The subject of baseboards came up when Less from Lannigan, Saskatchewan wanted to know how deep trim nailing should go into the wall. The answer is simple, the length of the nail more complicated. A trim nail should go 3/4 of an inch into the stud of the wall. But then you have to add to that the thickness of the drywall and the thickness of the trim or baseboard where you happen to nail. That usually means a nail or brad 1-3/4 inches to 2 inches long.
While we are on the subject of baseboards let me pass on some working tips for beautiful looking baseboard joints.
The outside corners are simply mitred at 45 degrees and cross nailed to each other. This may have to be adjusted if the wall is not exactly 90 degree or the corner bead pushes the end of the baseboards out from the flat of the wall. If you cut or sand away a bit of the heal of the joint, the outside edge will fit tighter. Actually this joint is always done last because it is the easiest to adjust as long as your boards are the right size or too long, but too short is fatal.
When you have to make a running splice in the middle of the wall either cut it to 45 degrees or a flatter 60 degrees. The key here is to align the cut of the joint perpendicular to the line of sight when entering the room. If it opens a little, you will not notice the gap. You may want a running splice because it is a long wall, or to use up shorter pieces of baseboard or because you cut the piece just a little too short to make a good outer corner. In the latter case you should cut back some distance and splice in another piece. When possible, locate the splices behind furniture or near other visual obstructions.
It is the inside corner that is the most complicated and that more often shows up less than perfect craftsmanship. This is because if you cut it at a standard 45 degrees, you cannot nail the two pieces to each other like on the outside corners and with eventual shrinkage, you usually see the joint. This crack is accentuated by the fact that the line of sight is always straight into the corner, following the mitre joint. Inside corners should always be done first.
The best way to do this joint is to 'cope' one side and play with the line of sight.
First decide where is the most common line of sight, usually walking into a room looking along one of the two walls. Then perpendicular to the line of sight, run the baseboard square into the corner. This way, if the coped edge is less than perfect, or shrinks a little, the common line of sight will not reveal the joint.
Now mitre the other piece at 45 degrees as if you wanted to make a mitred joint in the corner. By the way, this end of the board is always prepared prior to cutting it to length so any length adjustments can be made on the other end.
Take a pencil and darken the cut edge as in the photo. This is the line along which you will make the coping saw cut. I must thank Ian Burns for this tip, the easiest and most accurate way to draw the pattern that will mate with the other piece of baseboard.
When you cope along the line, angle the coping saw into the board to stay carefully on the line but remove a bit more behind the line. This will prevent the heel of the cut from holding the joint open and in fact allow you to press the pattern right into the other board. The end result makes it appear as if you had a mitred joint that is very tight, but will not open up to the line of sight.