What Is It?
The old wiring system, that was used up into around 1950 , depending on what area you are in, is what is known as “ knob and tube “ wiring.Where the “ tube “ is a ceramic tube, that was installed in the holes that where drilled in the wood, that would act as a protection, when the wire was pulled through it. The “ knob “ was a ceramic knob, with 2 parts, ( sometimes known as “ split knob and tube “ ), the wire would be secured inside the split knob, and then a nail or screw installed to hold it in place. The wire was a single conductor , with a type of Fabric insulation. They had mainly white, ( neutral ), and black, ( hot ) colours, i have seen it in red also. If for example, when they ran it in the attic, they would secure it, one line on each side of a joist space, facing each other, if the joists were @ 16” centres, then you had that extra “ insulation” between the 2 wires.
Usually there were no boxes used in the attic part of the system, one line would be wrapped around another line, or they would make a junction point, and twist a few together ,and then solder them, and then wrap with fabric tape. The outlet boxes, and switches, would have a metal box, most times screwed on the “Lath and Plaster “ finish, or the outlets would be mounted, sideways , right into the large molding, at the base of the floor. The Lights in the ceiling, usually had a “ header “ piece of wood mounted between 2 of the joists, and the 2 holes drilled in the wood, the wires would pass through the holes, with some extra wire protection, known as “ loom “.
Because this was just a 2 wire system, there was not a grounding system.
Why are insurance company’s saying i cant have, or have this wiring checked?
In all my experience re-wiring homes, it is always the same classic scenarios that pop up.
- The Knob and Tube has been tampered with, with someone maybe “ adding “ some more wiring, to power up extra lights / outlets etc. Because there was no junction boxes used in the attic, there was not a point to “ go into” the system. So most times, the wire insulation was just scrapped off, and the new wire wrapped around it. Sometimes i have at least seen some electrical tape wrapped around it, but rarely soldered, ( how many handyman even own a soldering gun )?
- When it was the Knob and tube era, there was not many appliances in the household, you had plug in lamps, Fridge, maybe a toaster, and then later a washing machine. So the houses did not have all the outlets / circuits installed like today. So what happens when there is no outlet in a room? Out comes the extension cords, and i have seen some very creative extension cord installations over the years! Most people have heard by now, this is not the best way to wire a house, especially using the cheap dollar store variety.
- Also when it was the knob and tube era, the Main Electrical Service to the house, usually was a 60 amp Service, because you did not have all these appliances like today.
- The Knob and tube wiring was not designed to be installed in insulated ceiling and walls, or be installed into recessed Lighting ( pot light ). Pot lights need a 90 C rating on the wire supplying them. I have been in attics, where it was so hot, (poorly vented ), there was hardly any insulation left on the old knob and tube wiring.
- With some simple research on the internet, i found out a house that old, may have had 5 to 8 renovations done to it, mainly Kitchens and Bathrooms topping the list. So what are the odds, that the knob and tube wiring has not been compromised in some way.