I want to install outdoor string lights and need a receptacle to plug them in. I have removed an existing outdoor wall light, which reveals the following shallow box (see picture).

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The box is 3" in diameter and 3/4" deep. It's set in stucco and screwed into a stud. It can't be made deeper because of the stud. I'm willing to expand the diameter though if needed.

What sort of box do I need to put in its place so I can convert this to an outdoor GFCI receptacle?


So I chipped out more of the stucco and installed a weatherproof box and weatherproof in-use cover. I'll patch up the stucco, of course. But it looks terrible. Sticks out way too far.

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I may end up installing an LB connector similar to what's described in the following post and running conduit to elsewhere: Is a splice permitted in a PVC conduit body?

2 Answers 2


As mentioned in your follow-up question, Jimmy Fix-it's solution didn't work.

As you are just adding string lighting, the best option is to keep your outdoor wall light and it's protective sconce, and remove your light-bulb and insert at light socket to outlet adapter (no GFCI needed).

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If you feel you need a GFCI, you can use this 2 prong GFCI adapter:

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If you want a ground and a GFCI you can use a 2 to 3 prong adapter with wire and an inline GFCI: enter image description here enter image description here


Surface mount a weatherproof 4/O box extension over the top of your existing box and feed the wires through the back. Seal around the box where it meets the wall so water cannot get behind it.

Then install a weatherproof conversion cover, they are fairly new and I have only seen them on the internet. Then install a weatherproof receptacle cover and you are done!

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  • I'm not sure if a 4" extension will fit against a 3" round box.... Commented Aug 8, 2016 at 0:24
  • They have surface mount tabs, screw it to the stucco with anchors. Basically his old 3/O pancake box with NM cable clamp gets extended into a 4/O WP surface mount box. Commented Aug 8, 2016 at 1:38
  • I don't believe that leaving a discontinuity in the box wall like that's within the spirit of Article 314 (although strangely enough, it seems to be legal for sub-1kV, unless 314.19 applies to forbid that?) Commented Aug 8, 2016 at 3:56
  • As long as the material between the two boxes is noncombustible (like stucco) I think its ok. I know, "I think" has sunk ships, but minimal actual hazard IMO. Same as an interior box that's not quite flush with the finished wall surface, no? Commented Aug 8, 2016 at 4:44
  • Even for a wall box in a non-combustible wall material, 314.20 limits you to ¼" of exposed wall material due to the box not being flush. Commented Aug 8, 2016 at 5:01

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