Types of footing and footing size calculation
Footings belong to structural components which are utilized to provide supports to columns & walls as well as transfer & allocate their loads to the soil in such a manner that the load bearing strength of the soil is not surpassed; excessive settlement, differential settlement or rotation are defended and sufficient protection against overturning/sliding is retained.
Types of footings
These types of footings are applied to provide support to the structural walls which bear loads for other floors or to provide support to nonstructural walls.
Isolated or single footings
These types of footings are utilized to provide support to single columns. These belong to one of the most inexpensive types of footings and are useful when columns are placed at comparatively long spans.
These types of footings generally provide support to two columns or three columns not situated in a row. Combined footings are useful when two columns are so adjacent that it becomes impossible to apply single footings or when one column is situated at or adjacent to a property line.
These types of footings provide support to a row of three or more columns. They contain limited width and extend under all columns.
Rafted or mat foundation
It comprise of one footing generally arranged under the whole building area. It is useful when soil bearing strength is low, column loads are heavy and as a result single footings can't be utilized, piles are applied and different settlement should be minimized.
These stand for solid slabs which are utilized to bind a group of piles jointly to provide support and transfer column loads to the piles.
Size of footing
The area of footing is measured from the actual exterior loads in order that the permissible pressure of the soil is not surpassed.
Area of footing = Total load (along with self-weight) / permissible soil pressure
Strength design requirements qu = Pu / area of footing