In order to cut crown molding correctly for a slanted ceiling, it will need to be cut differently than it would be for a flat or vaulted ceiling. The good news is that this can be accomplished rather easily with accurate measurements and an adjustable miter saw. It is recommended to use several test pieces of crown molding before cutting the actual pieces that you will be installing. One of the most common methods for fitting crown molding to a slanted ceiling is to attach the molding to a filler piece that is in between. When measuring and cutting crown molding pieces, you will also need to take the measurements and angles of filler pieces into account.
Step 1 - Determine the Ceiling Slope
Begin at the joint where the wall and your slanted ceiling meet. You will need to use an angle finder in order to find slope; these tools are available as either manual or digital, and a digital finder can save you time in converting between angle degrees and inches. Place one arm of your angle finder flat against the wall just below the ceiling, and open the angle finder until the second arm is flush against the slope of the roof. Some digital angle finders give you an automatic reading of this slope, while others have buttons to push first in order to find the angle measurement.
Step 2 - Determine Miter Saw Setting
Once you have gotten a correct slope measurement from step one, divide this by two in order to find the angle you will need to set for your miter saw. If your slope results in a divided number with decimals, keep this rounded to one decimal place. For example, a slope of 37 degrees from your angle finder would translate to a setting of 18.5 for your miter saw’s gauge.
Step 3 - Make Test Cuts
It is a good idea to have at least four pieces of scrap molding in order to find the most precise cut for your actual crown molding. Turn your first piece of scrap molding upside down from the way it would look if attached to your ceiling. Adjust your miter saw stops until they hold your scrap piece firmly in place so that it will not slide during cutting. After turning on your miter saw, lower the blade slowly and carefully in order to cut your angle as cleanly as possible.
Step 4 - Fit to Your Ceiling
Once you have cleanly cut through your first scrap piece of crown molding, fit this to your ceiling at the desired angle. If it is not a completely snug fit, repeat steps three and four on additional scrap pieces while making small adjustments to the miter saw’s gauge setting. After you have determined the perfect fit, cut your pieces of crown molding that will be installed at this exact angle.