Ventilated improved pit latrines
Practical Action
two sticks. For a school or community latrine, the diameter should be 1.8 metres across, so
the string should mark a radius of 90-cm (3 feet)
If the ground is quite rocky and very stable during rains, then the brick lining may be
eliminated. In such cases reduce the radius (the length of the string) by 15cm.
Do not make the hole too wide, you can endanger the occupants.
Dig the hole 3 meters, (10 feet) deep. Be careful to keep the walls straight.
Foundation
Begin laying and mortaring courses of bricks at the
bottom of the pit. Alternate vertical joints in the
bricks. Do not lay bricks or plaster over the floor of
the pit, and do not mortar vertical joints.
Continue building up the wall of the pit.
When you reach the top layer, dig out a little wider
and lay the last row of bricks perpendicular, as
shown. Mortar the vertical joints in this row.
Most soils considerably soften during the rainy season. Due
to its weight, a brick superstructure is in danger of
collapsing without a strong foundation as described here.
The alternative is to build a light superstructure. Very light
superstructures, such as these, made from thin wattle and
daub, with grass roofs, should not require such a strong
foundation. Consult with a good carpenter or mason on how
to assure a strong and suitable foundation that takes into
account the soil type and the materials used in building. In
any case, the top layer of bricks described here should be
laid and the top half of the pit should be plastered with
mortar.
The un-mortared spaces in
the vertical joints allows the
contents to seep into the
soil
Figure 2: Lining the pit
Slab
For a 1.2m (4ft) diameter hole, make a 2.15m (7ft)
diameter slab.
For a 1.5m (5ft) diameter hole, make a 2.4m (8ft)
diameter slab.
This gives a stable 45 cm overlap to the hole.
Splash water on the mortar
after it has set and keep it
damp for one week
Next to the latrine, dig a hole in which to cast the slab. It
should have a diameter, which is 90-cm larger than the
mortared latrine pit, and a depth of 7.5cm. The floor
should be very smooth.
Diameter of mortared latrine pit + 90 cm
Figure 4: Digging a flat-bottomed
hole as a template for the mould
3
Figure 3: Dressing the top of the pit