How Expansive Clay Soil Affects Manassas, VA Homes

Both soil erosion and soil swelling can change the way that your soil can support your home structures. With soil erosion, water or wind washes soil levels to lower than normal, which can be very problematic for your home. For instance, when soil gets washed away underneath concrete beds, this can leave voids, or gaps, which can cause your concrete to crack or sink—given enough time. Depleted soil levels can also invite rainwater and melted snow deeper underground, thus, increasing the likelihood that water will encroach upon your crawl space, basement, and foundation. Water entering any of these areas can lead to cracks, rotted wood, leaks, and potential floods.

Repeated swelling and shrinking of sandy clay soil particles can also cause similar problems in your home. Aside from causing concrete to crack or sink or water damage to your home space, swell-shrink cycles of sandy clay soil can also result in 2 common phenomena known as the Clay Bowl Effect and Hydrostatic Pressure. Both phenomena are caused by weakened soil that allows water to accumulate in large volumes around homeowner’s crawl spaces, basements, and foundations. Although drastic damage takes a significant amount of time to form from either the Clay Bowl Effect or Hydrostatic Pressure, you still want to be protected as soon as possible to prevent major problems. 

In order for your house to be built, contractors must excavate the earth to form a hole in which they can work. After completion of your home’s foundation and basement, this hole is refilled with surrounding soils. However, this soil is a lot weaker than the denser, untouched soil and, as a result, absorbs water much more readily, forming a “clay bowl” of water directly surrounding your house. The Clay Bowl Effect can actually pave the way for hydrostatic pressure, or pressure by large quantities of water upon your home structures. Hydrostatic pressure is quite common around basement and foundation walls, where it causes them to buckle or bow inwards.

The red clay soil that is found through much of Northeast NC is iconic. It is rich, fertile, and has many strengths. Unfortunately, it can also present a number of challenges to homes and structures that are built on it, especially during the stormier seasons of the year. This is because clay soils are expansive and water reactive in nature, and can become quite unstable when they are extremely saturated or dehydrated. Of course, many parts of Northeast NC also have the state soil (Cecil soil) that is far less reactive, but also has some limitations and weaknesses.

In fact, almost all soil has some weaknesses to consider. This is why contractors often seek to build in areas that have balanced, mixed soil. While expansive soils can be strong, you see, they are changeable. Keeping them stable requires careful and consistent moisture management around a home. If the soil becomes very saturated, it will swell and become soft and marshy. This can lead to subsidence and even heaving in concrete surfaces and structures.

If the soil becomes very dehydrated, however, it will shrink and become brittle. While prolonged droughts are rare in Northeast NC, they can happen. When they do, the soil can recede and crack quite dramatically. This leads to an issue known as settlement, whereby a foundation fragments and sections of it fall into the voids left in the earth. This destabilizes a property, and when the drought breaks, it will let water seep into your home.