Spandex requires a different needle, thread, and tension than cotton or linen

Spandex stretches in all directions, which means your machine will fight it unless you change three things before you start: use a ballpoint or stretch needle (size 75/11 or 90/14), switch to polyester or nylon thread instead of cotton, and lower your presser foot pressure so the fabric feeds without bunching. The fabric itself does not need special treatment—you can cut and mark it the same way—but the machine settings do.

The most common mistake is using a regular sharp needle. A sharp needle pierces woven fabric cleanly, but spandex is a knit, and a sharp needle will skip stitches or split the yarn. A ballpoint needle has a rounded tip that slides between the fibers instead of piercing them. A stretch needle is even better: it has a special scarf (the indent behind the needle eye) that prevents the fabric from bouncing back and causing skipped stitches.

Polyester and nylon thread have more give than cotton. Cotton thread is inelastic, so when you stretch a seam sewn with cotton, the thread breaks. Polyester and nylon stretch with the fabric, which is why they are the standard for swimwear and activewear.

Key Takeaways

  • Use a ballpoint or stretch needle in size 75/11 or 90/14, never a regular sharp needle, because spandex is a knit and sharp needles skip stitches in knits.
  • Thread your machine with polyester or nylon thread, not cotton, because cotton thread breaks when the finished garment stretches.
  • Lower your presser foot pressure to 2 or 3 (or use a walking foot) so the fabric feeds evenly without puckering or bunching.
  • Use a narrow, flexible stitch like a narrow zigzag or a stretch stitch, not a straight stitch, so the seam can move with the fabric.
  • Serge or bind your seams if your machine has a serger, because raw edges on spandex will curl and fray faster than on woven fabric.

Adjust presser foot pressure and stitch type before cutting

Presser foot pressure controls how hard the feed dogs push the fabric through the machine. On most machines, the dial is on top of the presser foot assembly and ranges from 0 (no pressure) to 9 (maximum). Spandex needs pressure around 2 or 3 so the fabric moves smoothly without the presser foot crushing it into wrinkles. If your machine does not have a pressure dial, a walking foot (also called an even-feed foot) solves the same problem by moving the fabric from above as well as below.

Straight stitches do not stretch. When you wash and wear a garment, the seam stays rigid while the fabric around it moves, and the thread eventually breaks or the fabric tears. Use a narrow zigzag stitch (width 1.5 to 2, length 2 to 2.5) or a stretch stitch if your machine has one. A narrow zigzag looks almost like a straight stitch but has enough flex to move with the fabric. Test the stitch on a scrap of your spandex first—the goal is a stitch that looks straight but has a tiny side-to-side motion.

Seam allowances on spandex should be narrow: 3/8 inch or less. Wider seams add bulk and are more likely to curl or pucker. Mark your seam line with a fabric pen or tailor's chalk before you sew, because pencil marks do not show on dark spandex and pins leave holes.

Prevent puckering by using the right presser foot and stabilizer

Puckering happens when the presser foot or feed dogs stretch the fabric unevenly as it moves through the machine. You have already lowered the presser foot pressure, but two other tools help: a walking foot (which feeds from above and below at the same rate) and a tear-away stabilizer placed under the fabric.

A walking foot is worth buying if you sew spandex regularly. It costs $20 to $40 and fits most machines. If you do not have one, a tear-away stabilizer under the seam does much of the same job. Cut a strip of tear-away stabilizer (available at any fabric store) about 1 inch wide and place it under the fabric as you sew. The stabilizer keeps the fabric from stretching ahead of the needle. After you finish the seam, tear away the stabilizer—it comes off cleanly and leaves no residue.

Do not use a regular presser foot if you can avoid it. The standard foot has a wide, flat sole that can catch and stretch the fabric. A narrow foot (sometimes called a 1/4-inch foot) or a walking foot is much better.

