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 consisted of single insulated copper conductors run within wall cavities, passing through joist and stud drill-holes via protective porcelain insulating tubes, and supported on nailed-down porcelain knob insulators.

This old wiring system does not meet current electrical code requirements and can pose fire and shock hazards due to lack of grounding, disintegrating insulation, and overloading. However, some of this wiring still exists in older homes and requires safety measures.

Dangers of Knob and Tube Wiring

Knob and tube wiring poses several fire hazards if left as-is:

These factors lead to electrical fires breaking out in walls and ceilings where knob and tube wires run unchecked. It is crucial to address and fix this outdated wiring method to protect your home and family.

Signs of Problems with Knob and Tube Wiring

Watch out for the following signs of faulty knob and tube wiring:

These are indicators of loose connections, overloads, and dangerous electrical faults in old wiring. Have an inspection done if you notice any of these.

Solutions for Replacing or Fixing Knob and Tube Wiring

Here are your options for dealing with old knob and tube wiring:

Full Replacement

Replacing knob and tube wiring completely ensures safety. This involves:

However, full rewiring is expensive ($5,000 to $15,000) and disruptive with walls being opened up.

Targeted Partial Rewiring

You can opt to replace knob and tube wiring selectively in the most high-risk areas:

This is a more affordable option but still leaves some old wiring in place.

Insulation Installs with Warning Signs

Rather than rewiring, you can opt to just install protection in the form of:

This doesn't eliminate the risk but contains it to some degree.

Electrical Load Management

Using power safely with old wiring involves:

Manage usage to avoid overloading circuits to prevent shorts, sparks, and fires.

When to Contact an Electrician?

It's always advisable to have your old electrical systems professionally assessed rather than take risks yourself.

Consult certified electricians if you notice any warning signs, before doing renovations or upgrades, or simply for your peace of mind. They can:


Knob and tube wiring found in older homes can lead to dangerous electrical fires given its many limitations. Address this outdated system by having it replaced or upgraded in the areas of highest risk. Practise safe electrical usage by managing your power loads. When in doubt, have your original wiring inspected by professional electricians. Investing in electrical safety will protect your home and family from tragedy.