I need some ideas.

pitt_md · Aug 29, 2009

I am trying to put in a new fence and I run into bed rock about two feet down. Normally I have been able to take a 25 lb. iron bar and beat my way through it. I have spent several hours chipping away at it and there seems to be no end to it. I have tried to move the hole all around the area to find a way through with no luck. Do any of you know if there is some kind of hydraulic jack hammer or something that I could use to get through this stuff?
This is a corner post and I do not believe that two feet deep even set in concret will hold up.

Thanks for any ideas.

MikeInEburg · Aug 29, 2009

If I were in your shoes, I'd probably rent an electric jackhammer and generator. Or clear off a 2'X2' area of the rock and use a hammerdrill - set some pins into the rock to enhance adhesion, and use concrete.
Mike

pat32rf · Aug 29, 2009

You might just have to resort to the old "angle post from the top of the corner post to the bottom of the next one". We often do this with wooden (cedar) corner posts when we have wet soil.....If you are using steel pipe posts then you can do the same, just weld the whole assembly up as a unit..
At least if you are down to bedrock the frost won't heave it.

texasjohn · Aug 29, 2009

There are electric drills that have a "hammer" feature. This means that while the drill rotates it also hammers up and down at a high frequency. You use a concrete/rock drill with a special tip that is hardened to stand the impacts. You can purchase rather long bits... a foot or more. I assume you could get electricity to the site... or have an electric generator....

You are willing to do some work... so, I'd drill several holes, maybe .5 inch diameter, close together... hopefully, you can drill them straight... this would give you several holes into the rock in close proximity. Use your bar to enlarge the area you have drilled sufficient to take the post.

I'd recommend a pipe as the corner post... strong and smaller hole needed than with an 8 inch wood post... and concrete it in... if you can get about 1 foot into the rock, the concrete should hold that post forever.

I'd purchase the drill and bit(s) ... even the generator if you have to... you have hit one difficult hole... likely there will be others.... purchase of these items now likely would be about the same cost as renting a air driven jack hammer... and you have the equipment for future projects and problems.

If you have a Harbor Freight Tools nearby, try there, they have the stuff I mentioned. If not... a box store such as Home Depot, Lowes, etc.

AchingBack · Aug 29, 2009

I once saw a stretch of fence set on rocky ground. The posts were set in 55gal. drums filled with rock. Concrete would be heavier though.

JoeinTX · Aug 29, 2009

This is what the professional fencers use:

Air Compressor Rental, Compressor Rental | United Rentals

You should be able to rent one from any major rental lot but I don't know what they charge since I've never used one myself.

donawilcox · Aug 30, 2009

There are several options. Home Depot rental has several of them.

first is an electric jack hammer. They should care a Hilti 905. or at least that is the older number. it ways 25 lbs. They also rent a Hilti TE 76 hammer drill/chipper. They also have a core bit for that and should have a
3"-4" cores. The only issue is they are only about 4" deep an then you have to clear it out. Just make sure to get the chisels along with the core bit if you go this way.

Then there are diamond core rigs. I have heard of these mounted to bumpers. They are designed to be mounted to a concrete slab where you are drilling. Some use water but also can get dry ones.

Another option as one said id the rock is sold you could anchor to it. Hilti makes a two part epoxy. it is strong stuff. This epoxy is actually stronger if say you epoxied a piece of rebar in a concrete vs putting the rebar in when wet. The RE500 can even be used under water. Great stuff. on this route if you go metal post you could epoxy in some 1/2 rebar and weld to them or set some all thread and put a plate down. if going wood you could set a piece of larger rebar in the rock and then drill a hole in the post and slide it over it.

some home depots have hilti reps in them that can help you with this. I use to be one about 4 years ago but they are only in a limited number. There are also hilti centers. in major cities.

Now that I have given you the options my recomendation would be the large hammer drill/chipper and a core bit and chisels.

Later

pitt_md · Oct 5, 2009

Just an update of how I chose to go about getting these posts into the rock.

I bought this electric jackhammer and it went through layer after layer or dense rock like it was peanut brittle. The price of renting a gas powered unit was 150/day. This one cost me $175. It weighs in at about 50 lbs and can be beast to handle but it does what it says it will.

teg · Oct 5, 2009

Where did you end up buying it from?

