Home sewers often resort to techniques that result in a faux flat felled seam. This often starts of by sewing right sides together at 5/8″ then trimming one side of the seam and folding over the longer side to encase the raw edges.
Although this achieves the goal of encasing the raw seams it does NOT address the strength feature of the original flat felled seam that Levi Strauss used to ensure the inside leg seams would withstand the mine works daily abuse they put on their jeans.
Fast forward to today’s lightweight, stretch denim with Lycra and you only compound the problem. After hearing from several home sewers who have worked hard to complete their own pair of jeans only to have the stress of the crotch area expose the seam I decided to create a video to demonstrate how a home sewer can sew a professional flat felled seam successfully.
To be clear a flat felled seam should display 2 rows of stitching on the right and wrong side of the fabric and each stitch should be sewn through 4 layers (2 from each side of the seam) of fabric. Any seam that includes only one stitch sewing through 4 layers is a faux flat felled seam in my opinion. This doesn’t mean that it won’t work on your project though. So if that works for you go for it. It is certainly easier for most to sew, which is why so many home sewers use it.