Knob and Tube Wiring in Ontario: What You Need to Know Before Renovating or Selling
If you own or manage an older home in Ontario—especially one built before the 1950s—there’s a good chance you’ve heard the term knob and tube wiring. Whether you’re planning a renovation, preparing to sell, or buying an older property, understanding what this type of wiring means for safety, insurance, and resale value is essential.
Let’s break down what it is, why it matters, and what you should do about it.
What Is Knob and Tube Wiring?
Knob and tube (K&T) wiring was a common electrical system used in Canadian homes from the early 1900s to the 1950s. It consists of:
At the time, it was considered a safe and practical way to distribute electricity. But electrical standards have come a long way since then—and K&T simply can’t keep up with today’s power demands or safety expectations.
Why It’s a Problem Today
Here’s why knob and tube wiring raises concerns:
Lack of Grounding
K&T systems have no ground wire, making them incompatible with modern three-prong outlets. This increases the risk of electric shock and limits what appliances you can safely use.
Increased Fire Risk
Over time, the wire’s insulation can become brittle or break down, especially when surrounded by modern insulation (which these systems were never designed for). DIY modifications, improper splices, and age-related wear add to the risk.
Not Designed for Modern Loads
When K&T was installed, homes didn’t have microwaves, hairdryers, home offices, or central air conditioning. Today’s electrical demands can overload these outdated systems.
Can You Still Live in a Home with Knob and Tube Wiring?
Technically, yes—but there are caveats. In Ontario, it’s not illegal to have K&T wiring if it’s in good condition and hasn’t been altered improperly. However, that’s a big if. And here’s where the real hurdles come in…
Insurance and Mortgage Issues
Many Ontario insurers refuse to cover homes with active knob and tube wiring. Those that do may require an inspection and charge higher premiums. You may even be denied a mortgage if the home hasn’t been updated.
If you’re buying, selling, or refinancing a home with K&T, expect questions—and potentially expensive conditions—from lenders and insurers.
How Replacing It Works
What’s Involved:
Removing and replacing knob and tube wiring is a major electrical upgrade. It usually includes:
How Long It Takes
Depending on the size of your home, a full K&T replacement typically takes 1 to 3 weeks, especially if walls and ceilings need patching afterward.
Permits, Inspections & Resale Value
In Ontario, replacing knob and tube wiring requires a permit and must be inspected by the Electrical Safety Authority (ESA). Hiring a licensed electrical contractor is not just recommended—it’s the law.
Why this matters for resale:
Should You Replace It Now?
If you’re planning to sell, renovate, or even just get better insurance coverage, the answer is yes. Upgrading your wiring may not be the flashiest improvement—but it’s one of the most important.
Trust G&S Electric to Do It Right
At G&S Electric, we’ve helped countless homeowners and property managers across London, ON and surrounding areas safely replace knob and tube wiring. Our licensed electricians will handle the process from permit to inspection—ensuring the job is done clean, code-compliant, and ready for resale.
Have knob and tube wiring? Let’s talk.
Schedule an appointment today or give us a call. We’ll walk you through your options and help future-proof your home the right way.
