NM Use in Metal Building

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absolutesantaja

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Waynesboro, Tenneesee
First of all I'm primary residential but me and another LLE are volunteering some time to wire a small steel building for our local church. The inside has wooden frame installed in front of the metal for sheetrock and drop ceiling to attach to. Now I know that NM is now allowed above the drop ceiling and we will be running MC as much as I dislike dealing with it but what is easier for the walls? Go ahead and run MC for everything or run NM and put metal junction boxes above the fake walls and swap over. 2008 Code references would be appreciated and yes I have searched the forum and have only found references for junction boxes above the drop ceiling and NM not being allowed in non dwellings.

Thanks and sorry for confusing everyone.
 
If you will combine the information from Annex E of your NEC with chapter 6 of the IBC, it will give you the where and where-nots of NM use. You might also check your local requirements, as there may be some differences.
 
You might take into consideration the engineered occupancy load* of the building as Art 518.4 may come into play.

* That number is derived by a standard based on use/type seating/etc and not just a "guesstimate"

(I assume your statement "Now I know that NM is now allowed above the drop ceiling" is a typo) 334.12
 
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Personally I like to pick one wiring method and stick with it, unless of course I have to change. Less material to have to worry about in my mind. So MC would be my choice in this instance and I'm not a huge MC fan either. I prefer flex for commercial work.

I'm assuming that the metal building is simply for storage or a work shop or such?
 
I can't remeber when and why it was, but I do recall where an exact situation of wood againest metal bldg. frame, came into play. I beleive that the wall down the building frame changed the listing of the wall since it was not a closed or complete assembly on the back side of wall down the structure, there was no gypsum on the metal side of the wall. There was a minimum air gap off of the structure.

I don't remember the cure or fix either! I do remember thinking of the pleasure of learning of the yahoo moment done by others though. :grin:

Bldg official didn't like it due to class of structure/usuage, something...
 
MC for everything. Absolutely "no" on transitioning from mc to romex just to run down the walls. No code reason. The time you spend making up extra boxes would be worth more than the material. Plus if you have other volunteers then you want to keep it simple.

Why do you prefer flex to mc Cowboy? Seams like way more work unless you are pulling multiple circuits at once. Even still with 12-4, 12-3 etc it seams like mc is the better method. I like flex for # 8 and over, shorts whips, and multiple conductors.
 
sd4524 said:
MC for everything. Absolutely "no" on transitioning from mc to romex just to run down the walls. No code reason. The time you spend making up extra boxes would be worth more than the material. Plus if you have other volunteers then you want to keep it simple.

Why do you prefer flex to mc Cowboy? Seams like way more work unless you are pulling multiple circuits at once. Even still with 12-4, 12-3 etc it seams like mc is the better method. I like flex for # 8 and over, shorts whips, and multiple conductors.
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I used to do a lot of remodel work, just easier if you want to expand or change something. Instead of opening a wall all the way back to the panel just to add a circuit, you can just pull it through. I've used MC and I've pulled miles of NMC, like I said just personal preferance.
 
Sorry for the delay in replying, I've realized after reading a lot of responses that I really didn't give enough information. My statement that NM is not allowed above drop ceilings was not a typo, it is only allowed above a drop ceiling in dwellings of 2 family's or less per 334.12 A(2) since this is not a dwelling then it would not be allowed.

Since our church has never had any where near 100 people nor would 1200 square feet hold that many with tables and chairs i don't believe that Article 518 applies either. I've looked up several formulas that indicate occupany is roughly 20'-36'^2 per person.

We are outside of the city limits and there isn't a building code that needs to be met.

As to why I wanted to only run MC in the drop ceiling, I'm only running 11 florescent light fixtures and smoke detectors that's barely 150' of cable, everything else is run within the wood frame walls.

The area is to be used for serving meals and will have two bathrooms with a small kitchen. Very few circuits are needed aside from the lighting and the kitchen area so we are trying to keep the expense to a minimum. I will be talking with the inspector tomorrow to see what he prefers for a transition from NM to MC above the drop ceiling.

Thanks to all of the replies you've helped me answer several of my questions.

Shawn
 
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