running cables across attic


Old 08-17-06, 11:08 AM
wgc is offline
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Join Date: Dec 2005
Location: New England
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running cables across attic

I'm planning to run some new wiring across the attic to replace some 60 yr old ungrounded stuff for a new light fixture, and am trying to plan the best route, plus have a general answer for any future work. How would you run the cables? What is code compliant vs what do you think is better? Do any of these existing runs sound bad enough to redo?

The house is a Cape with an unfinished attic that may be finished some day in the distant future. Some approaches are:
- The original wiring is simply run through the firring strips and joists of the ceiling below, with no protection other than the plaster ceiling. If that is still a valid strategy, it would be the easiest to do, would keep the wiring out of the way, would not interfere with insulation, and would not be affected by any future additions.
- Most previous owner work is stapled up a rafter then strung unsecured through the collar ties about 8' up. That is also easy to do and is out of the way but I wonder if it's a good idea to have it unsupported and unsecured even if it is mostly out of reach. That may or may not be in the way of future additions or roof work but would be easy to move.
- I could drill through the joists below, but that is a lot of extra work, makes it more difficult to deal with insulation, and would need to be redone if any future addition required more structure.
-A running board sounds like the best approach to me, but I don't know the limitations or best practices. I could run 2x4's the length of the attic across the floor joists down in the eves where the roof is about knee high, then staple the wiring along the surface of that. The wiring would be exposed, but secured, completely supported and in a hard to reach location. Any future additions short of a full second floor would not affect this since it would be behind the knee wall.

What do you think? Am I missing any options or pros and cons? What would you do if this were your house?

Last edited by wgc; 08-17-06 at 11:24 AM.
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Old 08-17-06, 12:05 PM
wgc is offline
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Join Date: Dec 2005
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How to cross dormer windows

Plus, how would you cross a dormer window?

- a running board seems like a bad idea since it could get stepped on.
- stapling to the roof structure?
Old 08-17-06, 04:16 PM
Join Date: Apr 2004
Location: Ontario Canada
Posts: 1,767
I'd run it through the joists. I'd plan my wiring around a dormer.
Old 08-18-06, 06:30 AM
Join Date: Feb 2006
Location: USA
Posts: 6,458
Running boards

Install running boards in pairs with enough space between them for the wires. Rest the wire on the joists between the running boards.
The running boards protect the wire from being stepped on or having the weight of an object placed on it.
Old 08-18-06, 10:53 AM
Join Date: Jul 2006
Location: Bozeman
Posts: 10
I like Wirepuller38's option. If you are going to finish off the attic, more than likely everything will need to be moved anyway.

I would discourage you from drilling ceiling joists, trusses or rafters if you don't already see existing holes. The lumber is your roof system is designed to carry a specific load. Drilling these weakens the structure and voids the design. I recommend consulting a structural engineer before drilling holes in ceiling joists, trusses or rafters.

Installing the wiring in the furring strips is a bad idea. If someone puts a screw in the ceiling, it could easily penetrate the cable and start a fire. The cable needs to be a minimum of 1 1/4" up from the ceiling.

Laying the romex horizontally on the attics trusses or joists is ok unsupported. However any vertical runs need to be supported within 12" of the connector and every 4 1/2'

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