Concrete Driveway Repair: How to Fix and Resurface a Cracked Driveway

Most cracked concrete driveways can be repaired instead of torn out. If the slab is still level and the cracks are not opening wider every season, you clean the concrete, prime it, fill the cracks with a flexible rubber patch, and topcoat the surface. This guide walks through concrete driveway crack repair step by step, explains when a driveway is past saving, and covers steps, sidewalks, and walkways that need the same fix.

Why concrete driveways crack

Every driveway cracks sooner or later. Concrete shrinks as it cures, and it keeps moving with temperature for the rest of its life. The common causes:

• Freeze-thaw cycles. Water soaks into the pores and cracks, freezes, and expands by about 9 percent. Each winter the cracks get a little wider and the surface starts to flake.
• Tree roots growing under the slab push it up from below.
• Soil settling or washout. When downspouts or poor grading send water under the driveway, the base erodes and the slab loses support.
• Heavy loads. Moving trucks, dumpsters, and RVs crack slabs that were poured thin.
• Deicing salts that cause scaling and pitting on the surface.

Rigid patching products, like cement crack filler and hard epoxy, do not move. Concrete expands in summer and shrinks in winter, so a hard patch either pulls loose from the edges or the slab cracks again right next to it. That is why the same crack gets “fixed” every spring.

Repair or replace: check these first

Repair makes sense for most residential driveways. Walk the slab and look for:

• Hairline and shrinkage cracks up to about 1/4 inch wide. These are cosmetic and easy to fill.
• Wider cracks where both sides are still level with each other. These can be filled and sealed.
• Surface scaling, pitting, and spalling where the top layer has flaked off. A resurfacing coat covers these.

Consider replacing a section if one side of a crack has dropped well below the other, the slab rocks when you drive over it, or large pieces are broken loose and sitting on hollow ground. Fix the cause first in those cases (drainage, a washed-out base, a tree root), because no coating will hold up a slab with nothing under it.

What you need

• Pressure washer, stiff push broom, and a degreaser for oil spots
• Muriatic acid, a plastic watering can, baking soda, and safety gear (acid-resistant gloves, goggles, and a respirator)
• Wire brush or shop vac to clean out cracks
• PermaFlex for the primer and topcoat (240 sq ft per gallon per coat on concrete)
• LRB (Liquid Rubber Base) and TAV (Thickening Activator) for the crack patch
• Heavy-duty zip-loc bags or a mortar bag, a putty knife, and a roller or squeegee

Use the crack filling calculator to figure out how much LRB/TAV mix your cracks will take. Enter the length, width, and depth of each crack.

How to repair a cracked concrete driveway, step by step

1. Clean the concrete

Prep is the most important part of any concrete driveway repair. Mold, mildew, oil, and ground-in dirt all keep a coating from bonding. Pressure wash the whole slab. Scrub oil spots with degreaser and wash them again. Remove any old sealer or paint, because the primer has to soak into bare concrete.

2. Acid etch

Acid etching opens up the surface of the concrete so the primer can penetrate. Dilute muriatic acid with water to a 10 percent solution, always pouring acid into water and never the other way around. You need about a gallon of diluted acid for every 200 square feet.

Wet the concrete first. Pour the solution on evenly with a plastic watering can and work it in with a push broom. It will foam. When the foaming stops, rinse with a pressure washer, then neutralize with 1 cup of baking soda per gallon of water and rinse again. If the acid beads up instead of foaming, something on the surface (sealer, oil, curing compound) is still blocking it, and that area needs more cleaning. Our full guide to acid etching concrete covers mixing, safety, and testing the surface. The video below shows the process.

3. Clean out the cracks

Take extra time on every crack, no matter how thin. Wire-brush the edges, pull out weeds and loose chips, and blow or vacuum out the dust. The patch can only bond to clean, sound concrete. Let the driveway dry completely before the next step. A sunny day or two is usually enough outdoors.

4. Prime with PermaFlex

Roll or squeegee one coat of PermaFlex over the whole driveway at 240 sq ft per gallon. PermaFlex soaks into the pores and acts as a binder inside the surface, locking weak and dusty concrete together. Work it into the crack walls too. PermaFlex can be thinned with acetone (or xylene where it is allowed) to help it penetrate deeper on dense concrete. Never thin it with water or alcohol.

5. Fill the cracks with LRB/TAV

Mix 2 parts LRB with 1 part TAV. That gives the thickest mix, about the consistency of silicone caulk. Use less TAV for a runnier mix that flows into narrow cracks. Put the mix in a heavy-duty zip-loc bag, clip a corner, and pipe it into the cracks like a cake decorator. A large bag holds about a gallon. Smooth each bead with a putty knife.

