Igloo type brick kilns in Zimbabwe
Practical Action
part of the roof and strechers form the outer cover, which is in turn plastered with cement
mortar. Provision is made both within
the wall and the roof for inspection
holes which are spaced evenly around
the kiln.
In the majority of the cases there is
one opening/entrance for both
loading and discharging of the kiln.
However, in rare cases, two opposite
openings are provided. Firing
chambers with an arched roof are
evenly spaced around the kiln wall.
The number of firing chambers within
one kiln ranges from 8 to 13.
A kiln with an inside diameter of about
seven metres would require
approximately 65,000 common bricks
Figure 3: Monitoring the state and colour of the bricks
through an inspection hole.
and the total construction costs would
be roughly US$ 8,000. The use of refractory
bricks would definitely increase the investment
cost of the structure. Chimneys are normally
constructed to serve 3 to 4 kilns. Chimneys which
are normally 13 to 15 metres high are located at
about 30 to 50 metres away from the kiln.
Setting of bricks inside the igloo kiln
In an igloo kiln, brick setting density is generally
lower than brick setting density in a field clamp.
Face bricks are arranged inside the kiln in such a
manner that at least both stretcher faces will be
exposed to the heat, and there will be adequate
space for the flow of heat without undue
restriction from the top of the kiln to the floor,
and out into the chimney. Enough space is left
as well between the kiln wall or roof and the
brick setting for specifically the same reason.
Figure 4: One chimney serving several igloo kilns.
For face bricks, normally a pattern known as "Pillar
Setting" is employed and in this pattern bricks are
laid on their bed faces. Bricks are arranged in the
form of pillars, which are then linked together, as
shown in Figure 6.
3 Figure 5: Methods of setting bricks for firing