In certain areas soil of poor quality can be found and in order to build on it, the soil must be
altered. This can be done by means of stabilization or modification of the soil or one can replace
the poor quality soil with good quality soil. This soil improvements or replacement of the soil will
have an impact on the construction cost therefore one should consider various options like the
cost of stabilization versus the replacement of the poor quality soil.
If soil improvements or replacement of the soil are ineffective, impractical or too expensive;
foundations can be used either alone or in combination with the soil improvements. The most
basic types of foundations are spread footings and strip foundations and are mostly and
effectively used in good, stable soils. Other foundation types like pad foundations, raft
foundations and piling foundations are more complex foundation types and are mostly used
where the soils are of poor quality or unstable.