What is Knob-and-Tube Wiring?

Knob-and-tube wiring was an early standardized method of electrical wiring used in buildings in the United States from about 1880 to the 1940s. It consists of insulated copper conductors running through ceramic knobs and tubes, which provide protection and structural support.

Key features:

This old wiring system has largely been forgotten as most homes have transitioned to modern wiring methods. However, some older homes still have remnants of knob-and-tube wiring, which poses some risks but also some surprising benefits.

Why Knob-and-Tube Wiring Was Used

Knob-and-tube wiring became the standard electrical wiring method in the late 19th century. It offered important advantages over earlier wiring methods:

The knob-and-tube system continued to be installed into the 1930s, even as new wiring methods emerged. The components were simple and reliable, though labor-intensive to install.

By the 1940s, knob-and-tube wiring was obsolete as new systems like armored cable offered more capabilities. However, the old wiring remains in many old houses.

Dangers and Downsides of Knob-and-Tube Wiring

While knob-and-tube wiring was safe when installed correctly, it does pose some risks in older homes:

These risks are very real in deteriorated, modified, or overloaded knob-and-tube systems. However, well-maintained, undisturbed knob-and-tube wiring can often still be safe and serviceable.

Surprising Benefits of Knob-and-Tube Wiring

While knob-and-tube wiring can certainly be dangerous, maintained systems also have some surprising benefits:

So while knob-and-tube wiring should never be used for new installations, maintained vintage systems can sometimes be superior to modern wiring in durability and safety.

Protecting Myself With Knob-and-Tube Wiring

As the owner of a home with knob-and-tube wiring, I take specific precautions to protect myself:

While upgrading the wiring would provide greater safety, I have chosen to preserve this bit of history. With proper diligence and maintenance, the well-installed knob-and-tube system in my old home remains safe, serviceable, and able to protect me.


Knob-and-tube wiring reminds us of an earlier era of electrical work, before home circuits became complex and lighting became abundant. While obsolete for new installations, well-maintained vintage knob-and-tube systems can still be safe and reliable when properly inspected and cared for. With attention and caution, the forgotten knob-and-tube could perhaps save my home from electrical hazards, just as it did decades ago.