For clayey and silty soils and for loose medium dense sandy soils with N < 15, a 450 mm square plate or concrete block shall be used.

According to Polishin and Tokar (1957), brick masonry will crack due to differential settlement when the unit elongation amount to 0.005.

For simple spread footing on clayey soils, the allowable pressure should be such that the differential settlement does not exceed 1/300.

The vertical downward movement of the base of the structure is called settlement and its effect depends upon its magnitude and uniformity etc.

It is suggested that allowable pressure should be selected such that maximum settlement of any individual foundation is 25 mm.

The allowable maximum settlement for warehouse type of structure is 50 mm.

The loading to the test plate may be applied with the help of a hydraulic jack. The reaction of the hydraulic jack may be borne by either any of gravity loading methodor reaction truss method.

Indian standards (IS: 1888: 1982) recommend that the loading of the plate should invariably be borne either by gravity loading platform or by the reaction truss.

The effect of settlement upon the structure depends on its magnitude, the length of the time over which it takes place, its magnitude and the nature of the structure itself.

The use of reaction truss is more popular now-a-days since this is simple, quick and less clumsy.