Serge or bind raw edges to prevent curling and fraying

Spandex curls at the edges more aggressively than woven fabric. A raw edge will roll inward and fray within a few washes. If you have a serger, use it: a 3-thread or 4-thread serge finishes the edge and seals it in one pass. If you do not have a serger, bind the edge with bias tape or a narrow strip of fabric folded and sewn over the raw edge.

Binding takes longer than serging but works well. Cut a strip of fabric (cotton or spandex) about 1 inch wide, fold it in half lengthwise, and press it. Place the folded strip over the raw edge so the fold is on top and the raw edges of the strip are underneath. Sew through all layers with a narrow zigzag stitch. Fold the binding to the back and sew it down from the back side with another narrow zigzag. The result is a finished edge that will not curl or fray.

If you are making a straightforward project and do not want to serge or bind, at minimum finish the raw edges with a narrow zigzag stitch on your regular machine. It is not as durable as serging or binding, but it slows down the curling and fraying.

Cut and lay out spandex the same way as other knits

Spandex does not require special cutting or layout. Lay it out single layer (not folded) so you can see the direction of the stretch. Most spandex has more stretch in one direction (usually the width) than the other. If your pattern calls for a certain direction of stretch, follow it—the pattern designer tested the fit with that direction in mind.

Use sharp fabric scissors or a rotary cutter and ruler. Spandex is slippery, so a rotary cutter is often easier than scissors because you can hold the ruler firmly while you cut. Pin the pattern pieces to the fabric with ballpoint pins (which do not leave large holes) or use pattern weights instead of pins. Mark seam lines and notches with a fabric pen or tailor's chalk, not a pencil.

Wash your hands before cutting and sewing. Spandex shows fingerprints and oils, and they can leave marks that are hard to remove later.

Sew seams slowly and test on scraps first

Sew at a medium speed, not fast. Spandex is forgiving, but rushing increases the chance of skipped stitches or puckering. If your machine has a speed control, set it to 50 to 70 percent of maximum. Let the feed dogs do the work—do not pull or push the fabric.

Before you sew your project, cut a 4-inch by 4-inch scrap of your spandex and sew a test seam with your chosen needle, thread, stitch, and presser foot settings. Stretch the test seam by hand. The thread should not break and the stitch should not skip. If either happens, adjust the needle size, thread type, or stitch settings and test again. This takes five minutes and saves you from ripping out seams on your finished project.

If you do need to rip out a seam, use a seam ripper to cut every third or fourth stitch, then pull the thread out. Do not try to pull the whole thread at once—you will stretch the fabric. After you remove the stitches, the holes may be visible, so sew the new seam 1/4 inch away from the old one if possible.

Frequently Asked Questions

Can I use a regular needle if I sew slowly?

No. A regular sharp needle skips stitches in spandex because spandex is a knit, not a woven. The needle pierces the yarn instead of sliding between the fibers, and the yarn bounces back and misses the loop. Slowing down does not fix this. A ballpoint or stretch needle is required.

What if my thread keeps breaking?

You are likely using cotton thread. Switch to polyester or nylon thread. If you are already using polyester or nylon, check that your needle is not bent or dull (replace it), and make sure your presser foot pressure is not too high (lower it to 2 or 3). Also check that your thread is wound tightly on the spool—loose thread can break under tension.

Do I need to pre-wash spandex before sewing?

Most spandex does not shrink, but check the bolt end or ask the fabric store. If the fabric is new and stiff, you can wash and dry it once to soften it, but this is optional. If you do wash it, use cool water and lay it flat to dry—heat and the dryer can damage spandex.

Can I use a serger instead of binding the edges?

Yes, a serger is the fastest way to finish edges on spandex. A 3-thread or 4-thread serge seals the edge and prevents curling and fraying. If you do not have a serger, binding or a narrow zigzag stitch on your regular machine works well.

What stitch should I use for hems?

Use a narrow zigzag or a stretch stitch, not a straight stitch. A straight stitch will break when the hem stretches. Fold the hem up 1/2 inch, press it lightly (do not use high heat), and sew with your chosen stitch. A twin needle (two needles side by side) also works well for hems on spandex and creates a professional look.