How to Sew a Fly Front Zipper | Closet Core Patterns

For a lot of people, the scariest thing about making jeans is the fly front. There are a lot of methods for installing them, and not all of them are easy to wrap your head around. We did a lot of research to find the best way to sew the Ginger Jeans fly front zipper, so hopefully these step-by-step photos will show you how easy it is to actually do!

Our method is a bit different than what you may have encountered before. In all our jeans patterns, from Ginger to our Morgan non-stretch jeans, we draft the fly extension into the actual front leg, rather than having it as a separate pattern piece you sew on later. If you're working with a pattern that does not have the fly extension drafted to it, check out our post on sewing a fly front zipper for trousers for instructions on adding it. That method is similar to this one, but the zipper position is reversed since women's trousers traditionally do up on the left side, not the right. However, all jeans zip on the right side regardless of gender (personally I find it so dumb that there is this distinction - can we please just make all coats, shirts and pants do up on the same side?!) I should also point out that if you are struggling with any of this, our Sew Your Dream Jeans online class walks you through all jeans construction from start to finish, and our sister store Core Fabrics has a beautifully curated selection of denim.

HOW TO SEW FLY FRONT ZIPPER

Before we sew our legs together, we need to finish the fly extension of the left leg. The fly extension on the right leg will be trimmed off eventually, so don't worry about it for now. Simply overlock or zig zag around the straight edge and as much of the curve as you safely can on your machine. When I'm serging, I try to fold the crotch curve out of the way and stop just before I reach the seam allowance.

Next, you will be sewing your two pant legs together at the front crotch seam. Starting at the center front notch, baste a straight line to the circle marking next to the bottom of the fly extension. You can draw a line with a ruler if this helps. You want a nice long stitch since you will be removing this stitching once your fly has been installed. When you reach the circle, switch to a medium stitch length, sew a few stitches, and backstitch just to the circle. Continue sewing normally along the 5/8" seam allowance.

Now it's time to cut a notch from the corner where your fly extension meets the regular seam allowance to the circle. Be careful not to cut into your stitching.

Finish that short crotch curve using an overlock or zig zag stitch - be sure to trim down to 3/8". This is the one seam that must be finished this way, even if you are flat felling your seams. Also, I have to apologize for my horrible serging in the following photos. My serger was having major timing issues when I shot this tutorial. Please don't judge me.

Press your fly extension open and your finished seam to the left on the inside.

Flip your jeans to the front, and sew two rows of double stitching to the right of the crotch seam, making sure your fly extension is lying flat and your finished seam is caught in the stitching. You can also sew just 1 row of topstitching along the crotch if you prefer the way it looks. Or, you can wait until your zipper is installed, go back and add the second row and stop sewing at the fly topstitching, finished off with a bar tack. It really is a matter of preference, so take a look at RTW pairs in your closet to see what works for you. I like the double line so that's what I've called for in the pattern.

Now it's time to insert your zipper. In the photos below, I am lining up the left edge of the zipper teeth to the center seam. I shot these pics before I sent the pattern out for testing, and a few people pointed out that they preferred their zipper to be set deeper in the fly so it doesn't peak out at all. If that's the case, align the left edge of your zipper tape to the center seam. Depending on the width of the zipper tape, this will set your zipper into the fly 1/2" - 3/4". It will not affect the size of the waist, just the location of the zipper. Make sure your zipper is face down.

Once your zipper is aligned the way you prefer, pin it into place along the right fly extension only. In general, I line up the bottom of the tape with the bottom of the fly extension. You want at least 1/2" between the bottom of the fly extension and the zipper stop since you will be topstitching here later and you don't want to hit the stop with your needle.

Using a zipper foot, sew close to the zipper teeth, ensuring you are stitching only to the right fly extension. You can sew another row of stitching along the right edge of the tape as well, but it's not mandatory since chances are your zipper tape will wind up being encased by the fly shield later on.

Flip the zipper and the right fly extension under. You will now have a strip of denim to the left of the front of your zipper. You may have a little more width than what you see here depending on where you aligned your zipper tape.

Stitch a line about 1/8" away from the folded edge of this strip using a zipper foot.

Flip your legs back so that the wrong side is facing you. If you grab the zipper and the right fly extension, you'll notice that you can now move it to the left. Fold it to the left as much as it will go without pulling the fabric. Pin it into place.

Sew close to the left edge of the teeth, and sew another row close to the edge of the zipper tape to secure it to the left fly extension only.

Your zipper is now sewn in! Round of applause. Turn your jeans over, and use the fly topstitching guide to trace a line on the front of your pants. Make sure the bottom of this guide is at least 1/2" below your zipper stop while still catching the fly extension below - I like to mark the location of the stop with a pin. It's really important you catch the extension below, or your topstitching won't have enough layers of fabric to stabuilize it. Trace another line 1/4" inside the one you just drew.

With the front of the jeans facing you, topstitch along those guides, making sure your fly extension is laying flat. Sew slowly around the corners, watching the needle rather than the guide to make sure your line has a nice curve. Stop stitching at the center front seam, and backstitch a few times to secure.

Almost there! Before we add our bar tacks to secure the zipper, we need to prepare the fly shield. Fold it right sides together and sew 5/8" along the angled edge. Trim to 3/8", snip the corner and press flat.

If any little corner pieces are peeking out you can snip them too.

Turn your jeans so the wrong side is facing you, and line up the folded edge of the fly shield to the finished edge of the left fly extension. Pin into place.

Depending on where you aligned your zipper tape, you may have to trim off a bit of excess fabric on the right fly extension. If you have a serger, sew the fly shield to the fly extension only, cutting off any excess as you go. If you're using a regular machine, you can finish this edge with a zigzag or overlock stitch, or wrap it in some bias tape. Again, please ignore my horrible serging below. Damn serger timing!

If you're serging, use a large darning needle to weave your thread tail back into your serged stitch so it doesn't unravel on you later.

From the front of your jeans, mark where you'd like your bar tacks to go. I generally sew them just above the where the topstitching curves, and just below the zipper stop. If you have any wonky topstitiching on your curve, you can hide it with some bar tacks!

Practice some bar tacks until you get the tension and width right. You can use regular thread in your bobbin, but you may have to tweak the tension to get a nice even stitch. I set my stitch length to .5 and my zig zag width to 1.5-2, which gives me a dense, strong bar tack. You basically want the same stitch you use for buttonholes here, so check your machine buttonhole function to get the right settings. When stitching, make sure your fly shield is lying flat - the bar tacks will help secure it in place.

Remove your basted stitching along the center front seam using a seam ripper to just above your topstitched lines.

AND YOU'RE DONE!! It can be a little confusing at first but once you get a handle on it, it becomes second nature.

If you’d like more help sewing professional looking jeans, consider taking our online video class. The Sew Your Dream Jeans Workshop will give you the tools and techniques to design, sew, and wear your very own custom pair of jeans with confidence.