Adding A Side Zip to Elastic Back Pants

Welcome to my version of inserting a side zip into a pair of elastic back pants!

Before I dive in to all the pictures and explanation of this process, I want to emphasis that this is only ONE of a myriad of ways that you could go about inserting a zipper into a pair of elastic back pants. There is no one RIGHT way or WRONG way to do this. There are merely different ways, and they are all based on personal preference, fabric choice, styling, etc.

The one way I am showcasing in this blog post happens to involve a coil pressed zipper (the plastic kind with the raised teeth), as it's what I had on hand. You could easily replicate this same process using an exposed metal zip, or even take a page from Mia of Sew North and use an invisible zip like she does in her Pietra Pant Hack!

Now that my little disclaimer is out of the way, let's jump in!

This post is based off of the Chandler Pants pattern, but note that it can be used for any pants pattern with an elastic back waist!

You might be wondering "Why would I need a zipper for an elasticated pant?"

Well, for some of us, our hip to waist ratio is so different that we must tighten our elastic to a point where it cannot easily slide over our hips. Or, if we don't pull our elastic tight enough, we run the risk of having our pants constantly falling down if we aren't wearing a belt (which is what happens every time I wear my other two Chandler's!)

So, if you have a waist to hip ratio that requires a little extra love to get your pants on and off a little bit easier, this tutorial is for you!

If you are following along form the Chandler instructions, feel free to follow the sewalongs / your instructions up until Step 22a.

To start, you will want to finish the edges of one side of your side seams completely. It doesn't matter if it is the left or right side, just pick whichever side you intend to have the zipper placed.

If you have a facing like in the Chandler's or the Closet Case Pietra pants, finish your seam only from below the facing edge down to the hem line.

For the back of your pant, you will want to finish the entire side seam (waistband facing and all) before you sew your elastic casing closed or anything like that.

Ok, we will meet back here again once you are to the point in your instructions that walks you through inserting your elastic.

You ready for your elastic? Awesome! Slide your elastic through your back waistband casing. Now, instead of basting your elastic in place really close to your seam allowance edge (like 1/4" or so) we are going to baste it in place just outside of your seam allowance edge.

For the Chandlers, whose seam allowance in 1/2" (1.3 cm), we would baste the elastic in place around 5/8" (1.6 cm). The name of the game is reducing bulk, and by basting the elastic just outside of the seam allowance, we are able to remove more  of the bulky elastic than if we were to baste it within our seam allowance. 

Once basted in place, flip your seam so that you can see most of the extra elastic, as shown below.

Then trim off your elastic as close to the basted edge as you can get.

 Now it's time to insert the zipper! With right sides together, pin your pant / short legs along the side seam that is going to host your zipper. Make sure to stop your pins just below the zipper stop.

If you want, you can measure your zipper to get an exact measurement on where this point should be, or you can lay out your zipper next to your seam and mark it with a pin (which is what I did!)

Don't forget to take into account where the top of your zipper with begin as well. For us, we want the tape to extend a little bit above the back waistband so that we are able to hide the zipper tape in a future step.

 Alright, since everything is pinned up, you are ready to sew your side seam together. Starting from your pin mark, sew your seam closed all the way through to the hem line.

For the other pant leg, feel free to follow your instructions as they suggest. For the Chandlers, that means jumping back to step 32.

Once you are finished with both side seams, grab your garment and head over to your iron- we need to press our zipper side seams open!

Not only do we need to press the seams open, we also need to press the unsewn portion of your side seams 1/2" (1.3 cm) back.

This is what it should look like on the right hand side- just a bit of your basting should be seen.

We are finally ready to insert our zipper- the moment we have all been waiting for, right?

On the back side of your pants, unfold the top portion of your ironed edge and place the right side of your zipper facing the right side of your pants. Make sure that a small portion of the zipper tape is sticking just above the waistband edge.

Fold the little bit of tape that is sticking up down towards the wrong/ back side of your waistband.

Now fold your seam allowance back along the ironed edge. This will completely enclose and hide your zipper tape.

When it all looks good, pin your zipper in place along the seam edge.

For the front of your pants, if you are working with a facing, you will want to fold the extra little zipper tape back at a 45 degree angle.

Then, fold your facing over your zipper (the wrong side  of the zipper should be facing you from the inside of your garment) to completely enclose the top portion of the zipper tape within it's seam.

Doesn't that look so nice and clean?

Go ahead and pin your zipper all along the front & back, as shown below. If you measured correctly and your front and back seams line up in the right places, you should have no weird puckers anywhere (which is also a benefit from ironing earlier!)

I know the top edge looks like it doesn't line up properly from front waist to back waist, but I promise it does! The way I pinned on one side vs the other makes it look as if the back waist band is sticking up much higher than the front.

Now, we topstitch!

I did't change my machine foot to insert this zipper because my regular foot never has a problem sewing along a plastic coiled zipper. If yours does, or if you are just more comfortable with it, feel free to swap out your sewing machine foot to a zipper foot.

When you are ready, go ahead and topstitch/ edgestitch your zipper into place. I sewed about 1/8" (0.3 cm) away from the seam edge, which coincidentally was directly on top of my basting stitch from earlier!

Keep sewing along until you get to your zipper head. At some point, it will simply be in the way. To get around this issue (without having to remove your garment from under the machine), put your needle down through your fabric right before the zipper head.

With your needle still down, lift your foot...

... and zip your zipper closed.

Put your foot back down, and continue sewing your zipper into place. Repeat those same three steps the next time you run into your zipper head (in like two seconds since it's just on the other side!)

I also like to add a few extra stitches to my back zipper seam along the top edge to ensure that my zipper lies flat and doesn't scratch my waist.

Success! You have just inserted a zipper into your elastic back pants! You can now continue on in your directions with fitting the elastic to your waist without having to worry about whether it will be too difficult to shimmy in and our of your pants, cause you have a zipper!

One last note- For some, you may have to pull your elastic so tight to get it to fit your waist properly, that you may be unable to sew those stitches you typically find in elastic waisted garments. You know, like these:

If that is the case, no worries! Feel free to find a few places to tack your elastic down vertically. This will ensure that your elastic doesn't twist while you are wearing your pants, and it'll keep the gathers a bit more evenly distributed.

I hope this tutorial helps those who need to add a zipper like I do! I love having the comfort of elastic with the ease of popping in and out of my garment without having to do a little dance (unless I want to !)