For over 50 years now, house wiring has included a mix of copper and aluminum wiring, even today. You have likely heard of the problems associated with the use of aluminum. There is some truth to this, some not, and it has been coming up regularly in house sale inspections since I started selling homes 27 years ago.
First the caveat — I am not an electrician. Please enlist the services of a qualified electrician if you seek answers to specific questions or issues on this matter.
I run into this issue quite often as I live in a 1972 house with aluminum wiring, and I have sold dozens of homes all over St Louis with it, and especially St Louis County within a few miles of the 270 corridor, when those municipalities were being built out 40 to 50 years ago. I have researched the issue and feel that most articles that are available for viewing are in line with my experience, and what I have heard from building inspectors and electricians over the years: It is not so much the aluminum wiring itself at risk, but the connections.
The main residential feed from the electrical utility (Ameren around here) to the house panel, is almost always aluminum, even today. It is a good conductor of electricity and is less expensive than copper. The branch or field wiring from the main house panel to each receptacle, switch or fixture has been copper since wiring began before 1900 until today, except for a period from about 1965 to the mid 1970s, when aluminum field wiring was used extensively due to the soaring cost of copper.
The characteristics of aluminum (silver) and copper (gold) metals are different enough that they need certain connections to be made between the two. It is when these connections over time develop too much resistance due to oxidizing or looseness and arcing that can cause a fire. On a house sale in that age period, inspectors look for outlets and switches marked CO/ALR, which was designed in the early 70s especially for this type of use, or for “purple wire nuts” that pigtail copper wire to the end of the aluminum. In the past, normal wire nuts have been used with a special paste, but that may not pass muster today. I have found most basements in that period to be finished with copper wiring, as commonly completed later on, and many professional kitchen and bath renovations bring some new copper strands up from the panel, so there can be a mix thoughout the home.
I have not noticed any difference in demand or pricing between homes with aluminum vs copper wiring. It is, however, a safety concern and a potential inspection issue that you need to be aware of, especially if you are working on a home that has some, and when you buy or sell. If the inspector recommends that an electrician review all connections and repair as needed, many buyers are asking the seller for that to be done, and it can be taken care of in its entirety, be negotiated out in lieu of other repairs, or some dollar credit issued to the buyer at closing. Figure about $25 per switch or outlet for an electrician to handle this, and $70 per GFCI, labor being the vast majority of the cost.
Happy Wiring!
Gary Hoeferkamp, Broker - Owner of Hoeferkamp Real Estate 