Tool Choice Help

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

welcome to the forums, I would use a sawzall draw out your circle drill a hole large enough on edge of circle and slowly cut around with sawzall. 

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.

oh that makes sense concrete deck not wood …lol

For demo it may be a better option to rent a jack hammer. If you have an air chisel or sds hammer drill with a chisel mode those may work as well. You’ll wanna make sure you do the perimeter first before you start hammering away.

Cut your hole’s perimeter with a grinder and a diamond blade and then drill holes in the piece to be broken up and use a sledge hammer or use a jack hammer or other smaller electric hammer to break it up.

I would say a diamond blade on a angle grinder and cut out the square and then just use a sledge to break up the concrete square

Oskie Boy wrote:

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.

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 2×4 then you only have to remove three, if 2×6 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.

He never said deck.  Cutting through existing “patio” that is 4″ thick or more tells me is concrete.

rrmccabe wrote:

1 hour ago, rrmccabe said:

He never said deck.  Cutting through existing “patio” that is 4″ thick or more tells me is concrete.

 

 

 

 

Crap…your right. Hit the reply button a little to quickly.

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

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.

KnarlyCarl wrote:

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.

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 

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.

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

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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IMHO, the harder part will be matching the concrete, whether broomed or exposed aggregate.


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comp56 wrote:

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

comp56 wrote:

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. 

Mordekyle wrote:

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″.  

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″ 

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Could you use the 6″ core drill and then use post bases?

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how close is the footing going to be near the edge of the patio? 

comp56 wrote:

3 hours ago, comp56 said:

how close is the footing going to be near the edge of the patio? 

Two of them will be only 18″ from the edge of the patio, but the other two will be about 14′ from the edge. The patio is attached to the house, so when you walk out of the house there is patio for 14′ and then the edge.  I see where you are going with this I think, just dig under the patio from the side and pour concrete under it.  If it was not for the two closest to the house that is what I would do.  Thanks -Nic

if the patio can hold the weight i would go with the diamond pier foundation system, code approved, no digging, no concrete, all you will need to do is drill four holes through patio at an angle (lol)

if the patio is a problem with weight, trace outline of diamond pier cutout slab, place pier on ground install rods, get selfleveling polyurethane ext. calk, comes in a bunch of colors, pour around pier for water tight seal

Now knowing the rest of the story and that inspectors are involved I would just rent a quickie saw.  Depending on the depth of concrete you will probably have to overcut your 12″ box to get a full depth cut. That means you are going to get short cut lines outside of your 12″ box the width of blade.  These are easily filled using the fines from the concrete for footings or later using a cement patch mix without the large aggregate in regular concrete.

In reality you will need need to make sure the existing concrete and new concrete do not bond together. Separate with sonotube or use expansion joint. Because of frost they are going to move up and down at different rates. In theory the footing wont move and the slab of course will rise.

rrmccabe wrote:

14 hours ago, rrmccabe said:

 

 

In reality you will need need to make sure the existing concrete and new concrete do not bond together. Separate with sonotube or use expansion joint. Because of frost they are going to move up and down at different rates. In theory the footing wont move and the slab of course will rise.

rrmccabe   I was actually planning on just filling the footing flush with the rest of the patio.  The existing patio is 20 plus years old and I live in Memphis TN so it does not get that cold, if they move will they not just move together? Is it not okay if the footing and the existing patio bond together? I guess I could make a square form out of 1/2″ material and pull it out after a few hours? Then I could fill the joint with driveway caulking or something?  I was not concerned with the heaving until you mentioned it.  

Well we have more frost in Iowa than you do (42″ for footings) so its a bigger deal for me than you. But you want to make them float independently.

In a perfect world you would think when the frost goes out the patio drops back down in the summer months. Around here is not uncommon to see a sidewalk or drive lift against a house or garage slab 1 and sometimes even 2″.   If that joint is not forgiving and either gets debris in it or fractures off some of the concrete from the joint when the frost goes out the patio hangs up on the footing leaving a void under your patio which leads to cracks.

So whatever you do, you want to make sure that patio can move up and down without issues. Expansion joint is the most common around here but I suppose you could leave a void and fill it with a urethane expansion caulk.