Nothing Is What It Seams: Working with Flat Felled Seams

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Nothing Is What It Seams: Working with Flat Felled Seams

Today we’re all about turning things inside out, as we take a deeper look into flat felled seams and how to get a consistently neat finish on the inside of your garments.

Flat felled seams are strong and durable, and that’s why they’re usually used on sturdy fabrics like denim, corduroy, canvas, and upholstery fabric. Because of its proven grit and staying power, it’s a seam that’s especially popular with makers of children’s wear.

While flat felled seams aren’t something you’ll use on every project, it’s a nice skill to master, especially if you enjoy working with medium to heavy fabrics. It’s most useful in making pants, especially jeans.

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Anatomy of A Seam

Basically, a flat felled seam is an overlapping seam that’s sewn flat; check out the seams on a pair of jeans as a best example. A flat felled seam has no visible inside or outside seam allowance. Rather, the seam allowance is enclosed within the seam; a seam within a seam, if you will!

Check out this video for a refresher course on the importance of seam allowance:

Video Source: YouTube/Professor Pincushion

While commercial sewing machines crank this work out in no time, the good news is that you can do the same at home with nothing more than a straight-stitching sewing machine with a standard pressing foot, scissors, an iron, strong, sturdy thread, and a lotta sewing pins.

If you’re new to this technique, it’s a good idea to practice on fabric scraps before taking on bigger projects. Practice, as they say, makes perfect and will help you create professional-grade flat felled seams that you can be proud of!

Getting Started

Before diving into the steps, this video will give you a good overview of how it’s all put together:

Video Source: YouTube/Howcast

A flat felled seam can be sewn from either the inside or outside, and the nature of the project/garment and fabric used will often determine which technique you should use. For jeans, sturdy handbags, or thick shirts, it’s best to go with the outside technique.

To begin, sew a seam with your usual seam allowance. Press both seam allowances over to one side, and then trim the width of the bottom seam allowance in half. The accuracy of your trimming skills will come into play here, so use your rotary cutter or scissors like a surgeon and work slowly and carefully.

Fold the larger seam allowance up and over the smaller one to just before the seam line. Stitch and press into place. Accuracy is important here, too, so at this point be sure to fold and press carefully and use a seam qauge to get an even fold. Then fold the whole seam over on itself so that the raw edge is hidden. Press again.

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Back on the sewing machine, you’ll want to edge stitch close to the free edge, keeping an even distance from the original seam line. Here’s where using an edge stitching or blind hem foot will help you stitch close to the fold, so if you got ‘em, use ‘em!

When finishing the piece, top stitching a third line of stitching just inside the original seam allowance will give extra strength and can be used as a cool design effect. You can always go with the iconic blue jeans stitching but if you want to make a splash, here’s your chance to get creative with your use of threads and stitching lines.

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The Jean Genie

Since flat fell seams and denim were meant to be together, mastering this technique offers you a great way to repurpose those denim jeans or jackets that have been lurking in your closet since 1987. There’s no end to what you can fashion from old, soft denim; think skirts, messenger bags, oven mitts, the outside of quilts, table place settings, even Christmas stockings. Sew on the logo of a sports team or rock band and you’ve got the ultimate personalized hand-crafted gift! And since you’re re-using something that might have ended up in a landfill, you’re helping the environment, too! We call that a win-win!

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