The installation of baseboard trim serves two purposes. It not only adds an aesthetically pleasing finishing touch to a room, it also serves the purpose of filling the gap left between the wall and the floor that exists purposefully in order for walls to expand and contract due to humidity. Baseboard, itself, expands, as well, and in order to fit well in corners, it must be fitted together with coped joints.
Coping saws are used to cope joints for the installation of baseboard trim. This type of saw is similar to a hacksaw. A coping saw, however, is deeper, shorter, and has a narrower blade than a hacksaw. Coping saws are flexible enough to change directions easily, which makes them ideal for cutting out the profile of one piece of baseboard from another, a trick to dealing with corners we will cover below.
The First Piece
Begin installation of baseboard trim with the wall opposite from where the door is going into a room. Cut the piece of baseboard you will be using a sixteenth of an inch longer than the wall. This gives a tight fit and allows the piece to continue to fit well during dry-weather times, when the humidity is low.
The ends of this first piece of baseboard should be cut square. No coping is done until you get to the trim that fits against this piece on the two walls meeting it at either corner. Because you have cut it slightly longer than the wall, it will take a little pushing with your hands or tapping with a hammer to get it to fit.
To avoid splitting the wood during installation of baseboard trim, pre-drill the holes for the finishing nails first. With wire snips, clip off the head of a nail and use it in place of the drill bit in your drill. Drive finishing nails that are long enough, 6d or 8d, into the 2×4 studs that go along the inside of the wall. You can determine where these are by the solid sound made when you tap a hammer along the wall.
Add Mitering and Coping to the Mix
For the next piece of baseboard, use a power miter saw to cut a mitered end to fit against the trim you just installed. Cut it as you would any other corner and then trace the profile of the cut end with a pencil. With the coping saw, hold it at a 90-degree angle and shave off the edge of trim.
Use a rat-tailed file to smooth off any ragged edges. Cut the other end of this piece square and, again, a sixteenth longer than the length of the wall. Go around the room in this manner until finished.
Some people like the look of quarter round put in at the bottom after installation of baseboard trim. Sometimes called shoe molding, this can be installed just like the baseboard, but keep in mind that if you are laying carpet, the quarter round must be installed afterward. For all other types of flooring, it can be installed before or after.