PSA: That foam backer rod actually matters for concrete cracks

I always skipped using backer rod when filling driveway cracks with caulk, figured it was just extra cost and work. Then I read on a concrete forum that the caulk needs something behind it to push against or it just sinks down and fails in six months. Has anyone else dealt with cracks coming back because you didn't use backer rod?

2 comments

2 Comments

tessawebb5d ago

Ngl, backer rod also prevents the caulk from sticking to the bottom of the crack.

fiona_murray5d ago

Doesn't the backer rod just create more work though? I've always figured if you're using good quality caulk and you prep the surface right, it'll stick fine without anything extra in there. Seems like adding backer rod is just one more thing to go wrong if it shifts or isn't seated perfectly. Plus, that stuff is a pain to cut and fit into narrow cracks. Honestly, I've had better adhesion just letting the caulk grab the bottom of the joint.