10 tips for sewing knits perfectly

When a person learns to sew, the first projects are always with woven fabric. When you go to a fabric shop, you’ll notice that most fabrics are woven. And when you browse sewing projects on Pinterest, nearly all of them use woven fabric.

But take a look at your own wardrobe, or that of your kids. I’m willing to bet that you have a pretty high percentage of garments made with knit fabric. (Such as T-shirts, leggings, sweatshirts/pants and sweaters.) So why do DIY sewing projects focus mostly on wovens?

Simply put, wovens are a whole lot easier to work with (except for some fussy fabrics like chiffon, which tend to cause much swearing). However, knits have a LOT of advantages that woven fabric doesn’t, which is why they’re so frequently used in clothing.

But in order to understand all this, let’s talk a moment about the difference between woven and knit fabric, and then we’ll get to 10 life-saving tips for sewing knits easily and with wonderful results!

Wovens vs. Knits

The first thing to understand is that woven and knit fabrics are NOT interchangable! When you are following a sewing tutorial or pattern, pay close attention to the type of fabric called for. Wovens and knits are intrinsically different and have totally different characteristics.

Look at the image above (thank you to One Little Minute for the great graphic!). Woven fabrics are created with a weaving loom, with a warp and a weft, or in layman’s terms, vertical and horizontal threads that overlap each other. Knit fabrics, on the other hand, are created with a single thread that is looped around itself over and over again, just like the fabric that is created on knitting needles. The picture below shows the right and wrong sides of a woven cotton (red) and a knit cotton (green).

This difference in construction method makes for a lot of other differences. The most important is that knit fabric stretches while woven fabric doesn’t. (Unless the fabric has been woven with some percentage of stretch thread, which is how stretch jeans have that extra bit of stretchiness that regular jeans don’t.)

Because knits are by stretchy by nature, garment patterns using knits usually have what is called negative ease. This means that the finished garment is actually smaller than your body’s measurements. This is because knits are meant to hug the body to a varying degree, and it will stretch over the body for a perfect fit. This also means that garments made with knit material are more forgiving in terms of sizing.

Knits also tend to be more pliable than wovens. This means that they drape easily and are very soft. There are different weights of knits, from relatively lightweight to thicker sweatshirt knit, however there are not as many types and weights of knit fabric as there are woven fabric.

However, there are different types of knit material, too. The two most typically used are jersey and interlock. In the photo above, the striped fabric is jersey and the yellow fabric is interlock.

Jersey, what the classic T-shirt is made of, is basically a classic stockinette stitch, which has a very distinct front and back, unlike woven and interlock fabrics. Notice that the edges roll in towards the front of the material, just like they do with a classic knit sweater. It’s hard to see well because knit fabric has tiny stitches, but see how similar the stitches and edges of jersey fabric are to those of my Gemini sweater, which I finished knitting a couple of months ago but never got around to blocking, hence the rolled edges.

Interlock is a double knit, which basically means that there are two layers of knit material. This means that the front and back are the same and the edges don’t roll in, as you can see a couple of pictures above.

Knit fabric is made in all different fibers, whether natural fibers or synthetic ones. It frequently has a small percentage of lycra or spandex (which are actually the same thing) to make it even more stretchy, which is great for neckbands and other parts that need to expand a lot.

If you’ve ever knit a hat or sweater, you’ll know that ribbing is usually worked around the openings, not only to keep the fabric from rolling, but also to make it stretchier to fit around the body part. (You can see ribbing worked on the arm cuffs of the sweater two pictures up.) Likewise, there is also fabric ribbing that is super stretchy and frequently used for cuffs and neckbands.

The picture above shows some different types of knit fabrics:

1. solid colored cotton jersey
2. printed cotton jersey
3. interlock
4. ribbing
5. hemp jersey
6. synthetic viscose knit
7. hemp sweatshirt fleece

Due to the structure and stretchiness of knit material, it can be a little tricky to sew. It can stretch out of shape. The seams can easily get wavy. The thread can snap. Holes can form in it. Your final garment may end up too big or too small.

However, there are some tricks to get past these potential problems and the payoffs of a well-sewn knit garment are well worth figuring out how to sew this type of material! So, on that note, let me tell you my “10 U’s,” otherwise known as…

10 Tips for Sewing Knits Perfectly

1. Understand stretch.

Before you even start your project, you need to understand your chosen fabric. Not all knit material stretches in the same way. It depends on the way it’s been made, the fiber content, and quality. It can be two-way stretch (it stretches just horizontally or just vertically), or four-way stretch (it stretches both horizontally and vertically).

The very important thing to remember is that the direction of greatest stretch must go AROUND the body part so that it can open wide enough to fit over but still be snug around the body. If you accidentally position a leggings pattern, for example, so that the stretch goes up and down, the garment will stretch out lengthwise, becoming too long, and will most likely be very tight around the hips and legs.

If the garment you are sewing is relatively snug, a fabric’s percentage of stretch and recovery is very important. So let’s say you have a fabric that is nice and stretchy, but with little recovery, meaning that it gets stretched out without going back to its original width. If you are sewing a loose T-shirt, it probably won’t be a problem. However, if you sew leggings with it, you will end up with a garment that is too long and wide because it doesn’t pull back into shape after getting stretched over the legs and hips.

The best thing to do to avoid this problem is to calculate stretch and recovery with a ruler or gauge. This excellent article by Elegance and Elephants has a downloadable stretch gauge with very detailed instructions and photos explaining how to use it properly. Quality sewing patterns will indicate what percentage of stretch is necessary for the project, so make sure that your chosen fabric is at least that stretchy, if not more.

