Aluminum wiring in older homes

Some homes built in the 1960s and 1970s were wired with aluminum instead of copper. If a home report or a seller's disclosure mentions aluminum wiring, it doesn't mean the house has to be rewired. It does mean the connections deserve attention, because that's where the problems start.

This article covers aluminum branch wiring: the smaller wires that run from the panel to outlets, switches and lights. The U.S. Consumer Product Safety Commission (CPSC) publication on repairing aluminum wiring is the main reference here [1].

Which homes have it

The CPSC says aluminum branch wiring was installed mainly from the mid-1960s through the mid-1970s, and that homes built before 1965 are unlikely to have it [1]. A home built or rewired in that window may have aluminum on some or all of its circuits.

Larger aluminum wires are also common for the main service cable and for circuits to electric dryers and ranges. The CPSC notes that its repair recommendations don't apply to those larger wires [1]. If you have questions about them, ask a licensed electrician.

Why the connections are the concern

The wire itself running inside the walls isn't usually where trouble begins. The risk is at the ends, where the wire connects to an outlet, a switch, a light or another wire.

Over time, resistance can build up at those connections, and a failing connection can overheat [1]. The CPSC cites a national survey of homes built before 1972: homes wired with aluminum were 55 times more likely than homes wired with copper to have outlet connections reach fire hazard conditions [1]. A risk-control bulletin from State Auto Insurance explains why that matters: loose connections can overheat, arc and spark, and because connections are hidden inside walls and boxes, a fire may grow for some time before anyone notices [2].

Connections can fail without any warning. The CPSC lists signs that may show up [1]:

Outlet or switch cover plates that are warm to the touch
A smell of burning plastic near outlets or switches
Lights that flicker
Circuits that stop working for no clear reason

If you notice any of these, stop using that outlet or switch and call a licensed electrician. The CPSC says to have a qualified electrician find the cause and warns, "DO NOT TRY TO DO IT YOURSELF" [1]. Flickering lights have other causes too, which is one more reason to have an electrician look: see flickering lights.

How to tell if a home has aluminum wiring

You can check without opening anything [1]:

Go to an unfinished area where you can see wiring cables, like a basement, attic, crawl space entry or garage.
Look at the printing on the outer plastic jacket of the cables. A flashlight held at a low angle can help you read it.
Aluminum cable is marked "Al" or "Aluminum."

Cable marked "CU-clad" or "Copper-clad" is aluminum wire with a copper coating. The CPSC says its repair recommendations don't cover copper-clad wire [1].

If you can't find any markings, or can't tell, have an electrician check. Don't remove outlet covers, switch plates or the panel cover to look. Live wires sit right behind them.

On a home report, this shows up as aluminum branch circuits.

How it's usually fixed

The CPSC describes three permanent repairs, in this order [1]:

Repair	What it means	What the CPSC says
Rewire with copper	Replace the aluminum branch wiring with copper	"The best method available," but often impractical or expensive
COPALUM crimp connectors	Attach a short copper wire (a "pigtail") to each aluminum wire end with a special crimp connector, then connect the copper to the outlet or switch	Considered a safe, permanent repair. Must be installed by electricians trained by the manufacturer
AlumiConn connectors	Attach copper pigtails with a setscrew-type connector made for aluminum	The next-best alternative when COPALUM isn't available. It has a shorter track record

With either connector, the work is done at every connection point on the aluminum circuits: outlets, switches, light fixtures and junction boxes. That's why the price depends mostly on how many connections the house has.

Repairs the CPSC doesn't consider permanent

You may hear about two other approaches. The CPSC is clear about both [1]:

CO/ALR outlets and switches. These devices are rated for aluminum wire. The CPSC says replacing devices with CO/ALR versions "must be considered, at best, an incomplete repair," and they failed in its lab tests with typical aluminum wire.
Twist-on wire connectors. The CPSC does not consider these an acceptable permanent repair. In its testing, substantial numbers of them overheated severely.

The CPSC says both can only be used as temporary emergency fixes, and a complete repair should follow [1].

If you're reviewing a quote, ask which method it uses and whether it covers every connection or only some. "Pigtailed outlets" can mean very different things.

Buying or selling a home with aluminum wiring

Aluminum wiring often comes up during a sale. A few things to keep in mind:

Get it evaluated, not guessed at. A licensed electrician can tell you which circuits are aluminum, whether any connections show damage, and which repair fits the house.
Ask about insurance early. Ask your insurance agent whether your insurer has questions or requirements about aluminum wiring before closing.
Get the scope in writing. The repair should say which method is being used and how many connections are included.

Aluminum wiring often shows up alongside other older electrical items, like an old panel or missing GFCI protection. See what kind of electrical panel do I have? and GFCI and AFCI protection explained.

For what HomeCloud reports price this kind of work at, see wiring and grounding repairs. HomeCloud is a licensed general contractor that evaluates homes and prices and does the repairs, and you can request an estimate. If a bigger electrical project is coming, financing options are available.