I have a couple of power outlets in my cabinets, one for a built-in microwave, the other for a countertop light. Should they be (1) flush with the wall and have the opening in the cabinet cut out bigger so that a face plate can be installed resting on the wall or (2) flush with the cabinet, using an electrical box extension, so that the face plate rests on the cabinet?
The advantage of (1) is that it spares using box extensions but of (2) it preserves more of the structurally important horizontal boards in the back of the cabinet on the top and bottom but the advantage and it also looks more elegant.
If the gap when split is less than an 1/8" it's probably acceptable to caulk it and then tile around it if you so choose. If the gap is bigger than 1/4" (between an 1/8 and a 1/4 is debatable) you can consider scribing the c-top into place but it will require a diamond grinding wheel and nerves of steel. You may want to consult a professional stone mason on that one. The biggest problem is you're adding scribe to the cabinet and loosing depth and width on your top which is subtracting from your overhang so you'll have to be judicious. Anything less than say a 1/2" of overhang will look odd. It should be noted that this kind of problem would require your wall to be out of square by 1/2" over 30"-36"? depending on your vanity. That's a lot. If that's the case, you might want to consider fixing your walls before you begin setting cabinets. If the problem is just an acute build up of compound in the corner, you may be able to scrape off the mud where needed but if you have to start cutting in to the drywall below the paper, its not worth it. Best of luck!
Best Answer
The ruling factor is that the junction box must be made of an appropriate material. Not particle board.
If you have a junction box inset into the wall so it's flush, and then you put 3/4" of wood material above it, and use the long outlet screws to mount through that, then effectively the junction box walls are wood. So if things get sparking or molten-copper-dripping in there, it sets the wood on fire. Whee!
You may say "but they allow this with drywall!" Drywall doesn't burn. It's used as a firestop, actually.