# When is MC required?



## Redeyejedi (Dec 13, 2019)

We all know when we need to use MC. However, what codes require its use? Particularly with multi story multi use buildings in Washington state. Any help is greatly appreciated. Thanks


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## Awg-Dawg (Jan 23, 2007)

Redeyejedi said:


> We all know when we need to use MC. However, what codes require its use? Particularly with multi story multi use buildings in Washington state. Any help is greatly appreciated. Thanks


I don’t know of any codes that actually require it.


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## Redeyejedi (Dec 13, 2019)

I feel it will be a fire or building code.


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## Wirenuting (Sep 12, 2010)

Redeyejedi said:


> I feel it will be a fire or building code.


Are you an electrician?


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## Tonedeaf (Nov 26, 2012)

it depends on the type of construction of the building and the Use of that particular space.

generally steel and masonry MC cable
wood construction sometimes you can use Romex


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## Redeyejedi (Dec 13, 2019)

Tonedeaf said:


> it depends on the type of construction of the building and the Use of that particular space.
> 
> generally steel and masonry MC cable
> wood construction sometimes you can use Romex


Generally and sometimes, yes. But what mandates that?


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## Redeyejedi (Dec 13, 2019)

Wirenuting said:


> Are you an electrician?


Yes Sir, I am an electrician and contractor in Washington.


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## Redeyejedi (Dec 13, 2019)

is it possibly due to limitation on NM-B?


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## Bird dog (Oct 27, 2015)

Is this a homework question?


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## CoolWill (Jan 5, 2019)

Most often it is a job spec. Or in existing buildings, you use it because that's what's already there. Or you use it due to the mechanical strength advantage it has over NM in specific environments. The code prohibits NM in some places as well.


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## Redeyejedi (Dec 13, 2019)

NM-B is not permitted in over 3 stories.


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## Bird dog (Oct 27, 2015)

Redeyejedi said:


> NM-B is not permitted in over 3 stories.


Read both code articles & compare them.


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## Redeyejedi (Dec 13, 2019)

im just not finding it in article 334 of 2017.


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## dronai (Apr 11, 2011)

Redeyejedi said:


> NM-B is not permitted in over 3 stories.


This is what I recall in California, but I thought it was for multi family dwellings, over two stories. Not sure though, been awhile


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## Redeyejedi (Dec 13, 2019)

Is it now allowed in wood construction over 3 stories? Ill just call my AHJ in morning. Thanks everyone!


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## Redeyejedi (Dec 13, 2019)

dronai said:


> This is what I recall in California, but I thought it was for multi family dwellings, over two stories. Not sure though, been awhile


Same. Im just not seeing the "story" limitations in 2017 or on Seattle's quick reference.


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## TheLivingBubba (Jul 23, 2015)

dronai said:


> This is what I recall in California, but I thought it was for multi family dwellings, over two stories. Not sure though, been awhile


When I was doing multi family resi, if the type of construction was Type IV romex was okay in common areas (hallways, closets, file rooms.) There was no height limitation to my knowledge because I was working on projects 3-6 stories. If it was Type V construction romex was not okay unless inside an apartment unit.


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## Dennis Alwon (May 9, 2009)

The over 3 stories has been changed many many code cycles ago. Probably at least before 2005 NEC.

NM can be used in 40 story buildings depending on the type of the building


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## Redeyejedi (Dec 13, 2019)

Dennis Alwon said:


> The over 3 stories has been changed many many code cycles ago. Probably at least before 2005 NEC.
> 
> NM can be used in 40 story buildings depending on the type of the building


LMAO i have my 2005 and 2017 in front of me.


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## dronai (Apr 11, 2011)

Dennis Alwon said:


> The over 3 stories has been changed many many code cycles ago. Probably at least before 2005 NEC.
> 
> NM can be used in 40 story buildings depending on the type of the building


The sad part about getting old, 1980's seems like yesterday


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## Wirenuting (Sep 12, 2010)

Redeyejedi said:


> Yes Sir, I am an electrician and contractor in Washington.


Please finish filling out your profile. 

Welcome to ET


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## eddy current (Feb 28, 2009)

Dennis Alwon said:


> The over 3 stories has been changed many many code cycles ago. Probably at least before 2005 NEC.
> 
> NM can be used in 40 story buildings depending on the type of the building


Isn't it only allowed in buildings of combustible construction?


