Building with Earth: Design and Technology of a Sustainable Architecture

Preparing the mix
Tests with 30 different mixtures, including
some containing straw, sawdust and pine
needles, showed that shrinkage reduction
and increase of output was negligible, indi-
cating that the additional labour and effort
involved in introducing these additives was
not worthwhile. However, the addition of
whey increased output slightly, and gave
better water resistance and surface hard-
ness. Casein powder and water can be sub-
stituted for whey. The mix for this technique
must have higher clay content than that for
rammed earth blocks. A clay content of
15% was found advantageous. Loam ele-
ments with lower clay contents showed
cracks at the corners. The content has to be
optimised so that the finished profile is dry
enough to be handled, yet wet enough to
adhere when being stacked into the wall.

Laying the elements
In the first test building made at the Uni-
versity of Kassel, Germany, in 1982 (8 .17
and 8 .18), 2-m-long extruded profiles were
transported on a board and flicked over
onto the wall. The joints were finished by
pressing them with bare hands or with
a modelling stick. Since the weight of the
upper layers cannot be allowed to squeeze
out the lower material, only three to five
layers are possible in a day.
As these profiles showed shrinkage of
about 3%, it was necessary to refill the
shrinkage cracks that appeared. Since this
was laborious, at the next application of this
technique in a residential house at Kassel,
Germany, in 1984, only 70-cm-long profiles
were used. The results showed that at this
length, and with pre-designed contraction

joints spaced at 70 cm, no shrinkage occurs

in the elements themselves. The extruder

was positioned at the centre of the house

to minimise transportation distances.

76 Direct forming

8 .15

8 .15Vertical extruder

for extruded loam pro-

files (Heuser)

8 .16Horizontal

extruder for extruded

loam profiles (Heuser)

8 .17 t o 8 .18Walls of

extruded loam pro-

files, test house, Uni-

versity of Kassel, 1982

8 .19Extrusion of loam

profiles

8 .16

8 .17

8 .18

8.20 to 8.22Stacking

extruded loam profiles

in a plastic state

8.23Smoothening

the surface with a wet

sponge

8.24Sculptured interi-

or wall made of

extruded loam profiles

8.26Filling a contrac-

tion joint with slightly

moist loam