Floating Foundations: A Guide to Building on Water

A floating foundation is a type of shallow foundation used in construction. It is made up of a slab of concrete poured straight onto the ground without the need for any extra footings or support frameworks.

Steel bars or wire mesh are usually used as reinforcement to give the slab more strength and durability. When the soil is stable and able to bear the weight of the building, floating foundations are beneficial.

Usually, they come in handy in smaller constructions, like sheds or tiny houses. One of the benefits of utilizing a floating foundation is that you can move it if needed, and it also saves money and construction time.

You should speak with a structural engineer if you want to choose one of the best foundation types in construction.

The primary goal of a floating foundation is to achieve zero settlement in the structure by using a structure of equal weight to balance the weight of the removed (dragged) soil. It is also known as a balancing raft foundation for this reason.

What is the Suitability of the Floating Foundation?

Let’s understand why the floating foundation is appropriate:

  • For differential settlement foundation issues under heavy loads, a floating foundation is the most appropriate solution.
  • In this case, the construction of a floating foundation aids in lowering the settlement.
  • It is mostly applied to low-shear-strength soils.
  • When there are no hard or stiff layers in the soil at the necessary depth, a floating foundation can also be employed. A floating foundation lessens the shear stress force acting on the structure under such circumstances.

How to Build a Floating House Foundation?

When building a floating house foundation, you need to gather details about building on solid earth strata to fully support the weight of the superstructure.

As previously indicated, they are more frequently utilized in sheds, garages, and house extensions that don’t always need substantial foundations.

These structures have light structural elements. Therefore, when compared to a conventional or normal foundation, the floating foundation is the most appropriate and cost-effective.

Here are the steps involved in building a floating house foundation: 

  • Excavation For Floating Foundation

Clearing the land and excavating the area according to the plan is the first step in building the floating foundation. It is the first stage of the building process preparation.

  • Laying Gravel Base Drainage

To allow water to drain out through the gravel base, as seen below, this step entails creating drainage in the foundation’s sides and bottom.

As seen below, the trench is sealed with gravel and Geo-textile to keep water out of the concrete foundation.

  • Reinforcement for Floating Foundation

For the casting process, the reinforcement molds are set in place. The reinforcing bars are supplied following the dimensions, codes, and specifications to strengthen the slab.

  • Casting of the Foundation

The formwork is filled with concrete. Depending on the area and workmanship, either labor or a mechanical vibrator is used to compact it.

To fully strengthen and produce the slab, proper compaction must be carried out. After placing concrete, proper curing must be carried out for almost two to three days.

What are the Principles of Floating Foundation?

The basic idea behind a floating foundation is to use a structure of the same size to balance the weight of dragged soil, resulting in zero settlement of the building.

Thus, balancing the raft foundation is another name for this foundation. Let’s understand it in easy steps: 

  • Let’s consider the ground depicted in the figure, which has a water table at the top. Excavation or dragging of the ground or base is done up to a point below the water table.
  • In the following phase, a building equal in weight to the removed soil and water is constructed.
  • Because of its balancing weight, the total vertical pressure in the soil beneath the foundation remains constant even if the excavation depth is below the water table.
  • However, it’s important to remember that building a structure cannot happen right away after excavation.
  • Due to the uneven weight, there may be a brief increase in effective vertical pressure below the excavation depth during construction. 

Stability of Floating Foundations

The following soil types are ideal for floating foundations:

  • Even though the soils have a good shear strength, heavy loads cause more and uneven settlements, which is an issue. The floating foundation can reduce the settlement values in this situation more than anything else.
  • those soils with reduced shear strength and lacking any hard soil strata at a suitable depth. In this case, a floating foundation is preferred to prevent settlement by reducing shear stresses to a manageable level.

Advantages of Floating Foundation

When spending a lot of money on soil treatment is pointless and the site has a lower soil-bearing capacity (SBC), the floating foundation may be the best solution. We can use it over loose soil or in soil with different compressibilities thanks to this system.

The ability of the floating foundation to disperse vertical loads or stresses across a wide area causes disturbance.

For the extension of homes, a floating foundation is a good option. It works best when we need to add to a building without compromising the foundation that already exists. It won’t affect the already-constructed building structure.

High-moisture soils can be used with floating foundations. Footer trenches are not necessary when using a floating foundation. It is more cost-effective to pour them with the aid of trenching or digging. You should dig very little soil because deep footer trenches are required. It keeps frosting and water from seeping through. The foundation can be protected from moisture and frost for this reason.

A floating foundation is also most appropriate for busy highways. The earth layer underneath is not disturbed by the floating foundation, nor will it affect the quality.

The floating foundation works best in places where there is a chance of shifting in the earth layer, mostly because of high moisture content. 

Disadvantages of Floating Foundations

The footing slab prevents underground land from being accessible below ground for connection lines that face the utilities. It uses antiquated technology. The design resonance of the floating foundation is lower.

Final Thoughts!

As more research and creativity are devoted to enhancing their design and performance, floating foundations represent a promising technology for coastal development and can grow in popularity as a sustainable building and infrastructure development option on bodies of water.