How to Check Your Home’s Knob and Tube Wiring

How to Check 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 consisted of single insulated copper conductors run within wall cavities, passing through joists and studs.

The wiring was supported along its length by knob insulators made of porcelain or wood attached to the structural framing. Where wires entered a wiring device such as a lamp or switch, or were pulled into a wall, they were protected by flexible cloth tubing called "loom".

Key Features of Knob and Tube Wiring:

Dangers and Issues with Knob and Tube Wiring

While knob and tube wiring was suitable for the low voltage lighting and few appliances used when initially introduced, it can be problematic and dangerous by modern standards. Some key concerns include:

How to Check for Knob and Tube Wiring in Your Home

If your home dates to the 1940s or earlier, checking for the presence knob and tube wiring should be a priority. Here are the main ways to check:

Examine the Electrical Panel

Inspect the Attic and Basement

Check Accessible Outlets and Fixtures

Consider Hiring an Electrician

For a thorough inspection, it may be wise to hire a qualified electrician. They can check wires in walls, perform electrical load calculations, and provide documentation of any issues. This may be necessary for insurance purposes as well.

Options for Remediating Knob and Tube Wiring

If your home does still contain knob and tube wiring, some options to consider are:

Ultimately, the safest option is fully rewiring a home to remove all old knob and tube wiring. But targeted replacements of dangerous or overloaded circuits can be a more affordable intermediate step. Consulting professionals is highly recommended before doing any work.