EZSMART Corporation, ESA/ECRA #7012690 , North York , Ontario
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Aluminum branch wiring was installed in tens of thousands of Ontario homes between 1965 and 1975, when copper prices spiked and builders switched to a cheaper alternative. Fifty years later, those aluminum connections are the reason home inspectors flag houses on almost every purchase in the affected age range. This guide walks GTA homeowners through whether aluminum wiring is dangerous, why the connection points are the real problem, and what remediation actually involves in Ontario.
Direct answer: aluminum branch wiring itself is not inherently dangerous; the connections where aluminum meets copper (at devices, marrettes, and terminals) are the failure point. Untreated aluminum-copper junctions oxidize, generate heat, and are a documented fire cause. Properly remediated aluminum — with CO/ALR-rated devices or copper pigtails using AlumiConn or COPALUM connectors — is safe.
If you are unsure, drop a receptacle cover plate, kill the breaker, and look at the exposed conductor. Silver = aluminum; reddish-brown = copper.
Direct answer: aluminum and copper expand at different rates when heated. A mixed connection (aluminum wire under a brass screw designed for copper) loosens over years of thermal cycling. Aluminum also oxidizes rapidly, forming a resistive layer at the contact point. Resistance generates heat, heat accelerates oxidation, and the connection eventually arcs or melts.
The Electrical Safety Authority tracks aluminum-wiring failures under residential connection-failure incidents in the Ontario Electrical Safety Report. It is not the largest category but the incidents are serious — typically fires that start behind a switch or receptacle wall plate.
Our post on whole-house rewiring cost covers the top-tier option in detail.
Direct answer: many Ontario home insurers charge higher premiums or refuse to renew coverage on homes with unremediated aluminum wiring. A written remediation certificate from a licensed electrical contractor typically satisfies the insurer.
Home inspectors flag aluminum on almost every purchase transaction. Buyers commonly make remediation a condition of closing, or negotiate the cost off the purchase price. If you are selling, doing the remediation before listing avoids the negotiation.
Direct answer: CO/ALR receptacles and switches are marked with the letters CO/ALR on the front or back of the device. They use special screw threads and terminal metallurgy designed to hold aluminum reliably. Regular receptacles — even ones marked “backwire” or “quick-connect” — are NOT rated for aluminum and must not be used.
The device swap sounds simple but adds complexity because every marrette in the box must also be replaced with an aluminum-rated connector. Not just the receptacle itself; every splice on the same conductor.
Any of these on a known aluminum-wired home is a same-day call to a licensed electrician. Do not use the affected receptacle or switch until the connection is inspected.
In our experience remediating aluminum wiring across GTA homes — particularly the older Etobicoke, North York, and Scarborough neighbourhoods where 1968-1972 construction concentrated aluminum — the single most important choice is between the CO/ALR device swap and the copper pigtail with AlumiConn. The device swap is cheaper but requires ongoing insurance conversations because some carriers still charge extra even after CO/ALR remediation. The AlumiConn pigtail approach eliminates the aluminum-at-device concern entirely and is more likely to satisfy every insurer. If you are planning to sell in the next 5-7 years, the pigtail approach is often the better investment. Our post on signs the house needs rewiring covers the escalation to full rewire.
Aluminum wiring in your GTA home? Book an ESA-certified electrician to inspect and quote a remediation. Call us at 416-838-9006 or visit our contact page — we will get back to you the same day.
Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp
