Molding is an important element in the finished appearance of a room. Chair rail molding protects walls from being scuffed by chairs, while crown molding hides gaps between the walls and the ceiling.

Installing molding calls for fairly sophisticated carpentry skills. Gaining these skills is simply a matter of practice: Spend some time cutting and fitting scrap pieces until you feel comfortable with the process. On the whole, chair rail is easier to install than crown molding (see Figure 1).

You will need a miter saw to make precise cuts. For small moldings, an inexpensive miter box and backsaw may be sufficient. For easier cutting and greater precision, purchase a bow saw—a metal frame and a saw that looks like a hacksaw. Or go all the way and buy a power miter saw, also called a chopsaw, which makes the quickest and most precise cuts. Test the saw on scrap pieces to make sure it cuts perfect 90- or 45-degree angles.

There are two basic types of chair rail. One is designed to top off wainscoting; the other rests flat against the wall and is a decorative element by itself. This project shows you how to install the latter type of chair rail.

Measure each wall of the room and buy molding to fit each wall. Purchase finishing nails that will penetrate at least 1½ inches into the wall studs (6d finishing nails generally work). Use a level to draw faint horizontal lines around the room at a height that will be just barely covered by the chair rail. Locate and mark all the studs (Make sure the stud lines will be visible when the molding is in place on the wall.) Stain or paint the molding before you start cutting, then do touch-up work after it's installed.

If the first piece will butt up against a wall on either side, measure and cut it about 1/8 inch too long, so it fits snugly. Ideally, you should have to bend it slightly to get it to fit. Once it's in place and level, drive one or two finishing nails into each stud, so that the molding fits tightly against the wall. Use a nail set to drive the nail head slightly below the surface of the wood.

If possible, do not cut the next piece to length yet (leaving yourself some wiggle room in case you make a mistake). Miter-cut a 45-degree angle where the second piece will butt against the first piece at an inside corner. Then use a coping saw to cut away the back side of the miter cut (see Figure 2). Cut away too much rather than too little, taking care not to cut the visible face of the molding. Test-fit the piece; you may have to cut away a bit more with a knife in order to get a snug fit.

In theory, getting a tight joint at an outside corner should be a simple matter of two 45-degree miter cuts. However, rooms are rarely perfectly square, so take some time to experiment with scrap pieces. You may need to vary the angle of the cut slightly. Once you have a tight fit, attach the pieces to the walls with nails. Wherever a nail will be driven less than 2 inches from the end of a board, drill a pilot hole first, to prevent cracking the molding (see Figure 2.)

Use a nail set to tap all the nail heads slightly below the surface of the wood. Fill the holes with wood putty, using a putty knife or your finger so that the putty extends slightly above the surface of the wood. If you’re installing stained wood, choose putty that matches the color of your stain. Allow the putty to dry, then sand it flush with the surrounding surface. Apply a final coat of paint, or a coat of polyurethane to stained wood.

Crown molding runs along the top of a wall where it meets the ceiling. The wider the molding, the more stately the effect. But because ceilings and walls are rarely perfectly square, crown molding can be tricky to install. You may have to shave off the edges of some pieces and shim out others in order to get tight fits at joints and along ceilings and walls. Take your time, take plenty of breaks, and have a helper hold boards in place for you.

Hold a scrap of crown molding in place at the top of the wall and determine how you will attach it: You might simply drive nails into the top plate of the wall framing or, if you have very wide molding, you may have to install a strip of wood behind the crown molding so you have something to nail to. Another option is to first install straight boards that act as surfaces on which to nail the molding—this can add to the visual interest of the molding and make it easier to hide imperfections in walls and ceilings. If possible, avoid cutting a board to an exact length using a miter cut; wherever possible, cut the miter first, then measure and cut the other, non-mitered, end. Generally, start with the longest piece—though if you have an outside corner, consider first cutting and installing both pieces there. Paint or stain the molding pieces before cutting.

It’s easy to get confused as to the direction of miter cuts. Use the illustration below (Figure 3) as a guide. Determine which side of the molding you want up, and always hold the piece in the same way when making cuts.

Corner joints can be tricky. Many pros experiment by cutting scrap pieces first. When you’re ready, cut both pieces to 45 degrees, and hold them against each other at the corner to see if the fit is tight. You may need to increase the angle of the miter cut a degree or two, or you may need to slip in a small shim to make a tight fit. To prevent cracks, drill pilot holes before driving nails less than 2 inches from the end of a piece of molding.

At an inside corner, cut the first piece square and install it tight to the corner. Cut the second piece at a 45-degree angle. Use a coping saw to cut away all the excess wood behind the profile of the face of the molding. Cut carefully, coming very close to the profile but not cutting into it (see Figure 4). The cut edge should match up with the contours of the piece that’s on the wall. Test-fit and make additional cuts if needed for a tight fit.

Use a nail set to drive the heads of the finish nails slightly below the surface of the wood, and fill the resulting holes with wood putty. Allow to dry, sand smooth, and apply a final coat of paint or polyurethane.