Sewing with Knit Fabrics: Tips to Avoid Stretch Distortion

The sun's out, T-shirt weather is here, and honestly, I'm contemplating making swim trunks for the entire family… but first, let's talk about sewing with knit fabrics. If you're dreaming up breezy tees or form-hugging swimwear for an active summer, you're squarely in the right spot. Nothing beats the comfort and flexibility of knits once you get the hang of them—and the range of colors and options out there is downright inspiring (did I mention the 30+ jersey shades you'll find in the Sewing Studio shop?!).

But if you've ever ended up with wavy hems or necklines that look like they survived a toddler's tug-of-war, you know sewing knits is a little different from taming stable cottons or linens. The good news: armed with a handful of proven tricks, you can avoid stretch distortion and achieve crisp, professional-looking results. Ready to jump into knit garments that hold their shape as well as your love for DIY fashion? Let's get started.

Why Knits Are Everywhere (and Can Be Tricky)

Knits are the fabric of choice for anything from T-shirts and tank tops to swimsuits and yoga wear. Why? Their magical looped construction delivers comfort, flexibility, and drape you just can't get from wovens. That stretch is both a blessing and a challenge—a little like the friend who means well but occasionally gets you into trouble.

If you don't prep and handle knits with a bit of know-how, your seams might ripple, hems could flare, and neckbands…well, let's just say they might never forgive you. So before you grab that electric blue jersey (or the mermaid-green swim spandex you definitely need for beach days), here's what you need to know.

1. Choose the Right Knit for the Project

Not all knit fabrics are made for the same adventures. Get to know your knits before you commit:

• Jersey Knits: These are the rockstars for T-shirts—soft, lightweight, and stretchy but not too wild when handled. With over 30 colors in stock, you could have a tee for every day of summer (and every mood, if you ask me).

• Interlock & Double Knit (like Ponte di Roma): Thicker, more stable, and less likely to roll at the edges—fantastic for newbie knit sewists. Ponte is my "training wheels" recommendation for those just starting out.

• Swimwear Knit (Spandex or Lycra blends): Slick, ultra-stretchy, and built to handle pool parties and cannonballs. Requires careful handling, but the results are unbeatable for swim and activewear.

Pro tip: Always check whether your pattern calls for 2-way or 4-way stretch. A pattern for leggings or swim bottoms will require plenty of vertical and horizontal stretch—unless, of course, you aren't planning to actually move.

2. Prepping Knit Fabrics: Essential Steps

Pre washing

Sure, it feels like a drag to wait an extra day, but knits (especially cotton-based ones) are notorious for shrinking. Toss your fabric in the wash using the same settings you'll use for the finished garment. This is also your chance to discover any sneaky dyes that like to run.

Laying Out and Cutting

Knits can twist, wiggle, and curl at the edges as if auditioning for America's Got Talent. These tricks will help you keep your cool:

• Cut flat—preferably single layer: This prevents shifting and ensures sizing precision.

• Pattern weights over pins, or ballpoint pins: Stick to the seam allowance, or better yet, use pattern weights to avoid stretching. Multiple colors of washi tape also work in a pinch—crafty and cute!

• Rotary cutter and mat: Clean edges, minimal shifting.

• Watch the grain: Knits have a "direction of greatest stretch" (DOGS). Make sure it aligns with the body—across the hips for tees, around the bust for swimwear.

3. Needle and Thread Know-How

Not all needles are created equal, especially for knits. A sharp, universal needle can punch holes in knits, causing runs (it's not denim—your machine doesn't need to show off its uppercut).

• Ballpoint or Jersey Needles: These slip between the fabric's loops, protecting stretch fibers.

• Stretch Needles: Best for super-stretchy fabrics like swimwear or ITY jersey.

• Needle Size: Use lighter needles (size 70/10 or 75/11) for light jerseys, heavier (90/14) for double knits.

For thread:

• Polyester or Wooly Nylon: Poly has a little stretch, while wooly nylon (used in the bobbin or upper looper of a serger) delivers extra softness and recovery. Never use cotton with swimwear—it'll sag faster than a deflated beach ball.

