Fullness depends somewhat on the fabric and the style of pleats. The rule of thumb for most fabrics is that the finished curtains measure two-and-a-half times the width of the window, but for sheers and silk, designers often prefer three times for fullness.
Box pleats generally require fabric three times the length of the curtain rod for the correct fullness, while a flatter style of panel, such as a scalloped top or grommeted panel may need only one-and-a-half times the curtain rod length.
Designers often put as much thought and custom detail into the hardware as they do the curtain panels themselves.
Designer Mitchell Brown says, "You want to have rods and rings that are in proportion to the size of the room and windows. In a generous room, that might mean a three-inch-diameter rod. There's nothing worse than skimpy rods and rings that look like they don't support the weight of the curtains."
Despite the popularity of this type of window (a large center window topped by an arched window and flanked by two side panels), designers agree that Palladian windows are one of their biggest challenges.
If the window cannot be left uncovered, curtains can be hung above the arch. The consensus is that the rod should not be hung at the bottom of the arch because that bisects the window.
Another option for arched windows is to hang a soft shade or swag that follows the curve, with matching shades on the adjacent windows. Thomas Jayne suggests using a curtain similar in color to the walls so it blends in rather than calls attention to itself.
Curtains should completely clear the doors so they can open. Or mount Roman shades onto each door. Thomas Jayne once designed flat panels with buttonholes that attached to small brass cleats.
If a wall or room is lined with pairs of French doors, consider running a rod all the way across the wall, or a track all the way around the room, and flanking each set of doors with curtains. "What you don't want to do is have one long valance and one set of curtains for multiple sets of French doors," says Cathy Kincaid.
"Hang draperies from the ceiling or just below the crown molding to lift the eye and make a small space or low ceiling appear larger."- William R. Eubanks Designer
Cathy Kincaid suggests shortening the valance to no more than 10 inches if the ceilings are low.
Although windows are a natural home for curtains, a room can benefit from the same soft expanse of fabric in other places. Here, designers suggest some of their favorite unexpected uses.
"When you really need to change a room, put curtains around the perimeter of the room, and then use tiebacks for all the openings-doorways, windows, bookcases. You can use draperies to flank columns or a mirrored wall to create symmetry where it doesn't exist." - William Diamond