How to Fix Pitted Concrete: Patch, Skim Coat, or Resurface

Small craters in a driveway or patio rarely stay small. If you are wondering how to fix pitted concrete, the short answer is this: clean the surface down to sound material, fill isolated pits with a polymer-modified patch, and switch to a thin skim coat or resurfacer once the damage covers more than about a quarter of the slab. Then seal it, because water getting into the pores is what made the pits in the first place.

The trick is matching the repair to the damage. A handful of popouts the size of a nickel needs nothing more than a trowel and a bag of patching compound. A walkway that looks like the surface of the moon needs a full resurfacing pass. Chipped edges and corners need a thicker, stiffer mix that can hold a shape. Get the diagnosis right and the fix is a weekend job; get it wrong and the new layer flakes off by next spring.

This article covers surface pitting, popouts, light flaking and chipped edges on slabs that are otherwise solid. If large sheets of the surface are lifting off in layers after hard winters, or the slab has cracked and settled, you are dealing with a deeper problem that a cosmetic repair will not solve.

How to Fix Pitted Concrete: Start With the Cause

Before you buy anything, figure out why the surface failed. Knowing how to fix pitted concrete means knowing which of these four culprits you are looking at, since each one points to a slightly different repair.

• Popouts: Cone-shaped holes, often with a broken piece of aggregate at the bottom. A porous stone near the surface absorbed water, froze, expanded and blew out the cap. These are usually isolated and easy to patch.
• Surface pitting from deicers: Clusters of shallow pits, worst where salt or chemical melt was spread or where cars drip slush. Salts pull in moisture and speed up freeze-thaw damage in the top layer.
• Flaking or scaling: Thin patches of the surface paste peeling off, exposing the sand and stone underneath. Often caused by a weak top layer from overworking or adding water during the original pour.
• Chipped edges: Broken corners at joints, steps and slab edges from impact, snow shovels or tires. These need a stiffer repair mortar that can be formed.

Tap suspect areas with a hammer. A clear ringing sound means solid concrete. A dull, hollow thud means the surface is delaminated, and that loose material has to come off before any patch or coating will stick.

Patch, Skim Coat, or Resurface: Choosing the Right Repair

Use the extent and depth of the damage to decide. These are practical thresholds that most concrete contractors work from, not hard rules, but they keep you from spending a day patching two hundred holes one at a time.

A skim coat is a thin, pourable or spreadable layer of polymer-modified cement that bonds to the old surface and gives you a fresh wearing face. It is the right call when pitting is everywhere, because patching individually leaves a blotchy surface that often looks worse than the original damage. A concrete resurfacer is the product most people reach for here; it is designed to go down thin, bond tightly and be finished with a squeegee or broom.

Tools and Materials

• Pressure washer (at least 3,000 PSI) or a stiff brush and hose
• Cold chisel, hand sledge and wire brush for loose material
• Angle grinder with a cup wheel and dust shroud, or a wet grinding setup, for high spots
• Polymer-modified patching compound or vinyl concrete patcher
• Concrete resurfacer for widespread damage
• Bonding adhesive if the patch product calls for one
• Margin trowel, steel finishing trowel and a long-handled squeegee
• Drill with a paddle mixer and clean 5-gallon buckets
• Concrete degreaser for oil stains
• Penetrating silane or siloxane sealer
• Safety glasses, waterproof gloves, knee pads and an N95 or P100 respirator

Step-by-Step: Fixing Pitted Concrete and Popouts

1. Check the weather. Plan for air and slab temperatures between 50°F and 90°F for at least 24 hours, with no rain in the forecast. Direct afternoon sun on a hot slab makes patches set too fast and crack.
2. Remove loose material. Chip out anything that sounds hollow or crumbles under a screwdriver. Undercut the edges of each pit slightly so the patch locks in instead of feathering to a thin, weak edge.
3. Degrease and wash. Scrub oil spots with degreaser, rinse well, then pressure wash the whole area. Surface dirt and old sealer are the most common reasons a repair pops loose.
4. Dampen the slab. Most cement-based patches want a saturated surface that is damp but has no standing water. Wipe out puddles in the pits with a sponge.
5. Mix small batches. Follow the bag ratio exactly and mix only what you can place in 15 to 20 minutes. Adding extra water to extend working time weakens the patch.
6. Fill and pack. Press the compound firmly into each pit with a margin trowel, working it into the sides. Overfill slightly, then strike it flush with the surrounding surface.
7. Match the texture. Once the sheen leaves the surface, drag a damp broom or sponge float across it so the patch blends with the surrounding finish.
8. Cure it. Keep the patch damp for a day or two by misting or covering it with plastic, unless the product says to air cure. Stay off it for at least 24 hours and keep vehicles off for several days.

