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< prev - next > Water and sanitation Sanitation KnO 100427_Ventilated improved pit latrines (Printable PDF)
Ventilated improved pit latrines
Practical Action
If the soil is to rocky to make a smooth floor, in the shallow hole, then build a
form using lumber, or place a sheet of polythene plastic within a circle of
Diameter of mortared latrine hole +
90 cm
Figure 5: An alternative method of moulding using forms
Carve two forms (from either wood or brick) as shown. They should be at least
7.5 cm thick. They will be used to cast the squat hole and the chimney hole
in the slab. The chimney form can either be round or square.
Figure 6: Mould inserts
Figure 7: The weld mesh
needs to be cut to size
To add strength to the floor slab,
weld mesh is set into the centre of
the concrete slab. You need to
cut and tie together pieces of 2”
weld mesh (or BRC weld mesh) to
fit inside the shallow hole. Where
the formers are positioned, for the
chimney and squat hole, you need
to remove some of the mesh to
leave room for the formers to be
released. Mark the ground where
the forms go, and leave them in
Figure 8: The weld mesh is placed onto the
Then removing the wire
mesh carefully and
leaving the forms in
place, you should be
able to cast a reinforced
concrete slab.