Knob & Tube Wiring

Our Home Inspector Found a Rather Unique Item Today. Knob-and-Tube wiring was the predominant wiring system through the 1920 s and 1930 s although there are some installations of knob-and-tube  wiring d in houses up until 1950

Problems Associated with K&T Wiring:

  • Unsafe modifications are far more common with K&T wiring than they are with Romex and other modern wiring systems. Part of the reason for this is that K&T is so old that more opportunity has existed for improper modifications.
  • The insulation that envelopes the wiring is a fire hazard.
  • It tends to stretch and sag over time.
  • It lacks a grounding conductor. Grounding conductors reduce the chance of electrical fire and damage to sensitive equipment.
  • In older systems, wiring is insulated with varnish and fiber materials that are susceptible to deterioration.

Compared with modern wiring insulation, K&T wiring is less resistant to damage.  K&T wiring insulated with cambric and asbestos is not rated for moisture exposure. Older systems contained insulation with additives that may oxidize copper wire. Bending the wires may cause insulation to crack and peel away.

K&T wiring is often spliced with modern wiring incorrectly by amateurs. This is perhaps due to the ease by which K&T wiring is accessed.

 

Advice for those with K&T wiring:

  • Have the system evaluated by a qualified electrician. Only an expert can confirm that the system was installed and modified correctly.
  • Do not run an excessive amount of appliances in the home, as this can cause a fire.
  • Where the wiring is brittle or cracked, it should be replaced. Proper maintenance is crucial.
  • K&T wiring should not be used in kitchens, bathrooms, laundry rooms or outdoors. Wiring must be grounded in order to be used safely in these locations.
  • Rewiring a house can take weeks and cost thousands of dollars, but unsafe wiring can cause fires, complicate estate transactions, and make insurers skittish.
  • Homeowners should carefully consider their options before deciding whether to rewire their house.
  • The homeowner or an electrician should carefully remove any insulation that is found surrounding K&T wires.
  • Prospective home buyers should get an estimate of the cost of replacing K&T wiring. They can use this amount to negotiate a cheaper price for the house.

From Knob-and-Tube Wiring – InterNACHI http://www.nachi.org/knob-and-tube.htm#ixzz23dXTZajP

From Knob-and-Tube Wiring – InterNACHI http://www.nachi.org/knob-and-tube.htm#ixzz23dXJn0zF

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