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Drafting a good pattern requires knowledge of the fabric it will be made in. This is especially true when working with stretch materials like those used for swimwear and intimate apparel. The combination of fabric properties and the pattern shape create the finished garment's fit. Your design depends on getting this combination right. Below are eight tips and techniques that I use to draft well-fitting patterns for stretch materials.
1. Select Your Materials Ahead of Time
You can’t draft the pattern for the fabric properties unless you know what those properties are. Before starting your pattern, you’ll want to know which fabric you will use for the style and understand the nuances of its behavior. A wide variety of materials fall into the stretch fabric category, and they can yield quite different results in a garment.
Most of the time, when it comes to swimwear and intimates at least, stretch fabrics will mean knit fabrics. Knit fabrics are inherently stretchy regardless of their fiber content due to their construction. Woven fabrics can also be stretchy if they contain a stretch fiber like spandex or elastane. These stretch fibers can be used in woven and knit fabrics to add additional stretch to the fabric and compression that will return the fabric to its original shape after being stretched.
The direction of stretch is another important fabric property to note. Knit fabrics inherently stretch in width (cross-grain). In the length direction (straight grain), they can range from no stretch to lots of stretch depending on the type of knit and fiber content. Fabrics that stretch in width and length are called 4-way stretch fabrics. Woven fabrics, if they have a stretch fiber, usually stretch in the width direction. Warp stretch fabrics are an exception that stretch in length only.
The fabric type and the amount of stretch in each direction will inform how you draft your pattern to get the look and fit you desire. The fabric will also determine what seams and stitch types are appropriate, and, thus, what seam allowances should be included in your pattern.
2. Be Clear About the Intended Fit and Function
Fit can be subjective, and there is more than one way to use stretch fabrics in a garment. Before you start drafting your pattern, you want to be clear about the intended look and fit for the style. How fitted is the style supposed to be? Who is the target customer for this garment? What activities will they be doing while wearing this garment? The more specific you can be about the target customer, their fit preferences, and the use cases for the garment, the easier it will be to draft a pattern that meets these needs.
Stretch can serve several purposes in a garment. A little stretch can provide additional comfort and flexibility to an otherwise looser-fitting garment. In this case, the fit of the garment is not really reliant on the fabric stretch, and the pattern might look fairly similar to that of a non-stretch style. A lot of stretch can greatly shape the fit and conform to the body's curves in a tight-fitting garment. Lots of stretch can replace other contouring techniques like darts or contour seaming in a pattern. A clear vision for the design and fit will help you draft an appropriate pattern.
3. Understand Where the Garment and Wearer Need Support
It is important to understand what part of a garment provides support – especially in high-stretch and compression garments like swimwear and intimates. These types of garments are very functional and sit close to the skin – making fit and comfort vital. Your pattern will need to account for these areas of support and include adequate structure to uphold them for the garment’s lifespan.
For a bra, the underband supports the garment and the wearer. In a corset, the waist provides the structure for the rest of the garment. In a tank top, the straps will hold the weight of the garment. These areas of support will need the most attention to detail in your pattern to make the garment functional and comfortable to wear.
4. Identify the Relative Stretch of Different Garment Areas
Even if the whole garment is made of the same stretch material, not every part of the garment will stretch equally when worn. This is a key aspect of drafting patterns for stretch fabrics that I don’t see talked about very much. The areas of the garment that are the tightest-fitting and those that provide the most support will be stretched the most.
To illustrate this, think about a one-piece swimsuit. Let’s map how much stretch is being used in each area. The torso will be stretched a lot in width as it wraps around the body on all sides. The torso will also experience vertical stretch from the shoulder to the crotch - but not necessarily evenly. The center will be stretched more as it extends from the shoulder to the crotch while the side seam doesn’t have as much vertical pull on its top and bottom sides. The straps experience the vertical stretch from the shoulder through to the crotch, but they aren’t being stretched at all in the horizontal direction.
What does this unequal stretch mean for your pattern? It means the areas that experience the most stretch will be more “squished” on your pattern than those that experience less stretch. Another way to put this is that the areas with high stretch will have negative ease in the pattern, but those with low or no stretch might have zero or even positive ease. You can see why drafting for stretch materials isn’t as simple as creating a pattern and applying the same stretch factor to the whole thing.
