How do I replace the elastic in a waistband?

Elastic perishes long before the garment does — it goes hard, splits into strands, or simply stops recovering. Replacing it takes half an hour and is the difference between a wearable garment and a bin bag. The only two things that go wrong are cutting it to the wrong length and letting it twist inside the casing.

What you'll need

• New elastic of the same width
• A safety pin, or a bodkin
• An unpicker
• A sewing machine or a needle and thread

Step by step

1. Find the opening in the casing.Many garments have a small gap left in the waistband seam from manufacture, often at the centre back. If there is one, use it. If not, unpick 3 to 4cm of the seam on the inside — no more.
2. Check whether the elastic is stitched down.Some waistbands have a line of stitching through the elastic at the side seams or all the way round to stop it rolling. Those stitches have to come out before anything will move.
3. Measure your replacement round the body first.Take the measurement over the clothing that will be worn under the garment, pull the elastic to a comfortable but firm tension, and cut about 5cm shorter than the relaxed measurement. Do not copy the length of the old elastic — it has stretched, and copying it reproduces the fault.
4. Match the width to the casing.Elastic narrower than the channel twists and rolls. Elastic wider than the channel will not feed through and buckles the waistband. Measure the channel, not the old elastic, which may have narrowed.
5. Pin the old elastic and pull it out.If you are reusing the channel, attach the new elastic to the end of the old one with a safety pin and pull the old one through — the new one follows and threads itself.
6. Secure the trailing end before you start feeding.A safety pin through the trailing end and into the fabric at the opening. Losing the end inside the casing means starting the whole job again.
7. Feed it through, gathering as you go.Work the safety pin along the channel in short pushes, sliding the fabric back over it. Keep checking that the elastic has not twisted at the point where it enters.
8. Check for twists before joining the ends.Pull both ends out, hold them together and run the flat of the elastic through your fingers all the way round. A twist left in makes the waistband sit wrong forever.
9. Overlap the ends and stitch them together.Overlap by 2 to 3cm and sew a rectangle with a cross through it, by machine or by hand. Butting the ends and whipping them together is weaker.
10. Try it on before closing the casing.It is a two-minute check that saves unpicking. Adjust the overlap if it is tight or loose.
11. Close the opening and distribute the gathers.Sew the casing shut, then pull the garment out to full stretch a few times to even the gathering all round.

Tips

• Woven elastic keeps its width when stretched and suits casings; knitted elastic narrows and suits being sewn directly to fabric.
• A bodkin is easier than a safety pin and does not catch the lining, but a safety pin works.
• If the waistband rolls over even with good elastic, stitch vertically through the casing at the side seams to hold it flat.

Common mistakes

• Cutting the new elastic the same length as the old — The old elastic is perished and permanently stretched, which is why you are replacing it. Copying its length reproduces a waistband that does not hold anything up.
• Letting go of the trailing end — It disappears into the casing and has to be fished back out, or the whole channel unpicked. Pin it to the fabric at the opening before you feed the other end in.

If it doesn't work

Questions people ask