Concrete repair FAQ: cracks, spalling, and cost

Last updated: October 28, 2026

This concrete repair FAQ covers what owners ask before they write off a slab. Which cracks matter? Can a spalled floor be saved, or does it have to come out? Start with what settles most calls. When a slab qualifies, repair fixes only the failed part. Our quote tool prices that at $8.27 to $22.41 a square foot of damaged area, and it skips the tear-out, hauling, and new pour a replacement needs. And most slabs people think are dead aren’t.

Cost and assessment

Cost comes up first on almost every call. The answer starts with the method, not the size.

How much does concrete repair cost?

When the slab qualifies, our quote tool prices concrete repair at $8.27 to $22.41 a square foot of damaged area. You pay for the part that failed, and you skip the tear-out, hauling, and new pour a replacement needs. The method sets the number, not the square footage. Crack routing and sealing is priced by the linear foot. Epoxy injection costs more, for the material and the pump gear. Full-depth section repair costs the most of all. It stacks tear-out, hauling, forms, and a fresh pour on top of the patch work that every smaller method skips. On a bigger slab, the cost per foot drops, because only part of it needs work and the fixed cost of getting the crew there spreads over more area. That’s why we price from an on-site look at the real damage, not a flat rate over the phone. Our concrete repair and resurfacing page lays out every method.

Why does concrete repair cost so much less than replacement?

Repair reuses the sound concrete you already own. Replacement doesn’t. It means tear-out, hauling, new forms, new steel, a fresh pour, and a 28-day wait before the slab reaches full strength and can carry real loads. When 60 percent or more of a slab is still solid, fixing the bad 40 percent skips most of that bill. And the savings grow on bigger slabs, where the failed part is a small share of the whole.

Do you charge for an on-site assessment?

The assessment is how we price the repair, and it comes with no obligation. A crew maps the crack pattern and measures any sinking with a straightedge and a level. They drag a chain across the slab to find hollow spots by sound, and they take photos of what they find. It’s the same look we’d want on our own driveway. You walk away knowing the method, a timeline, and a ballpark figure. A few photos sent ahead often narrow it down before anyone drives out to your site in Oklahoma City, Tulsa, or anywhere in the region.

So why is the visit worth your time before you’ve committed to anything? Because that’s where the options narrow. A crack that sounds solid under the chain and sits flush across the gap just needs a sealer. The same-looking crack over a hollow spot is a void, and we fill it before anything else happens. Spalling that stops at the top quarter inch gets a patch. Spalling down to rusting steel doesn’t. You can’t tell those apart from the driveway, and neither can we. That’s why somebody walks the slab first.

Guessing costs more than looking. The common mistake is buying a patch for a slab that was still moving. It cracks again in a season, and then you pay for the real fix on top of the first one. The other mistake runs the opposite way: writing off a slab as dead and replacing concrete that only needed a lift and a few routed cracks. Both cost real money, and both come from skipping the look.

Buying a building is the sharpest case. A floor you inherit is a floor you own, and finding out after closing that the shop slab needs work makes for a bad week. A look before closing tells you which repair belongs in the number you offer. That’s usually worth far more than the visit takes.

Cracks and what they mean

Reading the crack right is half the job. Most repair advice skips that step and jumps straight to a product, which is backwards.

Does every concrete crack need repair?

No. Hairline shrinkage cracks under about 1/8 inch are normal in any slab. They rarely need more than a sealer to keep water out. ACI 224.1R, the industry guide on cracking, treats fine shrinkage cracks as normal in cured concrete. It doesn’t count them as a defect. Concrete loses water as it cures, so it will crack somewhere, and control joints are there to pick where. The cracks worth worrying about grow over months, open wider than 1/4 inch, sit higher on one side, or weep water from the soil underneath. Width, movement, and offset tell you which kind you have.

What is the difference between a working crack and a hairline crack?

Width, movement, and offset are the three signs. A hairline shrinkage crack stays under 1/8 inch and sits flush across the gap. Once the slab finishes curing, it holds steady. A working crack moves with the seasons. It opens wider over the months, or one side drops below the other in a clear step. The first kind wants a flexible sealer, or nothing at all. The second wants a diagnosis first. Seal a moving crack with rigid epoxy, and it just cracks again a few inches over.

The real question under this one is usually the scary one. Does a crack mean my foundation is bad? Almost never. Nearly all the cracks in a floor slab are shrinkage. That’s concrete doing what concrete does as it dries out and gets a little smaller. Control joints exist because the industry treats that as normal. They pick where the slab will split, instead of pretending it won’t.

