Concrete Driveway Crack Repair: Fill, Seal, or Replace

Concrete driveway crack repair starts with understanding what kind of crack you have. Hairline shrinkage cracks are common and mostly cosmetic. Wider cracks let water reach the base, which can lead to settling, frost damage, and more cracking. Most cracks under about 1/2 inch can be cleaned and filled with a flexible sealant or a patching compound. Cracks with significant vertical offset or sunken slabs point to base problems that filling alone will not fix.

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Types of cracks

Crack	What it looks like	Typical cause	Repair
Hairline	Very thin, often random	Drying shrinkage	Leave, or seal with a penetrating sealer
Narrow (up to about 1/4 inch)	Visible, stable	Shrinkage, temperature	Flexible crack sealant
Wide (about 1/4 to 1/2 inch)	Open, may move	Settling, missing joints	Backer rod plus sealant, or patch
Offset or heaved	One side higher	Settlement, frost, roots	Leveling, grinding, or replacement
Map or spider cracking	Network of cracks	Surface issues, freeze-thaw	Resurface or replace

Choosing a filler

Polyurethane or hybrid sealant: flexible, bonds well, good for moving cracks and joints.
Silicone concrete sealant: flexible and self-leveling options for horizontal joints.
Epoxy or polyurea fillers: rigid; best for stable cracks and structural repairs, not moving joints.
Concrete patching compound: for chips and wider, stable cracks.

Avoid rigid fillers in cracks that open and close with temperature; they tend to crack again.

Step-by-step repair

Clean the crack with a wire brush, a screwdriver, and a shop vacuum or compressed air.
Widen tight cracks slightly with a grinder or chisel if the filler needs room.
Insert foam backer rod in cracks deeper than about 1/2 inch so the sealant is the right depth.
Apply the filler with a caulk gun, slightly overfilling.
Tool the surface smooth, and sprinkle sand on wet sealant for texture if desired.
Let it cure before driving, following the label.

Work on a dry day within the product’s temperature range.

When cracks mean bigger problems

Sunken or tilted slabs: consider slab lifting. See mudjacking vs polyjacking.
Cracks near the house where water flows toward the foundation.
Widespread scaling or crumbling: see concrete spalling from salt.
Cracks growing quickly or tree roots lifting sections.

Preventing new cracks

Keep control joints sealed.
Direct downspouts away from the driveway.
Avoid heavy trucks on residential slabs.
Seal with a penetrating sealer. See concrete driveway sealer types.

Bottom line

For concrete driveway crack repair, clean the crack, use backer rod for deep cracks, and fill with a flexible polyurethane or silicone sealant for moving cracks, or a rigid patch for stable damage. Offset or sunken sections need leveling or replacement. Keep water away and joints sealed to prevent new cracks.

Questions people ask

What is the best filler for concrete driveway cracks?

Flexible polyurethane or silicone sealants work well for most moving cracks.

Should I fill hairline cracks in concrete?

Hairline cracks are usually cosmetic. A penetrating sealer helps keep water out.

What is backer rod?

Foam rope pushed into deep cracks so sealant sits at the proper depth.

Can I drive on crack filler right away?

No. Wait for the product’s cure time.

When should a cracked driveway be replaced?

When cracks are widespread, slabs are badly heaved, or the base has failed.

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