How to Understitch & Why You Need it in Your Sewing Arsenal

Do you know how to understitch? If you make clothing or other items that have a lining or a facing, then this is one technique you need to know.

It may sound intimidating, if you’ve never done it before. But it’s actually really easy.

What is an Understitch?

Understitching is a finishing technique for garments, handbags, and other items that have a lining or facing. Understitching keeps the lining or facing from peeking out and ruining the appearance of the item.

Essentially, an understitch is a line of stitches close to the edge of a facing that keeps that facing from rolling outward. You’re stitching the lining (or facing) to the seam allowances – both its own seam allowance and that of the outer fabric.

It’s not difficult to do, and it can make your finished garment look tidy and professional.

What You Will Need 

Before you begin, collect your tools. 

• Your outer fabric
• Lining or facing material
• Thread that matches your outer fabric
• Scissors or snips
• Iron
• Your sewing machine

Are you ready? Let’s learn to understitch!

Tips to Bear in Mind Before you Begin

Understitching isn’t hard, but there are a few tips and tricks that can help you to get more professional results.

First, grade the seam allowances. What does this mean? It means to trim them, but not to the same width. You’ll be trimming the seam allowance of the facing a bit closer to the seam than that of the outer fabric.

Next, keep your fabric taut while you understitch. While you’re stitching, gently pull the fabric to each side. This will keep the seam nice and flat.

Also, sew your understitching line parallel to your seam. No one is going to see your understitching line, but this step will give the item a tidier finish.

If you’re understitching a corner, sew into the corner, but never out of it. This means once you reach the corner itself, stop, back tack, cut your threads, and reposition the work to sew into the other corner. 

Step by Step Instructions

So, how do you understitch? We’re glad you asked.

Step 1: Attach Your Facing or Lining

Lay your facing piece and your outer piece together, right side to right side.

Now, stitch them together. 

A ⅝ inch (0.625 inch, or 1.58 centimeters) seam allowance is considered the standard.

Step 2: Press Your Seam

Press the seam allowance toward either the facing or the lining (your choice).

Step 3: Trim Your Seam Edges

You’re going to be trimming the seam allowances closer to your stitch line. This will keep the seam from being bulky. 

Don’t trim them too close to the stitch line, because you’re going to need a bit of seam allowance yet for grading.

Step 4: Grade the Edges

“Grading” means trimming the seam allowances relative to one another. Specifically, you’ll be trimming the seam allowance of the facing closer to the stitch line than that of the outer fabric.

Step 4: Clip or Notch

If you’re sewing a curve, for example an arm hole or a round collar, clip the seam allowances close to, but not across, the stitch line. This will allow them to move as necessary.

Trimming, grading, and clipping are all important steps if you’re working with curves. Skipping ahead, you can see the difference that each step makes below.

Finished curve with clipping, grading, and notching.

Finished curve with no clipping, no grading, and no notching.

Finished curve with clipping, but no notching or grading.

Finished curve with clipping and grading, but no notching.

Step 4: Make Your Understitching

Stitch the lining or facing to both seam allowances. Make this line of stitching on the inside of your item. It will not show on the outside. Stitch between 0.125 inches (.32 centimeters) and 0.25 inches (.63 centimeters).

Here’s what it will look like on the inside of your garment. This line of stitches should not show on the outside.

Step 5: Press Again

Now press the facing toward the lining.

See how nice and neat it looks from the other side?

Here’s what it looks like on the outside of the garment.

Want to see the whole process from beginning to end? This video can show you how it’s done.

Final Thoughts

Understitching is one of those finishing touches that can make the difference between a homemade item that looks homemade, and one that looks professionally done. 

Do you have any tips for making understitching easier or more successful? We’d love to hear it!