An elastic waistband is convenient for slipping a garment on and off easily. However, if the elastic is showing, the garment will look tacky and cheap. You can cover your elastic waistband for a more polished look using the same fabric that was used to make the garment, a complementary fabric or a decorative ribbon. The key to creating a professional-quality, covered elastic waistband is careful placement of the fabric and nice, even stitches.
Stretch the exposed waistband to its full length and measure it with a cloth measuring tape.
Cut your fabric or ribbon to the length of the measurement from step 1 plus 2 inches. The width of the fabric or ribbon should be twice the width of the elastic waistband plus 1/2 inch more. You need this width to cover the elastic and stitch the covering to the garment.
Place the elastic waistband covering on the garment, right sides together with one long raw edge of the covering lined up with the bottom of the elastic waistband. The elastic waistband should stick up above the covering fabric.
Pin the covering fabric in place 1/4 inch from the raw edge. You will need to stretch the elastic waistband as you pin. The covering fabric will bunch up when you aren't stretching the elastic. That is fine. When the whole elastic waistband covering is pinned in place, stretch the elastic again to be sure the covering isn't too loose or too tight in any one place. Fully stretched, the elastic waistband and the covering should be smooth and flat.
Machine stitch the fabric to the garment at the bottom of the elastic waistband, along the straight pins. Be careful not to catch the elastic in your stitches.
Fold under the other long edge of the elastic waistband covering 1/4 inch. Iron the fold.
Bring the folded and ironed edge of the fabric up and over the elastic waistband. Pin it in place. Remember to stretch the elastic waistband as you pin in order to make the covering perfectly aligned with the elastic waistband. Test your placement before you sew by pulling the elastic waistband to its full stretch.
Machine stitch the covering in place using the ironed fold as your guide. Again, be careful not to catch the elastic in your stitches. When you come to the end of the elastic waistband covering, make sure that the overlapping ends are evenly folded on both sides.
Trim all loose threads.
If you decide to use ribbon to cover the exposed elastic, buy a width that is double the width of your elastic plus an additional 1/2 inch.