Replacing an Expansion Joint in a Concrete Driveway

Q: Our concrete driveway has an old piece of lumber used to form an expansion joint. The lumber has rotted away. What’s the best way to replace the joint?

A: Use a chisel or putty knife to remove the rotted wood. Sweep the dust and debris out of the seam with a wet/dry vac. Then, pack a strip of foam backer rod into the seam to allow some shifting of the concrete to help prevent cracking. Run the backer rod from one end of the joint to the other. Finally, seal the joint using a caulking gun and a tube of polyurethane sealant. Allow the sealant to fully cure before contact.