Pleating is the systematic folding of fabric. Pleats are held in place by stitching across the top. You can also stitch partially down the pleat fold lines. The most common types are accordion pleats, knife pleats and box pleats.
Pleats are not for beginners and they can take a bit of planning. There are many things to take into consideration before you begin sewing.
Accordion pleats are the least complicated type of pleat and they are easy to recognize. They look like the bellows of an accordion.
These pleats are symmetrical. Both sides of the pleat are the same length. Accordion pleats do not require any extra fabric to make, because they are not sewn closed at the top.
Accordion pleats are commonly found on circular skirts. The pleat lines are spaced much closer together at the top than at the bottom.
Knife Pleats, also called Side Pleats, are folds in the fabric that all lay to one side or direction.
Note that one side of the "V" is longer than the other, unlike an accordion pleat that is the same length on each side.
You will have to add fabric to your pattern, if you want to add knife pleats. The amount of fabric to add depends on the depth of your pleat. The orange area in the image above indicates all the extra fabric needed to make the pleat.
Pleated skirts can use a lot of fabric and take some patience to create.
Box pleats are found a lot in upholstery work to allow expansion at corners. A box pleat is two knife pleats that face each other.
Box pleats require twice as much extra fabric as one knife pleat. Again, the orange segment indicates the extra fabric needed.
Box pleats are often used at the center back of a men’s shirt to allow expansion through the back.