Floating Slab Foundations: Exploring the Benefits

What Is a Floating Slab?

A floating slab, also known as a float slab foundation, is a type of concrete foundation that is constructed by pouring a reinforced concrete slab directly over the soil. Unlike traditional concrete foundations, which are anchored to footings that are dug deep into the ground, floating slabs are designed to “float” on top of the soil.

This makes them a popular choice for construction projects on sites with poor soil conditions or high water tables, where conventional foundations may be difficult or expensive to install. Floating slabs can also be used as a base for outdoor structures such as sheds, garages, and patios. They are relatively quick and easy to install and can be customized to suit a wide range of building requirements.

Why Use a Floating Slab?

Floating Slab
Floating Slab

Using a floating slab foundation is considered one of the most cost-effective methods of building a foundation of a house. Normally, a strip foundation is used for house foundation construction using a frosted wall above.

Strip footings are construction lower than the frost level of the area and which is typically kept between 3 ft to 4 ft below grade level. The construction cost of strip footing and front wall construction is generally higher compared to normal foundation construction which involves a larger area to be excavated for a foundation with more concrete work and labor work required.

Read More: Floating Slab Vs Monolithic Slab | What Is Monolithic Slab | What Is Floating Slab

floating slab vs monolithic slab

A floating slab and a monolithic slab are two different types of concrete foundations used in construction. While both types of slabs are made of concrete, there are some key differences between them.

A floating slab is a concrete slab that is poured directly onto the ground, without a traditional foundation. It is typically used in situations where the ground is unstable or there is a high water table. A floating slab is not anchored to the ground, but instead “floats” on top of it, which can help prevent cracking and settling.

On the other hand, a monolithic slab is a type of foundation that combines the slab and the footing into a single, continuous pour of concrete. The slab and the footing are poured at the same time, and the footing is designed to be thicker and wider than the slab to provide additional support.

In terms of cost, a floating slab is generally less expensive than a monolithic slab because it requires less material and labor. However, a monolithic slab may be more suitable for certain types of structures, such as larger buildings or structures in areas with high wind loads or seismic activity.

Construction of Floating Slab

Construction of Floating Slabs requires details. The proposed building requires a solid and strong foundation to fully support the entire superstructure’s weight on it. As mentioned they are more commonly used in garages, and extensions to a house or shed do not necessarily require a large foundation. These buildings have less structural load compared to others.

Hence Floating Slabs are found to be most suitable and economical as compared to conventional slab construction. The main construction layers in a floating slab are shown in Figure-1. The construction includes the following steps:

1. Site Excavation for Floating Slab Construction

Site Excavation For Floating Slab
Site Excavation

The first step to being done in floating foundation construction is to clean the land and excavate the area as per the plan. This is the preliminary preparation for construction.

The step also includes creating drainage in the sides to drain water through the gravel base as shown below. The constructed trench is sealed with geotextiles and gravel as shown below, which will drain water from the concrete slab foundation.

2. Laying Gravel Base for Drainage

Install a gravel grid before pouring gravel. Add an 8- to 12-inch gravel base of various rock sizes, compacting each layer for durability.

3. Reinforcement for Slabs

Reinforcement Of Floating Slab
Reinforcement for Slabs

A slab mold is placed for the casting process. For reinforcing slabs, reinforcing bars are provided as per the dimensions and code.

4. Casted Floating Slab

Concrete is poured into the slab formwork. This compresses either my labor or a mechanical vibrator, depending on the area and workmanship. Proper compaction has to be done to make the slab fully productive. Appropriate treatment has to be taken for about 2 to 3 days.

Read More: What Is Floating Foundation | Suitability of the Floating Foundation

Advantages of Floating Slabs

Floating Slabs have the following advantages,

Floating Slab | Float Slab Foundation | Floating Concrete Slabs
Floating Slab Foundations: Exploring the Benefits 6
  • The major advantage of using floating slabs is that they can be constructed on low-bearing capacity soil. Also, where there is money investment for soil treatment to increase soil bearing capacity is too expensive.
  • These slabs have the property of spreading the vertical load or the stress on it to be distributed over a large area.
  • The floating slab is best suited when there is a need for an extension of the house area. It is very easy and cost-effective in the case of a floating slab foundation to extend the house without disturbing the existing structure of the house foundation.
  • The floating slab foundation does essential need to have a footer excavation trench. This slab can be filled with concrete only by digging and teaching in the foundation.
  • The floating slabs act as a barrier to the entry of moisture coming from the ground. It acts as a barrier between the superstructure and the ground.
  • It protects against water seepage and frost. For this purpose, the slab can be insulated from frost or moisture. This led to their widespread use in cold-field construction.
  • The layer of soil lying below the floating slab does not disturb nor will it interfere with the quality.
  • In cases, where there are changes in soil layer settlement due to heavy moisture content in the soil, the floating foundation provides the best solution.

Disadvantages of Floating Slabs

Along with advantages Floating Slab also has some disadvantages as listed below,

  • The floating slab does not provide
  • underground access for the connection lines facing the utilities.
  • It’s primitive technology.
  • Floating slab foundations have low design resonance.

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1 thought on “Floating Slab Foundations: Exploring the Benefits”

  1. Nice Article, Well described Floating Slabs, Basically, I saw using these Floating slabs in a variety of structures, garages, cottages, and sheds.

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