How to Fix Old Knob and Tube Wiring in Your Home

How to Fix Old Knob and Tube Wiring in 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 single insulated copper conductors run within wall cavities, passing through joists and studs.

The conductors are supported on ceramic knobs and separated from each other by about 1 inch by ceramic tubes at crossover points. This method of wiring has largely been replaced by safer and more efficient systems, but may still be found in some older homes.

Dangers of Knob and Tube Wiring

Knob and tube wiring can pose several safety hazards:

Signs You May Have Knob and Tube Wiring

Here are some signs that a home may still contain old knob and tube wiring:

Options for Replacing Knob and Tube Wiring

If your home contains old knob and tube wiring, here are some options for replacement:

Full Rewiring

This involves removing all old wiring and installing entirely new circuits and wiring throughout the home up to modern electrical code. This ensures maximum safety and capacity but is the most expensive option. Expect costs of $8,000-$15,000.

Targeted Rewiring

With this approach, only the most problematic wiring is replaced by running new wiring in easier to access spaces like attics and basements. Keep costs lower at $2,000-$8,000 but doesn't address all risks.


Individual circuits are upgraded by splicing short sections of modern wiring into existing wires. Very cost effective at $1,000-$2,000 but doesn't replace old wiring within walls.

DIY or Hire an Electrician?

Replacing knob and tube wiring is a complex project best left to licensed electricians familiar with old electrical systems. Mistakes can lead to fires or electrocution.

However, minor targeted improvements like pigtailing individual circuits may be DIY-friendly. Always get proper permits and have work inspected.

Prioritizing the Replacement Project

When planning and budgeting your wiring replacement project, focus first on:

Safety Tips for Homes with Knob and Tube Wiring

If full rewiring isn't possible right away, here are some tips for managing risk:

Replacing aging knob and tube wiring improves safety and prevents fire risks. Prioritize high-risk areas but consider fully rewiring over time.