Electrical Boxes in block walls

[steve66]

I am designing a project where we will have a lot of block walls. There will be a lot of outlets, switches, etc. that are flush mounted. Some of the areas will be hose down.

I'm not sure what type of boxes to specify. I am also worried about how the contractor will fasten the boxes. I don't want them falling out in a few years.

I am thinking of using metal boxes with a baked on epoxy paint in the hose-down areas. Boxes like Pass & Seymour WPB23.
P & S catalog

But I don't know how these would be mounted in a block wall.

In other areas, I'm not sure if I should stick with the weatherproof boxes, or allow your typical steel boxes, or if regular plastic boxes can be used.

Thanks in advance:
Steve

 

[petersonra]

Re: Electrical Boxes in block walls

I have seen boxes in such a situation actually grouted in place. Looks like it is part of the wall.

 

[tkb]

Re: Electrical Boxes in block walls

The aluminum boxes will turn to white powder in a few years. I have seen this done. Not a good idea. IMHO

I would use a deep 4" sq with a 2" tile ring.

Make sure that mason fills the space in the block where the box is, and fill around the tile ring. Then use a regular weatherproof cover.

If the mason works with the electrician, It can look good and be watertite also.

 

[jimwalker]

Re: Electrical Boxes in block walls

Depends on what your running,if romex i would use plastic cut in boxes.

 

[steve66]

Re: Electrical Boxes in block walls

Posted by TBK:

The aluminum boxes will turn to white powder in a few years.

Do you mean the weatherproof ones with the baked on paint? They don't let us out much.

Steve

 

[steve66]

Re: Electrical Boxes in block walls

Jimwalker:

Again, I'm not that familiar with contractor lingo, so can you guys please talk slower for me

Is a plastic cut in box something like these P&S Slater boxes (without the nails):

Slater Boxes


No romex, but I'll let them use almost anything else. EMT, PVC, LFMC, or even flexible nonmetallic conduit (I think its called smurf tube??). I am trying to make it easy for the electricians, yet get an installation that will last.


Thanks again:
Steve

 

[JJWalecka]

Re: Electrical Boxes in block walls

Steve

` I have always used 4" Square by 2 1/8 deep box with an 1/8 or 1/4 plaster ring in block walls. As TKB stated if you work with the mason and mortar is installed around the box and plaster ring it will hold well. I like to put duct tape around the box and fitting to ensure no concrete gets in and remember the green ground screw and conductor with at least six inches from the back of the box before you install the box in the in the masonry wall. Generally I stub up with 18" cuts of E.M.T to a above the suspended ceiling. Where I then 90 degree into another 4" Square deep surface mounted where another raceway can feed the device. Watch the mason "accidentally" they can move the pipe around and the next thing you know the mortar is dry with the plaster ring not flush with the block. Hope this helped if at all.

Justin

 

[roger]

Re: Electrical Boxes in block walls

Steve as stated earlier a 4" sq (1900 box) box with a 1.5" plaster ring works as well as a standard masonry (tile) box.

4" square box

4" square 1.5" deep plaster ring

Masonry box (gangable)

I have been installing these type boxes in finshed block jobs (kitchens, schools, industrial, etc...) for 30 years.

Roger

 

[sandsnow]

Re: Electrical Boxes in block walls

Just like the old saying water and electricity don't mix, water and metal don't mix where the moisture can accumulate on or in the metal enclosure. I see it all the time on commercial remodels.

Take a look at the non-metallic boxes they make for ENT. Here's a link to Carlon's website: CARLON

 

[JJWalecka]

Re: Electrical Boxes in block walls

Steve typing mistake 1.5" is the correct choice 1/8 and 1/4 plaster rings are incorrect per Article 314.20 which states In wall or ceilings with surface of concrete, tile, gypsum, plaster or other noncombustable material, boxes shall be installed so that the front edge will not be set back of the finished surface more than 6 mm (1/4)
in)
In walls and ceilings constructed of wood or other combustible surface material, boxes shall be flush with the finished surface or project therefrom


Justin

 

[paul]

Re: Electrical Boxes in block walls

I prefer the metal, gangable mason boxes shown. Lord knows that the blockies aren't the most gentle guys on the job. I think they're a half notch about the steel guys on the gentle scale, so the tougher the better. Then go ahead with PVC, because of you have a ton of blockies going full tilt boogie, then you're gonna want to be throwing those 4' sections of raceway up real quicklike when you have 5+ blockies all screaming "SPARKY" at the same time.

I say let the contracter choose what boxes they're comfortable with.

Goodluck

 

[davedottcom]

Re: Electrical Boxes in block walls

The Masonry boxes work great. Although I never used the gangable ones. You'll have to stand there and add 24" pipe stubs as the brickies are building the walls. I suggest having A LOT of them precut and ready to go, 90's too, also precut so they stick out where you want them to. The boxes wont move if the masons throw enough mud around them. Part of your job is to make sure They do theirs!

Dave

 

[paul]

Re: Electrical Boxes in block walls

Originally posted by davedottcom:
Part of your job is to make sure They do theirs!

Dave

One job I was working on, we bought the blockies a case of beer on Friday early in the job. Made things run ALOT smoother for us the rest of the time they were building the walls.

 

[allenwayne]

Re: Electrical Boxes in block walls

We do 6 course lifts,The block masons will lift that far,I like using deep P rings to flush out to block.When it gets boring waiting for that call a case of beer does help to insure that the block guys won`t go past you

 

[davedottcom]

Re: Electrical Boxes in block walls

I was also going to suggest that making friends Quick with the brickies will make life much easier!!!
The last job I did like this was a big YMCA, I put on 48" stubs and the masons just looked at me like "what the #@$% " Their blocks weighed 18 lbs!!! Ooops!
I cut the stubs in half to keep them happy. Also bough a few rounds of coffee (Winter time in Pa!) Kept them happy,Job went great.

Dave

 

[steve66]

Re: Electrical Boxes in block walls

Thanks for all the help. And double thanks to Roger for his pictures.

Justin: I'm not sure, but I think the intent of the article is to keep the box enclosed. I don't see anything wrong with recessing the box, and using a plaster ring to flush mount the device. Maybe the plaster ring counts as part of the box.

Steve

 

[electricmanscott]

Re: Electrical Boxes in block walls

This isn't what you are looking for but for future reference.
http://www.aifittings.com/whnew68.htm

 

[JJWalecka]

Re: Electrical Boxes in block walls

Steve,

I wrote 1/8 inch or 1/4 inch plaster rings, I feel that they would be too recessed in the block, since the block is around 1 inch thick (I believe) and the yoke of the device wouldn't be within the required 1/4 inch of the plaster ring. Per article 314.20. Maybe I'm wrong. I learn everyday. My interpretation of the Code is that the device yoke should be as close, if not making mechanical contact with the box or plaster ring. To ensure a proper ground and to be electrically safe from combustible materials. Good luck.

Justin