Building structures fail because there is a failure already in the foundation. It is always advisable to get it right at the first time than seeking for a remedy when the unexpected happens.
Getting it right the first time is by far cheaper and less stressful than seeking for a remedy when the unexpected happens. Nothing can be used to compare a quality foundation that can comfortably carry a superstructure despite the cost.
In some instances, the cost of a foundation can triple that of the superstructure itself especially in reclaimed lands, lands where mining has taken place, clayey soils, lands previously used for refuse dump, etc.
Fig 1: A failed fence caused by soil heaving.
Foundations fail because of the differential settlement of the soil upon which it was built. This in turn leads to the failure of the superstructure.
The following can lead to increase in settlement
1. Very loose soils
2. Highly shrinkable soils
3. Reclaimed lands
4. Areas where mining is taking place
5. Abandoned mines.