Understitch for Professional Garment Sewing

Read our step by step guide and never skip understitching again. From what it does, how it makes your garment look professionally sewn and when to understitch; our guide covers all your questions and will have you sewing at expert level in no time. 

Understitch - What is it?

Understitching is a row of stitching on the inside edge of a garment, usually a facing, sewn to keep the seam rolled to the inside of the garment.

Understitching is never visible from the right side of the garment. Unlike basting, understitching is permanent.

Understitching seems like a step you could skip, and just press the garment instead, but it makes a world of difference to the crispness of your edges.

It's a professional sewing technique that can drastically improve the finished results of your sewing. In short, understitching is an easy to sew row of stitches that makes your garments look good!

Examples of Understitching

On the left, it's easy to spot the understitching in white thread against the floral print. It's the row of visible stitches near the top finished edge of the garment. You can also see just above the white stitches the seam that attaches the outside garment fabric to the facing. This seam is slightly towards the inside of the garment.

On the right, the understitching blends in with the matching coral thread.

Note on both examples, the understitching is not visible on the outside of the garment.

  • WHEN DO YOU USE IT?

    • Understitch after sewing the facing to the garment but before pressing the facing to the underside
    • Any garment that has facings can be understitched
    • Usually the pattern instructions will tell you when to understitch. But if they don’t, feel free to add it! (Read to the end of the pattern instructions before adding it in to make sure it doesn’t happen later in the construction.)

HOW TO UNDERSTITCH A FACING

GRADE YOUR SEAM ALLOWANCE

After sewing the facing to your garment, grade your seam allowances. To do so, use scissors to cut the seam allowances smaller. Trim so that each side of the seam allowance is a different length. For example, a ⅝" seam allowance can be trimmed to ⅜" and ¼".

Doing so helps reduce the bulk of your facing seam line.

CLIP CURVES

Clip inner curves so the seam will lie flat by making snips into the seam allowance about ½" (1.3cm) apart. Make more snips into very curved areas and less snips into less curved areas.

Be careful not to snip into your stitching line.

Once clipped, the curve can now be stretched into a straight line! You’ve made your seam more flexible. This is an important step, as otherwise it will be harder to understitch the facing.

POSITION YOUR FABRIC LAYERS

The goal of understitching is to attach the facing to the seam allowances underneath. Arrange your piece so that the facing is on top. Open up the seam line and stretch the seam as much as you can (gently!) with your fingers.

Before you begin to sew, double check that your seam allowances are in the right spot. You want both seam allowances to be flat and pointed towards the facing, so you catch them with your understitch.

You’ll notice I didn’t press the seam open with an iron. I find you get better results by stretching and understitching and then pressing the facing. This way there’s no crease mark when you understitch.

UNDERSTITCHING SEAM ALLOWANCE

Insert the needle into the facing, very close to the seam line.

You want to keep this stitching very close to the edge, as close as you can maintain, while not crossing over onto the bodice front fabric. If you can manage to get at least 1⁄8" (3mm) away from the outside fabric seam, that will work.

Lower your presser foot and begin stitching slowly as you stretch the seam open with your fingers. Begin with a small backstitch and continue following the fabric.

FINISH + PRESS

Continue along the seam line until you get to the end. Backstitch and trim threads.

Now look at how nicely your facing rolls to the inside of your garment.

You’ve made it want to stay in the right place!

Pressing the facing will be so easy since you’ve created this lovely natural curve.

UNDERSTITCHING TIPS

  • Understitch linings, as well as facings if they start to roll to the right side.
  • You can also understitch by hand and thereby get into smaller areas like corners that the sewing machine can’t reach. Thread a handsewing needle with a double thread, and sew tiny prickstitches to secure the facing to the seam allowance. It’s time-consuming but adds a couture finish to gowns and formal wear.

YOU CAN DO IT!

The payoff for taking the time to understitch is huge!

It ensures that your facing will stay in place nicely and not roll to the front of your garment. It's an easy sewing step to want to skip, but when completed gives professional results.