Sonotube Cuts

June 17, 2025

In preparation for our upcoming fence post install, I had the job to cut our sonotubes down to size.

Traditionally, fence posts are made out of 4×4 wood posts, and use a 10″ tube. Since we’re using a metal post, the footprint is much smaller, and we ended up going with 8″ tubes.

Because we’re in the Midwest, where the ground freezes and thaws over the winter, we need to dig deep enough to get our posts below the frost line.

Technically I think it’s 4′ – and also, you’re supposed to make a kind of “bell” shape at the base of the hole (imagine the head of a nail or screw). All of this is to prevent the post from getting pushed up, when the ground shrinks and expands, due to the winter weather.

For our part, we’re just going to go with a straight hole, and we’re only going 3′ down. So I’m cutting our tubes down to size.

Liz cut the first tube we used by hand, but I was way too impatient for that. I ended up using the sawzall, and made a kind of impromptu jig on a piece of plywood (that worked out… ok, but could have been better).