Upon completing this section, you should be able to identify the types of interior wood trim and the associated installation procedures.

The casing around the window frames on the interior of a structure should be the same pattern as that used around the interior doorframes. Other trim used for a double-hung window frame includes the sash, stops, stool, and apron (fig. 6-35, view A). Another method of using trim around windows has the entire opening enclosed with casing (fig. 6-35, view B). The stool serves as a filler trim member between the bottom sash rail and the bottom casing.

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Figure 6-35.—Installation of window trim.

The stool is the horizontal trim member that laps the windowsill and extends beyond the casing at the sides, with each end notched against the plastered wall. The apron serves as a finish member below the stool. The window stool is the first piece of window trim to be installed and is notched and fitted against the edge of the jamb and plaster line, with the outside edge being flush against the bottom rail of the window sash. The stool is blind-nailed at the ends so that the casing and the stop cover the nailheads. Prechilling is usually necessary to prevent splitting. The stool should also be nailed at the midpoint of the sill and to the apron with finishing nails. Face-nailing to the sill is sometimes substituted or supplemented with toenailing of the outer edge to the sill.

The window casing should be installed and nailed as described for doorframes (fig. 6-26, view A) except for the inner edge. This edge should be flush with the inner face of the jambs so that the stop covers the joint between the jamb and casing. The window stops are then nailed to the jambs so that the window sash slides smoothly. Channel-type weather stripping often includes full-width metal subjambs into which the upper and lower sash slide, replacing the parting strip. Stops are located against these instead of the sash to provide a small amount of pressure. The apron is cut to a length equal to the outer width of the casing line (fig. 6-35, view A). It should be nailed to the windowsill and to the 2-by 4-inch framing sill below.

When casing is used to finish the bottom of the window frame, as well as the sides and top, the narrow stool butts against the side window jamb. Casing should then be mitered at the bottom comers (fig. 6-3 5, view B) and nailed as previously described.


Base molding serves as a finish between the finished wall and floor. It is available in several widths and forms. Two-piece base consists of a baseboard topped with a small base cap (fig. 6-36, view A). When plaster is not straight and true, the small base molding will conform more closely to the variations than will the wider base alone. A common size for this type of baseboard is 5/8 inch by 3 1/4 inches or wider. One-piece base varies in size from 7/16 inch by 2 1/4 inches to 1/2 inch by 3 1/4 inches and wider (fig. 6-36, views B and C). Although a baseboard is desirable at the junction of the wall and carpeting to serve as a protective bumper, wood trim is sometimes eliminated entirely.

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Figure 6-36.-Base moldings.

Most baseboards are finished with a 1/2-by 3/4-inch base shoe (fig. 6-36, view A). A single base molding without the shoe is sometimes placed at the wall-floor junction, especially where carpeting might be used.

Square-edged baseboard should be installed with a butt joint at the inside comers and a mitered joint at the outside comers (fig. 6-36, view D). It should be nailed to each stud with two 8d finishing nails. Molded single-piece base, base moldings, and base shoe should have a coped joint at the inside corners and a mitered joint at the outside corners. In a coped joint, the first piece is square-cut against the plaster or base and the second piece of molding coped. This is done by sawing a 45 miter cut and using a coping saw to trim the molding along the inner line of the miter (fig. 6-36, view E). The base shoe should be nailed into the baseboard itself. Then, if there is a small amount of shrinkage of the joists, no opening will occur under the shoe.

To butt-join a piece of baseboard to another piece already in place at an inside corner, set the piece to be joined in position on the floor, bring the end against or near the face of the other piece, and take off the line of the face with a scriber (fig. 6-37). Use the same procedure when butting ends of the baseboard against the side casings of the doors.

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Figure 6-37.-Butt-joining baseboard at inside corners.

For miter-joining at an outside comer, proceed as shown in figure 6-38. First, set a marker piece of baseboard across the wall comer, as shown view A, and mark the floor along the edge of the piece. Then set the piece to be mitered in place. Mark the point where the wall corner intersects the top edge and the point where the mark on the floor intersects the bottom edge. Lay 45 lines across the edge from these points to make a 90 corner. Connect these lines with a line across the face (view B), and miter to the lines as indicated.

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Figure 6-38.-Miter-joining at inside corners.

The most economical, and sometimes the quickest, method of installing baseboard is to use vinyl. In addition to its flexibility, it comes with premolded inside and outside corners. When installing vinyl base, follow the manufacturer’s recommended installation procedures for both the base and adhesive.


Ceiling moldings (fig. 6-39) are sometimes used at the junction of the wall and ceiling for an architectural effect or to terminate drywall paneling of gypsum board or wood. As with base moldings, inside corners should be cope-jointed (fig. 6-39, view A). This ensures a tight joint and retains a good fit if there are minor moisture changes.

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Figure 6-39.-Ceiling moldings.

A cutback edge at the outside of the molding (view B) partially conceals any unevenness of the plaster and makes painting easier where there are color changes. For gypsum drywall construction, a small, simple molding (view C) might be desirable. Finish nails should be driven into the upper wall plates and also into the ceiling joists for large molding when possible.


The decorative treatment for interior doors, trim, and other millwork may be painted or given a natural finish with stain, varnish, or other nonpigmented material. The paint or natural finish desired for the woodwork in various rooms often determines the species of wood to be used.

Interior finish to be painted should be smooth, close-grained, and free from pitch streaks. Species meeting these requirements include ponderosa pine, northern white pine, redwood, and spruce. Birch, gum, and yellow poplar are recommended for their hardness and resistance to hard usage. Ash, birch, cherry, maple, oak, and walnut provide a beautiful natural finish decorative treatment. Some require staining to improve appearance.