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Zippers & Hardware

When drafting openings for closures, the seam allowances and edge margins must be calculated based on the specific type of hardware you plan to install. Drafting the wrong seam allowance width or failing to leave proper hardware clearance can cause zippers to buckle or allow metal fasteners to show on the finished garment edge.

Zipper Seam Allowances & Extensions​

Unlike standard construction seams that typically use a uniform 5/8" (16 mm) allowance, zipper seams require specific seam allowance adjustments depending on the application style.

1. Centered & Lapped Zippers​

For traditional centered or lapped zipper applications, standard seam allowances must be maintained or slightly widened along the opening.

  • Standard Seam Allowance: Use 5/8" (16 mm) to 3/4" (19 mm) along the zipper insertion edge.
  • Lapped Zipper Adjustment: The overlap side requires a full 3/4" (19 mm) seam allowance to ensure the folded fabric completely hides the zipper teeth without pulling or distorting the seam.

In PatternMaker Pro, use the Change Line/Curve Seam Allowance tool to assign a custom value to specific lines or curves. The automatic Add Seam Allowance tool will then apply that custom distance when generating the pattern.

2. Invisible Zippers​

Invisible zippers are sewn directly adjacent to the zipper coils, meaning no extra fabric overlap is required.

  • Seam Allowance: Draft a standard 5/8" (16 mm) seam allowance along the zipper edge.
  • Pattern Annotation: Mark precise stop marks on the pattern piece to indicate where the zipper stop sits, ensuring the seam below the zipper aligns smoothly.

Use the Add Alignment Marks tool in PatternMaker Pro to make your pattern annotations.

3. Exposed Zippers​

Exposed zippers showcase the zipper tape and teeth as a design feature.

  • Drafting Cutout: Instead of a standard overlapping seam allowance, you must subtract width from the pattern edge equal to half the visible width of the zipper tape.
  • Opening Window: If inserting an exposed zipper into a slash opening, draft a rectangular window cutout matching the exact dimensions of the zipper teeth and visible tape.

Hidden Zipper Plackets​

A hidden zipper placket uses a fly-like fold or guard extension to conceal a heavy-duty zipper completely. This is commonly used on jackets, coats, or decorative closures.

Drafting a Placket Extension​

  1. Define Center Line: Locate the Center Front or Center Back seam line on your pattern draft.
  2. Add the Underlap Extension on One Pattern: Draft an extension past the center line equal to the width of the zipper tape plus 1/4" (6 mm) clearance.
  3. Draft the Overlap Shield on the Other Pattern: Create a fold-back placket piece (or self-facing extension) that extends 1" to 1.5" (25 to 38 mm) past the center line. This shield folds over to completely hide the zipper hardware beneath it.
PatternMaker Pro

Use the Mirror Layer tool in PatternMaker Pro to mirror your left/right pattern piece to make the other half of the pattern. Then draft your overlap and underlap extensions on the separate patterns.

Hooks, Eyes & Snaps: Hardware Clearance​

When adding physical closures like hooks and eyes, press snaps, or magnetic fasteners, you must leave an appropriate edge margin on your pattern.

1. Setback Edge Margins​

Fasteners should never sit directly on the finished edge of a garment. If metal hardware is placed too close to the finished line, the metal will peek out or rub against the skin.

  • Hook & Eye Setback: Draft a hardware placement mark set back 1/16" to 1/8" (2 to 3 mm) inside the finished garment edge.
  • Snap Setback: Center snap placement marks at a distance at least equal to the radius of the snap cap plus 1/8" (3 mm) clearance from any finished edge or seamline.

Use the Add Alignment Marks tool in PatternMaker Pro to make your pattern annotations.

2. Overlap & Underlap Geometry​

  • Overlaps: The top piece carrying the hook or top snap half must cover the underlap completely.
  • Underlaps: Draft the extension on the underlying pattern piece wide enough to support the entire base of the hardware without extending past the interior facing edge.

Working with PatternMaker Pro​

In PatternMaker Pro you can add extensions either by changing the seam allowance or using the extension tool:

Quick Review​

✏️ Question #1: Why should hooks, eyes, and snaps be drafted with a setback edge margin of 1/16" to 1/8" (2 to 3 mm) inside the finished garment line?

✏️ Question #2: How does the seam allowance draft for an exposed zipper differ from a centered zipper?

✏️ Question #3: What is the primary function of drafting a hidden zipper placket extension?