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## splatz (May 23, 2015)

> 334.10 Uses Permitted. Type NM, Type NMC, and Type
> NMS cables shall be permitted to be used in the following:
> (1) One- and two-family dwellings.
> (2) Multifamily dwellings permitted to be of Types III, IV,
> ...


Annex E is a bit of a maze, much better to let the engineer determine type and stamp it on a print or answer an RFI.


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## macmikeman (Jan 23, 2007)

Dennis Alwon said:


> The over 3 stories has been changed many many code cycles ago. Probably at least before 2005 NEC.
> 
> NM can be used in 40 story buildings depending on the type of the building


I don't think there are any 40 story buildings that would be strong enough to support themselves if they are built of a type that allows nm cables. The ones that are all reinforced concrete are not allowed nm cables. Big timber wood frames will collapse after around ten floors. But you can run nm in those ones.


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## B-Nabs (Jun 4, 2014)

macmikeman said:


> I don't think there are any 40 story buildings that would be strong enough to support themselves if they are built of a type that allows nm cables. The ones that are all reinforced concrete are not allowed nm cables. Big timber wood frames will collapse after around ten floors. But you can run nm in those ones.


We have an 18 story one in Vancouver

https://www.google.com/amp/s/global...anada-mass-timber-high-rise-construction/amp/

Sent from my SM-G975W using Tapatalk


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## splatz (May 23, 2015)

B-Nabs said:


> We have an 18 story one in Vancouver
> 
> https://www.google.com/amp/s/global...anada-mass-timber-high-rise-construction/amp/


I read that article, interesting that the gluelams are held together with patriotic and delicious maple syrup. However I am concerned that very patient terrorists are going to fly termites into that building.


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## CTshockhazard (Aug 28, 2009)

eddy current said:


> Isn't it only allowed in buildings of combustible construction?



No, we can install it in buildings that won't burn too. :biggrin:



NM can be used in a multifamily or other structure built out of any material, as long as the building could be built via Types III, IV, and V construction.


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## eddy current (Feb 28, 2009)

CTshockhazard said:


> No, we can install it in buildings that won't burn too. :biggrin:
> 
> 
> 
> NM can be used in a multifamily or other structure built out of any material, as long as the building could be built via Types III, IV, and V construction.


Not sure what those “types” mean. We don’t use those specs in Canada.


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## CTshockhazard (Aug 28, 2009)

eddy current said:


> Not sure what those “types” mean. We don’t use those specs in Canada.



:smile: 


> Construction Types - Definitions
> 
> TYPE I-A--Fire Resistive Non-combustible (Commonly found in high-rise buildings and Group I occupancies). 3 Hr. Exterior Walls* 3 Hr. Structural Frame 2 Hr. Floor/Ceiling Assembly 1 ½ Hr. Roof Protection
> 
> ...


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## manchestersparky (Mar 25, 2007)

The tallest structure NM cable is allowed would be 5 stories , BUT it depends on type of construction, the fire rating and if it is sprinklered.
Annex E in the back of the NEC is a decent reference to start with …...

NM is allowed in types III , IV, & V construction.
Type III max height is 5 stories if one hour rated and sprinklered
Type IV max height is 5 stories if Sprinklered
Type V max height is 4 stories if sprinklered


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## Helmut (May 7, 2014)

Redeyejedi said:


> . But what mandates that?


The code book isn't written that way.


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## bostonPedro (Nov 14, 2017)

Redeyejedi said:


> NM-B is not permitted in over 3 stories.[/QUOTER
> 
> Not true at all.
> You cant leave the floor where the circuit originates when over 3 stories but you can wire resi tower apartments in romex unless you have a local addendum stating otherwise or the building type doesn't allow it


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## manchestersparky (Mar 25, 2007)

Dennis Alwon said:


> The over 3 stories has been changed many many code cycles ago. Probably at least before 2005 NEC.
> 
> NM can be used in 40 story buildings depending on the type of the building


And what building type would a 40 story building be ?? Bet its not a type 3,4, or 5 ……… Just asking ??????


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## Redeyejedi (Dec 13, 2019)

Seems like i went after it backwards, but fully on board now. Truly appreciate the help in understanding the details. Thanks everyone!


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