Zippers & Hardware
The hardware you choose decides how you draft the opening. The wrong seam allowance, or no clearance for the hardware, makes zippers buckle and lets metal show along the finished edge.
Zipper Seam Allowances
A zipper seam does not follow the usual seam allowance. What it needs depends on how you plan to put the zipper in.
| Zipper | Seam Allowance | Notes |
|---|---|---|
| Centered or Lapped | 3/4" to 1" (19 to 25 mm) along the zipper opening | The lapped overlap needs the full width to hide the teeth without pulling the seam. |
| Invisible | 5/8" (16 mm) on both edges | The zipper is stitched right next to the coils, so no extra overlap is needed. |
| Exposed | None. You remove width from the pattern. | See below. |
Wherever the zipper goes, add the wider allowance along the length of the zipper, then let the seam jog back to 1/2" (13 mm) below the zipper stop.
In PatternMaker Pro, use the Change Line/Curve Seam Allowance tool to give a line or curve a custom value. The automatic Add Seam Allowance tool then uses that distance when it builds the pattern.
Centered and Lapped Zippers
For a centered or lapped zipper, keep the allowance wide along the opening. Use 3/4" or 1" (19 or 25 mm). Pick one and use it every time, so you do not have to think about it.
Make the opening as long as the zipper teeth, so the bottom stop is barely hidden.
Invisible Zippers
An invisible zipper has no stitching showing on the outside, which is why it is so popular in dresses and skirts. Draft a 5/8" (16 mm) allowance on both edges, and buy the zipper a little longer than you need, about 5/8" (16 mm), because some of the length is used up when you put it in.
- Stop Marks: Mark where the bottom of the zipper stop sits, so the seam below it lines up.
Invisible zippers work well in knits. With no topstitching, there is nothing to stretch the fabric out of shape.
Use the Add Alignment Marks tool in PatternMaker Pro to make your pattern annotations.
Exposed Zippers
An exposed zipper shows the tape and teeth as part of the design.
- No Seam Allowance: The teeth add width to the garment. To make up for it, measure the width of the teeth and remove half of that from each side of the opening on the pattern.
- Slash Opening: If you put the zipper into a slash opening where there is no seam, draft a rectangular window for the teeth and the visible tape. A fabric patch (a stay) is stitched behind the opening first. It steadies the opening, stops raveling, and cuts down on bulk.
Hidden Zipper Plackets
A hidden zipper placket uses a fly-like fold, or guard, to cover a heavy-duty zipper completely. You see it on jackets, coats and decorative closures.
Drafting a Placket Extension
- Find the Center Line: Locate the center front or center back seamline on your draft.
- Draft the Underlap on One Side: Extend the pattern past the center line by the width of the zipper tape plus 1/4" (6 mm) clearance.
- Draft the Overlap Shield on the Other: Make a fold-back placket piece, or a self-facing extension, that reaches 1" to 1 1/2" (25 to 38 mm) past the center line. It folds over to hide the zipper completely.
Use the Mirror Layer tool to mirror your left or right piece into the other half. Then draft the overlap and underlap extensions on the two separate patterns.
Hooks, Eyes and Snaps
Hooks and eyes, snaps and magnetic fasteners need an edge margin on the pattern, and the placement matters.
Keep Hardware Away from the Edge
Hardware should never sit right on the finished edge. Too close, and the metal peeks out or rubs against your skin.
- Hook and Eye: Mark the placement 1/16" to 1/8" (2 to 3 mm) inside the finished edge.
- Snaps: Keep snaps at least 1/8" to 1/4" (3 to 6 mm) from any edge.
Use the Add Alignment Marks tool in PatternMaker Pro to make your pattern annotations.
Overlap and Underlap
- Overlap: The top piece, which carries the hook or the top half of the snap, has to cover the underlap completely.
- Underlap: Draft an extension on the lower piece that is wide enough to hold the whole base of the hardware, without running past the inside edge of the facing.
On a waistband, for example, the hook goes on the back of the overlap and the eye on the underlap. A 1" (25 mm) extension on one end of the band gives you that underlap.
Working with PatternMaker Pro
In PatternMaker Pro, you can add an extension by changing the seam allowance or by using the extension tool: