[shauninusa]

Trying to figure out if I can put a 3 or 4 way box for 3 or 4 light switches in a block wall. I'm refitting a house with copper cable versus aluminum in Florida. It means a huge reduction in insurance pricing if changed, so much so ($600+ a year) that it will pay for itself in 2-3 years, so staying with Al cable is not up for debate, note cable has alumiconn blocks but this does not work for insurance company. House is block construction with bats on wall, all drywall is down. All existing boxes are 2 gang but I'd like to make 3 of them 3 or 4 gang boxes. To do this I'd need to cut a bigger hole in the block and that would mean cutting the web (I think that's what it's called) in the center of the block. So my question is can I do that or would it effect the integrity of the block or against code? For the record I can't surface mount, I can't add conduit, and the wall is in place so I can't rebuild and position any of this within the wall. Any guidance would be greatly appreciated.

 

[205490]

What did you spec in your permit?, what does your code spec?

 

[shauninusa]

What did you spec in your permit?, what does your code spec?

The permit was for a renovation and the architects plan shows 3 and 4 way light switches on the wall but does not have any detail on how that will be done. I can ask for a consult with the inspector before I do the work but I was trying to get as much info as I could before I spoke to the inspector. I cant find the code piece in the building code book, do you or anyone know what section that would be in? Happy to read it but that's a lot of reading if you don't know the right section to read.

 

[oldsparky52]

If it were me I would

Talk to the building inspector.

Confirm with the customer that it is okay with them.

In my untrained opinion, I don't believe cutting a portion of the web for a box to fit in there would be a significant structural degradation.

 

[205490]

Yes lots of reading, there is an index

 

[shauninusa]

I think this is the right section of code... Can anyone confirm it is and what they have done to meet this?

"R606.8 Chases

Chases and recesses in masonry walls shall not be deeper than one-third the wall thickness, and the maximum length of a horizontal chase or horizontal projection shall not exceed 4 feet (1219 mm), and shall have not less than 8 inches (203 mm) of masonry in back of the chases and recesses and between adjacent chases or recesses and the jambs of openings. Chases and recesses in masonry walls shall be designed and constructed so as not to reduce the required strength or required fire resistance of the wall and in no case shall a chase or recess be permitted within the required area of a pier. Masonry directly above chases or recesses wider than 12 inches (305 mm) shall be supported on noncombustible lintels."

 

[MikeFL]

You're fine taking out one web of one block in a wall.
Don't even mention it to inspectors.

 

[oldsparky52]

You're fine taking out one web of one block in a wall.
Don't even mention it to inspectors.

And if I'm understanding this correctly, he won't remove the whole web, just a couple/three inches on one side leaving the rest in place to continue supporting the loads.

 

[macmikeman]

Now that we have asked the question , is this going to become the new thing? How long till it starts showing up in the NEC that you cannot cut a web in concrete blocks? It's a conspiracy!!!!!!!

 

[MikeFL]

And if I'm understanding this correctly, he won't remove the whole web, just a couple/three inches on one side leaving the rest in place to continue supporting the loads.

You could remove an entire block and not compromise the wall.
You're going to be fine. Do what you need to do. Make it pretty and nobody will blink an eye.

 

[Almost Retired]

if this is FL or some other hurricane type area, you may find some of the columns in that block wall are poured solid
it would be a bummer to start on that web and hit solid concrete

another option, not necessarily the best would be another 2 gang box above or below the existing ones

 

[shauninusa]

if this is FL or some other hurricane type area, you may find some of the columns in that block wall are poured solid
it would be a bummer to start on that web and hit solid concrete

another option, not necessarily the best would be another 2 gang box above or below the existing ones

Yes all the 3 & 4 I'm adding will be replacing the 2's in place so I can see that the blocks are not solid, or I can push a 1/4" drill into the next web to make sure its empty. but thanks for pointing this out, as you say that would be a bummer to find out.

 

[oldsparky52]

Ugh, check to see if anyone knows if the block walls have that poured insulation in them. That crap is messy and customers don't like losing it.

 

[joe-nwt]

Ugh, check to see if anyone knows if the block walls have that poured insulation in them. That crap is messy and customers don't like losing it.

Some of the old stuff has asbestos in it.

 

[Almost Retired]

Some of the old stuff has asbestos in it.

OH CHIT !!

 

[shauninusa]

Some of the old stuff has asbestos in it.

All the walls, insulation and plaster has been tested all clear of asbestos.

 

[joe-nwt]

All the walls, insulation and plaster has been tested all clear of asbestos.

Did they check for insulation in the block? Only asking because I just recently encountered that very thing.

 

[shauninusa]

Did they check for insulation in the block? Only asking because I just recently encountered that very thing.

No insulation inside wall

 

[MikeFL]

When you're inside that cavity breaking that web out with a hammer, tap the web sideways so you don't blow out the other side of the wall. And only tap as hard as necessary. Breaking out small pieces results in good work. Smashing big chunks will cause more damage than you want to deal with.

You should have some mortar to patch around the box. After you put the mortar on, let it sit for a while, then rub the surface of the mortar with a chunk of the block and you'll have a close enough texture it will match.