Ran into a retired guy at the hardware store who had a killer trick for setting posts in clay

I was grabbing some concrete bags in Spokane last fall and this older guy saw my work shirt. He said, 'Son, you mixing that whole bag for a corner post in this gumbo?' I told him yeah, and he shook his head. He told me to dig the hole a foot wider than usual, line the bottom with 3 inches of gravel for drainage, and then use only half a bag of mix, but let it cure for a full 48 hours before putting any weight on it. Said the gravel stops the post from heaving as much when it freezes. Tried it on a job two weeks ago and those posts are rock solid. Anyone else use a gravel base in heavy clay soil?

2 comments

2 Comments

abby18910d ago

Ever try using a bit of sand in the mix too? I mean, it helps the concrete grab better in that slick clay, at least in my experience. Makes a solid post even with less mix.

paulm9510d ago

Used to skip the sand thinking it was just filler. Tried it last season on a gate post in pure gumbo clay, and the difference was crazy. That post hasn't budged a millimeter, even after all the spring rain.