Knob and Tube Wiring

by Gary | April 11, 2023 | Whole House Rewire

What is Knob and Tube wiring

Knob and tube wiring (sometimes abbreviated K&T) is an early type of electrical wiring used in homes built before the mid-20th century. Knob and tube wiring gets its name from the white ceramic “knobs” and black “tubes” that encase the copper wiring carrying electricity as it winds through the house. It was made up of two insulated wires, one hot and one neutral, shielded by a flexible cloth insulating sleeving. Cotton fabric soaked in asphalt served as the original insulation before rubber became widely used. These cloth insulated wires were run within wall or ceiling cavities, and protected by porcelain insulating tubes that were drilled through joist and stud drill holes. They were held along their length by porcelain knob insulators that were nailed into place. 

Is Knob and Tube Wiring Safe?

No, you should have your whole house rewire if you have knob and tube wiring. Knob and tube wiring is outdated and can be dangerous, as it is not up to current safety standards. It is also not suitable for modern electrical needs. A professional Pasadena Electrician can assess your home and determine the best course of action for rewiring.

When was Knob and Tube Wiring Used

If it was wired before 1950 and has not been upgraded it likely needs rewiring to replace cloth-insulated wiring. If the home has cloth-insulated wiring. If the home has knob and tube wiring. This is typical in homes built before 1935. If you are planning a major renovation, a partial rewire may be considered as you may want to add large appliances that require a dedicated circuit or add lighting where there was none. This is potentially the best time to rewire your home as the walls will likely be open and will help cut down the costs.

When Did Knob and Tube Wiring Stop?

Knob and tube wiring was a popular method of electrical wiring used in homes from the 1880s to the 1940s. However, it is now considered outdated and unsafe due to its lack of grounding and inadequate insulation, which increases the risk of electrical fires and electrical shocks. Therefore, replacing knob and tube wiring is highly recommended.

Sometimes called Tube and Knob Wiring

The system is missing a ground wire, which is an additional cable that runs deep into the earth. Therefore, these wires are not grounded, so they are not considered safe for modern electrical systems. This is a vital safety element because if something goes wrong in the home, the ground wire provides a channel for the excess power to be discharged.

Knob and Tube Wiring Replacement

You must hire a licensed electrician for knob and tube replacement. It is not a DIY project, and it requires the services of a licensed electrician.

The electrician will inspect the existing wiring system to determine the extent of the replacement required. They will then design a new wiring plan that meets current electrical code requirements and provides adequate electrical capacity for the home. The electrician will need to turn off the electricity supply to the home to avoid any accidents during the wiring replacement. The electrician will carefully remove the old knob and tube wiring without damaging the walls or ceilings.