Expansive Soil and Your Home Foundation

Expansive Soil and Your Home Foundation

Did you know that the soil your home is built on could have a significant impact on the long-term health of your home foundation? In order to avoid any necessary foundation repairs, it’s important that as a homeowner, you have a general understanding of potential soil-related foundation issues, how to spot them early, and how to address any foundation damage.

While there are a variety of soil-related foundation concerns, we will focus on the definition, cause, and signs of expansive soil, a common source of structural issues that can be addressed with the appropriate foundation repair.

What is Expansive Soil?
Expansive soils are soils that expand and shrink, depending on the soil’s moisture. If a fluctuation of the soil’s moisture is present, an expansive soil heave, or otherwise commonly known as a differential heave, can occur.  In technical terms, an expansive soil heave will occur when the confining pressure of a building does not exceed the pressure exerted on the building by the expanding soil

What Causes an Expansive Soil Heave?
Although environmental circumstances, i.e. flooding, may seem like the primary cause for an expansive soil heave, it’s important to consider, prepare, and respond to the other potential causes of an expansive soil heave. Below, we have identified a few common causes of expansive soil heaves. While it’s imperative for homeowner to actively monitor their foundation and be aware of these potential causes of an expansive soil heave, a professional engineer may be necessary to conduct a soil test and recommend any necessary foundation repairs.

Potential Causes of an Expansive Soil Heave:

  • Rise and fall of the groundwater table with the seasons
  • Unusual rain, drought or humidity
  • Plumbing leaks
  • Site drainage and irrigation

In addition to observing these potential causes of an expansive soil heave, homeowners should be aware of other factors such as a graded property side or damaged gutter system.  These are important because, for example, if the property site is graded towards the foundation or if the gutter system is not intact, water might pool near the foundation. This pooling means that the moisture content of the soil around the home will not be uniform and an expansive soil heave may occur.

Common Signs of Expansive Soil Heave
Homeowners can typically spot an expansive soil heave if they observe that their floor elevation has a “hump” or “mound” in the middle of the floor. Another common sign of expansive soil heave is if you notice a cracking or lifting of the floor slab in a two-car garage.  If active soils are present, homeowners may observe that the high point of the garage slab has shifted to the mid-point of the garage door opening, where the loading is the lightest.

What to Do if You Notice a Potential Expansive Soil Heave
If you are a homeowner and are concerned about potential expansive soil heaves, it’s recommended that you contact an independent foundation engineer who can conduct a proper site analysis and recommend a foundation repair plan any for your home.

Photo Credit: Lee Haywood