I'm in the process of building a 7-foot faux stone fence using 4x4 posts, cement board panels, and stone veneer, along with a pergola supported by 6x6 posts. With the frost line at 3.5 feet here in Chicago, I'm unsure how to install the posts. Some videos suggest digging below the frost line and pouring concrete directly with the posts, while others warn that this can lead to rotting. I've also heard about using tube forms for concrete footings and attaching the posts to those. Since tomorrow is concrete day, which installation method is best for ensuring strength and durability?
3 Answers
If you're in a frost area, I highly recommend going with sonitube footings below the frost line and attaching the posts to that. It's a solid approach that reduces both heaving and rotting. Make sure to use pressure-treated wood for longer-lasting posts!
From my experience with fence posts, the biggest issue is typically rotting at ground level. I've had success by pouring concrete in sonotubes a few inches above ground level to keep the wood dry and minimize rot. Also, consider using metal brackets that extend into the concrete and up the sides of the posts to help with sideways forces. That makes a big difference!
Absolutely! The way the metal extends into the concrete helps the posts withstand lateral forces much better than just resting on top.
I'd definitely set the posts in concrete directly. Dig a standard hole—about 8 inches in diameter is fine—and make sure the surface slopes away from the post to prevent water pooling. Leaving the top of the concrete exposed helps too. If you're really worried about rotting, consider using metal posts instead—they're a great alternative!
Yeah, just be cautious with posts resting on a concrete footer because it can create weak spots. It's best to dig down and set them properly.