Building with Earth: Design and Technology of a Sustainable Architecture

property of the salt, this loam stays moist
for longer periods, and prevents water
penetration while it remains in this state.
If shrinkage cracks occur during drying,
swelling occurs during contact with rain
and seals the cracks. Once the rain has
washed off some of the salt, reducing the
self-sealing effect of the top coarse layer,
residents can either sprinkle salt or pour
salt water on it to regenerate the seal
(Dalokay, 1969).
When making loam-covered flat roofs, it
should be kept in mind that roof edges are
susceptible to mechanical damage, especial-
ly by wind and water erosion. This can be
prevented by solutions of the type shown in
14. 27. If the surface of the roof is to be
walked upon, then tiles are recommended
(14.27 D).
Illustration 14.26shows an inclined roof
from northern Venezuela, consisting of lay-
ers of cow dung stabilised with straw loam
mortar applied in several layers (8 to 12 cm),
over a wooden substructure made of
branches and twigs. After the rainy season,
the top layer is normally redone.

New solutions
In rainy areas, where inclined roofs are
common, traditional buildings do not have
loam roofs. However, recent experiments

have proved that additives can increase

the weather resistance of loam.

Bases on test results of the BRL, described

in chapter 4, p. 40, a low-cost housing

prototype was built at Pujili, Ecuador, by the

group FUNHABIT, Quito, and the author.

The roof was made of a timber substructure

built of tree trunks, branches and reeds. This

was covered by several layers of loam plas-

ter that were 8 cm thick in total (14.28). The

first layer consists of clayey loam thinned

with pumice (0 to 12 mm diameter) and

waste mobil oil (52 parts loam : 28 parts

pumice : 1 part oil). This mixture, which also

provided thermal insulation, was laid in a

fairly dry consistency and compacted by

beating. The top layer, 2 to 3 cm thick, has

the following mix: 72 parts loam, 36 parts

pumice (0 to 5 mm), 12 parts cow dung,

12 parts donkey dung, 8.5 parts mobil oil,

6 parts loose Sisal fibres (3 to 5 cm long),

and 1 part double-boiled linseed oil. After

several days, when the mixture was some-

what dry, it was recompacted with a metal

trowel, using great pressure, till the surface

was shiny.

116 Designs of building elements

Traditional wet loam techniques

roof, north Venezuela

14. 27Traditional flat

loam roofs

14.28Vertical section

through a loam roof, Pujili,

Ecuador

14.29Earth block domes,

village near Aleppo, Syria

14.30Earth block domes,

Siestan, Afghanistan

14.26 14.27

14.28