Invisible Seams: How to Seam Handknits Using Mattress Stitch

All you need to join your knitted pieces together using mattress stitch: yarn, a tapestry needle and a pair of scissors.

Sometimes, I feel like I might be the only person in the world who enjoys seaming.

Growing up in the golden age of Rowan magazine, I didn't know there was any other way. As a teenager, I even seamed a hat! (I find this so amusing now)

These days, knitting in the round is far more popular and seaming is out of favour. Most of the top knitwear designers tend to make sweater patterns knitted top-down, in the round and that's what many knitters want.

I, too, love to knit in the round and have designed several patterns, such as my Shorthand Sweater, seamlessly. It's simple, fast and easy to try on as you go along. Nevertheless, I strongly believe that seamed garments have their place too.

Why You Should Seam some of Your Handknits

Seams give structure and support to a handknit garment, which will help to avoid sagging, stretching and wear and tear. For anything that can easily go out of shape (e.g. superwash and alpaca yarns) or needs some additional structure (e.g. linen, which has a tendency to bias), seaming is essential.

Add to Cart

One of my recent sweater designs, Nutkin, released in Issue 5 of Laine Magazine, is intentionally designed with seams. My recommended yarn, Islington DK, is superwash and very drapey. By adding seams, I am ensuring that the garment will stay in shape for much, much longer.

Likewise with my Fragment t-shirt. Linen yarns, such as Sparrow, will create fabrics that naturally bias - even high-quality ones. This will create twisted garments which knitted in the round, which is pretty frustrating. Seams keep this bias under control so that your garments hang beautifully.

Joining Knitted Pieces Using Mattress Stitch

I think a lot of what holds people back from knitting seamed garments is fear. I recently received an email from a lovely woman who had several sweaters knitted up and set aside because she was afraid of messing up the seaming part. She was even considering frogging!

Despite what some might think, seaming is very simple when you use Mattress Stitch. It creates a flat, almost invisible seam that is very strong. Whilst some knitters use back stitch - including my favourite designer Julie Hoover, this is the only stitch that I use because it is difficult to go wrong and looks SO professional.

To prepare your pieces for mattress stitch, it can be helpful to block each piece first. This will make seaming easier because the edges will behave. That said, I didn't block until I'd sewed together the whole garment for years and it never did me any harm. Whilst this step is recommended, it isn't essential.

Mattress Stitch Tutorial

In this mattress stitch YouTube tutorial, I will show you just how easy it is to create a really beautiful seam. You will learn:

  • How to use your existing ends to seam up

  • How to anchor a new yarn end to the bottom of the seam

  • How to sew knitted edges together using mattress stitch

  • How to level out the top and bottom of mattress stitched seams

How to Sew Side Seams in Knitting

Side seams are the easiest seams to sew using mattress stitch because they are vertical.

When knitting the pieces, make sure you work your increases at least one stitch away from the edge and always use a selvedge on the edge stitches. This might mean slipping the first stitch of every row or, my favourite, knitting the first and last stitch in every row to create a column of garter stitch at each end.

It doesn't matter whether you have straight sides or waist shaping - just sew your mattress stitch one stitch from the edge.

Even though I am using a contrasting yarn, the mattress stitch seam is barely visible.

How to Set-In Knitted Sleeves using mattress stitch

This is slightly trickier than side seams, but only just. Some knitters prefer to use back stitch here, but I still find that I get the best results with mattress stitch.

At the beginning of the armhole and the sleeve head, you will generally have a few bound off stitches. In this section, you will work horizontally across the fabric rather than vertically, going under a whole stitch rather than two ladders. The rest of the process is the same.

Once you get past the bound off section, you will be sewing just as you were for the side seams, except at an angle.

Sewing SHoulder Seams in Knitting

Should you use mattress stitch on shoulder seams? I did for years, but I was never happy with the finish. As hard as I tried, the seams weren't as smooth as I wanted them to be.

Instead, I recommend that you use short row shoulders to create a super neat shoulder slant and then join the live stitches together using a three-needle bind-off. When I tried this method for the first time, I never went back!

How do you seam your handknits?

Are you a lover of mattress stitch or do you use a different method to sew your knits together? Perhaps you avoid seamed sweaters entirely! Share your experiences in the comments section below. I'd love to hear from you!