spaces thus created are then filled with a
third layer of loam mortar stabilised with
6% to 8% (by volume) of double-boiled lin-
seed oil. The surface is then smoothed by
rubbing with great pressure using a metal
trowel (14 .19) until the surface becomes
shiny.
Since this process is very labour-intensive,
the author of this study has developed an
alternative design requiring significantly less
labour (less than a fifth):
The layers constituting this floor can be seen
in 14. 21. In order to break up capillary
action, the lowest layer is formed by coarse
gravel. A damp-proof coarse of bituminous
felt paper is laid over this, followed by a
base thermal insulation layer of rockwool.
(The latter is necessary only by the stringent
demands for thermal insulation contained
in more recent German regulations; other-
wise lightweight loam would be sufficient.)A 12-cm-thick lightweight mineral loam is
poured on top of this layer. This provides
both sufficient thermal insulation and the
required structural strength.
The lightweight loam was prepared in a
normal concrete mixer and then poured
from a wheelbarrow (14.22).
In order to reduce hardening time, 4%
cement was added to the mix. In order to
achieve adequate surface hardness, a
3-cm-thick loam mortar (containing suffi-
cient coarse sand to minimise the occur-
rence of shrinkage cracks) was applied in
two layers. For this mortar, 6% (by dry
weight) of three different stabilising agents
were successfully tested: the first, soda
waterglass was added after being thinned
1:1 with water; the second, double-boiled
linseed oil; and the third, lime-casein glue
(made from 1 part hydraulic lime and
5 parts fat-free white cheese mixed vigor-113 Designs of building elements14 .17
14 .18
14 .19
14.20