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UHF
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Fence posts in limestone

I'm trying to install some privacy fencing. These are 8' wide by 6' tall panels. These to be exact: »www.menards.com/main/building-ma ··· 5774.htm

There's also a section that's 10 feet long and 8' tall.

My problem is that it's very difficult to dig 2 foot deep holes for the fence posts because the ground here is pretty much solid limestone with about 4-6 inches of topsoil.

My question is, how far into the rock do I need to dig? I'm going to use concrete in the holes, so if I can dig down 12-18" is that enough, at least for the posts that aren't on the ends? This is in Iowa, so frost is a concern, but if the post is basically embedded in a foot or more of stone, I can't see it going anywhere. Ideally, I'd want to be 2 feet deep, but I about killed myself getting one hole 12" deep tonight.

I'm gonna try a jackhammer tomorrow. Maybe that will solve the problem.


Jack_in_VA
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join:2007-11-26
North, VA
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Not sure about it but I've seen the wind blow some over around here.


Cho Baka
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join:2000-11-23
there
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reply to UHF
Wrong thread.

robbin
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Leander, TX
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reply to UHF
If you can get a Bobcat or Mini-excavator into the area, then you can use a rock drill. I have drilled 12" holes without any problem in solid limestone using one.

It would help to know your area to even try to give advise regarding strength and depth needed.


UHF
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reply to Jack_in_VA
said by Jack_in_VA:

Not sure about it but I've seen the wind blow some over around here.

Yeah, we do get some serious winds here during thunderstorms. I've measured 80+ MPH here at the house before, and 55+ several times a year.

robbin
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join:2000-09-21
Leander, TX
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I should clarify what I tried to say -- I have drilled 12" diameter holes 4' deep in solid limestone with a rock drill mounted on a Bobcat Mini-Excavator. It isn't quite like a hot knife in butter but it's not really work either. Can't be work when it is so much fun to operate the equipment!


UHF
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I can get a bobcat skid loader up there, but we don't have a drill for it, just a bucket.


UHF
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reply to UHF
As for the area, it's near Waterloo, Iowa. There's a rock quarry less than 1/4 mile from here
The power company actually wrecked the boring equipment trying to run underground electrical service about a decade ago.

robbin
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Leander, TX
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reply to UHF
Check with your local Bobcat dealer. They may rent the drill (they do here) or may know of someone else that does. All you need is the aux hydraulics on the Bobcat to power it.


Dell User
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join:2002-01-21
Waterford, CT
reply to UHF
You might want to look into fence post anchors, to see if they'll work for you.

You dig as far as you can then drill a one inch hole with a mason drill and drive these thing in 6 or 8 inches and bolt the bottom of the post to them.

They used them on my fence when they ran into granite and they have held up well.


UHF
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said by Dell User:

You might want to look into fence post anchors, to see if they'll work for you.

Excellent. I'll look into this. As I was out there with the pick tonight I was thinking that drilling into the rock and using some type of anchor would be cool, but wasn't sure if there was such a thing.

iknow
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join:2012-03-25
reply to UHF
maybe a passive method, like pouring a strong acid(safely!), into the hole which will dissolve the limestone, would work better. less manual labor anyway, and rental of expensive equipment is not required. there is another way, i'm not sure what you call them, but they are used to separate sheets of marble, granite, etc. they go into a small drilled hole, of which a few are drilled, and you hammer them in, starting on one, then continuing to the last one, and they expand, and separate the stone, like wedges. and yeah, dynamite was probably used there at one time, if properly done, it's safe. a very high pressure water jet is another idea, it's used to cut steel and other hard materials, it should have no problem with limestone. you're just unlucky to have to deal with something that most would call crazy.

robbin
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Leander, TX
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Drill rents fairly reasonable if the OP can find one as they already have the Bobcat. Other option is there is a hand held drill available for a compressor but I'm not sure how big of a hole you can drill with it. They mainly use it around here to install T-posts in a drilled hole in the rock.


mityfowl
Premium
join:2000-11-06
Dallas, TX
reply to UHF
A 6' breaker bar will make dust out of that limestone.

