Fastener Extensions
A button closure needs two things from your draft: enough overlap to hold, and buttons in the right place. A common beginner mistake is adding an extension without knowing where the Center Front line sits. The result is a closure that does not line up, or a garment that gaps open when you move.
Don't forget the interfacing. Almost every extension needs it across the whole closure area, from the Center Line over the Fold Line to the Pattern Edge. It supports the buttonholes, backs the buttons and gives the fold a crisp edge. Carry the interfacing 5/8" (15 mm) past the fold and stop it 3/8" (10 mm) short of the inner edge, so the finished edge rolls softly without a ridge.
Center Line vs. Extension Line
The Center Front (CF) or Center Back (CB) line is the true center of the body. When the garment is buttoned, the center line on the overlap piece lies directly over the center line on the underlap piece.
The button extension is the extra fabric you add past the center line, so the edges overlap enough under the buttons.
Calculating Extension Width
There is no single exact number, but most rules make the extension about as wide as the button, with a little extra.
| Rule | Extension for a 1/2" (13 mm) Button |
|---|---|
| Equal to the button size | 1/2" (13 mm) |
| Button width plus 1/16" to 1/8" (2 to 3 mm) | About 9/16" to 5/8" (14 to 16 mm) |
| Half the button width plus 1/4" (6 mm), the least for a large button | 1/2" (13 mm) |
A button centered on the center line sits with half a button width of fabric on each side. Go for the full button width, and add a little for thick buttons or heavy fabric. Think twice before going below half the button width plus 1/4" (6 mm).
Buttonhole Placement
A button sits at the end of its buttonhole, not in the middle. So the buttonhole is placed slightly off center:
- Length: the button diameter plus 1/8" (3 mm).
- Position: the buttonhole starts 1/8" (3 mm) out from the center line, on the extension. About a quarter of the buttonhole sits on the extension and the rest on the body side, so the button lands on the center line when the garment is closed.
Self-Facings vs. Applied Facings
Once you know the extension width, you have to finish the outer raw edge. You can use a self-facing extension, or a separate pattern piece (an applied facing).
The Add Fastener Extension tool in PatternMaker Pro does this whole process for you.
Fold-Over Extension (Self-Facing)
If the front edge is straight, you can draft the facing right onto the pattern piece as one continuous unit.
Drafting Method:
- Find the Center Line (the button placement line) on your pattern.
- Draw a fold line parallel to the Center Line, at the extension width.
- Measure off the fold line 2 x the extension width, to make the pattern edge.
Now you have a Center Line, a Fold Line and a Pattern Edge. When you fold it back, the self-facing covers the buttonhole area on the inside with no extra seam. Because the pattern edge is twice the extension width past the fold, the facing returns one extension width beyond the center line on the other side.
With large buttons, or buttonholes that run across the center line, the buttonhole reaches deeper into the garment than a standard extension covers. Most of the buttonhole sits on the body side of the center line.
Make the self-facing wide enough that the whole buttonhole cut sits on two layers of fabric. When you fold it back, the inner pattern edge reaches past the center line to support all of the buttonhole stitching.
On a curved edge, such as a sloping neckline or a collar point, the top edge of the extension cannot be a straight line.
Extend the Neckline Curve: Carry the neckline curve past the Center Line out to the Fold Line.
Mirror the Curve: From the Fold Line out to the Pattern Edge, draw the neckline curve again in the opposite direction.
When the facing is folded back inside, the mirrored curve flips over and lines up with the original neckline seamline.
If you get confused, draw a quick sample on scrap paper, cut it out and fold it back along the fold line. You will see how the curves line up.
Separate Placket Band
If the front edge is curved, or you want a contrasting fabric, draft a separate placket piece. It is sewn directly to the Center Line and holds all of the extension.
Drafting Method:
- Reduce the garment front:
- Decide the finished width of the placket band.
- Measure back from the Center Front line toward the side seam by half of that width.
- Draw the new joining seamline parallel to the center front edge, and cut away the extra from the garment body.
- Draft the placket band piece:
- Draw a rectangle (or a curved strip to match the garment edge) as wide as the whole finished placket.
- Mark the Center Front line down the middle of the band. The buttons and buttonholes sit here.
- Add the fold lines or facings as in the methods above.
- Add seam allowances:
- Add matching seam allowances to the joining edge of the garment body and to the matching edge of the band.
Applied Facing
Use an applied facing when the extension is drafted onto the main garment, but you want a separate inside piece to finish the edge instead of folding the fabric back.
Drafting Method:
- Find the Center Line (the button placement line) on your pattern.
- Draw a line parallel to the Center Line at the extension width. This is the outer seamline of the garment front.
- Trace the outer seamline, the Center Line, and 2 times the extension width of the connecting lines or curves at the top (neckline) and bottom (hem).
- Mirror your traced lines horizontally.
- Add matching seam allowances along the outer joining edges of both the garment front and the applied facing.
Double-Folded
You can also extend the facing so it folds double. That leaves no raw edges inside the garment and gives the buttons and buttonholes more support.
PatternMaker Pro handles double-folded self-facings and applied facings for extensions.