How do you repair cracks in a concrete driveway?

Seal it

under ⅛ inhairline, non-moving

Fill it

⅛–½ inrouted and sealed

Replace it

over ¼ in offsetvertical displacement

Wait before sealing

28 daysnew concrete, typical practice

Short version

• Diagnose first: shrinkage cracks are cosmetic, displacement cracks mean the subgrade moved.
• Clean and rout the crack before filling, or the repair pops out in a season.
• Flexible sealants for anything that opens and closes with temperature; rigid fillers only for static cracks.
• One slab lifted or dropped more than about ¼ inch is a lifting or replacement job, not a caulking job.
• Seal the driveway after repairs cure, not before.

What kind of crack is in your driveway?

Driveway cracks fall into four families, and each one calls for different work. Shrinkage cracks are narrow, wander irregularly, and appear in the first weeks or months as the slab dries. NRMCA’s guidance on cracking concrete surfaces and on plastic shrinkage cracking covers why they form. They are almost always cosmetic and are the ideal candidate for cleaning and sealing.

Control-joint cracks are shrinkage cracks that went where they were supposed to. A crack running dead straight through a tooled or saw-cut joint is the slab working exactly as designed. Seal the joint, do not treat it as damage.

Settlement cracks come with vertical offset — one side sits higher than the other — and usually run near the edge of a slab, over a utility trench, or where a tree root pushed. The concrete did not fail; the ground under it did.

Structural or alligator cracking is a network of interconnected cracks across a panel, often with spalled or loose edges. That pattern means the slab is undersized for the load, the base is failing, or both.

Surface scaling and popouts are a separate problem from cracking. NRMCA’s guidance on scaling covers the freeze-thaw and deicer damage that flakes off the top layer.

When do you repair a driveway crack and when do you replace the slab?

Repair when the concrete is sound and the ground under it is stable. That means cracks under roughly ¼ inch wide, no vertical displacement between the sides, edges that are solid rather than crumbling, and no more than a few cracks per panel. A driveway like that will take a sealed repair and go another decade.

Replace, or lift and then repair, when any of these show up. Vertical offset over about ¼ inch is a trip hazard and a sign the subgrade moved. Alligator cracking across a full panel means the slab has lost its structural continuity. Widespread spalling, exposed and rusting reinforcement, or a slab that rocks under a car all point the same direction.

The middle case is a slab that is intact but has settled as a unit. Polyurethane foam lifting or mudjacking raises it back to grade at a fraction of replacement cost, and only then do you seal the cracks. Lifting a slab first and sealing second is the correct order; sealing a slab you are about to lift wastes the sealant.

Cost usually decides the borderline cases. Repairing two or three cracks is inexpensive. Repairing fifteen is most of the price of a new panel with none of the life.

What do you fill a driveway crack with?

Match the material to how much the crack moves. Exterior driveway cracks open in winter and close in summer, so almost all of them need a flexible material — a self-leveling polyurethane or silicone sealant meeting ASTM C920, or a hot-pour or cold-pour joint sealant for pavement. Rigid cementitious patch in a moving crack cracks again along the same line.

Wide cracks and crumbled edges need a repair mortar or a polymer-modified patching compound rather than sealant alone, because sealant has nothing to grip. Very fine hairlines under about ⅛ inch often cannot accept any filler at all and are usually best left alone or covered by a resurfacer.

The full comparison of sealants, epoxy injection, and patching materials, plus how to tell a moving crack from a static one, is on the how to fill cracks in concrete page. Structural crack repair on a driveway is rare; epoxy injection belongs on walls and structural members, not on flatwork that needs to move.

Color matters more than people expect. Gray sealant on a weathered driveway reads as a gray stripe for years.

How do you repair the crack step by step?

Work on a dry day with the forecast clear for 24 hours, and start by opening the crack up. Chase it with a crack chaser wheel on an angle grinder or a masonry blade to create a clean channel roughly ¼ inch wide and ¼ inch deep. A routed channel gives the sealant a shape it can stretch in; an unrouted hairline gives it nothing.

Clean everything out. Vacuum, then blow with compressed air, then vacuum again. Dust and loose material are the single most common reason a crack repair fails. Kill any vegetation growing in the crack and let the channel dry completely.

For channels deeper than about ½ inch, press in closed-cell backer rod so the sealant bonds to the two sides and not to the bottom. A sealant bonded on three sides cannot stretch and tears.

Apply the sealant, tool it slightly below the surface, and let it cure for the time the manufacturer’s data sheet gives before driving on it. Dry-cutting concrete releases respirable silica regulated by OSHA under 29 CFR 1926.1153, so use a wet-cut or dust-collecting setup.

Should you seal the driveway after repairing the cracks?

Seal after the repairs cure, never before. A penetrating silane or siloxane sealer reduces water and chloride absorption, which is what drives freeze-thaw damage and deicer scaling — the failure mode NRMCA’s scaling guidance describes. Sealing a driveway you are about to repair just means grinding sealer back off.

Wait the full cure time on the crack sealant, which is typically several days rather than several hours, and check the sealer’s data sheet for compatibility with the sealant you used. Some film-forming acrylics will not bond over silicone.

New concrete gets sealed at around 28 days as a common contractor practice, not before. Sealing a slab that is still releasing construction moisture traps that water and causes blistering and whitening.

Sealing does not stop cracks. Water and salt drive most driveway deterioration, so a sealer buys years of durability, but shrinkage and settlement have nothing to do with surface absorption. More about driveway sealer selection and timing is covered on the driveway sealing page.

Common mistakes

• Filling a crack without cleaning and routing it — sealant bonded to dust lets go in one freeze-thaw season.
• Using rigid patch material in a moving crack — the crack reopens along the repair line, usually by the next spring.
• Sealing over a settlement problem — if the ground moved, the crack comes back wider, and the filler only hides it until then.
• Bonding the sealant to the bottom of the channel — without backer rod, the sealant cannot stretch and tears down the middle.
• Sealing the driveway before the repairs cure — the sealer traps solvent and moisture and both the repair and the seal fail.