Thoughts on the French Seam

It’s your favourite garment and when you take it off, would you rather see this:

Or this:

If you answered B, then maybe you’re thinking of incorporating more French Seams into your work!  Perhaps you haven’t a serger/overlocker and, like me, you’re aiming for a more professional finish.  The French Seam certainly brings a touch of couture-like neatness in return for very little effort.  It’s also:

  • Durable – so you get a second chance if you burst a row of stitching on your overtight trousers….!
  • Enclosing – useful if your fabric is light and frays easily, such as the wonderful voile

We’ll get to the downsides too!

The Tutorial Bit

It’s not rocket science but there’s more than one way of adapting the typical 1.5cm (5/8″) Seam Allowance of a commercial pattern into two lots of stitching that form the French Seam.

Option 1: 1cm followed by 0.5cm

Use the 1cm Seam Allowance guide on your machine to sew the first row.  Remember: wrong sides together.

Press (to embed stitches) and trim the seam.

Flip the fabric so it’s right sides together, then using the 0.5cm Seam Allowance guide stitch again, ensuring the fabric is folded as close to the first seam as possible.

On the wrong side, the finished seam when pressed to one side will look like this.

Advantages: neat, no bulk, inconspicuous.

Disadvantages: if the garment proves too small, there’ll be only about 1.5cm total in the seam to remake it.  


Option 2: 0.5cm followed by 1cm

Swap the Seam Allowances around, so with wrong sides together, sew with a 0.5cm Seam Allowance. Trim very carefully, aiming to take off a mere 2mm (or skip the trim).

Flip to right sides together and sew along the 1cm Seam Allowance guide.

The result is neat, if slightly bulky.  Good for medium-weight fabrics or denim.  Also useful if you might need to let the garment out later, e.g. kids’ clothes.


The Golden Middle: 0.75cm followed by 0.75cm.

How about splitting the width of the Seam Allowance exactly in half?  Sure, except that most sewing machines don’t have a 0.75cm seam guide.  Or maybe your machine has Imperial SA guides so none of the above was helpful anyway.  Well, there’s a solution…

First, adjust your stitch length to something like a basting stitch.

With wrong sides together, run some basting stitches along the 1.5cm (or 5/8″) Seam Allowance. 

Then change your stitch length to normal and sew half way along the width of the Seam Allowance.  You can eyeball this measurement.  Trim. 

Pull out the basting stitch.

Do not press to embed stitches as the fabric will puff out and those helpful needles holes will just disappear.  Instead, pin fabric with the right sides together and stitch, using the needle perforations as your Seam Guide

And voilà, the wrong side and the right.

No bottoms will be bursting out of these Bermudas!


How to Notch (and Not)

When using French Seams, beware of Notches.  Don’t cut them out like this:

Or else, you’ll end up with Fish Lips.  Which isn’t the end of the world, but still…

Knotch out instead.  The extra fabric can be trimmed away after seam number 1:


When Not

French Seams are not always appropriate: for example, you don’t French Seam Neoprene.  The seams would bulge like sausages.  French Seams are your worst enemy if you’re making a costume for a marathon-runner as even if the garment was loose, the chafing would amount to some serious wounds .  Flat-locked seams are the way to go. 

And sometimes, for example when making a pencil skirt, when an area needs to look as smooth as possible, seams that can be pressed open are a safer bet.


How do you like your French Seams?  Do you use them 
or do you think they add unnecessary bulk?  Do you call them something else?  Dites moi tout!

8 thoughts on “Thoughts on the French Seam

  1. It seems I’ve read somewhere that french seams aren’t great for curves. Since you lead with the example of a crotch curve, maybe it’s just sharp curves, or convex curves?

    • You’re right. I’d imagine on a convex curve, where the seam curves out, you’d have to snip into the seam allowance which would spoil the neat look. But on loose trousers or shorts, it works fine. Probably wouldn’t want to try it on a tighter trousers (the chafing… 🙁 ) but that’s where the flat felled seam comes in handy.

  2. I love reading your tutorials – every step is covered by perfect, in focus photos. I didn’t know there were so many ways to French! Apparently, this is a verb now!

  3. The first photo you showed (the one with a straight line of stitching and a tiny zig-zag next to it) is actually an alternate method of doing a French Seam. The advantage is that the zig-zag makes it easy to cut off the excess seam allowance because the width of the zig-zag marks it.

  4. You’re right about the french seam bringing a couture-like neatness. I had a look inside a Stella McCartney blouse – all finished with french seams!

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