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How To Neatly Sew a Lapped Zip with a Concealing Flap +Video

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A lapped zipper is a way of sewing a regular zipper in a concealed way. With this technique, a folded flap of fabric covers the zipper and offers a mostly invisible finish. You can use it on side seams or the center back/front seams of trousers, skirts, tops, dresses, jumpsuits, and even cushions and bags. It involves some visible L-shaped topstitching to secure the zipper into place, but you can always switch to a hand-sewn prick stitch to achieve a less visible look.

A lapped zipper usually closes left over right, meaning the right side of the fabric will form the underlap that will be hidden by the lap of the left. This application makes it easier for right-handed people to access the zipper pull, but if you’re left-handed you can always reverse the directions to have the lap on the right side.

Two alternatives to lapped zippers are centered zippers and invisible zippers. With centered zips, two flaps of fabric meet at the center to conceal a regular zipper, and it features some topstitching to secure the zipper just like in lapped zips. With invisible zips, you’ll need to use an invisible zipper but you’ll achieve a completely hidden look with no visible topstitching.

Contents list:

Preparation (install zipper foot, interface fabric, machine settings):

What is a zipper foot?

A zipper foot is a presser foot that allows you to position the needle in a way that’s closer to the zipper teeth. There are different styles of zipper feet for domestic machines, but most of them feature cutouts on either side so the foot curves around the zipper teeth you’re sewing. With these models, you need to snap them onto your machine’s ankle from the right or the left depending on which side of the zipper you’re sewing on. 

How to install a zipper foot on your sewing machine:

  1. Start by removing the existing presser foot on your machine. On my machine (a Pfaff Ambition 630), this is done by simply pushing the presser foot down, but on some machines, you may need to pull the presser foot release lever to drop the existing foot or even use a screwdriver to release the foot from the ankle.
  2. Next, decide which side of the zipper you’ll be sewing on. If you’re going to start by sewing on the left side of the zipper, you’ll need to attach the ankle to the right side of the zipper foot, and vice versa.
  3. Once you know which side of the zipper foot you want to attach the ankle to, you can either push the foot up to the ankle or lower the ankle down towards the bar at the back of the foot until it snaps into place. Make sure to check your machine’s manual to see if there are different instructions for changing presser feet. 

Machine settings:

  1. Select a straight stitch with a length of 2.5 mm. 
  2. Position the needle so that it’s close to the zipper teeth. This is done by changing the stitch width or changing the needle position. Slowly turn the handwheel toward yourself to check that the needle isn’t hitting any part of the zipper foot and that it’s sewing close to the zipper teeth without piercing the actual teeth.

Preparation steps:

  1. Apply some lightweight fusible interfacing to the edges of your pattern pieces where the zipper will be sewn. The interfacing should be around the same width as your seam allowance or a little wider. The length should extend about 1” (2.5cm) below the bottom stopper of your zipper. You can either apply the interfacing strip by aligning its edge with the raw edge of your fabric, or center it on your seam line (in this case you can use a narrower strip of interfacing).
  2. Finish the center back or front edges of your pattern pieces. You can use an serger/overlocker machine, a mock overlock or zigzag stitch on your regular sewing machine, bias binding, or pinking shears depending on your fabric and project. More finishing details are here.
  3. If you’re sewing a facing to clean up the top of the zipper, interface the facing pieces and finish the free edges using your edge finish of choice. You can do a small hem, use a serger/overlocker machine, a zigzag stitch, apply some bias binding, or sew the facing to the interfacing right sides together, and then flip the interfacing to the wrong side and fuse it for an extra clean finish.

How to sew a lapped zipper:

In this tutorial, I’ll show you how to sew a lapped zipper by machine. This method involves basting the seam closed, sewing the zipper to the underlap side, and then topstitching it into place from the left side. 

For the sample I prepared, I’ll be inserting the zipper into the center back seam, and referring to the right and left pieces as they are worn on the body. You can, of course, use this tutorial to sew a lapped zipper to a side seam or even into a cushion or pillow. I’m using a contrasting zipper and thread color so that you can clearly see the details, but you’ll want to use a matching color for the zipper and thread for the most well-hidden look (unless you’re deliberately going for a contrasting pop of color). 

