Is Knob & Tube Wiring Dangerous ?

Knob and Tube

Knob and Tube Wiring, also called Open Wiring, was commonly used in the 1900’s to the late 1940’s.

If the Knob & Tube Wiring system remains unchanged, has been carefully maintained, and all repairs have been made by a licensed electrician, this wiring method would still be safe to use today. Unfortunately this is almost never the case. As the wiring ages and deteriorates, porcelain knobs and tubes may break up, old wires sag and fray, and the sheathing turns brittle and falls off, exposing the live wires.

Aside from worsening as a result of age, the majority of problems with Knob & Tube Wiring are caused by tampering and when alterations are made to the original system by handymen.

Add to this scenario the unsafe practice of modifications made to contemporary appliance cords in order to make them compatible with the old and outdated 2 prong receptacles, extensive use of extension cords and power bars, household insulation installed over the wires, and you have the potential for a serious problem.

A combination of Knob and Tube Wiring and modern wiring is commonly found in older homes today. If this work has been done by an unauthorized no-professional person the potential for disaster is certainly present. In many cases the “updating” is not visible in the attic or basement, instead it is hidden behind the walls as it was probably done during a previous renovation or addition to the house.

So, to respond the question of whether Knob and Tube Wiring is safe, the answer is: it can be. But this method has long outlived its time and should be replaced with current procedures.

What is the best Knob and Tube Solution?

Removing the old Knob & Tube wiring and replacing the entire system to meet today’s Canadian Electrical Safety Code standards is usually the best solution.

Exchanging the old ungrounded switches and receptacles with CSA approved devices is another significant safety measure.

Installing a new electrical service panel that provides for the needs of today’s average household usage and also allows for any potential future needs or plans, addresses the problem of blown fuses, overloaded circuits and other safety concerns.

Excerpts from ESA – May 1, 2009


  •  Knob & Tube wiring is unsafe.
  •  All knob and tube wiring must be disconnected and replaced.
  •  The Ontario Electrical Safety Code no longer recognizes knob and tube wiring as an acceptable wiring method.


  •  Knob & Tube wiring is safe, provided it is properly maintained by competent licensed people as outlined above.
  •  The Electrical Safety Authority as well as the Ontario Electrical Safety Code recognize and accept knob and tube wiring methods.
  •  The Ontario Electrical Safety Code 2002 edition contains rules that govern the installation of open type wiring methods (knob & tube). Rules 12-200 to 12-224 set out the minimum safety standards for the installation of open wiring, which may still be installed to this day.

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