Kai Mallari's Notes'

Knob-and-Tube Wiring Is an Insurance Refusal Trigger in BC (Home Systems)

5 min read

Knob-and-Tube Wiring Is an Insurance Refusal Trigger in BC

idea

Claim: Knob-and-tube wiring (used in Canadian homes roughly pre-1950) triggers insurance refusal or heavy surcharge from most BC insurers, not primarily because the wiring fails on its own terms, but because its insulation has deteriorated after 70+ years and the system cannot safely carry modern electrical loads. Most BC insurers will not issue a new policy on a home with active knob-and-tube, or they require full replacement within 12–24 months as a condition of coverage.

Mechanism

Knob-and-tube wiring uses individual copper conductors (no ground wire) routed through ceramic knobs fastened to framing members and through ceramic tubes where wire passes through framing. The insulation is rubber and cloth fabric, not the modern thermoplastic (THHN/THWN) that is stable for 30+ years.

After 70 or more years, this insulation becomes brittle, cracks, and in many cases has partially or fully fallen away from the conductor. Exposed live conductors in proximity to wood framing, cellulose insulation, and other building materials create direct ignition opportunities when the circuit carries load.1

Three compounding hazards:

  • No ground wire: knob-and-tube has only a hot and a neutral — no equipment ground. Ungrounded circuits cannot provide shock protection for 3-prong appliances or be protected by certain GFCI configurations. Damp environments (bathroom, kitchen, laundry) are particularly hazardous.2
  • Thermal insulation incompatibility: the insulation on knob-and-tube was designed to dissipate heat freely in open air. When modern blown-in or batt insulation is added to walls and attics of older homes (as an energy upgrade), it traps heat around the conductors, raising operating temperature and accelerating insulation failure. Blown-in insulation packed around knob-and-tube is a documented fire cause.1
  • Undersized for modern loads: knob-and-tube systems were sized for the 30–60 amp services typical of early 20th-century homes. Modern households draw 3–5× the load that was assumed when the circuits were sized. Running modern appliances on these circuits overloads them.2

Insurance reality in BC

Most BC insurers will not write a new home insurance policy on a property with active knob-and-tube wiring. For homes where coverage exists (usually inherited policies):

  • Insurers commonly impose premium surcharges of 30–50% over a comparable modern-wired home.3
  • Many require documented full replacement within 12–24 months as a condition of policy renewal.
  • Some will insure only if a licensed electrician provides a letter certifying the system is in good condition — but this does not resolve the underlying load and insulation risks.

Non-disclosure risk: failure to disclose knob-and-tube at application or renewal gives the insurer grounds to deny a fire claim. In a strata, a denied claim still exposes the owner to the strata’s deductible chargeback under SPA s.158 if the fire spreads to common property or a neighbouring unit.

What counts as “addressed”

The insurance standard in BC requires one of:

  • Full replacement of knob-and-tube with modern copper wiring, plus a Technical Safety BC permit and passed inspection. This is the standard most BC insurers require.3
  • De-energizing (removing the circuit from the panel and capping the conductors) is sometimes accepted by insurers as an interim measure for portions of the system that have been replaced — confirm with your specific insurer in writing before relying on this.
  • Licensed electrician certification in good condition — accepted by some insurers, but fewer than before. The certification does not remove the thermal insulation and load risks.

Scope

  • Covers knob-and-tube branch-circuit wiring in homes built roughly pre-1950 (some systems installed into the early 1960s).
  • Does NOT cover aluminum wiring (1965–1976 hazard, different mechanism) — see Aluminum Wiring Overheats at Connections — Not In the Wire Run (Home Systems).
  • Does NOT address whether a specific home has knob-and-tube — that requires a licensed electrician inspection.

Sources

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Footnotes

  1. WireChief Electric, Metro Vancouver electrician — knob-and-tube wiring: insurance, risks, and what homeowners need to do; thermal insulation incompatibility noted — https://www.wirechiefelectric.com/knob-tube-wiring-homeowner-insurance ↩ ↩2

  2. ThinkInsure, Canadian insurance information — knob-and-tube wiring: lack of ground, insulation deterioration, load incompatibility, insurance challenges — https://www.thinkinsure.ca/insurance-help-centre/knob-and-tube-wiring.html ↩ ↩2

  3. Vancouver General Contractors — knob-and-tube replacement in Vancouver 2025: BC insurer surcharges 30–50%; most insurers require replacement; costs 35,000 depending on home size — https://vancouvergeneralcontractors.com/knob-tube-wiring-vancouver/ ↩ ↩2

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