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wiring in attic

I have demoed my upstairs and plan to make a studio apartment for my son. Most of the wiring is old (1920s) and in need of updating. Our ground floor lights are currently on knob and tube. My question is "do I need to run the new wiring through conduit or "flex" or can I simply run NM cable on top of the joists in the dead space and then insulate?" I don't want to drill holes through the joists if I don't have to and I don't want to completely remove the knob and tube, just yet, as there are other things that are still on that circuit. I have already run new wiring for the outlets upstairs with NM running through the wall studs. Please advise.....

Re: wiring in attic

My recomendation is, if you have the time or money, just do the job right the first time and replace the knob and tube. NM cable dosen't need to be protected from insulation, but it can not be trampled on either. Make sure when you say dead space, that there is no way you walk on it or damage it somehow.

Re: wiring in attic

Like Mike says, NM can be run along the top of the joists (bottom chord of the trusses), but if it's in an area that's accessible to people (i.e., it could be stepped on) it must be protected. A 1x4 running parallel and adjacent to the wires is generally considered adequate protection.

Re: wiring in attic

Not going to comment on the rest of the post because there are a few hundred variables and I do not like to type.

Keep in mind that the National Electrical Code does not allow Knob and Tube to be encapsulated in insulation.

Re: wiring in attic

You say you already have NM run for the upstairs so is there any way you can attach to that instead of the knob and tube? Keep in mind the anticipated electrical load especially for TV, computer, air confitioner if necessary.

The best way to do it would be to give it its own breakers in the breaker box and run new cable straight up. Regardless of time and additional cost, its the right way and the safest way! You dont need all of your hard work burning down because you wanted the cheap/easy way out.

Re: wiring in attic
dcalabro wrote:

You say you already have NM run for the upstairs so is there any way you can attach to that instead of the knob and tube?

I probably should have mentioned I have run NM from the breaker box to the upstairs in an effort to take some of the load off the knob and tube. I have two circuits run for the upstairs and am running two new circuits to replace the knob and tube powering all the ground floor lights and ceiling fans. My next project is to run new circuits up through the basement to power wall outlets. This should eliminate the need for the knob and tube altogether and I can remove it from the panel. This will also help clean up the tangle of 88+ years of "add ons". How my house passed inspection and hasn't already burned down is beyond me.

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