Peter McCarthy Electric Co., Inc. - Specializing in Older Buildings in Chicago
Adventures in Old House Wiring....

Installing GFCI outlets in Older Homes Pt. 1


Changing out GFCIs can be very straightforward to somewhat complicated. A GFCI receptacle is a much larger device than a standard receptacle. It takes up much more space in an outlet (junction) box. If your home is a new one, built after 1970, it is usually no issue because the junction boxes used are quite large and have enough wiring space can accommodate the receptacle. But if it's an older home, even if it was remodeled recently, chances are the junction box is much smaller. Many remodellers use small, single device "gem" boxes, and these have very little wiring space in them. If the wiring goes back earlier, gem boxes were very common. The long and short of this is there is no space to add a GFCI receptacle.

This issue is often lost on home inspectors and real estate agents, who describe switching them out as a "5 minute job."   In some cases that is true, but many, many times it is not. When the junction box is too small, either it has to be completely cut out, a very labor-intensive process, and all the pipes/cables wires have to be re-routed into a larger box (this is especially challenging with a tile back-splash, where we are not totally free to cut wall as needed and have plaster repair done later) This job is fully do-able, of course, but can be dirty and expensive. The second alternative is to raise the outlet off of the wall surface by installing an extension box. This fits over the original recessed box and provides wiring space. It is not visually ideal, but it is more economical and provides safety until the future when the kitchen is fully remodeled and new, larger size junction boxes can be installed. I just dealt with this exact issue on University Ave yesterday. I have photos and am planning to put them on my website along with the explanation I am writing here now.  We are open to installing the GFCI outlets in any manner the client wishes, of course. But I like to make the pros and cons of the issue transparent upfront. You can use this information to clarify with any electrician you hire how they plan to address this issue. A very experienced one ought to have a sense of this going in. You dont want your GFCI outlet jammed so forcefully into your undersized box that it damages the wires (almost a certainty if you have cloth covered wire) or yanks the box itself off the mounting, which it can if there is no place for the wires to go and someone pushes the receptacle too forcefully. So these are just things to consider.
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