How to Safely Inspect and Repair Knob and Tube Wiring

What is Knob and Tube Wiring?

Knob and tube (K&T) wiring was an early standardized method of electrical wiring used in buildings from about 1880 to the 1940s. It consists of single insulated copper conductors running through ceramic knobs and tubes, and uses air as an insulator between the wires.

While K&T wiring is considered obsolete today, it can still be found in some older homes and buildings. The wiring can be dangerous if damaged or improperly modified. However, with caution and care, K&T wiring can be safely inspected and repaired.

Dangers and Risks of K&T Wiring

There are several key risks associated with old K&T wiring systems:

Inspecting Knob and Tube Wiring

Inspecting K&T wiring should only be performed with extreme care by a qualified electrician. It involves identifying all locations of K&T wiring and systematically checking its condition throughout the building. Key inspection steps include:

Visual Inspection



Repairing and Upgrading Knob and Tube Wiring

Repairing K&T wiring should only be done by a licensed electrician as it requires extensive experience and care when working with live K&T circuits. There are three main approaches:




Key Safety Tips

With proper safety precautions, inspection, assessment, and repairs by a qualified electrician, K&T wiring can often be repaired or upgraded to allow it to be safely maintained in older homes. However, replacement is the best option to eliminate risks.