How To Install Trim To A Cove Ceiling

by Darwin Hall

cove ceiling trim molding

In a home I’m remodeling, I wanted to replace the old trim molding that was at the top of the wall.

It had a thin, crown-type trim, and I wish to duplicate it.

The trim I picked resembles regular crown molding, with a groove at the top and a groove cut at the bottom of the piece.

The trim is completely flat on the back of the piece, which is perfect for a wall near a cove ceiling.

If you look at a piece of crown molding, it has two angled cuts on the backside of it, which allows you to fasten it to the wall and the ceiling of a square room.

Since the ceiling I’m working on is a cove-style commonly found in older homes, it obviously won’t work for this installation.

Trim at the top of a wall really defines the room and ceiling, adding visual contrast.  After you install the trim, you can to paint the ceiling one color and the walls another.

See also:  Using Moldings To Finish A Room

The molding I chose is a general purpose variety, milled from pine, that is sold un-primed – so I’ll have to prep it.  Here’s how to install the wall trim:

Step 1

The first thing to do is to prime the back of all the trim.  I set up a pair of sawhorses and place all the pieces on them.  Regular water-based primer is all that you need.

The reason for priming the backside is to minimize shrinkage caused by humidity changes in the room.  The wood won’t contract as much, which could pull seams away from each other later down the road – creating gaps where one piece joins another.

crown-type cove ceiling trim

cove ceiling trim

Priming also also allows the finish nails to not split the wood from the power of a nail gun.

I let the primer dry a bit on the back before flipping all of the pieces over to paint the front of them.  I check the edges of the moldings and brush down any build-up primer.

Step 2

While the primer is still drying, I prepare the room by moving furniture and other stuff to the center of the room.  For the stuff that you can’t move, you’ll need to reach those areas with a step ladder.

Pick a corner to start.  You’ll need a miter saw to cut inside or outside corner angles.  To determine the angle at which to cut the wood, start by cutting a 45° miter on the ends of two pieces.

Place the two pieces, butted up against each other, on the wall.  A good rule of thumb is to place the molding 6 inches down from the height of the cove ceiling.  You can adjust this distance however, to fit your needs.

cove ceiling trim - corner

The two butted pieces should fit damn near perfect with each other.  If the top or bottom of the pieces show more than 1/8 gap between them, you’ll need to adjust the bottom rail of the saw and/or the angle of the cut.  It’s trial and error.  The goal is to get a fair meeting of the two piece’s end cuts in the corner.  Later, caulk will be applied to cover imperfections.

You also may need to cut off a small portion of wood from the back of each inside corner piece you miter because of the slope of the cove.  Use a coping saw to do it.

Step 3

After getting two inside corner ends cut at angles to fit decent, the next step is to install one side.  But before you install it, cut the opposite end at a 45° miter if the piece won’t reach the other end of the wall.  The trim I chose only comes in 8 foot lengths.  The walls I’m installing it on are wider than 9 feet, so I’ll need to create a scarf joint.

scarf joint ceiling trimA scarf joint is used to attach two pieces of linear molding.  Each piece of a scarf joint has a 45 degree cut.

These pieces are then butted up against each other with wood glue.  The glue is to secure the seam so it won’t break later from expansion and contraction.

You will never even see the joint when it’s sanded and painted!

Starting at an inside corner, install the piece of pre-cut molding to the wall at your chosen height, using a 4 foot level sitting atop of it.

A good idea now is to use a scrap piece of molding on the other wall to determine exact placement of the first piece.

Tack the piece in place using a compressor and finish nailer.  The nails should be 2 to 2 ½ inches in length.  If you don’t have a nailer-compressor combo, simply purchase a box or two of 2 ½ inch finish nails and nail the piece to the wall with a hammer.

You’ll need to counter-sink the nails later with an awe.  Be careful when hammering the nails; make them flush to the surface without denting the wood.

Before you put in the second nail, make sure to check that the piece is completely level.  Then nail the piece along the length, placing a nail 8 to 10 inches apart from each other.  Do not place nails into any of the grooves of the molding, because it will be harder to sand out once you cover the hole with putty.  Just nail to the flat part of the trim.

Every piece of molding after this first piece will be installed in a left to right way, using your level on each piece, with the goal of ending up in a perfectly leveled square room of wall trim.

Another way to install this trim is by snapping a chalk line around the circumference of the room, then installing the pieces to the line.  It really depends on your comfort level in which way will work for you.

Step 4

Get ready to set the second piece of molding next to the first piece.  Cut the inside corner end first, for the furthest wall end.

Then cut the next wall piece to make sure they butt up against each other in an angle.  Once everything fits, drop the piece and note the location of the scarf cut from the first piece.  Make a mark on it for the scarf with a pencil and cut it at 45°.

Set the second piece into place and check it for fit.  Adjust the scarf cut on the piece as necessary, shaving off small increments with your miter saw until the two pieces fit flush to one another.

Dab carpenter’s glue on the ends of the scarf joints and press them together.  Level this second piece of trim molding and place finish nails into it to secure it.  Continue along the entire room left to right, leveling each piece and adding scarf joints were needed.

For outside corners, place a piece against the wall, mark where the corner is on the trim and cut a 45 degree angle at the ends of two pieces, then level and secure those to the wall.

Step 5

Next, fill all nail holes with plastic wood putty.  Then caulk the bottom of the trim with a good quality painter’s caulk.  There is no need to caulk the top of the trim; it won’t be seen by anyone.

Apply a thin bead of caulk to inside corners and use a caulking tool or piece of cardboard to remove the excess caulk.  Get it as perfect as you can.

For outside corners, apply wood putty liberally along the pointed edge.  Let the caulk and wood putty cure for a few hours.

Step 6

Prepare to sand the putty with a palm sander.  This tool for sanding wood is best and makes fast work of the trim in a large room.  I like to start out with coarse sandpaper, then switch to smooth paper if I think I need to.

cove trim molding kitchen

living room trim sanded

Sand all wood filler nail holes smooth to the surface of the wood.  Use a flashlight held at a slight angle to check your work.  Don’t forget to sand any outside corners.

Scarf joints will require a little more sanding than most other areas.  Sand the joints to the bare wood, while being careful not to distort the molding’s groove lines.

Step 7

Paint the trim moldings.  Start at a corner and paint left to right.  Stroke paint on the other corner molding in the opposite direction (right-to-left),  then go back to the first piece of trim and continue left-to-right along the entire room.

cove trim molding painted

cove ceiling trim molding room

You can block the ceiling area from mistakes with a piece of a cardboard held in your free hand while you paint the trim with the other hand.  An old cardboard box makes a good paint blocking tool.  Cut a box flap off with a utility knife.  Use the straightest side as a way to eliminate the paint getting on the ceiling.  To protect the bottom of the trim, use blue painter’s tape to mask the wall under the molding.

Finally, most trim should be painted with semi-gloss or a gloss finish.  You’ll need two coats to get adequate coverage.  Good luck!

Tools You’ll Need:

Materials:

Dotted Line Post Separator

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