A fly front zip is the fastening traditionally used on jeans, trousers and can often be found on skirts and shorts where the zip is positioned on the front of the garment. The zip is hidden from view by a zip facing or extension and is covered by a fly shield from the inside of the garment. Knowing how to sew one is a great skill to add to your sewing arsenal so we've prepared this handy guide for you to refer to.
The fly facing can either be a separate piece attached to the centre front seam or a continuous extension of the fabric of the main garment and can be positioned on the left or right hand side of the garment according to preference. It is worth considering that adding a separate piece will give a nice firm finish to the centre front edge. Traditionally women's zips are on the left side of the garment and men's are on the right, but nowadays you will most likely have garments with zips on both sides. I decided to go traditional when making this skirt (the Moss skirt by Grainline Studios) and positioned the zip on the left side of the garment, although for right handed people a zip on the right hand side of the garment is easier to use.
If adding a separate fly facing to the garment stitch in place along the seam line, press the seam flat then open before grading the seams to reduce any bulk. Understitch then press towards the fly facing.
Next you need to select the correct size zip or, if using a nylon zip, cut it down to the appropriate size and zig zag stitch over the teeth at the bottom of the zip to create a new stopper. The bottom stopper of the zip should be positioned just above where the centre front seam finishes and the stopper at the top should finish slightly lower than your seam allowance to allow for your waistband to be attached and still have a bit of clearance. For this skirt the seam allowance is 1/2" so I positioned the top of the zip 5/8" down from the top of the skirt panel marked by the orange pinhead in the image below.
Once you have selected/prepared your zip you will need to position it correctly on the fly facing or extension. The zip teeth should be 1/2" from the centre front. Measure your zip to check how far the teeth are from the edge of the zip tape, for most zips the teeth will be 1/2" away from the edge of the zip tape as shown in the image below.
Use tailors chalk or a chaco pen to mark where the edge of the zip tape should be positioned (i.e. 1" away from the centre front in this example since there is 1/2" of zip tape either side of the zip teeth)
Now apply a strip of basting tape next to your markings, which will allow you to fix the zip in place before stitching. If you haven't come across it before basting tape is your new best friend when it comes to sewing zips! It is a clear, soluble, double sided tape that washes away and is great for tasks such as this, especially seeing as it is also nice and cheap! Moreover if you get the positioning wrong you can just lift the zip off the tape and reposition it, much easier than basting stitches. In the image below I have left the white backing on the tape to make it more visible, but this simply peels off to reveal the sticky, transparent tape.
Open the zip and stick it in place using your markings and tape making sure it is also the correct distance from the top and bottom of the facing then machine stitch along the edge of the zip tape.
Stop about 3/4 of the way down, put your needle down and move the zipper to the top to allow you to reach the bottom.
Open the zip again and use a zipper foot (if purchasing a zipper foot make sure you purchase one compatible with your machine) to machine stitch 3/4 of the way down the edge of the zip teeth, stop, put your needle down, move the zipper to the top and continue to the end in the same way as before.
Repeat these steps on the other side of the garment attaching your zip to the seam allowance.
Check the zip is level and opens and shuts freely.
Next top stitch the centre front fold, this will give a nice neat finish and will also help to hold the fly facing in the correct position. Use a slightly longer stitch length than normal and a top stitching thread and top stitching needle. You can choose a contrasting or matching thread depending on the effect you are looking for. I chose a similar coloured thread to give this denim skirt a smarter look. Close the zip and push everything to the side then machine stitch down to meet the centre front seam stitching line. Using a zipper foot can help you to reach that stitching line.
Next you will need to top stitch the rest of the zip facing in place. Use tailors chalk to mark the lines on your garment marking the furthest line 1 1/2" away from the centre front fold and curving round at the bottom to meet the centre front seam. Draw a second parallel line about 3/8" away from your original marking and nearer the centre fold or however wide you wish the parallel stitching line to be and to match any other flat felled seams you have created on your garment. I used a chaco pen and a Dritz Esy Hem tool to make my markings.
Close the zip and top stitch along your markings from the top of the garment and round the curve to the centre seam.
Now we need to attach the fly shield. Line the raw edge of your fly shield up with the raw edge of your seam allowance and machine stitch in place using a zig zag stitch to finish the edges.
It should now look like this:
Lie the garment right side up, open the zip and stitch from the right side of the fabric next to the zip teeth using your zipper foot and stopping to move the zip out of the way as before.
Finally add some bar tacks between the parallel top stitching lines at the curved end of the top stitching using a zig zag stitch and testing on a scrap of fabric first. These stitches aren't just for decoration, but will also hold the fly shield in place.
And there you have it a fly front zip!
Have fun sewing!
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