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.

Things You'll Need

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

  • 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.

  • 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.

  • 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.

Tips & Warnings

  • Wear safety goggles and gloves when working with the urethane sealer.

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  • Photo Credit Thinkstock Images/Comstock/Getty Images
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