Flat fell seam tutorial // Closet Case Patterns


One of my favourite things about designing patterns is thinking about the best way to finish things; pretty guts are very important to me (team #prettyguts). When I started working on the Kelly Anorak, I knew flat fell seams would play a major role. Essentially a sturdier version of a french seam in that all the raw edges are enclosed, flat fell seams are great when the right and wrong side of the garment need to look great, and be strong and durable enough to last a good, long time. They are commonly used on jean jackets for just this purpose and have quickly become one of my favourite seam finishes.

While I’ve covered flat fell seams before in our Ginger Jeans sewalong, the process for Kelly is slightly different, and I wanted an extra opportunity to fan away the flames of fear some of you may have about trying them. It’s essentially sewing a straight seam with a few extra steps, and it is 100% worth your time. If you’re feeling lazier and have a serger, feel free to use a flat faux seam which is explained in our instructions. Either way, you’ll want to sew these durable seams along the front yoke, side seams and one of the arm sleeves (the other will be impossible to flat fell once the sleeve is assembled in a tube).


The first step is to sew your seam at the 5/8″ seam allowance with right sides together. In this example I am sewing the front coat to the front yoke.


Now, depending on which way you want to press and topstitch your seam, one of those seam allowances is going to wrap around the other. In this example we are pressing the seam up, so you will want to trim the yoke seam down to 1/4″. You can use regular scissors, but I absolutely love applique scissors for grading seams since the duckbill part ensures you aren’t cutting the other seam by accident. If the seam is straight, I often use a rotary cutter for speed and accuracy’s stake.


Once the “under” seam has been graded to 1/4″, press the entire seam up, so that the wider seam is on the top.


At your ironing board, use your fingers to fold the top seam around the seam you trimmed.  Try to do this as evenly and consistently as possible, and press into place with lots of steam.


This seam now needs to be topstitched into place. You can sew from the right or wrong side of your fabric. If you sew from the right side, make sure you use lots of pins to keep that seam folded in place. If you sew from the wrong side, you can just use your fingers to make sure it stays tucked under as you sew as I did below.


Here it is from the right side once its been stitched down.


Some people prefer to make their flat fell seams with the wrong sides together first. Feel free to try it that was as well, but just keep in mind you will have two visible lines of stitching on the right side: your construction stitch, and the topstitching to seal everything together. I personally prefer to “hide” the folded part on the wrong side just in case my pressing and cutting wasn’t 100% perfect.

Hope this helps you make a sturdy Kelly of your own!

  • Cari

    The first sentence under the heading, sewing a flat felled seam, says start by sewing wrong sides together. I think you mean right sides together at that point.

    • You’re absolutely right Cari – thank you!

  • I love flat fell seams too! I even did one down a centre back seam in silk that to this day I love to see and feel 🙂 It was a tricky business though I have to say – it’s a flowy silk – I actually taped it down with wonder tape before sewing and that worked pretty good 🙂

  • mrssandoval

    I have to wonder: what kind of sewing machine do you have? Brand? Model? I’ve got the Pfaff Ambition and although it’s a great machine (IDT and computerized), it’s not great for seams. I do have a felling foot, though!
    I looked at the Kellys from others and now I feel blah. I, too, bought an army green twill (but mine is sanded and brushed!) I wanted to do a nod to my dad by using a hippie print lining because he was in the Vietnam war.
    Anyways, my Pfaff is not friendly with thick seams. She makes thread nests and will repeatedly sew one area over and over. If she does go over the seam, it’s ugly.
    I’ve got a tool for thick seams, but it doesn’t work well. I can’t afford a Bernina, but I’m getting a stronger Pfaff this spring (and a new Babylock!)

    • I have a Bernina. You might want to consider getting a vintage Bernina. I may be getting the 1130 next week fi I can meet up with the person on Craigslist 😉

      • mrssandoval

        Really?! I had a chance to get the Arista 180, but balked at the last minute because I’m afraid of used machines. Now that you and everyone says that, I should reconsider. I just really need a new serger. I bought the Babylock Diana and I hate it. My Brother was better! So, I’m buying the BL Imagine, because everyone recommends it for garment sewing.
        Ooh, while I got you, how do you recommend I measure my shoulders? I was told bone to bone, top of my shoulders on top of the blades, across horizontally. I can’t write it down right, so I’m trying to describe it. I just want to get this right! I wanna mess with the flat pattern adjustments first because I’m better at that.