Running new NM-B cable thru attic

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  #1  
Old 04-26-15, 05:26 PM
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Running new NM-B cable thru attic

I am in NJ, Somerset county.... Running new 20A to my bath at the other end of the house from the panel.... since I have an open attic I pulled the cable up the the attic and then all the way to the bath and down.

My question is around the cable run in the attic :

Do you need to run the cable in any particular fashion?
I am thinking that for the neatness I will run it up and attach to the rafters as they cross.
Also....how do you handle insulation? Do you run the cable under or on top of the insulation (assuming fiberglass rolls).
Anything else to watch out for or to make it future-proof ?

Thanks!
 
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Old 04-26-15, 08:23 PM
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Why run it along the rafters then have to deal with where it drops down to the bathroom?
Run it along where the wall and roof meet then along side the joist where it needs to feed down to the bathroom.
It can also be run along the top of the joist if it's protected with a 2 X 4 along side of it so no one can step on it.
In your area there should have been a minimum of R-40 to 50 of insulation with is about 12", what's there now?
 
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Old 04-27-15, 12:19 PM
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If your attic has permanent stairs, the cable must be protected for its entire length. If it only has a scuttle hole, the cable must be protected within 7 feet of the scuttle. In either case, the cable should run along and be stapled to a framing member such as a 2x4.
 
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Old 04-27-15, 06:58 PM
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what does it mean "protected" ? Do I need to get a conduit ?
My attic has the pull down stairs.

Joe - I don't want to run them along the wall/roof line as it is very tight there....don't feel like crawling over fiberglass.... and I would just rather run it up and then down the joist to the place where it needs to drop to the ceiling of the bathroom.

I have R30 now...planning on putting more before winter....so that's why I also want to run it on top.... I would think it unwise to run a cable between layers of insulation..but of course I could just lift it before placing second layer of rolls.
 
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Old 04-27-15, 07:04 PM
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You can come up the nearest roof rafter, along the main ridge beam and then follow the nearest rafter back down to where you are going.
 
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Old 04-27-15, 07:40 PM
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thanks...so pending clarification from ibpooks on the stairs and protection of the cable - it sounds there is no code that would prevent me from either running it up or just laying it down on the insulation....

As for other tips...I guess it is up to me and how I like it best....but still if somebody has a good tip or an idea based on experience of doing 100 of those - please share.

Thanks!
 
  #7  
Old 04-28-15, 08:00 AM
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In my experience inspectors have not considered the pull down stairs to be permanent. The intention of the code is that if you can easily walk into and walk around the attic, then any cables cannot be exposed to where they could be stepped on or create a tripping hazard.

In your case it sounds ok to just run the cable along some of the existing framing without need for adding additional protection beyond that. It can run above or under the insulation as long as it is running along framing members stapled at least every 4 feet. Cables cannot be loose through the attic.
 
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