Masonry should be raised uniformly over the whole area. A slow progress of masonry work makes stronger joints and has more uniform settlement.
Unequal Settlement of the Sub-soil
Unequal distribution of the weight of the structure on the foundations due to eccentricity of loads. In continuous wall foundations reinforcement should be provided whenever an abrupt change in magnitude of load or variation in ground support may occur.
Horizontal Movement of the Earth Adjoining the Structure
This is effective in the cases of clay soils aid black-cotton soils. Such soils become soft and swall when wet loosing their bearing power considerably and shrink and crack when dry.
Atmospheric Action
Rain and the sun are the main agents for atmospheric action with the change of seasons. Rise and fall of the subsoil water level, increasing or decreasing the moisture content which is especially effective when the underground water is near the surface, or in damp soils overlying a layer of porous material like sand etc. causes cracks due to expansion or shrinkage of sub soil. Soakage of the rain water in the sub-soil also produces a number of changes as above and sometimes bring in salts which react chemically on the lime and
bricks m the foundations and cause them to disintegrate. Underground open drains should be provided to drain out the excess water when the subsoil water level rises. Deep foundations with sides (of the trenches) well filled and consolidated with good slope away from the walls given to the ground surface will help against rains. A plinth protection of about 60 to 90 cm width with concrete or flat brick flooring will give further protection. Cement or hydraulic lime should be used with stone or over-burnt bricks upto the plinth level in damp locations.
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