Uses

  • Center back / front seams of tops, skirts, dresses, jumpsuits.
  • Side seams of trousers, skirts, dresses, jumpsuits.
  • Pillows, cushions, zippered pouches, bags.

Supplies

  • Two pieces of fabric that will be joined by the zipper, with the edges interfaced and finished
  • A regular zipper
  • Zipper foot
  • Standard presser foot
  • Sewing pins
  • Hand sewing needle and thread for basting (optional)
  • All-purpose polyester thread for permanent stitches
  • Sewing machine
  • Iron
  • A clear quilting ruler
  • Fabric marking tool of your choice, or washi tape

Step-by-step instructions:

  1.  Start with your pattern pieces prepared according to the preparation steps above. Place the two pieces right sides together and pin along the center back seam.
  2. Place your zipper on the center seam. The top of the zipper teeth should be placed just under the seam allowance at the top of the center seam. Mark where the bottom stopper of the zip lands on the center back seam. 
  3. Set your sewing machine to a straight stitch with the longest possible stitch length, or a basting stitch if your machine has one.
  4. Starting at the top, sew a basting stitch until you reach the mark that you made in step 2.
  5. At the mark, stop and decrease your stitch length back to 2.5 mm. Continue sewing down the center back seam, making sure to backstitch at the beginning (where the mark for the bottom stopper is) and the end. 
  6. Press the seam allowances open.
  7. Place the zipper on the wrong side of the center back seam with the zipper teeth down. The right side of the zipper (where the zipper teeth are) should be touching the wrong side of the fabric. The bottom stopper of the zipper should be on the mark you’ve made in step 2. 
  8. Pin the right side of the zipper tape (as you’re looking at it) to the seam allowance underneath it. The pins should be on the left side of the garment as worn, but because you’re looking at the wrong side of the garment you’ll be pinning the right-hand side of the zipper tape to the seam allowance on the right-hand side. If you prefer, you can also baste these layers together using a hand sewing needle and thread. Fold the fabric so that you’re only looking at the zipper tape on the right-hand side and the seam allowance under it.
  9. Using a zipper foot and a straight stitch with a length of 2.5 mm, sew the right side of the zipper tape to the seam allowance. You’ll need to put the zipper foot on its left side. Adjust your stitch width so that you’re sewing about ⅛” (3 mm) away from the zipper teeth. Backstitch at the beginning and end. You may need to move the zipper pull out of the way, which you can do by unpinning the top and pulling the zipper pull down.
  10. Remove the pins or basting stitches you placed in Step 8. Fold the zipper out so that you’re looking at the right side of the zipper.
  11. Switch the zipper foot to its right-hand side and select a straight stitch with a length of 2.5 or 3 mm. Edgestitch along the folded edge of fabric right next to the zipper teeth, about  ⅛” (3 mm) away from the folded edge.
  12. Flip the zipper back down so that the right side of the zipper is touching the seam allowance on the left side of the fabric. Turn your piece around so that you’re looking at the right side of the fabric.
  13. Using your preferred way of marking (jump to this section for details) create guidelines on the right side of your fabric for your topstitching. Make sure to transfer the marking for the bottom stop of the zipper to the face of the fabric so that you know where to pivot your stitching. 
  14. Using a zipper foot and a slightly longer stitch length of 3 or 3.5 mm, topstitch by following the guidelines you created. Start from the bottom, sew the short side, pivot 90 degrees at the corner, and continue sewing up until you reach the top edge. Backstitch at the beginning and the end.
    1. If you don’t want your topstitching to be so visible or if you’re worried about machine topstitching on a delicate fabric, you can also use a hand-sewn prick stitch for this step.
    2.  If you don’t want visible backstitching, you can also leave long thread tails at the beginning and end of your stitching, thread the long tails through a hand sewing needle and pull them to the back of your work to tie them in a triple knot and trim the excess.
  15. Remove the machine basting stitches you sewed in Step 4 that are holding your two pieces of fabric together. Give everything a final press and your lapped zipper is complete!

