Knob and Tube Wiring During a Home Renovation: What Toronto Homeowners Need to Know
- 416 Construction
- Aug 9
- 3 min read
What Happens If Knob and Tube Wiring Is Found During a Renovation?
If knob and tube wiring is discovered during a Toronto home renovation, stop before covering the area and have the system inspected by a Licensed Electrical Contractor.
The Electrical Safety Authority states that existing knob and tube wiring may remain in service when it is properly maintained. However, an electrical contractor may recommend replacement if the wiring is damaged, deteriorated, improperly modified or unsuitable for the planned renovation. (Esa Safe)
A renovation is often the most practical time to replace old wiring because walls and ceilings may already be open.
Knob and Tube Wiring Questions and Answers
What is knob and tube wiring?
Knob and tube is an older wiring method commonly found in homes constructed from the early 1900s through approximately the 1940s. Individual wires were supported by porcelain knobs and protected by porcelain tubes where they passed through framing.
It does not provide all the safety features available in modern electrical systems, including modern grounding and protection for certain wet or high-risk locations. (Esa Safe)
Does knob and tube wiring have to be replaced during a renovation?
Not automatically.
Ontario’s electrical rules are not generally retroactive simply because an older wiring method exists. However, wiring affected by the renovation must be evaluated, and new electrical work must meet current requirements.
Replacement may be recommended when:
Wiring insulation is deteriorated or damaged
Previous alterations were completed incorrectly
Circuits are overloaded
Additional outlets, appliances or lighting are being added
Walls containing the wiring are being opened
An insurer requires replacement
The final decision should be based on an inspection by a Licensed Electrical Contractor.
Can you renovate a house that still has knob and tube wiring?
Yes, but the electrical system should be assessed during the planning stage.
The contractor must determine which circuits will be affected by demolition, structural changes, new kitchens, bathrooms, additions, finished basements or upgraded mechanical equipment. Leaving this assessment until construction begins can lead to unexpected costs and delays.
Is knob and tube wiring dangerous?
Knob and tube wiring is not automatically dangerous simply because it is old. The ESA states that it can remain safe when it has been properly maintained by a Licensed Electrical Contractor. (Esa Safe)
The concern is that older wiring may have deteriorated, been overloaded or been altered by unqualified individuals over many decades. A visual home inspection alone may not provide a complete electrical assessment.
Will home insurance cover a house with knob and tube wiring?
Insurance requirements vary by provider. Some insurers may refuse coverage, restrict coverage or require the wiring to be replaced before issuing or renewing a policy. (Esa Safe)
Homeowners should speak with their insurer before beginning the renovation and keep all electrical permits, inspection records and certificates.
Do you need an electrical permit to replace knob and tube wiring?
Most electrical installation, repair and replacement work must be reported to the Electrical Safety Authority through a Notification of Work, commonly called an electrical permit.
A municipal building permit and an ESA electrical notification are separate approvals, and a renovation may require both. Electrical installations may also need rough-in and final inspections before walls are closed. (Esa Safe)
Who is allowed to replace knob and tube wiring in Ontario?
When a homeowner hires someone to perform electrical work, the work must be completed through a Licensed Electrical Contractor.
Ask for the contractor’s ECRA/ESA licence number and confirm that the required ESA notification will be filed. A general handyman or an unlicensed subcontractor cannot legally perform electrical work for hire. (Esa Safe)
What document should you receive after the electrical work?
Once the work has been reviewed and accepted, request a copy of the ESA Certificate of Acceptance.
This document confirms that the electrical work has passed the applicable ESA review process and can be important for insurance, future resale and the homeowner’s records. (Esa Safe)
Plan Your Older-Home Renovation with 416 Construction
Renovating an older Toronto home requires more than choosing new finishes. Existing electrical systems, plumbing, structural framing and hidden conditions must be reviewed before the final construction budget is established.
416 Construction provides complete design-build coordination for older-home renovations, including architectural drawings, building permits, structural work and coordination with Licensed Electrical Contractors for electrical upgrades and ESA inspections.
Planning a renovation in Toronto or the GTA? Contact 416 Construction to assess the property, develop the scope and coordinate the renovation from design through construction.
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