What is the difference between pad foundation, strip foundation and raft foundation?

Shallow foundation is commonly accepted as foundation with founding level less than 3m from ground surface. In case surface loads or surface conditions could still affect the bearing capacity, the foundation which sits on it is called shallow foundation. 

Pad foundation refers to the foundation which is intended for sustaining concentrated loads from a single point load such as structural columns. 

Pad Foundation

Strip foundation is used to support a line of loads such as load-bearing walls. For instance, closely-spaced columns render the use of pad foundation inappropriate and strip foundation may be a better alternative. 

Strip Foundation

Raft foundation consists of a concrete slab which extends over the entire loaded area so that loads from entire structure are spread over a large area leading to a reduction of the stress of foundation soils is reduced. Moreover, raft foundation serves to avoid differential settlement which otherwise would occur if pad or strip foundation is adopted. 

Raft Foundation

This question is taken from book named – A Closer Look at Prevailing Civil Engineering Practice – What, Why and How by Vincent T. H. CHU.

Mat Foundation

• A large, thick concrete slab that sustains the load imposed by a number of columns and walls.
• The method to reduce or distributed building loads in order to reduce differential settlement between adjacent areas.
• Mat Foundations are generally used with soil that has a low bearing capacity.
  

ADVANTAGES

• Good in low soil bearing conditions.
• Can distributed the building pressure over a large area, so the soil can bear the stress.
• Reducing differential settlements as the concrete slab resists differential movements between loading positions.
• Have haunches that go below the slab portion to resists punching shear from column or large concentration loads.