My home was built in 1932 and I have knob and tube wiring in my walls. Is this safe?
Many homes built in the before World War II had a type of wiring known as “knob and tube” originally installed. This practice has been discontinued, and modern building codes specify wires plastic, PVC or metal sheathing where both positive and negative wires, as well as a ground wire, and individually isolated and insulated.
Knob and tube wiring offers no such insulation – a positive and a negative wire are individually sheathed in cloth, and run together around ceramic “knobs” where a turn is required and for support, and through “tubes” where it is necessary to transport wiring through studs. The positive and negative wires were generally not next to each other in walls, but instead isolated on either side of a beam or stud.
Over time, the cloth insulation deteriorates, and the bare wire may be exposed. This becomes a potential fire hazard generally if there is some sort of change in the house – walls moved or other renovation work, for example, that brings exposed wire into contact with another wire or the house itself.
As a result, most insurance companies will not insure homes with known knob and tube wiring in use.