This article with video shows how to sew a flat felled seam finish using a sewing machine.

How to Sew a Flat Felled Seam - Skirt with flat felled seam finishes on denim

Hey y’all, today we’re going to be talking about how to sew a flat felled seam. This is a seam finish that you can do with a regular sewing machine. In this post I’ll include step by step instructions with photos as well as a video demonstrating how to flat fell your seam.

Right side and wrong side of a flat felled seam on denim

What is a Flat Felled Seam?

Flat felling is considered a self enclosed seam finish, meaning that all the raw edges are enclosed within the seam. The seam is typically combined with topstitching. To create it, you will stitch,  wrap the raw edges of the seam allowance around each other, and stitch again. A flat felled seam is a very sturdy seam and suitable for heavy fabrics. Therefore you often see it used on garments like jeans or denim skirts. You can do this seam finish on a regular sewing machine.

Pros: Can be done with a regular sewing machine with only straight stitching, very strong and durable seam.
Cons: Takes more time, precise fabric cutting, seam allowance sewing, and trimming is key, needs at least 1/2 inch width seam allowance, can be bulky, hard to do on curves.

A flat felled seam sewn on denim fabric

Making the Seam

First decide whether you want to sew starting with wrong sides together or right sides together. Starting with wrong sides together will give you a ridge on the outside like you normally see on jeans. It is the type finish I used on this skirt. If you do this with right sides together, you’ll have two lines of stitching visible on the inside and one line of stitching visible on the outside next to the seam.

You’ll also need to think about which way you want to press the seam allowances because that will affect which of the seam allowances you trim and which one you press around it. When I sew this type of seam on the right side of the fabric, I tend to press seam allowances away from the center front. At the center front or center back, you can choose which way to press. This may be influenced by another design element, for example a zipper fly (press folded edge away from the fly stitching). On shirts you want to press the shoulder seam allowance toward the front, etc. You can also check ready to wear clothes to see which way the seams are pressed.

Denim skirt front and back with flat felled seams and jean cut off shorts with flat felled seams

Once you’ve made those decisions, watch the video below or on YouTube here to see how to sew your seams. You can also use the illustrated step by step instructions below the video for reference.

Illustrated Photo Guide to A Flat Felled Seam

How to sew flat felled seams

Time needed: 10 minutes.

How to Sew a Flat Fell Seam

  1. Stitch

    Stitch your pieces together with at least a 1/2″ seam allowance. If you want the double topstitched ridge on the right side (as seen on jeans), start with fabric pieces wrong sides together. Otherwise place pieces right sides together.

  2. Press and trim

    Press the seam flat and trim one seam allowance down to 1/4″. Fold and press the other seam allowance raw edge 1/4 inch toward the seam.

  3. Wrap

    Wrap the folded seam allowance around the trimmed raw edge of the shorter seam allowance. Press away from the seam line. Pin if desired.

  4. Stitch again

    Stitch down close to the wrapped/folded edge. This stitching will be visible on both sides of the finished seam, so make sure to choose your top thread and bobbin thread accordingly.

Seam pressed flat to trim seam allowance

Tips for Success

For really nice flat felled seams, here are some tips:

  • If you’re not confident you can sew a straight line just using the guide on your machine, consider marking the seam line before stitching it. Just make sure your fabric marking choice will wash out by testing on a scrap of your fabric.
  • Consider pressing the seam open as shown above and using a rotary cutter for trimming. This ensures that you won’t accidentally cut anything besides the seam allowance you intend to trim.
  • Starch can be helpful to press the fold into the other seam allowance.
  • You might also want to use tape instead of pins to hold the edge of the fold in place as you stitch, this can help make sure there aren’t bumps in the edge where the pins were. Remove the tape after stitching.
  • Consider the direction you want to press the seam allowance. I detailed this more in the Making the Seam section above.
  • Move your needle position (if your machine has that option) instead of your presser foot to line up the edge stitch for the second line.
  • Use your iron and ironing board and press well. It’s nearly impossible to get a clean finish on your flat felled seams without pressing.
  • Using contrast topstitching thread will make any mistakes more obvious. If that might bother you, keep your top stitching matched to your fabric.

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