How Expansive Soils Damage Foundations and Concrete

What’s beneath your home? It’s not just “ground”—it’s a complex mix of sand, silt, loam, and clay, forming the soil that your home’s foundation rests on.

The composition of this soil, and its behavior under varying conditions, is crucial to your home’s stability and the condition of your concrete. In areas like South Carolina and Georgia, the abundance of clay-based soil, coupled with above-average rainfall, can pose a significant challenge.

The impact on your property is inevitable and significant. But don’t worry, we’ve got solutions to these expansive soil issues, ensuring your home’s foundation remains robust and resilient. Welcome to our comprehensive guide on expansive soils and their effects on your concrete and house foundations.

Your home sits on diverse soil layers, each with unique thickness and properties affecting your foundation.

Formed over millennia by various forces—water, wind, glaciers, or even the contractor who built your home—these soils display increasing stability and load-bearing capacity with depth. Starting with an organic-rich surface layer ideal for plant growth, you’ll find sand, silt, clay, and loam soils as you dig deeper, culminating in a bedrock layer of rock or highly stable, compact soil.

The most critical layer for homeowners is the “active zone” around and beneath the house. Most susceptible to moisture and climate changes, it’s often the root cause of foundation problems. The active zone’s depth can range from mere feet below the surface to over 30 feet, depending on your location.

Expansive soils, such as clay, expand when wet and shrink when dry. This fluctuation causes concrete surfaces like driveways and sidewalks to crack and become uneven.

Furthermore, changes in weather and heavy loads can lead to soil compaction and shrinkage, causing concrete structures to sink due to insufficient support. These soils exert significant hydrostatic pressure on foundations when wet.

Why Soil Shrinks

Soil shrinkage, typically caused by high heat or drought, is a common issue in the Southeast, particularly in South Carolina and Georgia. As the sun intensifies, it evaporates the moisture in the soil, causing it to shrink and become brittle. This shrunk, brittle soil can no longer support the weight of the concrete above it, leading to cracks and degradation. Soil, like a sponge, needs moisture to maintain its density and strength. The damaging cycle of soil shrinking and expanding is repeated with alternating periods of rain and heat, especially during summer.

• Cracked Concrete: Expansive soils swell when wet, causing pressure that cracks concrete. As the soil dries and shrinks, gaps form, causing the cracked concrete to sink further, leading to more damage.
• Flaking, Pitting, and Staining: Cracked concrete is at risk of flaking and pitting, indicating poor condition. Moisture can cause flaking and discoloration, worsened by the soil’s expansion and contraction.
• Uneven Driveways and Sidewalks: The size fluctuation of expansive soils leads to cracks and unevenness in driveways and sidewalks, posing risks like tripping, vehicle damage, and decreased property value.
• Unlevel Concrete Steps: Steps supported by concrete can become uneven due to soil shrinkage and compaction. This can lead to a tripping hazard and lower curb appeal.