Knob and Tube Wiring . . . .
What is it and is it dangerous?

Knob-and-Tube wiring was the predominant wiring system through the 1920’s and 1930’s; although some installations of knob-and-tube wiring continued in houses up until around 1950. Knob and tube has many differences from current wiring such as ROMEX, the most common used wiring in new construction. Modern wiring runs directly through holes in the structural components (joists, studs, and rafters). Knob and tube wiring used protective ceramic tubes placed in the holes to prevent the wire from being damaged against the woodwork. These ceramic knobs and tubes are an easy way to identify if your home has knob and tube wiring. Knob and tube wiring had visible connections that were soldered together and then wrapped with tape. Any connections with other wiring forms are wire nutted together and then placed in a junction box.

The biggest problem with knob and tube wiring has nothing to do with the original wiring. It has everything to do with what has happened after the fact. Homeowners, amateur electricians, and age are some of the factors that can cause problems with knob and tube wiring. Most houses that I have inspected that have knob and tube wiring also have a mixture of other forms of wiring. The problem is that sometimes the new wires and the knob and tube are not correctly attached together. Wires that are improperly connected and outside of a junction box, too many outlets, lights, or both on a circuit, missing or damaged insulation, and over fused circuits can all lead to problems in a house wired with knob and tube. In all fairness though, these same deficiencies can cause problems with newer Romex, rag romex, and BX wiring also. Except that knob and tube does not have a ground wire, it is not necessarily any more dangerous than other wiring forms as long as it was not altered incorrectly.

Insurance companies are starting to get stricter about insuring a home with knob and tube wiring, which can also add to the frustration of dealing with knob and tube. Although it is getting harder, there are still companies that will insure homes with knob and tube and I suggest that you shop around for the best prices and coverage.

Of course, it would be better if your house did not have any knob and tube wiring, although having it doesn’t necessarily mean that you should be overly concerned about it. The best thing to do is to have a qualified electrician further evaluate your homes wiring system and contact several insurance companies to get their stand on it. This way you can make an educated decision based on what their recommendations are.






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