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Oskie Boy

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Hello, I have a covered patio project coming up and I need to create footings.  Two of the footings will be in the dirt which will be no problem, but the other four I need to cut through my existing patio.  I need to cut a 12"X12" square or circle and then dig down through the dirt.  It is prob 4 inches thick at least.  Any ideas on how I could get a clean cut? 

 

Thanks,

 

Nic

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Sounds like you are talking about concrete.  Unless you have specialty tools I would drill the perimeter with a 1/2" concrete bit and a few through the center and break it out with a sledge. You will need a lot of holes to weaken the concrete to get the center breakout started.  If you need a really clean edge you can follow up by cutting the top edge with a cheap 4" diamond blade on a grinder.

 

All depends on what you have available for tools.

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11 hours ago, Oskie Boy said:

Hello, I have a covered patio project coming up and I need to create footings.  Two of the footings will be in the dirt which will be no problem, but the other four I need to cut through my existing patio.  I need to cut a 12"X12" square or circle and then dig down through the dirt.  It is prob 4 inches thick at least.  Any ideas on how I could get a clean cut? 

 

Thanks,

 

Nic

could get a laser shovel with anti-grav technology.

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Ok, so let me make sure I have this right.  You need to place footings under your existing wooden deck to support the roof you will be placing over it, right? And of course the deck is too low to  the ground to get under it.

 

If right, instead of cutting into the deck I would just remove the enough existing deck boards to access the dirt. So if the deck boards are 2x4 then you only have to remove three, if 2x6 then only 2. Though removing an extra board or so will make it easier. When finished just replace the boards and notch them around the post for a clean install and no one will be the wiser.

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I have a an old Makita circular saw that I keep just for cutting stucco and concrete. It has a dust port on it that I can hook up to a shop vac to keep dust down. I have a Husqvarna Diamond blade on it. The problem I've run into with a diamond blade on a die grinder is it gives you very little cutting depth, even with the guard off. So I would cut the square in concrete the best I could plunge cutting with a circular saw. 

 

Then as rrmccabe said. I would drill a bunch of holes through the concrete and use a sledge hammer or (I have a Bosch electric chisel hammer) to bust out the center and then use a chisel to clean up the rest of the corners etc.

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55 minutes ago, KnarlyCarl said:

Does the concrete need to be cut for the weight of the new patio? Is the existing cement patio not sufficient enough support?

I am guessing since he said footings he might live somewhere cold like me.  The patio floats and he needs to punch through and go down to get below frost so his covered patio is not moving up and down in the winter.

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Thank you everyone for all of your comments, I should have been more clear.  This patio will have 6 posts, four of which will be on the existing concrete patio which is prob 4" deep, perhaps more perhaps less.  When I went to get a permit I was told the footings had to be a minimum of 12" deep.  One of the posters mentioned "why not just put the post on top of the existing patio? That was my original idea too.  But the permit guy told me I couldn't do that, and it will prob be safer to have a nice deep footing anyway, I actually plan to dig down 24".  My location is Memphis TN, so frost heave is prob not a issue at 12" to 24" deep footings.  I have never had to cut concrete and end up with nice edges.  All I have is wood working tools and I do not want to use them on the concrete.  I like the angle grinder idea and the  skill saw idea.  With the diamond blade.  Get a nice straight line going then start tapping the middle and hope it breaks clean.  I think the angle grinder would be easier to get the cuts started right? But then it would not go as deep as the skill saw.  With the 4.5" angle grinder how deep could I make the cut? Looks like harbor freight has a 9" 15 amp angle grinder. Has anybody used this one? How deep do you think I could get with that? 

 

-Nic 

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Yea that's the problem with an angle grinder. You are only going to get about 1 1/2" deep cut. I suggested it to clean up your cut and make it look good at the top after you have your hole. But you are pretty much going to have to drill through it around the perimeter to get a semi clean break to start with.

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I don't understand why you need a nice clean line or hole? I would make a larger hole with a concrete saw and a jack hammer rent them if need be get your footing job done and then fill the hole again with concrete to be flush with patio

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I don't understand why you need a nice clean line or hole? I would make a larger hole with a concrete saw and a jack hammer rent them if need be get your footing job done and then fill the hole again with concrete to be flush with patio


It depends on the home and the homeowner. If I'm paying for a nice deck for an upper end house, it better not look like some idiot used a jackhammer and poured a sack of quikrete and didn't bother to wash off the post.


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1 hour ago, comp56 said:

I don't understand why you need a nice clean line or hole? I would make a larger hole with a concrete saw and a jack hammer rent them if need be get your footing job done and then fill the hole again with concrete to be flush with patio

Well the point in getting a clean line is to keep the project clean looking, since the new concrete will not match exactly, I am going to bring the footing up fluch with the rest of the patio concrete. If I was not worried about looks I would just use the sledge, but my main goal is to prevent any of the existing patio from cracking. 

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1 hour ago, Mordekyle said:

You'll easily be at it 10 hours for four holes.

Contact a concrete cutting contractor. Have them use a core drill at whatever size you want.

I doubt any rental place has one, but it wouldn't hurt to find out.

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This would prob work perfectly, home depot rents them too. But they do not have the larger model available in my area. The smaller one will do 6" diameter and the big one will do 15".  

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Looks like I can rent a gas powered concrete saw 14" from Home Depot for $72.  For one day.  I only have 12' to cut or 4 12X12" holes. I have never used one so I am sure it will take me all day.  I am glad to pay the $72 to keep my frustrations to a minimum which might not be the case when trying to use a grinder.  Here is the pic from their website, With that 14" blade all I will need to do is lower it into the slab and pick it back up I imagine, Guess it wont hurt if the holes are 14"X14" 

 

 

 

  PRO Gas Concrete Saw 14

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