Friday, August 19, 2011

Racerback Summer Dress Part 1 - Seam Allowances

We're deconstructing the racerback summer dress today!

Today you get the pattern and a lesson on seam allowances. 

There are only two pattern pieces for this dress: the front bodice yoke and the back bodice yoke. Everything else is rectangles.

You all know that I haven't dabbled much in commercial patterns, but the little that I have heard about them has led me to believe that there are two main categories:
  1. those with seam allowances included
  2. those without
and the sewing world is divided into folks who like one or the other, or who used to like one and then started liking the other. I've never drawn seam allowances into my patterns because that was just how I was taught. I simply add them around the paper pattern when I am cutting the fabric out. 

Then people started to ask me questions like "How much seam allowance do you use?" and "Why do some patterns have wider seam allowances than others?" and "Why is there seam allowance at some parts of the pattern and none at others?"

So I thought I'd do something different with this tutorial, and discuss seam allowance. There is a reasoning behind them that, once understood, will enable you to make your own patterns and freely adapt pre-existing ones.

Let's begin. First is the picture again of the pattern pieces:

They have no seam allowances. In other words, they are the exact dimensions of the finished garment bodice. Remember this, because we will add seam allowances to some sides/edges, and explain what they're there for. Throughout this tutorial, at every side/edge of the pattern pieces, ask yourself this important question:
What is this edge/side for? 

The answer to this might be any of the following:
  • It joins to another edge.
  • It is a fold.
  • It is a stand-alone edge.
  • It needs to be finished (e.g. bound, serged etc).
The answer will tell you whether to add seam allowance to it and, if so, how wide. Typical seam allowances are 1/4"-3/8" or 1 cm, but there will always be variations, depending on what that edge is used for,

Next is the obligatory shot of all the fabric pieces. Note that I didn't include thread and elastic and other such stuff. Pay attention: there is a whole bunch of rectangles, and then there are those two bodice-y looking pieces right at the top. We're going to concentrate on those two.

Observe the two aforementioned bodice-y looking pieces. They will be shown together in most of the pictures, because there is a symmetry to their seam allowance allocation that is useful to study.

The left piece is the FRONT (F). The paper pattern is half of the entire front bodice, so the fabric is folded along the center front. The right piece is the BACK (B). The paper pattern is again half of the entire back bodice, so the fabric is again folded along the center back.
Q And this is worth mentioning because?
A There is no seam allowance along fold lines. That is obvious once you can visualize the significance of the center front and center back, but it's always good to revise the basics, yes?

Now look at the bottom edges of these pattern pieces - these will connect to the skirt. Therefore you need a seam allowance for sewing that edge to the skirt. This skirt is a gathered skirt, and it is easier to work with gathers if the seam allowance is wider than usual. I used 1/2". 
Incidentally, you will use this same seam allowance (1/2") for the top edge of the skirt, which gets sewn to those bottom edges. The principle is:
Edges which get sewn together have the same seam allowance.

Next are the sides of the bodice. The pieces are now lined up in the orientation in which they will be sewn together. The sides need to be joined in a side seam, so they will need the (typical) seam allowance for the sewing - 1 cm or 1/4"-3/8".
Using the principle we just introduced, the side seam (front) and the side seam (back) will have the same seam allowance because they get sewn together.

This dress will have bound necklines and armscyes. This means they there are no sleeves or collar and the necklines and armscyes are the final, finished edges of the bodice. They will not be sewn to another edge - no collar, no sleeve, no facings. They will simply be bound with the equivalent of bias tape. Therefore they don't need a seam allowance. 

Now we will introduce the shoulder strap. Behold these are the bodice fabric pieces unfolded to full size, with the paper patterns laid on them, and the skinny shoulder strap rectangle above them. 

Let's start with the front bodice. It has two shoulder edges that will be joined to each end of the shoulder strap. Therefore each shoulder edge needs a seam allowance. It will be enclosed within a double fold of the strap (it will become clear later), sort of like the first stage of a French seam. So we'll make it narrow - about 1/4 - 3/8".

Now for the back bodice. This is a racerback dress, so the back piece has its shoulder edge right in the middle of the back. It will not be sewn to the strap but it will have a casing through which the strap will slide. Therefore we need a seam allowance wide enough to make that casing. We added 1" (width of casing) + 1/4" hem = 1.25" seam allowance.

I want to point out just one more thing before we move on to the actual sewing. In the last two photos, you might have noticed that the bottom edge seam allowance (where it connects to the skirt) is not uniform. It is slightly wider at the center fold and narrower at the side seam. This is a child's pattern, and children have bellies that stick out and raise skirt hemlines. To counter this, children's patterns are usually drafted with a dip in the center front so that the final hemline of a skirt, or the waistline/yokeline of a dress will look horizontal on their round bellies. You can read about it in excruciating detail and consequence here (see Step 21).

If you are using a child paper pattern with a perfectly horizontal hem, like this brown paper pattern, you should allocate to this hem, a wider (e.g. 3/4") seam allowance in the center region and a narrower seam allowance (e.g. 1/2") towards the side seams. 

If you are lucky enough to be using a child paper pattern that already has this adjustment, you can just use a perfectly uniform seam allowance (e.g. 1/2") along the hem. I've already integrated this into the patterns you'll be printing out to sew this sundress. 

Click on the pattern to download and print:

It is in three sizes: 7 year old, 5 year old and 3+ year old. They are not graded patterns - they were drafted to fit my children. Again, in case it wasn't obvious by now (hee!), there are no seam allowances

Coming up: Part 2: Binding with Knit.


  1. Thanks so much for the tutorial, my little girl would love this dress. I have a question, she's into anything twirly at the moment, how do I make the dress even more twirly? Cut the rectangle even wider?

  2. I self-draft my patterns, and do not add seam allowances to my patterns as it makes it easier for me to trace the actual stitching lines.

    Yes in commercial patterns they call it as ready patterns (the ones without seam allowances) and the pattern with seam allowances are called production patterns, few garment industry jargons learnt at my Pattern Master's course ! ;)

  3. Hmmm... methinks I know what Miss C's gonna get for her birthday next year! (If I can remember this by then.)

  4. This was extremely helpful, thanks!

  5. You are really great, my friend!!One more time, THANKS for share your patterns with us!

  6. beautiful beautiful THANKS for share your patterns


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