Civil Engineering Reference
In-Depth Information
Maintenance
All vegetable growth should be
removed immediately. The condition
of the roof protection is crucial to
performance.
Renewal of the coatings,
particularly the exterior coating, is
important. The construction should
be examined from time to time for rat
runs, and the holes filled with a
compatible mixture.
Restrictions due to weather
conditions
Earth walling should not be laid in
wet weather, and needs protection if
rain intervenes during the building
process. Cob is normally laid during
spring and summer, which avoids
frost conditions.
Workmanship
Cob working is a rural art. Essentially
it is not highly skilled, but it does
require experience. Pisé-de-terre is
normally rammed between climbing
formers (Figure 2.67), and wall
thickness is self-evidently easier to
control.
Work on site
Storage and handling of materials
Traditionally the mixing of raw
material was carried out by bullocks
in a pen (dung will be an added
constituent but, contrary to popular
conception, is not necessary for a
quality cob). Recent works have used
a mechanical excavator, both in
winning the soil and in mixing it by
running back and forth across the wet
mix.
Figure 2.67
Pisé-de-terre is normally rammed between
formers. The through bolts are necessary
for stability; they were withdrawn from the
wall subsequently and the holes pointed.
(The drawing shows the construction of
shutters used in the Building Research
Station experiments of the 1920s.)
Inspection
The problems to look for are:
◊
deterioration or leaking of roofing
◊
inadequate roof overhang
◊
dampness
◊
incorrect external protection
◊
rotting of timber lintels
◊
external render cracking
◊
rat runs
