How to sew a Flat Felled Seam

Looking to find a seam that is strong and durable?  The flat felled seam, or felled seam, is just what is needed. This is the preferred seam in jeans, denim jackets, and other casual garments that get rough and tough wear.

What is a flat felled seam?

The felled seam, or flat-fell seam, is a seam made by placing one edge inside a folded edge of fabric and then stitching the fold down. The fold encases the raw edges and protects them from fraying.

The fold is secured with edge stitching. It is useful for keeping seam allowances flat and covering raw edges, along with providing a strong and durable seam.

Learn more about sewing a flat felled seam by watching our video or keep reading this post.

What is the difference between a flat felled seam vs a French seam? 

Both the French seam and the flat felled seam are finished so that the raw edges of the seam allowance are not visible.

However, the French seam is a locking stitch that encloses the raw edges inside of a single seam. It is done on the wrong side of the fabric.

The flat felled seam is worked on the right side of the fabric.  A seam is sewn and pressed, and one side of the seam allowance is trimmed. 

The other side of the seam allowance is folded under the trimmed seam and edge stitched to make a very strong seam.

French seams are used for delicate garments, such as evening wear.  The flat felled seam is used for casual clothing that gets lots of tough wear.

What are the pros and cons of a flat felled seam?

The advantage of the flat felled seam is that it can be done on a regular sewing machine and uses only straight stitching.  It is a very durable and strong seam.

The disadvantages of the flat felled seam are that it takes longer than a basic seam, involves precise cutting, needs at least a 1/2 inch seam allowance and can be bulky and difficult to do on curves.

The flat felled seam tutorial is coming your way!

WHAT YOU NEED to sew a flat felled seam

• Two pieces of fabric
• Threaded sewing machine
• Iron
• Ironing board
• Scissors

INSTRUCTIONS: How to make a Flat felled seam

For this tutorial, we have used contrasting thread and fabric that look different on the front and the back.  This will help to see the stitches and identify the front vs. back of the fabric.

If you are stitching a flat felled seam, you may want to use a thread that matches the fabric.

STEP 1: Stitch the first seam

Position the fabric with the wrong sides of the fabric together.  This is different from a normal seam that has the right sides of the fabric together.

Sew a 5/8" seam or the amount specified in the pattern.  Remember to backtack at both the beginning and end of the stitching.

A sample sewn seam is shown below.

STEP 2: Trim one seam allowance

On a flat surface, lay the fabrics with the seam allowances facing up.  Trim one seam allowance to 1/4" from the stitched seam line.

Notice that the photo below shows that the other seam allowance is not trimmed.

Step 4: Press the seam allowance for the Flat felled seam

Press the seam allowance towards the trimmed seam allowance as shown in the photo below.

The seam is nicely pressed to one side.

In the photo below, the smaller seam allowance is shown under the untrimmed seam allowance.

Step 4: Fold the seam allowance for the Flat felled seam

Next, fold or tuck the larger seam allowance under, enclosing the trimmed seam allowance and press.

The photo below shows the untrimmed seam allowance has been folded and tucked under.  

Press it flat. The seam can be pinned down for ease of sewing and to hold it in place. Pin this folded seam allowance all of the way down the seam.

Step 4: Edge stitch the folded seam

Return the pinned fabric to the sewing machine and edgestitch very close to the fold. 

This will keep the raw edges neatly inside the folded seam allowance. Be sure to backtack at the beginning and end of the stitching.

The flat felled seam is finished!  It is strong and durable and ready for some tough wear!

The photos below show the front and the back of the seam.

Flat Felled Seam Sample - Front or right side of the fabric.

Flat Felled Seam Sample - Back or wrong side of the fabric