What is a Valance?
Although valances, like curtains, are classified as window treatments, they are not the same thing as curtains. While curtains cover the entire window, valances cover only the top portion of a window. You can hang a valance on its own for decoration, or you can hang one in front of blinds or curtains to hide unsightly hardware and give your window a complete, professionally decorated look.
Basic Rules of Thumb for Valance Coverage
While exactly how much of your window your valance should cover is a matter of taste, you can follow a few simple rules when determining how long and wide it should be. While some decorators suggest allowing your valance to cover no more than the top one-third of your window's glass, others base valance length on the length of the window's curtains, making valances 1/6 to 1/5 as long as the curtains. Add enough length to your valance so that you can hang it at least two inches above your window and any moldings.
When it comes to width, valances that hang on rods mounted outside the window should be at least two inches wider than the window, including any side moldings, and covering at least an inch of the wall on each side.
More Window Coverage
Decorating rules for valances should not be seen as commandments you must follow. Sometimes using a valance to cover more of your window is a good idea. For example, if you have a window that is too low on the wall, hanging a longer valance closer to the ceiling will give the illusion of a taller window. Also, if you're hanging a valance over curtains that are much wider than the window, the valance must be much wider as well.
Less Window Coverage
Just as there are times when longer or wide valances are useful, there are times when shorter, narrower valances are useful. For example. if your ceilings are low, a shorter valance won't overwhelm the room; the same holds true for a smaller window. Keep scale and proportion in check so that large windows do not overwhelm small valances.