Sewing a Flat Felled Seam. Everything you need to know and more!

In this tutorial, you are going to learn how to sew a Flat Felled Seam to use in all your garments.

This seam, usually seen on denim pants and jackets is meant to make seams stronger and more durable.

Also, one of their greatest characteristics is that it leaves a clean finish on the inside of the garment. 

I bet once you learn how to make this seam, you’ll find a lot more uses for it besides denim clothes. 

So keep reading and jump in into this video and picture tutorial.

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I think you are going to enjoy this tutorial pretty much. 

We will be talking all about Flat Felled Seams, what it is, where is it used, if there is a presser foot to make the job easier and, even how to make a faux version of this seam just in case you are in a hurry.

I think the first time I learned how to make this seam was when I was learning how to make dress shirts in college. A long time ago, indeed.

And truth be told. I “felled” in love with it (I accept pity laughter, thank you).

Is this techinque hard to learn?

I am not going to lie to you, this seam surely requires work and time to get it perfect. But it’s totally worth it!

And as well as the rolled hem foot, there is a presser foot to make this seam easier with your sewing machine.

Now, if you have been researching this technique, you will read that the uses for this seam are only denim and shirts.

But do not be fooled! This seam can be used in a lot more projects than just that. 

For example, I like to use it when I am sewing lace tops to have a clean finish. And of course, because it is so much better than have serged edge finishes.

You know how when you serge lace the seam just won’t look clean because of the gaps of the fabric? Well, this takes care of that as easy as pie.

Are you ready to learn a new technique? Let’s jump in!

What is a Flat Felled Seam?

A Flat Felled Seam is a seam made by sewing two layers of fabric together and then using one layer of the seam allowance to enclose/cover the other layer of seam allowance to then be pressed and topstitch down flat.

Both edges of the seam allowance are enclosed and protected so they don’t fray or stand out on the interior of the garment.

Making this type of seam on a garment will make it stronger and more resistant due to its both seam lines.

Also, it will give a clean finish on the inside of the garment, as it won’t leave any seam allowances hanging out.

Where is a Flat Felled Seam commonly used?

The most common use for this type of seam is to sew denim jeans and jackets. It is also commonly seen in men’s dress shirts. 

The main reason to be used on both of these garments is because of their strength and the fact that they don’t leave any bulk or hanging seams inside of the clothes.

This makes them look really clean and endure the stress of wearing the garment for a long time.

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It was originally used for work clothes for the same exact reason.

But nowadays only high-end and homemade garments have a real flat felled seam.

You will find a lot of commercial garments with faux/mock Flat Felled seams. This is because the fast fashion industries like to save time and money by making them this way.

But my recommendation for you, that have the time and the opportunity to make it the right way is to learn and practice this seam as much as you can.

What do you need?

To make this seam you just need your usual sewing tools and materials:

• Fabric (two layers)
• Thread
• Pins or Sewing Clips
• Sewing Machine
• Sewing Scissors
• Iron

How to sew a Flat Felled Seam?

Watch this video to see how to easily sew a flat felled seam or follow the step-by-step picture instructions below.

Step by step Sewing Instructions

1. Pin the edge of the fabric

Place both layers of your pattern garment piece with the wrong sides of the fabric facing together. 

Match the edges and pin them.

2. Sew at the indicated seam allowance.

My to-go measure on a seam allowance for this type of seam is ⅝”. 

But depending on the garment you are sewing it could be ¾” or any other measurement the designer decides.

So check on the instructions and sew with the indicated seam allowance.

3. Trim the Inner Seam Allowance

After sewing along the edge you are going to decide where you want your seam to fall (hence the name).

Again, it depends on the garment and on the design. 

For example, I like to throw the seams from the center front to the back. Meaning that if it were to be a side seam I will cut the back seam allowances.

Trim at least half of the seam allowance you want to enclose.

Then, press both of the seams so the bigger seam allowance covers the smaller one.

4. Enclose the seam allowance.

Use the upper (wider) seam allowance to fold it over the inner seam allowance.

Then pin that fold flat all along the seam.

Make sure that the width of the fold is the same all along the seam line.

Also, check that the seam at the back is wide opened. I am saying this because it has happened to me that the back fabric gets gathered or pulled.

Press again.

5. Make a topstitch.

Finally, make a topstitch with your sewing machine at ⅛” or 1/16” from the folded edge.

Remember to backstitch at the beginning and at the end of the seam.

