Knob-And-Tube Wiring: Is Your Old Home Safe or Is It Time to Upgrade?

9 March, 2026 Hi-Lite Electric Inc.

If you own a home built before the 1950s, there’s a good chance you’ve heard of knob-and-tube wiring. This once-standard electrical system helped power homes throughout Ontario for decades, but it was never designed for the demands of modern living. Today, knob-and-tube wiring poses several safety concerns, often making it a liability when it comes to insurance, home resale, and electrical reliability.

Many homeowners don’t realize they still have active knob-and-tube wiring in parts of their house. Whether it’s tucked behind plaster walls or hiding in the attic, outdated wiring can create a false sense of security until something goes wrong. If you’re living in or buying an older home, here’s what you need to know.

The Hidden Dangers of Knob-and-Tube Wiring in Older Homes

Knob-and-tube wiring was common from the 1880s through the 1940s. It uses ceramic knobs to guide wires through framing and ceramic tubes to protect wires where they pass through wood. While it was innovative for its time, it lacks one major modern safety feature: grounding.

Without a ground wire, these systems can’t safely redirect electrical faults, increasing the risk of fire or shock. Add to that decades-old insulation, and you’ve got a system that’s increasingly brittle and prone to failure. As a result, most insurance providers consider knob-and-tube wiring a high-risk liability.

The reality is, even if your home’s knob-and-tube wiring has never caused an issue, it’s still considered outdated and unsafe by today’s standards. It’s not a matter of if something will go wrong, but when. The longer the system remains in place, the greater the likelihood of an electrical failure, especially as more demands are placed on your home’s infrastructure.

1. Overheating and Fire Hazards

One of the most serious risks of knob-and-tube wiring is its potential to overheat. The insulation used during the early 20th century deteriorates over time, especially in warm attics or areas with moisture. Once that protective coating breaks down, exposed wires can arc, spark, or ignite surrounding materials.

Since these systems were never designed for today’s energy loads, plugging in a high-demand appliance, like an air conditioner or microwave, can quickly overwhelm the circuit. And without a ground wire, there’s no built-in safety mechanism to prevent a fire.

2. Risk of DIY Modifications

Knob-and-tube wiring may have worked safely when installed by skilled electricians 80 years ago, but over time, many systems have been tampered with. Homeowners or handymen often spliced modern wiring into existing circuits without proper grounding, fuses, or junction boxes.

These DIY fixes are usually invisible behind walls or ceilings and may not be caught during a standard home inspection. But they increase the risk of overloaded circuits, reversed polarity, or worse.

If your home has gone through multiple renovations, it’s likely that some of the wiring has been altered in ways that may not meet today’s safety codes. That’s why it’s important to have a professional electrician evaluate the entire system, especially if you notice flickering lights, frequent blown fuses, or outlets that feel warm to the touch.

3. Limited Capacity for Modern Living

Knob-and-tube systems were built in an era of toasters and table lamps, not flat screens, gaming consoles, and electric vehicles. These old circuits simply weren’t made to handle the electrical demand of a 21st-century home.

Running multiple high-powered devices on the same circuit can lead to tripped breakers, overheating, or even permanent damage to sensitive electronics. And because these systems weren’t designed to distribute power evenly throughout a home, you may experience dimming lights or inconsistent performance in different rooms.

4. Insurance and Home Sale Complications

Insurers in Ontario are increasingly unwilling to underwrite properties with active knob-and-tube wiring. Some may refuse coverage altogether, while others will only issue policies if a complete rewiring is completed within a set timeframe.

For homeowners looking to sell or refinance, this can be a major roadblock. Buyers may be hesitant to purchase a home with outdated wiring, or mortgage lenders may require proof of updated electrical systems before approving a loan. In either case, old wiring can dramatically reduce a property’s value and marketability.

Upgrade Your Home’s Wiring with Expert Help

If you suspect your home has knob-and-tube wiring, or if you’ve been told by an inspector or insurance agent, it’s time to act. The safest route is to have a licensed electrician perform a full electrical assessment. They can determine where the wiring exists, evaluate its condition, and recommend the most effective plan for a full or partial upgrade.

At Hi-Lite Electric, we specialize in rewiring older homes across the GTA. Our team understands the unique challenges that come with heritage properties, from plaster walls to limited attic access. We provide detailed assessments, safe removals, and updated wiring systems that meet today’s electrical code.

Upgrading your wiring improves safety, increases home value, and ensures that you can run modern appliances without risk. It also gives you peace of mind, knowing your family is protected from preventable hazards hiding behind your walls.

Don’t Wait Until There’s a Problem

Too often, knob-and-tube wiring is only discovered after an issue: a power outage, a failed home inspection, or worse, an electrical fire. By taking proactive steps now, you can avoid costly emergency repairs, insurance issues, and risks to your safety.

Modern electrical systems offer better performance, greater efficiency, and most importantly, vastly improved safety standards. If your home was built before 1950 and hasn’t had a full electrical update, now’s the time to make the change.

Reach out to Hi-Lite Electric today at (416) 223-9655, email us at info@hi-liteelectricinc.ca or click here to schedule your safety inspection.