2. Use the right pins.

Before you start sewing, you’ll probably need to pin your fabric pieces together. But not all pins are made the same. Regular straight pins are quite sharp to pierce the fabric. Ballpoint pins have a softer point which slips between the knit loops without of going through the thread itself. This keeps the fibers intact so that they don’t break when the fabric is stretched. Because heck, who wants little holes in their meticulously sewn garment?!

An alternative are Wonder Clips. These are special plastic clips that hold the fabric together without pinning. These are very useful if you don’t want to damage fabric with pins, however you can only use them on the edge of fabric, not anywhere in the center of the sewing surface.

I use these ballpoint pins* and these wonder clips* and am very happy with both.

3. Use the right needle.

The same exact thing goes for sewing needles. Regular universal needles are quite pointy and will ruin the knit fabric. Make sure you get either ballpoint or stretch needles. Another really amazing needle for knits is the double needle (or twin needle). I’ll talk more about that in tip #5.

The needles in this picture are Schmetz 90/14 Stretch Needle* and Schmetz 4/75 Stretch Twin Needle*.

4. Use the right thread.

Thread doesn’t stretch as much as stretchy fabric, which means that it can easily snap. And that’s really annoying. This is why I only use polyester thread with knits. Some people seem to be able to use high quality cotton thread for stretchy garments, but I’ve had too many stitches on stretchy garments break with it. Some people use wooly nylon or stretch thread, but I haven’t used them myself.

There are lots of brands of polyester thread, but I almost always use Gutermann Sew-All poly thread* because it’s the easiest-to-find high quality polyester thread where I live in Europe.

5. Use the right stitch.

Remember what I just said about thread snapping when a knit garment is stretched? The most important way to avoid this happening is to use a stitch that will expand with the fabric. Which means that a classic straight stitch is out of the question.

Your sewing machine probably has a variety of stitches and is sure to have at least one that will work with knits. The most common is the zig zag stitch (#5 above), but there are also the triple straight stitch (#3 above, which looks like three vertical dashed lines), the stretch stitch (#4 above, which looks like a jagged lightning bolt), and the triple zig zag stitch (#6 above, which looks like a dashed zig zag stitch). Always test these stitches out on a scrap of the fabric you’re using so that you can regulate stitch width and length, as well as tension.

Another option is to use a long straight stitch with a ballpoint or stretch twin needle*. I love using this needle for hems and at some point I’ll make a tutorial to show how to use it. Basically there are two top threads, and the bobbin thread zig zags between them under the fabric, allowing it to stretch. The resulting parallel lines of stitching also looks more professional than a simple zig zag.

And yet another option? An overlock machine (serger)! This sewing machine’s stitches are stretchy by nature, so perfect for knits.

6. Understand knit edges.

The wonderful news is that knits don’t fray, so you don’t have to finish off the edges if you don’t want. Remember, though, that the fabric edges of jersey roll to the front. This can be a desired effect, as on the front edge of this rectangle vest, because it hides imperfectly cut edges and just looks more finished. However, it can also be really annoying if you just want it to lie flat, such as when you’re sewing it. If this is the case, apply some iron-on stabilizer to the back of the fabric, or spray-on starch before sewing it.

7. Use the feed dogs properly.

The feed dogs are those jaggedy metal things sticking out of the needle plate on your sewing machine. They move front to back each time the needle goes up to move the fabric along. (Learn more about sewing machine anatomy here.) Sometimes it helps to pull the fabric a little from behind to move it along. DO NOT pull knit fabric because you will then sew it into place while it’s all stretched out.

One problem people frequently run into is that the fabric gets sucked down into the feed dogs when you start sewing it from the very edge. To avoid this from happening, start sewing a centimeter or so in from the edge, backstitch to the edge, and then continue sewing regularly.

8. Use a walking foot.

One common issue when sewing knits is that the seams pucker up and look wavy after sewing them. These last three tips help deal with this effect. The first and, in my opinion, easiest way to counteract seam waviness is to sew knit fabric with a walking foot. Like I explained in my walking foot lesson, this special foot has feed dogs on the top, too, meaning that it moves bulky, slippery or otherwise difficult fabrics under the sewing needle evenly.

9. Use tissue paper.

This is a trick that I’ve already shared in my lesson on sewing PUL and other laminated fabrics. While putting tissue paper between the fabric and the machine foot was useful in counteracting the stickiness of the laminated PUL surface, in the case of knits it works as a stabilizer. You can also try putting the tissue paper under the fabric too, which helps keep the fabric from getting pulled down into the feed dogs (see tip #7). The sewing needle creates a perforation, making the paper easy to remove afterwards.

10. Use your iron.

I have never tried to hide the fact that I hate ironing, but it’s absolutely necessary to press fabric and seams when sewing. And when sewing knits, an iron can be your best friend because a good steam pressing will flatten out most wavy seams. The picture above shows normal zig zag horizontal and vertical stitching on scraps of 4-way stretch jersey with the edges folded over. I left the stitches marked A unironed, and gave the B stitches a quick steam pressing. It’s hard to tell in the picture, but the A stitches are quite wavy, while the B stitches are perfectly flat but equally stretchy.

So, now that you know all about what makes knit fabric special and how to compensate for the problems arising from its stretchiness, grab some scraps and practice sewing knits a bit. When you feel comfortable sewing this type of fabric, move on to this refashion tutorial for a comfortable and useful accessory!

This lesson on sewing knits is part of the syllabus of Cucicucicoo’s Learn to Machine Sew beginner’s sewing course! Don’t forget to share pictures of your work on Facebook or the Cucicucicoo Creations Flickr Group!

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