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How Expansive Soils Damage Foundations and Concrete

cracked concrete floor

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.

Soil Types, Composition, and Moisture Interaction

Foundation walls are designed to bear vertical loads, but struggle with lateral pressure from surrounding soil. This pressure varies with soil type, moisture levels, and the depth of the foundation. Backfill soil, particularly, absorbs more water, expands, and exerts increased hydrostatic pressure. If this exceeds the wall’s capacity, it can lead to cracks and bowing, and even collapse over time due to expansive clays, hydrostatic pressure, and freezing water.

Different soil types react differently to moisture:

  • Sandy Soils are susceptible to washout as water decreases their cohesiveness.
  • Clay Soils pose a significant risk to foundations. They absorb water, swelling as they saturate, and shrink upon drying, leaving gaps that allow further water penetration, leading to a damaging expansion cycle.
  • Earthy Loam Soils remain largely stable regardless of moisture levels but can erode, impacting their load-bearing capacity.

The continual cycles of wet and dry weather conditions can cause some soils to perpetually expand and contract, resulting in foundation damage.

Soil Movement: The “Active Zone”

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.

What Are Expansive Soils and How Do They Damage Your Property?

soil expansion and shrinkage

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.

dry soil

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.

Compaction from Heavy Concrete

Proper soil compaction is essential as it provides a dense, stable base for concrete. This process, often done during construction, eliminates air pockets that could cause soil collapse. Thus, pressure from heavy concrete can be beneficial, maintaining soil density.

However, excessive concrete weight can lead to over-compaction, causing the soil to collapse, especially when it’s dry and shrunken. This leads to concrete cracking and unevenness as it sinks into the overly compacted soil.

Common Signs of Damage from Expansive Soil

uneven concrete steps
  • 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.

How to Protect Your Concrete and Home from Expansive Soil Damage

Worried about soil-related damage to your home? The solution starts with us – our PolyRenewal™ polyurethane foam injections tackle concrete issues while our comprehensive foundation repair addresses foundational damage.

we at Mount Valley Foundation Service your local specialists, well-versed in the expansive soil issues that homeowners in Charleston, Columbia, Greenville, and Savannah often face. Our experienced team is ready to protect your home with knowledge, experience, and proven solutions.

Schedule a free inspection with us today. We’ll diagnose your unique problem and determine the best course of action.

Don’t let expansive soils undermine your home. Contact us now and learn more about our concrete lifting process, tailored to your needs.

Exapnsive Soil Damage FAQs

In South Carolina and Georgia, they are. Much of the soil in these states is clay-based. However, construction companies often bring in soil from separate location in order to make the land better for building. Some homeowners may be lucky and have more porous soil in their yard. However, residents of South Carolina and Georgia should always be aware that expansive soils are a likely occurrence for them.  

You can with professional help. Expansive soils are a naturally occurring phenomenon, and you can’t easily replace the soil below your home or driveway. However, solutions exist to assist with expansive soil problems. Mount Valley uses PolyRenewal™, a polyurethane injection system that removes soil from the equation al together and keeps your concrete protected from soil issues permanently.  

The concrete lifting process we employ, using high-density polyurethane foam injection, is relatively quick. The foam expands and cures within 15 minutes, stabilizing and lifting the concrete. The duration of the entire process can vary based on the size and condition of the steps. Our repairs are covered by comprehensive warranties, ensuring the longevity and durability of the solution. With proper care, the repairs can last for many years, providing both safety and aesthetic appeal to your home. 

Michael Wilcher

Michael Wilcher

Michael Wilcher is the Content Lead at Groundworks, helping us to answer all of our customers biggest questions about foundation repair, basement waterproofing, crawl space encapsulation, and concrete lifting. In his free time, Michael enjoys collecting vinyl records, watching Formula 1 Racing, and reading philosophy. He holds an MPhil from the University of Cambridge.

Disclaimer: “Concrete leveling” means the process by which cracked, uneven concrete is stabilized, and in many cases lifted, by means of PolyRenewal™ polyurethane foam. Mount Valley Foundation Services does not guarantee that PolyRenewal™ can make your concrete perfectly level. 

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