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Pulling New Wire Through Old Knob and Tube

I'm new to the forum, so please forgive me if this has been covered. I couldn't find anything when I searched.

Setting the stage:
I recently purchased a 1920's rowhouse, and I'm working on replacing the knob and tube wiring in the first floor ceiling. The house has three rooms, front to back, each separated by a framed partition wall: living, dining, kitchen. The side (shared) walls are all plaster on brick, so no chance of fishing under baseboards through framing. I tore down the plaster and lath living room ceiling due to damage, but the other two rooms had new drywall ceilings when I moved in. There is a single circuit run of K&T that services a center ceiling fixtures in each of the three rooms. I was able to run new cable up from the basement, through a switch in the living/dining partition wall, and to the ceiling. Now the fun begins...

The problem:
I had hoped to pull the new cable (I'm using 14-2 and 14-3 MC-Lite) by attaching it to the old K&T wires, which I can access both through the ceiling fixture hole and through the open ceiling in the living room. Unfortunately, I quickly realized that, even though the tubes were all installed with the same orientation (flared end facing the rear of the house), if I attach the new cable to the old wire, the first tube will dislodge from its joist, but then it gets pulled along to the next joist, and the flared end gets stuck. The MC cable doesn't fit through the tube, so I have a logjam: joist, tube, MC cable. It's clear that I have to allow the tubes to drop down out of the way, but I don't see a way of making that happen without losing the connection between the old and new wires. I tried my luck pulling one shorter old wire and then fishing with fiberglass glow rods, but the joist holes don't align particularly well, and it took quite a while to get the rod through 3 joists. I'm dreading the longer runs, which span 4-6 joists.

The question:
Is there any way to take advantage of the fact that there is an existing wire running through joist holes before I just yank them and start fishing? I'd thought about taping a tiny, powerful magnet to the old wire, then pulling it and following closely behind with a rod, hoping the rod could "find" the old wire after the tube dropped out of the way, but that seems improbable. Other than that I have no ideas and would sure appreciate a miracle trick.


Re: Pulling New Wire Through Old Knob and Tube

Get a Fein Multimaster and start pulling up floorboards upstairs or access. Use it to cut down trough the tongues of the T&G. Or make a hole in the ceiling at every joist. Or fish up the wall to the joist bay in line with where the ceiling box is, and cut one hole at the wall/ceiling vortex to bring the wire through the plate (if it's balloon framed, no plate to drill through)

Re: Pulling New Wire Through Old Knob and Tube

Welcome to another joy you get for free with the ownership of an Old House!

You can probably manage to feed a fish tape through a few of the old holes- 4 if you're lucky but past that it's almost a futile effort (and this much may take an hour's fishing around, re-bending the end of the fish tape for each effort). So maybe you have only 4 joists to go through and you might manage it, but any further and it's open something up to gain access. Perfect straight lines for the tubes wasn't considered worth the effort back than so it's always hit-or-miss trying to fish through them. Short of trying one of those newer endoscope-type cameras I can't see any other way you'd be able to find all the holes since you can't know exactly where they are. But do try, for with each hole you get through that's one less place you have to cut open access!

There are plenty of old houses with K&T in the between-floor ceilings and since the chances of them ever being disturbed are essentially nil, it's generally safe to leave those and reuse them. It will not meet any codes to do that and if you have knowledge of it your homeowners insurance company won't like it either. I would upgrade if it were me- I like knowing that the wiring is positively safe and new, but that choice is up to you.

K&T should never be left anywhere that is accessible for if you can get to it then something else can too and short it out. Don't see the work you go through with an Old House as troublesome; see it as learning and practicing new skills and you'll feel better about it all in the end!


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