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How To Install Three-Piece Crown Molding: Creating a Foundation With Rail Trim
Fastening crown molding directly to walls can be a headache, but well-fastened rail trim makes nailing the crown fool-proof. Use construction adhesive on all rail—even where you can nail into studs and ceiling joists. That way, you can use just enough nails to hold the trim in place until the adhesive sets, and you’ll have fewer nail holes to fill. Apply the adhesive lightly so the excess doesn’t squeeze out and make a mess.
Miter the ceiling rails at both inside and outside corners. The corners of a room usually aren’t perfectly square, so you’ll have to use test pieces to find the exact angle for each corner. The crown molding tips and techniques shown in the rest of this article will help you install the wall rails. The wall rails are mitered at outside corners and coped at inside corners. Coping the wall rails is just like coping the crown except that you stand the trim upright against the saw’s fence when you make the 45-degree miter.
Customize Your Saw to Miter the Crown
Make square cuts with the crown lying flat on the miter saw’s bed. To make miter cuts for copes and outside corners, you have to lean the crown molding—tilted at exactly the correct angle—against the saw’s fence. Pencil lines on the bed or fence can help you position the crown right, but fence extensions and stop blocks make positioning fast and fool-proof. If your fence doesn’t already have holes that let you screw on extensions, you can drill holes. Or you can fasten the extensions with hot-melt glue and pry them off later. Besides providing a taller fence if needed, the extensions let you screw on stop blocks.
Why Cope?
You’re probably wondering why you should go through the slow, fussy process of coping when you could just miter trim at inside corners. The answer is that wall corners are never quite square, and coped joints fit tight even when corners are badly out of square. Whether you’re installing crown molding, chair rails or baseboard, coping is faster than finding the right miter angle through trial and error. If you really want to avoid coping, use corner blocks (available at most home centers and lumberyards). With these decorative blocks placed at inside and outside corners, you only need to make square cuts.
Coping Isn’t as Hard as It Looks
Coping starts with a 45-degree cut on the miter saw, just as if you were going to make a miter joint at the inside corner.
This cut leaves an edge along the face of the trim that acts as a guideline for your coping saw. Cut along that edge and the resulting shape will fit against an adjoining piece of crown. Chances are your first attempt won’t turn out perfectly, but after a couple of practice runs you’ll be able to make good-looking inside corners. Here are some tips for smooth, successful coping:
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Every time you cut a miter (whether for coping or outside corners), you’ll set the crown upside down against the saw’s fence. It’s easy to get confused and cut the angle backward. To avoid mishaps, hold the molding up to the corner and draw a slash showing the direction of the cut.
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Clamp the molding to the work surface. Sawing is a lot easier with the molding locked into place.
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If the saw blade tends to slide to one side as you start a cut, make a small starter notch with a utility knife.
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Make sure the teeth in your coping saw point toward the handle. That way, the blade will cut smoothly on the pull stroke.
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Don’t force the saw forward. Make even strokes, apply only light pressure and let the blade advance at its own pace.
Shave Pieces on the Miter Saw for a Snug Fit
Making a piece of crown fit between two inside corners is a combination of careful measuring and trial and error:
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Don’t bend the tape measure into a corner and guesstimate the measurement. Instead, measure in from both corners and add the two measurements.
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Make a square cut on the end of the molding. Don’t assume the factory cut is square.
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To prepare for coping, measure from the square end and mark the miter cut position on the bottom edge of the crown molding.
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Don’t make your miter cut exactly at the mark. Instead, cut the piece about a nickel’s thickness too long.
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“Spring” the molding into place. If it’s too long, shave a hair off the square end and try again until it fits just right.
Four Fussy Spots:
Outside Corners
The joint at an outside corner is formed by two simple miter cuts, but making them fit takes several steps. Don’t rush the process—outside corners are usually prominent and so are mistakes. If the crown will have a varnish finish, select two pieces with similar grain patterns.
Double Copes
If your room doesn’t have any outside corners or require scarf joints, you’ll finish the job with a piece that’s coped on both ends. This isn’t as tough as you might think. The key is to start with a piece that’s mitered to the right length. Miter both ends and hold the piece in place to check the fit. Then cope the ends as usual.
Scarf Joints
On a wall that’s too long for a single piece of molding, you’ll have to “scarf ” pieces together. The angled cuts of a scarf joint are less visible than square cuts. If you plan on a varnish finish, select pieces that have similar color and grain patterns. Cut and install the longer piece first so the shorter piece can overlap it at the joint. Glue the joint.
Odd-Angle Corners
Coped joints only work in square corners. If you have non-square inside corners—such as 45-degree corners in a window bay—you have to miter them. Find the correct angle for each corner. Treat odd-angle outside corners just like square outside corners.
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