Foundation Crack Repair
Foundation Crack Repair San Antonio, TX
Seal hairline and structural foundation cracks before they spread. Epoxy injection and carbon fiber reinforcement for San Antonio homes.
Foundation crack repair in San Antonio starts with diagnosis, not a tube of epoxy. Not every crack means disaster. In this clay, cracks that grow after rain or drought cycles are movement, not age. We tell you whether a crack is cosmetic, structural, or a symptom of a dropping slab, then fix the right layer.
Injecting a still-moving foundation wastes money. The crack reopens next season. That is why every crack call starts with an elevation survey, not a one-size seal.
Types of foundation cracks
- Hairline vertical cracks: often cosmetic, still worth monitoring with photos and dates
- Horizontal cracks: soil pressure on walls. Act quickly
- Stair-step cracks in brick or block: differential settlement
- Wide cracks (more than 1/4 inch): structural movement underway
- Cracks wider at the top than the bottom: classic settlement pattern
Homeowner walkthrough: seven signs of foundation problems. Interior drywall cracks often trace to a slab failure that is not under the hallway you see. We map interior and exterior together.
The penny test and when to worry
Slide a penny into the crack. If it fits easily, or the crack is wider at the top than the bottom, schedule an inspection. Clay expands after heavy rain and contracts during drought. Cracks that open and close with the seasons signal active movement. Epoxy alone will not hold that.
Document cracks with photos and dates. Homeowners who track changes after spring storms give us the best data for repair vs monitor. Stable hairline cracks with level floors and closing doors can wait. Growing stair-step brick cannot. Why rain opens cracks: San Antonio clay soil guide.
Foundation crack repair cost in San Antonio
Price depends on whether the crack is cosmetic, structural, or a sign of slab drop requiring piering.
| Scope | Typical range |
|---|---|
| Hairline seal / monitoring | $200 – $600 |
| Single crack epoxy injection | $500 – $1,500 |
| Multiple cracks + carbon fiber straps | $1,500 – $4,000 |
| Active slab movement (piers required) | $7,000 – $15,000+ |
| Full foundation repair (if crack is a symptom) | ~$12,663 avg |
Ranges reflect San Antonio market conditions. Final price depends on inspection findings. We quote in writing before work begins.
A $500 injection today saves thousands when the slab is stable. It is wasted when the foundation is still moving. Cost context for piering vs sealing: 2026 cost ranges.
Epoxy vs polyurethane injection
Epoxy structurally welds dormant, dry cracks and restores tensile strength in the concrete. It wants a dry crack face. Trapped water prevents a proper bond. Use it on stable, load-bearing cracks that have not changed across at least two seasonal cycles.
Polyurethane expands on contact with moisture and stays more flexible. It is the right chemistry for weeping cracks, wet-season leaks, and cracks that still move a little with San Antonio clay. We inspect for water at the crack before choosing. A contractor who only sells one resin is selling inventory, not a diagnosis.
When crack repair is not enough
Epoxy bonds concrete. It does not stop a slab that is still dropping. If an elevation survey shows corners down more than about an inch, or doors stick across multiple rooms, you need slab foundation repair (piers), not just sealing. We tell you which category you are in before quoting.
Carbon fiber straps add tensile strength to bowing or cracked walls without excavation. They are not piers. If the house is dropping, straps on a moving wall are cosmetics. Straps plus injection for a stable wall. Piers when the survey says the slab moved.
Truss uplift vs foundation movement
Drywall cracks near ceiling corners, especially on interior walls, can be truss uplift: roof framing moving with attic humidity, not the slab. Different fix, different cost. We check floor level and exterior brick before selling piers for a truss problem. If floors are level, doors latch, and only ceiling corners crack seasonally, do not buy a $12,000 pier package.
DIY injection: what not to do
Surface sealants hide the symptom without bonding the full crack depth. Hardware-store epoxy on a wet, moving crack fails. Structural injection needs ports, proper prep, and pressure. DIY is fine for monitoring: pencil marks, dated photos, penny tests. It is not fine for structural cracks. Done wrong, water keeps entering and the crack widens behind the skin you painted over.
Our crack repair methods
High-pressure epoxy on dry structural cracks. Polyurethane on wet or leaking cracks. Carbon fiber where walls need tensile help without digging. Every repair includes before-and-after photos and a written warranty on the injection or strap work. Most crack-only jobs finish in a single day with minimal landscaping disruption.
Selling? Documented repair plus a stable elevation report reassures buyers more than caulk. Active movement should be fixed or priced into the sale. Stone Oak and Alamo Heights buyers will notice stair-step brick. If drainage fed the crack, we point you to drainage correction so the seal is not fighting ponding at the footing.
Interior vs exterior cracks, mapped together
The crack in the hallway is rarely sitting on the failed footing. Brick stair-steps on the north wall plus a drywall split above the front door often share one dropped corner. We photograph both, then overlay them on the elevation diagram. Repairing only the pretty interior crack is how you recaulk every spring. Targeting the exterior settlement is how the interior crack stays closed.
Horizontal cracks in block or stem walls are a pressure problem: wet clay pushing sideways. Injection without drainage is a delay, not a fix. Vertical hairlines in a garage floor that do not continue into the house slab are often shrinkage from the original pour. We still document them so a buyer does not treat them as a surprise.
How we monitor vs how we repair
Monitoring means dated photos, pencil marks at crack ends, and a recheck after the next heavy rain. It is the right call for stable hairlines with level floors. Repair means injection, straps, or piers. Mixing them up is the expensive mistake: injecting too soon, or waiting on a stair-step that grew a quarter inch since March. If you already have a year of photos, bring them. They are better than our memory of your hallway.
Carbon fiber install is a one-day wall job: grind, epoxy, strap, and a paint-ready face. Neighbors will not see I-beams in the yard. That is the point. It is still the wrong product if the survey shows the slab dropping under that wall. We will not strap a moving house to save a sale.
Carbon fiber is not a basement-only product. San Antonio rarely has true basements, but stem walls and garage walls still bow. Straps go on the inside face. If you planned to finish a garage wall, tell us so we leave a paint-ready grid. We will not hide movement behind texture. The survey decides whether straps are enough.
Neighborhood patterns help. Stone Oak stair-step brick after a wet May is usually clay heave then drop, not a bad mortar mix. Alamo Heights interior cracks on pier-and-beam can be lumber, not the brick veneer. We do not treat those the same. Bring the house age and foundation type if you know them. If you do not, the inspection names the type in the first half hour and the crack plan follows that, not a generic epoxy pitch.
Emergency same-day service is for cracks that opened after a storm, water coming through a wall, or a closing deadline. Hairlines that have looked the same for two summers can wait for a weekday inspection. We would rather schedule the right chemistry than inject the wrong resin at 7 p.m. because someone panicked at a pencil-thin line. Bring photos. They shorten the visit and improve the call.
Related guides
Call (830) 244-0222 for emergency same-day crack service across Bexar County. Written diagnosis before we inject.
San Antonio Slab Repair · 454 Soledad Street, 3rd Floor, San Antonio, TX 78205 · (830) 244-0222
Questions & answers
Foundation Crack Repair
Don't let a small crack become a $15,000 problem.
Foundation issues get worse every month. Our free inspection gives you a clear diagnosis and an honest quote, with no pressure.