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Swimsuit Sew-Along: Altering for Style

This post is one part of a Swimsuit Sew-Along series! If you missed the previous posts and would like to join in, just click below!

If you would like to add bra cups, raise a neckline or add/change straps, then this post is for you. I will cover some of the most common style changes I have encountered and will set you up with some great tutorial links for all the how to’s.

Adding bra cupsSometimes you find a great suit style but really want some inner support. And by all means! We’re making a suit so you want to take advantage of the opportunity to make it what you want! The best tutorial I’ve seen for this is not a swimsuit tutorial, but it works exactly the same. This Tutorial: How to sew a built-in bra (with cups!) has been cruising around pinterest for a while and it’s applicable to us because she makes a t-shirt with a built in bra sewn into a lining layer. This is exactly how a swimsuit is structured. Every women’s suit will have a lined front, even if only in the bust area, so you can just follow her tutorial for adding bra cups and presto-change-o you’ve got a great feature in your custom sewn swimsuit.

Altering leg hole/brief styleI had a question from one of our sew-along participants asking how to alter a brief bottom to be more of a boy-short style. After a little google research, I found this FREE pattern download & instructions at Cloth Habit. You could use this to alter a one piece suit too, by laying the boy-short pattern under some tissue paper. Line up your swimsuit pattern to match the crotch seam, for example (or however it lines up on your particular swimsuit pattern), tape the your swimsuit pattern to the tissue and draw the new leg hole. This pattern has a center seam, so to account for that in your suit (unless your swimsuit also has a center seam), draw the stitching line on the boy shorts pattern and line that up as best you can with the “cut on fold” line on your swimsuit pattern. This will ensure your boy short doesn’t turn out too wide.

neckline suitAdding neckline coverage: Another style alteration you might want to make involves gaining more coverage in the neckline. For a swimsuit with a halter neckline like the one pictured to the left, you could save scraps or buy a small piece of contrasting fabric to sew in place that would act as a camisole. After constructing your swimsuit, hem the top of the scrap (to be the top of your insert), try on your swimsuit and place it where desired between the straps/bust. Pin it in place and sew down the neckline on both sides using a straight stretch stitch, twin needle or a very narrow zig zag. Other styles with a scoop or v-neck can easily be drawn higher by starting at the shoulder seam, marking the height on the center front and mimicking the line of the original pattern down to the new neck height marking. Remember, you can always take away later, but it’s definitely more challenging (or near impossible depending on the situation) to add more.

Changing the Strap/Adding Straps:  After making a few halter neckline suits and a few strapless, I’ve come to realize I just feel more comfortable in a regular ol’ over the shoulder down the back strap. While criss-cross, halters using ties or bra hooks, and strapless can all be cute and flattering, I’m just not comfortable in the long run, so I’ve learned to stick with my tried & true. Adding straps to a halter is by far the easiest addition you can make. For my last swimsuit, I just took a long strip of my fabric, folded it in half right sides together and sewed all the way down. I used a turning tool to turn it inside out, attached them to the back of my suit where it seemed right and then tried it on, pinning the straps in front where I felt they worked best. Another way to make a strap is by encasing your elastic in this strip of fabric like this. This is probably what I should have done with mine, so if for some reason mine start to fail, I can always go back and do it right.

If however, you have a halter as shown above, you may have to do some legwork. Since this type of halter is designed and cut to wrap around your neck, the easiest fix is to cut the straps long and cross them in the back before sewing them in place on the back of your bodice.  Any halter with spaghetti straps, intended to be tied can be done the same way and even possibly made into the regular ol’ over the shoulder down the back strap. Just try it on and have someone pin your straps various ways to see what works best.

Did I miss your specific alteration? Let me know what you’re facing – I’d love to help you out! While some of these alterations are done before cutting/sewing, some won’t be finalized until we are in the process, so be sure to tuck this post away for safe keeping if you will need to alter as you sew. Now we are ready to cut out our swimsuit so grab your pins and a yardstick, ruler or quilting ruler and I’ll see you Friday!

11 thoughts on “Swimsuit Sew-Along: Altering for Style

  1. I really need to take my one piece in a size up top. the bottom fits great but the top is too big. How would I alter that? What kind of thread/stitch should I use?

    1. Hi Lisa – thanks for stopping by! Depending on the style, you can just take in the side seams starting at the top and gradually sew out to the original seam line at the waist (or wherever the fit starts to be right on you. You should use a stretch or ballpoint needle, polyester thread and a stretch straight stitch on your machine (it looks like a tiny zigzag) or just use a very narrow zigzag stitch. Hope that helps!

  2. I have a question about altering the crotch, Should I measure the width of someones crotch? I’m having issue that bottoms for my daughter have way too much fabric between her legs and it bunches up real bad, I’m afraid of taking too much out and her lady parts might show. I didn’t alter a bottom and on the beach this week sand got between her leg and the elastic and rubbed her raw. I was thinking if it fit better she wouldn’t have had this problem.

    1. Hi Michelle! Thanks for stopping by! I would compare the suit to a pair of their underwear. You could line them up and cut the suit to their size (plus seam allowance) and it should fit much better.

  3. I have a one piece swimsuit that looks like a 2 piece tankini set. It has control fabric from the bodice to where the “bottoms” begin. I bought it so the top fits (sz 14), but I wear a sz 10 in the bottoms. I wore it in the pool last summer but the wet fabric was very clingy to my lady parts because of the excess fabric. I ended up purchasing shorts to wear over the suit in the pool. How can I alter the bottoms so they will fit?

    1. Hi Laura, Thanks for stopping by! It would depend on where they were big. You could take in the side seams using a narrow zig zag stitch or serger if you have one, and just taper up to the seam allowance on the part of the suit that fits you. If you need to pull them up a little, it sounds like you could take a little on the waistline seam where the bottoms meet the control fabric. Without seeing it, I’d say you just will need to put it on and play with tucking out fabric in different spots until you get the fit you want. If you feel confident, you could remove the leg elastic for a cleaner alteration or just literally stitch up the side seam making sure the bottom matches up well. Wish I were right by you to give you better advice! Hope that helps some.

  4. I’d love to know how to alter a bottom on the swimsuit. I’m scared to touch it because of the fabric. It’s for a 7 year old. The bottoms are loose. The smaller size just was to tight. She’s got curves! The difference I need to take up I’d very small. So I’m thinking I’m going to have to rip out the seams in order to do both sides for the best look and fit. Do I need a specific thread, foot on my machine, needle, stitching, ect. I can’t see paying someone to fix them due to the cheap cost of the suit. I’m concerned about the needle putting large holes in the suit and the thread not staying put. We swim almost every day and I machine wash suits after each use. Air dry. Thanks!

    1. Hi there! You can just use polyester thread and your regular presser foot. The stitches and needles I discuss here: But I’d be happy to answer any additional questions if anything else comes up. Thanks for stopping by!

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