Regal Home Inspections, LLC recently did an inspection in Matawan, NJ. The house was over 100 years old and it’s a time capsule for the evolution of residential illumination (Lighting). In this home were at least 3 distinct technologies seen. Assuming that they never used candles, the original illumination in the house was gas lights. Pipes were installed that delivered gas to the wall fixture. An open flame illuminated the area. There’s a movie, Gas Light where someone uses a gas light to try to convince another that they’re crazy. The phrase was popularized in 2022 making, “Gaslight” one of the words of the year.
This was in the attic of this Matawan house. Also in the house was Knob & Tube wiring.
The next iteration of residential wiring was knob and tube. Knob and Tube (KnT) wiring was the state-of-the-art around the 1920’s and 1930’s. We’ve found a lot of knob and tube wiring during the nearly 4000 inspections over the years. In addition to KnT being old, insurance companies don’t like the added risk that it causes. KnT circuits are usually ungrounded. There is no ground wire. That wasn’t much of an issue in the 1930s but 21st century electronics (Computers, modern TVs, etc.) all must be grounded.
KnT circuits have, knobs (Seen in all three photos starting with the one immediately to the left and the two following). The knobs are ceramic and secure the individual wires.
The tubes are also ceramic and are used when the wires have to be installed through wood joists or rafters. If you’re considering buying a home built in the 1940s and earlier, MAKE SURE to have an inspection and use an inspector, like Regal Home Inspections, LLC, that knows what to look for in determining if KnT is or may be present. If KnT is present, a licensed electrician must evaluate and replace all KnT wiring.
Circa the 1940s & 50s, cloth sheathed cables and conductors were used. The wire, in many cases, was tinned-copper. That is a solid copper conductor with a very thin, tin coating. There’s still a lot of this type & era cable in service. Except for the fact that the insulating materials on the wires can become brittle and break, it’s not an issue like KnT and the aluminum (Next topic). If there are indications of the insulating materials deteriorating, a licensed electrician must evaluate and repair.
Around the early 1960s more common Non Metallic (NM) cables were used. Key among this era of cables is that all** the conductors were copper. These are still available and the predominant type of electrical cables used. One brand name is ROMEX and the entire category of NM cables are often generically referred to as, “Romex”. We also see some metal, armor jacketed cables commonly called, “BX”. BX is still available today and commonly used. Some jurisdictions, such as New York City/Manhattan, still requires BX or metal, armor jacketed cables today. The NM and BX cables described in this paragraph are STILL the state of the art. **However, there was a brief period when The Great Garden State allowed solid aluminum conductors in NM cables. From what I’ve been told, toward the end of the Vietnam War some jurisdictions (Including NJ) allowed solid conductor aluminum to be used. From about 1967 through about 1974 it was an option for builders and electricians. My home, built in 1972, had nearly all solid conductor aluminum wire when we moved into it in 1991. If you’re planning to purchase a home build 1967 – 1974, make sure to select an inspector that is aware of the use of aluminum in that era. For a few reasons, aluminum was known to cause fires. Insurance companies don’t like it and it’s expensive to replace. A technique called, “Pig-tailing” is often used to mitigate the issues with aluminum. For my home, I decided to replace it all with solid copper, BX cable which is superior to the electrical code for NJ. There is a little, modern, copper, NM cable but the vast majority is copper conductor, BX.