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 tube insulators, which provide protection and structural support.

This old wiring system has largely been replaced by newer and safer methods, but it can still be found in some older homes and buildings. While knob-and-tube wiring is often considered obsolete and dangerous by today's standards, understanding how it works and its unique quirks can potentially help me stay safe in a building that still utilizes this vintage wiring technique.

Key Components of Knob-and-Tube Wiring

Knob-and-tube wiring gets its name from the nobs and tubes used to route and insulate the wires:

Unique Attributes of Knob-and-Tube Wiring

There are a few distinctive characteristics of knob-and-tube wiring that are important to understand:

Dangers and Risks of Knob-and-Tube Wiring

While knob-and-tube wiring was safe when first installed according to the standards of the time, it does pose some risks from a modern perspective:

Staying Safe in a Home With Knob-and-Tube Wiring

While knob-and-tube wiring can seem very precarious by modern standards, there are steps I can take to stay safe if I am living in or visiting a building that still utilizes this old wiring method:

Weighing Replacement vs Continued Use of Knob-and-Tube Wiring

For homes still relying on knob-and-tube wiring, the question eventually arises: should I rewire or continue using the old system? There are pros and cons to each choice:

Pros of Rewiring:

Cons of Rewiring:

Pros of Keeping Existing Wiring

Cons of Keeping Existing Wiring:

I need to weigh the pros and cons carefully for my specific home. Hiring an electrician to provide an assessment is key to determining if replacement wiring is urgent or if the knob-and-tube wiring can safely be maintained a while longer.


Knob-and-tube wiring reminds me of bygone eras but poses real safety risks from modern viewpoints. While rewiring provides the only comprehensive solution, I may be able to safely live with knob-and-tube wiring for some time if I understand its quirks and take precautions. With proper vigilance and respect for its antiquated nature, the forgotten knob-and-tube just might help preserve life and property rather than endanger it.