How the Forgotten Knob-and-Tube Electrical Wiring Method Could Burn Down Your Home

What is Knob-and-Tube Wiring?

Knob-and-tube wiring was an early standardized method of electrical wiring used in North America from about 1880 to the 1940s. It consists of insulated copper conductors passing through porcelain knobs attached to joists or studs and supported every few feet with porcelain tubes.

While knob-and-tube wiring was considered safe when it was first introduced, it does not meet today's electrical standards and can be very dangerous. The insulation around the wires becomes brittle over time, leading to cracks and exposure. This can cause electrical arching, sparks, and potential fires.

Why Knob-and-Tube Wiring is Still Around

Although knob-and-tube wiring has not been installed for over 70 years, it still exists in many older homes that have not had their electrical systems updated. Some estimates suggest over 25 million homes in the United States still have some knob-and-tube wiring.

Homeowners are often unaware their home contains this outdated and potentially hazardous wiring method. It can be hidden behind walls, ceilings, and insulation. Unfortunately, many homeowners only discover it when problems arise.

Dangers and Risks of Knob-and-Tube Wiring

There are several significant dangers and risks associated with knob-and-tube electrical wiring:

Fire hazard: The degradation of the wire insulation over time leads to cracks and exposure. This can cause sparks, electrical arching, and overheating that can ignite surrounding combustible materials. Knob-and-tube wiring is responsible for over 500 house fires per year.
Lack of grounding: Knob-and-tube wiring has no ground wire, putting occupants at risk of electrical shock. Ungrounded wiring can also lead to damage of connected appliances and electronics.
Overloading: The wiring is insufficient for handling the electrical demands of modern households with numerous appliances and devices. Overloading the wires can lead to more overheating and fire risks.
Unsafe wiring practices: Attempts by homeowners to tap into existing knob-and-tube wiring to add outlets or lights can compound the hazards if done incorrectly.

Signs You May Have Knob-and-Tube Wiring

Watch for these signs that may indicate the presence of old knob-and-tube wiring:

Your home was built before 1950.
Light fixtures are prone to flickering.
Circuits trip or fuses blow frequently.
You see insulation around antique ceramic knobs and tubes in unfinished areas like the attic or basement.
Rooms have a limited number of outlets.
You do not have a ground wire on some outlets.

Why Knob-and-Tube Wiring Needs to Be Replaced

While some people try to claim that old knob-and-tube wiring is fine if left undisturbed, it is simply not worth the risk. The wisest and safest choice is to have any knob-and-tube wiring in your home replaced by a licensed electrician as soon as possible.

The hazards and limitations far outweigh any perceived benefits of leaving antiquated, unsafe wiring in place. Homeowners insurance policies may also explicitly exclude coverage for damage caused by knob-and-tube wiring. Replacing it can prevent tragedy and provide much needed peace of mind.

The Process of Replacing Knob-and-Tube Wiring

Replacing knob-and-tube wiring involves:

Having an electrician conduct an assessment to locate all the existing wiring.
Getting necessary building permits for the wiring replacement project.
Running new wires through walls, attics, and basements as needed.
Installing new electrical boxes and outlets.
Ensuring grounding and GFCI protection is in place.
Properly capping off and removing any accessible knob-and-tube wiring that is no longer in use.
Having the completed work inspected before covering it up.
Getting safety certifications from the electrician before using the new wiring system.

It often takes running completely new wiring throughout the home to eliminate all the risks. Trying to reuse some parts of the old system or just capping it off creates lingering dangers.

Conclusion

Knob-and-tube electrical wiring has no place in modern homes. The risks substantially outweigh any benefits of keeping the antiquated system in place. Homeowners should have their home inspected by an electrician and take steps for total replacement as soon as possible. Although the process takes time and money, preventing catastrophe is invaluable. Protect your family and property by taking action to eliminate hazardous knob-and-tube wiring.