Mar 12, 2009

How to sew a fly zipper

I thought I would go through the steps of sewing a fly zipper. The first time I installed a fly zipper it probably took me an hour or longer. This took me about 15 minutes to cut out and sew. The more you do things the better you get so practice and you'll get better. I'm using scrap fabric because I already have a sample to show my students. I'm going to rip this apart so I can save the zipper.

First, I use small samples when teaching. I made and copied a pattern to teach in my class. It consist of 3 pieces. The front pant of which you cut 2, a fly and an underlap of which you cut 1 each.

With two right sides together sew the center seam of the front pants to the notch leaving room to install the zipper. Sew the bottom of the underlap. Flip and press your underlap. You can finish the notched edge of the underlap because you will see this edge in the garnment. If your fabric's going to fray you might want to zigzag or serge your edge.

One trick to doing the fly zipper - you want to press your seam not right at your stitch line but to inset it. When you sew your seam at 5/8" fold and press your seam 1/4". This allows the zipper to sit inside the fly. The whole reason for installing a fly zipper so you don't see your zipper. The more you can insert it the better it looks.

I forgot to take a picture of this step but you may want to finish the curved edge of the fly because it will be exposed. You can do this by doing a zigzag next to the edge of the fabric our serge the edge finished.

With two right sides together sew your fly to the right side of the pant. (when you put on your pants to wear them it will be the left side). Turn your fly in to the inside of the pants and press at the seam.

With the right side facing up pin the top of your zipper to the pressed 1/4" seam with the teeth of the zipper next to the fold. Then place your underlap under your zipper with the serged edge so that you don't see the underside of the zipper. Use the same pin's you used to pin the zipper to pin the underlap in place.

You only want to see one stitch line. This is why you pin all layers together. Sew using your zipper foot down to the bottom of the zipper. If your zipper is longer than needed you can cut the excess off after you finish the insulation.

Zip the zipper closed. Bring the fly side of the pants over and place the fold of the fly over top of the zipper and pin it in place. Your going to be pulling these pints out later when you sew the zipper.

Flip the fabric over and pin the zipper to the fly only. Pin it to the wrong side of the zipper. Pull you pins out on the other side of the fabric and unzip the zipper until it's open. Sew the zipper to the fly only.

When your finished zip the zipper back up and replace the pins to the outside of the fly to hold the fabric in place while you mark and sew the stitch that will hold the fly secure on the outside of the fly.

There are many different ways to mark your fabric. You want to mark the topstitch holding the fly to give you something to follow so you get a straight line and curve at the bottom. You can use tracing paper and wheel. Place the paper down on your fabric. Put the pattern on top and trace our your mark to follow. This will come out in the wash. (I marked it with some tailors chalk so you could see it better in the picture) After a while you will get better at doing this and you won't need a line to follow. This is the fun part of doing the fly zipper to me.

We're almost done...
If you look at your pants you buy at the store there's always extra stitching at the bottom of the zipper to give extra support. You can do this by going back and forth a few times or doing a zigzag stitch over the bottom of the zipper. After you do this you can pull the pins out holding the fly down.

Continue sewing your center seam from the notch up to the top of the zipper.

If your zipper is longer than needed you can do a few stitches across the zipper going back and forth and cut the zipper right below the stitch line.

And that's how you do a fly zipper.

If you don't understand any of these steps come in to any sewing class and I'll show you how to do it. Just bring in some fabric, thread and a zipper to class with you.

Until next time,
Enjoy your moments ~ make them "sew" much fun,


  1. Thanks for this tutorial. Since there are no patterns for little boys with zippers, and my DD and SIL want their Little Man to have
    Big Boy pants, this will come in very helpful!! I've put two zippers in without knowing what I was doing. They turned out ok, but this will make it so much easier.
    I am seriously considering starting a class to teach sewing. I'll start with beginners, then work my way up. I taught an heirloom class once and it was fun. I am also considering sewing for others on a bigger scale. I may need advice when the time comes.
    Your comments about my mother made me tear up. I do love her and I always knew she loved me; it's just weird to hear the words. She asked me to kiss her yesterday. Now, that's a first!!