NM covered one side

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augie47

augie47

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State Electrical Inspector (Retired)
In regard to 334.10(3), this may be answered by Appendix E, but, Appendix E and I have not come to friendly terms as of yet, so allow me to post a couple of scenarios.

Condition 1: Building is typical commercial "red iron" structure. Exterior is insulated metal walls. Inside is metal studs with walls and ceiling covered one side with sheet-rock.
Is Romex allowed ? (Code says "cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies. "

Condition 2: Same as one except sheet-rock covered room(s) are only a potion of the building (such as small offices in an open warehouse)
Those walls exposed to the warehouse are coved both sides but those exposed to the exterior walls are not.

I have been taught one of the reasons for the barrier was containing
fumes in the event of a fire. In condition 2, any fumes would be free to fill the warehouse.
In Condition, the entire building is covered one side. Fumes would only
escape to above a sheet rock ceiling.
Only one side is covered so cable is not necessarily "within"
 
Not sure I'm seeing the difference between this and an unfinished attic in most any house. And it seems less likely people would be sleeping in a warehouse. I guess I'm not considering the code... but what would seem to me to be common sense.
 
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Nor do people sleep above drop or suspended ceilings in other than dwellings but this is not allowed either 334.12 (A) (2)
 
The basic question falls back to Romex being installed per 334.10(3).
Is it Code compliant if the Romex is behind a 15 min rated wall cover on one side but exposed and non-accessible on the other or do both sides have to have 15 min cover ?










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The buildings you describe would be Type I or II and would not allow NM cable unless in conduit. The reasons for limiting NM cables are not only fumes but the combustability of the cables. Type I and II buildings are designs that limit the combustable elements in and protect key structural elements of a building.
 
Dennis Alwon said:
Gus can you give an example of exposed and non accessible. I am also having trouble with this concept.
Click to expand...

I attempted to in Post #1 ;)
Prefab metal building. Exterior walls sheet metal with insulation.
General Contractor constructs some "offices" in the prefab building by
building walls (either wood or steel studs) and sheet rocking the side(s)
accessible to the occupants but leaves the open studs where the back up to the prefab building exterior walls.
(say office is built in a corner and two walls are only inches from the main structure outside wall so that the Romex is out of sight/reach but open to air)

RICK NAPIER said:
The buildings you describe would be Type I or II and would not allow NM cable unless in conduit. The reasons for limiting NM cables are not only fumes but the combustability of the cables. Type I and II buildings are designs that limit the combustable elements in and protect key structural elements of a building.
Click to expand...
Rick, are you saying the interior buildings are considered Type I or II whereas the basic structure (pre fab) is Class III, IV or V ??
 
I did not realize from your first post that these structures were part of an existing structure, if they are part of an existing structure that is type III, IV or V then NM cable could be used but needs the 15 minute rated cover even if it is inaccessible.
 
RICK NAPIER said:
I did not realize from your first post that these structures were part of an existing structure, if they are part of an existing structure that is type III, IV or V then NM cable could be used but needs the 15 minute rated cover even if it is inaccessible.
Click to expand...

The question is whether it needs sheetrock on the backside of the 2x4 wall that butts up to the outside wall. Is that correct Gus.

IMO, I don't think it would.
 
Dennis Alwon said:
The question is whether it needs sheetrock on the backside of the 2x4 wall that butts up to the outside wall. Is that correct Gus.

IMO, I don't think it would.
Click to expand...

That is correct
(sometimes getting info from me is akin to pulling teeth ;))
 
This is an interesting subject. I recently had a NCDOI repsentative tell our local inspector, based on a local complaint, that is was acceptable to have exposed nm cable in a mechanical space, located on the second level of an business occupancy, served by a permanent door. The questions were about this issue, and grouping the service disconnects in a two story multiple tenant space, one upstairs and one downstaris, and the exposed nm cables. The response was that since it was intended to be rented to another "occupant" upstairs, that the two services were acceptable. I can't seem to get these explanations, other that someone is covering someone elses "you-know-what" - I sometimes see why there is such inconsistency between counties in NC. I agree with the folks here, must have 15 min rating between occupants and nm cable. (sorry about venting)
 
so the contractor is supposed to build an 8 foot high office in a portion of a warehouse with 15 foot walls. Then to save having to drill holes, he decides to set the wall studding out from the exterior warehouse walls a half an inch... then it occurs to him that if he sets it out an inch he could put the water pipes back there too... then he realizes he needs a drain so he sets it out 2" .... then he remembers one of the drains is a 3" drain.

Is there a point at which 344 is violated? Where is it?
 
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