Knob and Tube Wiring


In most cases, century old homes are very desirable and boast many features that are unparalleled with homes of a more recent era. Architecture, masonry work, solid wood trim carpentry, there are many examples where modern day practices just do not measure up to that of the olden days . . .

However, knob and tube wiring is definitely one exception.

History of Knob and Tube Wiring

Knob and tube wiring is an obsolete wiring method used in the early 1900’s. It has been estimated that over 100 000 houses in South Western Ontario are still wired with knob and tube.

Knob and tube wiring is a single conductor, ungrounded system, where electricity is brought from typically a 60 Amp service to various areas of the home by running copper wires (covered with a cloth and rubber insulation casing), through the walls, attic and floor spaces. Porcelain knobs are used to secure the wires and prevent them from contacting combustible surfaces. Wires are threaded through porcelain tubes and holes are drilled anytime wire runs through a stud or joist.

Concerns of Knob and Tube Wiring

Knob and tube wiring is a valid concern for the following reasons;

  • It is an ungrounded method of wiring and is widely deemed unsafe by design. When there is a shorted condition, the electricity has no safe place to travel; this could be a potential shock hazard
  •  Usually very brittle and deteriorated due to its age, making it very difficult to work with (knobs crack due to heat, insulation frays exposing live wires) becoming a potential fire hazard
  •  Home owners and non-electricians can unknowingly create a hazardous situation when trying to update/modify wiring themselves, unaware of the potential dangers
  •  2 pronged receptacles installed with knob and tube wiring are not compatible with 3 pronged plugs used with modern appliances, devices and power bars
  • Not code compliant with E.S.A. - O.E.C. (Electrical Safety Authority – Ontario Electrical Code)
  • Many insurance companies give 90 days to remove all knob and tube wiring or they will not provide coverage
  • When selling a home with knob and tube there is vulnerability for leverage against you because most are reluctant due to the reputation of a knob and tube wired home
  • Knob and tube wiring is very restrictive to add loads to a circuit
  • Fire hazard

Solutions for Knob and Tube Wiring

There are two main solutions for knob and tube wiring that is safe and code compliant;

The absolute best solution is to replace all knob and tube wiring with new, grounded type copper wiring. This will totally eliminate any potential risk of shock hazard or fire hazard, creating peace of mind for your family that things are safe and sound at home

The second option would be to install GFCI protection at the beginning of each ungrounded circuit. This method is less expensive than a full rewire and feasible if the existing wiring is in (good enough) condition

How Much Damage Will Be Done To My Ceiling And Walls

At Live Electric, we have specialized tools for fishing wires without damaging the surface. Fish tapes, fish rods, drop chains, and lots of tricks up our sleeve to keep your home intact during a rewire. We remove baseboards to fish, pull carpet back and drill through the floor boards, whatever options we have to conceal with wiring. When there is no other option, we carefully cut a hole for access (ideally in an inconspicuous place like inside of a closet wall) and fish our wire from point A to point B. When we are complete, we refasten the piece we did cut so all that is left is a small patch job.

Things you should know  

Knob and Tube wiring is obsolete wiring method that is outdated and potentially hazardous for your home, let us help you create a safer environment for you family with our expertise.