Setting fence posts in rock

[Steve Foss]

Hey all:

We're starting a 6' wooden privacy fence tomorrow running about 120 lineal feet, and we know that at some point we'll be hitting solid ledge rock. Probably within a foot of the surface in a few of the post holes.

I've been told that using a rock bit and drilling a hole in the rock will work because there are post bases with rods that fit down into the drilled hole, with the 4x4 fitting into the top of the post base.

Anyone have any experience with this? What do you recommend? We'll actually have no problem bracing the fence. We'll be landscaping the whole length of it on our side, and bracing will be hidden in just a few years by shrubs and perennials.

[Steve Foss]

Answered my own question. Two ways I've found are:

1. When digging, once you hit solid rock, drill into the rock with rock bit and bolt in a 4x4 anchor. Drop the 4x4 in the anchor and fill the hole with Quickcrete.

2. If rock is exposed, drill a pattern of holes in a circle, with the holes close together, and when the circle is complete drill out all the rock with a jackhammer. Clear the rock. Repeat as often as necessary to get a hole deep enough.

We've set about 10 of the 15 posts needed for the fence, and all were able to be set well into the ground before hitting ledge, and set in Quickcrete. None of the yard where the fence will be going has exposed ledge, so likely from here on back, where we see more rock terrain, we'll chose option 1. Also, there are mature trees or rock near where each of the remaining posts will go, and because we're going to landscape our side of the fence in shrubs and perennials, bracing the fence, if needed, will be invisible within a couple years. The first 2/3 needs no bracing at all.

When it comes to fence holes, sure wish I was digging them back where I grew up in the Red River Valley!

[Neighbor_guy]

Down here is sand country we just use the ice auger. 5" if no crete, 8" if crete. NO WATER!!! Just tamp the quick crete in and it will take in whats needed to cure.

Up there in rock country, or should I say BoUlDeR country, more work will be needed. I'd offer to help, but I am 247 miles to the south. How 'bout I just ofer some encoragement....

But the reality is I am having rouble just typing today, so I got nothing......

[Steve Foss]

No prob, Matt. I know you'd pitch in and help if you were here!

We were going to rent a power drill but it wasn't available until tomorrow and we didn't want to wait. Saved us $50 doing it by hand, too. Considering tomorrow's expected weather (more rain), I'm really glad we didn't wait. It's a lot easier to put up cross pieces and dog-ear boards if it's wet than it is getting down in the mud to do posts.