TL;DR
Knob-and-tube wiring is the early electrical method, common from the 1880s through the 1940s, that runs separate hot and neutral conductors on ceramic knobs and through ceramic tubes in framing, with no grounding conductor and rubber insulation that embrittles with age. Intact and unmodified, it can still function, but buried splices, overfusing, and burial under attic insulation, which the NEC prohibits because the wires need air cooling, create real hazards.
What it means
Knob-and-tube wiring is the early electrical method, common from the 1880s through the 1940s, that runs separate hot and neutral conductors on ceramic knobs and through ceramic tubes in framing, with no grounding conductor and rubber insulation that embrittles with age. Intact and unmodified, it can still function, but buried splices, overfusing, and burial under attic insulation, which the NEC prohibits because the wires need air cooling, create real hazards. Many insurers surcharge or decline homes with it energized, making evaluation and replacement a frequent rewire driver.
Where it sits in the glossary
Knob-and-tube wiring is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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