Elastic works best when it's sewn directly into a seam or casing, not glued or topstitched loose
The strongest way to attach elastic is to sandwich it between two layers of fabric in a seam — the fabric holds it in place on both sides, and the thread locks it down. The most common method is a casing, where you fold fabric over the elastic and stitch through all three layers. A casing works for waistbands, necklines, and cuffs. The second method is to sew elastic directly into a seam before you close the garment, which is faster but requires more precision. Both methods keep the elastic from rolling, twisting, or peeling away after washing.
The elastic itself matters. Braided elastic (flat, woven on all sides) is easiest to work with and doesn't curl. Knit elastic (stretchy in all directions) is softer but can twist if you're not careful. Swimwear elastic is chlorine-resistant and thinner, for fitted garments. For most home sewing — waistbands, pajamas, underwear — braided elastic 1 to 2 inches wide is the standard choice.
Key Takeaways
- A casing (folded fabric sewn over elastic) is the most durable method and works for waistbands, necklines, and cuffs.
- Braided elastic is the easiest type to sew because it lies flat and doesn't roll or twist inside the casing.
- Measure the elastic to fit snugly around the body part, not loosely — it should stretch slightly when you put it on.
- Sew the elastic with a zigzag stitch or a stretch stitch, not a straight stitch, so the seam doesn't snap when the garment is worn.
- Pin the elastic at four points before sewing to keep it from bunching or twisting as you stitch.
How to make a casing for elastic
A casing is a tunnel of fabric that holds the elastic inside. Start by folding the fabric edge inward — usually 1 to 1.5 inches, depending on the width of your elastic. Press the fold flat with an iron so it stays in place. The fold should be wide enough that the elastic slides through easily with a little room to spare; if it's too tight, the elastic will bunch and the garment will pucker.
Pin the folded edge down all the way around, spacing pins 2 to 3 inches apart. Sew the fold closed with a straight stitch, staying as close to the inner fold as you can without sewing over the elastic opening. Leave a 2-inch gap in the stitching — this is where you'll thread the elastic through. Backstitch at the beginning and end of each seam so the thread doesn't unravel.
Cut a piece of elastic to the correct length. Measure it snug around the body part (waist, neck, or wrist) — it should stretch slightly when you put it on, not hang loose. Attach a safety pin to one end of the elastic and use it to thread the elastic through the casing, like threading a needle. Once the elastic is all the way through, overlap the two ends by 1 inch and sew them together with a zigzag stitch, going back and forth three times to make it strong. Then stitch the 2-inch gap in the casing closed.
Sewing elastic directly into a seam
This method is faster than a casing but requires you to hold the elastic steady as you sew. Cut the elastic to the correct length and pin it to the wrong side of the fabric (the side that won't show). The elastic should be stretched slightly as you pin — not at full stretch, but not loose either. Pin at the beginning, middle, and end, then add pins every 2 inches.
Set your machine to a zigzag stitch or a stretch stitch. A straight stitch will snap when the garment is worn because the thread can't flex with the elastic. Sew the elastic to the fabric with the elastic facing up, so you can see if it's bunching. Sew slowly and let the elastic guide the fabric — don't pull the fabric through the machine, or you'll stretch it unevenly.
Once the elastic is sewn down, fold the fabric over it and sew the seam closed with another zigzag stitch. The elastic is now sandwiched between two layers of fabric, which holds it in place and protects it from wear.
Measuring and cutting elastic to the right length
Elastic that's too long will bunch and wrinkle; elastic that's too short will pull the fabric and be uncomfortable. Measure the elastic around the body part it will hold — waist, neck, arm, or leg — and pull it snug but not tight. This is the length you need. Write it down before you cut, because you can't reuse elastic once it's been stretched and cut.
If you're making a garment for someone else, measure them directly if you can. If not, measure a similar garment that fits well — measure the waistband or neckline opening, then subtract 1 to 2 inches for the stretch. A waistband that measures 28 inches flat usually needs 26 to 27 inches of elastic.
