Cracked or sunken concrete in San Antonio can often be lifted with slurry or foam, sealed, ground or resurfaced. On expansive clay, timing matters: a slab that dropped in a drought may rise after rain, so fix moisture problems first. Badly broken slabs are usually replaced, and signs of foundation movement call for a structural evaluation.
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Not every cracked or tilted slab in San Antonio needs to be torn out. Depending on the cause, concrete can often be lifted, sealed, patched or resurfaced. The key is understanding why it moved. On this region's soils, the answer is often water: too much, too little, or too uneven.
Why concrete moves here
- Expansive clay. Dark clay soils, common through much of Bexar County and the Blackland Prairie to the east, swell when wet and shrink and crack when dry. Slabs ride up and down with them, and edges often drop during long droughts.
- Uneven moisture. A slab that gets sprinkler water on one side and baking sun on the other can tilt. So can one next to a leaking hose bib or a downspout.
- Loose fill. Backfill next to foundations and along driveway edges can compress over time.
- Tree roots. Live oak and other large tree roots lift walks and driveways, and they also pull moisture out of clay, which can make nearby slabs drop.
- Erosion. Heavy storms and sloped lots can wash soil out from under slab edges.
- Shrinkage and construction. Thin slabs, joints too far apart and fast drying in hot weather all cause cracking.
Repair options
- Slab lifting (mudjacking): a cement-based slurry is pumped under a sunken slab to raise it and fill voids.
- Polyurethane foam lifting: expanding foam through smaller holes lifts the slab and cures quickly.
- Crack and joint sealing: flexible sealant keeps water out of the base, which matters on clay.
- Grinding: a raised edge can be ground down to reduce a trip hazard.
- Patching and resurfacing: for spalled, crazed or worn surfaces on sound slabs.
- Section replacement: badly broken panels are cut out at joints and repoured.
When lifting makes sense
Lifting works best on slabs that are mostly intact and sank as a unit. On expansive clay, there's a catch: a slab that dropped during a drought may come back up on its own after a wet season. A contractor who knows local soil will ask when the problem appeared and may suggest waiting through a season, or fixing the moisture cause first, before lifting. Slabs that were lifted by swelling clay or roots usually can't be pushed back down and are often cut and replaced.
Fix the water first
Extending downspouts, regrading so water runs away from slabs, fixing leaks and evening out irrigation along slab edges are often part of a lasting repair. Watering schedules set by SAWS or your water provider during drought stages may affect how you keep soil moisture steady, so follow current rules.
When it might be structural
Flatwork cracks are usually not structural. But foundation movement is common on San Antonio clay. Stair-step cracks in brick or stone veneer, new drywall cracks, doors that suddenly stick, or a garage slab separating from the house can signal it. A structural engineer or foundation repair specialist is the right first call in those cases. In the City of San Antonio, foundation repair is work for a registered residential building contractor.
Questions to ask
- What caused this, and will the repair address the cause?
- Should we lift now, wait for a season, or replace?
- How will drill holes or patches look afterward?
- Is there a warranty if the slab settles again?
Have a sunken slab or trip hazard? Mark your request as urgent and request a concrete repair contractor.
See how it works
Frequently asked questions
Should I lift a slab that sank during a drought?
Maybe not right away. On expansive clay, slabs can come back up when the soil gets wet again. Fix the moisture cause and ask a contractor whether to wait a season before lifting.
Is mudjacking or foam lifting better?
Both can lift sunken slabs. Slurry lifting is a long-established method; foam uses smaller holes, is lighter and cures quickly. The right choice depends on the slab, the voids and the contractor's experience.
Are my driveway cracks a foundation problem?
Usually not. But stair-step cracks in brick, new drywall cracks or sticking doors can signal foundation movement, which is common on San Antonio clay. Have a structural engineer look.
Sources and further reading
- City of San Antonio Development Services: No Permit Required list
- City of San Antonio Development Services: Residential permits
- City of San Antonio: Sidewalk-Curb permit application
- City of San Antonio: Building and home improvement contractor registration
- City of San Antonio: Sidewalk, curb and gutter contractor license
- Bexar County Public Works: Right-of-way permits
- City of Alamo Heights
- San Antonio Water System (SAWS)
- TCEQ Edwards Aquifer Protection Program
- Texas Water Development Board: Houston Black, the Texas state soil
- USDA NRCS Web Soil Survey
- Texas 811
- Texas A&M Forest Service: Texas Oak Wilt
- American Concrete Institute (ACI)
- Portland Cement Association (PCA)