Concrete repair FAQ: cracks, spalling, and cost

Last updated: August 21, 2026

This concrete repair FAQ answers what owners ask before they write off a slab. Which cracks actually matter? Can a spalled floor be saved, or does it have to come out? Every answer below carries a straight number, starting with the one that decides most of these calls: concrete repair typically runs 30 to 60 percent of full replacement cost when the slab qualifies. Most slabs people assume are dead aren’t.

Cost and assessment

Cost leads almost every call, and the honest answer starts with the method, not the square footage.

How much does concrete repair cost?

Concrete repair typically runs 30 to 60 percent of full replacement cost when the slab qualifies. The method drives the number, not the square footage. Crack routing and sealing is priced by the linear foot, epoxy injection costs more for materials and pump equipment, and full-depth section repair runs highest of all, because it carries demolition, hauling, forming, and a fresh pour stacked on top of the patch work every smaller method skips. Larger slabs actually bring the per-unit cost down, since only a portion needs work and the fixed mobilization spreads across more area. That’s why we price from an on-site read of the actual damage instead of a flat rate off a phone call, and our concrete repair and resurfacing page lays out the full method menu.

Why does concrete repair cost so much less than replacement?

Repair reuses the sound concrete you already own. Replacement doesn’t: it means demolition, hauling, new forms, new reinforcement, a fresh pour, and a 28-day wait for full strength before the slab carries real load. When 60 percent or more of a slab is still solid, fixing the bad 40 percent skips most of that bill, and the savings only grow on larger slabs where the failed area is a small fraction of the whole.

Do you charge for an on-site assessment?

The assessment is how we price the repair, and it carries no obligation. A crew maps the crack patterns, measures any settlement with a straight-edge and level, sounds the slab for hollow spots with a chain drag, and documents conditions in photos. Same read we’d want on our own driveway. You walk away knowing the recommended method, a timeline, and a ballpark figure. A few photos up front often narrow the read before anyone drives out to your site in Oklahoma City, Tulsa, or anywhere in the region.

The fair follow-up question is why the visit is worth anybody’s time before you’ve committed to anything. Because the visit is where the options get narrowed. A crack that sounds solid under a chain drag and sits flush across the gap is a sealer. The same-looking crack over a hollow spot is a void that gets filled before anything else happens. Spalling that stops at the top quarter inch patches; spalling down to rusting steel doesn’t. You cannot tell those apart from the driveway, and neither can we, which is exactly why somebody walks the slab first.

Guessing costs more than looking. The common version is a homeowner who buys a patch for a slab that was moving, watches it crack again in a season, and then pays for the real fix on top of the first one. The other version is the opposite mistake: writing off a slab as dead and replacing concrete that only needed a lift and a few routed cracks. Both are expensive, and both come from skipping the read.

Buying a building is the sharpest case of this. A floor you inherit is a floor you own, and finding out afterward that the shop slab needs work is a bad week. A read before closing tells you which repair line belongs in the number you offer, and that is usually worth far more than the visit takes.

Cracks and what they mean

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

Does every concrete crack need repair?

No. Hairline shrinkage cracks under about 1/8 inch are normal in any slab and rarely need more than a sealer to keep water out, because ACI 224.1R, the industry document on cracking, describes fine shrinkage cracks as expected behavior in cured concrete rather than a defect that signals failure. A slab that loses water as it cures will crack somewhere, and control joints exist to choose where. The cracks worth worrying about grow over months, run wider than 1/4 inch, show vertical offset, or weep water from the soil beneath. Width, movement, and offset tell you which one you have.

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

Width, movement, and offset are the three signals. A hairline shrinkage crack stays under 1/8 inch, sits flush across the gap, and holds steady once the slab finishes curing, while a working crack moves with the seasons, opens wider over months, or shows one side dropped below the other in a clear vertical step. The first wants a flexible sealer or nothing at all. The second wants diagnosis first, because sealing a moving crack with rigid epoxy just relocates it a few inches over.

The question underneath this one is usually the scarier version: does a crack mean my foundation is bad? Almost never. The overwhelming majority of cracks in a floor slab are shrinkage, which is concrete doing the one thing concrete does as it dries out and gets smaller. Control joints exist because the industry accepts that behavior as normal and chooses where the slab will split rather than pretending it won’t.

A foundation problem announces itself differently, and it rarely announces itself with a single line in the floor. The signs worth taking seriously stack up together: vertical offset where one side of a crack sits higher than the other, doors and windows that used to close and now stick, cracks running up a wall or stepping through masonry joints, and a slab that has dropped along one edge instead of cracking in the field. One of those on its own 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 voids, and puts a level across the floor, and that single visit turns a worry into a verdict. Most of the time the verdict is boring, which is the outcome 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 is the primary driver in continental climate regions. Clay swells 4 to 8 percent when it absorbs moisture and shrinks when it dries, and that seasonal volume change creates the differential movement under a slab that produces cracks. Red montmorillonite clays are the worst offenders. Freeze-thaw cycling adds surface damage as water enters concrete pores, freezes, expands about 9 percent, and fractures the surrounding paste, while road salt tracked onto driveways and garage floors accelerates the whole cycle by lowering the freezing point and stacking more micro-freeze events into each winter than the slab was ever poured to survive. Soil moves the slab. Salt and frost work the surface.

Can a crack be repaired without replacing the whole slab?

Yes, in most cases. The method follows the diagnosis:

• Crack routing and sealing handles dormant surface cracks with a flexible polyurethane or silicone fill.
• Epoxy injection restores structural capacity on static cracks as narrow as 0.002 inches, with cured strength over 6,000 PSI tensile.
• Full-depth repair sawcuts, removes, and re-pours only the failed section, tied into the existing slab with dowel bars.

