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Knob and tube wiring in an old home

Is Your Knob and Tube or Aluminum Wiring Still Safe?

Home wiring hasn't always been the way it is today. In older homes, circa 1890 to 1940, the typical home wiring system was knob and tube wiring. Another vintage wiring system uses aluminum wires, which was common in houses in the 1960s and 1970s.

Although quite outdated, both are acceptable home wiring systems, according to the Electrical Safety Authority of Ontario (ESA). In this blog, you'll find the acceptability of both types of wiring, some of the issues you might encounter with them, and what electrical system upgrades exist. 

What is knob and tube wiring?

As the name suggests, it consists of ceramic knobs and tubes that secure the wiring throughout a home. Rubber or cloth insulation covers the copper wires.

Knob and tube wiring is allowed to stay in a home so long as:

  • it is protected by a 15-amp fuse or circuit breaker,
  • no additional outlets have been added to the original installation (to avoid a circuit overload), and
  • the visible conductors appear to be in good condition.

Electrical systems and appliances today use more power than a century ago, so problems typically occur when knob and tube circuits are overloaded. This means you may find yourself limited in power supply without the ability to add new outlets or additions to the existing system. Any additions would require a complete replacement of the home's electrical system.

Knob and Tube wiring

What is aluminum wiring?

You can guess this one quite easily. Rather than the more common copper in the wiring, it's aluminum. The ESA also approves the usage of aluminum wirings in homes. There are some shortfalls with this wiring system, though.

The wiring is perfectly functional, but problems can occur at the ends of the wires, also known as termination points. One problem is using incorrect devices (like light switches, outlets, fixtures etc.) with aluminum wiring. Only aluminum-rated devices are safe to use with this system. The device and wiring insulation can melt or burn if using a copper-rated device.

Another challenge with aluminum wiring is that exposed aluminum that connects to the device oxidizes over time. Oxidation may also melt or burn its wiring and connected devices. Fortunately, an "oxide inhibiting compound" can be applied to the termination points to mitigate the risk. Ensuring that the wiring is connected correctly to the proper devices is why it's always in your best interest to work with a licensed electrical contractor.

Can you keep original wiring?

The short answer is: it depends. If either form of wiring is in the home, so long as it meets the ESA standards, it is legally acceptable. What is the easiest way to find out if it is? Hiring a licensed electrical contractor to complete an electrical inspection would work!

The real issue is that insurance companies may deny you a policy, even if the wiring is in good shape. You may have to upgrade or remediate the wiring to obtain a new policy.

Something else to consider is what your future electrical needs might be. Will you renovate or add space, install an EV charger, or need more power? Depending on your appliances, they may need more power or updated outlets to function properly. If you need to upgrade wiring, consider the following options.

Home insurance policy

Wire upgrades and remediation

The only option for knob and tube wiring is a replacement. In this process, a team of electricians will replace wiring throughout the entire home. They will install an electrical breaker panel and, if needed, upgrade old outlets and switches. Finally, they will connect everything to give the house its new power system. Please be aware that this process may include some damage to walls, as it can be challenging to access hidden wiring

There are two options for working with aluminum wiring. The first option is replacing all aluminum wiring with copper, like above.

The other process is called wire remediation. This process connects or "pigtails” copper wires to the ends of aluminum wiring. Adding copper wire at each termination point allows copper-rated devices to be used.

The result of improper pigtailing

We recommend hiring a licensed electrical contactor to complete remediations because there are dangerous intricacies. Aluminum wire expands and contracts more than copper wiring, which can create loose connections in the pigtails. Oxidation, as previously mentioned, also remains a risk with aluminum wiring. Any mistakes in this process can create fire hazards and electrical risks for you and your home.

The costs of these processes vary. For aluminum wire remediation, it typically ranges between $2000-4000, depending on the job size. Rewiring a house requires much more material and labour. Depending on the home, you can expect to pay $10,000-$20,000.

Whether you are purchasing a new home or looking to update your current electrical system, Kraun is here for all your rewiring needs. We’d be happy to get started on your next electrical job. All you need to do is reach out by email at or by calling us or filling out the form below.

Let’s start a job together

Serving the Hamilton and Niagara area.

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