Flat Felled Seam: How to Sew Flat Felled Seams Step by Step

Learning how to sew a flat felled seam is one of the best ways to create strong durable seams with a professional finish. Flat felled seams fully enclose raw fabric edges, making them ideal for garments that need extra strength and comfort such as jeans, shirts, overalls, and sportswear. This seam is commonly found in denim clothing because it creates a neat finish on both sides of the fabric while preventing fraying. In this tutorial, you will learn exactly how to sew a flat felled seam step by step, including curved seams, mock flat felled seams, and the best fabrics to use.

What is a Flat Felled Seam?

A flat felled seam is a simple seam designed to encase raw edges to prevent them from fraying as well as providing an attractive and extremely durable seam.

If you are learning strong durable seam finishes, explore the full types of seams guide to compare flat felled seams with other enclosed seam types.

Here is how to sew a flat felled seam. Keep reading for the step by step instructions with more photos.

1. Stitch the seam with wrong sides together. Press open the seam and trim one seam allowance.
2. Press the wider seam allowance in by 1/4 inch
3. Fold it over the trimmed side.
4. Stitch along the open folded edge.

You can see from this photo below that the inside of the item has a clean finish with no raw edges or finishing visible. This makes it a great seam for people and especially kids who are irritated by serged seams. These seams are a seam and seam finish all in one! If you don’t have a serger then this can be a great alternative to create simple flat open seams.

When to Use a Flat Felled Seam

The flat felled seam is ideal for denim and cotton fabrics but may be too bulky for heavier material. If you look at your denim jeans, shirts, or jackets, you will see lots of felled seams. Flat felled seams are also a great choice for linen since the raw edges are encased preventing them from fraying. It is more difficult to sew around curves and is best used on straight seams if you are a beginner.

Supplies Needed

• Sewing Basics – Sewing machine, scissors, thread, pins
• Pressing Tools – Iron and ironing board
• Presser Foot – All-purpose sewing foot and optionally an edge stitch foot or felling foot.

Flat Felled Seam Video Tutorial

Here is a video I made to show you how easy it is to sew this seam. Subscribe to my YouTube channel for weekly sewing videos. Relax and press play below >>

How to Sew a Flat Felled Seam (Step by Step)

1. Add Seam Allowance

Before you start, check your seam allowance width. It should be at least 5/8 inch (15mm) wide. Any less than this will result in a really narrow seam that will be hard to sew. Do a test of the seam on a scrap of fabric and adjust the seam allowance if necessary.

2. Stitch the Flat Felled Seam

Place your fabric pieces with wrong sides together and stitch along the normal seam line. (This is the opposite to what you would normally do so it may feel a little strange!)

Press the seam open. If you have a delicate fabric, use a presser cloth for all pressing so you don’t damage the fabric.

3. Trim the Seam

Trim one side of the seam to a width of 1/8 inch (3mm). It is important that there is no fraying as loose threads can stick out and get caught under your stitching in the next step.

4. Press and Fold

Press the wider seam allowance (untrimmed) edge over by 1/4 inch (6mm).

Fold the wider, pressed edge over to encase the trimmed edge. Make sure the pressed and folded edge is the same width all along the seam. It can look strange if it goes in and out. The smaller seam allowance which was trimmed is now hidden inside.

5. Outside Stitching

Stitch along the open edge of the seam 1/16 (1.5mm) to 1/8 inch (3mm) from the edge. You want to stitch as close as you can without going off track.

Beginners: Use pins or hand baste with a large running stitch to secure the seam before you sew. Cotton normally irons a crisp edge but slippery fabrics or thin fabrics like silk and polyester will be difficult to sew without some hand basting first.

You can use your regular all-purpose sewing foot, but for really accurate and neat stitching, an edge stitching foot can really help. See how it has a guide in the center that will run along the edge of the seam. You will need to move your needle position slightly to the left rather than leaving it in the center as you would for normal sewing. You could also use a twin needle for extra topstitching. Read more on edgestitch foot

Using a Flat Felled Presser Foot

The felling foot is a presser foot designed for sewing flat-felled seams. It will glide along the edge of the pressed seam and accurately stitch the edge. This specialty foot comes in different widths so you can match your desired seam allowance. Choose a wider foot for thicker fabrics and a narrower foot for fine or sheer fabrics.