A foundation problem shows up differently, and it rarely shows up as one line in the floor. The signs worth taking seriously come in a group. One side of a crack sits higher than the other. Doors and windows that used to close now stick. Cracks run up a wall or step through the masonry joints, or the slab has dropped along one edge instead of cracking out in the middle. Any one of those alone can still be nothing. Three of them in the same room is a different conversation.

So we look. A crew reads the crack pattern, checks for offset, sounds for hollow spots, and puts a level across the floor. That one visit turns a worry into an answer. Most of the time the answer is boring, which is what you want. When it isn’t, you find out while the fix is still a repair.

What causes concrete to crack in the first place?

Expansive clay soil, clay that swells when it gets wet, is the main cause in regions with hot summers and cold winters. Clay swells 4 to 8 percent when it soaks up water, and it shrinks when it dries. That swing moves one part of the slab more than another, and the slab cracks. Red montmorillonite clays are the worst of them. Freeze-thaw adds damage at the surface. Water gets into the pores of the concrete, freezes, and grows about 9 percent, which breaks the paste around it. Road salt tracked onto driveways and garage floors speeds the whole cycle up. It lowers the freezing point, so each winter packs in more small freezes than the slab was ever poured to survive. Soil moves the slab. Salt and frost wear the surface.

Can a crack be repaired without replacing the whole slab?

Yes, in most cases. The method follows what the look finds:

• Crack routing and sealing handles surface cracks that have stopped moving, with a flexible polyurethane or silicone fill.
• Epoxy injection puts the strength back in cracks that hold still, even ones as narrow as 0.002 inches. Once cured, it tops 6,000 PSI in tensile strength, which is how hard it resists being pulled apart.
• Full-depth repair saws out only the failed section, removes it, and pours it back, tied into the old slab with steel dowel bars.

We go with partial repair whenever the concrete around the damage is sound. That saves both the cost and the mess of a full tear-out.

Spalling and surface damage

Spalling looks bad, and most owners take it as a sign of a tear-out. It almost never is.

What is spalling and what causes it?

Spalling is concrete that has flaked, chipped, or popped off the surface. It shows up most around joints and edges, where de-icing salt collects. Freeze-thaw and salt cause most of it. Poor finishing and too much water in the mix (a high water-cement ratio) come close behind. Both weaken the top layer of paste, so it sheds in the first hard winter. ASTM C672 is the test that grades how well a mix holds up to salt, and the slabs that scored poorly are the ones that spall first.

Can spalling concrete be repaired or does it have to be replaced?

Most spalling gets repaired, not replaced. A crew chips out the weak concrete back to a sound, rough surface that matches an ICRI 310.2 profile. Then a partial-depth patch with a polymer-modified or ASTM C928 rapid-set mortar rebuilds the top. Replacement only becomes the answer in two cases. Spalling has bared rusted rebar across a large area, or the slab has lost structural section, which means real thickness and strength are gone. A spalled garage floor is almost always a patch-and-resurface job, not a tear-out.

How deep does spalling have to be before it is serious?

Spalling in the top 1/4 inch is a surface problem. It patches or resurfaces cleanly. The trouble starts when the damage reaches the steel. Rebar swells as it rusts, and that pushes more concrete off from the inside out. That’s how a shallow flake nobody touched for a few years turns into a structural repair. At that depth, a crew chips back to sound concrete, treats or replaces the steel, and patches with a bonded repair mortar.

Repair versus replacement

Repair wins on cost and downtime most of the time. Not every time. An honest contractor tells you when a slab has really lost its strength.

When does concrete repair make more sense than full replacement?

Repair is the right call when most of the slab is sound and the damage sits in one spot or only on top. Picture a driveway with 2 to 5 cracks from clay movement over a level base. Or a garage floor with surface spalling and no sinking, or a patio with scaling on solid concrete. Repair stops making sense past about 40 percent slab damage, more than 1.5 inches of settling, or rusted steel in several places. Past that line, a fresh pour buys a longer life for each dollar you spend.

How do I know if my slab is beyond repair?

A slab is past repair when it has lost structural section. Look for four signs. Spalling bares rusted rebar across a wide area. The slab has broken into many separate pieces. It sank too far for a lift to fix. Or the base under it has a drainage failure that will keep shifting the concrete, no matter what goes on top. We run those numbers at every assessment, so you compare real options instead of guessing from the driveway. Our overlay versus replacement guide walks the decision in more depth.

