How to Repair a Concrete Patio Expansion Joint

An expansion joint gives your concrete room to settle and prevents unsightly cracks.

Concrete is a strong material that forms a stable platform. As a concrete pad settles, it will inevitably sink in some places; this shift will cause cracks in the surface of the concrete. A expansion joint is a saw cut in the concrete that is usually filled with a prefabricated piece of shock-absorbing material that allows the concrete to settle and expand with the ambient temperature without cracking. A damaged expansion joint must be replaced immediately to ensure the protection of your concrete slab.

Things You'll Need

• Concrete saw
• Cold chisel
• Hammer
• Bolt cutters
• Expansion joint
• Caulk gun with construction adhesive
• Razor knife
• Concrete mix
• Water
• Wheelbarrow
• Hoe
• Shovel
• Concrete float
• Plastic sheeting
• Work gloves
• Safety glasses
• Hearing protection
• Face shield
• Dust mask

Instructions

1. Start your concrete saw. Cut a line 3 inches from both sides of the existing expansion joint. Make the lines as deep as the blade of the saw will reach.

2. Use your hammer and chisel to break the concrete between the cuts and the expansion joint. Break the concrete into manageable chunks. Remove the busted concrete and expansion joint from the excavation. Cut concrete wire in the hole with your bolt cutters and discard the wire with the other debris.

3. Use your razor knife to cut the new expansion joint to fit the gap in your patio. Apply construction adhesive to one side of the concrete around the repair site. Press the new expansion joint into the adhesive to fasten the joint to the concrete.

4. Combine concrete mix and water in the wheelbarrow using the amounts recommended by the concrete manufacturer. Stir the mix with your hoe. Shovel the concrete into the trench, being careful not to cover or disturb the expansion joint. Fill the trench to the top.

5. Smooth the new concrete with your float. Re-float the concrete each hour for six hours. Cover the concrete with plastic and let it cure for 48 hours. Remove the plastic sheeting.

Tips & Warnings

• Work gloves and safety glasses are required when working with hand tools.

• Hearing protection, dust mask and face shield are required when using a concrete saw.

References

• Ask the Builder: Concrete Crack Prevention