Most cracks and control joints take a 3/4-inch bead. Where the driveway meets the garage slab, the house, or a curb, run a 1-inch bead. Mixed LRB/TAV has a pot life of about an hour, so mix in batches you can use. It cures to solid rubber in about 4 hours at any thickness, and it stays flexible, so it stretches and recovers as the slab moves instead of breaking loose.

You can also pour straight LRB over low spots and rough, pitted areas to level them. It self-levels and cures at any thickness.

6. Topcoat

Once the patches have cured, roll a topcoat of PermaFlex over the entire driveway at 240 sq ft per gallon. This ties the patches and the old concrete into one seamless rubber membrane. Driveways and ramps get wet, so add texture for grip: broadcast rubber granules into a wet coat of PermaFlex, then lock them in with more coating. Our slip resistant floor covering page shows the textured finishes.

7. Let it cure

The surface can take foot traffic about 6 hours after the final coat. Wait about 24 hours before you drive on it. Cooler weather slows curing, so give it longer in spring and fall.

Repairing concrete steps, sidewalks, and walkways

The front steps and the walk to the door usually crack at the same time as the driveway, and the same products fix them. Steps take a beating at the edges and corners, where chunks break off the nosing. To rebuild a broken edge, prime the step with PermaFlex, build a form from plywood wrapped in plastic sheeting (SANI-TRED will not stick to the plastic), and fill it with a mix of 1 part LRB to up to 3 parts silica sand. Pull the form once it cures, then texture and topcoat the treads. Our step-by-step guide to concrete step repair and resurfacing has the full process, including how to texture only the treads and leave the risers smooth.

Sidewalks get the driveway treatment. One example: a golf club in Ontario, Canada had a pitted entrance walk with a crack running from the corner of the clubhouse across the whole slab. The contractor, HC Products, primed the slab with PermaFlex, filled the crack with LRB, and then applied a decorative concrete overlay on top to cover the pitting and give the entrance the look the club wanted. The crack did not come back through the overlay.

Keep the driveway from cracking again

• Send water away from the slab. Extend downspouts and fix low spots where water pools along the edges.
• Seal the joints. Fill control joints and the gap along the garage and house with a flexible rubber sealant. See our concrete joint sealer page.
• Go easy on deicers. Shovel first and use sand for traction where you can. Never use deicers made with ammonium nitrate or ammonium sulfate on concrete.
• Seal bare concrete you are not coating. For sidewalks and patios you want to keep looking like plain concrete, a penetrating concrete sealer soaks in and repels water and salt without changing the color.

Frequently asked questions

What is the best way to repair cracks in a concrete driveway?

Clean and dry the crack, prime it, and fill it with a flexible material that bonds to the concrete. Rigid fillers crack again as the slab moves. A rubber patch like LRB/TAV stretches with the concrete and stays sealed.

Can you resurface a cracked concrete driveway?

Yes, as long as the slab is stable. Fill the cracks first, then coat the whole surface. Resurfacing over unfilled cracks just lets them show through again.

How long does a concrete driveway repair take?

Plan a weekend. Day one is cleaning, etching, and drying. Day two is priming, patching, and topcoating. You can walk on it in about 6 hours and drive on it after about 24.

Should I fill driveway cracks before winter?

Yes. Open cracks let water in, and freezing water widens them. Do the work while daytime temperatures are still mild so the concrete dries and the coatings cure properly.

How wide a crack can I fill myself?

LRB/TAV fills cracks and joints of almost any width because it cures at any thickness. The limit is the slab, not the filler. If one side of the crack has sunk or the slab moves under a car, fix the base first.

Repair your driveway with SANI-TRED

SANI-TRED is a liquid rubber system that soaks into concrete, bonds to it, and cures into a flexible rubber surface with up to 590 percent elongation. Driveways move, and SANI-TRED moves with them. Products are solvent free, non-flammable, and low VOC, and the system is built for do-it-yourselfers with phone support from our techs.

• Read our driveway crack repair and resurfacing guide
• Coating the garage floor too? See the garage floor coating system
• Estimate your patch material with the crack filling calculator
• Buy PermaFlex, LRB, and TAV in the SANI-TRED shop
• Call 1-866-784-3308 to talk through your driveway with a SANI-TRED tech

Sources: Portland Cement Association (PCA), guidance on freeze-thaw and deicer scaling of concrete; U.S. Geological Survey (USGS), water expands about 9 percent when it freezes.