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If you've found yourself the owner of an older home, or are looking at one, you may have a type of wiring called Knob and Tube. While modern homes have copper-based wiring covered in a plastic insulation sheathing, knob and tube wiring was created before our capabilities with plastics was at this level and so the wire was insulated with rubberized cloth fabric. The wire needed to flow through large open spaces to allow the heat of the wire to dissipate and so ceramic tubes and knobs were used to ensure the wiring did not touch the wood.


Unfortunately, Knob and Tube wiring had several drawbacks, not the least being that the wiring could not touch anything lest the heat conduct and start a fire. As we renovate and changeup older homes, the risk of fires from Knob and Tube wiring increases by any materials that end up close to this wiring. In addition, the rubberized sheathing loses its elasticity over time and can leave the wiring exposed. This is not only a shock hazard but an additional fire hazard. This wiring also did not support ground wiring and so outlets that are Knob and Tube are only two prongs and will not be compatible with grounded devices.
Your insurance company has likely told you to have this wiring replaced if you have a home that contains it and the likelihood of home fire increases the more you modify your home or any of the wiring of Knob and Tube. If you're buying a home with Knob and Tube wiring, do have an inspection done first. We can let you know for sure if this outdated wiring is in your future dream home.

 

Your insurance company has likely told you to have this wiring replaced if you have a home that contains it and the likelihood of home fire increases the more you modify your home or any of the wiring of Knob and Tube. If you're buying a home with Knob and Tube wiring, do have an inspection done first. We can let you know for sure if this outdated wiring is in your future dream home.

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Keith Langlois

RHI | NHI

Registered Home Inspector
National Home Inspector
Licensed Electrician