When performing a home inspection on older homes built from around 1880 to the 1940’s, one of the things our home inspectors are on the lookout for is knob-and-tube wiring. Knob-and-tube wiring is the black cloth-covered wiring that was installed using the white ceramic “knobs” and “tubes” to support it and to protect it where it runs through wood.
Knob-and-tube in a wall cavity
What is knob-and-tube wiring?
wiring system used in the early days of bringing electricity into homes. Knob-and-tube wiring isn’t inherently dangerous given its original conditions; however, it is a potential fire hazard and considered outdated by today’s standards. Many times, the initial installation of knob-and-tube wiring has been altered, added to, or covered with insulation in the attic space.
How to identify knob-and-tube wiring
Knob-and-tube wiring is usually found in attics and unfinished basements or crawl spaces. This wiring is typically insulated in a black cloth-like material, is wrapped around ceramic knobs, and passes through ceramic tubes in the home’s framing. The hot and neutral wires are both black and run parallel to each other. Splices were done by removing a portion of the insulation, pig tailing or wrapping the spliced wire, and soldering them together. The splice was then heavily wrapped with cloth-like electrician’s tape.
Knob-and-tube with white insulation
The potential dagers of knob-and-tube wiring
· Unlike modern wiring, knob-and-tube wiring is not grounded. Grounding of electrical wiring in homes started in the 1960s.
· Do-it-yourself or improper modifications may have been made over time. Sometimes these modifications were not soldered at splices, or the bare wires were left exposed.
· Modifications are prone to overloading the original circuit design. Adding to circuits to support modern electrical needs can overload knob-and-tube systems, resulting in fire.
· There could be missing insulation, either due to rot and decay over time or from rodents chewing on the wires. Exposed wiring may lead to electrical shock or death.
· Covering knob-and-tube wiring with insulation in attic spaces or walls does not allow heat to dissipate. This type of older wiring has a higher electrical resistance and will become too hot, possibly resulting in a fire.
· Knob-and-tube wiring will become unreliable over time. Take notice of lights that flicker, warm switch plates, or sparks when plugging or unplugging devices at outlets.
Knob-and-tube in an attic space
How does knob-and-tube wiring affect your insurance?
Obtaining insurance may be difficult if you have knob-and-tube wiring in your home. Some insurance providers will offer additional coverage for homes with knob-and-tube wiring, while others will deny coverage outright. Due to the increased potential for fire and damage to your home and personal belongings, insurance coverage for a home with knob-and-tube wiring may have higher premiums.
Summary
Replacement of knob-and-tube wiring is not required by code, but if you have this type of wiring in your home, for safety’s sake, you should seriously consider having it inspected by a licensed electrician. When performing a home inspection, our home inspectors will clearly note knob-and-tube wiring in your home inspection report. Our practice is to “recommend further evaluation for adequacy and safety” by a licensed electrician. An electrician will be able to tell you if you have a hazard or not and if the knob-and-tube wiring needs to be replaced.
At HomePro Inspections, our home inspectors are trained to inspect electrical systems and identify any defects. Any issues are documented in your home inspection report and recommended for resolution by a qualified professional.
Visit our website to learn more or to schedule your home inspection in the Rochester, Owatonna, and Faribault, MN areas. You can contact us today at (507) 202-8942 or utilize our online “Schedule Now” feature to set up an appointment.