Why Is My Driveway or Walkway Cracking?

Root cause

Concrete expands and contracts with temperature changes, and repeated freeze-thaw cycles in colder climates put ongoing stress on the surface. Thin hairline cracks are a normal, largely cosmetic result of this over years of exposure, not a sign of a structural problem.

30-second check

Measure the crack's width with a coin or ruler. True hairline cracks are far thinner than 1/4 inch. Cracks up to about 1/4 inch wide are usually cosmetic as long as both sides of the crack are level with each other with no step or height difference.

Tools & materials

Concrete crack filler or sealant (squeeze-tube or pourable), a wire brush, a caulking gun if using a cartridge-style filler.

Step-by-step

1. 1 Clean the crack thoroughly with a wire brush to remove loose debris and dirt.
2. 2 Apply concrete crack filler directly into the crack, following the product's instructions for depth and application.
3. 3 Smooth the surface level with a putty knife while the filler is still workable.
4. 4 Allow to cure fully per the product's timeline before driving or walking heavily on it.
5. 5 Reapply sealant to the full driveway or walkway every 2–3 years as routine maintenance to prevent new cracks from forming as easily.

Root cause

The flexible material in expansion joints (the intentional gaps between concrete sections) breaks down over time from sun and weather exposure, losing its ability to absorb the slab's natural movement, which can then show up as cracking near those joints instead of the joint flexing as intended.

30-second check

Look specifically at the expansion joints between concrete sections for crumbling, missing, or hardened filler material rather than a flexible seal.

Tools & materials

A flathead screwdriver or joint-cleaning tool, self-leveling polyurethane joint sealant, a caulking gun.

Step-by-step

1. 1 Remove old, deteriorated joint filler with a screwdriver or joint-cleaning tool.
2. 2 Clean out the joint thoroughly, removing debris and dust.
3. 3 Apply new self-leveling polyurethane sealant into the joint, following the product's fill-depth instructions.
4. 4 Allow to cure fully before use.
5. 5 Repeat for all joints showing similar deterioration. They typically age at a similar rate.

Root cause

Spalling, meaning flaking or pitting at the surface, often results from de-icing salt exposure, poor original finishing, or trapped moisture freezing near the surface. Crumbling edges along a driveway are frequently from repeated vehicle weight concentrated right at the unsupported edge.

30-second check

Look for a rough, pitted, or flaking surface texture (spalling) rather than a clean crack, or check whether damage is concentrated specifically along an unsupported edge.

Tools & materials

A concrete patching compound or resurfacer, a trowel, a wire brush, safety glasses.

Step-by-step

1. 1 Clean the damaged area thoroughly, removing all loose and crumbling material with a wire brush.
2. 2 Dampen the area slightly per the patching product's instructions for better adhesion.
3. 3 Apply concrete patching compound or resurfacer with a trowel, feathering the edges to blend with the surrounding surface.
4. 4 Allow to cure fully before foot or vehicle traffic, following the product's specific timeline.
5. 5 Consider reducing future salt use on this area, or switching to a concrete-safe de-icer, if salt exposure was the likely cause.

Root cause

Cracks wider than about 1/4 inch, or where one side of the crack sits noticeably higher or lower than the other, indicate the ground underneath has shifted, from erosion, poor original compaction, or a plumbing leak washing out the base material. Surface sealant won't address movement happening below the slab.

30-second check

The crack is wider than roughly 1/4 inch, one side is visibly higher than the other, or an entire slab section has noticeably sunk relative to its neighbors.

What a professional actually does

A professional evaluates the underlying cause of movement, and depending on the diagnosis either lifts and levels the existing slab (mudjacking or polyurethane foam injection), replaces the affected section, or addresses a drainage or plumbing issue that's washing out the base material.