Recently had a quartz backsplash installed and was told the electrical boxes are to be BEHIND the backsplash. In other words, the electrical outlet would sit flush with the wall, without an electrical box extender and we should use long screws to attach the outlet to the electrical box behind the backsplash. This does not sound safe nor up to code for NY. Could someone please clarify. Thank you in advance.
314.20 Flush-Mounted Installations. Installations within or behind a surface of concrete, tile, gypsum, plaster, or other noncombustible material, including boxes employing a flush-type cover or faceplate, shall be made so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (1∕4 in.).
Most tile or backspash is 1/4" when it's done (thin set + tile). Assuming you have new construction, your electrician will come in first and wire everything up, with the box as close to the surface as possible (usually, some do cut corners here). Then the builder will either put drywall or some sort of backer board up. Finally, you tile. This necessitates something important: you must cut the tile to allow access to the box.
The simple answer is that, if the box is flush with your mounting surface, it might be compliant as-is after tiling. If not (i.e. your tile is over 1/4"), you can make it compliant with an extension ring that does indeed use long mounting screws.
I had a 3/4" quartz back splash installed and we used box extenders. The back splash is not always tight to the drywall surface so the box extender helps seal or bridge this gap.
Looks like based on the referenced answers that boxes can only be 1/4" recessed from non-combustible surfaces.
We used these white box extenders:
The advantage of the white box extender when you have a thick back splash that is quartz is that you don't need to cut the corners perfectly for the box extender to fit into the hole. The quartz installer I used didn't have the box cuts perfect so they had to be adjusted to allow the box extenders to fit into the back splash. The quartz installer never had to do this before - I guess people just skip the box extenders even though they are code - and learned on my job so initially he was cutting the corners which is the hardest part once the back splash is installed.