Floors of latrines, whether laid on the ground or supported over a pit, should be smooth and impervious so that they may be cleaned easily and have a satisfactory appearance to users. The upper surface should be at least 150 mm above the surrounding ground level (Fig. 7.8) to prevent rain and surface water entering the latrine.
The floor surface should slope gently to facilitate cleaning and to prevent surplus wash water from collecting in puddles. The slope is normally from the outer edge of the floor towards the squat hole or pan at the centre, so that the water used for cleaning flows into the pit and does not foul the area surrounding the slab. A fall of about 20 mm between the edge and the centre of a slab up to 1.5 m across is sufficient to prevent pools of liquid forming (Fig. 7.8). Where seats are used, the floor should slope away from the seat support so that any wash water flows towards the latrine entrance.
Fig. 7.8. Requirements of slabs
If a precast slab is smaller than the inside floor area of the superstructure, an impervious surface is normally provided to seal the area between the slab and the inside wall of the building. Any area around the slab which is left as bare earth could be fouled, thus becoming a possible site for hookworm infestation. However, in order to minimize costs, the space around the squatting area inside the superstructure should be limited. This reduces building costs for the superstructure as well as flooring materials. But the squat hole or pan should not be so close to the superstructure that users are forced to lean against the wall when they are trying to defecate. A minimum floor space of 80 cm in width and 1 m from front to back is normally acceptable (Mara, 1985b).