# Can I use NMB for wiring through steel studs?



## Drsparky14 (Oct 22, 2016)

I have a customer who wants me to wire his house, he has framed the entire thing out of metal studs. It looks like a commercial building lol. 

My question is, can I use NMB and grommets to wire the house with? Or do I have to use MC cable?

I ask because on all the commercial jobs I’ve done with metal studs it was always spec’ed for MC or AC wire. 


Thank you!


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## macmikeman (Jan 23, 2007)

It is all in your code book. Residential buildings are an acceptable place for NM run in steel studs as long as plastic bushings are installed properly , and the building type meets the requirements set forth in the code book for where NM cable can be installed. If this is a two story metal framed house, then you bet your ass you can do it, unless there are local amendments , and there is no spec prohibition for that particular project against NM cables being used. I've roped a dozen metal stud whole houses at least. I like the way the floor joists have prepared holes for my wires, no drilling the joist required. Top plates are a different story but check out the knock out drill bits in my added picture.











These are the bomb. Pump the trigger on your impact gun, don't hold it down continually. Pump action. Works fast and good. Then stick the bushing in the hole and pull your wire thru. Fast.


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## Dennis Alwon (May 9, 2009)

I agree it is not an issue to use nm cable


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## splatz (May 23, 2015)

Drsparky14 said:


> I ask because on all the commercial jobs I’ve done with metal studs it was always spec’ed for MC or AC wire.


Of course with steel studs, you'll need the grommets with NM. I am not sure if it's a code requirement but I wouldn't mess around with anything but the two-piece grommets that are made for the purpose, once you snap them together they stay in place. 

If the spec's don't rule out NM, a lot of commercial buildings are a building type that NEC would allow NM. But, that can lead to a battle with the inspector, and to win that one you you'll have to prove the building type, and if you don't have that on the prints or otherwise stamped by architect / engineer, good luck. 

I had a friend lose this battle once and it cost him a pile of money. And that was a stick built building, wood framed, he just lost the argument with the inspector about the building type. The construction manager / GC was really not on the ball, but it was him that wound up taking the bath.


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## Cow (Jan 16, 2008)

Just because you can, why would you want too?


I'd use MC all day long and not worry about one of the grommets falling out, like they always do and chafing/cutting through the jacket on the NM.


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## MechanicalDVR (Dec 29, 2007)

+1 for Cow's comment.


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## macmikeman (Jan 23, 2007)

MechanicalDVR said:


> +1 for Cow's comment.


-1 for Mech's comment. There is steel homes by the ten thousands in this state and in California by the millions. Wired with Romex. Safely. 



I can remember a time when although mc was manufactured and sold everywhere else the Honolulu inspectors were not allowing it, since they thought it was BX , and you couldn't convince them it wasn't BX it was something new. 
They had stuck brains for a number of years. Don't have a stuck brains Cow and Mech, this is a very common wiring method.


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## Signal1 (Feb 10, 2016)

I've pulled thousands and thousands of feet of NM through metal studs with no problems. I was just one apprentice of a crew of 20. We had the 1000 foot reels craned up by the pallet. 
During the condo-mania years here in the late 80's there were 10-12 story 100+ unit buildings going up everywhere they could fit them. All metal studs, all NM.

I don't think I saw a wood stud my first four years in the trade. Now everything is wood again. 

The only issue back then was it couldn't pass though floors.

With the right grommets that snap in tight, and the caddy CJ clips for support, it's fast easy and safe.


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## MechanicalDVR (Dec 29, 2007)

macmikeman said:


> -1 for Mech's comment. There is steel homes by the ten thousands in this state and in California by the millions. Wired with Romex. Safely.
> 
> 
> 
> ...


I'd rather just pull mc than install bushings and then pull cable and go back and reinstall bushings that popped out during the pulling of cables...

Rinse-wash-repeat!


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## macmikeman (Jan 23, 2007)

MechanicalDVR said:


> I'd rather just pull mc than install bushings and then pull cable and go back and reinstall bushings that popped out during the pulling of cables...
> 
> Rinse-wash-repeat!


Why can't you just admit you never worked in a situation like that and leave it to people who do that style of wiring to comment on it?

I hereby condemn all POE T-BAR wiring scheme's regardless of how well they work, because I have never touched a single system like that! I must be crappy since I have no experience in it..............


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## macmikeman (Jan 23, 2007)

Quoted from HackWorks- You weren’t trying to educate yourself, you were trying to criticize other people’s work and tell them how it was wrong, when it was actually right. You have a very bad attitude, if you change that everything will be just fine.

The people on this form will be happy to educate you, but you have to be willing to receive it.

When you apologize to the forum we can get past this.


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## MechanicalDVR (Dec 29, 2007)

macmikeman said:


> Quoted from HackWorks- You weren’t trying to educate yourself, you were trying to criticize other people’s work and tell them how it was wrong, when it was actually right. You have a very bad attitude, if you change that everything will be just fine.
> 
> The people on this form will be happy to educate you, but you have to be willing to receive it.
> 
> When you apologize to the forum we can get past this.


