Duplicate thread.

This was already asked: http://ths.gardenweb.com/forums/load/wiring/msg0515190617120.html?1

Sorry, wrong thread. The other was a different question.

"My bad" as they say.

HOLD IT!... so you're chiseling out a j-box-sized hole into the (hopefully) hollow-core of your CBS wall, just so the exterior box will be flush-mounted? How do you know you won't hit a center web, or TWO end webs in the block structure? Plus, every so many of the aligned vertical cavities contains a rebar, and a poured column... don't want to damage that either! =:O

Generally, in a CBS home, you live with big "bumps" on your exterior walls, wherever aftermarket boxes are added, and there are no "architectural features" (wood/foam/entry foyer) to embed them in.

But, assuming you've reconnoitered your structure with a drill and coat hanger... In answer to your question: NO, you can't use an INterior EMT box on the EXterior of your home, CBS or otherwise, then jury-rig it with stucco, LOL... (I'm assuming CBS = Florida or the Carribean?... ;')

Besides, I don't think the Liquidtite/exterior gasketed covers will properly mate/seal with an EMT box. Oh, I know, there's a million tract homes, and under-inspected addtions out there with such "rigs", but they don't meet code either.

Conversely, YES, to meet code, you must use an EXterior j-box... they come in PVC and coated metal. I'm no pro, but I've seen no prohibitions on stuccoing over... after inspection. Probably have to "rough up" the box for REAL stucco to adhere... I'm thinking there's a thinner, textured fascimile (spray? brush-on?) made for this... me, I just paint (box only), and leave it smooth. The faceplate + hinged covers I just leave gray/white/original... would only consider using spray on them.

I'm not sure what code requires to connect inside and outside boxes, but I just use a 1/2" (nominal) dia. RIGID (threaded) nipple that's long enough to span the block + stucco + whatever's on the interior side. IIRC this requires a hole made w/ a 7/8" masonry hammer-bit. The metal exterior boxes are pre-threaded for such, the interior box will need a locking collar. You'll be grounded up the wazoo... esp. if you top it off with a GND wire! (optional)

HOLD IT!!!

Please don't bump super old posts like this.

you most certainly can do it the way you propose, but a much simpler method would be to use what is referred to as a "handy box". they have found many uses over the years, but were originally designed to be embedded in block/brick/etc. the mounting tabs on the box face inward (as opposed to the outward facing tabs found on standard single gang device boxes). just run the proper length of emt or a rigid nipple and slap some mortar around the outside to mount the box. if you are very careful of what you are doing while chiseling the block, no repairs to the outside will be required (the weatherproof faceplate will overlap the box and mortar) but this usually takes some experience.

fyi, you may need to buy the box and an extension if you plan on fitting a gfci in there (depending on several other factors).

"HOLD IT!... so you're chiseling out a j-box-sized hole into the (hopefully) hollow-core of your CBS wall, just so the exterior box will be flush-mounted? How do you know you won't hit a center web, or TWO end webs in the block structure? Plus, every so many of the aligned vertical cavities contains a rebar, and a poured column... don't want to damage that either!"

Actually, you can chisel away.

You are not going to compromise the strength of the wall by cutting a hole for a box.