The Dreaded Knob and Tube

By Wendy Gooditis

Once upon a time, a couple of lovely people decided to sell the wonderful 1920s bungalow in which they had raised their families and been happy for almost 30 years. As hard as it was to contemplate parting with their beloved home, they felt certain that the next occupants would appreciate and care for it as they had. A locally respected agent listed it and found them a buyer for a reasonable price with which everyone could be satisfied.

Then came the home inspection required by banks before they will finance a mortgage. Usually, for a house which has been cared for by sensible people, the home inspection turns up myriad small repairs, such as doors which don’t close properly, some rotten boards on the porch, a leaky pipe under the sink, etc. But sometimes, especially in older houses, the repairs—and the surprises—are huge.

As a result of the inspection, these nice, responsible, intelligent people learned that the electrical system in their house was still the antique knob and tube wiring which had been installed when the house was built. The unpleasant surprise was this: they had had the house inspected when they bought it years before, and it had been found to be knob and tube, and had supposedly been completely rewired at the time! But the electrician paid to do the job had merely replaced all easily visible wiring and the electric panel box in the cellar. He hadn’t touched all the wiring in the lath-and-plaster walls throughout the house. This electrician has since gone on to a place where he is no longer reachable to be made to take responsibility on earth for his earthly actions.

A problem like this is a huge and costly repair, which these sellers took on in good faith in order to sell the house. But what had been thought to be a $10,000 job grew to be more than $15,000, and the sellers no longer stood to make the expected good return when they sold their house. These sellers were unusual in that they fulfilled this task with no complaint, and are to be admired for their sense of honor. The lucky buyer got a fantastic deal on a completely rewired house.

So what is knob and tube? It is the system commonly used in the 1920s and 30s, and sometimes used right up through the 1950s. It consists of insulated wire wrapped around ceramic knobs nailed into the studs, and fed through ceramic tubes inserted into holes in the joists. Hence the knob and tube nomenclature. It was a sturdy system which worked for many years in many houses, and still functions well in some houses today. But time, temperatures, gnawing mice or squirrels, and additions or changes make most of these outdated systems quite risky. The old methods of insulation ranged from cotton fabric to aluminum, all of which are far inferior to today’s insulated wire.

William Kibbel III, The Home Inspector on the useful website old house web had this to say: “When additional branches or fixtures are added, the fuses protecting the old circuits are likely to blow frequently. Installing larger fuses is an easy, but unsafe, solution. Oversized fuses allow much more current to flow than originally intended, resulting in additional heat in the conductors. This heat causes the insulation protecting the wire to become brittle, and eventually to disintegrate.” Uninsulated wires and overloaded systems can and do lead to house fires.

On top of these risks, add the fact that knob and tube systems were not grounded. Because the wires were insulated and the hot and neutral wires were installed several inches apart, most of the time the system was safe. But here’s why the grounding required by code in modern electrical systems is so vital to our safety, according to the website HowStuffWorks: “The primary purpose of grounding is to reduce the risk of serious electric shock from current leaking into uninsulated metal parts of an appliance, power tool, or other electrical device. In a properly grounded system, such leaking current (called fault current) is carried away harmlessly. The human body may be fatally shocked by a current of less than one ampere—well below the point at which a fuse or breaker will operate. Grounding helps prevent such a hazard from occurring. In some cases, however, as when a person handles an electrical device while standing on a wet surface, there is a risk of fatal shock from a leaking current even from a properly grounded electrical circuit. For protection against this danger, a safety device called a ground-fault interrupter can be installed in the circuit. This device, so sensitive that it can detect leakages as small as 5 milliamperes, immediately disconnects the circuit when a leakage occurs.”

These are installed in our bathrooms today, required by code, and cannot be correctly installed on a knob and tube system.

Now you understand the concept of grounding and why it is desirable, right? And you understand how the presence of knob and tube wiring can jeopardize not only the safety of a home and its occupants, but also a real estate transaction.

There are many reputable electricians in our area who have the experience to tackle the job of knob and tube remediation. And if you are the owner of an old house still using knob and tube, you can have the job done a room or two at a time to save mess and to spread out costs. Friends of mine in one of the large, lovely houses we all admire as we drive down certain streets in Winchester started this process a year ago, and have a couple of rooms rewired every couple of months. They are pleased with their schedule, and are more pleased that they are soon to be free of the worry about the outdated electrical system.

Wendy Gooditis is a real estate agent on the Chip Schutte Real Estate Team with ReMax Roots at 101 East Main St., Berryville, VA 22611, phone 540-955-0911. Wendy can be reached at or at 540-533-0840.