How To Let Out (Or Take In) The Back Trouser Seam For Men's Trousers

Men's trousers are constructed so that there is a wide seam allowance in the center back seam.  This is to allow for alterations.  Have the client try on the trousers.  If they are too big, pinch the waist excess in the back and mark how much they need to be brought in.  If it needs to be more than 3", they need a smaller size trouser.  Taking in trousers more than 3" will distort the fit in the back of the trousers.



If the trousers are too tight, have the client undo the fastener and unzip the zipper a few inches.  Then measure from both sides of the closure.  This will determine the amount needed to let out at the waist.  Look at the seam allowance to see how much you can actually let out.  I try to leave in a 3/8" seam allowance.  You should be able to let out at least 2".

Look to see if there is a belt loop on the center back seam.  This will need to be removed.  As you unpick it, look at the way it has been stitched and attached so that you can duplicate it when you sew it back on.

If you need to let it out 2", you will mark your new line 1" out from the original stitching line.  Draw your new stitching line, blending the new line to the original seam line where the seam curves into the crotch.

Pin and stitch, from the bottom to the waist.

Unpick original seam.

Press seam flat to press out old crease and embed new stitches into the fabric. 



Then press seam open and use wood clapper to reduce bulk and train new seam allowance.



Press waistband open to reduce bulk.

Roll down waistband and press again, and use the clapper again.

When pressing on the right side of the trousers, use a pressing cloth to protect the fabric from shine.  My favorite pressing cloth is a silk organza cloth, hemmed with a serger narrow rolled hem.

On the outside of the center back waistband, stitch in the ditch to anchor waistband down.

Stitch on the belt loop.  This belt loop has been stitched first at the bottom, then the loop has been flipped up and topstitched at the top of the belt loop.

Great job!  This is a great skill to know.

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