Stop using that cheap expansion joint filler from Home Depot

I used to grab whatever foam backer rod was on sale at the big box stores for my driveways and sidewalks. After three seasons in the sun here in Phoenix that stuff dried out and cracked, letting water get under the slab. Switched to a closed-cell polyethylene rod from a concrete supply house last summer and it's a night and day difference. The rubbery stuff actually springs back and doesn't let moisture sneak through. Anyone else had their joints fail after a couple years?

3 comments

3 Comments

pat_schmidt601mo ago

My last driveway job in Mesa had the cheap foam rod crumbling after just two summers of 115 degree heat. That open-cell stuff from the hardware store soaks up moisture like a sponge and then turns to dust when it bakes. The closed-cell polyethylene you switched to is the only way to go for desert climates, it actually seals water out instead of wicking it in.

the_rose1mo ago

@pat_schmidt60 nailed it, but there's one thing nobody brings up. That cheap rod also shrinks when it bakes, so you get gaps at the joints that defeat the whole purpose. Closed-cell is the way to go, no argument there.

wyatt_green311mo ago

Hang on, is this really that big of a deal? I mean, yeah, if it crumbles after two summers it's annoying, but we're talking about a foam backer rod. It's like 20 bucks for a whole roll. You're acting like the driveway itself is gonna fall apart because of it. I've seen guys just use old pool noodles cut in half and call it a day, and that stuff holds up fine for years. Maybe people are just overthinking what's basically just a spacer to keep the caulk from sticking everywhere.