The Importance of Soil Type in Foundation Repair

So you’re doing some renovation work on your home, and for one reason or another, you notice that the walls, the crawl space, and foundations of your house are damaged and need to be repaired. Or you may have noticed that your home isn’t sitting quite right on the earth it was built on.

Let’s say you didn’t have a hand in the construction of your house, and you have no idea how it was built. What you may not know about your house and how it’s built is that the type of soil it’s standing on has a huge impact on how stable the foundations are, as well as how your house deals with moisture and times of flooding.

Understanding the interaction between your house and the earth it’s on, as well as the different types of soil your home is built on will help you repair it the best and most efficient way possible.


How does soil affect your foundations?

Before going into the different types of soil you can find, first let’s go into the science of how soil and your home’s foundations interact with each other.

To put simply, the earth your house is sitting on is made up of many different soil layers, built up over many, many years. Some of it has been put there by nature itself, while some of it was definitely dumped there by the contractors who built your home.

As the layers increase, the more the soil is able to bear the weight of the structure constructed on it. However, the hardest parts of the earth underneath it are very, very deep. What you should be more concerned about is the so-called active zone, or the layer of soil your house and its foundations are sitting right on top of. That active zone is directly affected by the weather and climate in your area, and different kinds of soil comprising the active zone will, in turn, directly affect your home.

Depending on the kind of soil in the active zone, you could experience foundation settlement in your home, or the phenomenon where the structure sinks into the earth because the soil could no longer support its weight. Foundation settlement happens for three reasons:

  • The soil dries and shrinks, cracking and collapsing from underneath
  • The soil becomes too moist and softens, becoming weak
  • The soil was not compacted enough during the construction of your home, and is too loose, also resulting in it collapsing and compressing from underneath

You obviously wouldn’t want foundation settlement to happen, as it could damage your house at the very least and destroy it at the extreme worst. We’ll go into which types of soil are more likely to do which in the next section.


The common types of soil

Here’s a list of the most common types of soil you can find in the US, from the most to the least ideal for supporting foundations:


  • Loam – The most ideal type of soil for your foundations, loam is made of a mixture of sand, clay, and silt. This mixture combined with temperate weather conditions is well-balanced and results in great moisture absorption, which is perfect for supporting your house’s foundations. The downside of loam is erosion, which may leave the soil unable to support the weight of your home and its foundations when it happens.
  • Rock – Usually referring to sandstone, limestone, bedrock, or other kinds of rock, this type is the most solid and doesn’t absorb moisture at all, making it a good material to support foundations. It just has to be properly prepared.


    • Clay – One of the most common soil types around. Clay is very expansive as it’s composed of small particles that can easily shrink or expand, making it easy to mold when wet. Here’s the thing about clay soil: you don’t want to use it for shallow foundations (when you’re adding rooms, for example) because in extreme temperatures, the soil can get either too wet, expanding the soil, or too dry, shrinking the soil and allowing more space to let water in. Clay soils commonly damage foundations.


  • Sand/gravel – Sand or gravel particles have relatively larger spaces in between them, which allows for no moisture retention. Water simply passes right through sand and it retains its volume and density. Because of this characteristic, sand or gravel is ideal for drainage systems and foundations in general so long as water doesn’t wash the soil out. The only downside is that sand or gravel is fairly hard to come by.
  • Silt – This type of soil has particles somewhere between the size of sand and clay, and it absorbs a lot of moisture. When it retains moisture, the soil swells up against the foundations, damaging them and making areas like the basement damp. Needless to say, silt isn’t really ideal.
  • Peat – This type of soil is made up of water and decomposing vegetation. Its softness obviously makes it unstable to build any foundation on, and if the soil around you is peat, you need to avoid it at all costs. Peat is usually found in wetter climates, near marshes and swamplands.


We know how to fix your foundations

If your home is in danger of sinking, we can help get it to solid ground. We can help you identify how to approach foundation repair to your home with our foundation repair services. Our foundation repair team is one of the finest in Chattanooga, and we’re ready and well-equipped to analyze the soil around and under the crawl space of your home and explain to you how we can fix it. Our services include an on-site inspection and consultation, and a proposal on how we’ll approach your soil and foundation issues.


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