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I’m a remodeler who just moved from South Carolina to the North Carolina mountains. I’ve got a job that requires setting a 4X4 post into a very large boulder.
I’ve never had to deal with this type of problem before so I was hoping someone could give me some ideas on how this is normally done. All I can think of is blasting a hole in the boulder and filling it with concrete and a connector (“J” bolt) for the post. However, I’m concerned about frost heave if I do this since it’s above grade.
I’d appreciate any ideas you’ve got.
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Dear John,
Blasting a hole would be a trick and a half and highly unlikely. You might end up remodeling the neibourhood instead.
Core drilling is a possibility, one of many I guess.
My comment would be, why not install a U bracket instead, directly on top of the rock and anchor it with standard anchor bolts?
A lot cheaper and much safer. Whether you blast or drill to install your post into the rock or you attach the post to the surface, via a bracket, I doubt very much that frost would factor into moving anything that solid.
Just another thought
Gabe
*John,I wish I could see what you are trying to do but from what I gather i would suggest drilling into the boulder, setting a rod into it and then setting your post over the rod. Is there a reason in particular that you need to set it into the boulder? I also agree with Gabe as far as frost not lifting the post out of the boulder however it could quite possibly lift the boulder or even worse, water can enter the hole you cut and freeze and expand and split the boulder. Try posting a simple sketch for us to see and explain things a little more in detail.Pete Draganic
*I second Mr. Pete, and would consider using epoxy to attach the rebar (or whatever rod you would use)to the boulder. Mix the epoxy, pour it into the hole, then insert the rod for a full bond.The epoxy would give a better seal than cement in terms of preventing water migration into the hole, thus minimizing future splitting or spalling of the stone.I've seen a few jobs done this way, one I know of was done back in '82 and is still holding tight.
*Gosh, give a guy a break. Pete and Mongo, you told him my idea before I could.
*I agree with the above. However if you still require to a actually sink a hole into that there hard beastie, try this. Mark your position on the rock. drill a series of holes to the depth you require the post to go.Fit as many holes in as you can. Youv'e now created a series of weak points for the rock to fracture to. Use a long pointed cold chisel ( round) to work out the rubble, ( work from the centre out ) then clean up the edges with a flat faced cold chisel. Make sure you wear safety glasses.
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I'm a remodeler who just moved from South Carolina to the North Carolina mountains. I've got a job that requires setting a 4X4 post into a very large boulder.
I've never had to deal with this type of problem before so I was hoping someone could give me some ideas on how this is normally done. All I can think of is blasting a hole in the boulder and filling it with concrete and a connector ("J" bolt) for the post. However, I'm concerned about frost heave if I do this since it's above grade.
I'd appreciate any ideas you've got.