Rocks are making my post hole digging process horrible


  #1  
Old 08-09-04, 07:45 AM
colpaarm
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Rocks are making my post hole digging process horrible

In an attempt to add tool storage space, I've decided to build a tool shed. I decided to add footings for them to make them stronger. A person building my addition told me that it was overkill and I should just build it on the floor since it was only a 10x12.

Two make a long story short, I drew up my plans and got my building permit. I rented an auger so I wouldn't have to kill myself. Unfortunately, it doesn't dig through rock, which has plagued all 12 of the holes I'm digging. I'm supposed to go down 42" but have not gotten any hole past 30" and some even less than that. I spoke to the building inspector. He basically said that I shouldn't sweat it; just dig as far as you can and then pour the footings.

The thing is, however, the whole point of going below the frost line is to prevent frost heave. This inspector is notoriously nice. However, I don't want an unstable structure becuase of this. I can't quite tell if in every situation it's pure solid rock or just a bunch of smaller rocks.

Here's the deal. How do I get around this? Is my only option to use a jackhammer? If so, how much do they typically run? I'm not even sure if I can get my hands on them where I live (westchester, ny). Unfortunately, I can't use a sledgehammer for the obvious problem of lack of space. Anyway, any thoughts would be greatly appreciated.
 
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Old 08-09-04, 09:56 AM
C
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I don't know about not reaching full depth for the footings, but you should be able to rent an electric jack hammer at the local tool rental shop. It will eat up the rocks.
 
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Old 08-09-04, 12:41 PM
colpaarm
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Okay, I'll see if I can find a place in NY that rents them. Thanks.
 
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Old 08-09-04, 04:17 PM
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12 holes for a 10x12? thats way past overkill. For that size shed i would have poured a 4" at grade pad and be done with it. A jackhammer is going to be hard to controll 30" into the ground.... you will almost need to sit to use it.
 
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Old 08-10-04, 02:27 PM
colpaarm
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Yeah, this is what happens when you follow the home depot book! I understand their logic. I'm only using 2x6's for the floor. I can get away with that because of the number of supports. From a cost standpoint, it's actually a wash. And digging holes is actually easy, believe it or not. Quite frankly, I didn't even need the auger. I can do one every 10 minutes or so. I know this because my wife recently brought some plants that I had to plant. Of course, when a bunch of rocks decide to be right where you want to dig, it ain't even close to being easy.

Now I just spoke to a guy that rents jackhammers. I'm not worried about controling the jackhammer 'cause I'm strong enough. However, he warned me that there's no guarantee that the jackhammer will tackle the rock. He said that where we live, there's a lot of rock that only blasting will get rid of. In his words, "you can jackhammer it all day and you might just be making powder!" Basically, he said that I should get down there with a hammer and chisel. If I can get flakes to come off, then it's something that an electric jackhammer will take care of no problem. If not, take the building inspector's advice and just pour on top of the rock.
 
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Old 08-13-04, 05:29 PM
colpaarm
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Just to give an update, it turns out that my local home depot rents both small and large jackhammers. I practically LIVE in that store and never noticed this. After thinking things through, the only jackhammer that could actually go down 4' with only 12" of diameter to work with was the portable one. So I rented that one. It's a Hilti te 905. It looks like a big reciprocating saw with a long, cold chisel on the end.

When you start it up, it just makes a humming noise and doesn't do anything more. However, as soon as you touch it to anything hard, it gets to work. What's nice about it is that you get almost no vibration. And it ate up the rocks! Just one problem. I would have to work all day to finish breaking up all of the rock. No problem, 'cause the jackhammer's pretty light and does the work. However, with this hurricane stuff going down in florida, I was only able to work on one hole. All of the rain is getting kicked up to NY. Even the one hole I worked on I had to bring the jackhammer in two times because of intermitent rain. So I did some research regarding buying it. I figured a reciprocating saw is about $100-$200 bucks, so this should be within that range. Yeah right! Try over $800!!! You can get it for around $600-700 on ebay used (depending on the auction). So basically, I need to rent this early one morning and make sure that there won't be a drop of rain. Again, with the weather, rain will threaten 'till at least next tuesday. I had a summer friday off from work today and would have loved to finish it today. The funny thing is, when I rented the post hole digger from home depot, it rain unexpectedly that day. Anyway, enough rambling!
 
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Old 08-13-04, 05:34 PM
colpaarm
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Oh, and one more thing. I couldn't just put a four inch pad down for the shed. I have to get a permit to put a shed down where I live and that wouldn't pass. You can do a slab, but it's funny how you have to do it. You have to make a trench and at some points, the thing has to be 16" deep. Trust me, with the amount of concrete you have to mix, you'd be better off getting it pre-mixed. Then, couple that with the amount of digging you'd have to do, you'd be bettter off getting one of those excavators. Finally, if you live in cold climate you may still have to pour footings even if you do a slab to prevent frost heave. It will depend on your building department.
 
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Old 08-13-04, 06:20 PM
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writetovarun,

Our frost line will regularly go down to 8' and over travelled roads and such as much as 12' and no one here uses piles for garage pads.
5" of concrete minimum with a perimeter trench of about 18" wide by 10 " deep is the norm and as long as the ground and gravel cover is properly packed it will never move.
The only time there is ever a problem is if someone takes a shortcut and doesn't remove unstable soil.
 
 

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