How Can Soil Support Concrete?

Most homeowners might not believe that something as simple as soil can actually bear the weight of concrete slabs. Let’s take a closer look into how contractors use soil as support for these heavy slabs below.  

• Soil Type 

Contractors will typically take two things into account before building on a specific piece of land: the type of soil in the surrounding area and how many layers of soil they will need to dig through for the best support. Typically, the best soils to build on are those that are already compacted together. Compact soils are able to bear larger weights without the contractors having to dig too far for extra support. However, this does not mean contractors will not build on looser soil types. 

The soils near Rush City, Minnesota, for instance, are much sandier and less compact than the richer loam soils of North Dakota. Contractors will take every type of soil into account before building. This means that the supporting soils in Rush City might need extra layers built on top to provide more adequate support for the heavier concrete slabs it will carry over it  

• Soil Layers 

The layers of the native soil in an area are also important for contractors. The topmost layer, also known as the subgrade layer, is typically the only layer a contractor will need to settle down the concrete slabs over. However, if this layer is too loose to provide adequate support, then the contractor will have to dig deeper to find a better bedrock of natural support. 

Contractors may also decide to create an artificial layer made up of hardy gravel. This is known as the subbase layer and is typically used to absorb or slow down the flow of groundwater from welling up and washing the rest of the loose soil away. If the subgrade layer is especially loose, they may add even more base layers to the area to create a stable foundation to build upon.