Cracked Concrete Patio? Causes and 5 Fixes

You poured real money into that patio, and it looked flawless the day it cured. Time has been less kind. Now you are staring at spiderweb cracks, a slab that has settled at one corner, or a raised edge that catches every toe in the yard.

Here is the good news. Concrete looks permanent, but the damage rarely is. Below we cover why your patio is failing, how to tell a cosmetic crack from a serious one, and five repair methods that run from a weekend patch to a full pour.

Concrete is tough, but it is not invincible. Weather, erosion, shifting soil, and everyday wear eventually take a toll. Before you grab a sledgehammer, figure out what actually went wrong.

If you skip the underlying cause, any repair you make is a temporary bandage. Here is why patios crack, and how to get yours back to level.

What Causes Cracked and Uneven Concrete?

Understanding the “why” matters as much as the “how.” Concrete usually fails for one of a few specific reasons.

Improper Installation and Curing

The first few days of a slab’s life decide its future. If the concrete is overmixed or poured in extreme heat, the water evaporates too fast and the chemical curing process never finishes.

The result is shrinkage and surface crazing, a network of fine cracks. Keeping the fresh concrete damp, called misting, slows the drying, but adding too much water to the mix itself dilutes it and weakens the top layer.

Ground Movement

The dirt under your patio is always moving. Settlement happens when the soil dries and shrinks, leaving a void under the slab. With nothing to support it, the heavy concrete cracks and drops.

In colder climates, freeze-thaw cycles are the enemy. Saturated soil freezes and expands, heaving the concrete up, then thaws and lets it fall. Repeat that a few dozen times and the slab snaps. Clay soil is especially bad here, since it swells and shrinks more than most.

Loss of Moisture (Plastic Shrinkage)

This one starts right after the pour, but the damage lasts for good. If the surface dries faster than the concrete underneath, the tension tears it apart. That is why installers watch the weather so closely. Pouring on a hot, windy day with no windbreaks or curing retarders invites trouble.

Improper Concrete Mixture

Concrete is not just “wet rock.” It is a recipe, and the ratio has to match the job. Use a walkway mix under a driveway load and it will crumble. You need the right blend of cement, sand, and aggregate (stones) for the weight it will carry.

There are several ways to mix concrete, each producing a different compression strength measured in PSI (pounds per square inch).

Here is a breakdown of common concrete grades and their uses:

Corrosion and Chemical Damage

Concrete is porous, like a sponge. In winter, de-icing salts melt snow into saltwater that seeps in. If steel rebar sits inside, the salt rusts the metal, which expands and pops the surface off in flakes, a failure called spalling.

Using sand for traction is much kinder to your slab than rock salt.

Excess Weight

This ties back to the mix. Drive a heavy truck onto a patio built for lawn chairs and physics wins. The concrete compresses and cracks. If an area will carry real weight, the mix needs more aggregate and steel reinforcement to handle the tension.

5 Ways to Fix a Cracked and Uneven Concrete Patio

Before you pick a method, size up the damage. A hairline crack under 1/8 inch wide is cosmetic and takes filler. A crack wider than 1/4 inch, one that keeps opening, or slabs sitting at different heights can point to a structural problem worth a professional look first. With that sorted, here are the five most effective repairs, from professional lifts to DIY patches.

1. Slab Jacking (Mudjacking)

Slab jacking is the traditional way to lift sunken concrete, and it is a job for a pro. They drill a few 1 to 2 inch holes in your patio and pump a slurry (cement, topsoil, and water) underneath.

The pressure from the slurry lifts the slab back to level it out, then the holes get patched. It is heavy-duty and effective, and usually runs $3 to $6 per square foot, far less than a full replacement. The trade-off is a messier job and bigger patch marks.

2. Polymer Slab Lifting (Polyjacking)

Think of this as the modern cousin of slab jacking. Instead of a heavy cement slurry, pros inject expanding polyurethane foam. It costs more, often $5 to $25 per square foot, but the trade-offs win a lot of homeowners over:

• Smaller Holes: the injection holes are roughly 5/8 inch, so they nearly disappear once patched.
• Lightweight: the cured foam is light, so it does not pile more load onto the already struggling soil below.
• Fast Cure Time: you can walk on the patio almost right away, while mudjacking takes days to cure fully.

3. Patching

For minor surface cracks, you do not need heavy machinery, just some elbow grease. Patching means cutting out the damaged section or widening the crack with a chisel to create a clean edge for the filler to grab.

