Several things contribute to the frequency of foundation issues in Marietta. We’ll discuss each of these in-depth below, as well as the likely culprit of each.
“Georgia red clay” is the name given to the predominant soil in Georgia, which is characterized by an abundance of clay and a comparatively small concentration of silt and sand particles. The ground in Georgia may be ideal for agriculture, but it creates a wide array of problems for home foundations built on top of it.
The first issue with the soil is that it expands when it gets wet. Clay particles are tiny, and the voids between them leave plenty of room for water absorption.
When the earth around your Marietta home gets saturated with runoff, the soil swells and places lateral pressure on your concrete block walls and upward pressure on your slab. The stress can become too intense for the concrete to withstand, resulting in the formation of large cracks and structural damage.
The clay-rich soil also shrinks when it dries, sometimes causing the earth to pull away from your foundation. This type of movement occurs under all foundations, but it’s more intense and rapid in Marietta because of the abundance of clay. If the drainage on your property is at all uneven, differential settling can occur.
Uneven settling can cause areas of your foundation to sink further into the ground than the rest of your home. Concrete can flex slightly with changes in pressure, but eventually, your slab will crack, and your home’s structural integrity will be compromised.
The last issue is caused by Marietta’s clay soil ability to retain water for long periods. Runoff can be forced against the concrete for many days following precipitation, which leaves your home prone to water damage and moisture build-up, both of which can be damaging to your crawlspace, basement, and living area.
Above-Average, Year-Round Precipitation
Marietta receives nearly 50 inches of rain each year, about 50% higher than the national average. The above-average rainfall makes the problems with Georgia’s expansive soil significantly more dangerous. The ground gets saturated more frequently, causing the earth to swell and place excessive pressure on the concrete beneath your house.
Additionally, the abundant runoff increases the risk of water and moisture problems.
To make matters worse, the rainfall in Marietta occurs regularly, averaging about two days per week for the entire year. The soil can only swell so much in response to precipitation, but the constant rainfall does contribute to water intrusion and humidity accumulation under your home.
Tropical Storms and Hurricanes
Marietta is located inland, but residents still see the effects of hurricanes and tropical storms during hurricane season, which lasts from around June to November. The rainfall during these months is a bit higher in frequency and volume than the rest of the year.
The more concentrated precipitation leaves Marietta and the neighboring cities at greater risk of flash floods, primarily because the significant runoff drains very slowly through the dense clay soil.
Flooding not only contributes to ground swelling and excessive hydrostatic pressure on your concrete, but it also increases the chances of water or water vapor entering your home and causing damage.
Lastly, much of Georgia is underlain by limestone bedrock. Limestone is problematic as a support for your home’s foundation because it dissolves in the presence of water. Runoff and groundwater can erode the bedrock over time, leaving empty caverns and waterways in the wake of draining water. This underground erosion is referred to as karst, and it can contribute to differential settling.
The compacted soil above the voids in the bedrock can collapse, creating instability in the ground that eventually affects the surface in the form of sinkholes. If the karst is situated under or near your home, your foundation can lose support from the earth below and settle further into the ground. This often results in a loss of structural integrity and requires significant stabilization.