Piece of History: Knob & Tube
It’s been a while since I did a Piece of History post, mainly because we’ve done most of our tear-out and there’s not much left to find at this point. However, as we complete the electrical work, it seems fitting to talk about the wiring system we removed.
I honestly had no idea what the little white porcelain knobs in the walls were when I first saw them. It seemed like every wall or ceiling cavity we opened had them running along the studs or on the joists. As it turns out, we were looking at the original wiring system for this house. Knob and tube wiring was the standard method of wiring a house between the 1880s and the 1930s. The “knob” in knob and tube provides support to each wire, anchoring it in place at each stud. Not shown in the photo above is the other half: the tube. Ceramic tubes were inserted into holes drilled into the studs or joists and the wires run through the middle of them.
The product of this wiring method is a matrix-like network of wires running along the ceilings and walls. From what I can gather, this was necessary as a precaution against two wires being too close together. Wire insulation back then wasn’t so great — if two wires touched, it could start a fire. Where the wires did have to get close to each other (outlets, light fixtures, etc), they were insulated with a cloth sleeve called a loom. And, of course, there were no grounds or anything of that sort. It’s a far cry from what electrical code is now.
I would say we’ve pulled out three or four dozen knobs and tubes so far (Update: photos added below!). I’m hoping we can sell them to someone restoring a historic house or building — we’ll see.