How to Safely Work on Your Home’s Knob-and-Tube Wiring

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 knobs and tubes which act as insulators and physical supports.

The knobs are round or hexagonal porcelain insulators that separate the wires from each other and the surrounding surfaces. The tubes are circular or rectangular porcelain or fiber tubes that protect wires where they pass through framing members.

This old system has largely been replaced by modern sheathed cables passing through drilled holes in framing. However, many older homes still have original knob-and-tube wiring, which can present safety issues but also has historical significance.

Dangers of Knob-and-Tube Wiring

While knob-and-tube wiring was sufficient for the electrical needs of most homes in the early 20th century, it can be dangerous by modern standards. Some key risks include:

Evaluating Your Knob-and-Tube Wiring

If your older home has knob-and-tube wiring, it's important to have it thoroughly evaluated by a qualified electrician before undertaking any work. They should check:

The electrician can then advise if replacement, upgrades, or other changes are recommended for safety. They can also identify any wiring that should be preserved for historical accuracy.

Working Safely With Knob-and-Tube Wiring

If your home still has live knob-and-tube circuits that are in good condition, it is possible to work with them safely by following precautions:

Replacing Knob-and-Tube Wiring

In many cases, completely replacing knob-and-tube wiring provides the only way to bring an electrical system fully up to modern safety standards. Typical steps include:

Replacement provides maximum safety but comes at a higher cost. Grants may be available in some areas to assist homeowners with knob-and-tube replacement expenses.

Working Safely Around Deactivated Knob-and-Tube

If old knob-and-tube wiring has been made fully deactivated and dead, it can be worked around safely using simple precautions:

Preserving Historical Knob-and-Tube

If your home has original knob-and-tube wiring that is in good intact condition, it may have historical value worth preserving. This can be facilitated by:

With proper care and precautions, the knob-and-tube wiring in your older home can be either adapted for continued safe use or turned into a unique historical feature to maintain. By partnering with experienced electrical professionals, you can ensure your family's safety while also preserving a bit of the past.