How to replace old knob & tube wiring?


Have older house, remodeling in steps. Some areas have both k&t wire combined with new 12\2. Best way to trace to source, fuse panel? Some is buried in walls!

  6 answers
  • Kelli L. Milligan Kelli L. Milligan on Jan 23, 2019

    We updated all the wiring and put in a new electrical panel. Didn't trust the way they did the new wiring since it was piece milled.

  • William William on Jan 23, 2019

    Most of the time the knob and tube wiring is disconnected and left if place. A pain to trace and remove it. What ever can be cut and removed is. Everything is rewired to meet current codes. Get a non contact voltage tester and see if any of the K&T wiring is live. It should not be reused or have anything connected to it.

  • Kc Kc on Jan 23, 2019

    If you have to ask about whole house wiring then you need to hire professional help.

    What's really scary is the old stuff combined with the new...really?...or is the knob and tube disconnected and the new wiring is running separately but in the same wall?

  • Seth Seth on Jan 23, 2019


    Our 1839 Greek revival saw every iteration of wiring since the invention of electricity. One of the things you have already probably discovered is that your panel schedule is not accurate and you have no way of knowing who made what "improvements" over the years. K+T by itself was very safe. It's what people did to it over time that caused problems. The most serious issue you are facing is that there is really no way to trace all of the K+T and know what is connected and buried inside walls and ceilings. You might have modern grounded 12/2 going to an outlet and then have active K+T branching off of it. Very often K+T was installed with no rhyme or reason as to what went where. People needed to tap a source when fixtures got added and spliced wiring all over the place usually just taping the connection. You might have all modern wiring coming out of your panel, but as soon as it enters a wall from the basement, it becomes active K+T that you cannot see. Without doing what is called channeling (opening up narrow strips of wall and ceiling) to trace all K+T and pulling out outlet boxes and switches to see what is actually connected, you may never know where all the K+T is. Short of doing that and doing extensive rewiring, the best you can hope for is to isolate it. Any outlet that tests as having no ground (even if it is a 3 prong socket) is suspect. Anything connected to K+T is not grounded. What we did is rewire everything on the first floor because it was easy to get to from the basement. We cleaned up any K+T in the basement, but made note that it was still active going down stream. We separated anything suspect onto it's own 15A line and installed AFCI breakers on those lines. Any outlet we suspected as still being K+T was replaced with a GFCI outlet. Whatever changes you make, keep careful detailed notes for future owners.

  • Call in the pros. If anything ever goes wrong, they are liable. If you do it and something goes amiss, and your insurance company finds out it was a DIY job and not to code, they can deny the claim and drop your coverage. I have seen it happen time and time again. Don't be foolish unless you know local code, have pulled your permits and know what you are doing.

  • Annie Annie on Jan 24, 2019

    So right, Naomi! You need a GOOD electrician.