How to Sew a Flat Felled Seam

  • 01 of 05

    What Are Flat Felled Seams?

    Finished flat felled seam
    Debbie Colgrove

    A flat felled seam has no visible seam allowance, inside or out.  The seam allowance is enclosed within the seam. 

    Flat felled seams are very strong and very durable which is why we are most familiar with flat felled seams being on strong durable fabric such as denim and on jeans.

    Commercial sewing machines have a system that does the seam in one step but it can be accomplished at home with a straight-stitch sewing machine, scissors, and an iron.

    It's just a matter of following these steps and sewing the seams one step at a time. Pressing is a very important part of creating a flat felled seam at home, as is special extra-strong, denim thread which is available for home sewing.

    Note: If you have never sewn a flat felled seam, grab some scraps of fabric and practice before attempting it on your intended item. Practicing will allow you to understand each step and gain the confidence to make a professional-looking flat felled seam.

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  • 02 of 05

    Start by Sewing the Seam on the Right Side of the Fabric

    Sew the seam to the right side of the item by sewing with the wrong sides of the fabric together.
    Debbie Colgrove
    • Unlike a regular seam, to begin sewing a flat felled seam, you place the wrong sides of the fabric together, sewing the seam on the right side of the fabric with the wrong sides of the fabric together. Every step of your sewing while sewing a flat felled seam will be seen from the outside of the garment or item you are sewing.
    • Thoroughly press the seam the same way it was sewn to set the stitching on the fabric.  
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  • 03 of 05

    Trim the Back Seam Allowance

    Trimming the back seam allowance in half
    Debbie Colgrove
    • Find the front and back of the garment.
    • Trim the back seam allowance in half, cutting neatly and as straight as possible. Sharp scissors are a must so that you have a smooth edge and aren't fighting fraying threads as you create the seam.
    • Press the entire seam allowance to the back side. Press it open and then to the back if you need to in order to get a smoothly ironed seam facing the back of the garment.

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    • 04 of 05

      Enclosing the Seam Allowance

      Press the larger seam allowance in half, enclosing the trimmed seam allowance.
      Debbie Colgrove
      • Press the larger seam allowance in half turning under the raw edge so that it just about meets the originally sewn seam. This will cause the wider seam allowance to enclose the trimmed seam allowance.
      • Press the turned-under seam allowance flat as the finished seam will be sewn. Use a press cloth if you need to prevent a sheen on your fabric but thoroughly iron the seam allowance so that the fold is well pressed before you begin to sew it in place.
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    • 05 of 05

      Sewing Down the Enclosed Seam Allowance

      Stitching the seam allowance down
      Debbie Colgrove

      When you sew the final step, you will want the stitching to be an even distance from the original seam line of stitching and not go off of the folded edge. This final stitching will enclose the seam allowances so fraying is not possible and the finished seam is very strong and durable.

      • Top stitch the pressed-under seam allowance as close to the folded edge as possible. Sewing straight lines and using the seam guides on your presser foot are essential to your finished seam looking professional. Changing needle position, when possible, can also help you have the stitching exactly where you want it on the edge of the fold.
      • Stitch the seam allowance down, keeping the stitching as close to the fold as possible without going off the edge of the fold and keeping the stitching an even distance from the original seam line of stitches.