Resurfacing and durability

A worn-out top over a sound slab is the classic case for resurfacing. And a good repair can outlast the concrete around it.

What resurfacing options fix widespread surface damage?

Sometimes spalling or scaling is too spread out to patch spot by spot. Then we use a polymer-modified cement overlay, usually 1/8 to 3/8 inch thick, to put back an even top. Indoor overlays last 10 to 15 years. Outdoor work uses freeze-thaw-rated systems built for the region’s winters. For a bigger upgrade in looks on sound concrete, a thin decorative topping or microtopping crosses over from repair into a finished floor. Either way, the bond coat and the prep decide how long that overlay holds.

What is the difference between resurfacing and a decorative overlay?

Resurfacing fixes how the floor works. It puts a sound, even top back on a slab that has scaled or spalled, and the only goal is a floor that works again. A decorative overlay adds color, pattern, or texture on top of concrete that’s already sound. The line blurs, because the same family of polymer-modified materials does both jobs. If the goal is fixing damage, that’s repair, and the concrete repair guide matches each method to its problem in detail.

Can you fix a sunken or settled slab without tearing it out?

Usually, yes. Slab lifting is the answer when the concrete is sound but the soil under it washed out or packed down. Polyurethane foam injection drills dime-sized holes, pumps foam under the slab, and raises it back to grade in minutes. The foam cures in about 15 minutes, so the slab takes traffic the same day. Mudjacking pumps a cement slurry to do the same job at a lower material cost. Our quote tool prices a lift at $4.72 to $9.38 a square foot. Both methods cost less than a tear-out, because the slab stays in place. There’s no hauling and no new pour.

How long does a concrete repair last?

A well-bonded repair lasts 10 to 20 years, and often the rest of the slab’s life. Epoxy-injected structural cracks in a stable slab hold for good, because the cured epoxy is stronger than the concrete it bonds to. Routed and sealed joints run 5 to 10 years before the sealant needs a refresh. How long it lasts comes down to prep, not the patch. A repair placed over a dusty or delaminated surface, where the top layer is already coming apart, can pop loose in one freeze-thaw season.

Why does surface preparation decide whether a repair lasts?

Bond is everything, and the bond gets built in the prep. ICRI 310.2 sets the surface profiles a repair material needs, from a light broom texture to a rough finish with the stone showing. The product data sheet says which one. ASTM C1583 is the pull-off test that proves it worked. A passing core breaks in the old concrete, not at the repair line. A material can hit full strength and still fail if it went down over a weak, dirty surface, because the weak spot just moves to the bond.

Getting started

The fastest path to a real answer is a few photos and a short description.

Will a repair fail again if the cause is not addressed?

Yes. Any repair fails again in time if the root cause keeps working. Soil movement, poor drainage, tree roots, and a washed-out base all keep shifting the slab, no matter how good the patch is. A patch is only as good as the ground it sits on. That’s why a crew finds the cause before recommending a fix, following the ACI 546 repair guide. Fixing drainage, filling voids, or firming up the soil sometimes adds scope. It’s also what turns a one-season patch into a 15-year repair.

How long does a repair project take?

Most home repairs finish in 1 to 3 days. Epoxy injection is often a single day, and it reaches full strength in 24 to 72 hours, depending on the temperature. Routed sealant is usually ready for traffic about a day later. Polymer overlays need 24 to 48 hours before foot traffic and 72 before vehicles. Full-depth sections follow normal concrete cure times, about 7 days to design strength and 28 to full strength. Cure time sets the calendar, not labor. Commercial work can run at night and on weekends, one zone at a time. That way a floor that has to stay open during business hours keeps working.

Do you repair both residential and commercial concrete?

Yes. Home work covers driveways, patios, garage floors, sidewalks, and pool decks. Commercial work covers warehouse floors, loading docks, parking structures, and storefronts across Oklahoma and the states around it. The methods are the same. The scale and the access change. Bel Covo has repaired concrete on Fortune 500 facilities and single-family homes since 2004, working from our shop in Prague, Oklahoma, where every crew runs the same steps to read a slab.

How do I get a quote for concrete repair?

Send a few photos of the damage and a short note through the online quote form. We tell you whether repair is the right call. If it is, we set up an on-site assessment and send back a quote with the method matched to the damage. No obligation. No pressure. For a contractor who needs both the repair and a new pour, one quote can cover the whole job.