What is Knob and Tube Wiring, What it Looks Like and How to Remediate

Knob and Tube Wiring

What is Knob and Tube Wiring, What it Looks Like and How to Remediate

Knob and Tube wiring, also known as K & T wiring, is one of the types of wiring that was used for electrical installations at older homes. Before the implementation of this method another method called open wiring was used for electrical installations. In open wiring bare conductors were used along the surfaces such as ceilings, walls and floors. Although this method was simple and inexpensive, it included high risk of shock and electrical hazards.

To overcome this problem knob and tube wiring was made into use. K & T wiring uses conductors in black insulation covering, which reduced hazard of electric shock as compared to open wiring. The K & T method was commonly used in the early 19th century, almost 1890s to 1950s, in North America but has become outdated now due to advancement of world in the field of electrical installation.

Still some older places might have K& T wiring installed in them, so let’s discuss construction, concerns and remediation about knob and tube wiring.


Construction and Working

Knob and tube wiring consists of three main components:

  • Knobs

These are cylindrical in shape and made up of white ceramic material.

  • Tubes

   These are made up of porcelain material and used for protection of wiring through the material it passes such as wood.

  • Copper wire

K & T wiring comprises of copper wiring that is one neutral and one hot. These wires are commonly used in a black insulation covering.


These copper wires run through porcelain made knobs and tubes. Knob holds the wire in place while tubes protect the wire from being in touch with any surface that can cause electric hazard such as overheating and shock. K & T wiring does not contain any ground wire.

Concerns about K & T wiring

It was first designed for small home appliances such as fryer, electric kettle, and toaster etc. But engineers started to use in the wiring system of buildings which arose many concerns about the safety of buildings and residents. K & T wiring does not contain any ground wire which increases the risk of fire and damage to sensitive equipment. Due to unavailability of the third wire, it was not possible to use K and T wiring system in the 3-wire appliances. Moreover, it sags overtime. So, it is not suitable to use this wiring system in this modern era. Insurance companies generally ask that such wires be replaced before they insure the house. Due to this, identification and modification of this wiring is necessary.

How to identify Knob and Tube wiring in buildings

To identify knob and tube wiring is necessary for safety in this era. If you are the owner of any old building or want to buy some, you need full inspection to avoid the loss. If you are

Knob and Tube Wiring

unaware of the wiring system of the building and want to explore that if your building has K & T wiring, then you can take following steps:

  1. Before any kind of inspection, make sure that the power is turned off. Safety is the first priority in electrical systems.
  2. Visual inspection is easy in the case of K & T wiring because of its structural elements. Look for ceramic tubes and porcelain knobs.
  3. This wiring is mostly done in crawlspaces or attics, so look for the exposed structural elements of knob and tube wiring in such places first.
  4. If you don’t find any exposed ceramic tubes and knobs in the house that doesn’t mean you don’t have K & T wiring. There are chances of hidden knobs and tubes in the walls, so, call professionals for the identification by digging into the walls.


Remediation for K &T wiring

The following modifications are necessary if the building has K & T wiring.

  1. Seek expert advice on the condition of the wiring in your building.
  2. Based on the expert advice, make a blueprint for modernization of your electric system.
  3. Sometimes there are chances that only a few modifications will be made to the system such as a few fixes in the damaged insulation or upgradation of some circuit breakers.
  4. Some safety measures like removal of K & T wiring from kitchen and less use of high voltage devices may also help to prevent any damage.
  5. In some cases, if the wiring is completely damaged then complete wiring is modernized which causes a lot of cost depending on the buildings’ infrastructure.



K & T was a good implementation in past era but due to its use in buildings and improper modifications, it has become a safety hazard. Engineers need to change and rewire any building having k & T wiring due to the need of modern wiring system.

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