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Tutorial – Piecing a diagonal quilt back

Have you ever come across the technique of piecing a quilt back diagonally? It’s some cutting magic that means you can use less fabric to make a quilt back by effectively ‘stretching’ it width-ways. Magic, I tell you!

It’s a really efficient way of using fabric (bye-bye buying twice the finished quilt length in backing fabric or spending lots of time piecing a backing together!), especially for those throw sized quilts that measure just slightly bigger than a width of fabric, say 48″-60″ wide.

Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!

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I first came across this technique about a year ago when I was making the Wedding Quilt – I had some fabric which was Just Perfect for the backing, but not enough yardage to make the size I needed.

From what I can find, the idea of piecing a quilt back diagonally was created by John and Joan Flynn and works best with quilts that are no more than 1.5x the width of the backing fabric.

There is some maths needed to work out what yardage you will need. However, the quilt sizes that I have most often used this for are;

Finished Size of QuiltAmount of Backing fabric needed
(assuming 44″ wide fabric)
50″ x 65″75″ (2.1 yards)
55″ x 70″93″ (2.6 yards)
60″ x 75″118″ (3.3 yards)

If you are using extra wide fabric or making a different sized quilt, you can find a calculator here which does all the hard work for you!

For this quilt, I was looking for a backing that measured 52″ x 72″ and used a piece of fabric measuring 85″ (remember, that you want the backing to be bigger than the quilt to allow for basting and quilting).

Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!

Fold the fabric in half diagonally. This is a little fiddly – I would recommend taking your time and trying not to do it when there are kids running around as you definitely need a flat surface!

Cut along the diagonal line, to give two triangular pieces of fabric. You can do this with scissors, but my preferred method is to use a rotary cutter, ruler and cutting mat. Place the ruler on the fabric, leaving the fold showing and trim off a slither (about 1/8″) to cut the pieces.

Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!

If you have a slippy floor (I was working on my tiled kitchen floor!), you can slide the mat along the floor under the fabric easily without ruching the fabric. It’s a lot quicker and more accurate than using scissors.

Fold the top fabric back, and then slide the thinnest point of one half away from the other (this makes the fabric wider and shorter).

Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!
Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!

Measure to double-check that the fabric is now measuring what you need (remembering to take into account the fabric that you will lose in the seam allowance).

Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!

At one end, pinch the fabrics RST and pin – I generally just use one to keep the fabric in the right position before sewing.

Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!

Using a walking foot and at least a 3/8″ seam allowance, sew along the seam. TIP – because the fabric is cut on the bias, be careful NOT to stretch the fabric as you’re sewing (a walking foot helps with this).

Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!

Press the seam open.

Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!

Square off each of the pointy ends – I like to use the grouting lines in my tiled floor as a groove for my scissors to sit in to achieve a straight (ish) line! It doesn’t need to be accurate at this point, I just don’t want the pointy ends getting in the way when I’m quilting!!!

Picture Tutorial for piecing a quilt back diagonally, a great way of stretching fabric further!

And Ta-Dah! You’re finished and ready to make a quilt sandwich! And the seam is virtually invisible, especially if using a patterned fabric.

I’ve found it to be a great way of stretching yardage, it saves piecing a quilt back and is quick too! I hope you’ve found this useful – do let me know if you have any questions,

Speak soon,

S x

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6 Comments

  1. October 23, 2019 / 4:02 pm

    Wow – this is the coolest thing I’ve seen in ages. This technique would have saved me a lot of grief on a few of my past quilts! Am bookmarking for future.

    Thank you!

    • Sonia
      Author
      October 24, 2019 / 9:38 am

      Hi Nicole! Am so pleased you found it useful and yes! It’s revolutionised the backing of my quilts too!!!! Sooooo much easier!

  2. Mona Roberts
    October 28, 2019 / 1:43 pm

    Awesome!!! Sew happy to learn this trick since my favorite charity requests quilts 55″ x 65″. I think this diagonal seaming is going to be nicer loaded on the longarm. Win-win! Thanks again.

    • Sonia
      Author
      October 28, 2019 / 4:14 pm

      So glad it was useful! And yes, great for charity quilts and hopefully easy to load on your longarm!!!!

  3. KATHRYN RINTOUL
    November 1, 2019 / 10:30 am

    This is genius – I recently bought not-quite-enough end-of-bolt to back a quilt and have been scratching my head how to stretch it to fit, so this looks perfect for my needs!

    • Sonia
      Author
      November 3, 2019 / 7:31 pm

      Excellent – I hope it helps you out! It’s helped me out of a few tight spots!!!

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