Knob and tube wiring in Ontario pre-1940s homes creates real insurance, safety, and sale complications. Here is what homeowners need to know.
What Is Knob and Tube?
Individual copper conductors in cloth or rubber insulation, run through ceramic insulators in framing. No ground wire, no sheathing, no modern circuit protection features. Found in Ontario homes built from approximately 1880 to the late 1940s.
Safety Concerns
No grounding: risk for modern appliances and electronics. Aged cloth insulation becomes brittle and cracks. Decades of DIY modifications may have overloaded circuits or bypassed junction boxes. Attic insulation blown over K&T is a fire hazard — K&T requires air circulation to dissipate heat.
Ontario Insurance Reality
Many Ontario insurers now refuse to bind or renew policies on homes with active K&T wiring. This is the most common driver of replacement in Ontario. ESA Certificate of Inspection after rewire typically satisfies insurer requirements.
Replacement Costs 2026
Partial update (panel + priority circuits): $5,000-$12,000. Full rewire: $12,000-$30,000+ depending on home size and access. Permit and ESA inspection required for all electrical work.
Discuss K&T replacement and find licensed Ontario electricians at home.renovation.reviews.