Common repairs

Repair a Popped Seam on Stretch Fabric

Mend a seam that has burst open on a T-shirt, leggings or other knit. A machine with a stretch or narrow zigzag stitch is preferable. Hand sewing works for small splits if you leave the stitches loose.

Confident Beginner25 minHand or machine

What you will learn

Sewing a stretch seam
Choosing a knit needle
Keeping stitches elastic

Materials and tools

Polyester all-purpose thread (cotton thread breaks on stretch)
Machine ballpoint or jersey needle 70/10 or 80/12 (stretch needle 75/11 on spandex)
Hand sharps needle, size 8 or 9
Pins or clips
Seam ripper
Small scissors
Scrap of the same knit for testing

Before you start

Assess the damage. Stretch the seam gently. If the thread has snapped but the knit is not laddered or torn, this repair works.
Check the fabric on both sides of the split. If it is thin, holed or running, use rep-small-hole or rep-darn-knit.
Decide why it popped. A straight stitch has no give, so it breaks when the knit stretches. Other causes are a garment that is too tight or worn thread.
Test on a scrap of the same knit. Set a zigzag about 1.5 mm wide and 2.5 mm long and sew a short seam. Pull it. Stitches should stretch and spring back.

Step by step

Turn the garment inside out. Unpick 1/2 in (12 mm) of loose stitches past each end of the split. Cut away stray thread.
Smooth the seam flat. Do not press hard on a synthetic knit. Use a cool iron and a press cloth.
Pin the edges together, right sides facing, matching the original needle holes. Place pins across the seam, every 1 in (25 mm).
For machine: choose a narrow zigzag (width 1.5 mm, length 2.5 mm) or the stretch stitch in your manual. Stitch along the old line. Do not stretch the fabric while sewing, let the feed dogs pull it.
Overlap the existing sound stitching by 1/2 in (12 mm) at each end. Use two or three stitches in reverse to secure, as your manual describes.
For hand: use a doubled thread and backstitch, pulling each stitch only until it lies on the fabric. Leave a little slack so the seam can stretch.
Trim thread tails. Stretch the repaired seam gently over your hands to test it. If a stitch snaps or the seam puckers, unpick and resew a little looser.

Tips for a neat result

A new ballpoint needle makes a big difference. A dull or universal needle can cut knit loops and make holes.
Stitch a second row of narrow zigzag 1/8 in (3 mm) from the first on a seam under heavy stretch.
Wind the bobbin and thread the upper the same way as usual. If stitches skip, change to a stretch needle.

Common mistakes and fixes

Stitches pop again when the garment is pulled on.

You used straight stitch. Resew with a zigzag or a stretch stitch.

The seam looks wavy.

You stretched the knit while sewing. Let the machine feed the fabric, and hold it gently from behind.

Small holes appear along the stitching.

The needle is too thick or not ballpoint. Use a new 70/10 ballpoint needle.

Safety and fabric care

Keep fingers clear of the needle. Unplug the machine before changing needles.

Check your result

The seam stretches and springs back with no snapped thread.
No holes or puckers along the line.
Garment pulls on and off easily.

Stop it happening againChoose polyester thread and a stretch stitch for any knit seam. Avoid wearing garments that fit too tightly across the seam.

When to use a professionalTake it to a repair shop for swimwear, compression garments or technical fabrics where the fabric or flatlock seam needs special machines.

Projects that use this

Fix a Split SeamBeginner20 min