How to Fix a Cement Patio That Sank Toward the Foundation

Use a tape measure to arrange three drill holes in a triangle. Space the two holes closest to the sunken edge at least 1 foot in. All three holes should be spaced evenly and 3 to 8 feet apart from each other, depending on the thickness of the slab. Mark the holes on the sunken concrete with chalk.

Drill three 1 1/2- to 2-inch holes through the chalk marks, using a core drill.

Screw one end of a hose onto the end of a slabjacking pump and attach a clasp to the connection to prevent the hose from coming loose.

Screw a 1 1/2- to 2-inch nozzle on the other end of the hose and push it through the lowest hole until it hits the foundation beneath.

Mix a batch of cement grout made for slabjacking in a wheelbarrow with the amount of water recommended on the instructions. Scoop the grout into the pump with a shovel.

Turn the pump to "On" and pump grout into the lowest hole until the cavity beneath the pavement is filled. Turn the machine to "Off" and repeat this process for the other two holes to fill the cavity beneath the slab.

Return the hose the first hole and turn the machine to "On." With the cavity filled, the pump will pressurize the grout to slowly raise the slab. Continue pumping into the first hole until the slab rises about an inch.

Repeat step 7 on each hole, raising the slab 1 inch before rotating to the next hole, until the slab returns to its original height.

Scoop out any grout inside the drill holes with a screwdriver or other long, narrow tool, and wipe it off with a moist cloth.

Pack stiff mortar mix into each hole with a putty knife and cut the surface off clean with the end of the knife so it’s less noticeable. Block off the patio and give the grout beneath the slab two days for it to set before allowing foot traffic.