How to make a Window Valance
The home carpenter can make a wood valance (or cornice) which will make the window, its curtains and draperies much more attractive. Adding a valance to a window is like putting on a lovely hat to set off a costume. For the purpose you can use shelving wood or plywood. A composition wallboard can also be used, but it won't be so strong and might need a wood frame to back it; thus, the effort and time might not be worth it, and you might find it better to use wood.
The size of the valance depends on the size of the window. A tall narrow window needs a deeper and wider valance (a short wide window should have a narrow valance) in each case it should be kept in proportion. The design of the valance also depends on the type of room, curtains or draperies. In a modern room, with simple decoration, a straight board with no design is best. But in a more formal room, with heavier draperies, you could saw the bottom edge of the valance in a scallop or other design. No matter what size or design of valance you select, make certain it is not too conspicuous so that it makes the window look too cumbersome, and that its actual weight is not so heavy that it produces a strain on the window molding.
Measure the outside of your window frame, cut the board the same length, or an inch or two wider if you want the valance to extend out a little on both sides. This is good when it's a very narrow window and you want to create the illusion of more width, or when you use heavy draperies which need more room. Then cut two pieces to be used as the sides of the valance. If you desire you can make a "cover" on top of the cornice, of the same wood or composition board. But, to keep your carpentry simpler, this "cover" can be eliminated and the top of the cornice left open.
To attach the cornice to the window frame, nail two wood blocks on each side of frame at top of window, placed in such way that when cornice is attached these two blocks will fit right into the two sides of cornice. Or, if you think the window frame is not strong enough to hold all the weight, the cornice can be attached to the wall itself, with rawl plugs.
If you want to add some trim, get molding that is narrow and of simple design, and nail it around the top and bottom of the valance.
Another effective wood valance is wide molding. Have this cut to length when you buy it at the mill working plant, then miter the joints at the corners. Thus you have a wood valance that carries its own design.
The way you finish the valance is entirely up to your own tastes and decorating scheme. If you make it of soft wood, paint it to harmonize with the color of your draperies, or with the other woodwork. Valances made of hardwood might be left in natural state, unpainted, but covered with a stain and polish. For a modern room, unpainted natural wood is often preferred. Plywood or composition board can also be painted. To be individualistic, in a wallpapered room the same paper can be pasted over the valance to blend with the walls.
If time is at a premium, you may purchase a cornice that is completely ready for you to upholster or stain, in a variety of shapes and sizes. However, you will find that many draperies and curtains are now available with matching fabric cornices, both in modern and traditional patterns. Many people like the "softer" effect of the fabric cornices, and you can often mix and match colors and achieve unique fashion touches.