Ceiling crown molding is a great way to highlight the architectural details of a vaulted ceiling. Once you master the tools and angle theories of cutting crown molding, adding ceiling crown molding to your vaulted ceiling can be a fun home improvement project. For a vaulted ceiling, it is recommended that you install scaffolding to complete the project safely.
Step 1 - Mark Crown Molding Elevation
With a tape measure, determine the height of the chosen ceiling crown molding. Measure the molding height from the ceiling down the wall to determine where the molding will lay on the wall. Mark on the wall where the molding will fasten.
Step 2 - Measure Vault Angles
With an angle-measuring tool, find all requisite angles on the walls at ceiling level. The measuring tool allows accurate angle determination. Set one leg of the tool against each wall making the angle, lock the nut, read the angle. Write measurements down. Indicate whether each angle is an inside or an outside corner. Inside and outside corners are handled differently.
Step 3 - Measure Length of Cuts
Measure the length of each piece of ceiling crown molding. The measurement should be taken at the elevation line marked on the wall in Step 1. This is the length of the bottom of the molding.
Step 4 - Set Up Miter Saw
To cut the molding, place the molding upside down in the miter saw. To assure that every cut is made perfectly, at the same angle, attach a piece of plank snug to the molding wide enough that the saw will not cut through. Be sure that the faces of the molding are set with the wall face at the fence (upright guide on saw table) and the ceiling face is sitting on the base of the saw. This assures a perfect cut. Clamp the board to the table. Alternatively, there are crown-molding jigs available to hold the molding at the perfect angle to achieve an exact cut. Inside corners can be cut with first piece cut straight, to butt into the corner. Cut intersecting piece at 45 degrees (necessary length), mark mitered edge along edge of face. With a coping saw, carefully following the contours of the profile, undercut the molding to fit over the first piece.
Step 5 - Cutting Molding
Choose your starting point, measure and cut appropriate angles at either end. Attach the just cut molding with finish nails (nail gun). If there is a wall that is longer than one piece of molding, ‘scarf’ 2 pieces of molding together at the center of the wall. To do this, undercut each piece at equal and opposite angles (the pieces will slide, or scarf, together flat to the wall). Scarfing the joint will allow for a tighter fit than butt-jointing (cutting the ends straight) and provides a wood surface under the joint for sealing the joint properly. Be sure to lightly sand each miter with 22-grit sandpaper before attaching the ceiling crown molding, and wipe clean with tack cloth.
Step 6 - Finish Joints
For any miters that show a gap, use spackle to fill the joints. Spackle does not shrink, and can be sanded. Also, condition, prime and apply first coat of finish to the molding before attaching to the wall. This will minimize finish work necessary after installation. After all ceiling crown molding has been placed and spackled, apply final finish coat.