Slab on Grade Foundation

What Is Slab On Grade | Grade On Slab Foundation | Slab On Fill vs Slab On Grade | Slab on Grade Foundation vs Crawl Space

What Is Grade On Slab?

The Slab On Grade is defined as a directly laid on the earth surface for supporting the structural elements and walls.

The minimum thickness of grade on slab is depending upon the soil characteristics and porosity and generally 4 inches thickness is considered on the grade of slab. The slab on grade is also known as a floating slab.

Slab on Grade is popularly used in that area where the ground doesn’t freeze. These types of slabs may or may not use reinforcement on them and the decision of inserting or using reinforcement is depend upon the local building codes and floor loads.

For safety purposes, a layer of bitumen and gravel is laid on the earth surface before laying the concrete slab for preventing moisture into the slab.

Also, this type of slab is directly prepared on the ground level or earth level, slab on grade is acts as a foundation for any structure or building. Which does not require a further type of footing.

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Construction of Concrete Slab On Grade

Before the construction of grade on a slab, initially excavated the earth up to the required depth and compact the earth surface to remove air voids from the surface.

Batters are placed in position as per plan before pouring the concrete in it and this board act as a mould which helps to identify the corners of the slab

Soil investigation is done then design to a thickness of the slab as per investigation result and another layer of bitumen and gravel is poured in the earth surface.

This gravel and bitumen layer acts as a sub-base layer for the concrete slab. This is preventing the entry of groundwater into the slab.

The pouring of concrete is thicker at the edges of the concrete slab, and that is acts as a footing and also reinforcement bars are provided in the edges for strengthening purposes.

To minimize the cracking problem used control joint I the slab and also expansion joint is placed between the slab and wall, for curing the stress action in the hightemperature period.


Types of Grade on Slab                    

The following two types of grade on slab are described below,

1. Supported Slab on Grade                                        

2. Monolithic Slab on Grade                             

1. Supported Slab on Grade

Supported slab on grade is as the name suggests this slab support the already having traditional footing on the field or site.

Supported grade on slab also acts as a moisture barrier and an expansion joint is provided between the wall and concrete slab for relieving the stress during the high temperature period.

In support grade slab used control joint to control cracking on the surface also help to raising the column.

2. Monolithic Slab on Grade         

In Monolithic slab on grade is does not have any traditional footing but this concrete slab is acting as a footing for the building, walls and column.

This type of grade on slab foundation is framed by providing batter boards around the slabs. These batter boards are helping to identify slab corners because they act as a mould.

What Is Slab On Grade | Grade On Slab Foundation | Slab On Fill vs Slab On Grade | Slab on Grade Foundation vs Crawl Space
Slab on Grade

Grade on slab is usually rested on the layers of bitumen (moisture barrier) and gravel, which is preventing to the entry of water into the slab.

The perimeter or edge of the slab on grade is thicker than the rest of the slab surface, this thicker portion works like a mini footing and also help to distribute the overload on the large area of the ground.

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Advantages of Grade on Slab Home

The Advantages of Grade on slab home is listed below,

  • Grade on slab is an inexpensive competitively doing a crawl space under a structure or full basement under a structure.
  • Grade on slab is sturdy in nature, the building or structure is directly resting on the poured concrete and it is not rely on the supports and beams to sustain the building.
  • Slab on grade foundations are excellent for flooring in a garages, barn and shed.
  • Grade on slab foundation does not have a termite attack problem.
  • In Grade on slab foundation excavation cost, labor cost and forms are at a minimum.
  • Construction speed is high.

Disadvantages of Grade On Slab

The Disadvantages of Grade on slab is listed below;

  • Grade on slab foundation in high chance to settle down the foundation.
  • In Grade on slab is creating a problem when extending the building.
  • Difficult to check the lines periodically.
  • In Grade on slab does not having an access for utility lines such as gas line, pipe line and cable, etc
  • Slab on grade is located in low profile elevation so that high chance to flood even in moderate rains.

Read More: What Is Concrete Edging | Types of Concrete Edging | Concrete Curbing | Concrete Garden Edging


Slab On Fill vs Slab On Grade    

 The difference between Slab On Fill vs Slab On Grade is as follows,

Slab On FillSlab On Grade
Slab on Fill is also known as Concrete slab. It is one type of grade on slab.Slab on grade is also known as Floating slab foundation.
Slab on fill layer is made up of a mixture of broken stones, masonry, and concrete.Slab on Grade is made up of the layer of Bitumen and gravel.
It is built over soil or aggregate layer.Built-in a grade surface or slightly dug in.

Slab on Grade Foundation vs Crawl Space

The difference between slab on grade vs crawl space foundation is as follows,

Slab on grade foundationcrawl space
Slab on grade foundation is raised slab that the house is built over it.Crawl space foundation is a concrete wall that is exterior support the interior walls and beams.
Construction of slab on grade foundation is inexpensive.Construction of Crawl space is more expensive.
Construction takes a shorter time.Construction takes a longer time.
Slab on grade foundation is more energy efficient.Crawl space is less energy efficient
The slab on the foundation is not suitable for floodprone areas.Crawl Space is good for floodprone areas.
Slab on grade is less accessible for gas lines, Plumbing lines, and cable lines.Crawl space is more accessible for gas lines, Plumbing lines, and cable lines.

FAQs:

What is the grade on slab?

The grade on slab is defined as a directly laid on the earth surface for supporting the structural elements and walls are called grade on slab or slab grade.

What are the types of Slab on grade?

The following two types of grade on slab are described below,
1. Supported Slab on Grade    
 2. Monolithic Slab on Grade                                                              

What are the advantages of Slab on Grade?

The Advantages of Grade on slab is listed below;

  • Grade on slab is an inexpensive competitively doing a crawl space under a structure or full basement under a structure.
  • Grade on slab is sturdy in nature, the building or structure is directly resting on the poured concrete and it does not rely on the supports and beams to sustain the building.
  • Slab on grade foundations are excellent for flooring in a garage, barn, and shed.
  • Grade on slab foundation does not have a termite attack problem.
  • In Grade on slab foundation excavation cost, labor cost and forms are at a minimum.
  • Construction speed is high.
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