I have a short torso, so when I make pants that are the correct crotch length, I don’t have enough room for a fly zipper that opens wide enough. Any suggestions?
Karen Howland replies: To look natural and aesthetically pleasing, pants fly zipper should end at, or before, the point where the center front seam begins to curve toward the inseam. But apart from its visual impact, the primary purpose of any waist zipper is to increase the waistline length so the wearer can pull on the garment over the hips. If a zipper is the only source of the extra length at the waist, when closed it needs to be at least half as long as the difference between the hips and the waist, including a couple of inches of added ease. For example, I have a 13- to 14-inch difference between my hips and waist, regardless of my current weight. Therefore, I need my pants and skirt waistbands to increase by 15 to 16 inches in order to comfortably and easily pull them on. A 9-inch zipper (which opens to about 18 inches) easily provides that amount, and works well for me…but I’m over 6 feet tall.
The difference between waist and hip size provides the key
Measure to find the difference between your waist and hips to determine how much total extra length you need, then measure the straight portion of the center front seamline on a pants pattern that’s adjusted to your waist-to-hip length to see how much extra length you can get from the existing opening. If you need more zipper length than your torso length will allow, you need to add one or more additional sources of extra waistline length to your pants. There are several ways to do this.
Add elastic or another zippered opening
To supplement your too-short fly, you could add elastic to the waistband in the back of the pants. The drawings at left show how to redraw the pants back pattern to provide more waist length for an elastic waistband, and how to add the necessary length to the waistband pattern. Another option is to put a second, invisible or hidden zipper somewhere else in the pants, giving the garment two waistband openings. If you need only a couple more inches for the length, a third option would be to convert the fly opening to a nonfunctioning mock fly and simply put all the needed extra length into an invisible or hidden zipper that’s long enough. In either of these last two options, the best places for an unseen zipper are the center back seam, a side seam, or inside a side seam pocket.
The drawings below show one way to conceal a zipper opening in a side seam pocket, along with how to alter your waistband to accommodate the new opening. If you prefer one of the hidden zipper solutions not depicted here, you can adapt these waistband directions to position the appropriate opening and overlap.
Add waist length with an elasticized back
An elasticized back waistband is easy to incorporate, though somewhat visible.
1. Increase the back pattern waistline
Tape the back pattern onto a piece of tissue paper. Decide how much (total) you need to add to the waistline. Divide this amount in half and then subtract the width of the back dart(s). Add the resulting amount to the back pattern waistline, dividing equally at each end. Redraw the center back and side seams as shown. (Omit the darts when you sew.)
2. Extend your waistband pattern to incorporate the new length
Cut your waistband pattern apart on the center backline. On a piece of paper, draw a line that’s twice the length of the altered back waistline; mark the midpoint CB and the ends SS. Lay the two waistband pattern sections over the line, aligning the SS marks; tape in place. Draw lines between the sections to complete the pattern.
Add waist length with a zipper hidden in a pocket
The following directions will work with any side seam pocket that has either an on-seam or slanted opening and whose top edge is attached in the waistband seam. Pockets with horizontal openings, such as on jeans, won’t work because most of the inner pocket layer, on which the zipper is inserted, is exposed.
Insert the zipper in the inner pocket layer
Prepare the opening
Draw a vertical line on the right side of the inner pocket layer and reinforce it with stitches, as shown, to establish an opening that will expose the zipper teeth. Slash along the line, clipping out to the reinforced corners.
Sew in the zipper
Fold and press the slash edges to the wrong side along the reinforcing stitches and up to the top edge. Center this opening over the zipper, then topstitch close to the fold to secure it. Proceed with the pants and pocket construction until you’re ready to attach the waistband, then draft a new band as shown next.
Revise the waistband pattern to open at the pocket and at the front
Mark alignment points on the pattern
Mark the existing waistband pattern to show the center fronts, side seams, side pocket openings, and zipper position, as well as the overlap and underlap allowances.
Create two patterns
Trace the pattern to make one pattern for the center front-to-pocket opening section and another for the zipper opening-to-center front section; include overlap and underlap allowances at the ends.
Sew each band to the corresponding waistline section
Open the fly zipper and the pocket zipper. Baste the top of the front section of the open pocket (all layers) to the front of the pants. Cut out the waistbands from the new patterns. Pin each band piece to the corresponding pants section, aligning all the marks. Complete each band in the usual manner.