Spandex needs a different approach than cotton or linen

Spandex stretches in all directions, which means standard sewing techniques will pucker the fabric, break your thread, or snap the seams when you wear the garment. The fabric also slips under the presser foot and curls at the edges. You cannot sew spandex the way you sew a t-shirt.

The core difference is that spandex requires a stretch stitch instead of a straight stitch, a ballpoint or stretch needle instead of a universal needle, and thread that gives rather than locks. You also need to stabilize the fabric so it does not feed unevenly. Most home machines can do this. The setup takes ten minutes.

Key Takeaways

  • Use a ballpoint or stretch needle (size 75/11 or 90/14) and polyester or nylon thread, both of which stretch without breaking.
  • Set your machine to a narrow zigzag or a dedicated stretch stitch, never a straight stitch, because straight stitches snap when the fabric moves.
  • Stabilize the seam with a strip of tear-away stabilizer or a rolled hem foot to prevent puckering and slipping.
  • Reduce presser foot pressure and use a walking foot if your machine has one, so the fabric feeds evenly without bunching.
  • Test your settings on a scrap of the same spandex before cutting into your project.

Choose the right needle and thread

A ballpoint needle has a rounded tip that slides between fibers instead of piercing them, which prevents laddering (vertical runs in the fabric). A stretch needle has a special scarf and eye designed to handle elastic materials. Either one works; many sewers use them interchangeably for spandex. Buy size 75/11 for lightweight spandex or 90/14 for thicker blends.

Universal needles will work in a pinch, but they pierce the fibers and leave holes that can ladder when you stretch the garment. Avoid them if you have ballpoint or stretch needles on hand.

Thread matters as much as the needle. Polyester thread and nylon thread both stretch and recover without snapping. Cotton thread is rigid and will break the moment you move in the finished garment. Gutermann, Coats, and Mettler all make polyester and nylon thread in standard colors. Match the thread color to your fabric, not the bobbin color.

Set your machine to a stretch stitch

A straight stitch locks the thread in place and cannot move. When you stretch spandex, the thread snaps. A narrow zigzag stitch (width 1.5 to 2, length 2 to 2.5) allows the thread to move with the fabric. The thread zigzags slightly instead of running straight, which gives it slack to absorb the stretch.

Many machines have a dedicated stretch stitch or elastic stitch in the stitch menu — usually marked with a wavy line or labeled "stretch". Check your manual to find it. If your machine has one, use it instead of the zigzag. It is designed specifically for this purpose.

Test your stitch on a scrap of the same spandex before sewing the actual seam. Sew a line, then pull the fabric hard in both directions. If the thread snaps or the seam puckers, adjust the stitch width or length slightly and try again. Once you find the setting that works, write it down for next time.

Stabilize the seam to prevent puckering

Spandex curls and bunches under the presser foot because it is so stretchy. A strip of tear-away stabilizer placed under the seam prevents this. Tear-away stabilizer is a thin, stiff fabric that you pin or baste under the seam line, then tear away after sewing. It costs a few dollars per roll and lasts through many projects.

Cut a strip of stabilizer about one inch wide and the length of your seam. Pin it to the wrong side of the fabric, directly under where your needle will go. Sew through both the fabric and the stabilizer. After sewing, gently tear the stabilizer away from the seam. It should come off cleanly without damaging the thread.

If you do not have stabilizer, a rolled hem foot (also called a narrow hem foot) can do the same job by guiding the fabric evenly under the needle. Not all machines have this foot, but if yours does, it is worth trying. The foot holds the fabric in place so it feeds smoothly without bunching.

Reduce presser foot pressure and use a walking foot if available

The presser foot holds the fabric down while the needle moves. On spandex, too much pressure flattens and stretches the fabric unevenly, causing puckering. Most machines have a dial or lever to adjust presser foot pressure. Turn it down to the lowest setting that still holds the fabric in place — usually around 3 or 4 on a scale of 1 to 10.

A walking foot (also called an even-feed foot) moves the fabric forward at the same speed as the feed dogs underneath, so both layers feed evenly. This is especially useful for spandex blends or when sewing two layers of spandex together. If your machine came with a walking foot, attach it before sewing. If not, they are inexpensive to buy separately and fit most machines.

Sew slowly and keep seams straight

Spandex is forgiving of tension problems but unforgiving of crooked seams. Sew at a slow to medium speed — around 50 to 60 percent of your machine's top speed. This gives you time to guide the fabric and catch mistakes before they become a problem.

Use a seam guide or mark your seam line with a water-soluble pen before sewing. Spandex does not hold a crease, so you cannot fold and press a line the way you would with cotton. A marked line or a guide keeps your seam straight and even.

Do not pull the fabric toward or away from the needle. Let the feed dogs move it. Pulling stretches the fabric and causes uneven stitches. Your hands should guide, not force.

Finish seams to prevent curling

Spandex edges curl and fray because the fibers are so elastic. A zigzag stitch along the raw edge seals it and prevents curling. After sewing your main seam, trim the seam allowance to about half an inch, then zigzag along both raw edges. This takes an extra five minutes but makes the garment last longer and look neater.

Alternatively, you can use a serger (overlock machine) to finish the seam in one pass. A serger cuts the excess fabric and wraps thread around the edge in a single motion. If you have access to a serger, it is the fastest and cleanest way to finish spandex seams. If not, the zigzag method works just as well.

Frequently Asked Questions

Can I use a regular needle on spandex?

A universal needle will work for one or two seams, but it pierces the fibers and leaves holes that ladder when you stretch the garment. Ballpoint and stretch needles are inexpensive and designed for this job. Buy a pack and keep them on hand.

What if my seams still pucker after I switch to a stretch stitch?

Puckering usually means the presser foot pressure is too high or the stabilizer is not in place. Lower the pressure dial and add a strip of tear-away stabilizer under the seam. If puckering continues, try a slightly wider zigzag (width 2 to 2.5) or a dedicated stretch stitch if your machine has one.

Do I need a serger to sew spandex?

No. A home sewing machine with a stretch stitch and a ballpoint needle will sew spandex seams that hold up to wear. A serger finishes the edges faster and looks more professional, but it is not required. Many sewers finish spandex seams with a zigzag stitch on a regular machine.

Why does my thread keep breaking?

Cotton thread breaks on spandex because it does not stretch. Switch to polyester or nylon thread, both of which move with the fabric. Also check that your needle is a ballpoint or stretch needle, not a universal needle, and that your stitch is a zigzag or stretch stitch, not a straight stitch.

Can I wash spandex seams the same way as cotton seams?

Yes, but use cold water and gentle detergent to extend the life of the spandex. Chlorine bleach and hot water break down the elastic fibers over time. Air dry when possible, or use low heat in the dryer. Seams sewn with polyester or nylon thread hold up well to repeated washing.