NM Uses Permitted

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Hello Forum, I'm an electrician working on a new house for a customer. The new "fad" in our area is homeowners using pole barn steel to finish their garages, used to be garages were sheet rocked, mudded and that's about it. So the pole building steel does provide a very fast way to make a garage look nice, and it can get wet without worrying about the paint.

Now in a normal pole building this would be wired in conduit. The customer is ok with running conduit in their new garage but would really like the wiring in the walls for a cleaner look. On a prior job with an inspector I was told romex could not be installed behind steel because its not fire rated. We are told there is a fire rated sheet steel available we're looking at. But I'm just curious if someone could clear up NEC 2020 code 334.10 (3) for me, as to what defines a "thermal barrier" and what the general purpose this paragraph is getting at? I'm not seeing anywhere else in the code under uses permitted or uses not permitted for NM cable that defines what coverings aren't allowed.

Thanks in advance.
 
I don't think Iowa is using the 2020 yet.

Roger
 
334.10 (3) doesn't apply if this is " One- and two-family dwellings and their attached or detached garages, and their storage buildings. " Other means things other than in (1) and (2).

By the way, that section is unchanged since at least 2011.
 
In a garage NM can be exposed in stud bays.
Its not a dwelling.
Huh? It is presumably a one and two family dwelling and it's attached or detached garage, which allows you (at least as far as the NEC is concerned) which allows it to be used. Garages that are not associated with such dwellings and are constructed of Type II, IV, or V require protection.
 
I'm not an inspector, but I looking at 334.10, I would say you should be okay if the sheet metal meets the fire rating described. "at least a 15 minute finish rating". If you the NM is exposed and the sheet metal is used as the exterior only, I would recommend using conduit just for the sake of protection.
 
I'm not an inspector, but I looking at 334.10, I would say you should be okay if the sheet metal meets the fire rating described. "at least a 15 minute finish rating". If you the NM is exposed and the sheet metal is used as the exterior only, I would recommend using conduit just for the sake of protection.
I doubt that any material that is thermally conductive would meet the requirements for a finish rating. That rating is intended to provide a period of time before the combustible material behind it can reach its auto-ignition temperature.

That being said, since the garage in question is associated with a dwelling unit, 334.10(3) does not apply. There are no special rules triggered by the use of the steel interior wall covering.
 
I doubt that any material that is thermally conductive would meet the requirements for a finish rating. That rating is intended to provide a period of time before the combustible material behind it can reach its auto-ignition temperature.

That being said, since the garage in question is associated with a dwelling unit, 334.10(3) does not apply. There are no special rules triggered by the use of the steel interior wall covering.

Thanks for the input Don that's what I was after is the science behind it. And thanks to everyone else, very much appreciated.
 
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