After the construction of a house is complete, many times homeowners experience various problems due to poor design or poor construction practices or both. Differential Settlement of foundations is one of the most frequent of these. It can cause so many unpleasant effects such as small hairline cracks on the plaster, door frames getting out of place and doors not closing, beams cracking… In extreme cases, it can bring the structure to the point of imminent collapse. Differential settlement can happen in any type of structure, and not just houses.
How can this be prevented? Both design and construction practices are important, in order to prevent differential settlement of foundations.
First of all, the soil must be analyzed properly by a qualified geotechnical consultant, and the foundation system must be designed per his recommendations, by the structural engineer. This means having a good geotechnical report in hand, in the first place. This report includes soil type and ground water table considerations at a minimum.
Loads that are transferred from the structure to the ground, and the foundations that can take that load, without causing settlement above tolerable limits must be known.
Not only the bearing capacity of the soil is considered, but the calculations must be done so as to limit the settlement, which is the determining criteria.
If the results dictate that the individual footings be too wide, then all of them can be combined in a single mat foundation.
Depending on the soil and loads, piles can also be used if shallow foundations will not be adequate.