The advantage of the felling foot is that it saves you from so much pressing as the fabric will guide you through the gap in the foot.

Sewing Curves with Flat Felled Seams

Flat felled seams are often sewn around curves in the center crotch area of pants and trousers. These give a durable seam that won’t unexpectedly rip and cause undue embarrassment.

If you are using the flat felled seam around a curved edge, then clip the trimmed edge of the seam before encasing the seam as this will give more elasticity to the seam and allow you to turn a corner. There is an example of this in my video. When clipping sewing, put tiny snips every 1/4 inch (6mm) making sure you do not cut the stitching line. If you accidentally snip the stitching line, make sure you go back with your machine and reinforce it.

However, it is worth noting that this seam is best suited to the straight path of your seam line or gently curved seams.

Variations of the Flat Felled Seam

Mock Flat Felled Seam

A mock flat felled seam is a variation used for thicker fabrics such as denim and canvas. This seam is commonly found inside your jeans and denim jackets. It is faster to complete and reduces bulk as the seam allowance does not need to be pressed over. A mock flat felled seam is best sewn on seam allowances that are at least 1/2 inch (12mm) wide.

1. Finish the seam allowance on one side of your fabric. With right sides together, sew the seam with your regular sewing machine with your desired seam allowance.
2. Trim down the seam allowance that was unfinished to 1/4 inch (6mm) in width.
3. Press the finished seam allowance over the trimmed seam allowance.
4. Stitch the seam in place next to the finished edge. If your seam allowance was 1/2 inch (12mm) this means you will be stitching around 3/8 inch (1cm) from the seam.

Run and Fell Seams

The biggest difference when you sew a run and fell seam is that the fabric is placed right sides together when you sew the first seam. The folded seam will be underneath and not visible on the right side of the fabric. All you will see on top is a single row of stitching around 3/8 inch (1cm) from the seam.

1. Place your fabric right sides together and stitch the seam. Seams must be 5/8 inch (15mm) or wider.
2. Trim one side of the seam allowance down to 1/4 inch (6mm).
3. Press over the wider seam allowance (untrimmed) so it folds over the trimmed side.
4. Turn the fabric to the right side and stitch around 1/4 inch (6mm) from the seam. It is important to catch in the seam allowance underneath.

BEGINNERS – If you find this hard to keep straight, you can always sew from the wrong side instead. The reason it is better to stitch on the top is that the stitching will just look neater. The top spool stitching always looks better than the bobbin stitching.

How to Sew a Flat Felled Seam by Hand

Any of the regular or variations of the flat felled seam can be sewn using hand stitches. It is, however, better used on the mock seam where the seam allowance is on the inside. That way your hand stitches will hold tight and prevent fraying but will not be visible.

For the main seam, the strongest hand stitch is the backstitch. Because the top of the backstitching looks better, plan ahead and stitch on the side that will be visible once the seam is folded and tucked.

When sewing the folded edge, use a whip stitch or blind stitch so the stitching isn’t visible on the outside. All you will see is the tiny pinpricks of stitching which will be invisible if you use a matching thread.

Flat Felled Seam vs Other Seams

Seam Type	Main Difference
French Seam	Best for delicate lightweight fabrics
Topstitched Seam	Decorative stitching only, raw edges may remain exposed
Edge Stitching	Decorative seam edge stitching without enclosed edges
Serged Seam	Uses overlocker rather than folded enclosed seam
Mock Flat Felled Seam	Faster version with reduced bulk

Flat Felled Seam FAQs

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Flat Felled Seam – In Conclusion

Now that you know how to sew a flat felled seam, you can create stronger more professional seams for garments and sewing projects that need durability and comfort. From jeans and workwear to children’s clothing and sportswear, flat felled seams remain one of the best seam finishes for long-lasting sewing projects.

More Types of Seam Articles:

• Mock French Seams
• Straight Seams
• Hong Kong Seam
• Understitching
• Welt Seams
• Taped Seams
• Slot Seams
• Double Stitched Seams