Mounting electrical boxes, device boxes, J-Boxes (Junction Boxes), and outlet boxes requires an understanding of the National Electric Code and the local building codes whose requirements may be more stringent than the National Electric Code. Mounting electrical boxes requires an understanding of trade “Conventions.” Trade conventions establishes uniform practices throughout the trades. The electrician needs to understand these rules and conventions because it’s information that he won’t find on the working drawings.
Mark the studs on which receptacle device boxes are to be mounted. Article 210.52 of the National Electric Code states that no point measured horizontally along the floor line shall be more than 6-feet from a receptacle and that any wall space 2 feet or more in width shall have a receptacle. The code recognizes a duplex receptacle as being two receptacles on one strap so after placing the first box at 6-feet, the remaining boxes can be spaced at 12-foot intervals.Studs are spaced either 16-inches o.c. (on center) or 24-inches o.c., so you can save time by simply counting studs to determine box spacing. With 16-inch spacing, nine studs equal 12-feet. Since 6-feet falls between the fourth and fifth stud, you would mount the box on the fourth stud.
Mount the boxes so that the top of the box is 12 inches above the finished floor. This is the standard height for wall mounted receptacles. This is a trade convention, not a Code requirement.
Position each box on the stud so that the front lip will be even with the surface of the finished wall (NEC Article 314.20.) most ABS Plastic device boxes have a positioning gauge on the side of the box that make this quick and easy. This also applies to device boxes for switches and to lighting outlet boxes as well.
Make sure that the box is straight vertically and then secure it to the stud.
Mount all device boxes for switches so the top of the boxes is 46 inches above the finished floor. Forty-six inches is a trade convention.
Mount all outlet boxes for wall mounted light 66 inches above the finished floor.
Mount devices boxes for kitchen counter receptacles so the top of the boxes are 44 to 46 inches above the finished floor, depending on the back-splash. The box may be entirely in the tiled back-splash or entirely above it but it can't be half in and half above the tiled back-splash, that's a Code violation.