Usually the installation height of wall cabinets in the kitchen is determined by the bottom of the upper cabinets. The top-section over the wall cabinets usually gets filled in to the ceiling with either a starter strip or decorative crown molding. In many cases the space over the cupboards is left open if the distance is at least twelve inches.
read Installation Height Upper Wall Cabinets
I’ve wrestled with how to fix kitchen upper cabinets that have loose crown molding many times. Some cabinet installers only use a small staple to hold the corner joints together. Sometimes they miss the mark just enough to cause the molding to separate and a gap will appear in the corner miter joint over time. This is usually caused by the wood joints expanding and contracting with the temperature changes.
Try getting some Fast Drying Miter Joint Wood Glue to repair the separation with.
Fixing wall cabinet decorative crown can be frustrating because sometimes the installer did not get the miter aligned properly during the original installation. If this is the case, you can really only do the best read How to Fix Loose Crown Molding
