Two kinds of ground in one county
The Handbook of Texas says the Balcones Escarpment crosses Bexar County, and that the northwest corner, about one-eighth of the county, lies up on the Edwards Plateau. Everything in the story of a San Antonio foundation starts at that line.
| Part of the county | What’s in the ground | What it means for a foundation |
|---|---|---|
| North side and the Hill Country edge | alkaline soils over limestone, per the Handbook of Texas; the NRCS general soil map says Edwards Plateau soils such as Tarrant, Brackett, Eckrant and Real are shallow to limestone | Less clay to swell, but rock close to the surface, hillside lots and fill pads that settle unevenly |
| Middle and east of the county | A central strip of Blackland Prairie; Houston Black clay | The classic Texas heave-and-shrink soil: the biggest seasonal movement |
| Far south | Loamy surface layers over loamy to clayey subsoils | Moderate; varies lot to lot |
The clay is the reason most San Antonio foundations move. The NRCS general soil map says the shale under the Blackland Prairie produced high shrink-swell properties. The USDA’s official description of Houston Black adds that it has high shrink-swell potential, and a Texas licensing bulletin gives the mechanism: heave when wet, settle when dry. Volunteers with the Texas Master Naturalists go further: they say the clay’s swelling and shrinking is the primary reason for foundation issues in Bexar County.
Droughts that last, rain that arrives in one afternoon
Rainfall is the other half of the story. The Handbook of Texas gives Bexar County an average of 31 inches a year, but the average hides the swings:
- Dry years. The National Weather Service’s records, which start in 1885, put the driest year at 10.11 inches in 1917 and the second driest in 2022, at 11.51 inches.
- Wet years. The wettest was 1973, with 52.28 inches.
- Single days. 11.26 inches fell in one day in October 1998.
Clay that dries and cracks through a long summer lets the edges of a slab drop. A soaking fall swells it back and can lift the edges. Repeated year after year, that is what cracks brick and racks door frames. The aquifer under the city tells the same story: 612.5 feet was the record low at the J-17 well, set in the 1956 drought.
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San Antonio’s houses: older than Texas average
San Antonio proper is older than its suburbs. The Census Bureau puts the median home’s construction year at 1985, and 43% of the city’s homes were built before 1980, compared with 36% across Bexar County and 33% statewide. 31% date from 2000 or later.
That age shows in the foundations you see. Most Texas houses are slabs, which ASCE’s Texas Section calls slab-on-ground. But San Antonio also has a lot of raised-floor houses. The City’s Office of Historic Preservation says many historic houses in San Antonio have pier and beam foundations. The pier and beam page covers those; the slab page covers the rest.
Repairs a contractor may propose
- Slab foundation repair: piers set below the active clay at the sagging beams, then a lift toward level.
- Pier and beam repair: shims, added piers, new beams and a drier crawl space.
- House leveling: what a lift can and can’t do, and when it’s worth it.
- Drainage and soil moisture: gutters, grading and drains that keep the clay’s moisture even.
- Slab leaks and plumbing tests: finding out whether a pipe under the slab is part of the problem.
- Inspections and engineers: a walk-through, elevation readings and an independent second opinion.
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What foundation repair costs around San Antonio
Local contractors publish ranges, and they disagree. These are claims, not quotes, set beside national guides for scale:
| Item | Published figure | Source |
|---|---|---|
| Repairs in San Antonio, overall | $300–$30,000+ | Ram Jack (contractor) |
| Typical repair, San Antonio | $5,000–$7,000 | G.L. Hunt (contractor) |
| Average repair, San Antonio | $7,000–$15,000 | StoneHouse (contractor, 2023) |
| Steel pressed pilings | $1,500–$3,000 per pier | Ram Jack (contractor) |
| Foundation repair, national average | $5,166 | HomeAdvisor |
| Foundation inspection | $300–$750 | HomeGuide |
One San Antonio contractor says it plainly: there is no single number, because the price depends on how many piers a slab needs. The cost page goes line by line through what a quote can include.
Signs worth a closer look
Texas inspectors and engineers treat these as signs a foundation may be moving:
- doors that bind or don't latch, especially near the middle of the house
- diagonal (stair-stepping) cracks in brick near outside corners
- sloping floors you can feel underfoot
- frieze board separations where the wall meets the roofline
- walls separating from ceilings or floors
The Foundation Performance Association adds a caution: not all distress is foundation movement. The warning signs page lines up each sign with what else can cause it.
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How inspection and repair work
- Inspection: a walk-through inside and out, with floor elevation readings.
- Written plan: pier count, locations, method and price.
- Engineer and permit: in San Antonio, a licensed engineer designs or guides the repair and signs the paperwork the city asks for.
- Repair: piers, the lift, and a plumbing test if the plan calls for one.
- Records: after-repair readings, the permit, the engineer’s letter and the warranty terms, which a buyer will ask for.
San Antonio’s permit rule
The city’s Development Services Department publishes one bulletin that settles the question, and none of the contractor sites we read mention it.
| Question | City of San Antonio (Information Bulletin 172) |
|---|---|
| Who designs the repair? | Repairs must be designed by or under the guidance of a licensed professional engineer |
| What goes in with the application? | An Assumption as Engineer of Record Letter, signed and sealed |
| What clears the inspection? | The Engineer's Inspection Letter, accepted only from the engineer of record |
| Who can apply? | owner or City-licensed Residential Building Contractor |
| What if work starts first? | A double fee for starting without a permit |
Ask every contractor who pulls the permit and who the engineer of record is. The permit guide compares San Antonio with Schertz, New Braunfels and Helotes.
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Watering under SAWS rules
Steady soil moisture slows the swings, and the San Antonio Water System’s rules decide how you can supply it. They track the Edwards Aquifer: year-round rules apply while it stands above 660 feet above mean sea level, Stage 1 starts when it falls to 660 feet above mean sea level, and Stage 3 at 640 feet above mean sea level. In Stage 3 a hand-held hose is allowed any time on any day, while a soaker hose is limited to once a week. The watering guide has the details.
Before you sign a repair plan
Texas doesn’t license foundation repair contractors; a state Senate bill analysis found no state regulation of foundation repair contractors (2011). The plan, the permit and the contract are what protect you:
- Get more than one bid, in writing. The Texas Department of Insurance suggests at least three bids.
- Ask for the elevation readings behind the plan, and a drawing with every pier marked.
- Read the warranty: what it covers, for how long, and whether a buyer can take it over.
- Don’t sign a contract with blanks in it, and be wary of a large or full down payment.
- On paying in full, the Attorney General’s answer is not until the work is complete and you have inspected it.
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Areas we cover
Beyond the city itself, New Braunfels sits where the Blackland Prairie meets the Balcones Escarpment, Schertz straddles three counties with its own permit PDF, and Helotes sits in the northwest corner of Bexar County on the limestone side.
Who does the work
Calling or sending a request reaches the foundation contractor who serves your part of Bexar, Comal or Guadalupe County. They set a time, inspect the house and hand you a written plan and price. Work is done by independent local contractors. Pricing and availability are set by the contractor serving your area.