4. Set Up Your Machine for Success

The Right Stitch

• Zigzag or Lightning Bolt Stretch Stitch: These flex along with your fabric, unlike the straight stitch that'll just snap under pressure (wouldn't you?).

• Try a width of 1.5–2.5mm and a length of 2–3mm as a starting point, but always test on a scrap first.

• Twin Needle: Looks super professional for hems—like store-bought T-shirts—but still stretches.

Lower Presser Foot Pressure

Your machine may have a dial, knob, or digital setting for this. Too much pressure = stretched seams and "lettuced" edges. A gentle touch goes a long way.

Use a Walking Foot

Grab a walking foot if you have one—it feeds both layers evenly, which prevents that mystifying wavy effect and makes sewing knits about as stress-free as an afternoon by the pool.

5. Stabilizing Where It Matters

Some parts of a garment—especially shoulder seams and areas around zippers, necklines, or swimwear elastic—need a little structure.

Here's how to reinforce them:

• Clear Elastic: Lightweight, flexible, and practically invisible in finished seams.

• Knit Stay Tape: Adds support but preserves stretch.

• Knit Interfacing: Ideal for swimwear waistbands or button plackets.

I always stabilize shoulder seams in a tee or tank top, and anywhere a closure might pull or stretch under strain. Your future self will thank you.

6. Handling and Sewing Without Stretching Out

• Let the Machine Do the Work: Don't pull, tug, or "help" the fabric through—this just invites distortion.

• Test Everything on a Scrap: Needle, thread, stitch length, and presser foot pressure. Give your sample a good stretch and see how it returns.

• Baste Before Committing: Baste your neckbands or tricky curves by hand or with a long machine stitch. Adjust as needed, then stitch permanently.

• Hemming Aid: Wonder Tape or wash-away hem tape holds edges in place before sewing without gumming up your needle.

For extra points, press with a steam iron (but gently) after sewing each seam. This sets stitches and helps eliminate subtle ripples.

7. The Swimwear & Activewear Difference

Swimwear and performance knits up the stakes: these fabrics pack a lot of spandex and demand special care for ultimate bounce-back and support. Here's what I do when swim season rolls in:

• Use swim-appropriate elastic (not regular woven or clear elastic).

• Always use a stretch needle with swim blends.

• Wooly nylon thread in the bobbin or serger looper: Keeps seams supple, especially around the legs and armholes.

• Stabilize all seams joining elastic to fabric—this ensures your swimsuit keeps looking good after every lap.

If you want a custom swimsuit that actually stays put at the pool (no wardrobe malfunctions, thank you), get comfortable with stabilizing methods and take it slow as you sew elastic in.

8. Troubleshooting: Don't Panic!

Everyone gets a wavy seam, a puckered hem, or a popped stitch at some point—and, yes, I still have my first wonky knit tee to prove it.

Here are common issues and quick fixes:

• Wavy Seams: Lower presser foot pressure, use a walking foot, and stabilize trouble spots.

• Skipped Stitches: Switch needles (ballpoint or stretch), check threading, use good quality thread.

• Puckered Fabric: Check tension, move to a slightly wider stitch, or try a stabilizer.

• Rolled Edges: Spray starch or gentle pressing helps, or baste with wash-away tape before sewing.

Make This the Summer of Knits!

With the right supplies, setup, and a few expert moves, sewing with knit fabrics can be just as rewarding (and addictive) as binging the latest sewing vlogs with a cup of iced coffee. Whether you want to rock a rainbow wardrobe of jersey T-shirts, sew a dreamy, custom swimsuit, or whip up activewear in your favorite shade, now's the time.

Here's your challenge: pick a color from our 30+ jersey collection or try a swim knit for your next project. Test these techniques, add a walking foot if you haven't already, and share how it all turns out.

You can create unique, beautifully-fitted garments that'll make you want to yell "I made this!" every time you get dressed. And if you run into trouble? You're not alone—every rippled seam is just part of your sewing story.

Ready to make the best tees, tanks, or swimwear you've ever owned? Grab those knits and get started. Your sewing adventure just got stretchier, comfier, and way more colorful.