Then you pack in a concrete patching compound. For cracks between 1/8 and 1/4 inch, laying mesh reinforcing tape in first helps keep them from reopening. Make sure to seal the gap tightly so water cannot get back in. If water freezes in that crack again, it will pop the patch right out next winter.

4. Resurfacing (Veneering)

If your patio sits level but looks rough (pockmarked, discolored, or webbed with fine cracks), resurfacing, sometimes called veneering, is your best move. It lays a fresh face over the old concrete.

For the new layer to stick, prep the old surface hard. Use a pressure washer or a chemical etcher to roughen it up. Some people even drill shallow holes for a mechanical bond, though a liquid bonding agent is usually enough.

Then pour a resurfacing mix over the top. It goes on thin, usually 1/16 to 1/4 inch, and has polymers that make it sticky and strong. Apply it only when the surface and air will hold at 50 degrees Fahrenheit or warmer for a full day, then keep it damp and off-limits for 24 hours while it cures. Broom finish it for texture and you get a patio that looks new for a fraction of a full replacement.

5. Replacing the Concrete

Sometimes a slab is just too far gone. If the concrete has heaved badly, crumbled into rubble, or split with deep structural cracks, you start over.

This one is labor-intensive:

• Demolition: sledgehammer or jackhammer the old slab and haul the debris away.
• Prep: rebuild the sub-base with gravel and sand, tamping it down firmly. This is the single most important step for preventing future cracks.
• Pouring: build a wood form, pour the new mix (a 1-2-3 ratio gives good strength), and screed it flat.

Once it is poured, cut control joints into the fresh slab at about a quarter of its depth, spaced roughly two to three times the slab thickness in feet, so a 4 inch slab gets a joint every 8 to 12 feet. Those joints give the concrete a planned line to crack along instead of a random one. Keep the new slab damp for several days so it cures to full strength. It is hard work, but it fixes the problem for good.

FAQs

Can You Pour New Concrete Over Old Concrete?

Yes, you can pour new concrete over old concrete, a method called resurfacing or capping, as long as the existing slab is structurally sound. Clean the surface thoroughly and use a bonding agent so the thin new layer grabs the old one. If the old slab is still heaving or sinking, that movement telegraphs up and cracks the new layer too, so fix the cause before you cap it.

How Much Does It Cost to Lift a Concrete Patio?

Lifting a concrete patio costs far less than replacing it. Mudjacking generally runs $3 to $6 per square foot, while polyurethane foam lifting (polyjacking) runs $5 to $25 per square foot and averages around $15. Both raise a sunken slab in place, so you skip the demolition, haul-away, and fresh pour that a full replacement demands.

How Long Does Concrete Patching Last?

A well-applied concrete patch lasts roughly 5 to 20 years, depending on the product and your climate. Acrylic and vinyl-reinforced patches hold up well, but if the soil movement or water intrusion that caused the crack is never addressed, the patch fails sooner. Resealing the repair every couple of years stretches its life.

How Do I Keep a New Concrete Patio From Cracking?

Keep a new patio from cracking by getting the base and the joints right. Compact a gravel and sand sub-base firmly before you pour, then cut control joints about a quarter of the slab’s depth and space them roughly two to three times the slab thickness in feet, so a 4 inch slab gets a joint every 8 to 12 feet. Joints give the concrete a planned line to crack along instead of a random one, and keeping the fresh slab damp for several days helps it cure to full strength.

How Wide Can a Concrete Crack Be Before It Is Serious?

A concrete crack turns into a real concern once it passes about 1/4 inch wide. Hairline cracks under 1/8 inch are cosmetic and take a simple filler, cracks between 1/8 and 1/4 inch often want mesh reinforcing tape so they do not reopen, and anything wider than 1/4 inch, uneven across the break, or still growing deserves a professional evaluation before you patch over it.

Choosing Between DIY and Hiring a Professional

Whether you DIY or call a pro comes down to how bad the damage is.

Hairline cracks and surface spalling are a trowel-and-patching-compound job, a satisfying weekend project that saves real money. But a slab that is sinking, tilting, or split by deep structural cracks needs a professional. Mudjacking and polyjacking rely on specialized equipment you cannot rent at the hardware store.

Size up the damage honestly, weigh it against your budget, and pick the path that keeps your patio safe for the long haul.