Knob And Tube Wiring

Knob And Tube Wiring: Should You Rewire?

What Is Knob And Tube Wiring?

Knob and tube wiring refers to the first generation of electrical wiring. It was installed in homes between 1900-1950. While it was once considered cutting-edge technology, knob and tube systems are largely considered risky, and having this type of wiring may make your home non-insurable.

Knob and tube conductors are characterized by single wires wrapped in a cloth-based sheath. The conductors run in parallel pairs and are supported by porcelain tubes and as they travel through wooden framing members, and porcelain knobs as they travel along wooden framing members. The conductors must be physically separated to prevent them from shorting out. It is considered a free air wiring system.

Is It Safe?

Here are 3 technical issues to be concerned about:

  1. There is no ground wire. The main reason for ground wires is to help prevent shocks. Knob and tube wiring is not grounded.
  2. It is a free air wiring system. Most homes have attics with insulation. Many insulation contractors will not insulate homes with knob and tube wiring due to law suits.
  3. It predates temperature ratings on wire. Yes, in fact it is older than radio.

Some inspection agencies claim it is not inherently dangerous provided that:

  1. The insulation is in tact – You really cannot see very much of the wiring in most homes, although it is generally most affected above ceiling mounted light fixtures because of long term exposure to heat from light bulbs. Knob and tube wiring pre-dates temperature ratings, so no one really is sure what rating it has. Two generations later, most home wires were rated for 75 degree Celsius. For almost 40 years the standard has been 90-degree Celsius. Many light fixtures require this temperature rating to be safely installed.
  2. Additional outlets have not been added to it – Every house old enough to have knob and tube wiring has had some electrical additions. Some are no doubt done professionally by a licensed electrician, and many are not. Too many outlets on a circuit is a problem for any type of wiring.
  3. The wires are properly protected by the correct fuse or breaker – All wiring should be properly protected by the correct size of breaker.

Will It Affect My Ability To Get Insurance Coverage?

Some insurance companies refuse to provide coverage for homes with knob and tube wiring because of their unreliability and safety concerns. The following reasons are often cited as reasons to decline coverage:

  • Knob and tube systems weren’t designed to meet modern electrical requirements. Considering that simply making toast and coffee in the morning demands about 20 amps of electricity, it’s easy to see how your electrical system will be quickly overloaded. Many light fixtures also require 90’C wires, which is frequently overlooked.
  • Knob and tube systems aren’t grounded, which is now a code requirement for electrical installations. Grounded circuits are safer because they reduce the risk of shock if an appliance malfunctions.
  • Knob and tube systems aren’t easily accessible because they’re installed behind the walls. This makes them more difficult to inspect for safety concerns.

What Should I Do If My Home Has Knob And Tube Wiring?

Hire a Licensed Electrical Contractor with extensive experience replacing knob and tube type wiring.

Langstaff And Sloan: Specialists In Knob And Tube Replacement Services

Langstaff and Sloan has provided residential and commercial electrical services in the GTA since 1991. Our licenced electricians specialize in knob and tube rewiring, and we also patch and holes that might be required. Langstaff and Sloan is dedicated to providing our clients with reliable services at competitive rates. Contact us today for an assessment and to book an appointment.