Types of shallow foundation

A shallow foundation is one whose depth is less than or equal to its width (generally under 3 m), and which transfers the load to the soil near the surface.

Types

1. Wall (strip) footing: Continuous footing under a load-bearing wall. Wider than the wall, with an offset, made of masonry or concrete.
2. Isolated (spread) footing: Square, rectangular or circular footing under a single column; the commonest type for RCC frames. May be flat, stepped, or sloped.
3. Combined footing: One footing carrying two or more columns; used when columns are close, or one is near the property line.
4. Strap (cantilever) footing: Two isolated footings joined by a strap beam; an edge column's eccentric load is balanced.
5. Raft (mat) foundation: A thick slab under the whole building. It is used for soil of low bearing capacity or where isolated footings cover more than about half the area.
6. Grillage foundation: Steel beams in layers (crossing) embedded in concrete, to spread heavy column loads over low-capacity soil, with shallow depth.
7. Stepped foundation on sloping ground for walls.
8. Inverted arch footing for soft soil between piers.

 Wall footing         Isolated footing       Raft
   |wall|               | col |            ___________
  [_____]              [_______]          |___________|