# Cutting receptacles in block walls



## 6 shooter (Feb 4, 2008)

I have to install two circuits in a block wall for a blender and a refrigerator. I would use a 2 gang masonary box in the void of the block. My question is what is the best way to cut out the block. The other is do you use a mortar mix to secure the box in the wall?


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## Bkessler (Feb 14, 2007)

cutting the holes are easy, you can score with a diamond blade and then just tape with a hammer, or you can just drill a bunch of 1/4" holes around the outline of the box and then finish it off with a few taps from your hammer. Try and put the box off center from the center of the cell that way you have something for the mortar to adhere to. Hope you don't find a piece of rebar in your way.


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## jw0445 (Oct 9, 2009)

Surface mounting would be easier. If you need to flush mount I'd take a 4 1/2" angle grinder and scribe the block with it as deep as you can, then take a demo chisel on a Hilti to knock out what you need or a chisel and hammer if you don't have a Hilti. Stuff the holes in bottom of the block with paper or rags before mortaring the box in.


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## 6 shooter (Feb 4, 2008)

jw0445 said:


> Surface mounting would be easier. If you need to flush mount I'd take a 4 1/2" angle grinder and scribe the block with it as deep as you can, then take a demo chisel on a Hilti to knock out what you need or a chisel and hammer if you don't have a Hilti. Stuff the holes in bottom of the block with paper or rags before mortaring the box in.


What would stuffing the bottom of the block be for? Do you fill the hole void with mortar.


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## McClary’s Electrical (Feb 21, 2009)

6 shooter said:


> What would stuffing the bottom of the block be for? Do you fill the hole void with mortar.


 

If you don't do that, it might take a wheelbarrow of mud to fit in one box


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## 6 shooter (Feb 4, 2008)

After the hole is cut the wire is stubbed in do you fill the hole in with a triangle trowel with the mortar? Then in bed the box? What would keep the mortar from falling out or does it stay in the hole nice?


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## jw0445 (Oct 9, 2009)

6 shooter said:


> After the hole is cut the wire is stubbed in do you fill the hole in with a triangle trowel with the mortar? Then in bed the box? What would keep the mortar from falling out or does it stay in the hole nice?


It will stay in as long as you don't make it too sloppy. Make a stiff mix.


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## John Valdes (May 17, 2007)

I knock out the hole with a ball peen hammer. Saws are to dusty. I pull the cables up and secure the connector or connectors and the cables.
Then I fill the bottom with newspaper. I mix up some mortar mix thick. I put a whole bunch in first and then push the box in while guiding the cables back down. (I get help for this) You want mud coming out of the sides. Secure. It's not the easiest of jobs, but if you gotta do it.


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## amptech (Sep 21, 2007)

I have always cut the hole using a 4" grinder and chisel, drilling the corners with a 1/4" bit. For securing in the block I use a box with ears and wedge door shims on both sides of the box then caulk the gap around the box with masonry adhesive. If you can cut the hole neat and square, T&B makes battleships with 3-1/2" fingers that work well.


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## thegoldenboy (Aug 15, 2010)

The way I've been shown to do it is by using a 4 1/2 angle grinder with a diamond blade, cut out the opening and dry fit the box first. After you dry fit it take it out and apply a heavy bead of PL around the opening, reinstall the box and shim as necessary. Once the PL has had time to set up, go back and trim the shims and excess adhesive as needed.


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## 220/221 (Sep 25, 2007)

I'd simply bang the hole with a hammer and screwdriver/chisel. 

Make the hole nice and tight and drive some shims in the sides or top/bottom to secure it. You won't be able to get enough mortar around the box to secure it unless you beat a really big hole.

Actually, a two gang handy box with rounded corners may be a better choice. You can make your opening a bit small (1/8") then beat the box into place by striking the corners alternately. That's the way we did it in the olden days.


Oh yeah...make sure the cell isn't grouted solid befor you start. Drill a couple 1/4" holes first.




> I've always *wiremolded* or surface mount emt'd something like that.


GAH!! BLASPHEMY!!


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## miller_elex (Jan 25, 2008)

Jeebus! I've always wiremolded or surface mount emt'd something like that.

Of course here its standard to fill the blocks.


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## Control Freak (Mar 8, 2008)

How are you getting the cable down? Snaking through existing block?

We never really recess boxes in block unless the wall is going up as we are roughing it out.....in that case we just have the brickies do the cuts and mortar and just keep adding in nipples to the conduit every 3 courses of block or so.

Ive never run cable down block walls only conduit...........usually gal. do not be mistaken..... I am NOT saying its wrong to run cable down block walls.


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## MDShunk (Jan 7, 2007)

I always secured masonry boxes in old work with PL Premium adhesive (like Liquid Nails) or lately I've been using a similar product called Power Grab because it is white in color. 

