Recently bought a single story house that was built in 1925, it has a basement and an attic space. I've doing some updates in it, and have noticed some confusing things with the electrical wiring. There is a fuse box in the basement, but only has metal conduit coming out of it and going to the rest of the basement and I think most?! of the main floor.

I've been doing some work in my attic space, and the lightbulb that is wired up there is wired with functioning knob and tube, and there is old k&t all throughout the ceiling joists and attic walls, running to where the outlets and switches are on the main floor.

I am not an electrician, and have a few questions:

  1. Would an electrician only update a portion of k&t to modern conduit wiring and leave some functioning k&t behind??
  2. If so, how can k&t be wired into a system of conduit/modern wiring? Has anyone seen that done before?
  3. If updates were made to at least a portion of electrical, would there still be k&t throughout the attic or would that have been ripped out? How do I test if the existing k&t is functioning?
  4. How important is it to update a fuse box?

It's a confusing problem - thanks for the help in advance!

  • I would update ALL the wiring. My parents live in a house originally bought by my grandparents. I removed all the original wiring which was 2 core with a lead outer sheath. Some had been decommissioned earlier, but some was still live. Now it is all up to date. Actually had an inspection by the Electricity Company and they signed it off as excellent. Apparently best one they had seen in the area, and they were surprised.
    – Solar Mike
    Jun 15, 2022 at 15:15
  • It's very important to check the fuse box for hacks. I.e. the typical and very hazardous putting a coin in under a screw-in fuse when you don't have a spare fuse handy, which then basically makes the circuit unfused. If the fuses are all the size they should be and not bypassed in thet sort of manner, the fusebox should be "safe" in the sense of limiting current as it should. Replacing it it is a good idea, but not as important/urgent as (for instance) replacing an FPE Stablok circuit-breaker panel that's known not to actually limit current in some fault cases.
    – Ecnerwal
    Jun 15, 2022 at 16:09
  • I answered your question, which is "is it possible that previous electricians did X" but I would also like to suggest that as you are now the owner of 1925 wiring, you ought to consider a renovation that includes fully replacing all wiring in the house. If that has never been done, it should be high on your list of priorities.
    – jay613
    Jun 15, 2022 at 18:24

1 Answer 1


I will answer some of your questions.

A house can be partially rewired. A common example is a typical two story house with an unfinished basement and an old fuse box or old panel. You can upgrade the panel, upgrade most of the downstairs wiring, renovate the kitchen and fully rewire that. You can upgrade the service into the house and maybe run some new wiring upstairs, perhaps say for air conditioning. But you don't have to rip open all the upstairs walls and ceilings at the same time to rewire there. You can leave those in place.

K&T can be left behind in various states There are many practices, not all of them wise. When K&T is replaced, the old K&T can be removed or left behind. Commonly, exposed decommissioned K&T will be removed so as not to spook future purchasers of the house. Commonly, decommissioned K&T that is not exposed will be left there. No need to destroy walls just to remove that. It is of course possible that live K&T would be left behind in walls even though it doesn't service any lights or outlets any more.

There are ways to interface most older wiring types with most newer ones. I don't know the details specifically about K&T but at a high level, you would replace what you can, and where some of it disappears into a wall where it remains in service, you'd insert the accessible end into a junction box (using techniques I don't know) and make connections there as with anything else.

  • 2
    Indeed, it's very common to have partial new wiring + partial K&T in service.
    – Ecnerwal
    Jun 15, 2022 at 16:10
  • Yeah, especially on lighting circuits, who cares? It's AFCI protected. Jun 15, 2022 at 23:13

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