An outdated electrical system common in homes built before 1950, using ceramic knobs and tubes to run individual wires through wall cavities and floor joists. Unlike modern wiring, it has no ground wire, cannot safely handle modern electrical loads, and becomes a fire hazard when insulation is added around it or when the rubber wire coating deteriorates with age.
Why It Matters
Knob and tube wiring is a dealbreaker for many insurance companies -- some will not issue a policy until it is fully replaced, which can cost $8,000 to $15,000 or more for a typical GTA house. If you are buying an older home, budget for a full rewire. Even if only a portion of the original wiring remains active, most insurers want the entire system replaced before they will cover you.
Real-World Example
You find a charming 1920s detached home in The Junction listed at $899,000. The home inspection reveals active knob-and-tube wiring throughout the second floor and attic. You contact three insurance companies, and two refuse to provide coverage until the wiring is fully replaced. A licensed electrician quotes $12,000 to rewire the affected areas and bring the electrical panel up to current code. You negotiate a $15,000 price reduction from the seller to cover the rewiring cost plus a buffer for any hidden issues discovered during the work.
Ontario & GTA Context
In Ontario, knob-and-tube wiring is most commonly found in homes built before 1950, which are concentrated in older Toronto neighbourhoods like The Annex, Roncesvalles, High Park, Cabbagetown, and Riverdale. The Electrical Safety Authority (ESA) does not require removal of existing knob-and-tube wiring, but any new electrical work must meet current Ontario Electrical Safety Code standards. Most Ontario insurance companies will not insure a home with active knob-and-tube wiring, or will charge significantly higher premiums.
How It Works in Practice
During your home inspection, ask the inspector specifically about knob-and-tube wiring -- it can be hidden behind finished walls and may not be immediately visible. Get insurance quotes before removing conditions on your offer, since inability to obtain insurance at a reasonable cost could make the purchase impractical. Budget for a full rewire, even if only some knob-and-tube is currently active.
Common Questions
Can I get home insurance with knob-and-tube wiring in Ontario?▾
How much does it cost to replace knob-and-tube wiring in the GTA?▾
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