Recently I submitted an offer on an older house in Castlegar. The insurance agent I deal with wants to know the approximate age of the wiring in this house before his company will insure the building and contents. So I’ve opened my electrical panel box and looked at the wiring. Some of it looks older than the rest. Is there any way I can answer his question just by looking at these wires?

The good news is yes, anyone can figure out the approximate age of the wiring in his or her house if you have some basic information. All building wiring since early on has been covered with an insulating protective coating. This coating is the key to identifying the age of a particular wire. For instance, the earliest type of home wiring called “knob & tube” was sheathed with rubber. All house wiring since then has been encased in some type of casing to prevent the neutral, hot (and ground wires in modern wiring) from touching each other. Each type of casing is commonly connected to a particular time period. So here is the list of time periods that can be relied on to provide the approximate age of the wiring in your home.

Knob & Tube: rubber casing 1920 – 1950  (also identified by their distinctive porcelain knobs & tubes supporting the branch wiring.)

two or three wire cables with no ground wire – 1945 to early 1960’s

Cloth Sheathed: two or three wire with an integral ground wire – Early 1960’s to early 12970’s

Cloth sheathed aluminum wire with an integral ground: – 1964 to 1978

Plastic sheathed aluminum cable with an integral ground wire: – 1974 to 1978

Plastic sheathed copper cable with an intragal ground wire: - 1974 to date

Be cautious when opening your electric panel. Remember your dealing with a potential killer. Consider completing this investigation in the company of a qualified electrician. Happy sleuthing!