How Different Soil Types Affect Building Foundations

Learn here how different soil types affect building foundations of your home

Meta: Stronger foundation leads to a stronger building. Here is how different soil types impact your foundation’s strength.

A building’s foundation provides support to the entire structure so it must be constructed efficiently and correctly. While we focus on high-quality material and the process of construction, soil supporting the foundation is often overlooked. Not all soil types are the same and the way they affect the foundation and interact with moisture varies. Below are some of the common types of soils used in construction.

Dangers Of Poor Soil

  • The soil that is not compacted and drained properly before pouring the foundation can give rise to foundational damage. Soil that expands can cause the foundation to shift, crack, and result in the growth of mold, bowing, and moisture stains.


  • Clay has small particles that can store water properly. However, when the water dries, clay shrinks significantly. Therefore clay is not an ideal option for foundations as it tends to shift over time. Clay foundations are liable to cracking and result in uneven floors. Clay soil foundations are generally kept deeper for more stability.

Drilled pier foundations are the best house foundations when it comes to clay soil, as they anchor deeper into the clay. This results in better stability. In the same way, slab-on-grade foundations resist clay’s tendency to shrink and expand.


  • Loam contains sand and slit in combination. The combination makes them great for the construction of a foundation. It is dark, soft, dry, and crumbly and is perfect for supporting a foundation.

It maintains water at a balanced rate and drains nicely. However, it must be compacted nicely before pouring the foundation.


  • Peat soil is usually found in wetlands and is dark brown or black. It consists of decaying vegetation or organic matter. It can hold a large amount of water which makes it easily compressible thus causing it to easily shift around.

During the hot summer months, it becomes extremely dry thus increasing the risk of cracks and fissures in the foundation.


  • Bedrock is referred to as the layer of rock beneath a surface layer of soil. There are different types of rocks such as sandstone, limestone, etc. All of them are an ideal option for larger buildings due to their high bearing capacity.

Bedrock does not expand and contract unlike clay and therefore it is more resistant towards water and offers greater stability. Make sure the surface is leveled before laying the rock foundation.

Sand And Gravel

  • soil types affect building foundationsSand and Gravel are good for foundations as they have the largest particles that are dry and gritty to touch and do not hold moisture. The large openings enable the water to drain quickly. When soil retains less moisture the risk of foundation shifts, non-structural and structural cracks reduces.

When compacted and moist these soils make a great option for a building’s foundation. They offer more stability because of their non-water-retaining properties. When the soil is moist, it tends to lose friction and can be washed away which might leave gaps.

Features Of A Good Soil For Construction

The properties and features of soil that make it ideal for construction are:

  • The presence of good structural and physical properties leads to stability and support.
  • Good soil should be able to hold any type of foundation constructed on it.
  • It should withstand erosion and runoff.

A soil map is used for determining these features in soil. Soil data can be accessed through soil scientists or from USDA’s website.

If you have noticed cracks in your foundation give us a call at 877-727-2259. Our experts from Crack-X will assess the damage and provide necessary foundation repairs. Crack-X is a structural repair company located in Maine and New Hampshire.

Scroll to Top