For making the cutout, I mainly either use a bunch of 1/4" holes or a hammer and chisel. A few well-placed hammer blows will do most of the work making the major hole, and the chisel will clean it up. Unless you're a moron, you understand how concrete block are made, and you'll stay away from the web.


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## MDShunk (Jan 7, 2007)

Control Freak said:


> How are you getting the cable down? Snaking through existing block?
> 
> We never really recess boxes in block unless the wall is going up as we are roughing it out.....in that case we just have the brickies do the cuts and mortar and just keep adding in nipples to the conduit every 3 courses of block or so.
> 
> Ive never run cable down block walls only conduit...........usually gal. do not be mistaken..... I am NOT saying its wrong to run cable down block walls.


Depends on the occupancy type, but either MC or UF. Whatever it takes. You definitely need to be ginger with MC, though. It often takes a guy to feed in and a guy to pull the string with a deft touch. Unless they've poured a bond beam, you shouldn't have a huge problem if you do it with care.


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## merlin1926 (Oct 29, 2010)

That's what we do here,brick layers cut the block and place the box for you.If it is existing either surface mount or nothin.


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## MDShunk (Jan 7, 2007)

merlin1926 said:


> ....If it is existing either surface mount or nothin.


Gee, that's fantastic customer service you guys have. I'd rather surface mount too, but I'd be hard pressed to not at least try a concealed drop if they wanted it and I thought I could.


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## Bkessler (Feb 14, 2007)

MDShunk said:


> Gee, that's fantastic customer service you guys have. I'd rather surface mount too, but I'd be hard pressed to not at least try a concealed drop if they wanted it and I thought I could.


Back in his day your lucky to get it on the wall of your choice. He's 84 right?


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## John Valdes (May 17, 2007)

merlin1926 said:


> That's what we do here,brick layers cut the block and place the box for you.If it is existing either surface mount or nothin.


Then you get nothin and someone comes in and does the job and gets paid. It's not that hard to flush mount a box in a block wall. It's not the easiest thing to do, but it's doable and looks so much better than surface mount.

In South Florida and other areas, block construction is prevalent. You must be able to come in after new construction and do these jobs or you don't get these jobs.


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## Bkessler (Feb 14, 2007)

I can see how cutting a box into block is intimidating if you have never done it or seen it done.. It's easy though.


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## HARRY304E (Sep 15, 2010)

6 shooter said:


> I have to install two circuits in a block wall for a blender and a refrigerator. I would use a 2 gang masonary box in the void of the block. My question is what is the best way to cut out the block. The other is do you use a mortar mix to secure the box in the wall?


Why can't surface mount your circuit and outlets in pipe??


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## 6 shooter (Feb 4, 2008)

MDShunk said:


> Depends on the occupancy type, but either MC or UF. Whatever it takes. You definitely need to be ginger with MC, though. It often takes a guy to feed in and a guy to pull the string with a deft touch. Unless they've poured a bond beam, you shouldn't have a huge problem if you do it with care.


The kitchen is right behind the mechanical room where the panel is only 5 feet away. So I am going to punch a hole in the back side of the block and run mc cable in threw the back and come in the back side of the box. It looks like that is how some of the existing add ons to were done looking over the job.


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## Bkessler (Feb 14, 2007)

HARRY304E said:


> Why can't surface mount your circuit and outlets in pipe??


Because in this situation that's the easy way out and not what the customer wanted.


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## Control Freak (Mar 8, 2008)

give it a good wack with a hammer in the right spot then drill two small holes through the block and run tie wire through the box through the blockand pull the tie wire tight and splice the ends together to hold it in place. fill the void with your choice of mixture..........

when its dry cut the tie wire out.......


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## electric mike (Jun 15, 2009)

always bust the hole up top first and drop some jack chain down the hole to make sure the cores don't have mud or some other obstruction before making your cuts for the box. it's really easy to tell if the chain is falling free down the interior of the wall or getting caught up. then you won't have a hole you can't fish a wire to. for some reason (don't ask me how i know :whistling2 customers don't like that.


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## Marshall175 (May 23, 2009)

merlin1926 said:


> That's what we do here,brick layers cut the block and place the box for you.If it is existing either surface mount or nothin.


wow, what fantastic advice....:thumbsup:


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## Bob Badger (Apr 19, 2009)

amptech said:


> I have always cut the hole using a 4" grinder and chisel, drilling the corners with a 1/4" bit. For securing in the block I use a box with ears and wedge door shims on both sides of the box then caulk the gap around the box with masonry adhesive. If you can cut the hole neat and square, T&B makes battleships with 3-1/2" fingers that work well.


Holy crap, I have never heard of anyone going that route, God bless you I do not have that kind of patience. :thumbsup:


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