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 passing through ceramic knobs and tubes, which provide protection and structural support.

The knobs separate the wires to prevent contact between them, while the tubes protect wires where they pass through framing members. This old wiring system did not include a ground wire, relying on the air between conductors as insulation.

The Rise and Fall of Knob and Tube Wiring

Knob and tube wiring became popular as electricity spread through cities in the late 19th and early 20th centuries. It was an inexpensive and straightforward way to add electrical wiring during a time of rapid development and expansion.

By the 1920s and 1930s, knob and tube wiring was the standard wiring method used for lighting and power in most homes and commercial buildings. However, it started to decline in the 1930s and 40s as newer and safer wiring methods emerged, like non-metallic sheathed cable and concealed armored cable.

Dangers and Downsides of Knob and Tube Wiring

While knob and tube wiring met the needs of the early electrical era, it has some significant drawbacks and dangers:

Why Knob and Tube Wiring Remains in Many Homes

Despite the risks, it is estimated that millions of older homes across the United States still have original knob and tube wiring. Here are some key reasons this obsolete wiring lingers today:

Dangers to Consider If Your Home Still Has Knob and Tube

Here are some specific risks to weigh if your home still relies on aging and hazardous knob and tube wiring:

Weighing Your Repair Options

If you discover your home has original knob and tube electrical wiring, here are some repair options to consider:

I recommend consulting with a certified electrician to explore which option is best for your unique home and budget. Living with outdated knob and tube wiring is not worth the serious safety risks it poses for you and your family.