Using NM Cable (Romex) in Type I and II Construction

[jar546]

NM Cable or 'romex' was developed as a less expensive alternative to BX cable back in the early 1920's. Type NM cable has come a long way since then, including the addition of an equipment grounding conductor starting in the very early 1960's. It is synonymous with one and two family dwellings and of course limited in its use for commercial and industrial applications.

When we read through the code for NM cable we see something interesting, not typical in many other code articles. Let's take a look:

334.10 Uses Permitted. Type NM, Type NMC, and Type NMS
cables shall be permitted to be used in the following, except as
prohibited in 334.12:
(1) One- and two-family dwellings and their attached or
detached garages, and their storage buildings.
(2) Multi-family dwellings permitted to be of Types III, IV,
and V construction.
(3) Other structures permitted to be of Types III, IV, and V
construction. 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.
(4) Cable trays in structures permitted to be Types III, IV, or
V where the cables are identified for the use.
(5) Types I and II construction where installed within raceways
permitted to be installed in Types I and II construction.

When you look at 334.10(5) you immediately think that you can only use NM cable in types I and II construction when installed in raceways, but, that is not the case. Look a little closer at 334.10(2). It may just surprise you.

334.10(2) states "Multi-family dwellings permitted to be of Types III, IV and V construction." What does that mean? The word permitted does not mean that you issued a permit, it means that under the type use, area and height limitations, although the owner chose to build with Type I or II construction, they would have been permitted to build in a lower classification such as Type III, IV or V construction.

I recently looked at a 5 story condo building that was of Type 1 construction but the dwelling units were all wired with NM cable. It was a sprinklered building, of course, but could have easily been built with Type II, IV or V construction. This, of course made the installation of NM cable in the dwelling units perfectly acceptable.

 

[Phil]

I want to make sure I have this right. When NM is installed, the building can no longer be classified/permitted as a Type I. Any type fire-life-safety exceptions or area increase go out the window and the building is no longer type I construction.

 

[ICE]

This might be presumptuous on my part but I think that he means this:
If a building is constructed as types I or II for no particular reason ........and could have been constructed as types III, IV or V....with no change other than the type of construction......then NM is allowed without being in a raceway.

He bumped his head with this one.

 

[jar546]

I want to make sure I have this right. When NM is installed, the building can no longer be classified/permitted as a Type I. Any type fire-life-safety exceptions or area increase go out the window and the building is no longer type I construction.

Part of me agrees with you but nowhere in the description of a Type 1 building does it mention the type of wiring, so no, it is still Type 1 construction. Hmmmm

 

[jar546]

This might be presumptuous on my part but I think that he means this:
If a building is constructed as types I or II for no particular reason ........and could have been constructed as types III, IV or V....with no change other than the type of construction......then NM is allowed without being in a raceway.

He bumped his head with this one.

You are correct. ONLY for multi-family, however.

 

[ICE]

You are correct. ONLY for multi-family, however.

The words are the same for multi-family and other structures.

(2) Multi-family dwellings permitted to be of Types III, IV,
and V construction.
(3) Other structures permitted to be of Types III, IV, and V
construction.

 

[ICE]

If your premise were correct there would be a statement that clarifies that if the Type I and II are required then a raceway is required.

 

[jar546]

If your premise were correct there would be a statement that clarifies that if the Type I and II are required then a raceway is required.

If a building is required to be type 1 or 2 then you have to use raceway

 

[ICE]

If the structure is type I or II NM will be in a raceway. If there was an exception, there would be an exception. Reaching for an exception is not how the NEC is used. The backdoor approach that you have taken can result in issues beyond the present.

Assume that a building that could have been any type of construction is built as a type I for no particular reason. Fast forward to a time when adjacent construction, property line adjustments, additions or whatever cause the Type I to be relied upon.....there is now a violation if the NM is not in a raceway.

 

[jar546]

If the structure is type I or II NM will be in a raceway. If there was an exception, there would be an exception. Reaching for an exception is not how the NEC is used. The backdoor approach that you have taken can result in issues beyond the present.

Assume that a Building that could have been any type of construction is built as a type I for no particular reason. Fast forward to a time when adjacent construction, property line adjustments, additions or whatever cause the Type I to be relied upon.....there is now a violation if the NM is not in a raceway.

That is the way it is interpreted by the IAEI and by the handbook sold by the NFPA and that is what it reads because the verbiage is obvious to clarify the intent. Now, you will never see NM cable exposed anywhere within the construction when the job is done but you can install it in Type I & II buildings if they could have been legally built with Type III, IV & V construction but NOT if they have to be Type I or II. You can always reinvent the code to fit your needs if you want. Your approach is no different than inspectors who require a warning ribbon places 12" above underground service laterals that are in conduit. That section is for direct burial conductors and cables but I see it enforced incorrectly all the time.

 

[jar546]

Here is a recent Type I construction project for R2 units that was approved by the jurisdiction plan reviewers, AHJ, inspectors and me when I performed inspections there.

 

[ICE]

Well then you’re in good company and I’m not. Or could you and your good company be all wet? Ya I think you and your’s need to dry off.

And by the way, I have never required a warning ribbon.....you see we don’t do dumb things like burying cable.

 

[jar546]

Well then you’re in good company and I’m not. Or could you and your good company be all wet? Ya I think you and your’s need to dry off.

And by the way, I have never required a warning ribbon.....you see we don’t do dumb things like burying cable.

You live in your own bubble.

 

[steveray]

IIB and IIIB are pretty much the same H&A wise.....So It could almost always "have been" IIIB here...Even though it is not....