Learn the step by step process of how to sew a front fly zipper to a pair of trousers successfully! The process of making a fly involves many steps that at times can be confusing to follow, even as an experienced sewist, and I hope this tutorial will help you make the process easier and more clear for you.
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The trousers I sewed a front fly zipper into are the Tatjana trousers from Just Patterns. Whilst making the Tatjana trousers I also made videos on:
- Sew perfect darts every time!
- How to make & attach belt loops
- How to sew single welt pockets [coming soon]
Want to sew your own Tatjana trousers? Buy the Just Patterns pdf pattern here.
Click here to watch the video, or click on the thumbnail above. Or if you prefer you can keep on reading…
The Components of a Front Fly Zipper:
Fly shield: The fly shield is placed on the garment’s wrong side to provide stability as well as a protective shield between the zipper teeth and your skin. The fly shield will often be made in a similar size to the fly facing.
Fly facing: In this tutorial, I am showing you how to sew a fly front zipper when the fly facing is drafted to the front leg pattern piece. Many tutorials and patterns call for the fly facing to be sewn onto the centre front instead, but I think this is an unnecessary step that complicates the process. If you are using a trouser pattern without the fly facing added on as an extension I suggest that you add it yourself before cutting your fabric.
The zipper: You can use any regular zipper for a fly front, but personally I prefer metal zippers. The length of your zipper will depend on if you make high waist or low waist trousers.
If you aren’t sure if your zipper is long enough for the trousers that you are making just measure your front leg pattern piece along the centre front from the circle marking towards the notch. Then subtract your seam allowance. Do not worry if your zipper is a little too long – you can always trim it to fit! Below I have some further advice on choosing the right zipper.
Tools & supplies used:
- Zipper – Even if I used a plastic regular zipper in the video I do prefer metal zippers or other more heavy duty zippers on a front fly. Sadly I couldn’t find a metal zipper in the correct length for these trousers – but once I find one I will replace it! This is because I find a heavy zipper stays in place better at the front fly when you sit down, as well as they can withstand the wear and tear jeans and other trousers have better.
- Bias binding (optional) – You can use other seam finishes if you prefer like an overlock stitch, but I find binding the seams helps to make a neat finish that feels soft to the skin.
- Fusible interfacing – This is used to strengthen the fly shield, fly facing and fly edge at the side which will not have a fly.
- Sewing machine needles – I used Univeral sewing machine needles for this project, but if you are sewing a front fly zipper in a pair of jeans you want to make sure to use denim sewing machine needles.
- Zipper presser foot & a standard presser foot – I used my standard presser foot A interchangably with my walking foot throughout this process.
- Thread – I used Gütermann’s regular cotton thread in navy througout this project both on the regular seams, as well as the top stitching. If you are sewing a fly front on jeans you would want to have one thread for regular seams and another for top stitching. You might want to consider this for other trouser styles as well.
- Steam Iron – I love my Rowenta DW6080U1 Eco Intelligent Iron.
How to sew a front fly zipper step by step:
- Iron on fusible interfacing on the fly shield, the curved edge as well as the straight edge of the front pieces and any other areas that require interfacing on your trousers.
- Make sure that the circle marking where the zip opening will end is correctly marked on both the right and left front pieces. Also, make sure that all other notches and other pattern markings are correctly transferred from your pattern.
- Finish the edges of the inseams on both the back and the front as well as the crotch seams with an overlocker – or any other seam finish you prefer.
- Then bind the curved edge of the fly facing. Once that is done fold the fly facing inward towards the wrong side along the centre front line and press in place.
- Fold the fly shield along the middle lengthwise. Then stitch the slanted edges with a 1/4″/ 6 mm seam allowance. Please note that I will use this as the standard seam allowance throughout this tutorial unless I say otherwise.
- Turn the fly shield to the right side and press.
- Then baste stitch the zipper to the fly shield, make sure that the zipper stops 5/8″ / 1,5 cm below the top raw edge.
- Place fly shield with the zipper facing down on top of the left front leg. Stitch the fly shield with a 1 cm / 3/8 ” seam allowance right sides together making sure that the zipper is sandwiched in between.
- Once that was done I bound the raw edge with bias binding.
- Place the right front leg on top of the left leg and the fly shield right sides together. Start to stitch the crotch seam 5 cm/2″ away from the inseam until you reach the circle marking.
- Open the trousers and unzip the zipper, then unfold the zipper shield from underneath the left front. Press if needed.
- Then edge stitch left front seam through all the layers, including the fly shield.
- Close the zipper and overlap the front right over the left front by 6 mm/ 1/4″ and pin along the centre front, making sure that notches match.
- Now turn your work to the wrong side, and fold the fly shield out of the way. Make sure to pin the side of the zipper not yet stitched to the fly facing ONLY! Stitch in place using a zipper foot, making sure to only stitch through the facing.
- Move shield out of the way then topstitch the fly 3,5 cm/ 1″ 3/8′ parallel to the centre front.
- Once that is done it’s time to secure the fly to the fly facing by stitching them together diagonally at the bottom.
And your front fly zipper is now complete!
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