How to Sew a Lapped Zipper: A Clean, Concealed Closure

A lapped application uses an uneven overlap. One side of the seam allowance is stitched close to the zipper teeth, while the other side extends over it as a lap, hiding the coil entirely. Only the lapped edge is topstitched through to the outside, which is why the finished result shows a single stitching line rather than the two lines of a centered application.

This asymmetry is the defining feature. Deciding which side laps over which matters for consistency: on a center-back seam the lap conventionally sits so the topstitching falls to one predetermined side, and on a left side seam the back laps toward the front.

Start with a seam allowance wide enough to work with; around 1.5 to 2 cm is comfortable. Interface a lightweight or loosely woven fabric along the zipper opening with a narrow strip of fusible so the edge does not stretch or ripple as you stitch. Finish the raw allowance edges before installing the zipper, since access is far easier now than later.

Machine baste the seam closed along the zipper opening at the finished seam allowance, then switch to a permanent stitch below the zipper stop. Press the whole seam open. The basted section holds the opening perfectly aligned while you build the lap, and it pulls out cleanly at the end.

1. 1.Baste the seam closed along the opening and press it open.
2. 2.With the zipper face down on the allowance, stitch the coil to one seam allowance only, close to the teeth.
3. 3.Turn the zipper face up and let a small fold form in that allowance, then edgestitch through the fold and tape to create the underlap.
4. 4.Close the zipper and smooth the lap side flat over it from the outside.
5. 5.Topstitch the lap from the right side, about 1 cm from the seam and across the base, catching the free zipper tape underneath.
6. 6.Remove the basting and press.

The single topstitched line is the only part of the job that shows, so it deserves the most care. Mark it with a chalk line or a strip of low-tack tape as a guide, keeping a consistent distance from the seam. Move the zipper pull out of the way as you approach it by stopping with the needle down, lifting the foot, and sliding the pull past.

Pivot precisely at the base of the zipper to square off the bottom of the lap. A clean right-angle turn there reads as deliberate and professional, whereas a rounded or wandering corner signals a rushed installation.

• Rippling along the opening: stabilize the edge with interfacing and avoid stretching the fabric under the foot.
• Visible zipper coil: the lap is too narrow or the underlap stitching sat too far from the teeth.
• Wavy topstitching: baste the lap first and follow a marked guideline rather than eyeballing it.
• Bulk at the base: trim and grade the seam allowance below the zipper stop before finishing.

A standard coil zipper suits most skirts and dresses; choose one slightly longer than the opening so the pull can be parked clear of the stitching line, then shorten it by bar-tacking across the coil at the required length. Match zipper weight to fabric weight, since a heavy metal zipper distorts a fine cloth.

Placement, opening length and allowance width all originate in the pattern. Minerva Patterns supplies made-to-measure patterns in DXF AAMA, PLT and PDF with zipper openings and notches marked, so the closure sits at the correct point on the seam for the individual garment.