This is a wonderfully retro adaptation to both versions of the Iris Pattern, and is very easy to do.
You will need to extend the centre back of the back pattern piece so it can overlap to do up the buttons. This is called the button extension. And how much you need to add on depends on how big the buttons are that you want to use. A rough guide is to go for an extension of about 1.5 – 2cm. In this example I’ve used a 2cm extension as the buttons I want to use are about 2cm in diameter.
Altering your pattern
Draw in the centre back line on the back pattern piece. Add a piece of paper wider than your button extension and stick that to the centre back seam allowance. I use proper pattern cutting paper with the dots and crosses on. It makes it so much easier to get nice straight lines and right angles. You can order yours by the metre online.
Personally I prefer to use Prittstick instead of tape, as it won’t melt onto your iron, but feel free to use whatever method of attachment you desire.
When the buttons are sewn onto the back of your top and done up, you need to have the buttons sitting down the centre back line. So place your button on the centre back line of the pattern piece to see how much of an extension you are going to need. Roughly an extra 0.5cm – 1cm past the button should be fine.
Mark this onto your pattern piece and draw in the new centre back edge.
Now add your seam allowance onto this. I’ve used 1.5cm, but you can use 1cm if you prefer.
That is the extension done but now we need to draw in the facing to neaten off the centre back opening and support the buttonholes.
The back neck facing already does the job of finishing the neckline, so all we need to do is curve that out and extend it so it continues all the way down the centre back.
Lay the back neck facing on top of the back pattern pieces and match everything up. Trace around the back neck facing so you have the shape on the back pattern piece.
Draw in the new back facing line parallel to the centre back, about 6cm from the original centre back line. Take it all the way down the centre back.
Curve the new line in to meet the original back neck facing line. Make sure to blend it in so the new line is a smooth curved shape.
When you have marked the new back facing shape onto your back pattern piece you can trace off the new back facing pattern piece.
Cut out the new back facing and mark on the grain line parallel to the centre back line.
Because you have taken the new pattern piece directly from the bodice pattern everything should match up beautifully.
Sewing the Button-up Back adaptation.
When you make up the Button-up Back Iris, just make up the facing in exactly the same way as before and neaten the whole of the outside edge, from the centre back hem all the way around to the other side of the centre back hem.
And when you attach the facing again just sew it together in exactly the same way as normal, pivot at the corners and continue to sew down the centre back edges. Trim the corners, snip into the curved neckline seam allowance and understitch as you would do normally.
Marking the Buttonholes
Evenly space the buttons to mark out the buttonholes. Make sure the top buttonhole is not too close to the edge of the neckline.
If you want to create horizontal buttonholes make sure to start the end of the buttonhole on the centre back line. Buttons will always pull to the furthest end of the buttonhole. So rather than marking the button hole equidistant over the centre back line so the button sits in the middle, make sure you mark it on the centre back line. That way when the button pulls to the end of the buttonhole it doesn’t gape and pull open.
Measure the end of the button hole so it sits on the centre back line.
Sew the buttonholes in the correct places then mark and sew your buttons on the centre back line.
And now you have a brand new version of the Iris Top.