I usually use these clamp connectors to connect flexible metal conduit to a box:

However, I am now installing a weather proof light fixture box outside of a shed (just surface mounting it, poking the FMC through the wall straight into the back of the box - basically like this but surface mounted). So I didn't think that warranted fully water proof conduit, but I can't seem to find any connectors that will keep water out of the box at the connection point. Do I not need to be worried about this?

  • Home Depot or other supply stores should have a full range of weather-tight conduit options. What do you mean you can't find any? – JPhi1618 Feb 20 '19 at 18:51
  • I went there (and looked online) and the only thing I could find was this homedepot.com/p/… , but it seemed to be designed to work with this stuff: homedepot.com/p/… , not the standard FMC. – David Doria Feb 20 '19 at 18:53
  • Right, that's the stuff - didn't realize you want to use the standard FMC right up to the light. Interested to see what the "right" answer is because any surface mount light I've come across is just mounted over a hole in the wall with maybe some caulking. – JPhi1618 Feb 20 '19 at 18:57

In my opinion FMC is no good for this application, even though it's only barely outside, it's not rated for outdoor use. (I realize lots of people would either disagree or figure it's close enough and run with an indoor rated wiring method.)

The easiest thing to do would probably be to set a box inside and transition from FMC to UF cable - run the UF through the wall to the back of the box with a suitable waterproof connector such as this one from Arlington:


uf connector

To connect the UF connector to the inside box, you could use an indoor-rated clamp as long as it's listing / instructions / labelling says it's for use with UF. It might be easier to just use the outdoor connection indoors as well.

You might be able to find what's called a "transition fitting" or a "this-to-that" that will connect UF directly to FMC but again it's probably simpler and easier to just transition in a box.

  • 1
    Can you link to a suitable waterproof connector from UF to the exterior box? And would you use the same "clamp connector" I showed previously for the UF to the interior box? – David Doria Feb 21 '19 at 13:01
  • @DavidDoria - sure, see edits. – batsplatsterson Feb 21 '19 at 13:20

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