Applying a Skim Coat for Widespread Pitting

When the damage is everywhere, fill the deepest pits (anything over about 1/4 inch) first with patching compound and let it set. That prevents the skim coat from shrinking into the holes and leaving dimples.

Next, divide the slab into manageable sections using the existing control joints. Tape or place weatherstripping in the joints so they stay open, since covering a control joint invites a random crack across the new surface. Saturate the concrete, remove standing water, then mix the resurfacer to a pancake-batter consistency.

Pour a ribbon of material and spread it with the squeegee in overlapping strokes, pushing it into the pores. Aim for a thickness of about 1/8 inch per coat. Five to ten minutes later, pull a soft broom across in one direction for a slip-resistant texture. A second coat can go down once the first is firm, usually within a few hours; check the label for the recoat window. Work with a helper on larger areas, because the edge of each section needs to stay wet as you move to the next.

Repairing Chipped Edges and Corners

Chipped slab edges and step noses need a repair mortar stiff enough to stand on its own. Pour-and-level resurfacers will slump off an edge. Screw or stake a straight board alongside the damaged edge, flush with the finished height, to act as a form. Coat the board with a release agent or wrap it with packing tape so it pulls away cleanly.

Pack the mortar in layers no thicker than the product allows, usually about 1 inch per lift, and round the corner slightly with an edging tool. Pull the form after the mortar is firm but before it fully cures, then touch up the face with a damp sponge. Repairs on edges that take regular impact, like a garage apron, benefit from being set a hair below the original line so tires roll over them rather than catching the lip.

Sealing to Stop the Pitting From Coming Back

Patching without sealing is a short-term fix. The concrete pitted because water and salt were getting in, and fresh cement is just as thirsty. After the repair has cured for the time listed on the product (often 7 to 28 days), apply a penetrating silane or siloxane sealer. These soak into the pores and repel water without making the surface slick, which matters on walkways and steps.

Beyond sealing, change the habits that caused the problem. Use sand for traction or a deicer labeled safe for concrete, and avoid rock salt on slabs less than a year old. Shovel promptly so snow does not melt and refreeze in place. Make sure downspouts and grading send water away from the slab rather than across it. Reapply the sealer every 2 to 5 years, depending on sun and traffic.

Safety: Silica Dust and Chemical Products

Grinding, chipping and cutting concrete releases crystalline silica, a fine dust that causes serious lung disease with repeated exposure. Use wet methods whenever possible: mist the surface while chipping and choose a grinder with water feed or a shroud connected to a HEPA vacuum. Wear an N95 at minimum, and a P100 half-mask respirator for any extended grinding. Clean up with a HEPA vacuum or wet mopping, never by dry sweeping.

Cement products are strongly alkaline and can cause chemical burns on wet skin, so wear waterproof gloves, long sleeves and eye protection, and rinse any splashes immediately. Degreasers, bonding agents and solvent-based sealers give off vapors: work in open air, follow the respirator guidance on the label, keep flammable products away from pilot lights and open flames, and never mix cleaning chemicals together.

Troubleshooting Common Problems

• Patch sounds hollow or lifts at the edges: The surface was dirty, too dry, or had old sealer. Remove it, grind or etch to fresh concrete, and repeat with the surface properly dampened.
• Fine hairline cracks in the skim coat: It dried too fast. Next time work in the morning, keep it misted and avoid thick single coats.
• Patch color does not match: Fresh cement always reads darker at first and lightens over weeks. For a uniform look, skim coat the whole panel rather than spot patching.
• Pitting returns after one winter: Water is still getting in. Seal, fix drainage and switch deicers.

Cost to Fix Pitted Concrete

DIY spot patching usually costs under $50 in materials for a few dozen popouts. Resurfacing a typical two-car driveway yourself runs a few hundred dollars in resurfacer, sealer and rented tools. Hiring a contractor to resurface generally costs in the range of $3 to $8 per square foot, depending on region, prep and whether a decorative finish is added. Full tear-out and replacement costs considerably more, which is why catching pitting early and sealing afterward pays off.

When to Call a Pro

Bring in a concrete contractor if the slab has cracks wider than about 1/4 inch, sections that have heaved or sunk, large areas that sound hollow, or exposed and rusting reinforcing steel. Those signs point to base failure or deep deterioration that a thin overlay will only hide for a season. A pro can core the slab, check the base and tell you whether resurfacing is worth doing or whether replacement is the better value.