5. Start From A Pattern Block
Drafting patterns for stretch fabrics isn’t easy, but certain shortcuts can make it much easier. One of my favorite shortcuts to drafting any pattern is to start with a tested pattern block. A pattern block is a similar style that you know fits and sells well. If you have one of these styles made for a similar fabric to the one you are drafting, you can use that pattern as a starting point. Using a tested pattern lets you know that the basic fit is good, and you just need to adjust the design details to match your new design.
It is crucial here to select a block pattern that is made for the same type of fabric as you are working with. Ideally, it might be the same exact fabric, but it is at least very close in weight and stretch properties. You wouldn’t want to use a stretch woven pattern as a block for a 4-way stretch knit style or vice versa. The goal is to build upon the fit you’ve already tested in this type of fabric.
6. Balance Fabric Stretch And Contour Seaming for the Best Fit
As I mentioned above, high-stretch materials can replace darts and contour seams to create shaping. There are times, though, when you want to use a combination of fabric stretch and other contouring techniques to create the design, fit, and support you want. Areas that need to closely fit the body's curves - like a bra cup - benefit from seams or darts. High-stretch materials can stretch around these curves but will squish and flatten the body tissue, adding more stress to the fabric.
Contour seams in the pattern not only make it easier to fit curves precisely, but they can also provide support. A seam or line of stitching through a stretch fabric will stabilize that area and prevent excess stretching. The stitching acts as reinforcement. For even more structure, you can add elastic to trim tape to the seam. This can be a great option for the areas in the garment that need extra support.
This is a functional and aesthetic conversation, so the designer and patternmaker will likely be involved in finding the right balance here. When discussing fabric stretch versus contour seaming, keep in mind how your design will fit on different body sizes and shapes. You might be able to rely on the fabric stretch alone in smaller or flat-chested sizes, but not in larger or fuller-bust sizes. You want to design and pattern with your whole size range in mind.
7. Don’t Forget About Shrinkage
When drafting for stretch materials, it is obvious to consider the stretch, but don’t forget to consider shrinkage as well. As with any fabric, you’ll want to test your stretch fabrics under normal care and wear conditions to anticipate any shrinkage. I recommend doing this right after you’ve selected your materials. You’ve dialed in your pattern to get the right fit so far, so it would be a shame to have that precision thrown off by the final garment shrinking in the first wash. (I had a bra once that came out of the wash with the shell fabric so shrunken that it was pulling the top edge of the bra cup outward in a way that was immediately noticeable through any shirt - super annoying.)
Beyond just washing shrinkage, stretch fabrics for swimwear and intimates are also exposed to chlorine, salt water, sunlight, sweat, etc. which can change the fabric properties and require adjustments to the pattern to compensate. Stretch fabrics can shrink depending on how they were unrolled and laid out to cut or if they come in contact with heat from printing or ironing during production. You can draft your pattern to counteract all these types of shrinkage if you’ve tested your fabric and have the information needed.
8. Include Trim Cut Length Guides
Some stretch fabric garments like tee shirts require minimal trims. Swimwear and intimate designs, on the other hand, often include multiple components like elastics, ribbons, stabilizers, hardware closures, rings, sliders, etc. Any of these that require cutting (i.e. not in piece units like a slider) should have a cut length guide in the pattern. These are not pattern pieces that will be cut in a marker from the fabric, but they are guides that make it easy to measure and cut how much of each trim is needed for each size.
It is especially important to include cut length guides for trims that will finish at a different length than the length of the pattern seam line. For example, when adding elastic to the leg openings of a panty, the elastic might be pulled during sewing to slightly ease the fabric into the seam. This means that the elastic length is shorter than the length of the leg opening on the pattern. You’ll need to specify the exact elastic length in the pattern cut guide to ensure every garment gets sewn the same way.
Stretch materials are wonderfully flexible and lend so many properties to the fit of the finished garment. They can be tricky to draft patterns for, though, if you’re not used to managing them. Follow these pattern drafting tips and techniques to get that perfect fit for your next swimwear or intimate apparel garment.
Meet Alison
Alison Hoenes is a freelance patternmaker who helps women’s slow fashion brands confidently get their designs to production without compromising fit, vision, or values. She writes a daily newsletter for fashion brands and designers on creating clothing and growing a fashion business that fits, and is the host of the How Fitting® podcast.