How to Repair Frost Heave in Garage Slabs

Wait until the temperature rises above freezing for an extended period of time. The water under the slab needs to be melted before attempting even a temporary fix, otherwise the repair will likely crack quickly after application.

Wash the garage floor thoroughly with warm water and a mild detergent to remove dirt, grease and stains that can interfere with your repair. Pressure washing is another option. Treat any stubborn stains with a chemical solvent. Follow all instructions on the package for safe and effective application. Rinse the garage again after all stains are removed and let the slab fully dry.

Glue plastic injector ports into each crack in the slab at 12-inch intervals. The ports attach to the cracks with an epoxy paste. Fill the crack in between ports with the same paste using a trowel or putty knife. Wait for the paste to dry.

Inject polyurethane foam slowly into the first port. It should be at the lowest point of the floor if the slab is uneven. Continue the injection until you see foam appearing in the next port. Move to the second port and inject more until you see foam in the third port. Continue until all of the ports have been treated. This fills the cracks with a flexible foam that is water resistant and helps bond the concrete together again.

Wipe away any excess foam with a clean rag before it hardens and pull out the injection ports. Wait several hours for the foam to dry and harden.

Dampen the repaired concrete with water from a spray bottle and lay down a 6-foot-long straightedge on both sides of the repair to form a boundary for a concrete overlay.

Apply mixture of 1 part Portland cement and 2.5 parts of fine sand to the repair to cover the cracks and form a thin concrete surface over it. Spread the mixture with a trowel. Follow package instructions on the cement to ensure you use the appropriate amount of water for the surface area you need to cover.