How do I fix a seam that has split open?

A split seam is the easiest clothing repair there is, and the one most often botched. Almost every failure comes from the same two things: sewing on top of the seam instead of in it, and starting exactly where the old stitching stopped, which puts all the load on the one weak point you just created.

What you'll need

• Thread matching the garment
• A sharp needle, or a sewing machine
• Pins
• An iron (optional)

Step by step

1. Check it is the seam and not the fabric.Pull the two sides gently apart. If the thread has broken and the fabric edges are intact, it is a seam and it will repair well. If the fabric itself has torn beside the stitching, or the edges are frayed to nothing, restitching there will simply tear again a few millimetres further along and it needs a patch behind it instead.
2. Turn the garment inside out.Everything happens on the wrong side. The old seam allowance and the crease it left are your guide line, and you cannot see either from the outside.
3. Pull the loose thread ends back and knot or trim them.A trailing end will unravel further while you work. On a machine-overlocked seam, tie the ends off rather than cutting them flush.
4. Match the two layers along the original crease.The pressed line where the seam used to sit is the correct position. Pin across the seam every 3 to 4cm so the pins can be pulled out as you reach them.
5. Start well inside the sound stitching.Begin about 2cm before the break, in stitching that is still holding, and finish 2cm past the other end. Overlapping is the entire point — it transfers the load into the old seam rather than concentrating it at a new endpoint.
6. Sew along the same line, not beside it.Follow the original stitch holes as closely as you can. Sewing a new line 5mm inside the old one takes width out of the garment on that side and makes it hang oddly.
7. Use backstitch if you are sewing by hand.Running stitch is not strong enough for a structural seam. Backstitch produces an unbroken line on the surface and is the nearest hand equivalent to machine stitching.
8. Secure both ends properly.On a machine, reverse three or four stitches at each end. By hand, work two or three stitches back over themselves and finish inside the seam allowance where the knot cannot be felt.
9. Press the seam.Open first, then to one side as it was originally. Pressing is what makes a repair look like the garment rather than like a repair.

Tips

• Crotch and underarm seams take real load. Sew those twice, one line 2mm inside the other.
• If the original seam was overlocked and the overlocking has survived, leave it — you only need to replace the straight stitching.
• Polyester thread on almost everything. Cotton thread is weaker and rots faster in a wash.

Common mistakes

• Starting and stopping exactly at the ends of the split — The two junctions become the weakest points in the seam and it opens again from there within a few wears. Overlap 2cm into stitching that is still holding at each end.
• Sewing the split closed from the outside — It puts a visible line of stitching on the right side of the garment and it usually catches only part of the seam allowance, so it is both ugly and weak.

If it doesn't work

Questions people ask