Adding crown molding to a room can be tricky, because you can’t install the molding the way you would with regular trim. The most difficult part of installing crown molding is cutting the corners. The corners need to be cut with a coping saw to ensure that the angles are correct when they match up. A coped joint is what you’ll want for crown molding. To ensure the length of your molding matches up exactly to your wall space, you will want to “measure twice, cut once.”
Make your length cuts with a miter saw, as this type of saw will provide greater accuracy, allowing you to make fine cuts if you’re off by a small amount, such as of an inch. You will need to mark the walls and the ceiling where you want the molding to go, just as you would with regular trim, to ensure that your lines are straight across. Use a level for this process and a chalk line if you have one.
Do not confuse yourself with the coping saw and the miter saw. The coping saw is for cutting tight angles for inside corners. Outside corners are what the miter saw is for. If you start to the left of the room and work your way around, moving to the right with each installation, you will be able to keep your cuts straight and make them without having to adjust the saw each time.
If you do not want to use a coping saw, then you can buy corner blocks that will allow you to make simple square cuts instead. These blocks are decorative as well so they will look just as good. Regular trim and baseboards are a little bit simpler, but they still require a lot of cuts, so a miter saw should be purchased or rented for this project. Miter saws can be purchased for a $100-$300.