging glowing iron) and beaten into
the surface together with cow’s blood,
cow’s bile or tar.
A
B
14.15
Traditional earth floorings
Illustration 14.15 shows Niemeyer’s version
of a traditional loam floor (Niemeyer, 1946).
The base layer consists of loam, about
15 cm thick, with high clay content. This
acts as a water barrier, and is applied in two
layers that are compacted by beating or
ramming until no cracks appear while drying.
The next layer consists of coarse gravel,
which interrupts capillary action. Above this,
a 10-cm-thick layer of straw loam provides
thermal insulation. An additional 4-cm-thick
layer of straw loam, stabilised with cement
in the proportion 1:6 (1 part cement : 6 parts
straw loam), is added so that heavy loads
can be carried. As the final layer, Niemeyer
recommends a 2-cm-thick layer of cement
mortar with sawdust. Two coats of waterglass
are then applied while the final layer
is still moist. Finally, after it is completely dry,
the surface is waxed.
The author of this study suggests reversing
the sequence of the bottom two layers.
To interrupt capillary action, coarse gravel
should be used as the lowest layer. Loam
with a high clay content should form the
next layer, acting as a water and vapour
barrier (damp-proof coarse). As described
below in this chapter, stabilised loam mortar
may be substituted for cement mortar. In
traditional German farmhouses and barns,
earth floors were built in a similar way, so
that even cars (without pneumatic tyres)
could drive over them. Instead of the
Modern earth floorings
In 1984, the two different loam floors
shown in 14.16 were successfully tested at
the BRL. Design A has a surface, hard
enough to be walked on, that is divided by
a timber grid, while design B shows a loam
floor paved with timber blocks.
The subflooring is identical in both cases,
consisting of a 15-cm-thick capillary breaking
layer of gravel, followed by a water and
vapour barrier of plastic or bituminous felt
paper, and topped with a 10-cm-thick layer
of expanded clay that acts as thermal insulation.
The first layer of moist clayey loam is placed
on top of this subflooring and rammed
(14.17 and 14.18). In both cases, a primary
grid of timber battens (10 x 10 cm) is laid
over this.
In design B (14.16), this grid is then filled
with timber blocks laid with a loam mortar
stabilised with 6% to 8% (by volume) of
double-boiled linseed oil. The blocks are
placed so that the annular rings are exposed
(14.20).
In design A, a second layer of loam mortar
is applied and rammed, over which a
secondary grid of timber strips is laid. The
14.15 Traditional flooring
for living rooms (after
Niemeyer, 1946)
14.16 Modern earth floorings
(Minke, 2000)
14.17 to 14.19 Making
a rammed earth floor
14.20 Making a rammed
earth floor with a wood
block cover
14.16
112
Designs of building elements