The flat felled seam is a flat, comfortable seam suitable for medium-weight fabrics and garments requiring maximum durability.
A flat felled seam makes sportswear and casual wear look very professional and if you have an active little toddler running around, these seams are hardwearing and perfect for overalls and rompers. They are comfortable because the bulk of the seam is on the outside.
The flat felled seam is ideal for denim and cotton fabrics but may be too bulky for heavier material. It is more difficult around curves and is best used on straight seams for beginners.
Flat Felled Seam: Step by Step Video
Here is a video I made to show you how easy it is to sew a flat felled seam. Subscribe to my YouTube channel for weekly sewing videos.
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How to Sew a Flat Felled Seam
Before you start, check your seam allowance width. It should be at least 1/2 inch (12mm) wide. Any less than this will result in a really narrow seam that will be hard to sew.
Do a test of the flat felled seam on a scrap of fabric and adjust the seam allowance if necessary.
Step One: Place your fabric pieces with wrong sides together and stitch along the normal seam line.
Step Two: Press the seam open.
Step Three: Trim one side of the seam to a width of 1/8 inch (3mm).
Step four: Press the wider (untrimmed) edge over by 1/4 inch (6mm).
Step Five: Fold the wider, pressed edge over to encase the trimmed edge.
Make sure the pressed and folded edge is the same width all along the seam.
Step six: Stitch along the open edge of the seam.
Beginners: Use pins or hand baste to secure the seam before you sew.
You can use your regular all-purpose sewing foot, but for really accurate and neat stitching, an edge stitching foot can really help.
See how it has a guide in the center which will run along the edge of the seam. You will need to move your needle slightly to the left rather than leaving it in the center as you would for normal sewing.
Further Reading: How to use an edge stitching foot
Sewing a Flat Felled Seam around a Curve
If you are using the flat felled seam around a curved edge, then clip the trimmed edge of the seam before encasing the seam as this will give more elasticity to the seam and allow you to turn a corner.
However, it is worth noting that the flat felled seam is best suited to the straight path of your seam line.
Flat Felled Seam
Run your fingers along the completed article and see what a smooth finish you have on the inside and a tough edge to the outside. This is a rugged, but smart seam, and a winner for sports and outdoor wear!