Most zip problems come from sewing the two sides in opposite directions, which shifts the layers and produces the wave everyone recognises.
The sequence that works.
Baste the seam closed where the zip will go, with a long machine stitch. Press the seam open. Position the zip face down over the basted seam and hand-baste or tape it in place — tape is faster and does not distort the fabric.
Fit the zip foot. It sits to one side of the needle so you can stitch close to the teeth without hitting them.
Sew from the top down on the first side. Then sew from the top down again on the second side — not from the bottom up. Both sides must travel in the same direction or the layers shift relative to each other.
Unpick the basting last. Press.
Two details that decide the result. Stop and lift the foot with the needle down to move the slider out of the way before you reach it; sewing around the slider is what makes the stitching bulge. And interface lightweight fabric behind the zip, or the fabric ripples along the tape.
Choose the right zip. A moulded plastic zip on a fitted waistband fails at the stress point. A metal or coil zip of the right weight outlasts the garment.
Questions people actually ask
My zip always waves.
Almost always because the two sides were sewn in opposite directions. Sew both top to bottom, and baste before you stitch.
Do I really need a zip foot?
Yes. A standard foot cannot get close enough to the teeth without riding on them, and the stitching ends up too far away, which is what makes a zip look home-made.
Last reviewed 2026-08-11