Homeowner Guide
San Antonio Soil & Foundation Guide
A practical, San Antonio-specific explanation of why slabs move here and how to respond -- backed by official sources.
Why do so many San Antonio homes have foundation problems?
Many homes in the San Antonio region sit on clay-rich soils that shrink when dry and swell when wet. Repeated moisture swings -- especially around the perimeter of a slab -- can contribute to movement that shows up as cracks, sticking doors, and uneven floors.
What is expansive clay soil (Vertisols) in plain English?
Vertisols are clayey soils that shrink as they dry and swell as they become moist, often forming deep cracks. Engineers treat these soils as a special risk category because their volume changes can stress structures built on top -- especially when moisture changes are uneven across the foundation footprint.
What are common early warning signs?
- Drywall cracks near doors/windows
- Doors that start sticking or swinging open/closed
- Gaps between trim and wall/ceiling lines
- Floors that feel uneven
- Exterior cracks that widen over time
What actually helps before repairs?
- 1Improve drainage so water doesn't pool near the slab.
- 2Keep gutters/downspouts working and discharging away from the home.
- 3Address plumbing leaks quickly (leaks change soil moisture patterns).
- 4Reduce extreme wet/dry swings around the perimeter.
Frequently Asked Questions
Why do so many San Antonio homes have foundation problems?
Many homes in the San Antonio region sit on clay-rich soils (Vertisols) that shrink when dry and swell when wet. Repeated moisture swings around the perimeter of a slab can contribute to movement that shows up as cracks, sticking doors, and uneven floors.
What is expansive clay soil (Vertisols)?
Vertisols are clayey soils that shrink as they dry and swell as they become moist, often forming deep cracks. Engineers treat these soils as a special risk category because their volume changes can stress structures built on top.
How do I know if foundation cracks are cosmetic or structural?
Hairline cracks in drywall are often cosmetic. Wider cracks, sticking doors, uneven floors, or separation around windows may indicate structural movement. A professional evaluation helps determine whether soil expansion or settlement is affecting the foundation.
Is foundation leveling a permanent fix?
Foundation leveling corrects existing structural imbalance, but expansive clay soils in San Antonio can continue to move seasonally. Long-term stability often depends on proper drainage and consistent soil moisture management.
Will soil movement continue after leveling?
Yes. San Antonio's clay soils expand when wet and shrink when dry. Even after leveling, seasonal moisture changes can cause minor movement, which is why drainage and irrigation consistency are important.
Does homeowner's insurance cover foundation repair in Texas?
Most Texas homeowner policies do not cover foundation settlement caused by soil movement. Coverage may apply if damage results from a covered event, such as plumbing leaks. Policy details vary by carrier.
How long does foundation leveling take?
Most residential leveling projects are completed within one to three days, depending on pier count, accessibility, and structural complexity. Larger or more complex homes may require additional time.
Do sprinkler systems affect foundation soils?
Yes. Inconsistent watering can cause uneven soil expansion or shrinkage around the slab perimeter. Overwatering or poor drainage can contribute to movement over time.
Why do slab homes crack more during summer?
During extended heat and drought, clay soils shrink as moisture evaporates. This shrinkage can cause foundation edges to settle, leading to cracks and misalignment in slab homes.
Next step
If you're seeing multiple symptoms, get a documented evaluation. Then prioritize drainage and moisture control.