Okay it wasn’t a strong shock, but non the less it was odd. I was feeling a water damaged plaster ceiling, trying to figure out why the ceiling was corroding and rusted. Upon entering the attic I saw some knob and tube coming out of blown in cellulose insulation. The ceiling was damaged from poor flashing around a chimney and therefore water was dripping from the chimney flashing onto the insulation and therefore onto the ceiling below the insulation. Would I be correct to assume that the knob and tube is likely in contact with either the “wet” insulation/ plaster ceiling, therefore energizing the ceiling? What would cause the plaster to rust like this? This house is probably about 100 years old.
could be metal lathe at the corners…
Knob and tube should not be in contact with combustibles. That is why it was isolated with ceramic insulators. It should be called out as a fire hazard.
Rust may be from steel flashing? Sometimes the cellulose darkens water. It may not be rust.
Knob and tube must not be buried in insulation. Period.
Nails used to secure lath would be likely source of rust.
It’s probably not just rust, but a combination of deposits picked up by the water as it passed over the brick, mortar, flashing, roofing, old darkened framing, fasteners, lathe and plaster.
As far as the shock is concerned, were you standing on something to reach the ceiling or was it low enough touch? You’re probably correct, with old and wet knob and tube there are plenty of scenarios where you could have been in parallel with a circuit and gotten a mild shock. Glad you are still here to tell the story.
Thanks for all the input. FYI I did call it out as a safety concern. Next time I’ll pull out the old non contact voltage tester before I touch something water damaged…
Wow, I’ve never considered this as a shock hazard but will definitely think twice next time! Thanks for sharing!
Anytime I see knob/tube, my electrical inspection is over. Recommend replacement, etc…