How to finish the top raw edge of a lapped zipper with a facing:

If you want to finish the top edge of your garment with a facing, you’ll need to sew your lapped zipper in a slightly different way. In this tutorial, I’ll walk you through the exact steps you need to follow to achieve a clean, faced finish around your lapped zipper in an easy way. We’ll start by sewing the facing pieces onto the fabric, and finish by inserting the zipper into the seam. For this tutorial, I’ll be sewing the zipper to the center back seam, but you can of course use this method for inserting a lapped zipper to the side seam. I’m using a contrasting zipper and thread color for visibility purposes, but you’ll want to go with a matching color for the best results.

Uses

  • Center back/front seams of tops, dresses, and jumpsuits with neckline facings.
  • Side seams of trousers and skirts with no waistband.

Supplies

  • Two pieces of fabric that will be joined by the zipper, with the center edges interfaced and finished.
  • Two facing pieces for the top edge of your fabric pieces. They should be interfaced and the bottom edges should be finished.
  • A regular zipper
  • Zipper foot
  • Standard presser foot
  • Sewing pins
  • Hand sewing needle
  • All-purpose polyester thread for permanent stitches
  • Sewing machine
  • Iron
  • A clear quilting ruler
  • Fabric marking tool of your choice, or washi tape

Step-by-step instructions:

