Is Knob & Tube Wiring Legal? Untangle the Facts..
Old historical features that come with an older home may be appealing to some home buyers. The stained glass and original high quality materials are what attracts people to homes that are 100+ Years old. Consequently an additional feature that may come along is the presence of knob and tube wiring. Does it really matter if knob and tube wiring is present?
Knob and tube setup
WHAT IS KNOB AND TUBE WIRING?
Electrical service to residential American homes began in the mid 1890's and surged from 1920 to 1940, by this time 75% of residential American homes were connected to the electrical grid. The primary go to wiring installation between 1890-1910 was knob and tube wiring. During this time knob and tube wiring was quite dependable and a surprising a number of American homes STILL rely on electric that is supplied with knob and tube wiring typically with modern updates.
Generally speaking knob and tube itself is not considered a safety concern but may be a safety hazard due to deterioration, damaged wiring and or improper modifications. Although knob and tube wiring is NOT illegal it is no longer permitted (the installation of new knob and tube wiring) in new construction today. Meaning if it is currently installed within a structure it is legal despite many misconceptions .
IS KNOB AND TUBE WIRING DANGEROUS?
Generally speaking there is not a code or mandate that requires the removal (some local jurisdictions may require removal under certain circumstances) if your home contains knob and tube wiring. But, wiring such as Knob and Tube does have inferior properties. Knob and tube wiring over time may tend to stretch, sag, deteriorate and or pass through insulation that may cause the wiring to overheat. Remember the wires were hung in air so they can dissipate heat – if the wires are passing through insulation this may lead to overheating. The outside casing is made of rubber which can deteriorate overtime especially if exposed to extreme temperatures/humidity levels such as an attic or basement. Additionally knob and tube wiring does not contain a ground.
Frayed knob and tube wiring
Knob and tube passing through insulation
If a home that contains knob and tube wiring was properly modified along side newer wiring such as romex and the visible knob and tube wiring is in serviceable condition you may have not much to worry about. Knob and tube wiring should be a concern if it appears to be in rough shape, not properly installed and or modified incorrectly.
HOW DO I KNOW IF MY HOME HAS IT?
Curious if your home has knob and tube wiring? To confirm if knob and tube wiring is present in your home just take a look in your basement and attic for white, ceramic circular knobs that are typically secured by a nail to the joists or rafters. The wires pass through the knobs and the tubes protect the loose wires (See pictures).
If knob and tube wiring is not readily visible in your home it doesn't necessarily mean that you don't have it. Knob and tube wiring may be hiding behind the walls which is often referred to as spider webbing.
WHAT SHOULD I DO IF MY HOME HAS KNOB AND TUBE WIRING?
If you have discovered knob and tube wiring in your home you are not required to replace it. If you are interested in upgrading your knob and tube wiring to modern wiring we recommend you hire a licensed electrician for the job. Updating your electrical wiring from knob and tube can cost around $5500 - $15,000 (can be more) depending on the size of the home. You may want to have your current knob and tube wiring inspected to make sure it is in serviceable condition.
Read more on knob and tube wiring: THE TRUTH BEHIND KNOB AND TUBE WIRING