Wednesday 3 July 2013

Half Rectangle Triangles

Half Rectangles are tricky. They are very similar to Half Square Triangles but there is a little trick to making them. I needed a roof for a pieced house I was designing and it took three attempts to get these right.

Of course I could have paper pieced them but I got stubborn after attempt number 2 and was determined to figure it out. I thought I'd share with you what I did wrong and how I finally got what I wanted.
For the house above I wanted to use a layer cake, so I was working with a maximum size of 10". I came up with the bright idea of piecing it using Half rectangle Triangles and sewing them together. The size I needed for the roof wasn't a nice 2:1 like a flying goose but 10" wide by 4" high finished dimensions.

Well, on the first attempt the mistake I made was to treat the rectangle like a square and forget that rectangles are not symmetrical. I started with 5.5" x 6.5" rectancles, deciding to go big and trim down later.

Placing the fabric right sides together and using the HST method of drawing the diagonal then sewing 1/4" either side gives a very wonky result like this:
Oops!  I have no excuse, I knew it wasn't going to work as I was cutting it, but I figured keep going and I'll discover where I went wrong.  The trick is to rotate one of the rectangles and lay them out long edges across each other.  Here's the layout using the triangles I finally used in the roof:
This gives two identical half square triangles which will give me the left roof. You need to do another with the diagonal line going in the opposite direction to get the right hand part of the roof because half rectangle triangles aren't symmetrical.  That is well stick in my head now!

I did this and got 4 Half Rectangle Triangles and then I trimmed two of them down to the dimensions I wanted for my roof. To make up 10.5 x 4.5 I trimmed them to 4.5 x 5.5 as I will lose 1/4" in the middle when I join them.

On attempt number 2 I didn't pay enough attention trimming and ended up with rectangles with seam allowance for the bottom of the roof but clipped the top off the house!

Of course I only noticed this when I had sewn it to the base of my house. Not the end of the world, I could probably live with it in the project I'm making for myself but I had hoped to put this up on my blog as my first ever pattern so it's got to be right.
At this point I figured I'd take a break and go check out blogland - yes I really should have done this earlier!

 I found these three tutorials on Half Rectangle Triangles confirming for me that my starting dimensions were ok, my layout of fabric right sides together was on the right track but what I had not done was to take my 1/4" seam allowance into consideration when aligning the fabric or drawing my diagonal.  Oops again!

The modern quilt guild

Wayne Kollinger's Quilt Blog

The Busy Bee Quilt Shop

So third time around, I decided to try Wayne Kollinger's method and started my diagonal 1/4" up the rectangle both sides.

Ta-dah!!! Success at last.

On this final attempt, I decided if it wasn't going to work out I would just paper piece it . Well it did work out but now that I have the idea of paper piecing in my head of course I'm going to have to try that too! So I've downloaded the free software Quilt Assistant and once I practice with it a bit more I'll tell you all about it.

For now I'm just happy to have the test piece for my cushion/pillow project pieced and measuring the right dimensions!


  1. Ruth

    I'm glad my method worked for you.
    On my blog I posted 3 different methods for piecing haf-rectangle triangles.
    If you want to try paper piecing,you might want to go with the third method which uses freezer paper.

  2. Hi Wayne, Happy 4th of July, thanks for the tips. I was so happy when my roof finally came toghether to the size I wanted. There are so many ways to do things, it's a constant learning cycle. It's hard to get freezer paper here in Ireland but I'll keep looking and give it a try.

  3. Ruth

    Instead of using freezer paper youy could try pinning.
    I don't find it as accurate but it might work for you.


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