Crown molding installed 601-750-2274 inside corners

Make a 45-degree cut

Inside corners are composed of a square-cut piece that butts the corner, and a corresponding piece that's cut on an angle and coped (carefully cut along the molding's profile) to conform to the first piece.

Begin by installing a piece of crown with a square-cut end (zero degrees on the saw).

Then position a second piece of molding upside down on the saw and adjust the blade for a miter cut. If this piece comes to the joint from the right side as shown in Step 3, swing the blade to 45 degrees left and make the cut. The bulk of the molding should be sitting on the left side of the saw.

If cutting a left-side coped piece, swing the blade to 45 degrees right, with the molding sitting to the right.
Cope the edge

Highlight the very edge of the cut, along the profiled front of the molding, with a pencil.

Next, using a coping saw, cut away the bevel. Angle the coping saw blade toward the rear about 5 degrees — a technique known as back beveling — and carefully follow the molding profile as you cut.

Use the miter saw table to brace the workpiece when cutting.
Check the fit

After completing the coped cut, test-fit it against the square-cut crown that's nailed in place.

If necessary, use a rasp to remove more wood or smooth out the coped cut.

Nail the coped molding in place and set the nails.
Cut the return

Where the crown molding doesn't butt ito something, you need to finish it with a return. Cut a 45-degree miter on the end of the crown (as you did for an outside corner) and nail it up. Next, make a 45-degree cut in the opposite direction on another piece.

Adjust the saw to zero degrees and lay the piece flat and face-down on the saw table. You'll need to remove your wood guide fence for this.

Cut through the crown, starting at the very point of the miter.
Complete the return

Bore two pilot holes through the tiny triangular return with a 4d finish nail chucked in your drill.

Apply a thin coat of glue to the return, then press it into place and hold it for a minute or two.

Nail the joint gingerly with 4d nails through the pilot holes only if the glue fails to hold.

Set the nails and fill all nail holes with putty.

Crown molding installed 601-750-2274 outside corners

Determine angle of outside corner

An outside corner can be formed by cutting two pieces of crown with opposite miters of 45 degrees each, making sure both miters are longer on the top of the crown (the part that rests on the saw table when you cut). But sometimes a wall corner isn't exactly square, so you must first measure the angle formed by the two walls and and then bisect it.

To do this, take two pieces of wood of exactly the same width and hold one against each wall, making sure their ends overlap by an inch or so.

Next, draw pencil lines on the face of the upper piece (the one held flat to the ceiling) alongside each edge of the overlapping piece.

Draw a diagonal line to connect two opposite corners of the marks.

Test the angle cuts

Turn the pieces so they are stacked precisely one on top of the other (make sure to put the piece with the pencil lines on top). Then take this stack to the miter saw, put one set of the boards' edges against the saw fence, and adjust the blade angle to match the diagonal line.

Saw through both pieces at the same time along the diagonal line. This cut bisects the angle of the outside corner.

Hold the cut pieces against the ceiling as shown and check for a tight fit. If necessary, mark in which direction the angle is off, adjust the saw to match this corrected angle, reassemble the two boards as before, and cut them. Then test again to be sure.

Cut the outside miter

Mount a piece of crown in the saw (upside down as before), leaving the blade set to the angle used to cut the test scrap. This is the angle you'll use to cut the outside corner.

Because the molding is upside down, if the saw blade is swung to the right, you will be cutting the right-half piece of the joint and you'll need to cut off the right end of the workpiece. If the blade is swung to the left, cut off the left end of the workpiece to complete the left half of the joint.

Once you've cut the first piece, use the test scrap to adjust the blade in the opposite direction and cut the other half of the joint.

Install the molding on the corner

Hold the molding pieces in position at the outside corner and check for a tight fit (left).

Before nailing the molding to the wall, bore two pilot holes through the point of the miter joint. A 4d finish nail chucked into your drill works well here.

Then apply glue to the miter joint and fasten each piece of crown with 6d or 8d finish nails top and bottom.

At the corner joint, tap 4d finish nails through the pilot holes.

Set all the nails.