Aluminum branch circuit wiring was used in hundreds of thousands of Ontario homes built between 1965 and 1976, including huge numbers across the GTA — in Scarborough, North York, Etobicoke, Mississauga, Brampton, Ajax, and Pickering. I'm Sam from City Power Electrical Services (ECRA/ESA #7015314), and aluminum wiring remediation is one of my most frequent jobs. Here's what you need to know about the fire risk.
The core issue with aluminum branch circuit wiring is at the connections, not the wire itself. Aluminum wire running through your walls is fine. The problem occurs at every point where the aluminum wire connects to something — outlets, switches, light fixtures, junction box splices, and the panel. Here's why.
Aluminum expands and contracts significantly more than copper when it heats up during normal electrical use. Over time, this thermal cycling causes connections to loosen. A loose electrical connection creates resistance. Resistance creates heat. And heat at an electrical connection is the start of a fire. This process is gradual — it happens over years and decades, which is why aluminum wiring fires often occur in homes that have "never had a problem" for 40+ years.
The second issue is oxidation. When aluminum is exposed to air, it forms aluminum oxide on its surface. Aluminum oxide is a poor conductor, which increases resistance at connections. Copper also oxidizes, but copper oxide is still a decent conductor. Aluminum oxide is not.
The third issue is dissimilar metal connections. When aluminum wire is connected to devices designed for copper (which was the case for many switches and outlets installed in the 1960s and 1970s), galvanic corrosion accelerates the deterioration of the connection. Modern devices marked CO/ALR (copper-aluminum revised) are designed to work with aluminum wire, but many older homes still have the original non-rated devices.
How serious is the risk? According to research cited by the U.S. Consumer Product Safety Commission, homes with aluminum wiring are 55 times more likely to have one or more connections reach fire-hazard conditions than homes with copper wiring. The Electrical Safety Authority in Ontario also recognizes aluminum wiring connections as a significant risk and recommends remediation.
That said, context matters. Not every home with aluminum wiring will have a fire. The risk is statistical — it's elevated compared to copper, but millions of homes with aluminum wiring exist without incident. The risk increases over time as connections continue to deteriorate, and it increases with heavier electrical loads (which are far greater today than in the 1970s).
Warning signs that your aluminum wiring connections are deteriorating. Warm or hot faceplates on switches or outlets. Discolouration or scorch marks around outlets. Flickering lights (especially if it's gotten worse over time). A burning or plastic smell near outlets or switches. Outlets that spark when you plug something in. Breakers that trip for no obvious reason. Any of these signs in a home built between 1965 and 1976 should prompt an immediate call to a licensed electrician.
The proven solution: pigtailing. The accepted remediation for aluminum wiring is pigtailing — connecting a short copper wire to the aluminum wire using a connector specifically approved for aluminum-to-copper connections, and then connecting the copper pigtail to the device. This puts copper at every connection point while leaving the aluminum wire in the walls (where it's perfectly fine).
Two types of connectors are approved for this purpose. AlumiConn connectors are set-screw connectors made by King Innovation. They're CSA-approved, widely available in Canada, and the most commonly used solution by Ontario electricians. Each connector accepts one aluminum wire and one or more copper pigtails, with the set screws providing reliable, maintainable contact. COPALUM connectors use a specialized crimping tool to create a permanent cold-weld between aluminum and copper. They're considered the gold standard but require a specific tool that not all electricians have.
Both methods are recognized by the Electrical Safety Authority as acceptable aluminum wiring remediation. I use AlumiConn connectors for the vast majority of my aluminum wiring projects because they're reliable, efficient, and allow for future inspection and maintenance.
What about "aluminum-rated" devices? You may see outlets and switches marked CO/ALR, which means they're designed for aluminum wire connections. While these devices are better than standard copper-only devices, they don't address the fundamental issue of aluminum oxide formation and thermal cycling at the connection. Most electricians (and insurance companies) consider pigtailing to be a more thorough solution.
What not to do. Do not use standard wire nuts (Marrettes) for aluminum-to-copper connections. Standard wire nuts are not approved for this purpose and will not provide a reliable long-term connection. Do not use anti-oxidant compound (Noalox) alone as a solution — it helps but doesn't address the mechanical issues. Do not ignore the problem hoping it will be fine — the connections deteriorate over time, so the risk only increases.
The cost for a complete aluminum wiring pigtailing job using AlumiConn connectors is typically $3,000 to $5,500 for a standard GTA home, depending on the number of connection points. The work takes 1 to 2 days, and an ESA permit and inspection is required. After the work is done, your insurance company will have the documentation they need to confirm remediation.
Insurance implications in Ontario are significant. Many insurance companies now require aluminum wiring remediation or charge substantially higher premiums for homes with unremediated aluminum wiring. Getting the pigtailing done sooner rather than later can save you money on insurance premiums over time, in addition to dramatically reducing your fire risk.
If your GTA home has aluminum wiring, call City Power Electrical Services at 416-877-3048 for a thorough inspection and remediation quote. I'll check every accessible connection point and give you an honest assessment of the condition and risk.