Homes built in different eras often reveal their age the moment an electrician opens a wall or panel. Wiring methods have changed substantially over the last century, and knowing roughly when a system dates from helps explain what kind of work it may need.
Common in homes built before the 1940s, knob-and-tube wiring ran individual conductors through porcelain knobs and tubes rather than a sheathed cable. It lacks a ground wire, and insulation on very old runs can become brittle over time. Both are reasons many insurers and electricians recommend evaluation or replacement in homes that still have it.
Used in a portion of homes built roughly from the mid-1960s to mid-1970s during a copper price spike, aluminum wiring requires specific connectors and techniques to remain safe at outlets and switches, a detail worth confirming if you own a home from that era.
Today's standard residential wiring uses copper conductors in non-metallic (NM) sheathed cable, paired with grounding requirements, GFCI and AFCI protection in specific areas, and periodic code updates reflecting new appliance and safety needs. If you're unsure what's behind your walls, our repair team can inspect it during a service call.
Further reading: Knob-and-tube wiring (Wikipedia)