Crown moulding can be a pain to install. The moulding has to sit perfectly in place so that it touches the wall and the ceiling. If the crown moulding is cut at the wrong angle, there will be gaps between the moulding pieces. Manufacturers have started making do-it-yourself plastic moulding kits. These kits are easy to install and will give you the same look as custom crown moulding without all of the hassle.
Drill a 5/32-inch pilot hole though the plastic tabs on the moulding so that the screws go easily through the moulding.
Find the studs in the wall with a stud finder. Mark the location of each stud with a pencil. Try to screw the moulding tabs into the studs whenever possible.
Install the corner blocks. Line up the plastic block with the ceiling and wall. Screw the block to the wall through the plastic tabs. Do not sink the screw too far into the wall or it could crack the plastic tab.
Measure the distance on the wall between the blocks. Mark this distance on the plastic length of moulding.
Cut the plastic moulding to size with a mitre or hand saw.
Apply adhesive caulk on the back of the plastic moulding in an "s" pattern.
Slide the moulding into place between the blocks. Use a friend to help you do this when you are working with long lengths of moulding.
Screw the length of the moulding in place with a 2-inch trim-head screw. Screw the moulding directly to the studs in the wall.
Fill the screw holes with paintable caulk. Let the caulk dry and then paint.