Putting an electrical box in aluminum soffit

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Old 06-30-19, 10:01 AM
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Putting an electrical box in aluminum soffit

I'm closing off the soffits in an outbuilding, and would like to put round electrical boxes for future electrification in the front corners. The goal would be a set of floods.

Located: Michigan
Construction: Metal roof, aluminum soffit

It seems electrical boxes can be PVC or aluminum, conduit can be PVC or flexible liquidtight (with either a metallic or non-metallic core).

I'd like to do all PVC as I can be assured the whole assembly is water-tight, and am tempted to use the metallic-core flexible conduit (this is a short run to the interior, so I don't need a lot of exterior conduit either way).

Where I'm stuck - I don't know how to mount the round electrical box, nor where (if) to get a trim ring for my soffit.

Basically, I'd like to mount the box ABOVE my soffit but sticking out 1/4". Is this normal? Or do I just put a 2x board above the soffit for something solid to screw into and mount the box below my soffit? I was trying to make it as invisible as possible, as the lights themselves will be ugly enough as it is.

Thanks!
 
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Old 06-30-19, 11:10 AM
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You use new construction boxes that are on adjustable brackets.

https://www.homedepot.com/p/Carlon-4...-UPC/202065289
 
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Old 06-30-19, 01:02 PM
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I'm assuming you want to wire before closing off the soffits ?
In that case you wouldn't use any type of conduit. You'd use UF type weatherproof/outdoor cable and run it thru the soffit. The box Sleeper has shown would work.

I can't quite picture running PVC conduit thru the soffit but if that is the case..... you are limited in your choice of boxes. Then you would need to use actual outdoor boxes attached in the back with the proper support. Those boxes can be made of PVC but most are diecast and you would use screw in connectors for PVC conduit.

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Old 06-30-19, 03:04 PM
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You don't need watertight under the soffit. Just use a standard nail on box sticking down the depth of the siding. You can also use an 8B box with a spreader bar.
 
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Old 07-01-19, 07:43 AM
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Thanks for the details - I wanted to do conduit as I'm not going to run the cable for a while. I like the Carlon box you suggested, just need to work out how I'll mount the box. On the outside surface of the aluminum would be easiest (with wood backing to screw into), but I'd like to flush mount it (with .25" sticking out) which means finding a suitable surface ring to trim it out.
 
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Old 07-05-19, 07:27 PM
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If you're flush-mounting, you can use any indoor type box that is easy to mount. Could be a nail-on round box or a round box with a metal bracket between joists. Or could use a rectangular box too, but round is more common. Since it's flush and technically interior, it doesn't have to be weatherproof.

If you flush-mount, you should use the one that was PJmax posted. If you come out the back of the box directly into the soffit, you can run standard NM-B. If it were me, I would probably run 14/2 NM-B cable and just leave it hanging in the attic or into a box. Then you can finish it up at a later date.
 
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Old 07-13-19, 07:06 AM
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After looking at my options I decided to go with a flat/flush LED downlight. It provides enough light for when I need it, and supports being dimmed. It has a remote driver box, so what I'm doing is mounting the box *inside* the structure, and running the (low voltage) wire to the the light through the soffit. It's rated for wet locations, so no concerns were there ever to be a leak.
 
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