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New & Old Work Wiring

Knob and tube wiring

Becoming the owner of an older, heritage style home, can be thrilling, but also incredibly challenging. If your house was built prior to 1950, you’ll need to consider the type of wiring the home has, for instance, copper, aluminum, or knob and tube. If it is an older house, and it has never been completely rewired, it could have knob and tube wiring. If this is the case, it’s quite likely you’ll have a problem when you begin shopping around to get house insurance.

What can go wrong with knob and tube wiring?

Any of the problems listed below can cause short circuits or overheating. To avoid these problems, you may need to replace your house’s wiring. If in doubt, have an electrical inspection done.

Insulation over the wiring:

If household insulation is installed over knob and tube wiring, a fire is just waiting to break out. The wiring is coated with a rubber/cloth insulation. It needs lots of space to dissipate the heat that builds up when an electrical current is flowing through. If there’s no room, because it’s been covered with insulation, a very dangerous situation is created.


Serious problems can occur when this type of wiring is damaged, either due to wear and tear, handyman fixes, or other types of damage. Porcelain knobs and tubes can crack, and the wires tend to sag and fray over time exposing live wires.

Excess use:

Knob and tube wiring was installed when there were really very few electrical appliances in the average home. Nowadays, with TVs, sound systems, computers, washers, and dryers, the system can easily become overheated. Many times, there is overuse of extension cords, and power bars, as well. Old systems, are just not designed to handle the demands for electricity that occur in our modern computerized world. The ground pin (or 3rd prong) on power bars or other electrical items should never be removed to accommodate the two pin outlets used in knob & tube wiring.


Most problems occur with knob & tube wiring as a result of improper alterations being made to the existing wiring. As it’s such an old system, proper replacement parts are not always available, which could be the reason a lot of makeshift handyman fixes are so dangerous. Knob and tube wiring is easily accessed in the basement, which is perhaps the reason why this wiring is often spliced unsafely with modern wiring by home handymen, as opposed to certified electricians.

What will your home insurance company want to know?

Your insurance company will always want to know what type of wiring your home has. They’ll want to know if the entire house has been wired this way, or if some of the home has been updated. They may require you to have an electrician inspect the wiring, before they can offer you home insurance. A number of problems can occur when only part of the house has been rewired, and the rest of the home still has knob and tube. The connections between the two systems may expand and contract at different rates, causing connections to become loose.

Also, knob and tube wiring runs on a 60 amp service, but most insurance companies will require your home to have a 100 amp service/ breaker panel.

There are companies that will refuse to insure you with knob & tube wiring, as they consider the risk to be too high. However, there are others that will insure your home, perhaps with a higher premium or higher deductibles. There may also be a requirement to have an electrical inspection done by a professional before coverage can be offered.