A full bum adjustment adds width and length to the hip area of the back skirt to accommodate a fuller booty. It's a great adjustment to know if you often find you need a little bit more room across your bum, but the skirt fits comfortably on your waist.
I'm demonstrating on the Ramona skirt pattern. You can also use this adjustment on any similar darted skirt pattern.
For this tutorial you’ll need a very quick toile of your skirt, a flexible tape measure, your back skirt pattern piece (trace this off so you're not chopping up your original pattern), a pen or pencil, a ruler, some scissors, some tape or a glue stick, and a bit of paper slightly bigger than your pattern piece.
So, once you’ve got those handy, let’s get started!
First things first, you'll need to calculate how much extra width and length to add to the pattern when making your full bum adjustment.
To do this, you'll need to make a quick toile of the skirt in the size that most closely matches your waist and hip measurements. You can combine waist and hip sizes if you need to - there are more details on how to do this in our dedicated blog post on how to combine sizes.
Your toile can be really rough and ready as it'll just be used for figuring out how much of an adjustment you need to make. You don't need to insert any zips or other fastenings - you can just pin the open side seam together, remembering to take account of the seam allowances.
To determine how much extra width you need to add, use a seam ripper to open your skirt toile at the side seam from just below your waist to just below the widest part of your hips. The side seam will open up - using a tape measure, measure how much it opens by. This is how much width you'll add to the pattern.
To determine how much extra length you need to add, measure how far the hem rides up at the centre back. This is how much length you'll add to the pattern.
Once you've got those numbers noted down, we can get started on the full bum adjustment proper.
First of all, mark the seam allowance at the corner where the waist seam meets the side seam.
Next draw a line from this corner to the tip of the dart - we'll call this 'line 1'.
Then draw another line from the tip of the dart to the centre back - this line needs to be perpendicular (i.e. at a right angle) to the grainline - we'll call this 'line 2'.
And finally, draw a line through the centre of the dart from the waist seam to the dart tip - we'll call this 'line 3'.
Now it's time to grab those scissors! Starting at the centre back, cut along line 2, and then pivot at the dart tip to cut along line 1 stopping just before the seam allowance corner you marked earlier.
From the other side of the seam allowance, cut from the corner of the pattern piece and stop just before the start of line 1 to create a hinge.
Cut along line 3, starting at the waist seam and leaving a small hinge at the dart tip.
You should now have two hinges - one at the tip of the dart and one at the side seam. They're delicate so be gentle with them!
Next, get a piece of paper slightly bigger than your back skirt pattern piece and draw two horizontal parallel lines on it, with the distance between them the amount you want to increase the length by.
The upper part of the skirt will now be overshooting the lower part at the centre back seam (this is shown by the green arrow above). The amount that it overshoots should be equal to the half the width you want to add to the pattern, since the back skirt pattern piece represents one half of the finished back skirt.
We're nearly done! Now you need to redraw the dart, using the original one as a guide. Then draw in your new centre back seam, connecting it to the hemline at the bottom of the piece. And finally smooth out the corner where the waist and side seams meet if this has been distorted. Remember to transfer any pleat markings, notches etc. to your newly drawn dart and centre back seam.
