A facing stays inside when four things are done: the seam allowances are trimmed and clipped so there is no bulk pushing outward, the facing is understitched to those allowances 2 mm (1/16 in) from the seam, the seam is pressed so it rolls 1–2 mm toward the inside, and the facing is anchored to the garment at the shoulder and side seams. Understitching does most of the work. If a finished facing already rolls out, the quickest fix is a row of topstitching or edgestitching around the neckline, or a few hand tacks at the seams.

Why does a facing roll out?

A facing is a shaped piece sewn to an edge and turned to the inside, so that the seam between garment and facing lies exactly on the edge. Nothing holds it there except the way it was sewn and pressed. It rolls out when:

  • the seam allowances were left full width, so two layers of 1.5 cm (5/8 in) fabric push the edge outward;
  • a curved seam was not clipped, so the allowance is shorter than the edge it has to follow and pulls the facing out flat;
  • the facing was not understitched, which is the row of stitching that keeps the seam allowances on the facing's side;
  • the edge was pressed with the seam exactly on the fold rather than rolled slightly to the inside;
  • the facing was cut from a fabric that is stiffer than the garment, or without interfacing, so it has no reason to lie flat;
  • the facing's free edges were never anchored, so it lifts every time the garment is pulled over the head.

What do you need?

  • Fusible interfacing on every facing piece, light to medium weight. Interfacing gives the facing a flat memory and stops the neckline stretching.
  • Small sharp scissors for clipping curves and grading.
  • A regular foot, or an edgestitch foot with a guide blade, which makes understitching easier to keep at a constant distance.
  • A tailor's ham or a rolled towel, to press the curve of a neckline or armhole in shape.

How do you sew a facing that stays inside, step by step?

  1. Interface the facing pieces and sew them together at the shoulders. Finish the outer edge with a serger, a zigzag, a turned-and-stitched edge, or by stitching a narrow strip of bias tape to it.
  2. Staystitch the garment neckline 1.2 cm (1/2 in) from the edge, inside the allowance, so it keeps its shape while you handle it.
  3. Sew the facing to the garment right sides together, matching the shoulder seams and notches, with the usual 1.5 cm (5/8 in) allowance. Shorten the stitch to 2 mm around tight curves.
  4. Grade the allowances. Trim the facing's allowance to 6 mm (1/4 in) and the garment's to 1 cm (3/8 in), so the layers step down and the edge has no ridge. The layer nearest the outside stays the longest.
  5. Clip the curve every 1–1.5 cm (3/8–5/8 in) on an inward curve such as a neckline, cutting to within 2 mm of the stitching. On an outward curve, cut small notches instead. The clipping and notching post shows the difference.
  6. Press the allowances toward the facing, from the wrong side, with the seam open flat under the iron.
  7. Understitch. With the garment right side up and the facing opened away from it, sew through the facing and both allowances 2 mm (1/16 in) from the seam, on the facing side. Go as close to the ends as the foot allows. Understitching is invisible from the outside and is the one step that makes the facing turn and stay.
  8. Turn the facing to the inside and press the edge over the ham, letting the seam roll 1–2 mm toward the facing. Press from the inside, so the facing is pressed under rather than the garment pressed over.
  9. Anchor the facing at the shoulder and side seams: stitch in the ditch of the seam for 2–3 cm (3/4–1 1/4 in) through the facing, or sew it down by hand with a few stitches through the seam allowance only. Stitching in the ditch is invisible on the outside.

How do you understitch a tight curve?

On a small neckline or an armhole, the facing cannot be laid flat enough to sew a long straight run. Work in short sections, lifting the presser foot with the needle down every 2–3 cm to pivot and smooth the allowances under the facing with your fingers ahead of the foot. Where the shoulder seams cross the neckline, the layers pile up: press the seam allowances open before you understitch, and trim the corners of the allowances at the seam to reduce the bulk. For a V-neck, stop the understitching about 1 cm (3/8 in) from the point on each side and let the point turn itself.

An armhole facing is understitched the same way, but it tends to show at the underarm. Understitch as far as you can, then anchor the facing at the side seam.

What can you do if the facing already rolls out?

  • Topstitch or edgestitch around the edge from the right side, 2–5 mm (1/16–3/16 in) from the fold, through all layers. On a casual garment, this is a design feature, and it keeps the edge flat for good. How to topstitch straight covers the foot and the guide to use.
  • Understitch after the fact. Fold the garment back on itself along the seam, lift the garment layer out of the way and understitch through the facing and allowances from the wrong side, as far around as you can reach.
  • Hand tacks at each seam and, on a wide neckline, at the center front and back: a few stitches through the facing's outer edge into the seam allowance or into the garment with a tiny stitch that does not show.
  • A narrow strip of fusible hem tape between the facing's outer edge and the garment holds a lightweight facing in place without stitches, and is worth trying on a knit.
  • Replace the facing with a binding if it is an armhole facing that never behaves: unpick it and finish the edge with bias binding instead.

What are the common mistakes with facings?

  • Skipping the interfacing because the fabric felt firm. Washing softens it, and the facing then flaps.
  • Understitching the garment instead of the facing. The stitching must be on the facing side of the seam, catching the allowances, or it shows outside and does nothing.
  • Trimming before sewing. Trim and clip after the seam is sewn, so the pieces still match at the edge while you sew.
  • Pressing the seam open flat and then folding gives an edge that sits exactly on the seam, which rolls either way. Roll it toward the inside while pressing.
  • A facing cut to the same size as the garment edge with no shortening. Patterns often draft the facing a fraction smaller at the outer edge so that it pulls in; if yours does not, trim 2 mm from the outer edge of the facing before attaching it.
  • A facing on a stretchy knit neckline. Facings on knits need a knit interfacing and, usually, topstitching; a band is a better choice.

When should you use a facing instead of bias binding or a lining?

A facing gives a clean, flat edge with no stitching showing on the outside, which suits necklines and armholes on blouses, shift dresses and anything in a crisp fabric. Bias binding is better on sheer and lightweight fabrics, where a facing shows through, and on curves so tight that a facing fights them; the facing, bias binding or lining comparison covers the choice edge by edge. A full lining replaces the facings entirely on a sleeveless dress, finishing the neckline and both armholes in one go, and is the usual answer when both edges are faced and keep rolling. If you sew from a Sewly pattern and a step mentions understitching, you can ask the sewing guide what it means and where exactly the stitching goes for that neckline.