A cornice box - also known as a pelmet in many countries - used to be looked on as old fashioned, but fortunately is now accepted as an option for window treatments.
It has been used successfully in modern and contemporary window schemes, especially when the design is kept reasonably simple. One of its biggest advantages is that it successfully hides all the track fittings, giving a very neat finish to your window decorating.
Where to place it
It's a good idea to give some thought to exactly where you want to fix it so the overall effect will frame the window. If you don't plan ahead and just put it up as an afterthought, you won't get the professional finish you were hoping for.
As with plain tracks, allow enough for your curtains to draw back off the window and hang comfortably. This depends on the thickness of fabric, how many widths you're using, and if you use interlining or not. It's usually anywhere between 6" to 1' 6".
To gauge the height you'll need a rough idea of the shape and dimensions of your cornice box.
The best way is to cut the shape out in paper or cardboard and pin it up over your window. That way you can see if you like the shape, but also how far up it needs to go so you don't cover up too much of your window. Always check your ideas before you put them into practice!
One way of finding out how far up it needs to go, is to stand in the middle of the room and adjust the shape so that it just covers the window frame but not the glass. Then mark where the top of the shape comes on the wall, and that's where you need to fix your board.
This usually gives the best results for this sort of window treatment, but if you feel you need to change it, do so. Always go by what you think looks best.
The best way to fix both curtain track and cornice box is by using a board, about 6" deep and about 1" thick. You can then 'top fix' the track to the underneath of the board (about half way back), and the finished cornice box is pinned to the front of the board.
Lambrequin - just another version
Many people have never heard of this when they dream up their window treatment ideas. It's a useful solution for small windows where you want something more than just a plain treatment. It's most often used in conjunction with a roller or roman shade.
If your window isn't big enough to fit a complicated treatment, then a lambrequin - which is just a cornice box with long sides - can do the job perfectly.
They are normally placed flush with the wall, and just big enough to come up to, or slightly overlap the recess. A simple wood frame attached to the sides of the recess is enough to support the lambrequin.
As you can see from the illustrations, the sides are usually kept quite narrow, enough to hide the sides where the shade finishes.