Captinjack · Oct 5, 2009

Boy what model is this and where can you get one? I have a need myself, but even Harbour Freight costs over $400.

RalphVa · Oct 5, 2009

I'd rent an electric hammer drill. Then put a stud bolt in the bottom of your fence post into the hole you've made in the rock. This plus cementing around the fence post down to the rock should hold it in place.

I put in one of those safety pool covers about 3 years ago. I used my own hammer drill to drill the 4 corner holes. Took me forever and went through 2 drill bits.

I rented a huge hammer drill and was supplied with a concrete bit for it. I did all the other approximately 30 holes in less than 30 minutes. Using the proper equipment will save you lots of time.

Ralph

texasjohn · Oct 6, 2009

Thanks for the update...yep, where do you get one of these electric jackhammers??

Just2quickz28 · Oct 6, 2009

There is this stuff called Dexpan that is a non blasting demolition foam. I have not used it but looks like it may work.
Dexpan Non Explosive Demolition Agent, Non Explosive Demolition Agent Dexpan, Dexpan Demolition No Explosive

AndyMA · Oct 6, 2009

Dexpan works great

Andy

AndyMA · Oct 6, 2009

pitt_md said:
Just an update of how I chose to go about getting these posts into the rock.

I bought this electric jackhammer and it went through layer after layer or dense rock like it was peanut brittle. The price of renting a gas powered unit was 150/day. This one cost me $175. It weighs in at about 50 lbs and can be beast to handle but it does what it says it will.

So how do we get one?

Andy

pitt_md · Oct 6, 2009

AndyMA said:
So how do we get one?

Andy

Andy,
I did a Google search for electric jackhammer and came up with many places that sell this same model. I got mine from this site. Industrial-Grade Electric Demolition Jack Hammer with 2 Heavy Duty Chisels | eToolscity

This is a Neiko model 2845. When I got it I checked the oil level and needed to add some. I took the plug out and the o-ring was dry and broken. I bought a new one from my local hardware store for $0.29 and everything was good to go.

Baby Grand · Oct 6, 2009

Low tech, slow but steady method:

1) Go to the store and buy beer & hotdogs - lots of beer.
2) Fill your FEL with water and park it right close to the rock.
3) Call some friends over.
4) Start drinking the beer - don't forget to share.
5) With your friends, clear out a 3 foot diameter pit over the rock.
6) Make sure to get all the soil off of the rock's surface.
7) Build a hardwood fire in the pit; right on top of the rock - the hotter the better - and keep it going. Remember - hot! Throw in coal if you have any.
8) Cook & eat the dogs.
9) Drink more beer.
10) After about 6 hours, when the beer is all gone and your friends start talking about leaving, dump the FEL full of water right into the fire pit. That should break up the rock down 6" or more pretty well.
11) Repeat as required until specified depth is achieved.

This worked for the Romans & it will work for you.

-Jim

ultrarunner · Oct 6, 2009

pitt_md said:
Andy,
I did a Google search for electric jackhammer and came up with many places that sell this same model. I got mine from this site. Industrial-Grade Electric Demolition Jack Hammer with 2 Heavy Duty Chisels | eToolscity

This is a Neiko model 2845. When I got it I checked the oil level and needed to add some. I took the plug out and the o-ring was dry and broken. I bought a new one from my local hardware store for $0.29 and everything was good to go.

I just ordered one... I will let you guys know when it gets here.

I've got a bigger Bosch that I don't use as much as I should because it's big and heavy...

pitt_md · Oct 7, 2009

ultrarunner said:
I just ordered one... I will let you guys know when it gets here.

I've got a bigger Bosch that I don't use as much as I should because it's big and heavy...

I hope you get yours quicker than I did. I had it shipped standard ground and they gave me a 3 day window that it should arrive in. the last day of the "arrival window" was 9/23. I got mine on the 28th.

Eaglebait Ranch · Oct 7, 2009

Great Thread! I like what I have read. I am smiling because I have major, major hard pan at about 18". Really, really difficult to fence in pastures. But, I also have all the softball size rock anyone could dream of having. So, I clear the pastures of the rock and on the 10 acres of pasture I have (at last count) 67 rock jacks of about 30"-36" in diameter holding up "T" posts and corner posts. Any of you guys need any rock for rock jacks, let me know.