Aluminium Branch Wiring: Why It Matters and What Your Options Are

Homes built or extended between roughly 1965 and 1975 sometimes have aluminium branch circuit wiring — the small conductors feeding outlets and switches, not the large service entrance conductors, which are still routinely aluminium and perfectly fine.

The actual problem

Aluminium isn't dangerous as a conductor. The problem is what happens at the ends. It expands and contracts more than copper with heating cycles, which loosens screw terminals over time. It also oxidises into a layer that conducts poorly, and that layer forms wherever the metal is exposed.

A loose, oxidising termination generates heat. Heat loosens it further. That's the failure mode, and it happens at outlets, switches and splices — not in the middle of a cable run.

How to identify it

• Cable sheathing printed with ALUMINUM or AL, visible at the panel or in the basement
• Dull silver conductors at outlets rather than copper-coloured
• A build date between the mid 1960s and mid 1970s
• Warm switch plates or outlets that have discoloured
• Note: copper-clad aluminium exists and looks copper at first glance — check the sheathing print, not the conductor end

Your three options

• Full replacement. Rewire the branch circuits in copper. Most expensive, most definitive, and the one insurers like best.
• COPALUM crimping. A permanent compression connection joining a copper pigtail to the aluminium conductor. Widely regarded as the best repair short of rewiring, but requires specific tooling.
• AlumiConn connectors. A rated set-screw connector joining copper pigtails to aluminium at each device. Far cheaper than a rewire and accepted by most insurers.

What not to do

Do not pigtail with standard twist-on wire nuts, and do not simply install devices marked CO/ALR and consider it finished. Standard connectors are not rated for the dissimilar-metal connection and the anti-oxidant compound matters. This is a case where the cheap version of the repair is genuinely worse than no repair, because it looks solved.