(In Pittsburgh, PA).

I am installing a new exterior outlet on a brick wall (surface mount). I've drilled through the brick veneer and CMU, but now I am wondering - is conduit required here? All the tutorials I see on YouTube/etc just slap some caulk around the wire and call it a day.

I'm asking because it looks like my electrical box is expecting me to use a screw in PVC bushing to connect the conduit into the back of the box. The hole I drilled in the wall is 1" - big enough to handle the 3/4" schedule 40 PVC I purchased for conduit, but NOT big enough to handle the gigantic bushing I purchased (both pictured below).

I don't have a way to make the hole large enough to handle this bushing - all of the masonry bits that are large enough at my local store require a SDS drill, and I hate to buy that just for this purpose.

I suppose if conduit is required, I could buy a different exterior box with 1/2" holes, and the bushing for that should probably fit in the existing hole.

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  • 1
    SDS drills and maybe bits can usually be rented, if needed.
    – crip659
    Commented Jun 23, 2023 at 15:28
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    You could measure the length required and get a piece of rigid (RMC) or intermediate (IMC) 3/4" conduit cut and threaded to fit, no adapter needed. Why do you picture a 1-1/2" bushing if you need 3/4" threads, by the way? For that matter, is the hole about 3/4" and threaded (in which case it's threaded for 1/2" threads? Because threaded pipe and conduit sizes are weird...)
    – Ecnerwal
    Commented Jun 23, 2023 at 15:37
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    My understanding is that technically anything outside should be conduit but that practically speaking as long as it is "cable goes through hole directly into the back of the box and cable never visible/accessible outside the building outside the box" that this is a non-issue and inspectors will normally allow that. That being said, GET A METAL BOX!. Commented Jun 23, 2023 at 15:53
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    @manassehkatz-Moving2Codidact Fair enough! I think I have to make a trip to the store anyway.
    – negacao
    Commented Jun 23, 2023 at 15:57
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2 Answers 2


You can use a 3/4M to 1/2F threaded reducer bushing to use 1/2" conduit with your 3/4 threaded box holes.

Or, you could measure the length required and get a piece of rigid (RMC) or intermediate (IMC) 3/4" conduit cut and threaded to fit, no adapter needed.

Technically, unless your LAHJ requires all wiring in conduit (common enough for cities, though I don't know for sure about Pittsburgh, specifically) you could come through the wall with a waterproof cable into an appropriate clamp on the box. Many LAHJs permit using non-waterproof cable if it's an exterior box on the face of the wall, though I'm pretty sure that's a bad idea for any outside box, and technically a code violation where enforcement is strict. If you are running THWN wires, conduit is 100% required.

  • Covers all points.
    – FreeMan
    Commented Jun 23, 2023 at 16:35
  • If OP uses a standard NM strain relief clamp with waterproof cable, is the clamp's thread compatible with the threads in this box? So that it can be used without its nut? Otherwise a different style of box would be needed for the waterproof-cable-with-clamp idea, which is my favorite of the ones here.
    – jay613
    Commented Jun 23, 2023 at 16:39
  • If bothering with waterproof cable one should bother with the appropriate clamp for it. The threads are compatible, normally, yes. This type of box normally does specify additional sealant on threaded ports in the small text molded in, though.
    – Ecnerwal
    Commented Jun 23, 2023 at 17:28

The box pictured is far larger than needed. Get a Single gang box.

It's ready for 3/4 or 1/2 inch fittings for PVC. I would use pvc to get into the wall. and be sure it was sealed at the exterior to prevent moisture, air and insect infiltration into the wall cavity. This is better than just filling hole around the wire full of caulk.

  • I actually want the double gang.. but yeah, you're right, I should do conduit regardless of it being required or not. :)
    – negacao
    Commented Jun 23, 2023 at 15:59
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    Ah, but you can (almost) never go wrong with more Cu. In. than is required by code. Each additional inch makes your life easier.
    – FreeMan
    Commented Jun 23, 2023 at 16:34

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