Here is a tutorial to make a waistband which has openings for the elastics.
I’m not sure what to call this type of waistbands. It has openings even after you finish it so if you need you can change elastics (in case your elastic has gone slack) or you can adjust the lengths. You can see elastics inside of elastic casings even after finishing the garments, like the photo above (this is my shorts blogged here).
I’ve sewn up some shorts and skirts since I started sewing in 2012, I haven’t met PDF patterns using this type of waistband other than Imagine Gnats’ Alder Skirt. In Japan, this type of waistband is pretty much popular mostly in kids’ clothes and most Japanese sewing patterns use this method.
Anyway, let’s get to do it.
1. Cut a waistband.
The length of the waistband should be x2 of actual waist size. The width should be 6cm this time, to put three 1/4″ (6mm) elasttics.
2. Hold in half lengthwise and right sides together. Stitch the narrow side of the waistband.
(a) is a half length of the short side of the waistband. (b) is the seam allowance. You need to keep the space between them unsewn ’cause it will be the elastic opening. Backstitch at the beginning and the end.
3. Open up the seam you sewed at step.2.
You see the opening on the lower half of that seam, right?
4. Fold your waistband half widthwise wrong sides together. Press.
5. Stitch two lines pararell to row edges of the waistband.
In my version, one line is 1.5cm (5/8″) away from folded edge and another line is 3cm(1 1/4″) away from folded edge. You can adjust them with the width of your waistband and the elastics.
6. Match the row edges of the waistband and the waistline of your shorts (or skirt), right sides together. Make your shorts wrong side out and put the waistband inside. Match the elastic opening seam with the back seam opening shown (then it will be inside of the waistband). Pin and sew.
Finish the seam. Then you will have this clean look.
7. Put the elastics from the opening. (I put my waistband wrong way so it had openings outside :() I used the elastic threader here but you can do with the safety pins.
I don’t think this is so hard and it will make your garment more adjustable. Actually, after making the bloomers for T, I tried it on and cut elastics a few inches (that bloomers have same openings).