Replace Old Electrical Wiring

Learn how to replace old electrical wiring. Find out why insurance companies may not insure an older home with knob-and-tube wiring, and learn how to rewire your home.

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LESLIE: Larry in Utah is on the line and he’s got a question about wiring. What can we do for you?

LARRY: I’ve got this 100-year-old house; at least half of it’s 100 years old and the other half is in the 50s and it needs to be rewired.

TOM: OK.

LARRY: Some of the wiring is still the original wiring; it was put in about 1920. And the other half of the house it was put in about 1950 and it still has screw-in-type fuses.

TOM: OK, well first of all, why do you want to rewire it? Is it because you’re concerned about the fuses? Because if that’s the case, there is no concern. As long as the fuses are correctly installed they will protect the wiring. Or do you want the convenience of circuit breakers?

LARRY: Prefer to have the circuit breakers, but my insurance company tells me they’re not going to continue to insure it with the old wiring in it.

TOM: Because of the 1920s wiring? Do you have what’s called knob-and-tube wiring?

LARRY: Yes.

TOM: OK, well I understand that. Knob-and-tube wiring was sort of the very first form of house wiring and it basically looks like pieces of wire that is strung from beam to beam and wherever they go through the beams they go through a ceramic tube and wherever they go across the beams they sort of hang off like these ceramic sort of spacers and that’s why they call it knob-and-tube wiring.

The other problem with knob-and-tube wiring is that it’s not grounded, it’s not groundable and, also, in a more modern house we tend to insulate over those wires and that’s a problem because they were designed specifically to be air-cooled. So when you insulate them they become unsafe. So I certainly understand that concern.

If that’s the case, you have a couple of issues here. First of all, you need to rewire those circuits and, separate from that and only if you want to, you need to replace the panel. My point about the fuses is that if they’re properly sized they’re just as safe as circuit breakers but if you’re doing all this work, probably not a bad time to install new circuit breakers at the same time. As far as that 1950s wiring, that could be wired right into the panel. I don’t see any reason to replace that. That wiring should be grounded. If you need to add some additional circuits do that but the only wiring that you have to replace is the knob-and-tube. The 50s wiring, probably armor-clad cable; that’s probably OK.

LARRY: OK, thanks very much.

TOM: You’re welcome. Thanks so much for calling us at 888-MONEY-PIT.