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Learn How to Sew an Easy Understitch for Crisp Professional Finishes Full Guide of 2024

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how to do understitching sewingYou’ve got this! Sewing an understitch is easier than you think. The key is pressing that seam allowance toward the facing first. Let those hot iron powers smooth things out before you stitch. Your machine’s edgestitch foot will hug that folded seam as you sew, keeping things tidy.

In no time, you’ll have a crisp finish worthy of the big leagues. Sew on, friend! Understitching’s got your back.

Key Takeaways

  • Trim seam allowances, clip curves, and properly align layers before sewing to ensure smooth seams.
  • Stitch just inside the seam line on the lining side to secure raw edges inside the garment.
  • Use a press cloth and press slowly to avoid shine and pressed-in creases.
  • Check for shifting layers, use clips if needed, and take time positioning fabrics before sewing for the best results.

What is Understitching?

What is Understitching
You’d secure the facing or lining to the seam allowances to achieve a professional finish for handmade garments. With this technique, you stabilise the inside of a lined garment by stitching the facing or lining to the seam allowance.

Start by sewing the main fabric and lining together with right sides facing each other. Trim the seams, grade them, and clip curves. Then position the fabrics with the main fabric on the left and lining on the right.

Align the seam allowances under the lining and sew 1/8 away from the fabric/lining seam on the lining side.

Check positioning periodically to achieve an attractive parallel line of stitching on the seam line inside the garment.

Preparing the Seam

Preparing the Seam
After sewing the main fabric and lining together, trim the seam allowances, grade them, and clip any curved areas before understitching.

  • Trim seam allowances to 3/8
  • Cut wider seam allowance to half width
  • Clip inward curves every 1/2

Aligning the layers properly is crucial for smooth, flat seams. Investing the time to properly prep the seam helps ensure the finished garment has a professional appearance inside and out.

Sewing the Understitch

Sewing the Understitch
Progress with care as you stitch just inside the seam line, gently coaxing the layers so the lining hugs the seams. Understitching unites the main fabric and lining into one cohesive unit. This essential sewing task secures facings neatly inside garments.

While not the most glamorous technique, it’s an important step in achieving a polished finish.

Align the seam allowances under the lining and stitch about 1⁄8” away from the seam on the lining side. Check positioning periodically. Ease and guide the fabric as you sew. While understitching requires precision, it remains one of my favorite sewing tasks.

Benefits Challenges
Prevents visible puckering Needs precision
Secures facings and linings Time consuming
Gives a polished look Requires practice
Creates stability Can’t always do full length

Pressing the Seam

Pressing the Seam
Next, press the seam with lining out. The heat from your iron sets the shape, so take care pressing the full length. Press on a tailor’s ham for curved areas. With the right side up, press along the stitching line.

Then flip over and press the seam allowance toward the lining. Proper pressing is crucial for a professional finished look.

  • Set machine to low heat cotton setting
  • Press on the wrong side first
  • Use a press cloth to avoid shine
  • Press curved areas over a ham
  • Go slow and press in sections

This often overlooked step shapes the garment. Put in the effort here to achieve couture results.

Where to Use Understitching

Where to Use Understitching
You must use understitching on necklines and armholes for a professional finish. Understitch right along the seam joining the main fabric and lining, stitching about 1/8 inch away on the lining side. This secures the lining’s raw edges inside the garment. Take care to keep the stitching line straight and even for a crisp edge.

Any curved seam like an armhole or neckline must be understitched to prevent the lining rolling outward. Even a lined skirt needs understitching along the waist seam to keep the top edge smooth.

Your garment gains structure and shape when you neatly contain the edges where fabric and lining meet.

Troubleshooting Tips

Troubleshooting Tips
You’ll fix puckering when carefully aligning the seam while understitching. To troubleshoot understitching:

Take time positioning fabrics. Easing layers eliminates rippling. Inspect stitch placement; too far from seam shows outside. Press thoroughly so lining stays inside. Align, pin, and sew slowly for best results.

Proper understitching brings a couture finish. With patience, your garment gains shape, structure, and neat insides.

Frequently Asked Questions (FAQs)

What kind of thread should I use for understitching?

Use thread in a color matching your garment fabric for understitching. This will make the stitches less visible and provide a cleaner finish. Polyester or cotton threads usually work best. Opt for a longer stitch length around 3-4mm to simplify understitching removal later if needed.

First, test your tension on scraps to properly set the settings before sewing your garment.

How close to the seam line should I sew the understitch?

For professional results, sew the understitch about 1/8 inch (3 mm) away from the seam on the facing/lining side. Keep the seam allowances tucked under as you gently pull the fabrics apart. Check positioning periodically.

Stitching too close to the seam might show through; stitching too far away looks sloppy.

Do I need to understitch curved seams differently than straight seams?

You don’t need to understitch curved seams differently than straight ones. Simply align the seam allowances under the lining/facing, then sew 1/8 inch away from the fabric/lining seam on the lining side.

Gently pull the fabrics apart as you sew to keep the seam tucked under evenly, whether it’s a curve or straight line.

What is the best stitch length to use when understitching?

When understitching, use a longer stitch length between 3-4mm. This creates an easier to remove and more secure stitch. Gently ease the fabric layers apart as you sew to keep the seam tucked under. Periodically check positioning.

Do I need any special sewing machine attachments to make understitching easier?

You don’t need any special sewing machine attachments for understitching. Using a regular straight stitch foot allows maneuvering the fabric layers smoothly under the presser foot while keeping everything aligned as you sew.

With practice, understitching by hand works too if you don’t have a machine. The key is maintaining consistent tension to keep the facing or lining perfectly secured.


If you’re new to sewing garments, understitching may seem intimidating. But with the right preparation and tools, it’s an easy technique that takes your projects to the next level. As you make that final snip and gently ease the seam allowance toward the lining side, you’ll feel a sense of satisfaction.

This simple line of stitching ensures crisp edges that lie flat and look couture. Understitching prevents facings and linings from rolling or sticking out, for clean finishes inside and out. With practice, you’ll gain confidence mastering this fundamental skill that helps create professional-looking sewn clothes and accessories.

So grab your machine and needles, match up your seams, and start understitching.

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Mutasim Sweileh

Mutasim is the founder and editor-in-chief of, a site dedicated to those passionate about crafting. With years of experience and research under his belt, he sought to create a platform where he could share his knowledge and skills with others who shared his interests.