Wiring In Concrete Ceiling & Covering Junction Box

Christo · Jun 6, 2009

Hello
Several questions kindly.
I have a 10" concrete ceiling and I want to route the feed from an existing junction box to a point that is centered in my dining room to hang my fixture.
My plan is to notch out a channel approximately 2 feet from the box to my center point. Any special wire needed.

Also the depth of the box is 4" that needs to be filled in so that I may blend it in with my ceiling covered by joint compound. Perhaps foam for 3" then finish with joint compound feathered in to match the ceiling grade then painted. The whole point is to eliminate the swag of the chain/wire dreaded look. Why electricians put boxes way off center, I never understood.

Any advise would be greatly appreciated.

Bill Arden · Jun 6, 2009

christo said:
My plan is to notch out a channel approximately 2 feet from the box to my center point. Any special wire needed.

If this is a actual pre or post stressed beam concrete ceiling then you can not cut any kind of notches into it.

As for wire, as I understand it you can't just run wire in concrete, it has to be inside of some sort of conduit.

Sponsor · 2022-01-29T12:20:58-0800

Christo · Jun 6, 2009

The concrete was poured in place. The notch should not be any bigger than 1 inch tops 1.5

hj · Jun 6, 2009

ceiling

IF that is a 10" SOLID concrete ceiling the obvious question is how big was the plane they intended to land on it, or were they planning on using it as a driveway for semi trucks? We cannot answer the question because we do not know if there are tension cables or reinforcing metal in that lower 1 1/2" of the ceiling/floor. The physics of stress would make the bottom of the slab the most likely point for any reinforcement because that area is under stress while the upper portion is under compression. I cannot imagine any "patch" that will make a 4" deep box look "invisible".

Jadnashua · Jun 6, 2009

My personal thought is that it is a VERY bad idea to cut a notch in that. You should probably check with a structural engineer first for a blessing or the correct way to do it, if allowed at all. If I had to guess, this is a flat in a high-rise. There's a lot of liability involved here...you don't want to be responsible by doing it wrong or compromising the structure.

Christo · Jun 6, 2009

I should have mentioned I have already done two sections by notching out about a 3/4" channel the length of about 4' to run track lighting without any problems. I did not have to deal with a junction box however. I'm not an engineer but I hardly think that this would undermine the concrete. It is only 3/4 of an inch. I did not have any issues with metal or rebar.
I live in a condominium, hence the poured concrete. Gentlemen, I DO UNDERSTAND ALL OF MY CONSEQUENCES.

My problem is this 4" junction box to conceal. I guessed the slab was 10"
Maybe it is 8" I do know that the junction box is 4"

This run I am trying to accomplish would be only 2' Again does anyone think I could use foam for maybe 2" or so, then use a high strengh quick crete then then finish it with joint compound feathered in to match the ceiling grade then paint it.

If someone has another way, I would very much appreciate any help.

Alectrician · Jun 7, 2009

I wouldn't chop out any concrete, ESPECIALLY for a Jbox.

I'd do it right and furr the ceiling down if I wanted concealed wiring.

Christo · Jun 8, 2009

Thanks for replying 220/221

Could you please explain a little further, as I am not at all clear on what you said.

Thank you.

Geniescience · Jun 8, 2009

ask condo administrators for their understanding of what part of the slab (which is your ceiling, and is the neighbor's floor) you can safely take out. Every person posting above has said it the same way: this is important, very important. The entire building might collapse if it is weakened in specific ways. Unbelievable in your mind? Consult a couple others. Everyone who has posted above has said the same thing. It's now time for you to talk to others in the building.

Cookie · Jun 8, 2009

I know someone who uses fake decorative timbers which spanned their ceilings and from that timber you could maybe put a junction box instead of the concrete ceiling. Just a suggestion. To me that might be better than to maybe compromise the structure of the ceiling.

http://www.fauxwoodbeams.com/about_portfolio.php

Christo · Jun 8, 2009

Thanks for responding Cookie

Good idea on various applications, however that would not fit my decor.

Alectrician · Jun 8, 2009

Install metal hat channel on the concrete ceiling and drywall over that. That gives room for cable/conduit between the ceiling and the drywall.

It's not an inexpensive task but it is the proper way to do it.

Christo · Jun 9, 2009

Hello 20/21

Thanks for the idea, however that would be out of my budget and would force me to scrap the project which I really don't want to do.

Jadnashua · Jun 9, 2009

christo said:
Hello 20/21

Thanks for the idea, however that would be out of my budget and would force me to scrap the project which I really don't want to do.

And repairing the ceiling if it cracks your upstairs neighbor's floor is in the budget? There are right and wrong ways to do things, and I think if you asked a structural engineer, he would blanch at what you are trying to do.

Scuba_Dave · Jun 9, 2009

Notching the cement creates a stress relief point
Any stress (existing or new) can then cause the concrete to fracture
Once it does they will then find out why it fractured
Then you will be on the hook to pay for full repairs

Hopefully it will only fracture & not be a catostrophic failure

To meet code it has to be in conduit
Now you are talking an even deeper notch

Alectrician · Jun 9, 2009

Move your table ?

Christo · Jun 10, 2009

The consensus of opinion seems to say my project is a no no. Not sure what I will do. Maybe consult a structural engineer. Thanks, however for all those taking the time.

FloridaOrange · Jun 10, 2009

christo said:
The consensus of opinion seems to say my project is a no no. Not sure what I will do. Maybe consult a structural engineer. Thanks, however for all those taking the time.

Unless you know one personally it would be cheaper to create a drop ceiling for the lowest j-box you could find. Drywall, some lumber or metal channels, nails, cornerbead and paint. Less than $100 if it's a relatively small area. This project could be accomplished nicely in a day or two at the most.

Gary Swart · Jun 11, 2009

You said in one of your posts that you understood all of the consequences. I've got to say that you don't understand the consequences or you would not be asking the question. First, condos usually mandate that licensed and bonded contractors be used for plumbing and electrical work and that the condo association approve the work before it is done. The contractor is required to pull permits for the job and that means it will have to be inspected. I know that's a lot of bother that you'd like to avoid, but you legally can't. As it has been pointed out, your idea will weaken the structure which will put you on the spot for any and all problems that arise. If and when the condo association finds out what you have done, you will meet with more attorneys than you thought existed. It doesn't matter that doing the job right will cost more money than you want to spend. You either do it right or you don't do it. You are in dangerous water, best heed the warnings.

Wiring In Concrete Ceiling & Covering Junction Box

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