Many houses constructed pre 1950’s have what is called knob and tube wiring. One can determine if you have this type of wiring in your home, by closely looking at basement joists or attic rafters. To determine if your home is wired ” knob and tube”, look for ceramic knobs or tubes in which the wire gets attached to, or passes through, joists or studs. If the knob and tube wiring is not easily visible, you can usually tell by looking at your electrical outlets and switches.
You may only have two prong outlets to plug into. Basically, no ground at each outlet or fixture outlet means knob and tube wiring is present, likewise if you have older pushbutton switches, this is also a good sign you may have knob and tube Nowadays, Home owners with knob and tube wiring may find it difficult or impossible to obtain insurance on their home because most insurance companies are not likely to insure a house they perceive as high risk. Insurance companies usually require a certificate of inspection and compliance from a licensed electrician, that all knob and tube has been removed and replaced with modern 3 wire grounded circuits before it will insure a home that previously had knob and tube wiring. After the electrician rewires your home, they give you a satisfactory assessment of your home, and the insurance company will consider giving an insurance policy for your house. B. Overview of Knob-and-Tube Wiring Knob-and-Tube wiring was the predominant wiring system through the 1920 s and 1930 s; some installations of knob-and-tube wiring continued in houses up until 1950. There are several distinguishing characteristics of knob-and-tube wiring in comparison to current wiring methods