If you have a house built before 1970, or are thinking of buying one, you need to know something about wiring. Older houses can be a spaghetti factory of wires — copper, aluminum, knob and tube, often mixed together — which could be a safety hazard and will definitely impact any renovations you may be planning.
But isn't all wiring the same?
No. And different types often can't be mixed together. Today's electrical wire is copper and is used in a three-wire system — two power and one ground wire, wrapped in a plastic sheath. It's connected at junction boxes, and runs to your panel, usually to circuit breakers, though some houses still have glass fuses.
Knob-and-tube wiring is an old system with two wires running separately and parallel to one another, without a ground. The "knob" and "tube" are the ceramic fittings that keep the wires from touching framing, and anchor it as it runs through the house. Generally, 15- and 20-amp fuses were used in the electrical box.
(HOLMES GROUP)
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A big problem
This wiring system was okay in its time, and if you are using about the same amount of electricity as people did in the 1940s and '50s and the components are in good shape, it's adequate today. But that is rarely the case. The big problem is that old wiring was designed for different amperage. In "the old days," people just didn't use that much power in a day; they would have had a few lights, small appliances, a radio and a television.
No one uses that little electricity any more. For appliances alone, our electrical consumption has multiplied many times in the past 50 or so years. Asking knob-and-tube wiring to handle a modern load is like putting traffic from a multilane highway on a two-lane dirt road.
Is it dangerous?
Absolutely. First it leads to blown fuses. Because of that, homeowners replace 15-amp fuses with 30-amp ones, which leads to overloaded circuits and, possibly, electrical fires.
Rat's nest of wires
What you often end up with in an older house is a rat's nest of old knob-and-tube and new three-wire thrown together, as homeowners either do it themselves or hire a "brother in law who used to be a contractor" to run a line or two. Or build up a permanent tangle of extension cords to meet the increased load. You would not believe some of the electrical disasters I've uncovered when doing a renovation.
Whenever I uncover knob-and-tube wiring in a home that has had some upgrading, I know I'll find some terrible electrical problems. Who do you blame? The electrician who didn't demand that the old knob-and-tube be replaced when he did the new work? Or the homeowner who let it happen and was satisfied with shoddy, make-do work, maybe to save some money? Even a good electrician can't force a homeowner to do the right thing. He could refuse to accept the job, but the homeowner will probably just hire some hacker to do it anyway.
Knob and tube clues
There are telltale signs that old and new wiring have been slapped together. In older homes, only one outlet was usually installed in bedrooms. So if there are two or three outlets, you can bet there is old and new wiring patched together. And any time you find wiring run along the tops of baseboards or around door casings, it's likely you have new and old.
Hidden wiring in finished basements — usually those done without a permit — is the worst scenario. I've found dozens of junction boxes with wiring that is almost impossible to trace. Under the building code, it is supposed to be possible to inspect every junction box, but too often they are buried behind drywall.
I've seen situations in which new plugs were installed with new wiring only to find that it's attached to old knob and tube about four inches away, inside the wall. Another trick is to put in a new plug and attach a wire to it to look like a ground wire, and run it to a pipe somewhere so it tests properly.
You need an expert
If you are buying a house with a knob-and-tube system, you need an experienced electrician to come to inspect the wiring. Professionals are the only ones who are specialized and can catch deliberate cheating.
Don't kid yourself: It's important to get an invasive inspection of the wiring done, not just a surface one. You have to break a little drywall to really check.
Knob-and-tube wiring is not bad wiring, but such systems have usually been tampered with, and they won't handle the load a modern house places on them. If you have knob and tube, I bet you have an electrical problem. It's time to do it right and make the upgrade.
Most insurance companies won't cover houses that have a knob-and-tube system. A lot of people complain that that's "unfair," and that they can't afford to bring the electrical system up to code.
Maybe, but wouldn't you rather be protected with a system that's safe, up to code, and able to handle the demands you place on it?
Mike Holmes is the host of Holmes on Homes on HGTV. E-mail Mike at mikeholmes@holmesonhomes.com.
