Job at an old school house turned into a nightmare when we found knob and tube wiring

I was running new hardwired smokes in a 1920s school conversion last Tuesday and the whole ceiling had hidden knob and tube still live behind the plaster. Has anyone else run into surprise old wiring like this and what did you do about the fire risk?

2 comments

2 Comments

stella_lee17d ago

Knob and tube is actually fine if it's in good shape and not damaged. The real problem is people burying it in insulation or covering it with loose debris. That stuff gets hot under load, and without proper airflow it becomes a fire hazard. You're right to be worried, but the fix isn't always a full rewire. What you need is an electrician who knows old work. They can check the insulation condition, the splices, and whether anything's been spliced into modern wire wrong. If the K&T is intact and not overloaded, it's often safe to leave it in place. Just make sure it's not buried and the connections are tight. Honestly, the bigger danger is people who see old wire and panic. They rip it out and patch it poorly, or they tie modern fixtures into circuits that can't handle them. You're smart to ask first.

perez.christopher16d ago

Gotta agree with @stella_lee - I've seen guys rip out knob and tube just to replace it with wiring that's somehow worse, which is saying something coming from a guy who once shocked himself trying to change a lightbulb.