How to cut and install crown molding
For perfect cuts, practice and use the proper tools.
Even an experienced carpenter can have problems installing crown molding. Material waste is expensive and mistakes can be time-consuming. Worse, a poorly cut joint will detract from the finished interior.
The difficulty is that, unlike window casing or baseboard trim, crown molding only touches the wall at the top and bottom; most of the joint is “floating.” Crown molding is installed flush to the ceiling and wall through the top or “shoulder” and the bottom or “foot.” The finished corner joint requires a coped edge.
To correctly cut and install crown molding, work with a miter saw and a coping saw with a fine blade. The miter saw delivers accurate, uniform cuts at angles between 45° and 90°. CAUTION: Corners are not always 90 degrees. Before cutting crown molding for a corner joint, measure the angle formed by the two walls using an angle finder or a 360-degree adjustable protractor. Divide the angle in half to set the miter saw.
The coping saw uses a thin metal blade held in place in a large C-shaped frame. The thin blade can bend and move to create intricate, fine cuts.
Before making that first cut, cut test pieces of inside and outside corners using scrap molding. Practicing the cuts will reduce the chance for errors and confirm that the corner angles fit correctly.
Follow these steps for crown molding with flawless joints
Cut the first piece of molding square on each end to span an entire length of wall and fit snugly in each corner. The first piece will support the second. On a longer wall, you may have to splice two pieces of molding together using a scarf joint (see sidebar) to span the entire length.
Measure the adjoining wall to determine the length of the next piece, Cut the adjoining end to fit an inside corner using a miter saw. Set the saw at a 45-degree angle and place the molding upside down with the foot of the molding flush against the fence and the shoulder flush against the table. Cut the molding. On an inside corner, the top of the molding will be longer than the bottom.
Position the piece on the wall to make sure the length is correct. The molding will not fit flush with the installed piece until the end has been coped.
To fit the inside corner joint, use the coping saw to cut away the exposed wood just below the surface at the 45-degree cut. Marking the edge on the face with a pencil will make it easier to see the cut line. Angle the saw away from the molding surface as you cut, taking small “bites” out of the joint end until the entire end is coped.
Put the coped molding in place and check for a tight fit. If there are gaps, carefully remove high spots with the coping saw until the edge fits flush in the joint. Nail the molding in place through the foot and shoulder (not the center).
If a wall ends in an outside corner, cut an outside corner joint. For best results, practice by cutting the corner joint from scrap molding. Make an outside miter cut on one piece, rotate the saw blade to the opposite 45-degree angle and cut the second scrap piece. Glue and nail the ends together. Position the mockup at the outside corner and mark the ceiling where the pieces come together.
Measure from the top edge of the piece you’ll be connecting to—which is already installed on the wall—to the mark you made on the ceiling. Set the saw at 45 degrees and cut the molding. On an outside corner, the top of the molding will be shorter than the bottom.
Cutting crown molding to create flawless joints takes practice and patience, but the extra effort will help produce a superior result.
Cutting a scarf joint
To span the length of a wall, it may be necessary to splice two pieces of molding. First, measure the length from wall to wall and decide where to locate the scarf joint, usually over a stud. Cut the first piece of molding to the desired length and then cut a 45-degree using a miter saw, holding the piece to the right of the blade. Measure and cut the second piece and cut a 45-degree angle by holding the piece to the left of the blade.
Place the first piece on the wall with the angle facing into the room and nail it in place. Then position the second piece to overlap the first and nail it into place. Use a small amount of wood glue to seal the joint.