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How to Sew A Bias Tape Casing


A casing is basically a fabric tunnel that holds elastic, boning or a drawstring. It’s created by either two lines of stitching or by a fold and a line of stitching. When the elastic or drawstring is pulled tight, the garment gathers in to fit the curves of the body. A drawstring or belt allows the opening to be tightened or loosened to fit the wearer; elastic allows the garment to stretch and move with the body.

Casings can be extensions of the pattern piece. For example, you can thread elastic through the sleeve hem to create a gathered cuff. Casings can also be created by sewing a separate piece to the garment, in the case of a waistband on a pair of drawstring pants. You can also make casings by sewing bias tape (page link) to the back of a piece and leaving the ends open for inserting elastic or cord.

Casing with elastic on Saltspring Dress

Casing with elastic on Saltspring Dress

Casing with drawstring and elastic on Tofino Pants

Casing with drawstring and elastic on Tofino Pants


You’ll see casings on casual and athletic wear, sleepwear and lingerie. It’s a great technique to use when you want to draw in fullness on a garment but want it to be adjustable or have stretch. Waistbands can be sewn with a casing, with elastic or with a drawstring inserted to hold up the pants. Casings are used on the hems of sleeves, blouses, pullovers and sweatshirts or around necklines, hoods and waistlines. Casings are cut longer than the desired length so the elastic or drawstring can gather it in and so the garment can stretch as needed. Whenever sewing a casing, leave an opening to insert the elastic or cord. Do this by leaving the ends open if the piece is flat or by leaving an opening if you sew the casing around a circular opening, like a waistline. For drawstrings and tie belts, sew buttonholes (page link) on the right side of the garment to create an opening for the drawstring ends to come out.

Tips + Notes

  • For the most flexible and adjustable casing opening, consider adding both a drawstring and elastic. You can either thread both elastic and drawstring through the casing or sew fabric tie ends to a piece of elastic so the elastic is hidden in the casing and the tie ends are visible.
  • There are plenty of tools to help you thread drawstrings and elastic through casings. Plastic threading tools, bodkins and loop turners can make the process easier and faster.


How to sew an extended casing (1)

On the edge, turn under the seam allowance twice and press. Or finish the edge and press under once. Edgestitch (page link) or topstitch (page link) to form the casing. The casing should be slightly wider than your elastic—a good amount to add is 1⁄8″–¼” (3mm–6mm).

How to sew an extended casing (2)

If the ends of the piece are open, proceed with threading the elastic through. If the casing is in a circle, leave an opening of about 4″ (10.2cm) for threading the elastic. Thread elastic through the casing by pinning a safety pin to one end. Use your hands to work the safety pin through and to make sure the elastic hasn’t twisted in the channel.

How to sew an extended casing (3)

Edgestitch or topstitch the opening shut. Start and end in line with your previous stitching, if the casing is in a round opening. If the casing is in a flat piece, baste across the ends of the elastic to keep it in its casing.


To add a separate casing to a garment edge, measure the opening and cut a straight piece to that length and to two times the width plus seam allowances. Pin one edge of the casing strip to the garment opening and sew. Turn under the seam allowance on the other edge of the casing strip, and line up the fold with the seam. Edgestitch (page link) along the fold. If the casing is in a circle, leave an opening of about 4″ (10.2cm) to insert the elastic or drawstring.

Separate casing

Separate casing


Place the bias tape (page link) along the wrong side of your fabric piece, and pin or baste (page link) in place. Edgestitch (page link) along the top and bottom of the bias tape, leaving an opening if the piece is applied in a circle. In this example, I’m using ½”-wide (1.3cm) bias tape to fit ¼” (6mm) elastic.

Bias tape casing

Bias tape casing

Source : The Sewtionary An A to Z Guide to 101 Sewing Techniques + Definitions
About the Author : Tasia ST. Germaine