  1. Start by trimming the center edges of your facing pieces by ½” (12 mm).
  2. On the center edges of your main fabric, snip two notches on the top edge that mark your seam allowance. Here I’m working with ¾” (19 mm) seam allowances.
  3. Place your zipper next to the center edges of your fabric. You want the top zipper stop to be about ¼” (6 mm) under the top seam allowance. So if you’re working with ⅜” (10 mm) seam allowance for the top edge, the top zipper stop should be ⅝” (16 mm) away from the top edge of your fabric. With the zipper in position, mark the location of the bottom zipper stop on your pieces of fabric.
  4. We will first work on the right-hand side of the fabric, where the underlap will be. Place the facing on the top edge of your fabric with the right sides touching. The top and the outer edge should be aligned, and there should be a ½” (12 mm) gap between the two layers on the center edge. Place a pin at the top, towards the right-hand side.
  5. Fold the center edge of your facing piece in with the wrong sides touching by ¼” (6 mm), so that its folded edge is aligned with the notch you made in Step 2. Temporarily pin it into place. Next, fold the center edge of the main fabric in with the right sides touching, about ⅛” (3 mm) in from the notch you made in Step 2. This fold should be resting on top of the folded edge of the facing. Remove the pin holding the fold of the facing and pin the new fold into place, making sure nothing shifts in the process. At this stage, when you look at the top edge you should see a ⅛” gap between the folded edges of the main fabric and the facing.
  6. Sew along the top edge, making sure to catch the folds you created in the previous step. You can use whichever seam allowance you prefer for this step – I’m using ⅜” (10 mm).
  7. Moving to the left side of the fabric, fold the center edge of the main fabric in with the right sides facing at the notch you made in Step 2 (right along the center seam allowance). For this side, we want the gap between the folded edges of the main fabric and the facing to be about ⅜” (10 mm), so fold the facing in with the wrong sides facing and slide it under the fold of the main fabric. The center edge of the facing will be sticking out from under the main fabric. Pin into place.
  8. Sew along the top edge, making sure to catch the folds you created in the previous step. Use the same seam allowance you used in Step 6.
  9. Trim, grade, and notch the seam allowances. Flip the facing pieces out and poke out the corners. Give everything a press to secure all the folds into place and neaten the corners. Temporarily fold them back out for easy access to the top edge in the next step.
  10. Place the two pieces of fabric with the right sides together and the center edges aligned. Starting from the bottom edge, sew up to the marking you made in Step 3 using a straight stitch with a length of 2.5 mm. At the mark, backstitch and then turn your stitch length up to its maximum setting (which should be around 4-6 mm). Continue sewing up the center edge using your predetermined seam allowance. You won’t be able to sew all the way to the top edge of the facings that you’ve already sewn, so just get as close as you can.
  11. Press the seam allowances open.
  12. Place your zipper face down onto the wrong side of the fabric. The zipper teeth should be centered on the center seam. 
  13. Pin the right side of the zipper tape (as you’re looking at it) to the seam allowance underneath it. The pins should be on the left side of the garment as worn, but because you’re looking at the wrong side of the garment you’ll be pinning the right-hand side of the zipper tape to the seam allowance on the right-hand side. If you prefer, you can also baste these layers together using a hand sewing needle and thread. Fold the fabric so that you’re only looking at the zipper tape on the right-hand side and the seam allowance under it.
  14. Using a zipper foot and a straight stitch with a length of 2.5 mm, sew the right side of the zipper tape to the seam allowance. You’ll need to put the zipper foot on its left side. Adjust your stitch width so that you’re sewing about ⅛” (3 mm) away from the zipper teeth. Backstitch at the beginning and end. Again, you won’t be able to sew all the way up to the top. Get as close as you can and leave the rest, you’ll catch this section in the next steps.
  15. Remove the pins or basting stitches you placed in Step 8. Fold the zipper out so that you’re looking at the right side of the zipper.
  16. On the back of the zipper, fold the top right edge of the zipper tape down diagonally, away from the zipper teeth. The wrong sides of the zipper tape should be touching. Pin or baste into place.
  17. Switch the zipper foot to its right-hand side and select a straight stitch with a length of 2.5 or 3 mm. Edgestitch along the folded edge of fabric right next to the zipper teeth, about  ⅛” (3 mm) away from the folded edge. With this stitch, try to catch the fold of the zipper tape you created in the previous step. You’ll also be able to secure the previously unstitched portion of the fabric to the zipper with this topstitching.
  18. Flip the zipper back down so that the right side of the zipper is touching the seam allowance on the left side of the fabric. Turn your piece around so that you’re looking at the right side of the fabric.
  19. Using your preferred way of marking (jump to this section for details) create guidelines on the right side of your fabric for your topstitching. Make sure to transfer the marking for the bottom stop of the zip to the face of the fabric so that you know where to pivot your stitching. The long edge of the guideline should be about ⅝” (16 mm) away from the center seam.
  20. On the back of the zipper, fold the top left edge of the zipper tape down diagonally, away from the zipper teeth. The wrong sides of the zipper tape should be touching. Pin or baste into place.
  21. Using a zipper foot and a slightly longer stitch length of 3 or 3.5 mm, topstitch by following the guidelines you created. Start from the bottom, sew the short side, pivot 90 degrees at the corner, and continue sewing up until you reach the top edge. Backstitch at the beginning and the end.
    1. If you don’t want your topstitching to be so visible or if you’re worried about machine topstitching on a delicate fabric, you can also use a hand-sewn prick stitch for this step.
    2.  If you don’t want visible backstitching, you can also leave long thread tails at the beginning and end of your stitching, thread the long tails through a hand sewing needle and pull them to the back of your work, and tie them in a triple knot and trim the excess.
  22. Fold the facing pieces towards the back of the fabric, with the wrong sides touching. The area around the zipper teeth should be cleared thanks to the folding we made in the earlier steps. Using a hand sewing needle and some all-purpose thread, slip-stitch the folded center edges of the facing to the seam allowance / zipper tape.
  23. Remove the machine basting stitches you sewed in Step 10 that are holding your two pieces of fabric together. Give everything a final press and your lapped zipper with a facing is all done!

Tips

  • Understitching the facing pieces after Steps 6 and 8 will encourage the facing to fold towards the wrong side of the fabric and prevent it from peeking out over the edge. To do so, fold the seam allowances towards the facing, and edgestitch to secure them together.
  • After Step 10, make sure the top edges of your main fabric are perfectly aligned and that one side isn’t higher than the other.
  • As there’s a ¼” (6 mm) gap between the top edge of your piece and the top zipper stop, you may want to sew a hook and eye at the very top to keep the two sides together.

Troubleshooting problems:

I’m having a hard time moving the zipper pull up and down on my finished lapped zipper.

This may be caused by stitching too close to the zipper teeth when you’re sewing the zipper to the underlap side. If the fabric you’re using is on the thicker side and there isn’t enough space between the zipper teeth and the stitching, the folded edge of the fabric may cause issues with pulling the zipper up and down. Try to stitch about ⅛” (3 mm) away from the zipper teeth, and adjust this measurement to be bigger if you’re working with a particularly thick fabric.

