Earlier this year I had the great opportunity to make my own pair of jeans at the jeans school in Amsterdam where we were being taught by their teacher. I now drafted my own pattern from the Rundschau system, and with help from this teacher I altered it so that it's now a straight leg pattern, fit for use with selvedge denim.
I'm ready to start sewing, but I have some choices to make for seam allowances.
Since I'm using lapped seams, as per usual with jeans, the teacher told me to use double the seam allowance on pieces that fold under. For instance 1cm on the top of the back leg, vs 2 cm on the bottom of the yoke since the back leg folds over keeping it's length and the yoke folds under losing 1 cm. The same goes for the back inseam vs the front inseam where the back is folded under so needs double the seam allowance.
The other parth where I'm using a lapped seam is of course the seat seam between the two back legs. My point now is: If i double the seam allowance on my right back leg, which is folded under, the fold won't be the center. The left leg plus the foldes seam will be the same size as the right leg minus the folded seam (which is 1 cm wide). Is this how it's supposed to be, or is the entire 1 cm wide fold supposed to be the center, and should I add 1,5 cm to both left and right back legs so that the center falls exactly in the middle of the 1cm folded seam?
I hope I explained this clearly. I've added a little drawing: