NM CABLE IN ATTICS???

[jkl]

The AHJ is requiring that we secure our NM Cable at everyother truss (within 4.5') when we run perpendicular in the attic on trusses.

334.30(A) addresses that "runs through holes and notches" are considered supported as long as the support (studs) do not exceed 4.5' appart and the cable is secured within 12" of boxes.

The question: Is the AHJ correct?

(p.s.: we are in compliance with 334.23)

 

[bphgravity]

Re: NM CABLE IN ATTICS???

Is there a possibility that there could be damage concerns for the NM cable or maybe some obsure local code? What was the inspectors reasoning, did he give an explanation? Did you ask for one?

 

[jkl]

Re: NM CABLE IN ATTICS???

Thanks for the quick reply.

There is no special damage concern that I am aware of, this is your standard everyday residential home.

I have no local code issues as I am in Florida.

I don't no what the inspectors reasoning was, apparently my electricians have been doing this for sometime now and I was unaware.

 

[svaurez]

Re: NM CABLE IN ATTICS???

If your running the cable "ON" the trusses you have to strap it every 4.5 feet.If your running it "IN" the trusses you can use 334.30(A)

[ March 07, 2003, 11:28 AM: Message edited by: svaurez ]

 

[jkl]

Re: NM CABLE IN ATTICS???

I am running the NM on top of the truss. I'm just not sure what the difference is in being supported "in" a hole or notch as apposed to "on" a truss.
:roll:

 

[curt swartz]

Re: NM CABLE IN ATTICS???

A hole or notch will prevent horizontal movement of the cable.
There is a note in the handbook that says: Draping the cable over air ducts, timbers, joists, pipes and ceiling grid members is not permitted.

 

[bryonb]

Re: NM CABLE IN ATTICS???

334.30(A) says that the cable must be installed in accordance with 300.4.
300.4(A)(1) & (2) refer to "Bored Holes" and "Notches in Wood". I think the intent of 334.30(A) is refering to such and not layed inbetween the supporting members of a truss.

 

[jxofaltrds]

Re: NM CABLE IN ATTICS???

JKL

I would agree with him. Using your view you would be able to staple at the top of a stud and at the bottom but not between.

I do staple every other truss and would require it to be done.

Mike P.

 

[luke warmwater]

Re: NM CABLE IN ATTICS???

From my experience, the method of running horizontal across the top of rafters in attics is widely used. Especially when pre-manufactured trusses are used in the framing. Anywhere that I can think of, the wires were not secured other than at each end. I've never seen a job cited for this method either. That doesn't mean it's correct.
I don't think that we should be concerned with Supporting these wires in this case, what are we supporting from??-Gravity. The framing is doing a fine job of supporting the wires. What we're concerned with is Securing the wires, so forget all the other references and apply 334.30.
334.30(A) doesn't apply.
300.4(A)doesn't apply.

 

[bryonb]

Re: NM CABLE IN ATTICS???

Luke,
The following is text from the NEC Handbook following 334.30(A):
"Nonmetallic sheathed cable that runs horizontally through framing members (spaced less than 54 in. apart) and passes through bored or punched holes in framing members without additional securing is considered supported by the framing members."
By your reasoning, if you were to run NM cable in a conventional attic, i.e. not a truss roof, you would not be required to use staples as long as the cable is running at right angles to the joist. I do agree that the cable would be "supported" but it would not be "secured" as required.

 

[luke warmwater]

Re: NM CABLE IN ATTICS???

Bryonb, If I understand you correctly, then no, that is not my reasoning. My opinion is that in an attic, stick built or open truss, when running NM accross the top of the joists, you wouldn't need staples for support(I've never seen roof trusses more than 24" apart), you would need them for securing(every 4 1/2 feet).
334.30(A) doesn't apply the case. We're not talking about running through bored or punched holes. We're talking about running On Top of the roof trusses.
I think we're in agreement, but I'm not sure?

 

[bphgravity]

Re: NM CABLE IN ATTICS???

Some code is open to AHJ interpretation. I think the intent of the code is to ensure the cable is not pulled or moved as to damage the wire after being installed, therefore requiring securing every 4.5 feet. What happens at 5 feet? What happens if you secure at 13" from a box? The concern is for true and real potential hazards, and running the cable over the joist and not securing them is not one of them. Bad workmanship, laziness, incompliant, maybe. Is it going to kill someone or burn down the building, no.

 

[hurk27]

Re: NM CABLE IN ATTICS???

Think about this one a home owner goes up into the attic to clear a wasp's nest now this attic has blown in insulation and the truss are not visable as he is making his way across the attic he lands his foot on what he thinks is a truss bottom cord but instead it is a n/m cable but he doesn't know it and places his whole weight down on it and it pulls the n/m cable through a stapple located 2' away and it shorts out tripping the breaker and he heard the snap from the short. now he knows what he's done and calls an electrican and has it repaired.

Ok same setup but this time the n/m is only stappled down the wall or just at the ends and he stepes on the n/m but this time he's to far away to hear the snap of the short circuit and when he gets down from the attic his wifes yelling that the lights in the kitchen went out. now he call's a electrican and it takes them two days to find out what happened and they have to cut drywall to repair the bad place in the n/m that was only stappled down inside of the wall. and add another box to make a splice for the repair.

Any question's?

 

[iwire]

Re: NM CABLE IN ATTICS???

I think the inspector is correct and when I read the post I though to myself they should be stapled.

Then I thought about how we run MC or NM through the webs of steel truss with out anything securing it all the time in commercial buildings and we never get cited for this so I guess it comes down to the inspector.

 

[mvannevel]

Re: NM CABLE IN ATTICS???

I always stapled NM when running across the chords of trusses, and here in my jurisdiction we require it. I gues the wording can be somewhat confusing, 336-18('99 NEC) says "Supports" but talks about "secured". I think the intent here is not about supporting against the effects of gravity, but about securing the cable in place. Obviously the trusses support the wire from falling down, but the code calls for them to be secured, which to me means fastened in place. This helps prevent damage to the cables during and after construction. Just my opinion. Besides, I always thought it made for a neater installation.

[ March 13, 2003, 08:39 AM: Message edited by: mvannevel ]

 

[harold endean]

Re: NM CABLE IN ATTICS???

If you read section. 336-18 (1999 NEC)it states that NM wire must be "SECURED". So technically it must be stapled or use approved methods to secure the NM. A lot of jobs get passed with the NM just being laid across the ceiling joists and if it is way in the corner where no one can reach it, is there a problem? Probably not. If you read the NEC Handbook it too says that the NM must be secured and not just laid down. My state is still using the 1999 NEC so that is why I refrence that one. The 2002 NEC also says secured.

 

[hurk27]

Re: NM CABLE IN ATTICS???

Harold I agree. but there is some areas that could be left up to the AJH to call like when we run n/m close to the outside wall and the roof is only a few inches above it and there is no room to swing a hammer to even drive a staple in. and there is no way a homeowner could possibly step on the wire to pull it through the staples down the wall then I could see it not being stapled as long as it is not subject to damage from the metal gussets then I think it would be ok but that's only an opinion.