Concrete Crack Repair:
Methods, Materials
& Cost

Concrete crack repair starts with one question most people skip: is the crack still moving? A dormant hairline in a garage floor and an active crack across a driveway look similar, but they need opposite materials. Fill a moving crack with something rigid and it reopens next to the repair. Fill a forklift aisle crack with soft caulk and the edges break down. This guide shows how we read a crack, which method fits which crack, and what it costs.

Concrete crack repair method selector

Pick what you see. The selector applies the same logic our applicators use on a walk-through: movement and traffic decide the material, width decides the prep, and offset or settlement overrides everything.

How to repair a concrete crack, step by step

This is the sequence for a typical exterior slab crack using a flexible sealant, with notes where a floor crack under traffic differs.

1. Open and clean the crack

   Grind or rout narrow cracks into a clean V or square groove so the filler has two sound sidewalls to grip. TxDOT's rout-and-seal method uses a V groove typically about 3/8 in deep. Vacuum and blow out every bit of dust; filler stuck to dust is not stuck to concrete.

2. Let it dry

   Most sealants and resin fillers want a dry crack. After pressure washing, give it time, or use a torch or heat gun carefully on cool days.

3. Set the depth with backer rod

   For moving cracks, push closed-cell backer rod or bond breaker tape in so the sealant bonds to the two sides only, not the bottom. W. R. Meadows specifies a 2:1 width-to-depth ratio for Pourthane SL, from 1/4 in to 1/2 in wide. A thin, wide bead stretches; a deep, narrow one tears.

4. Fill wide voids first

   On floors, fill deep cracks with dry silica sand to just below the surface before pouring a low-viscosity resin, so the resin is not lost into the subgrade.

5. Fill slightly proud or flush

   Self-leveling sealant goes in flush or just below the surface. Semi-rigid polyurea or epoxy fillers are overfilled and shaved flush after cure so wheels roll over a continuous surface.

6. Protect while it cures

   Pourthane SL lists a skin time of 60 to 120 minutes and full cure around 72 hours at normal conditions. Keep tires and foot traffic off until the data sheet says otherwise.

Concrete crack repair under coatings and overlays

Most of our crack repair happens one day before a coating goes down. Garage floors, shop floors, pool decks and patios all get their cracks treated during prep, and how they are treated decides whether lines show up in the finished floor six months later.

For a full garage or shop system, our garage floor coating guide walks through prep, crack repair and topcoats. For warehouse floors, joint maintenance is half the job; see industrial flooring. If the cracks are part of a worn, scaled surface, a bonded overlay may fix both at once; see concrete resurfacing. Exterior slabs that are only cracked, not scaled, usually just need the cracks filled and a good concrete sealer.

Why ACI tolerable widths matter for driveways

The tolerable width of 0.007 in for deicing exposure is tiny, about the thickness of two sheets of paper. The point is not that every crack wider than that is a failure. It is that cracks wider than that let chloride-laden water reach reinforcing steel. Rusting steel expands and pops the concrete off above it. Sealing exterior cracks every few years is cheap insurance against that kind of damage.