Just add elbow (and shoulder, back, legs) grease.

Clean out with your good old clam shell digger.


UHF
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said by mityfowl:

A 6' breaker bar will make dust out of that limestone.

Just add elbow (and shoulder, back, legs) grease.

Clean out with your good old clam shell digger.

Yeah, I've been doing that. It gets old real fast. I think maybe the jackhammer is the way to go. I get free tool rentals so it's worth a try.

robbin
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Leander, TX
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reply to mityfowl
Seriously? Here in Central Texas my 6' rock bar rings like a bell once I get to the solid limestone. Only get tiny chips off of the stone at that point.


UHF
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said by robbin:

Seriously? Here in Central Texas my 6' rock bar rings like a bell once I get to the solid limestone. Only get tiny chips off of the stone at that point.

Exactly. Once in awhile I get lucky and break off a softball sized chunk, but it's usually much smaller pieces.


mityfowl
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Dallas, TX
reply to UHF
said by UHF:

said by mityfowl:

A 6' breaker bar will make dust out of that limestone.

Just add elbow (and shoulder, back, legs) grease.

Clean out with your good old clam shell digger.

Yeah, I've been doing that. It gets old real fast. I think maybe the jackhammer is the way to go. I get free tool rentals so it's worth a try.

Damn straight I would use a jack hammer if I didn't have to pay for it.

Those will do a number on your body too.


nunya
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reply to UHF
I see it done two ways:
1) a walk behind or Bobcat with a 6" core bit. It takes about 10 minutes per hole. Some places rent units that mount to your receiver hitch. They usually go down about 3' max.

2) heavy rod or pipe epoxied into a drilled hole in the rock, and run up into the post.

Remember, concrete around wood (even PT) is an invitation for rot.
--
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Liberty

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Tucson, AZ
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reply to UHF
I frequently need to plant a pole for a satellite dish which has a big sail at top of 6' pole so needs a good foundation

I swear grapes must love rock hard soil because wherever there are vineyards around here, the ground is miserable to dig in

I use an electric jack hammer and small phd
Often times I put a long 3/4" masonry bit in my drill and make a hole or two to give my j-hammer a fracture point - really helps sometimes

I further suggest that you abandon the pre made fence panels - they require pretty precise post placement and digging a hole in rock and adjusting can be a lot of additional hard work
Use schedule 20, 2 3/8" OD fence posts set in concrete
Using 2 bolts per post, bolt a vertical 'stud' on either side of post so that the horizontal members of your fence will align flush

You may likely save some effort on the digging end of project using steel posts and spend most of that time saved in doing the bolting part (which has a lot less sweat in it)
You will also save some $$ building the fence vs buying pre made panels and end up with a sturdier longer lasting fence

If you go the electric j-hammer route, keep in mind how much extension cord you will need
The hammer needs lots of amps and you will need a cord capable of carrying the load


Fronkman
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reply to UHF
I would reconsider my need for that much privacy if I were you.
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UHF
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said by Fronkman:

I would reconsider my need for that much privacy if I were you.

I have a "problem" house next door.


UHF
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reply to nunya
said by nunya:

Remember, concrete around wood (even PT) is an invitation for rot.

I agree.. They are foundation rated PT posts, but still.. Plus, they're from Menards, so quality is already suspect

They'll probably last longer than I'll be at this house.


UHF
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reply to UHF
As I was attempting, rather unsuccessfully, to jackhammer through the rock it dawned on me to ask my neighbor two doors down how he dug the holes for his fence. Turns out he used a 6" core drill.


Anonymous_
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said by UHF:

As I was attempting, rather unsuccessfully, to jackhammer through the rock it dawned on me to ask my neighbor two doors down how he dug the holes for his fence. Turns out he used a 6" core drill.

be sure to call you local gas co to do a survey this way you do not hit any gas lines


UHF
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All the utilities have already been located. Everything here is underground so I always call before I dig.