Slab on Grade Foundation

What is Slab on Grade Foundation

You would know that one of the most important design considerations while constructing a house is its foundation. Slab on grade or ground foundation is a design of foundation that involves pouring of concrete slabs directly on the ground, meaning there is no gap between the ground and the concrete. Slab on ground foundations are the preferred kind of foundations under these conditions:

  • These are frequently employed in warmer climates as there is no issue of freezing and thawing of the ground. This eliminates the requirement of having provision for heat ducts beneath the floors.
  • Very often they are used in areas comprising of clay soil.
  • Slab on grade foundations are usually used for tract homes or when constructing buildings quickly with a low budget.
  • This type of foundation is very suitable for sheds, garages and barns to get a strong floor without making any substantial expense.

This kind of foundation allows for the distribution of load placed on it. For instance, load-bearing walls that are not provided with some kind of a foundation to rest upon, would sink into the soil to some level and respond to any movement of the soil. That makes it imperative to properly prepare the soil before pouring concrete. It needs to be leveled and overlaid with gravel and moisture barriers. There are quite a few factors needing consideration for deciding the thickness, including the likely load that the slab would need to bear. While it is true that on opting for slab on grade foundation for constructing your house, you do not get any space below the foundation that could be used for residential and or storage purposes, the amount of money you save makes it worthwhile.  So, do not get discouraged by the preparatory work that is essentially needed for slab on grade foundation.

slab on grade foundation
slab on grade foundation vs others


  • Having poured the concrete, you just need to get it polished to get a finished floor that is highly durable and energy-efficient at a very low cost. The expense is substantially lower than having a full basement or even a crawl space as labor expense and cost of forms and excavation is very low. Another factor for the reduced expense is shorter period for completion of such foundation.
  • It is very sturdy as the building rests directly on poured concrete and not on beams or other supports.
  • Because in case of this kind of foundation there is no wood coming in contact with the ground, the chances of your house getting infested with termites are almost eliminated.
  • Because of their cost-effectiveness, concrete slab foundations are ideal for tract homes. They are great for flooring of sheds, barns and garages.

Well, despite all the advantages that slab on ground foundations offer, they do have some disadvantages. Here are the limitations of such foundations:


  • They do not provide any access to the area below the slab for utility lines and other important cables. It means all electrical and plumbing lines should be positioned beneath the surface of the foundation or within the building. Tight conduit needs to be used for pulling wires and cables with provision for replacement when repairs are needed.
  • Heat loss is quicker when the ground temperature falls below the temperature within the building.
  • Floods may be a matter of concern if the location of the slab foundation is at a low elevation because the building may get flooded easily when it rains.
  • Usually, it is not practical to get the building extended as it is resting on a poured concrete slab.
  • Slab on grade foundations would settle in due course of time and may create problems concerning the reliability of the building.
  • Water and natural gas lines laid at the time of pouring slab will ultimately break down over time, making their replacement necessary. There is no way to check the pipes periodically, meaning you have to be vigilant for any signs of leakages like wetness on the floor, drop in water pressure, and external walls getting discolored.

These factors along with the kind of soil need a careful assessment while considering slab on grade foundation.

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