LOL!

Maybe I just completely hate romex and it's crappy thin plastic jacket!


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## Bird dog (Oct 27, 2015)

Interesting comments. Does seem like romex in metal studs is an option.


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## cabletie (Feb 12, 2011)

So if you go with Romex, what type of box do you prefer? 

I know they just put up metal framed condos by me and used Romex. I don't know what type of boxes they used.


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## Wiresmith (Feb 9, 2013)

Your allowed to unless your local codes forbid it. But i am in the anti-nm camp with some of the other guys, i wouldn't want to use NM even with wood studs. Not that your playing with fire using it, just when i look at the cost/benefit ratio i think NM is the clear loser. It just doesn't make sense to me.


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## cwsims84 (Jan 21, 2012)

Cow said:


> Just because you can, why would you want too?
> 
> 
> I'd use MC all day long and not worry about one of the grommets falling out, like they always do and chafing/cutting through the jacket on the NM.


If done right... what’s the cost of a 250ft roll of 12/2 or 12/3 NM compared to the like in MC.. my cost on 12/2NM 250ft— $68.75, 12/2 MC 250ft — $144.50... that’s just my cost.. at more than double the cost.. I’ll take the NM.


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## cabletie (Feb 12, 2011)

Don't forget the price of grommets and installation

250' x12 = 3,000"
3,000 / 16 = 187 grommets per 250' @ 16" on center. 

So rounding it down to 100 per 250' adds another $77.00

I'm always told material is nothing, manhours is the killer. It's probably closer to a wash. Still leaning towards Romex though.


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## splatz (May 23, 2015)

cabletie said:


> So if you go with Romex, what type of box do you prefer?
> 
> I know they just put up metal framed condos by me and used Romex. I don't know what type of boxes they used.


I don't think it would change the boxes, or the collection of Erico-Caddy goodies that go with...


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## splatz (May 23, 2015)

cabletie said:


> Don't forget the price of grommets and installation
> 
> 250' x12 = 3,000"
> 3,000 / 16 = 187 grommets per 250' @ 16" on center.
> ...


It's actually about $30 for a bag of 100 of the Arlington bushings (SB130). Taking it a step further, the fittings cost more with MC. So materials cost, NM is ahdead. 

Labor wise, again NM is ahead, if all goes well. You nick a few, the NM lead could go right down the tube. And of course you can never save enough to make it pay if the inspector makes you rip it all out. 

BTW - to those who have the grommets fall out - I haven't had that issue. 
I haven't used them that much, and when I have I've used the Arlington two-piece rather than the Caddy or Greenlee. I do try to install them in the direction that I'll be pulling - that way friction isn't trying to push them back out.


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## 3DDesign (Oct 25, 2014)

Why not ask the inspector what he wants. One, 2 minute phone call solves this.
I agree NM should pass.


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## 99cents (Aug 20, 2012)

I usually just screw a piece of 2 X4 over the existing hole in the stud and drill a hole through it.


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## cwsims84 (Jan 21, 2012)

3DDesign said:


> Why not ask the inspector what he wants. One, 2 minute phone call solves this.
> I agree NM should pass.


Our inspectors will come out and give you a consult.. if you failed for something like this and you didn’t get a consult from them, you probably deserve the costs to rip it out... I always get one when I want to run a fine line on the code


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## macmikeman (Jan 23, 2007)

cwsims84 said:


> Our inspectors will come out and give you a consult.. if you failed for something like this and you didn’t get a consult from them, you probably deserve the costs to rip it out... I always get one when I want to run a fine line on the code



This is not a fine line on the code. It's a very commonly used wiring method. It's only the janitor boys at this forum who are never exposed to running wiring in dwellings in their entire career who have been giving objections. The code allows nm in single family and multifamily dwellings. Some types of buildings do not allow nm cable. That is the fine line. A high rise - you need mc or emt , no nm . And as far as Chicago goes, well........ they differnt in Chicago. Everything coming from Chicago is differnt.


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## macmikeman (Jan 23, 2007)

99cents said:


> I usually just screw a piece of 2 X4 over the existing hole in the stud and drill a hole through it.


Insanity, and in some cases , violation of fire codes using wood inside walls.


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## splatz (May 23, 2015)

99cents said:


> I usually just screw a piece of 2 X4 over the existing hole in the stud and drill a hole through it.


 That is creative and a good one to remember if you don't have a grommet with you. 



The bushings however are cheaper and you can fit a lot more in your pouch and they cost $0.30 so I don't think I'd ever plan to use wood, only improvise.


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## L J (Sep 28, 2018)

When I was just getting introduced to the trade, there were days when the only things my hands touched were attachment 1 and attachment 2 of this post. 

Needless to say, I can confirm that NM-B through metal studs is common practice in some areas.


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## Jlarson (Jun 28, 2009)

Big box of Arlington bushings, black buttons, some H23's and CJ6's and deep 1900's.


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