Knob and Tube Wiring in Ontario: Is It Safe? What Homeowners Need to Know

Knob and tube (K&T) wiring was the standard electrical wiring method in Ontario homes built before 1950. It uses ceramic knobs screwed into joists to support individual wires, and ceramic tubes to protect wires where they pass through wood framing.

Unlike modern wiring which bundles hot, neutral, and ground wires together in a single cable, knob and tube runs each wire separately with air space between them. There is no ground wire. The insulation is a rubber or cloth material that was not designed to last 75 or more years.

If your home was built before 1950 and has never been fully rewired, there is a high probability that some or all of the original K&T wiring is still active.

When it was new and properly maintained, knob and tube wiring was safe for the electrical demands of the era. The problem is that era had very different electrical demands than today.

K&T wiring was designed for lighting and a few small appliances. It was never meant to power air conditioners, microwaves, computers, multiple TVs, and all the other devices in a modern home. Running modern loads through K&T wiring causes overheating.

The insulation is the bigger concern. After 70 to 100 years, the rubber and cloth insulation on K&T wiring becomes brittle, cracks, and falls off. Bare wire touching wood framing is a fire waiting to happen.

Additionally, homeowners or previous contractors may have improperly added to or modified the original K&T system over the decades. Spliced connections, improper insulation contact, and overloaded circuits are common findings when we inspect older homes.

This is often what forces the conversation. Most Ontario insurance companies now treat knob and tube wiring as a significant risk factor. Here is what you may encounter.

Some insurers refuse to write new policies for homes with active K&T wiring. Others will insure the home but at significantly higher premiums, sometimes 50% or more above standard rates. Some will issue a policy with a condition that K&T wiring must be replaced within 30 to 90 days.

If you are buying a home with K&T wiring, your home inspector will flag it. Your mortgage lender may require proof of insurability before closing. And your insurer may require a full rewiring before they will issue coverage.

If you currently have insurance on a home with K&T wiring, do not assume you are covered forever. Policy renewals can trigger new inspections and new requirements.

Not all knob and tube wiring needs to be replaced immediately. Some K&T systems are in better condition than others. Here is how we assess it.

The wiring must be replaced if the insulation is visibly cracked, brittle, or missing. It must be replaced if K&T wiring is in contact with building insulation (blown-in insulation covering K&T wire is a fire hazard). It must be replaced if circuits are overloaded or have been improperly modified.

Replacement may be deferrable if the K&T wiring is in good condition, properly supported, and not in contact with insulation. Some homes have partial K&T where only certain circuits are still on the old system. In these cases, replacing just the active K&T sections is often sufficient.

The only way to know for certain is a professional inspection. We trace all K&T circuits throughout the home, assess the condition of the insulation, check for improper modifications, and provide an honest recommendation.

The cost of knob and tube replacement in Ontario depends on how much K&T wiring is active and how accessible it is. Here are typical ranges.

Partial replacement (a few circuits) costs $3,000 to $6,000. A full bungalow rewire runs $5,000 to $8,000. A two-storey home full rewire costs $8,000 to $15,000.

These prices include the new NMD90 copper wiring with proper grounding, the ESA permit and inspection, and the ESA certificate your insurance company needs.

Drywall patching is sometimes needed and is typically not included in the electrical quote. We minimize wall openings wherever possible and coordinate with drywall contractors when needed.

The cost of not replacing K&T wiring can be far higher. A house fire, denied insurance claim, or failed home sale all cost more than the rewiring itself.

All knob and tube replacement work in Ontario must be performed by an ESA-licensed electrician. An ESA permit is required before work begins, and an ESA inspection must be completed after the work is done.

The ESA inspector verifies that all old K&T wiring has been properly disconnected or removed, that the new wiring meets current Ontario Electrical Safety Code, that all connections are properly made, and that the new circuits are correctly protected by appropriately sized breakers.

After passing inspection, you receive an ESA certificate. This certificate is what your insurance company needs to update your policy and, in many cases, lower your premium.

Call Superior Power Electric at (647) 872-9954 to book a $49 knob and tube assessment at your Brampton home. The fee is credited toward your project if you proceed. We will inspect the wiring, tell you what needs replacing, and give you a written quote. ESA License #7014710.

We also handle complete home rewiring and aluminum wiring remediation.