Knob-and-tube wiring

Knob-and-tube wiring (sometimes abbreviated K&T) is a single-insulated copper conductor run within wall or ceiling cavities, passing through joist and stud about ½”-holes via protective porcelain insulating tubes, and supported along their length on nailed-down porcelain knob insulators. Where conductors entered a wiring device such as a lamp or switch, or were pulled into a wall, they were protected by flexible cloth insulating sleeving called loom.

Elements Of Knob and Tube

Ceramic knobs were cylindrical and generally nailed directly into the wall studs or floor joists

Ceramic tubes were inserted into holes bored in wall studs or floor joists, and the wires were directed through them.


Compared to modern electrical wiring standards, these are the main technical shortcomings of knob-and-tube wiring methods:

never included a safety grounding conductor

permitted the use of in-line splices in walls without a junction box

Over time, the price of electrician labor grew faster than the cost of materials. This removed the price advantage of K&T methods, especially since they required time-consuming skillful soldering of in-line splices and junctions, and careful hand-wrapping of connections in layers of insulating tape.

Modern home buyers often find that existing K&T systems lack the capacity for today’s levels of power use. First-generation wiring systems became susceptible to abuse by homeowners who would replace blown fuses with fuses rated for higher current. This overfusing of the circuits subjects wiring to higher levels of current and risks heat damage or fire.

Knob-and-tube wiring may also be damaged by building renovations.[8] Its cloth and rubber insulation can dry out and turn brittle.[7] It may also be damaged by rodents and careless activities such as hanging objects from wiring running in accessible areas like basements.

As existing K&T wiring gets older, insurance companies may deny coverage due to a perception of increased risk.

We are experts at preserving your Heritage Home

House Depot has performed old wiring replacement jobs in the Toronto area. We use special tools and techniques in combination with our years of experience to upgrade the wiring of your vintage home.  This could be due to kitchen remodeling or new construction

By choosing House Depot you will find that we:

  • Each job is assigned a project manager from beginning to end who will listen to you and will take care of your questions, requirements, and other concerns
  • Detailed Progress Report is provided on all significant events
  • Provide an Electricians Report to satisfy insurance companies
  • Clean-up and restore power at the end of each work day
  • Protect your furniture, cover all floors and stairs
  • Provide patch-up services to wall and ceilings making them ready for paint
  • Thoroughly clean-up and remove all garbage at the end of the job 

Reasons to replace knob and tube wiring:

  1. Fire hazard caused by uncontained sparks from arcing
    2. Unable to serve enough power for today’s electrical devices and appliances
    3. New wiring due to remodeling of the house, or in majority of cases kitchen renovation