Skip to main content

Understanding Knob & Tube


Arshad Khan, Certified Home Inspector - Qualityspec Inc.
Knob & Tube wiring is a type of wiring which was in common use until the 1940's. More than 1.5 million homes across Canada were built with knob and tube wiring. It was an early form of electrical wiring that was used up to 1945. So, many homes still have it but is now considered too risky and dangerous to be insurable, and for your own safety, and home resale value it should be replaced with copper wiring. Knob & tube wiring is comprised of insulated wires clamped on two-piece porcelain knobs; positive and negative are carried separately. Hollow porcelain tubes carry the wires, through beams and other combustible materials. Modern electrical codes do not permit this type of wiring. It can present a hazard if tampered with, particularly at unenclosed, soldered-and-taped junctions. The unsheathed insulation is subject to deterioration, particularly where it is exposed, that is, not enclosed in a wall or ceiling. Worn insulation, of course, presents a shock hazard The ESA's (Electrical Safety Authority) recommendation to insurance companies on knob and tube wiring is that they ask for inspections to make sure the wiring is safe. It does not recommend denying someone insurance simply because they have some knob and tube wiring, although individual insurance firms can refuse coverage for homes with knob and tube wiring as they see fit.

(This is an electrical panel using Knob and Tube wiring as well as fuses. The incoming service wires are knob and tube connected directly to the utility service wires that continue directly to the Meter. All circuit wires to lights, plugs, and switches in this home were still using the original Knob and Tube Wires)

What You Can Do
The first thing to determine is the safety of your system. 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 various upgrade options but don't attempt an upgrade yourself.

Comments

Popular posts from this blog

Holiday Travel Tips for Your Home

The festive holidays are approaching, and calendars are already filling up. Whether you’re staying with family around the country or taking an extended leave to escape the winter, you may be planning to leave your home vacant for more than a day or two. To ward against coming home to the wrong kind of holiday surprise, here’s what to do before you depart. Cheap Wi-Fi cameras Security equipment might sound high-tech and expensive, but securing your home against potential intrusion doesn’t cost much. For around $30, you should be able to outfit your home with WIFI cameras which are home assistant compatible. Shut the main water off Remember to shut off the main water supply if you plan to be away from your home for more than a day. In the event of a plumbing failure, your home could fall prey to serious water damage. Install smart water sensors in your basement Installing a smart water sensor in your basement can easily save a lot of money and worry. Some models will alert you to leaks a...

GTA REALTORS Release March 2025 Stats

Homeownership in the Greater Toronto Area (GTA) became more affordable in March 2025 compared to the previous year. On average, both borrowing costs and home prices have declined over the past year, making monthly payments more manageable for households looking to buy a home. “Homeownership has become more affordable over the past 12 months, and we expect further rate cuts this spring. Buyers will also benefit from increased choice, giving them greater negotiating power. Once consumers feel confident in the economy and their job security, home buying activity should improve,” said Toronto Regional Real Estate Board (TRREB) President Elechia Barry-Sproule. “Given the current trade uncertainty and the upcoming federal election, many households are likely taking a wait-and-see approach to home buying. If trade issues are solved or public policy choices help mitigate the impact of tariffs, home sales will likely increase. Home buyers need to feel their employment situation is solid before ...

TRREB MLS® SALES MARCH 2025