Install Decorative Moulding

• Start by cutting your decorative moulding pieces a little long, you can always trim a little off, but once a piece is too short it can't be fixed.
• Predrill holes for nails to avoid splitting the moulding.
• If you use a power miter saw, use at least a 60 tooth blade.
• In order to establish a level line for a chair rail, measure up from the floor to where the bottom of the chair rail will be and make a mark. Use a level as a straight edge and lightly draw a line around the room. As you install the chair rail, make sure it is even with this line.

Lay the moulding with its back flat against the bottom of the miter box or the bed of the power miter saw. For inside corners, cut through the face at 45° so the edge of the cut is visible from the front. For outside corners, cut through the face at 45° so the edge of the cut is hidden from the front. Cut the pieces as mirrors to each other.

For outside corners, use a power miter saw and set it as indicated in in our crown moulding adjustment table below. For inside corners, you can either miter cut the pieces or cope them.

• To miter the pieces, place the moulding so its top (the part that goes against the ceiling) is flat against the bottom of the miter box or bed of the power miter saw. The bottom (the part that goes against the wall) should be flat against the side of the miter box or the power miter saw's fence. Cut the pieces as mirrors to each other on 45° angles.
• To cope the pieces, butt one piece tight against the wall and nail in place. Place the second piece in your miter box or power miter saw as described above and cut the piece at 45° so the edge of the cut is visible from the front. Use a coping saw to cut a slight back angle following the contour of the exposed moulding profile. Test fit the coped cut and trim as necessary. See the animation below for more information on coping moulding.

When you are covering a span that is longer than your moulding, splice two pieces together with a scarf joint. Lay the moulding with its back flat against the bottom of the miter box or the bed of the power miter saw. On one piece, cut through the face at 45° so the edge of the cut is visible from the front. On the second piece, cut through the face at 45° so the edge of the cut is hidden from the front. The joint should meet over a wall stud or some other point where it can be nailed.

Locate and lightly mark the wall studs.

Measure the distance between two inside corners and cut a piece of moulding to fit between the corners. Predrill the moulding at every wall stud and nail in place. To avoid denting the moulding, use a nail set to finish driving the nails home. You may need someone to help hold long pieces while you drill and nail. In the event you have a span between two corners longer than the moulding, simply make a scarf joint as mentioned above to splice two pieces.

Continue installing pieces until all the moulding is up.

After all the moulding is up, touch up any raw edges with a light coat of finish. Use wood putty or a filler stick to hide nail holes. For crown moulding, it may be necessary to apply a bead of caulk where the moulding meets the ceiling to close any gaps.

Determine how much moulding you need as above.

Count the number of inside corners in the room to determine the number of inside corner blocks you will need. Do the same for the outside corners. Plan on using divider (intermediate) blocks in any wall with a measurement greater than 8'.

Apply the finish as above.

Predrill holes for nails to avoid splitting the moulding or corner blocks. Predrill holes in the inside corner blocks and nail them to the inside corners of the room (see Predrilled Block). Try to drill the holes so the moulding will cover them. If the room has any outside corners, predrill holes in the outside corner blocks and nail them to the outside corners of the room.

Measure the distance between the first two corner blocks. Cut a piece of moulding approximately 1/4" longer than the measurement.

Butt one end of the moulding tight against one of the corner blocks. Lap the other end over the other corner block and trace the edge of the corner block onto the back of the moulding. Take the moulding down and cut it on the outside of the line to ensure a snug fit.

Locate and lightly mark the wall studs. Touch up the raw edges with a light coat of finish and fit it between the corner blocks. Predrill the moulding at every other wall stud and nail into place. To avoid denting the moulding, use a nail set to finish driving the nails home. You may need someone to help hold long pieces while you drill and nail. Continue this process until all the moulding is up. Use wood putty or a filler stick to cover any noticeable holes.

In the event you have a span between two corner blocks longer than the moulding, simply center an intermediate block between the two corner blocks. Install the moulding as you would between corner blocks.

In order to establish a level line for a chair rail, measure up from the floor to where the bottom of the chair rail will be and make a mark. Use a level as a straight edge and lightly draw a line around the room. As you install the chair rail, make sure it is even with this line.