Cut the elastic straight across with scissors or a rotary cutter. A jagged cut will fray and catch on the casing as you thread it through. If the elastic is very thick, you can seal the cut ends with a lighter held a few inches away — hold it there for a second until the edge melts slightly and fuses. Don't touch the melted edge; let it cool first.
Choosing the right stitch for elastic
A straight stitch is the default on most machines, but it's too rigid for elastic. When you wear the garment and the elastic stretches, the thread doesn't stretch with it — the seam breaks. A zigzag stitch has give built in; the thread moves side to side as the fabric moves, so it flexes without breaking. A stretch stitch (also called a lightning bolt stitch on some machines) is even better — it's designed specifically for elastic and knit fabrics.
Set your machine to a medium width (about 2 to 3 millimeters) and medium length (about 2 to 3 millimeters). Too wide and the stitch will look loose; too narrow and it won't flex enough. Test the stitch on a scrap of fabric with elastic before you sew the garment. If the seam pulls or puckers, widen the stitch slightly and try again.
Troubleshooting common elastic problems
If the elastic twists inside the casing, you pinned it unevenly or the casing is too loose. Prevent this by pinning at four points — top, bottom, and both sides — before you sew. If it's already twisted, you can sometimes untwist it by working it gently from outside the casing, but if that doesn't work, you may need to cut the casing open, untwist the elastic, and sew the casing closed again.
If the garment bunches or gathers unevenly, the elastic is too short or you stretched the fabric unevenly as you sewed. Measure the elastic again and compare it to the body measurement. If the elastic is the right length, the problem is usually that you pulled the fabric through the machine instead of letting the machine feed it. Sew slowly and keep your hands light.
If the elastic shows through the fabric or the casing is visible, the fold is too narrow or the fabric is too thin. For thin fabrics like cotton jersey or linen, use a wider casing (1.5 to 2 inches) and fold the raw edge under before you fold the casing, so you have four layers of fabric hiding the elastic.
Washing and caring for elastic seams
Elastic lasts longer if you wash it in cool water and dry it on low heat or hang it to dry. High heat breaks down the rubber or spandex inside the elastic, making it lose its stretch. If you're sewing a swimsuit or activewear, use swimwear elastic, which resists chlorine and salt water better than standard braided elastic.
If the elastic starts to lose its stretch after many washes, you can replace it without replacing the whole garment. Cut the casing open carefully with a seam ripper, pull out the old elastic, and thread new elastic through using the same method. Sew the casing closed again. This takes about 15 minutes and costs just a few dollars for new elastic.
Frequently Asked Questions
Can I sew elastic with a straight stitch?
You can, but the seam will break when the garment stretches because the thread doesn't flex. A zigzag or stretch stitch is much stronger and will last through many washes without splitting.
What if the elastic is too short and won't go all the way around?
You can overlap the ends by 1 to 2 inches and sew them together with a zigzag stitch, going back and forth several times. This creates a join that's almost as strong as the rest of the elastic. If the elastic is too short even with an overlap, you'll need to start over with a longer piece.
How do I keep the elastic from rolling up inside the casing?
Pin the elastic at four points — top, bottom, left, and right — before you sew the casing closed. This spreads the elastic evenly and keeps it from bunching or twisting. If you're using a very stretchy elastic, add extra pins every 2 inches.
Can I use elastic on a curved seam like an armhole?
Yes, but you need to stretch the elastic slightly as you sew so it follows the curve without bunching. Pin it at the top and bottom of the curve first, then add pins every 2 inches, stretching gently as you go. A zigzag stitch is essential for curved seams because it flexes with the curve.
What's the difference between braided and knit elastic?
Braided elastic is woven on all sides and lies flat, making it easier to sew and less likely to twist. Knit elastic is softer and stretches in all directions, which is better for fitted garments, but it can roll or curl if you're not careful. For most home sewing, braided elastic is the easier choice.