How to Fill Large Expansion Joint in a Concrete Driveway

Expansion joints play a key role in preventing cracks in concrete driveways. They run through the depth of a slab to allow concrete to shrink and expand with changing temperatures. Typically filled with a semi-flexible material like cork, rubber or pressure-treated wood, large expansion joints must have a tight fit to prevent water from seeping under the driveway. This is a do-it-yourself task that takes about an afternoon to complete.

Hand brush
Wet-dry vacuum
Foam backer rod
Utility knife
Foam backer rod
Putty knife
Self-leveling urethane sealer
Caulk gun
Concrete sealer
Roller brush

Instructions

- 1
  Remove any dirt, leaves and other debris from the large joint with a hand brush. Use a wet-dry vacuum to suck out any remaining loose debris.
- 2
  Cut foam backer rod to fit the length of the joint with a utility knife. The backer rod should be a little wider in diameter than the width of the joint. Lay the material over the top of the joint and push it to the bottom with a putty knife. Once in place, the top of the backer rod should be about one-quarter inch from the surface of the driveway.
- 3
  Attach a tube of self-leveling urethane sealer to a caulk gun. Start at one end of the joint and fill the remaining joint with the sealer. Smooth the surface with the putty knife or a concave jointing tool. Block off the driveway so the joints can set for at least 24 hours.
- 4
  Apply an even coat of concrete sealer over the driveway and expansion joints with a roller brush. The sealer repels water and stains. Wait a day full for the sealer to dry and plan to re-apply it every 2 or 3 years.

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