Neoprene is thick, spongy and stretchy, so conventional seam allowances stack into ridges. The technique is to reduce bulk rather than enclose it.
Butt the edges together rather than sewing right sides together and turning. Trim the seam allowance off, hold the two cut edges against each other, and join them with a wide zigzag or a three-step zigzag straddling the join. That gives a flat seam with no allowance at all — the method used on wetsuits.
Where you do sew a conventional seam, trim the allowance to 5 mm afterwards and topstitch it flat. Anything thicker rolls and shows through.
Use a stretch or jersey needle, 90/14, and polyester thread. A sharp point cuts the foam.
Use a stitch with give. Neoprene stretches, and a straight stitch across it snaps. A narrow zigzag or a stretch stitch is essential.
Fit a walking foot. The surface is grippy on one side and slick on the other, and the layers will not feed evenly otherwise.
Never press it. It is a foam and it melts and compresses permanently. Roll seams flat with your fingers or a wooden roller.
Edges need no finishing. Neoprene does not fray, so a raw hem is normal and is often the best-looking option — a turned hem is stiff and bulky.
Cut with a rotary cutter against a ruler. Scissors compress the foam and give a wavy edge.
Questions people actually ask
Will my domestic machine cope?
Thin dress-weight neoprene, usually yes. Genuine wetsuit foam is beyond most domestic machines because of the thickness at seam junctions, not the material.
Do I need special thread?
Ordinary polyester is fine and it stretches slightly. Cotton thread has no give and will break along a stretched seam.
Last reviewed 2026-08-11