How to sew princess seams

Princess seams are a gorgeous alternative to darts for adding shaping to a garment. If you haven’t sewn princess seams before, you may be look at your pattern pieces and wonder how you’re going to get the opposing curves to join together smoothly, without puckering. Read on for my tips on how to sew them successfully...

What are princess seams?

Princess seams are curved, vertical seams down a garment that create smooth lines which flow over the bust and/or hips. You may see them on a dress, pencil skirt, fitted jacket, and more.

I’m demonstrating on our Noa pinafore sewing pattern. You can use these same tips for other patterns.

Tip 1: Staystitch the curves

Curved raw edges are liable to stretching out of shape from handling and sewing, so the first step after cutting out your pieces is always to staystitch the princess seams. All staystitching means is sewing a single line of stitching on each piece separately, within the seam allowance – so about 10mm (3/8in) from the raw edge. The stitches will help to hold the fibres in the fabric together.

Ironically, the process of staystitching itself can contribute to stretching. So, to avoid the pieces stretching out asymmetrically, staystitch in the same direction on each piece – sew from top to bottom.

Tip 2: Clip into inward curves

While the stitching lines on the side and centre pieces should be exactly the same length, the raw edges will be different lengths since the curves are different shapes. The raw edge of the inward (concave) curves will be shorter than the raw edge of the outer (convex) curves – so it can be helpful to open out the inward curves to release tension and make it easier to pin the pieces together.

In short, this means clipping into the inward curves (usually the centre pieces). I'd usually do this on very pronounced curves, such as over a full bust area, or on stiffer or heavier fabrics. It probably isn’t necessary for shallower curves, or for stretchy, lightweight or fluid fabrics. Simply cut a few short snips into the seam allowance at right angles to the raw edge, up to but not over the staystitching. If the seam has notches, you can make the clips a different length to avoid confusion.

Tip 3: Pin at right angles to the raw edges

When it comes to pinning the princess seams together, insert the pins at right angles to the raw edges, rather than parallel to them. This will make it much easier to match up the stitching lines of the curves (15mm or 5/8in from the raw edge) without the seams puckering.

Start by pinning together the corners and any notches, then pin together the rest of the seams, easing the curves together as you do. The pieces won’t sit flat – they will probably naturally try to curve up, and that’s a good thing!

Now you can stitch the seams carefully, taking your time so you can ensure you don’t accidentally catch any pleats of fabric in the stitching. Check the seam on both sides once you’re done.

Tip 4: Notch the outward curves

Before we press the seam allowances, we want to take out some of the excess length in the seam allowances on the outward curves to help them sit flatter.

Notch the most curved parts of the seam on the outward curved layer only (usually the side pieces), cutting small triangles into the seam allowance. Take care not to cut across the stitching lines.

Now you can trim the seam allowances, and finish them with zigzag stitch or an overlocker (serger). Yes, it’s fine to zigzag stitch or overlock across the notches!

Tip 5: Press with intention

The final step in creating your beautifully smooth princess seams is to press, press, press! Use steam if your fabric can handle it (test the iron on a swatch first), as this will help soften the fabric to make it more malleable.

As the seams are curved, rather than lying them flat on a table, it can help to press them over a curved shape. A tailor’s ham is great for this. But if you don’t have one, you can use a rolled up towel.

Princess seams will usually sit flatter when the seam allowances are pressed towards the inward curves, particularly if the curves are very pronounced – so, usually towards the centre. But if you prefer them to be pressed towards the side seams, that’s fine, so long as they play ball!

Sewing princess seams can feel a little fiddly at first, but once you put these tips into practice, you’ll be amazed at how neat and professional your garments look! Give them a whirl when sewing the Noa pinafore or other sewing patterns.

P.S. If you liked this post, you may also like How to sew an invisible zip.

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Author: Tilly Walnes
Photos: Jane Looker