My topstitching looks wonky and curves around the zipper pull.

Make sure you completely push the zipper pull out of the way as you’re approaching it. You can simply push it to the opposite side using a stick or an awl, or move it up / down so that it’s completely out of the way. Using a zipper foot to do topstitching will also help in this area.

How to mark the stitching line around the zipper:

There are a few techniques you can use for marking the top stitching lines around the zipper. Here are 4 that you can choose from:

Use a marking tool like chalk or water-erasable markers:

Using a clear quilting ruler and the marking tool of your choice, draw a line parallel to the center seam on the left-hand side, about ⅝” (16mm) away from the center seam. You can use chalk, soap, water or heat erasable pens, or disappearing markers.

Use washi / masking tape:

If you don’t want to mark the right side of your fabric with any marking tools, you can also use a length of washi tape or masking tape in the right width. Simply stick the tape so that the right edge of the tape is touching the center seam, and sew along the left edge. Most washi tapes don’t have a very strong glue so it shouldn’t leave a residue on your fabric, but always test it on a scrap piece of fabric to make sure it won’t damage it.

If you can’t find tape in the correct width, you can also use any width of tape by sticking it to the outside of the guide rather than the inside. You’ll want to lay down your quilting ruler so that it’s sticking out by ⅝” (16 mm) away from the center seam, and stick the tape along the ruler. 

I find that most washi tape doesn’t stick too well to fabric, so you might need to readjust the position of the tape as you’re sewing.

Hand-basting:

You can also sew a line of hand-basting stitches that are neat and parallel to the center seam. If you choose this option, I’d recommend sewing them about ⅛” (3 mm) away from where your final topstitching will go so that you’re not sewing directly on top of the basting stitches. This will make them much easier to remove later on.

Quick Q&A’s:

What is a lapped zipper?

A lapped zipper is a way of sewing a regular zipper in a concealed way. With this technique, a folded flap of fabric covers the zipper and offers a mostly invisible finish.

What is the use of a lapped zipper?

Lapped zippers are often used on side or center back / front seams of tops, dresses, skirts, jumpsuits, and trousers. They create a concealed zipper look.

How much seam allowance do I need for a lapped zipper?

I recommend having at least ⅝” (16 mm) wide seam allowances, but you can also choose to work with larger seam allowances like ¾” (19 mm) or 1” (25 mm) for easier assembly.

What side should the lap of a lapped zipper be on when looking at it? 

Traditionally, the concealing flap of fabric should be on the left and the right side should be the underlap. This is so that right-handed people can comfortably access the zipper pull. If you’re sewing a lapped zipper of a center front or back seam and you’re left-handed, you can switch these directions so that the lap is on the right-hand side. If you’re inserting a lapped zipper to the side seam of a garment, the open edge of the lap should be facing the back of the body so that the garment looks cleaner and smoother from the front. (Fallon, 2017)

What is the difference between a lapped and centered zipper?

With a centered zipper, the zipper will be hidden under two flaps of fabric that meet at the center and there will be a U-shaped topstitching that holds everything in place. With a lapped zipper, one side of the fabric will form a flap that falls over the other side, concealing the zipper, and the topstitching will be L-shaped. A lapped zipper usually offers a cleaner and smoother finish than a centered zipper.

How do you sew a lapped zipper in a pillow / cushion?

Option 1: You can separate the back piece of the cushion into two, add seam allowance, and follow the steps outlined above to sew the lapped zipper at the center back of the cushion.

Option 2: You can sew the lapped zipper on the bottom seam or one of the side seams of the cushion. For this method, you’ll simply want to follow the tutorial above to sew the lapped zipper to your desired seam first, and then continue to sew the rest of the cushion.

What to read next:

This article was written by Nisan Aktürk and edited by Sara Maker.

Nisan Aktürk (author)
Nisan started her sewing journey in December 2019 and already has a fully handmade wardrobe. She’s made 50+ trousers, 20+ buttoned shirts, and a wide array of coats, jackets, t-shirts, and jeans. She’s currently studying for her Sociology Master’s degree and is writing a thesis about sewing. So she spends a lot of her time either sewing or thinking/writing about sewing! Read more…

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