Repair Methods
Concrete Foundation Repair
The short answer
Concrete foundation repair covers fixing a concrete slab or footing that has cracked, settled, or heaved — using crack injection for cracks, mudjacking or polyurethane foam to raise sunken concrete, and piers to stabilize structural settlement. In Austin, the right method depends on whether the concrete moved and why.
| Repair | Typical Austin range |
|---|---|
| Slab leveling (mudjacking / foam) | $600–$2,500 |
“Concrete foundation repair” is several different jobs
People search for concrete foundation repair to mean very different things — from a hairline crack to a sunken garage slab to a whole settling foundation. The methods (and prices) diverge sharply, so the first job is always diagnosis.
The three core methods
- Crack repair (injection). Epoxy or polyurethane fills and seals cracks. Best for non-structural cracks. Details in our crack repair guide.
- Slab leveling (mudjacking / polyurethane foam). For sunken concrete — interior slabs, patios, driveways, walkways. A slurry or expanding foam is injected beneath to raise it. Typically $600–$2,500 for residential flatwork.
- Underpinning (piers). When the foundation itself has settled structurally, slab leveling won’t cut it — you need piers to stabilize and lift.
How wide is too wide? The engineering guide to crack width
A crack in concrete becomes a repair question once it crosses about 1/8 inch — narrower cracks are usually dormant shrinkage, wider ones warrant a closer look. That threshold isn’t arbitrary: it comes from the American Concrete Institute’s ACI 224R guidance on “reasonable” crack widths for reinforced concrete under normal service loads, broken out by exposure condition — 0.016 in for concrete in dry air, 0.012 in (about 1/8 in) for concrete exposed to humidity, moist air, or soil, down to 0.007 in for deicing-chemical exposure and 0.004 in for water-retaining structures. Foundation concrete sits in soil, so the moist-soil figure is the relevant one — which is why the 1/8-inch line shows up elsewhere on this site as the point where cracks get a professional look rather than a watch-and-wait.
Two caveats matter more than the number. First, ACI 224R is an engineering reasonableness guide, not a code requirement or a diagnosis — a crack under 1/8 inch that’s actively growing is more urgent than a static crack that’s wider but unchanged for years. Second, width alone never reveals the cause; a hairline vertical shrinkage crack and a hairline crack from early-stage settlement can look identical at first, which is the whole reason diagnosis comes before any repair method.
You don’t need a crack gauge to get a rough read. A dime’s edge is about 0.05 inch thick and a credit card’s edge is about 0.03 inch — if a crack easily takes a dime, it’s already well past the 1/8-inch guidance point and worth having assessed.
Choosing right (and avoiding overpay)
The common mistake is using slab leveling on what is actually structural settlement, or piering what only needed foam. A trustworthy contractor — backed by an elevation survey and ideally an engineer — tells you which problem you have. See the full cost guide to set expectations before anyone quotes you.
Frequently asked questions
What is the best concrete foundation repair method?
It depends on the problem. Non-structural cracks call for injection; sunken interior slabs or flatwork call for mudjacking or polyurethane foam; structural settlement of the foundation calls for piers. The skill is matching the method to the cause, not applying one product to everything.
Is polyurethane foam better than mudjacking?
Foam is lighter, cures fast, resists washout, and is injected through smaller holes — great for slabs and flatwork. Mudjacking is cheaper and fine for many jobs. Foam usually costs more but is less disruptive and longer-lasting in expansive-soil conditions.
Can you repair a cracked concrete slab permanently?
You can permanently seal a crack and permanently stabilize settlement with piers. But if the underlying soil keeps moving, new cracks can form elsewhere — which is why drainage and moisture control are part of a durable concrete repair.
How wide does a concrete crack have to be before it's a problem?
There's no single universal cutoff, but the American Concrete Institute's guidance for reinforced concrete in contact with soil and moisture treats about 0.012 inch — roughly 1/8 inch — as the upper bound of a 'reasonable' crack width under normal service loads. Wider, or actively growing, cracks are what typically call for an assessment rather than monitoring.
How do I measure a crack without a crack gauge?
A dime's edge is about 0.05 inch thick and a credit card's edge is about 0.03 inch. If a crack easily swallows a dime, it's already well past the 1/8-inch guidance point. For anything close to that line, or one that's growing, a proper crack comparator card (or a ruler and a phone photo, repeated monthly) gives you a real measurement to track.