-- Stain-Grade: Clear lumber suited to translucent finishes that show the grain -- relatively free of knots and other imperfections. Pine, maple, and red oak are the most commonly available wood species.
-- Paint-Grade: Lumber intended to receive an opaque finish, which conceals imperfections. Lesser grades of pine are typically used here, including finger-jointed moldings that consist of multiple short lengths of stock pieced together.
-- Engineered: Compressed fiberboard profiles covered with vinyl or wood veneers or primed to accept paint are readily available. High-density polyurethane profiles feature a smooth primer-coated skin and are stable and lightweight.
Cut and Fit
Cut and fit the molding for one section of the room at a time, starting at an outside corner. Most right-handers prefer to work counterclockwise around a room.
Attach the molding as you go so you don't confuse placement of the pieces. Drill pilot holes in the molding every 16 inches. Use a hammer and finishing nails to attach the molding to the wall. With the hammer and nail set, lightly countersink the finishing nails. Better yet, use a pneumatic finish nailer, shown, which you can operate with one hand while supporting the molding with the other.
Caulk nail holes, joint gaps, and seams where the molding meets the wall. Fill the holes with caulk and smooth with a putty knife. Squeeze a bead at gaps and seams. Smooth the bead with your finger and wipe away any excess. Let dry, then touch up with paint. Caulk minimizes imperfections, but is for painted molding only.
Tip: Paintable latex caulk is great because you can clean up smears with a rag and water.
Bevel cuts are diagonal cuts across the face of a flat piece of trim, especially at outside corners for baseboard or chair rails. Bevel cuts join the pieces of molding that form the frames.
Miter cuts are used for outside corners, joining two pieces of trim with the ends cut at an angle. To make an outside corner, cut a 45-degree angle on one piece of trim with the saw blade angled to the left and one 45-degree angle on the second piece with the saw blade angled to the right.
Compound Miter Cut
Possible with some compound miter saws, the cut is both mitered and beveled. It's used to cut wide crown moldings that are too large to nest upright on a miter saw base, and it allows you to cut corners with the molding laid flat on the table saw and without reversing the board.
What is Coping?
Coping is the cutting of a contoured end to match the curved profile of a neighboring piece of molding. You'll cut away some of the angled end, following the contours of the profile, so it can nest against the face of its neighbor. The first step is to make a miter cut.
Using the Tool
Use a coping saw to cut away the bulk of the material at the angled end, following the profile. Cut just shy of the contour line, leaving a little of the end grain exposed.
Use files to do the final shaping, test-fitting the piece as you work. A slightly recessed (back-cut) angle on the end grain will help ensure a snug fit on the front.
Tip: Use the trim-and-try-again method. Cut boards a little long, test fit, and nibble at the board end as needed.
Test to make sure you have a tight fit for a smooth joint -- the line where the molding's curved face meets the end grain of the miter cut. That line is the shape of the molding profile.
-- Before installing, inspect the side and head jambs, the boards that line the edges in the wall opening and run perpendicular to the casing. The jamb edges should be flush with the wall surfaces.
--Leave a narrow portion (less than 1/4 inch) of the jamb edges exposed, this is the reveal.
-- Fit the lower trim components first. For doors, this means the plinth blocks at the base. For windows, it means installing the stool (horizontal shelf) and apron (vertical piece beneath window) before fitting the side jambs.
This head casing tops off the door opening. The jamb casings (vertical) are made from 1 X 4 stock with rounded or radiused edges. They are cut square at the top then capped with a thin bullnose trim piece. Atop this sits another 1 X 4, with square edges intact.
This plinth block (an excellent aid to novice carpenters) at the base of door casing is where the side casing and baseboard meet. The moldings are cut square to butt against the plinth.
If the Shoe Fits
The gap where baseboard and floor meet is covered by a small piece of quarter-round molding known as a shoe.
Back to Basics
This one-piece casing style, with a tapered and curved profile, is inexpensive and easy to install. The corners are mitered.
This two-piece casing features 1 X 4 square-edge stock, butted together at the corners, then trimmed around the outside with an L-shape molding, mitered at the corners.
Quick and Easy
This casing features fluted profiles that require only square cuts to butt against decorative rosette blocks.
Test-fit outside corner pieces to reveal a gap that shows how much you'll need to adjust one of the angle cuts to compensate for the not-quite-square corner. If the joint is open on the outside as shown, cut both pieces at slightly less than 45 degrees. If the joints open at the back, cut both pieces at slightly more than 45 degrees.
For long wall sections that require multiple lengths of stock, splice the molding using a scarf joint, a simple overlapping of 45-degree bevel ends, positioned at a stud. Here, the left side of the joint is beveled away from the walls. The right side is beveled toward the wall. Attach the left piece and test fit the right piece. Apply wood glue and press the joint together. Drill two pilot holes through both ends (slightly angled into the joint), start the nails, and drive them in.