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Heritage homes and older properties are often revered for their character and charm, offering unique architectural designs and heirloom features homebuyers won’t get with a new build.

However, a few costly surprises can lurk behind the plaster walls and under the floorboards since these homes usually predate today’s building codes. You may find that the home’s plumbing, heating, and electrical systems need repair or replacement. And, while some renovations can wait, others may need to be addressed right away for insurance purposes. 

For instance, knob and tube wiring (K&T) can make it challenging to buy or renew a home insurance policy

What is knob and tube wiring? 

K&T is a wiring method that was popular before the 1950s. It used long black wires wrapped in rubberized cloth fed through ceramic tubes in the home’s joists, meeting at connection points — the knobs. While no longer installed today, many older homes still use this electrical system. 

How can you tell if a home has knob and tube wiring? 

In homes with unfinished basements, looking at the ceiling should indicate the wiring, as it is often left exposed. Some other indicators will be antique light switches on the walls and the lack of three-pronged outlets. 

It can be trickier to tell if a home has K&T, particularly if it has undergone some upgrades. Either way, having an electrical inspector come to the house is the best course of action. 

Is knob and tube wiring dangerous?

K&T doesn’t age well — it’s around 70 to 100 years old, after all. Here are some of the issues that can arise:

  • Wire damage. Often, the rubber coating cracks, exposing wires and becoming a fire risk.
  • Circuit overload. The electrical system wasn’t designed for today’s demand and modern appliances. Many modern devices, like fridges and even computers, have three-pronged plugs which are unsuited to the older two-pronged outlets.
  • Improper modifications. Using extension cords or modifying the K&T can be hazardous.
  • Power surges. K&T has no grounding wire, so nothing protects the outlets and your appliances from sparking. 

According to the Electrical Safety Authority (ESA), the regulatory body in Ontario, K&T is permitted if protected by a 15 A fuse or circuit breaker, no additional outlets have been added to the original installation, and the conductors appear to be in good condition. 

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How much does it cost to replace knob and tube wiring? 

The replacement cost will depend on the home’s size, location, and scope of the work. To replace K&T, it could cost as little as a few thousand dollars to upwards of $25,000

Replacing K&T would likely mean more upfront costs for homebuyers, so it is crucial to understand any added expenses you could incur when buying an older home. 

While it may cost a lot to replace K&T, doing so has benefits. Modern electrical installations have more safety features than those from a century ago. Some of the benefits of new wiring include grounded receptacles for surge protection, greater electrical capacity, and cheaper home insurance rates.

A licensed electrician should make any modifications to ensure the wiring is safe and to code. 

Will I be able to get insurance if my home has knob and tube wiring? 

According to the Insurance Bureau of Canada (IBC), some insurance providers won’t insure properties with K&T; however, others may allow homeowners time for remediation. The timeline to have the K&T replaced will depend on the insurance provider. 

Replacing K&T is not mandatory, however. Some insurance providers will offer home insurance for properties with K&T but may require an electrical inspection. In Ontario, homeowners can arrange an inspection through the ESA. If the inspection finds that the wiring doesn’t comply with today’s standards, you must correct the issues. 

Since insurance providers see K&T as a higher risk, insuring a home with older wiring can be costly. It’s important to compare home insurance quotes to ensure you get the best rate. is a free and independent rate comparison website that allows Canadians to compare rates from 75+ providers for various financial products, such as home and auto insurance, mortgages, and credit cards.

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