Driveway Crack Repair: How to Fix Cracks in a Concrete Driveway

What do you need for driveway crack repair?

A UV-stable crack kit, dry silica sand and a few hand tools. A driveway sits in full sun, carries car weight and moves with the seasons, so it needs a filler that flexes and holds up to sunlight.

The sand isn’t in the kit, so buy a bag of dry silica sand separately. The kit’s urethane isn’t UV-stable on its own. The polyurea top layer is what protects it from the sun, so don’t skip that layer outdoors.

How do you fix cracks in a concrete driveway?

Pull any weeds, open up thin cracks, clean and dry them, pack them with sand soaked in urethane, then top them with a polyurea filler. That’s the method in the UV slab kit’s instructions, and it’s the concrete driveway crack repair for cracks up to 1/4 inch with flush edges.

Here’s how to fix cracks in concrete driveway slabs with that kit:

1. Check the crack

   Lay a straightedge across it. If one side is higher, or it’s wider than 1/4 inch, read the section on driveways that need more than filler first.

2. Pull the weeds

   Pull out weeds and roots, then scrape the soil out of the crack with a screwdriver or weeding tool.

3. Open up thin cracks

   For cracks 1/8 inch wide or less, the kit’s instructions say to grind the crack out to 1/4 inch wide and 1/4 inch deep so the filler has room to grip. Wider cracks skip this step.

4. Clean and dry the crack

   Vacuum out the dust, soil and loose concrete. The instructions say it’s critical that the crack be dry, so work after a few dry days.

5. Prime with urethane

   Wet the inside of the crack with the kit’s urethane. Just wet it, don’t fill it.

6. Pack in sand

   Pour dry silica sand into the crack until it’s 1/4 inch below the surface.

7. Soak the sand

   Saturate the sand with more urethane and let it set for about 30 minutes.

8. Top it off

   Fill the last 1/4 inch with the polyurea filler. It’s thin and levels itself.

9. Scrape it flush

   Scrape any overflow flush with a razor scraper, then keep cars off until it’s ready for full traffic.

If the driveway is new, wait before you start. The urethane’s data sheet says the concrete needs at least 28 days of curing first.

What kind of driveway crack do you have?

Look at the width, the edges and where the crack is before you buy anything. A thin crack with flush edges is a filler job, a straight groove is a joint, and a wide or offset crack is a sign the slab moved.

A thin crack with flush edges is normal. An InterNACHI article says some cracks in patio slabs, walkways and driveways (opens in a new tab) aren’t a cause for alarm, and treats cracks under 1/4 inch with no displacement as not structurally threatening.

Not sure if a line is a crack or a joint? The crack or joint guide shows how to tell.

How do you get rid of weeds in driveway cracks?

Pull them, scrape out the soil, then fill the crack so nothing can grow back in it. Weeds in driveway cracks aren’t only cosmetic: Cornell University’s weed guide lists causing and expanding cracks in pavement (opens in a new tab) among the damage they do.

Cornell’s guide says weeds can be removed by hand, and suggests wetting the soil first for weeds with big taproots. Flame weeding also works on pavement, though perennial weeds may need repeat treatments. If you wet the crack to pull weeds, let it dry out for a few days before you fill it.

Filling is what stops them coming back. California’s Department of Pesticide Regulation recommends that you repair cracks in pavement to help prevent weed seeds from germinating (opens in a new tab). The polyurea’s data sheet lists grass and weed control in driveway cracks and joints as one of its uses.

Will the repair match the color of the driveway?

No. The polyurea top cures gray, so the repair shows as a thin line that’s lighter or darker than the concrete around it. The NRMCA says plainly that repair material will not match the color and characteristics (opens in a new tab) of the original concrete.

You can keep the line thin. Grind thin cracks only to the 1/4 inch width the instructions call for, keep the filler inside the crack, and scrape any overflow flush before it sets.

Some homeowners broadcast sand or dry cement dust onto wet filler to blend it in. The kit’s instructions don’t include that step, and the polyurea is tack free in about 5 minutes at 70°F, according to its data sheet. Since there’s no guidance on how it affects the repair, skip it.

How long before you can drive on a repaired driveway?

About an hour in mild weather. The polyurea top takes light traffic in 30 minutes and full traffic in 60 minutes at 70°F, according to its data sheet, and the concrete needs to be at least 50°F when you apply it.

Cold slows every cure. Park on the street or block the driveway until the full traffic time has passed.

What mistakes make driveway crack repair fail?

Moisture, a crack that was never opened up, and filling a slab that’s still moving cause most failures. Each one has a simple fix.

• Filling a damp crack. The kit’s instructions call a dry crack critical. Wait for a dry spell, not just a dry-looking surface.
• Leaving soil or roots in the crack. Filler bonds to concrete, not dirt. Scrape and vacuum the crack down to clean concrete.
• Skipping the grinding on a thin crack. Filler can’t get into a crack 1/8 inch or narrower, so it bridges over the top and peels off. Open it up to 1/4 by 1/4 inch first.
• Using crack filler in the joint at the garage. The urethane’s data sheet says it’s not meant for expansion joints. That gap needs a joint filler.
• Working in the cold. The polyurea data sheet calls for concrete at 50°F or warmer. Pick a mild day.
• Filling a panel that has moved. If one edge is higher or the panel sank, the crack will open again. Fix the movement first.

What about the gap between the driveway and the garage or house?

That gap is an isolation joint, and it gets a flexible joint filler, not crack filler. The NRMCA says isolation joints separate driveways and patios from sidewalks, garage slabs, stairs (opens in a new tab) and other fixed points so each can move on its own.

When the old filler in that joint rots or splits, rain runs down the gap toward your foundation and weeds move in. Cut out the old filler, set backer rod, and refill the joint with a flexible filler such as a polyurea joint filler kit.

The expansion joint repair guide walks through it, and the backer rod guide covers sizing. The joints guide covers control joints across the driveway.

When does a driveway need more than crack filler?

When it has moved. A panel that has sunk, tilted or heaved, or a crack with one edge higher than the other, means the soil under the slab changed. Filling the crack hides that but doesn’t stop it.

• Sunk or tilted panels. These can often be lifted back into place. The sinking slab guide compares mudjacking and foam lifting.
• Cracks wider than 1/4 inch with flush edges. These need a deeper fill. The large crack guide covers the method, but find out why it opened first.
• Cracks everywhere or a crumbling surface. Patching a slab that’s failing all over rarely pays off. The repair or replace guide helps you decide.

An offset edge is also a trip hazard and catches snow shovels. If a driveway crack lines up with cracks in the garage floor and the foundation wall, have a structural engineer look at the house before you fix the driveway.

How do you keep a driveway from cracking again?

Keep water and salt out of it. Once the repair cures, seal the driveway with a breathable penetrating sealer, keep the joints filled, and go easy on de-icers.

The NRMCA recommends a silane or siloxane-based breathable concrete sealer (opens in a new tab) to protect driveways from freeze-thaw damage. It says calcium chloride and rock salt are acceptable de-icers in moderate amounts, and to never use ammonium sulfate, ammonium nitrate or magnesium-based salts.

The same sheet suggests hosing off salt that cars drop on driveways and garage slabs when the weather allows. Point downspouts away from the driveway edges so water doesn’t soak the soil under the slab.

The sealing after crack repair guide covers which sealer to use over a repair and how long to wait. The driveway sealer guide compares sealers for the whole slab.