How to Build Crown Corner Boxes

A crown corner box is a box placed in ceiling corners to avoid difficult crown molding cuts in the corners of rooms. The box allows the crown molding to cut straight, instead of a carpenter having to figure out an upside down and backward cut. Calculating an upside down and backward angled cut is often quite difficult for novice carpenters. Making a crown corner box is not difficult, and it solves the carpenter's problem. Usually, the box is made of two parts that are joined together.

4-by-4-inch board
4-inch finial
Miter saw
Carpenter's glue
Drill
Screws
Screwdriver
Wood fill
Small putty knife

Instructions

- 1
  Take a sample of the crown molding and position the molding on the ceiling. Measure from the front edge of the crown molding to the corner of the ceiling and wall. This is the thickness of the profile of the molding. Your block needs to be at least this deep. For purposes of this example, our molding is 3 1/2 inches to the wall. This means we will use a 4-inch block.
- 2
  Measure the distance down the wall from the ceiling joint. This is the height needed for the block. Usually you will add an inch for a reveal. Cut a piece of 4-by-4-inch board to this height measurement using a miter saw.
- 3
  Place a 4-by-4-inch finial on the saw deck. Measure and mark the center line on each side. Cut the finial in quarters to create a pie-shape base.
- 4
  Position the finial under the block, lining up the flat sides of one corner. Drill pilot holes through the sides of the finial into the block on both sides. Apply carpenter's glue to the bottom of the finial where it connects to the block. Line up the holes and screw the finial to the block. Recess the screw head. Press wood fill into the top of the screw hole to hide the screw using your finger or a small putty knife.

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