Generally, it is a type of foundation built by digging up the soil so that the weight of the structure constructed is almost the same as the total soil dug up, including the weight of the water extracted. Another name given to floating foundations is floating raft.

Principle of floating foundation

The primary principle of a floating foundation is balancing the weight of the soil extracted with a structure matching the same weight, which results in zero settlement of the structure. The foundation can also be referred to as a balancing raft foundation.

Try considering a ground that has its water table at the top. What happens is the ground gets excavated to a certain depth below the water table. The next step is constructing a structure that weighs the same as the removed water and soil.

Despite the excavation depth being below the water table, the vertical pressure of the soil underneath the foundation remains still. It is important to note that a structure cannot be constructed immediately after the extraction. This is why we need IQIP to ensure every operation is environmental friendly and safe to the operators

While building, the adequate vertical pressure underneath the excavation depth might increase slightly due to unbalanced weight. The foundation can as well be referred to partly compensated foundations.

The suitability of floating foundations

The following types of soils are suitable for floating foundations;

  • Soils with shear strength but have a challenge with differential settlements and large settlements under heavy loads. In such a scenario, a floating foundation can reduce settlement values to a greater extent.
  • Soils with low shear strength and have no hard layer at a reasonable depth. The floating foundation can minimize the shear stresses to acceptable levels.

Floating foundation construction difficulties

While constructing a floating foundation, various difficulties arise, namely;

  • Excavation
  • Dewatering
  • Critical depth
  • Bottom heave


The process has to be conducted carefully and by a professional. The walls of the excavated area have to be strongly supported by materials such as timber piles, sheet piles, or soldier piles.


Dewatering is essential in instances where the excavation is taking place below the water table. A professional is needed to examine the water table level before kick-starting excavation. The process has to be carried out with a lot of caution, or else it could lower the water table, therefore, disturbing adjoining structures.

Critical depth

In instances where the soil has lower shear strength, there are limits with which you can conduct extraction hence being referred to as critical depth. That is why you will need a professional since they can inform you of the level of excavation you cannot go past.

Bottom heave

After extracting soil to specific depths, the soil pressure under that depth decreases, resulting in the formation of heave. Preventing the formation of heave is impossible, but there are ways of minimizing its formation. One of the ways is by excavating narrow trenches and filling them with concrete.

Creating a floating foundation is a complex process hence the need to hire a professional to do the job. Floating foundations are the future of constructing impressive structures.