We reach for partial repair whenever the surrounding concrete is sound, which saves both the cost and the disruption of a full tear-out.

Spalling and surface damage

Spalling looks alarming, and most owners read it as a tear-out. It almost never is.

What is spalling and what causes it?

Spalling is concrete that has flaked, chipped, or popped away from the surface, usually around joints and edges where de-icing salt collects. Freeze-thaw cycling and salt cause most of it. Poor finishing and a high water-cement ratio sit close behind, weakening the surface paste so it sheds under the first hard winter. ASTM C672 is the scaling-resistance test that grades how a mix holds up to salt, and the slabs that scored poorly are the ones spalling first.

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

Most spalling repairs without replacement. Partial-depth patching with a polymer-modified or ASTM C928 rapid-set mortar restores the surface once a crew removes the unsound concrete back to a sound, roughened substrate matching an ICRI 310.2 profile. Replacement only becomes the answer when spalling exposes corroded rebar across a large area or the slab has lost structural section. 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 limited to the top 1/4 inch is a surface problem that patches or resurfaces cleanly. The trouble starts when damage reaches the reinforcing steel, because corroded rebar expands as it rusts and drives more spalling from the inside out, which is 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 in most cases. Not all of them. An honest contractor tells you when a slab has actually lost its integrity.

When does concrete repair make more sense than full replacement?

Repair is the right call when most of the slab is structurally sound and the damage is localized or surface-level. Picture a driveway with 2 to 5 clay-movement cracks over a level base, a garage floor with surface spalling and no settlement, or a patio with scaling on solid concrete. Repair stops making sense past roughly 40 percent slab damage, settlement over 1.5 inches, or corroded reinforcement in several places. Past that line, a fresh pour buys a longer service life per dollar spent.

How do I know if my slab is beyond repair?

A slab is beyond repair when it has lost structural section. The signs: spalling that exposes corroded rebar across a wide area, a slab cracked into many independent pieces, settlement too severe for lifting to correct, or a subgrade with systemic drainage failure that will keep shifting the concrete no matter what goes on top. We run those numbers on every assessment so you compare real options instead of guessing from the driveway, because most slabs people assume are dead, honestly, aren’t. Our overlay versus replacement guide walks the decision in more depth.

Resurfacing and durability

A failing wearing surface over a sound slab is the classic resurfacing candidate, and a good repair outlasts the concrete around it.

What resurfacing options fix widespread surface damage?

A polymer-modified cementitious overlay, usually 1/8 to 3/8 inch thick, restores a uniform wearing surface when spalling or scaling is too widespread for spot patching. Interior overlays last 10 to 15 years, and exterior work uses freeze-thaw-rated systems built for the region’s winters. For a deeper cosmetic upgrade on sound concrete, a thin decorative topping or microtopping crosses from repair into a finished floor. Either way, the bond coat and the surface prep decide how long that overlay holds.

What is the difference between resurfacing and a decorative overlay?

Resurfacing restores function. It puts a sound, uniform wearing surface back on a slab that has scaled or spalled, with no goal beyond 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 polymer-modified family of materials does both jobs. If the goal is fixing damage, that’s repair, and the concrete repair guide covers the method-to-problem match 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 compacted. Polyurethane foam injection drills dime-sized holes, pumps expanding foam beneath the slab, and raises it back to grade in minutes, with the foam curing in about 15 minutes so the slab takes traffic the same day. Mudjacking pumps a cement slurry to the same end at lower material cost. Both beat tear-out on price, often by 30 to 50 percent.

How long does a concrete repair last?

A properly bonded repair lasts 10 to 20 years and often the remaining life of the slab. Epoxy-injected structural cracks in a stabilized slab hold indefinitely, because the cured epoxy is stronger than the concrete it bonds. Routed and sealed joints run 5 to 10 years before the sealant is refreshed. Durability comes down to prep, not the patch: a repair placed over a dusty or delaminated surface can pop loose in a single freeze-thaw season.

Why does surface preparation decide whether a repair lasts?

Bond is everything, and bond is built in the prep. ICRI 310.2 defines the surface profiles a repair material needs, from a light broom texture to an aggressive exposed-aggregate finish, and the product data sheet specifies which one. ASTM C1583 is the pull-off test that proves it worked, where a passing core breaks in the parent concrete rather than at the repair line. A material can hit full strength and still fail if it went down over a weak, contaminated surface, because the failure plane 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 eventually fails again if the root cause keeps working. Soil movement, poor drainage, intruding tree roots, and a washed-out subgrade 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 identifies the cause before recommending a fix, following ACI 546 repair-guide doctrine. Correcting drainage, filling voids, or stabilizing soil sometimes adds scope, and it’s exactly what turns a one-season patch into a 15-year repair.

How long does a repair project take?

Most residential repairs finish in 1 to 3 days. Epoxy injection is often a single day and reaches full strength in 24 to 72 hours depending on temperature, routed sealant is typically traffic-ready about a day later, and polymer overlays need 24 to 48 hours before foot traffic and 72 before vehicle loads. Full-depth sections follow standard concrete cure schedules, roughly 7 days to design strength and 28 to full strength. Cure time, not labor, sets the calendar. Commercial work phases into evening and weekend windows, so floors that have to stay open during business hours keep operating while a crew works one zone at a time.

Do you repair both residential and commercial concrete?

Yes. Residential work covers driveways, patios, garage floors, sidewalks, and pool decks, while commercial work covers warehouse floors, loading docks, parking structures, and retail storefronts across Oklahoma and the surrounding states. The methods are the same; the scale and access logistics 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 diagnostic framework.

How do I get a quote for concrete repair?

Send a few photos of the damage and a short description through the online quote form. We tell you whether repair is the right call, and if it is, we schedule an on-site assessment and return 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, a single quote can cover the whole scope.