300.4 and protecting cables

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Twoskinsoneman

Twoskinsoneman

Senior Member
Location
West Virginia, USA NEC: 2020
Occupation
Facility Senior Electrician
Was browsing 300.4 and had a question.
Is there any prohibition to installing NM cables across joists (perpendicular to the joists) in an unfinished basement. I see rules on distance from the edge IF routed through holes in the joist.
In the remodeling of a basement in which cables WERE installed in such a manner, obviously putting wall board on the ceiling would smash the cables. But if a drop ceiling were installed could the installation remain?

Thanks
 
Twoskinsoneman said:
Was browsing 300.4 and had a question.
Is there any prohibition to installing NM cables across joists (perpendicular to the joists) in an unfinished basement. I see rules on distance from the edge IF routed through holes in the joist.
In the remodeling of a basement in which cables WERE installed in such a manner, obviously putting wall board on the ceiling would smash the cables. But if a drop ceiling were installed could the installation remain?

Thanks
Click to expand...

IMO yes. NM cables are stapled to the joists all of the time when a ceiling is installed below them.
 
And, adding on to Infinity's comment, if the new remodel has rock replacing the dropped ceiling, then either nail plating or furring strips would permit the NM to remain (IMO, nail plating, in this situation, necessitates the slight notching of the joists for the NM to lay in.)
 
al hildenbrand said:
And, adding on to Infinity's comment, if the new remodel has rock replacing the dropped ceiling, then either nail plating or furring strips would permit the NM to remain (IMO, nail plating, in this situation, necessitates the slight notching of the joists for the NM to lay in.)
Click to expand...

Also to add, if you use furring strips you must keep the cable 1-1/4" from edge of the furring strip.

I don't quite understand this 1-1/4" rule, I could see not laying it up against the strip. But if you are nailing or installing screws into the strip what is the chance that you are going to hit a cable if it's not exactly 1-1/4" from the strip? You should mark where the strips are anyway, to know where to nail/screw.
 
Interesting. If I read the question correctly and the NM (smaller than #6) was fastened to the bottom of the ceiling joist on an unfinished basement it was a violation of 334.15(C). Locally, if you finish the basement (wiring as habitable space), then a drop ceiling would being the joist NM into compliance.
 
augie47 said:
Interesting. If I read the question correctly and the NM (smaller than #6) was fastened to the bottom of the ceiling joist on an unfinished basement it was a violation of 334.15(C). Locally, if you finish the basement (wiring as habitable space), then a drop ceiling would being the joist NM into compliance.
Click to expand...

Yeah your right.... interesting. What do you think is the reasoning behind it being ok for #8 and #6 NM? Someone may just decided to install wall board right over the small stuff smashing against the joists?
 
Twoskinsoneman said:
Yeah your right.... interesting. What do you think is the reasoning behind it being ok for #8 and #6 NM? Someone may just decided to install wall board right over the small stuff smashing against the joists?
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The bigger cables are strong enough to use as hangers ;)
 
Little Bill said:
But if you are nailing or installing screws into the strip what is the chance that you are going to hit a cable if it's not exactly 1-1/4" from the strip? You should mark where the strips are anyway, to know where to nail/screw.
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Agreed highly unlikely, but strange things happen. In the following you can see those crafty rockers used my MC to make a joint.:mad:

Joint.jpg
 
300.4 and protecting cables

I think your breaking the Code, I know around here they don't install shallow slates of wood for gypsum board installs. This is the main reason for me replying. I read about this type of install about once or twice a year. This type of install just doesn't happen around here. The slat wood framing is a hangover of stucco drywall installs where the materail needed the addition square footage support not offered with sixteen inch frame spacing. They might need to do slat installs for leveling or other requirements but you can't install and assume they will slat the ceiling. Thus 300.4.

(While I read this article quickie 300.4) I just don't see that this is an exception to your install either, it you take a minute and read it all I don't think you can just have it there in this wood cavity.

Frankly if your still going to do this one needs to do some coordination with the other trades involved. What your dealing with is a concealed install.

Cable is not mentioned in the definitions in 100 so here we go what is a CABLE ?

But, it's all over the Index the first definination is up in 800.2. Yes your type of material is listed, used and given.

Good Luck.
 
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augie47 said:
Interesting. If I read the question correctly and the NM (smaller than #6) was fastened to the bottom of the ceiling joist on an unfinished basement it was a violation of 334.15(C). Locally, if you finish the basement (wiring as habitable space), then a drop ceiling would being the joist NM into compliance.
Click to expand...

I JUST had to look that up and you are correct.

I have to get some #12 Romex from one side of an air return to the other. I can sleeve it and go through the joists, but in order to go under the joist I must have a running board.
 
Twoskinsoneman said:
Actually with the smaller stuff being supported by the hole through the joist, purely from a technical stand point they may have the higher load rating. :grin:
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I don't think it's got anything to do with load rating and everything to do with installation. Just think what a pain it would be to have to pull anything bigger than #6 NMS through bored holes. The more you have to struggle, the greater the chance of damaging the cable. If you made the holes big enough for an easy pull, they would have to be huge.
 
K8MHZ said:
I don't think it's got anything to do with load rating and everything to do with installation. Just think what a pain it would be to have to pull anything bigger than #6 NMS through bored holes. The more you have to struggle, the greater the chance of damaging the cable. If you made the holes big enough for an easy pull, they would have to be huge.
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Mine was a jest :roll:

But just because it is easier to pull smaller cables through a bored hole does not explain why the rule exist. I agree with Don that the rule does not accomplish anything... but make installs harder.
 
Twoskinsoneman said:
Was browsing 300.4 and had a question.
Is there any prohibition to installing NM cables across joists (perpendicular to the joists) in an unfinished basement. I see rules on distance from the edge IF routed through holes in the joist.
In the remodeling of a basement in which cables WERE installed in such a manner, obviously putting wall board on the ceiling would smash the cables. But if a drop ceiling were installed could the installation remain?

Thanks
Click to expand...
Augie47 is right on.
334.15,C says no in unfinished basements.
Two #6's or 3 #8's and larger cables can. Smaller cables shall be run by running boards, or in bored holes.
 
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