Then finish off with a final press.

Tips to get better finishes on this type of seam.

As with any other sewing technique, practice is the key to a better finish. But I wanted to give you some tips to take into account when you are practicing or sewing your Flat Felled Seam.

• Always make sure both edges of the fabrics are perfectly aligned. You won’t want the bottom one slide and suddenly have two different widths of seam allowances.
• Pressing is a must to get perfect results on this seam. Don’t skip these steps!
• Use a sliding measurement rule to make sure all the folded edge has the same width all along the seam.
• Use a basting stitch to hold your seam flat before sewing. This will guarantee that the seam won’t move or get twisted while sewing.
• If you are making this seam on sleeves (A.K.A curves) make a basting stitch on the curve of the upper seam allowance to facilitate the process.
• Check twice before cutting your seam allowance! There is no way to put that fabric back as you might know. So make sure which one of the layers you are going to cut before doing so.

Flat Felled Seam vs Run and Felled Seam

A flat felled seam and a run and felled seam are basically the same. The only difference is where the two parallel stitches will end up. On the outside of the garment or on the inside.

If the parallel stitches are on the outside it will be a flat felled seam. 

This usually has a higher size thread outside for decorative purposes. 

That is why you can see them in a different color and clearly standing out on jeans and jackets.

On the other hand, a run and the felled seam are meant to be discrete. This seam will only have one visible seam on the outside of the garment.

Usually of the same color as the fabric.

If you watch a men’s dress shirt you will notice this seam on most of its construction. The reason being that a dress shirt is a garment that you use on your job or elegant events, so the cleaner the look the better.

Making a run and felled seam on any garment will prevent bulks on the inside and effectively prevent the seams from fraying.

Why anyone would use a Run and Flat Felled Seam?

In theory, women’s shirts should have the same construction process as men’s dress shirts, but the fast fashion industry has decided that our finishes are not as important as the men’s garments…

But let’s not dive into the gender topic too much.

The main reason to make mock Flat Felled Seams or other alternatives (explanation below)  in those garments is clearly the lack of time. 

Whether is industrially made or homemade this seam requires special extra steps to be done. 

A pattern fix, the cutting, and folding, or even a specialty foot.

Nevertheless, this is certainly a worth-the-time seam. I use it on all my lace fabrics, and of course on my dress shirts.

Take that fast fashion!

The Flat Felled Foot

The flat felled presser foot will make the entire job of sewing a flat felled seam in only two steps.

This is just another way to make this seam that will save you a lot of time on the sewing part.

All though there are other steps involved if you want to use this foot. First of all, you have to modify your pattern so the inner seam allowance is already narrower than the upper one. 

The cool thing about this foot is that you can sew without the worry of pressing between steps. And that just saves a lot of time.

If you want to sew garments that need this type of seam often, I definitely recommend that you get one of these presser feet.

FAQ:

1. Differences between Flat felled seam vs French seam.

A lot of people confused a flat felled seam with the french seam. All though both of these seams enclose the seam allowances they have totally different purposes, techniques and, uses on garments.

First of all, a French Seam is used on more delicate garments such as blouses, chiffon fabric clothes, lace fabric, and so on. 

They are used especially on sheer fabrics so the seam will look clean and neat from the outside.

But this seam “hangs” inside the garment like any other regular seam allowance.

Unlike the flat felled seam, which lies flat on the garment, making almost a seamless transition between the pieces of it.

2. Is there a Flat Felled Seam Alternative?

If you want to have the same finish as a flat felled seam but you want to skip all the work in between here is an option. Sew your seams as you regularly do.

Serge the edges together and the same for the seam. Then press the seam to one side and use a twin needle to topstitch on the outside of the garment.

3. How do you make a Mock Flat Felled seam?

A mock flat felled seam is a faster technique than a real Flat Felled Seam. 

To make it, you will only serge one edge of the seam allowances, and then trim down the other edge.

Then you’ll have to press so the serged seam allowance over the trimmed one.

Finally, make two parallel top stitches on the right side of the fabric. To do this you can use a twin needle or simply sew them with your regular needle.

This alternative works great if you are in a hurry but you still want the strength and finish of a true Flat Felled Seam. There is a great tutorial here for this mock seam if you want to check it out.

I hope you enjoyed this tutorial! If you did please remember to share it on Pinterest and click on the heart at the bottom corner of this page.

Do you have any questions about this technique? Please write them in the comments below and I will do my best to help you with it.

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