The insurance inspector wasn’t smiling as he came up from the basement of the 90-year old brick home you just bought, but it didn’t mean much until he started to talk. “I’m sorry”, the guy said, not looking particularly sorry at all, “we can’t extend a homeowner policy to you. There’s knob and tube wiring in this place and you’ll need to upgrade the entire electrical system before we can offer you insurance coverage.”

This is the stuff of nightmares for a growing number of people moving into older homes, and it’s even affecting people with existing insurance policies up for renewal. As knob and tube wiring (also called ‘open wiring’) becomes more of a technical issue, understanding the nuts and bolts of the technology and the solutions is essential for owners of older homes. Like most things in life, a little insight goes a long way.

‘Knob and Tube’ Electrical System

‘Knob and tube’ is a generic term that describes a system of residential wiring installed between 1900 and the 1940s in both city and country homes across Canada. It was leading edge technology at the time, but is now regarded as too risky and dangerous to be insurable by some companies. Understanding knob and tube wiring can help you weigh your options and make the best possible decisions, both before you buy or after you’ve found out you’ve got knobs and tubes in your home.

  • Knob and tube wiring was used at a time when the electrical industry hadn’t yet developed the kind of highly effective, synthetic wire insulation materials we have now.
  • While modern electrical cables are actually bundles of wires separated by layers of flexible plastic, older knob and tube conductors are usually single wires covered in a cloth-based sheath.
  • These conductors run separately, in parallel pairs, supported by porcelain tubes and knobs where they travel through and over wooden framing members.
  • The marginal nature of the old insulation meant that conductors needed to be separated physically to prevent them from shorting out, and it’s this unique feature that makes knob and tube systems easy to identify.

Is ‘Knob and Tube’ Wiring Safe?

Although wiring practices have advanced a lot since knob and tube was cutting-edge, existing systems are still permitted to remain in place and operational for lighting and wall outlets if they meet the following conditions as laid out by the Electrical Safety Authority (ESA):

  • Circuits must be protected by a 15 amp fuse or circuit breaker
  • No additional outlets can be added to the original installation
  • Exposed conductors must be in good physical condition

Although this is good news, it doesn’t necessarily mean you’re eligible for insurance coverage from every company in the business. In fact, individual insurance firms can and do refuse coverage for homes with knob and tube wiring as they see fit. And the reasons cited certainly have some merit.

Knob and tube systems were designed to supply much lighter electrical loads than we consider essential today. They’re usually part of electrical services rated to provide just 60 amps of total current in a home. When you realize that simply toasting a couple of slices of bread while heating a kettle of water in the morning demands almost 25% of this capacity, it’s obvious how easy it is to overload old electrical systems.

Another area of concern is the fact that knob and tube wiring systems aren’t grounded. Even if they’re in perfect working order, these old circuits don’t include the kind of third circuit wire that’s now a code requirement for new electrical installations. All else being equal, grounded circuits are safer than non-grounded ones because they dramatically reduce the shock hazard if appliances malfunction.

What you can do if you have ‘Knob and Tube’ Wiring

The first thing to determine is the safety of your system. Opinions offered by inspectors certified by the Electrical Safety Authority are generally accepted by those insurance companies willing to cover safe knob and tube installations in certain situations.

Even if your system is determined safe, consider upgrading at least parts of it. The areas of a knob and tube installation that are most vulnerable to mechanical damage and trouble are also those areas that are exposed and easiest to change. An electrician can advise you on the feasibility of various upgrade options. Don’t attempt an upgrade yourself.

If your existing knob and tube system is certified safe, and you’d like to seek coverage for your home as it is, then call the Insurance Bureau of Canada. This nonprofit industry association is staffed to help you explore coverage solutions for knob and tube-equipped homes, and that’s good news for everyone who’s heard bad news lately from a stranger walking up the basement stairs.

So as it turns out, if you’re one of the thousands of homeowners living with this kind of electrical hardware, you’ve got more options than just losing sleep over the way your house is wired.

Is your home’s wiring up to snuff? Connect with Verified by eRenovate™ Electrical Contractors by using the eRenovate Post My Project tool or the eRenovate App.

Steve Maxwell is Canada’s Handiest Man. An award-winning home improvement authority and woodworking expert, he’s truly a treasure of home wisdom and the ultimate home GURU. Be sure to visit his site at

Steve Maxwell

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