Properly cutting crown molding for a curved wall will both keep the molding intact and secure it to the wall. Some crown molding is made from plastic foam and can be shaped to create a curve to follow the wall.
Step 1 - Cut the Molding
The back of the molding is not a curved shape. It is designed with three flat surfaces. The outermost two are for the adhesive. To create a curved shaped, slice the back of the molding with the utility knife, creating “V” shapes with each cut.
Step 2 - Shape the Molding
With each cut you will note the molding starts to curve naturally. Space the cuts to allow for enough maneuverability, but cut them thin enough to not break through the outer surface. Once you have reached the other end of the molding, your curve should be ready to glue.
Step 3 - Glue the Molding
Apply glue to the molding at the top and bottom and attach it to the angle of the ceiling. Hold the molding in place with three poles. Attach a cloth to each pole to protect the molding and hold it in place while the glue dries. For molding made from other materials, the same principle applies, but for wood you may need to use a jigsaw instead of a utility knife.