Full seat adjustments

Today I will show you an easy and practical pattern correction to increase the back crotch length. This correction is essential as a trouser that drops a lot at the back can be very annoying and unaesthetic. As a matter of fact, this is the most frequent problem I have noticed on people, including myself. Let's put an end to this!

Tools

• A back trousers or shorts pattern
• A ruler
• A pen or pencil
• Some paper sheers
• A sheet of paper
• Some clear tape or glue
• A seam gauge or quilter's ruler

Method

Step 1:

Prepare your back pattern and highlight the seam lines. Then trace an horizontal line at hips level and a vertical line from the lower part of the crotch. Note that I'm using a short pattern, so I will end the line at the hem. If you are working with a trouser, end this line at about 15cm (6") below the crotch, then square a line across the leg.

Step 2:

Slash through the pattern along the hip line, but not through the side seam allowance. The side seam line/hips intersection will be used as a pivot to rotate the upper part of the pattern.

Step 3:

Create a "hinge" in the side seam allowance by notching through it twice, toward the pivot. Don't notch too close by the pivot or it will break the pattern in two.

 

Step 4:

Place a strip of paper below the slash line and rotate the upper part of the pattern to create an opening of about 12mm (1/2") in the crotch... this measurement will depend on the fullness!

Step 5:

Tape the paper strip to the pattern and reshape the back crotch seam line. The side seams might need to be reshaped as well.

Step 6:

Shorts: slash through the vertical line down to the hem line, create hinges in the hem allowance and rotate the inseam in the same manner as indicated previously, according to the same value. Avoid adding width to the back hem as it might affect the style!

Trousers: slash through the vertical line down to the other horizontal line. Then slash through this line, from the inseam to the vertical line. Place a paper strip below the pattern and slide the crotch/inseam corner away from the garment, according to the same value added previously. 

Step 7:

Tape the paper strip to the pattern and reshape any affected lines, such as the inseam, lower part of the crotch or hem line.

Trousers: measure the front and back inseam length and drop the back crotch/inseam corner to readjust its length according to the front panel.

Step 8 (optional):

If you wish to, retrace the pattern piece but do not discard the original piece. Readjust the grain line by extending it from the lower part of the pattern. 

If your pattern have a zipper opening at the back, ensure to preserve its length. This correction must not affect it so reposition any notches/markings indicating the end of the opening.