Last reviewed 16 Sept 2026 · 6 min read
Purpose and types
A footing spreads the concentrated column or wall load over a larger area of soil so that the soil pressure stays within the safe bearing capacity (SBC) and settlement is acceptable.
| Footing | Use |
|---|---|
| Wall (strip) footing | Continuous strip under a load-bearing wall |
| Isolated (pad) footing | Single column; square, rectangular or circular; flat, stepped or sloped top |
| Combined footing | Two or more columns close together, or a column near the property line |
| Strap (cantilever) footing | Two isolated footings joined by a stiff strap beam to balance an eccentric boundary column |
| Strip footing under columns | A row of columns on a continuous footing |
| Raft (mat) foundation | Whole building on one slab; for weak soils or heavy loads where footings would cover > about 50% of the plan |
| Pile cap | Transfers column load to a group of piles |
Sizing
Area required uses service (unfactored) loads:
Self-weight is commonly taken as 10% of the column load for a first estimate. Choose convenient dimensions ≥ .
For structural design use factored loads and the net upward pressure (self-weight of the footing does not bend the footing since it is supported directly by the soil beneath):
IS 456 provisions for footings
- Thickness at the edge: not less than 150 mm for footings on soil (300 mm above the tops of piles for pile caps).
- Bending moment is taken at the face of the column, pedestal or wall (for a masonry wall: halfway between the centre line and the edge of the wall; for a steel column with base plate: halfway between the column face and the edge of the plate).
- One-way (beam) shear: at a distance from the face of the column.
- Two-way (punching) shear: on a perimeter at from the column face; with and .
- Development length of bars must be available from the critical section for moment.
- Minimum cover: 50 mm.
- Minimum steel: 0.12% (HYSD) as in slabs.
Distribution of steel in rectangular footings
- Long direction: spread uniformly across the full width.
- Short direction: a central band of width equal to the short side of the footing gets
The rest is spread uniformly in the outer portions.
Transfer of load at the base of the column
Compressive stress at the column–footing interface must not exceed the permissible bearing stress:
= supporting area (largest area of the footing geometrically similar to the column and concentric with it, within the footing); = loaded area (column). If exceeded, provide dowels (starter bars) or extend column bars into the footing; dowel area at least 0.5% of the column cross-section and at least four bars, extending the development length into both members.