You may know the flat felled seam by another name: the flat-fell seam or a felled seam.
What is a flat felled seam?
With double stitching, this seam is very durable. This is one of the sturdiest seams available. You will find it on jeans, workwear, outerwear or other places where you don’t want any visible seam allowance on either the inside or outside of the garment. Two rows of stitching show on the outside of the garment and a seam line and one row of stitching show on the inside of the garment.
How to Make a Flat Felled Seam
Learn how to make a flat felled seam with this step-by-step tutorial.
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These seams aren't just for jeans, even though that is where we see them the most. They are perfect for any straight seam that you want to be durable with no seam allowances showing. They are perfect for straight side seams on jackets.
Materials
- Two pieces of fabric ready for a straight seam using the flat felled method
- Thread - either matching or contrasting for a decorative look
Tools
- Sewing machine
- Iron
- Pressing surface
- Pins
- Quilters ruler
- Cutting mat
- Rotary cutter
Instructions
- The seam lines for a flat felled technique should be straight seams. This method is not suitable for curvy sewing lines like putting in a sleeve or a collar.
Place your two pieces of fabric WRONG sides together and stitch with your seam allowance. It is recommended to have at least 1/2-inch seam allowance, preferably 5/8-inch seam allowance.
- Press your seam open. Next, you will trim one of the seam allowances to 1/4-inch. Think about your garment. The one that you trim will be bulkier on that side of the finished seam. If it is a side seam (like this example), you'll want to trim the side towards the back of the garment so that it is a smoother look from the front.
Here I've lined up my quilters ruler to be able to leave a 1/4-inch seam allowance.
- Here it is all trimmed up.
- Next, fold the larger seam allowance over the 1/4-inch seam allowance, enclosing it in the fabric. Gently pull the fabric around to keep it even and tucked in nicely behind the smaller seam allowance. This is what will make your seam and stitching even for the finished flat felled seam.
I do this by just folding with my fingers.
- Pin the folded fabric in place. As you can see, we are looking at the right side of the fabric and see the first stitching line near the line of pins.
- Next, go to your sewing machine. Using your topstitch foot, move your needle two positions to the left and begin topstitching, lining the bar with the folded edge. This secures the folded edge and gives the double line of stitching featured in the flat felled seam..
- This is all there is to it! Here is the finished flat felled seam on the outside.
- And, here is what it looks like on the inside. See - no raw edges or seam allowances showing either inside or out!
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What is a mock flat felled seam?
The mock version looks almost the same on the outside of the garment, but you do see both seam allowances on the inside.
To make the mock version, start by edge finishing your fabrics. Here I used my serger, but you could use an overcast stitch on your machine or zig zag. I wouldn’t use any of the edge finishes that add bulk to your seams.
Place your two fabrics together RIGHT sides together and sew your seam line. Press both fabrics to one side. This will be the side that you stitch to finish this seam.
Here is what the inside of this seam looks like. You can see I pressed the seams to the left.
Using your topstitch foot, move your needle two positions into the seam allowance and stitch. Then, switch your machine foot to the basic foot and sew 3/8-inch from the fold of the seam line. This will match the flat felled seam.
Here is the finished mock version on the right side of the garment:
I used both of the seam finishes on this dress. Here is the side seam with the true flat felled seam finish. I matched the double stitching to sew on the pockets and used the raw edge of the denim to finish off the top of the pocket.
Here is the bodice seam with the mock version:
And, just in case you are curious, here is the finished dress. Super comfy and I can layer sweaters when the temperatures are cooler.
What is the difference between a French seam finish and a Flat Felled seam finish?
The French seam is sewn wrong sides together too, but using a small seam allowance. Then another wider seam is sewn on the inside of the garment enclosing the small seam allowance. Generally, the French seam is used for delicate or sheer fabrics.
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