electricalproduct-recommendation
Does anyone make a back box that has (British) standard 1-gang lugs, but the actual box extends beyond that?
i.e. something could be mounted centrally with 1-gang spacing (and it would cover the whole box) but the box would have more space either side of that.
Does anything like that exist? Closes I've found is dual 1-gang boxes, where two sit side by side, that would be OK except that I need the 1-gang spaced mounting to be central, or else the box probably wouldn't be covered one side.
Here in Australia you'd probably use a surface mounting block over the top and then an IP rated outlet.
Mounting block is bigger than a round j-box. May need to seal between block and wall and then you're done.
Along these lines:
Source: http://updates.clipsal.com/assets/images/products/A00047211.PNG
Not sure whats available and standards in the US but if surface mounted over the top and larger, shouldn't be an issue but uglier than flushed.
May be able to drill/chase in a large wall box, however it's quite a bit of work.
It was common to wire "switch loops" where a black and white wire were run between a switch and a light, and the white (neutral) wire would actually be used as a hot. When this was done, the white wire would be marked with black tape on both ends to say "this wire is really doing the job of a black wire". (wire colors are assuming common US conventions).
What you are proposing is doing something similar, but using a black wire as a neutral. This will work, but according to another question you can't repurpose a black wire as a neutral because code requires a neutral to be a certain color over the entire length of the wire.
So, electrically, it will work, but it seems to be an illegal modification.
Best Answer
You can get various conversion patresses which will fit over a flush 1-gang box and present a surface 2-gang box, eg
and conversion sockets, eg
If you want to fit a single socket on a double box you'd probably need to use a Euro module faceplate, Euro module socket and blanking plates
If you just need a decorative cover then 'finger plates' are available in white or clear
https://cpc.farnell.com/pro-elec/pel00515/finger-plate-for-light-switch/dp/PL10027