Knob and Tube Wiring

November 20, 2013

Do you have knob and tube wiring?

If your home was built prior to 1950 then you may still have this type of wiring and not even know it. Most homes with knob and tube wiring have been at least been partially upgraded to

knob and tube by Laurascudder

work with modern outlets and lighting fixtures. Sometimes homes will even have new wiring at the breaker panels and the original knob and tube wiring being used for lighting circuits on the second or top floor of the home.

What is knob and tube wiring?

It is the oldest residential wiring. Ceramic knobs support the wiring as it runs along its course, and then ceramic tubes are used to protect the wiring as it passes through floor joists and wall studs. This wiring was used until around 1950.

Is it Safe?

If the wiring has not been abused or tampered with then it should still be capable of carrying electricity throughout your home & should not be inherently unsafe. However, the safety really depends on the history and quality of the modifications and upgrades that have been done to the system. If you suspect you have knob and tube then it is best to have a qualified electrician evaluate the system for the safety.

Knob and tube wiring concerns and issues:

  • Improper Splices- ┬áSplicing into this type of wire is not easy and requires a trained professional. A qualified electrician should be able to do a proper and safe splice, however, inspectors often find splices that were done incorrectly and are dangerous.
  • Not a grounded system– this means the system cannot be used to wire modern outlets. it was only designed and intended to be safely used with un-grounded applications
  • Brittle insulation-the insulation around the wiring was not designed to handle high temperature environments such as caused by modern ceiling mounted light fixtures. If the wire is being used for inappropriate applicationlighting fixture by moreno0101

Will insurance carriers decline to write home’s with knob & tube wiring?

Yes, most home insurance carriers will not write a new policy for a home with knob and tube wiring. If you are buying a home with any knob and tube wiring then you will probably either have to replace all the wiring to qualify for  home insurance, or you can ask that the seller upgrade prior to agreeing to buy the home. The home seller may have hard time understanding why this is needed because they most likely are currently insuring the home. They may have insurance because they may been,with same carrier for years and were not even been questioned on the original application about the wiring. Whereas, the insurance carriers over the years have become more and more reluctant to write home with this type of wiring due to the losses they have experienced from homes that have had this type wiring improperly modified.

Cost of updating the wiring

If you only have a few circuits to replace then it should not be very expensive. However, if your home has knob and tube throughout then to bring the home up to modern standard and to meet the current building codes will be more expensive. part of the reason it that more electrical outlets will most likely need to be installed and the breaker panel may need to be upgraded to accommodate more circuits being added and all of this results in a greater cost.