replacing 'knob and tube'


Old 08-31-06, 12:34 PM
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replacing 'knob and tube'

Parts of my 60 year old house are wired using the 'knob and tube' method. Other parts have Romex. In the process of remodeling and moving a couple of switches and receptacles I want to convert some of the knob and tube - which runs through the attic - but I don't want to open any walls.

Is there any downside to running the Romex through the attic and adding boxes and connecting to the k & t where it goes down inside the wall? I guess the question is... Is there anything wrong with adding 8 or 10 boxes and splices where before there were none?

Many thanks.
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Old 08-31-06, 12:43 PM
Join Date: Apr 2006
Location: New Bern, NC
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What you just described was a common rewire method when I was just a helper. (lol just a year or so ago... lol)

If this is legal or not is a matter for your local building code, not the NEC.

I would not do it , no way, no how. Knob and tube was great in its time, but the wires are now so old that you cannot guantee that the insulation is safe where you cannot see it.

If I had to sleep in that house, I would want to fish the walls were needed and replace all the wireing.
Old 08-31-06, 03:09 PM
Join Date: Aug 2005
Location: San Francisco, CA
Posts: 749
As someone who is currently in the process of replacing all my K&T wiring with Romex…I”ll strongly second jwhite’s opinion.

Fishing the wire is not that bad at all; unless you hit blocking. There is some drywall work involved, but it’s minimal.

As I cannot pull out the entire run of K&T, I am cutting and taping/wire nutting off as necessary with the abandoned wire. The wire that I am able to cut and pull out, well, the insulation is basically gone.

Rewire the entire thing. If you have access to the crawlspace, it’s really not that difficult for an access standpoint. Of course you would need to know what you’re doing electrically as well.

Good luck.
Old 08-31-06, 03:27 PM
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Just a how-to suggestion. In many cases you may be able to fish the new wire by removing the original outlet box to create a temporary hole for fishing. Once the wire is fished you can use a special box (old work box) with clips in the hole. With care the resulting hole may actually have to be enlarged a bit to fit the old-work box so no wall repair will be needed.

How the original box was fastened determines how to remove it but if nailed to the stud you can often just run a Sawzall between the stud and box to cut the nails.
Old 08-31-06, 03:33 PM
Join Date: Aug 2005
Location: San Francisco, CA
Posts: 749

Great point. That's exactly what I'm doing...sawsall and all.

The only time I've had to cut holes is when I'm near the roof line and I can't get my right-angle drill to the top plate from above, or where there is blocking. Other than that, it's very very easy to do.

Last edited by DIYaddict; 08-31-06 at 03:36 PM. Reason: Removed quote as it's unnecessary to quote the entire post directly above yours
Old 08-31-06, 03:42 PM
Join Date: Aug 2006
Posts: 97
K&T wiring, like Pacific Electric breaker panels, is one of those things that never seems like a problem until it burns your house down (hopefully without you inside of it!). I've seen K&T in older houses that looked fine, but I've also seen it falling apart too. A really big problem is attic spaces, where blown-in insulation can overhead the K&T easily.

I'd do a little drywall patching and fishing to fix it if I were you.
Old 08-31-06, 05:56 PM
Join Date: Oct 2005
Location: Milwaukee WI
Posts: 1,338
The suggestions here are all right on.

Get copies of your state and local codes and a couple of electrical textbooks and do some bedtime reading so you can do it right the first time.

Start in an area that's already in bad shape or that you plan to paint anyway. You can usually tell which side of the box the strap is on, or use a stud finder.

You will need a sawzall, long bits, a flex extension or flex bits, a mirror or two, a fish tape, a mini-hacksaw. A laser for shooting light straight thru a hole, and some nylon string would probably also be helpful. Also maybe a Dremel tool if there are any spots too tight for a Sawzall and too tough for a mini-hacksaw.

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