How to Repair Cracked Concrete (Driveways, Patios and Walkways)

A crack in your driveway, patio or walkway looks bad, but it’s usually not an emergency. Small cracks are an easy weekend fix. The real goal is to seal them before water gets in, freezes, and turns a hairline crack into a broken slab.

This guide shows how to repair cracked concrete step by step, depending on how wide the crack is. You’ll learn which filler to use, how to prep the crack so the repair lasts, the best weather for the job, and when a crack is a sign you need a professional instead.

Why You Should Fix Cracks Early

Water is concrete’s biggest enemy. When it seeps into a crack, it can wash out the base underneath and, in cold climates, freeze and expand. Each freeze-thaw cycle pushes the crack a little wider. Weeds also root in cracks and pry them open. A small repair now saves a much bigger one later.

Step 1: Measure the Crack

Match the repair to the size. Use a ruler or a coin as a rough guide.

Tools and Materials

• Wire brush and a stiff broom
• Shop vacuum or leaf blower
• Cold chisel and hammer (for wide or crumbling cracks)
• Concrete crack filler or patching compound (see the table)
• Foam backer rod (for cracks deeper than about 1/4 inch)
• Caulk gun, trowel or putty knife
• Safety glasses, work gloves and a dust mask or respirator

Safety First: Concrete Dust

Chiseling or grinding concrete creates fine dust that contains crystalline silica. OSHA lists cutting, grinding and drilling concrete as sources of this dust, and breathing it can cause silicosis, an incurable lung disease, as well as lung cancer (OSHA). For small home repairs:

• Wear safety glasses and a well-fitting N95 or better respirator when chiseling or brushing out dust.
• Mist the crack lightly with water before chiseling to keep dust down.
• Avoid power grinding unless the tool has a dust collection attachment.
• Keep kids and pets away while you work.

Step 2: Clean Out the Crack

A repair only lasts if the filler bonds to clean, solid concrete.

1. Pull out weeds and dig out dirt with a screwdriver or chisel.
2. Scrub the crack with a wire brush to remove loose bits.
3. For wide or crumbling cracks, chip away loose concrete with a cold chisel until the edges are solid.
4. Vacuum or blow out all the dust and debris.
5. Let the crack dry fully unless your product says to apply it to damp concrete.

Step 3: Add Backer Rod for Deep Cracks

If a crack is deeper than about 1/4 inch, press foam backer rod into it with a putty knife so the top sits about 1/4 inch below the surface. Backer rod saves filler and helps the sealant flex properly, which makes the repair last longer.

Step 4: Fill the Crack

For cracks up to 1/2 inch wide

Use a flexible concrete crack filler in a caulk tube. Cut the nozzle to match the crack width, then fill the crack slowly and evenly, slightly overfilling it. Many fillers are self-leveling on flat surfaces. Smooth the top with a putty knife if needed.

For wider cracks and crumbling edges

Mix a concrete patching compound or repair mortar following the label. Press it firmly into the crack with a trowel to remove air pockets, then smooth it flush with the surface. Match the texture of the surrounding concrete with a brush or broom before it sets.

Step 5: Let It Cure

Follow the product label for cure time. Most fillers need several hours before foot traffic, and longer before you drive on them. Keep the area dry while it cures and block it off with tape or cones if needed.

Best Weather for Concrete Repairs

Many concrete repair products need dry weather and mild temperatures to cure properly. Check the label for the minimum temperature, and avoid working right before rain or a hard freeze. In most of the U.S., spring through early fall is the best time to fix outdoor concrete.

Prevent New Cracks

• Seal the surface. A concrete sealer every few years helps keep water out. Follow the product directions.
• Keep water away. Point downspouts away from driveways and patios, and fix low spots where water pools.
• Go easy on deicers. Some deicing salts can damage concrete, especially newer concrete. Check the label before using them, and use sand for traction where you can.
• Avoid heavy loads. Keep heavy trucks and equipment off driveways not built for them.
• Pull weeds early. Remove weeds from cracks and joints before roots widen them.

When to Call a Pro

DIY fillers work well for surface cracks. Call a concrete contractor or structural engineer if:

• One side of the crack is higher than the other, or a slab has sunk or lifted.
• The crack is wide and keeps growing after you repair it.
• Large areas of the surface are crumbling or flaking.
• The crack is in a foundation wall, especially if it’s horizontal, shaped like stairs in a block wall, leaking water, or getting wider. Foundation cracks can point to structural problems that need an expert.

Concrete Repair Myths vs Facts

Myth: All concrete cracks mean something is seriously wrong.
Fact: Concrete naturally shrinks as it cures, and small hairline cracks are common. Width, movement and uneven edges are what matter.

Myth: You can fill a crack with regular cement.
Fact: Plain cement or mortar often doesn’t bond well to old concrete and can crack again. Use a product made for concrete crack repair.

Myth: A thicker layer of filler lasts longer.
Fact: Proper prep matters more than thickness. A clean, dry crack and backer rod for deep cracks make the biggest difference.

Myth: Repaired cracks will be invisible.
Fact: Repairs usually show some color difference. If looks matter, a concrete resurfacer over the whole slab gives a more even finish.

The Bottom Line

To repair cracked concrete, match the fix to the crack: sealant or flexible filler for narrow cracks, patching compound for wide ones. Clean the crack well, use backer rod for deep cracks, work in mild, dry weather, and protect your lungs from concrete dust. Call a pro for uneven slabs, growing cracks or any worrying foundation crack.

For indoor wall repairs, see our guide on how to patch small holes in drywall.