If the soil conditions immediately below the structure are sufficiently strong and capable of supporting the required load, then shallow spread footings can be used to transmit the load. On the other hand, if the soil conditions are weak, then piles or piers are used to carry the loads into deeper, more suitable soil.
Design Considerations:
Must not settle excessively.
Must be placed at depth sufficient to prevent damage from surface environmental effects (frost, swelling and shrinkage, erosion and scour).
Must not cause failure of supporting soil (Bearing Capacity criteria).
Advantages of using shallow foundation
Cost (affordable)
Construction Procedure (simple)
Materials (mostly concrete)
Labor (does not need expertise)
Disadvantages of using shallow foundation
Settlement
Irregular ground surface (slope, retaining wall)
Foundation subjected to pullout, torsion, moment.
Shallow foundations are foundations where the depth of the footing ( ) is generally less than the width (B) of the footing. Deep foundations are foundations where the depth of the footing ( ) is greater than the width (B) of the footing.
) is generally less than the width (B) of the footing. Deep foundations are foundations where the depth of the footing ( 
) is greater than the width (B) of the footing.
