A welt seam is a strong, flat seam finish commonly used on heavier fabrics and garments that need durability without excess bulk. It creates a neat professional appearance on both the inside and outside of a garment while strengthening the seam with additional stitching. Welt seams are often compared to flat felled seams because they look similar from the outside, but they are quicker to sew and less bulky. This makes them ideal for denim, skirts, jackets, workwear, upholstery, and structured sewing projects.

In this tutorial, you’ll learn exactly how to sew a welt seam step by step, including open welt seams, double welt seams, and the differences between welt seams and flat felled seams.

What is a Welt Seam?

A welt seam is a type of seam that has been sewn flat by first stitching on the wrong side and then securing it on the right side. The welt seam is ideal for use on heavier fabrics needing stronger seams and less bulk. This useful seam is often called a mock flat felled seam. When it is finished it looks like a felled seam, but it has the advantage of not incurring too much bulk. 

If you are learning decorative seam techniques, explore the full types of seams guide to compare strong and decorative seam styles.

Purpose of a Welt Seam

There are several reasons to choose this seam:

1. It is an easy seam to sew.
2. Is strong and hard-wearing.
3. It finishes off the inside and the outside of straight seams neatly.
4. It reduces bulk inside thick fabrics such as denim, leather and suede.
5. Can be decorative and practical at the same time.

How to Sew a Welt Seam (Step by Step)

A welt seam is particularly useful for neatening thicker fabrics or fabrics that fray easily. It is a quick, but secure method of neatening a seam. It is best sewn with a sewing machine rather than by hand. Here are four easy steps to take to sew a welt seam.

1. Sew the Seam

Stitch your plain seam together according to the pattern’s seam allowance.  Set the right sides together and stitch in a straight line.

2. Finish the Seam

Finish the raw edges together either with a zig-zag stitch or a serger. If you are using a serger, do not trim too much off. Other methods of finishing the edge include making bias tape or pinking shears.

3. Press

Press the seam to one side.

4. Topstitch

Topstitch the seam edge down on the wrong side of the fabric to secure the sides of the seam. Turn over to the right side and use a presser cloth to press the seam flat.

Other Types of Welt Seams

Open Welt Seams

Another version is an open or tucked seam. This is a decorative seam and resembles a tuck or fold.  It is an easy-to-do seam and useful on a stitched yolk, giving a tucked effect.

Follow these steps to sew an open welt seam:

1. Put your fabric pieces right sides together and sew a row of basting stitches (L4.0) along the stitching line. 
2. Leave a tail end to the basting at each end of the seam. The tail end is important because it will enable you to pull out the stitches at the end. Do not put a knot or double stitch to secure your basting because it has to pull out easily.
3. Finish off the seam allowance in your chosen method and press the seam allowance to one side.

4. Now on the right side, stitch a row of topstitching 1/4 inch (6mm) away from the original basting of the seam. This stitching must be on the same side as the side you folded the seam allowance.
5. Press your seam flat.

6. Remove the temporary stitches by pulling the basting threads out of the fabric. The threads should pull out easily as you use the tail ends to bring the basting through to the other side and dispose of them. 

Using a different color thread will make sure you have removed all the basting stitches. If the stitches don’t pull through, use a seam ripper to gently remove them.

The seam will appear to open. However, it is not an opening. It is a tuck or folded edge created by the stitching after the neatening and pressing are complete. 

This tuck has several decorative uses on the edges of a yolk or to create detail on a cuffed seam. The open welt seam has been used to hold piping in upholstery and to fit boning into corsets and other fitted garments. 

Double Welt Seams

The double welt seam is the same, but an added row of stitching makes this stronger and gives it a decorative finish. It helps to control bulk and keeps the single welt edge from popping up when you need it to stay flat. Using contrasting colors for the stitching of the double welt seam to add a decorative feel.

From the outside, the double looks like a run and fell seam or a flat felled seam.  However, because it is not folded over, it does not have the bulk of the run and fell seam.

Welt Seam Vs Flat Felled Seam

Welt seams are close to being a flat-felled seam, but the difference is they are less work and quicker to finish. The welt seam is not enclosed like the flat felled, but it does create a neatened edge, and with extra stitching, it flattens the seam creating a smoother finish. The neatening part can be done by your serger, if you have one, or with a simple zigzag stitch on your normal machine. 

If the fabric you are working with frays easily, it is a good idea to neaten the edge with a row of stitching or a zigzag before you start working on the fabric’s difficult edges. You can stop unnecessary fraying with a row of straight stitches before you have a chance to finish the seam.

Welt Seam	Flat Felled Seam

Faster and easier to sew

More time-consuming

Less bulky

Fully enclosed seam

Raw edges are finished together

Raw edges enclosed inside seam

Decorative topstitching

Strong enclosed seam

Better for thick fabrics

Better for medium-weight fabrics

Welt Seams and Corsets

Did you know that the welt seam is a great way to make the partitioning for the boning of a corset? This is probably not something you would rush out to make, but you never know when you may want to add boning to an outfit or to a traditional costume or dance dress.  Read about the types of corsets.

If you do decide to make a corset, then a welt seam is the best choice to make the seam pocket, or casing, to slip the spiral steel boning into. Boning is also a way to add shape to swimsuits and strapless bodices. The boning will add structure to many garments, and the welt seam is ideal for providing support and casing for the boning.

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Welt Seam FAQs

Welt Seams – In Conclusion

A welt seam is a practical, durable seam finish that combines strength, reduced bulk, and decorative topstitching. It is especially useful for thicker fabrics where fully enclosed seams may become too bulky. From denim and workwear to upholstery and corsetry, welt seams are one of the most versatile seam finishes for durable sewing projects.

More Types of Seams

• Plain Seams
• Open Seams
• Closed Seams
• Princess Seams
• Bound Seam
• French Seams
• Grading Seams
• Welt Seams
• Serged Seam
• Pinked Seams
• Double Stitched Seams
• Flat Felled Seams