Tips for Installing Crown Molding
Installing crown molding can be a challenge the first time you try it.. The following
tips were compiled from discussions and information on another site.
Most Finish Carpenters consider it poor form to miter inside corners, they should be
coped. It allows for slight wood movement, and it allows you to perfectly match the
outside corners by allowing some slight leeway in the length of the piece that will be
covered by the cope.
To cut the
inside corners (which are the hard ones), just turn the molding upside down (ceiling
surface flat to the table - see figure 2) and make an inside miter cut. Now don't move a
thing except the waste piece. Sit there and visualize how this piece will cover its mate
(the cope cut - see figure 3).
You will see that if you take a coping saw and keep the blade parallel to the
table, and perpendicular to the molding, you can cut along the molding edge intersection
with the miter cut, and make a perfect cope. To help visualize, take a pencil and blacken
all of the mitered surface. Cut all of this away by cutting along the molding profile.
In practice, make your miter cut a little long, then adjust to fit with whatever it
takes, usually a sharp chisel, sometimes (judiciously) a gouge or rolled coarse sandpaper.
It is also usual to slightly undercut the profile so just the visible edge contacts (see
Then if the cope is carefully cut,
and slightly jammed to its mate, it will essentially self form the last little increment
to fit (see figure 5).
I usually cut any cope cut first, and the other end last, That way if the cope goes
really wrong, it can be re-cut before the stick is too short. It is seldom necessary to
make a cope cut on both ends of a molding if you have planned the room right. When it does
happen, it is usually the last piece, and there will have been ample time to figure how
the ceiling rolls, so to speak, so you can guess pretty well where to compensate. This
brings to mind, of course, Always do your longest runs first; hopefully your closing
pieces will be short ones and you will have three or even four pieces of short end to get
it right without actually wasting anything.
ut my walls aren't really Square?
Most wall/ceiling junctures run somewhere around 92° to 95° on the really bad ones
today. Stick a framing square up and and check the corner at a number of places around the
perimeter of the room. What happens is that even if the framing of the house is square,
(pretty likely) the drywall finishers tape the corner, then bury the tape, then feather
this out into the rest of the surface. So in the corner, the mud may be 3/16" (or
even 1/2") thick, feathered both ways to nothing in 8" to 12", leaving
greater than a true right angle.
Knowing this, A custom shop making millwork often makes the back angle more than 90*
(95* is not untypical-see Figure 1) - you want the top and bottom edges to touch before
the inside edges bottoms out, leaving a gap.
Generally, the ceiling is the reference for the miter angle, so you would want that
surface flat to the table of your Miter Saw. Practically speaking, it may be necessary to
split the difference. Position it by hand, or stick a splinter or paper match somewhere to
keep it from rocking. There a lot of little adjustments you can make if a
joint is almost, but not quite, there. For instance: outside corner to outside corner a
piece is a smidgeon too short (we're talking 1/32's). Plane the inside bottom of the
molding (wall juncture) of the three pieces slightly and the joints will close up because
the corners are brought in closer to the wall. You can't fix a botched job this way, but
you can improve dramatically an "adequate" installation. If the job is botched,
re-cut the pieces while they are still useful for somewhere else, and start over.
Good Luck! If you are looking for a great book on Crown Molding
and Trim Carpentry, check out
Trim Carpentry Techniques by Craig Savage, which covers many of the
"secrets" professionals use to get those nice tight joints.
highly rated, finish carpentry references that provide detailed
information on crown molding installation are the Finish
Carpenter's Manual, by Jim Tolpin and
Finish Carpentry, by Gary Katz.
If you are looking for a source for some truly stunning crown molding, check
out the Rope
Accent Crown Molding at Rockler.com. It is available in paint grade,
cherry, oak or maple.