How to Level a Settling Concrete Patio

Settling occurs when the soil beneath your patio compacts or washes away, leaving your concrete slabs unsupported and prone to cracking. Ignoring these voids allows water to pool, which eventually leads to deeper erosion and larger structural failures. When handled early, you can stabilize the slab before the concrete snaps under its own weight. Successfully leveling a patio is about filling the negative space without adding unnecessary pressure to the foundation. You aren't just pushing the slab up; you are creating a new, stable base that mimics the density of compacted earth. Once you finish, the slab will be supported, level, and far less likely to shift during the next rainy season.

1. Find the Hollow Spots. Walk the patio with a heavy metal bar, tapping the surface to identify hollow-sounding spots. Mark these areas with chalk to plan your injection hole layout.
2. Create the Access Points. Use a hammer drill with a masonry bit to bore 5/8-inch holes through the slab in a grid pattern. Space the holes roughly 2 to 3 feet apart, concentrating on areas where the settling is most severe.
3. Mix and Connect Your System. Set up your two-part polyurethane foam kit according to the manufacturer's pressure and temperature requirements. Connect the injection hoses to the mixing nozzle, ensuring the lines are clear of debris.
4. Raise the Slab Slowly. Insert the nozzle into your first hole and begin injecting the foam slowly. Watch for movement in the slab and stop immediately once you feel resistance or see the concrete begin to shift.
5. Work Hole by Hole. Move to the next hole, repeating the process until the entire section is level. Allow the foam to expand and harden completely, which usually takes about 15 minutes.
6. Seal and Blend the Holes. Remove the injection nozzles and fill the holes with a color-matched concrete patching compound. Smooth the patch with a small trowel to blend it into the surrounding texture.