How To Lengthen Or Shorten Trouser Patterns With A Twisted Seam

If you have a trouser pattern that contains a twisted seam (such as the Tidebrook Trousers, which I’ll be using in this tutorial), you may be wondering how to go about lengthening or shortening them.

If you’ve shortened or lengthened a trouser pattern before, then you’ll already know the basics.

For trousers with a twisted seam the process is basically the same, you just need to take care with how you draw the line of the new seam, which won’t be straight.

We’ll start by looking at how to lengthen the trouser pattern, and then move on to shortening them.

Lengthening Trouser Patterns With A Twisted Seam

Look for the lengthen/shorten line on the pattern. On the Tidebrook it’s midway between the notches on inside and outside leg seams.

Cut the pattern pieces along the lengthen/shorten line.

Move your two pieces of trouser pattern apart by the amount you wish to lengthen. In this instance I’ve chosen 4cm. Make sure the space is the same measurement right across the pattern pieces.

Ensure the grain line continues in a straight line from one piece to the next as shown above. Pin your pattern pieces to your fabric.

You’ll see that the inside leg seam is not a smooth curve. Use a curved ruler or draw the curve in free hand to create a new smooth line.

You can see I’ve used the widest point (A) to draw my curve from to avoid narrowing the leg and tapered the new chalk line into the crotch seam (B). The outer leg remains in line so can just be joined with a chalk line (C) - (D).

Make sure you have marked any notches then just cut out and construct as per the instructions.

Shortening Trouser Patterns With a Twisted Seam

To shorten the pattern, you need to cut along the shorten/lengthen line, just like the lengthening process.

This time I’m going to shorten my pattern by 4cm. To do this I’m going to drawn a line across the pattern piece, 4cm up from my cut line on the upper part of the trouser pattern.

You can see the line is parallel to the lengthen/shorten line that I cut across earlier.

Next I lay my lower trouser pattern piece along that line I’ve just drawn. Also matching the grain line as we did when lengthening in the previous section.

Pin the pattern pieces to the fabric and place a curved ruler to the widest point of inside leg seam, as in the lengthening instructions, and re draw your line joining the two pieces as shown in the picture above.

The outer leg line should naturally join well enough to just cut without any alterations, as you can see above.

As with lengthening, make sure you have marked any notches then just cut out and construct as per the instructions.

So that’s it. Really not that scary after all. Enjoy!

Sussex Seamstress is an independent pattern studio, based in Sussex, UK.

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