Fastener Extensions
When designing front or back button closures, the pattern draft must account for both functional overlap and geometric button placement. A common beginner error is adding an extension without understanding where the Center Front line sits, which leads to misaligned closures or garments that gap open during movement.
Don't forget your interfacing! Nearly all extensions require interfacing across the entire closure zone (from the Center Line across the Fold Line to the Pattern Edge) to support the buttonholes, back the buttons, and give the fold line a crisp finish.
Center Line vs. Extension Line
The Center Front (CF) or Center Back (CB) line represents the true center of the body. When a garment is buttoned, the Center Front line on the overlap pattern piece must lay directly over the Center Front line on the underlap pattern piece.
The Button Extension is the extra fabric added past the Center Front line to ensure the edges overlap sufficiently beneath the buttons.
Calculating Extension Width
As a standard rule of thumb, the extension width added past the Center Front line is as follows:
- Calculating Extension Width:
- The full diameter of the button, or at minimum, half the button diameter plus 1/8" (3 mm) clearance.
- Example: For a 1/2" (12 mm) button:
- Minimum Extension (Half Diameter + Clearance): 1/4" + 1/8" = 3/8" (6 mm + 3 mm = 9 mm)
- Full Extension (Full Diameter): 1/2" (12 mm)
This ensures the button sits cleanly in the center of the overlap without hanging over the finished outer edge.
Self-Facings vs. Applied Facings
Once the extension width is established past the Center Front line, the outer raw edge must be finished using either a self-facing extension or a separate pattern piece (applied facing).
The Add Fastener Extension tool in PatternMaker Pro makes quick work of this entire process.
1. Fold-Over Extension (Self-Facing)
If the front edge of the garment is straight, the facing can be drafted directly onto the pattern piece as a single continuous unit.
Drafting Method:
- Locate the Center Line (button placement line) on your main pattern.
- Draw a fold line parallel to the Center Line at the calculated Extension Width.
- Measure off the fold line 2 x ExtensionWidth to create the pattern/extension edge.
Now you have a Center Line, a Fold Line and a Pattern Edge line. When folded back during construction, this self-facing completely covers the buttonhole area on the inside without requiring an extra seamline.
If using large buttons with buttonholes perpendicular to the Center Line, your buttonholes may extend deeper into the garment than a standard extension covers.
When drafting your self-facing, increase the extension width as needed so the buttonhole cut sits entirely on two layers of fabric. When folded back during construction, this extends the inner Pattern Edge past the Center Line to fully support the buttonhole stitching.
When drafting a fold-over self-facing along a curved edge (like a sloping neckline or collar point), the top edge of the extension cannot be a straight line.
Extend the Neckline Curve: Continue the natural neckline curve past the Center Line out to the Fold Line.
Mirror the Curve: From the Fold Line out to the Pattern Edge, mirror the exact curve of the neckline in the opposite direction.
When the facing is folded back inside the garment during construction, this mirrored curve flips over to align perfectly with the original neckline seam line.
If you get confused, draw a quick sample on a scrap piece of paper, cut it out, and fold it back along the fold line. You will quickly see how the curves line up!
2. Separate Placket Band
If the front edge is curved or requires a contrasting fabric, a separate placket pattern piece must be drafted. This is sewn directly to the Center Line and contains all of the extension.
Drafting Method:
- Reduce the Garment Front:
- Decide on the total finished width of the placket band.
- Measure back from the Center Front line toward the side seam by half the finished placket width.
- Draw the new joining seamline parallel to the Center Front edge and trim/cut away the excess from the garment body.
- Draft the Placket Band Piece:
- Draw a rectangle (or curved strip matching the garment edge) with a width equal to the total finished placket width.
- Mark the Center Front line directly down the middle of this band. Buttons and buttonholes will sit here.
- Add the required fold lines/facings following the instructions above.
- Add Seam Allowances:
- Add matching seam allowances to the joining edge of the garment body and the corresponding edge(s) of the placket band.
3. Applied Facing
An applied facing is used when the extension is drafted directly onto the main garment, but you want a separate interior piece to clean-finish the edge rather than folding the fabric back.
Drafting Method:
- Locate the Center Line (button placement line) on your main pattern.
- Draw a line parallel to the Center Line at the calculated Extension Width. This creates the outer seamline of the garment front.
- Trace the outer seam line, Center Line and 2 times the Extension Width of the connecting lines/curves at the top (neckline) and bottom (hem).
- Mirror your traced items horizontally.
- Add matching seam allowances along the outer joining edges of both the garment front and the applied facing piece.
Double-Folded
Another option is to extend the facing to allow it to be folded double. This eliminates all raw edges on the inside of the garment and provides greater support for buttons and buttonholes.
PatternMaker Pro accommodates double-folded self-facings and applied facings for extensions.