Aluminum wiring in your home

Updated April 9, 2024

Aluminum electrical wiring in houses was common in Canada for a decade from about 1966 to 1974. Most people don’t give much thought to what their home’s wiring is made of, but it’s important to be aware of any aluminum wiring that might be lurking in your walls.

Keep reading to learn all about aluminum wiring in your home — what it looks like, what to do about it, and why it’s a problem.

Aluminum wiring

What is aluminum wiring?

Aluminum wiring is electrical wiring made out of aluminum, rather than the copper that is more common nowadays. One of the main differences between aluminum and copper is that aluminum wiring expands and contracts much more than copper under temperature fluctuations.

Aluminum was once considered a safe and inexpensive alternative to copper, but that’s not really the case. Aluminum wiring, particularly that from decades ago, is known to be a serious fire risk.

Modern aluminum wiring, installed and maintained correctly, can be perfectly safe. In fact, it’s still widely used for certain applications. Nevertheless, residential aluminum wiring poses major issues.

Aluminum wiring problems

Between about 1966 to 1974, copper was so expensive that everyone was looking for a way to cut costs for home electrical systems — thus, aluminum wiring. However, it didn’t take long to discover that aluminum wiring had some serious safety issues compared to copper.

In fact, according to the US Consumer Product Safety Commission, houses with aluminum wiring constructed prior to 1972 are 55 times more likely to reach fire hazard conditions. So not only are you at higher risk of fire but, due to the increased fire risk, you may have a hard time finding home insurance (more on that in a moment).

Aluminum wiring works just like copper wiring. The problem with aluminum wiring is not the wiring itself, but the connections.

Flowing electricity causes wires to expand and heat up. One of the issues with aluminum wiring is that it expands three times more than copper. When no electricity is flowing, the wires and connections cool down and contract. When the power is on, they heat up and expand. The constant fluctuation eventually opens gaps in the connections. The gaps expose the wiring to air, which oxidizes the aluminum. The oxidization increases electrical resistance, which makes the wiring and connections even hotter, exacerbating the expansion and contraction.

The connection gaps are also susceptible to arcing — a fire hazard.

Aluminum has several qualities that make it an undesirable substitute for copper. Some of these qualities are:

  • Higher electrical resistance
  • Less ductile, being prone to damage when bending
  • Galvanic corrosion, a tendency to degrade when in contact with certain other metals
  • Oxidation
  • Greater malleability, and a tendency to continuously deform under stress
  • Greater thermal expansion and contraction
  • Excessive vibration

The right aluminum wiring alongside the right maintenance program can be safe. However, home systems are often full of work done by many hands — both qualified and unqualified.

Aluminum wiring in your home

For all the reasons outlined above, its crucial to be aware of aluminum wiring in your home (or in a home you might purchase).

How to identify aluminum wiring

To identify aluminum wiring in your home, look at the wires wherever they may be exposed. Check between open floor joists, in the basement or attic, or at the electrical panel.

According to the Alberta Safety Codes Council, you can identify aluminum wiring by checking the wire jacket for the symbol AL. ALUM is another possible mark of aluminum wires. If you can’t identify your wiring visually, you may need to hire a qualified inspector or electrician to dig a little deeper.

You can also identify aluminum wiring by removing the cover of your electrical outlets or switches and looking for one of the following marks:

  • CO/ALR
  • CU-AL
  • AL-CU

Not only does this mark signal aluminum wires, it says you’ve got aluminum-rated outlets and switches — which is good news.

Some homes have both copper and aluminum wiring, having been installed separately over many years. This is also a hazard, unless everything was installed with the right aluminum-to-copper connectors. The different degrees of expansion and contraction between the two metals make potential gaps worse, causing serious fire concerns.

When should you call an electrician?

If you have aluminum wiring in your home, you may not think there’s anything wrong if you haven’t had any problems with it. But issues can take a long time to appear. It’s wise to have an electrician check your wiring before anything goes wrong. You should have your aluminum wiring inspected by a pro at least every 5 years.

Call an electrician ASAP if you notice any of the following:

  • Unusually warm outlets or faceplates
  • Strange odors, smoke, or sparks around receptacles or switches
  • Occasional flickering of lights
  • Unexplained static on TV or radio

Any of these things could indicate a potentially serious problem with the wiring.

Do you need to replace aluminum wiring?

Electrical contractors can assess your wiring, make necessary repairs, and provide you with a Certificate of Inspection for your records. Your insurance company may want a copy of the certificate as well.

It’s not always necessary to replace aluminum wiring, but it is important to have a qualified electrician check and advise on the best course of action for your home.

InterNACHI suggests two methods for addressing aluminum wiring:

  • Rewiring the home with copper wire. This is obviously the expensive path, which most would prefer to avoid.
  • Using copalum crimps, also called pigtails. Having someone install these special connectors to each wire end is a more economical fix.
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Aluminum wiring home insurance considerations

Home insurance providers always ask about your home’s electrical system.

They’ll often ask specifically about aluminum wiring, given that it’s a known fire risk. Since home insurance does typically cover damage from a accidental electrical fires, they need to know what sort of risk the home faces. Keep in mind that with the perceived higher risk of problems with aluminum wiring, you may have trouble finding an insurer, or you may have to pay a higher premium.

If you are considering buying a home with aluminum wiring, check with your insurance provider (or alternative providers) first. Some providers will not insure homes with aluminum wiring. Others are okay with it, provided a licensed electrician has inspected and passed the electrical system.

Square One, for example, can usually offer coverage for homes with aluminum wiring. The conditions are that the outlets and switches are aluminum rated, and the system has been inspected by a professional in the recent past, with no issues found (or those issues having been fixed).

Commonly asked questions

How much does it cost to rewire a house with aluminum wiring?

There are many, many variables that affect the cost of changing aluminum wiring to copper. The size, age and condition of the house, the accessibility of the wiring, and other unexpected oddities can all change the cost.

Roughly, expect to pay between $8,000 and $15,000 to rewire a 1,500 – 3,000 square foot home. You can probably infer from those wide-ranging numbers just how unexpected overall costs can be. For a better guess, consult an electrician and ask them for a full estimate of your home, and perhaps even shop around to see how their quote compares to competitors.

Why was aluminum wiring used in my home?

If your home was built between about 1966 and 1974, it’s electrical wiring may be aluminum. The price of copper skyrocketed during this time, making aluminum much more attractive for contractors and homeowners alike.

Is aluminum wiring safe?

Aluminum wiring itself is not inherently dangerous. It’s the connections within an aluminum wiring system that create fire hazards. If the system is installed and maintained properly, with all outlets and switches aluminum rated, it’s safe. However, many residential aluminum wiring systems are very old. The result is a high occurrence of shoddy DIY fixes and deteriorating connections, making the systems less safe.

What is the life expectancy of aluminum wiring?

Aluminum wires themselves are plenty durable, having a reported lifespan of 80–100 years. However, that assumes they were installed correctly and have been well maintained. An aluminum system with defective connections or other issues can be a fire risk at any point in its lifespan.

Will aluminum wiring pass inspection?

During the process of buying or selling a home, the home inspector will identify aluminum wiring in the electrical system. If that’s the case, it would be wise for the buyer to have a qualified electrician inspect the system to determine how much (if any) work it needs. If the system has aluminum rated outlets and switches, and is otherwise determined to be in good condition, it need not be a deal breaker.

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