The depth of footing should also be such that rate of angle of spread of load from wall base to outer edge of ground bearing does not exceed permissible value.

In case of old wells, all those materials should be removed from well and well, thus cleared, should be filled with hard material. Then suitable beams or arches should be provided to span well.

Tension pile or uplift pile anchor down structures subjected to uplift due to hydrostatic pressure due to over turning moment. Such foundations are always under very high tension and hence need to be laid very carefully.

The rain and son are main atmospheric agents to seriously affect foundation of a building. The rain may carry certain Chemicals and salts obtained from sewage, animal dung, etc. which reacts with foundation and leads to its destruction.

A strip footing is one that provides a continuous longitudinal bearing. Thus, a spread footing for a continuous wall is called a strip footing. The above given diagram shows two types of strip footings for a wall- i) Simple strip footing without masonry offset and
ii) Strip footing with masonry offset.

The horizontal spacing between two footing in case of average soil is adjusted by keeping angle of inclination is 45°. The horizontal spacing of to footing its adjusted in such a way that edge of bottom of new footing is not intersected by this line.

Grillage Foundation is very useful where bearing of soil is poor. The depth of foundation is limited from 1 m to 1.5 m. The load of column is distributed or spread to a very large area by means of layers of joists.

The above given figure contains steps or offsets and it is also referred to as stepped footing. Such type of footing are commonly used in small buildings or single storey buildings in which load is distributed step wisely into ground.

In this case, width of footing would be very low. In this type of footing, wall directly rests on concrete base and no masonry offset are provided since spread is not required.

Due to unequal settlement of sub-soil, cracks are formed in buildings, which in future, leads to serious defects. To prevent such failure, foundations should rest on rock or hard murum.