DIY Installing Crown Molding

This page offers illustrated, step–by–step instructions for cutting and installing crown molding. Angles and compound miter saw settings for cutting standard 52° crown molding are included.

Installing crown molding is an excellent way to dramatically improve the appearance of a room with minimal effort. However, the angles of cut required to install crown molding can be difficult for some do–it–yourselfer's to master. Fortunately, a compound miter saw makes cutting these complicated angles as simple as setting two guides on the saw.

To form the angles required to install crown molding, the wood must be cut in two directions at once; first it must be beveled and second it must be mitered.

A compound miter saw makes it possible to make these cuts with the molding laying flat on the saw table. These saws will have a stop on the bevel and miter guides for setting the proper angles of cut. A gauge on the back of the saw sets the bevel position of the blade and the table pivots left and right to set the miter position.

The following crown molding installation process is for standard crown molding with a 52° angle on the top, ceiling edge and a 38° angle on the bottom, wall edge like the ones here.

Setting the Saw

Set the saw by tilting the blade and setting the bevel angle at 33.86° using the guide on the back. Leave the bevel setting at this position thru–out this molding installation procedure. Some compound miter saws have a double bevel feature. This means the saw blade can be tilted left and right instead of just to one side. When using a double bevel saw for the following procedure, use only the left bevel position.

Set the miter angle by moving the saw table left and right of center. The position will alternate depending on which corner piece of molding will be cut. Set the saw table at 31.62° right to cut the molding that will form the right inside and left outside corners, pieces C and D pictured here. Cut these pieces with the molding's ceiling edge against the saw fence.

To set the saw for the matching pieces, slide the saw table to the left and set it at 31.62°. With this setting the left inside and right outside corner moldings, pieces A and B, can be cut. Turn the molding so the wall edge is against the fence to make these cuts. Notice that the inside corner moldings, A and C, will always be on the left of the blade and the outside corner moldings, B and D, will always be on the right.

Cutting Inside Molding Corners

Starting at the right corner of one wall, measure to the next corner. Have a helper hold one end of a tape measure to get an accurate measurement. Use this measurement to choose a piece of molding to run the length of the wall. If one is not available, see Combine Two Pieces of Molding below.

Cut the right end of the molding to form piece C using the settings for a right inside–left outside corner. Place the ceiling edge of the molding against the saw fence and make the cut. Leave the molding flat on the saw to measure and mark the opposite end.

All measurements for inside corners should be made using the wall edge of the molding as the reference. Hook a tape measure over the end of the molding and mark the other end with a thin pencil mark. Set the saw to cut piece A at the opposite end of the molding by sliding the table to the left and setting it at 31.62°. Leave the blade bevel set at 33.86°. Place the wall edge of the molding against the saw fence and site along the blade to line it up and cut the wall edge just outside the mark. Install the molding using the instruction below.

Cutting Outside Molding Corners

All measurements for outside corners should be made using the ceiling edge of the molding as the reference. To cut a left outside corner, piece D, slide the saw table to the right and set it at 31.62°, leave the blade bevel set at 33.86°. Place the ceiling edge of the molding against the saw fence and site along the blade to line it up and cut the molding just outside the mark on the ceiling edge.

To cut a right outside corner, piece B, slide the saw table to the lefts and set it at 31.62°. Measure and mark the ceiling edge of the molding. Set the wall edge against the saw fence and line up the blade. Cut just to the outside of the mark on the ceiling edge. Check the molding for a good fit.

Finished Outside Corners

To terminate the molding at the end of a wall, measure the wall and subtract an eighth inch. Cut a piece of molding with the appropriate outside corner to this length. Install the molding using the instructions below.

Cut the matching outside corner using a short piece of leftover molding. Be sure the piece is long enough to cut safely with the saw and cut the matching corner on one end. Measure the distance from the wall to the ceiling edge of the installed molding and cut the other end at 90° to fit flat against the wall.

Caulk the corner edge of the molding and mate it with the longer piece. Drive 1 ½ inch finishing nails at the corner to join the two pieces.

Correcting Cutting Mistakes:

If the molding piece you've cut is just a little too long, trim it by a saw blade's width or less and try the fit again, otherwise measure the wall again and measure the molding to determine where to trim it to correct the error. If the molding is too short, caulk can be used to fill small gaps. If there is a large gap in the joint, cut a new piece of molding to correct the error. Salvage the short piece by joining it with another piece or use it for short runs.

Combine Two Pieces of Molding:

If two pieces of molding will be needed to run the full length of a wall, they should be joined with a mitered joint rather than a straight, butt joint. A mitered joint will blend the two pieces of molding together so that the union is undetectable.

To join the two pieces set the saw for a right inside–left outside corner. Place the ceiling edge of the molding against the fence and slide the right end under the blade. Cut the molding to form piece C. Cut the second piece to be joined setting the ceiling edge against the fence and slide it so the left end is under the blade to cut piece D. Temporarily join the two pieces on a flat surface to measure and mark them for installation.

Preparing to Install the Molding:

Locate and mark wall studs and ceiling joists using a pencil. To find the framing, tap across the wall or ceiling and listen for a difference in the sound produced. In general a hollow sound indicates a space behind the wall. The difference between the hollow sound and the sharper sound of hitting the wall over the frame, gives one a rough idea of the location of the stud or joist. Use a drill and an eighth inch bit to bore into the wall where you expect to find the stud or joist. If the drill passes straight thru missing the framing, keep drilling at one inch intervals until you hit wood.

Before installation, caulk along the two edges of the molding that make contact with the wall and ceiling. This will ensure that the molding stays in place and will also serve to fill gaps between the molding and rough or irregular surfaces. Caulk may also be applied to corners when joining the molding. Use these caulking techniques to smooth out excess caulk that squeezes onto the walls and ceiling.

Driving Nails:

While holding the molding in place drive finishing nails thru the molding and into the wall and ceiling framing. Nailing the molding in place will be much easier with the use of a pneumatic nail gun. A finish nail gun with a mid–range capacity of 1½ to 2½ inches is a good choice for this and most other molding projects. If no nail gun is available, drill pilot holes and drive 2½ inch finishing nails with a hammer. Counter sink the nail heads and fill them with painter's putty before painting.

Installing the Molding:

Install the molding holding it up and shifting the placement until the edges lay flat against both the wall and the ceiling surfaces. Drive a nail thru the molding and into the wall and ceiling about 2 feet out from each corner. Leave the ends loose to allow for adjustments when joining the matching corner piece. Drive nails at about 16 inch intervals into the wall and ceiling to secure the middle of the molding. Some nails can be driven into the plaster or drywall but these should be kept to a minimum. To ensure that the molding stays in place be sure nails are driven into wood framing at regular intervals across the wall and ceiling.

Join the molding at corners adjusting the two piece together until they form a smooth union that lays flat against the walls and ceiling. Nail both pieces of molding to the walls and ceiling at the corner. Smooth out any caulk that squeezes from between the two pieces of molding before it has time to set.

A Word About Measurements:

When measuring walls at inside corners it can be hard to know exactly what point to use as the reference point. Most plaster and drywall corners are rounded and it can be difficult to get an accurate measurement. To avoid cutting the molding too short, always used the most extreme point as the reference point. The molding can always be trimmed slightly if it turns out to be a bit long when installing.