05/19/2026
Black copper and aluminum wiring are two things inspectors pay close attention to — but for very different reasons.
Black Copper Wiring
When copper turns black, it’s usually a sign of:
* Moisture intrusion
* Corrosion or oxidation
* Overheating
* Chemical contamination (often from sulfur compounds or poor environments)
The problem is the corrosion can increase electrical resistance, which creates heat. In severe cases, connections can become loose or fail completely. We commonly see this in damp crawlspaces, attics with poor ventilation, around roof leaks, or older overheated connections.
Aluminum Branch Wiring
Aluminum wiring itself is not automatically “bad,” but older solid aluminum branch wiring (commonly installed in the late 1960s–1970s) has a history of:
* Expanding and contracting more than copper
* Loose terminations
* Overheating connections
* Oxidation at devices and splices
That combination can create fire hazards if not properly repaired or maintained. Special connectors and approved remediation methods are often recommended.
As inspectors, we’re not just looking at the wire type — we’re looking for signs of heat, corrosion, improper terminations, double taps, and unsafe modifications.
“Electricity usually gives warnings before it gives problems.”