What is an Isolated Footing?

Isolated footings are shallow foundations ( Depth to Breadth ratio > 1) that are provided under the columns. In can be square, rectangular or circular in shape. These are simple footing which is mainly adopted for lighter loads. For heavy loads, stepped footing can be provided.

Features of Isolated Footing

1. Isolated footing taking any form or shape is provided such a way that, it maintains proportion and symmetry so that the resultant of the applied forces and the reactions coincide. 
2. The slab provided in isolated footing is of uniform thickness.
3. The slab can be either stepped or sloped.
4. Among stepped and sloped footing, stepped footing is more economical.

Fig.2. Types of Isolated Footing

Structural Behaviour of Isolated Footing

Isolated footing, under the action of uplift pressure from the soil underneath, is subjected to bending in upward motion called the cantilever action as shown in figure-3. Hence the bottom portion is subjected to tension and top to compression. This will demand, tensile reinforcement in the bottom of the slab ( i.e for the tension face).

Fig.3.Pressure distribution under the footing placed over sand, clay and uniform distribution respectively

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