How to Sew Bias Bound Seams

Finishing seam allowances with bias binding is a lovely way to give the inside of your handmade clothes an extra special finish. Not only does it neaten and strengthen the raw edges, bias binding also allows you to add a pop or colour or print to the inside of your garment.

In this tutorial, I’ll show you how to sew bias bound seams, including how to finish edges of seam allowances and facings, bind a full circle (such as a neckline or pocket), and sew a neat mitred corner. It’s a little more work than finishing with an overlocker (serger) or zigzag stitch, but the result is well worth it, especially on an unlined jacket or coat.

What is a bias bound seam?

Bias binding is a strip of fabric cut diagonally across the grain, at a 45° angle to the selvedge. Cutting it this way gives the fabric a little stretch, allowing it to flex around curves and corners.

A bias bound seam is made by stitching folded bias binding around the raw edge of a seam allowance. The binding encloses the raw edge, which strengthens it from wear and tear, prevents fraying, and creates a pretty detail on the inside of your garment.

What seams can you finish with bias binding?

Bias bound seams work well on unlined garments where the inside will be visible when you take it on and off, such as the Manon jacket and Sonny jacket. You can also use it on other woven garments, such as the Arielle skirt, where you want a special, hard-wearing finish. It's also great for adding a special touch to homewares, such as cushions and napkins.

It’s best if the garment fabric is mid- to heavy-weight and the binding fabric light- to mid-weight so it won’t show through to the outside of the piece.

The process is relatively time-consuming, and it does add bulk, so personally I wouldn’t bind hidden seams such as sleeve underarms. On some jackets and skirts, I bind just the inside edge of the facing for a little pop of interest, and finish the others with an overlocker (serger) or a zigzag stitch.

Supplies for bias binding seams

You will need either single-fold or double-fold bias binding for the techniques in this tutorial. You can buy it ready-made in various colours and widths. Alternatively, you can make your own bias binding, which is a great way of using up leftover scraps of cotton lawn, poplin or similar.

For this tutorial, I made my own 20mm (3/4in) single-fold binding.

You will also need thread to match the bias binding.

How to finish a seam or facing with bias binding

Attach the bias binding to seam allowances after sewing the seam, or to the inside edge of a facing (the one that won’t be attached to anything else) before stitching it to your garment.

When binding a stitched seam, you may want to trim the seam allowances a little to reduce bulk. Just make sure they’re still a little wider than the double-fold binding - or half the width of the single-fold binding - so it doesn't overlap the seam stitching. On the loose edge of a facing, there’s no need to trim.

1. Attach the bias binding

Unfold the binding and lay the right (nice) side against the seam allowances or against the right side of the facing, aligning one of the long, raw edges of the binding with the raw edge of the seam allowance or facing.

You can pin (or clip) the binding in place if you like, or on straight seams you could try keeping it aligned with your fingers.

Using thread to match the binding, stitch it in place, positioning the needle exactly along the channel of the fold that’s nearest the raw edge. Back tack at the beginning and end to secure the stitches.

2. Press the bias binding

Press the binding away from the main fabric. You can use just the tip of the iron to avoid over-pressing the project.

Now wrap the binding over the raw edge of the seam allowance or facing to the other side, the raw edge of the binding still folded under. The raw edges should now be enclosed between the layers. Press it in place.

Pin (or clip) the binding in place from the stitched side, making sure the loose fold is caught in the pins.

3. Edgestitch the binding

From the stitched side of the binding, edgestitch close to the inside fold of the binding, stitching through all layers.

As you sew, make sure the loose fold of the binding is getting caught in the stitching – you can feel through with your fingers, or pause occasionally with the needle down to lift up the project and check.

Give the finished seam a final press to neaten it up, and you're done!

How to bias bind in the round

If you're binding an edge that forms a complete loop, such as the edge of the pocket on the Manon jacket, or an armhole where the binding is on show, you'll need to join the two ends of the bias binding neatly.

I'm demonstrating on a loose pocket bag to make it easier for you to see what's going on, but on the Manon jacket you'll be doing this once you've attached the pocket bags to the front bodice.

1. Choose a relatively inconspicuous point to start binding. Leave a short tail of binding – around 2cm (1in) – unstitched at the starting point.

Stitch the binding to the raw edge along the fold channel nearest the edge, following the same steps outlined above. (If there is a corner on the area you are binding, such as on the pocket of the Manon jacket, see ‘How to bias bind a corner’ below when you get to that part!)

2. When you are around 3-5cm (1-2in) from where you started, stop stitching. Trim the binding, leaving a tail the same length as the starting tail. Overlap the two tails and mark a line halfway along where they overlap, marking the same point on both binding layers.

3. Bring the two tails right sides together and stitch along the marked line, pulling the rest of the project out of the way so it doesn’t get caught in the stitching. Back tack at the beginning and end.

4. Trim the unstitched tails, leaving a little seam allowance, and press them open. Now you can now sew this unstitched section of binding to the raw edge of the seam.

Once that's done, press the binding away and around to the underside and edgestitch in place, following the same steps as the section above.

How to bias bind a corner

Bias binding is flexible enough to work around corners, too. For a neat finish, you can create a mitred corner.

Follow the same steps outlined above for bias binding a seam or facing, with a little adjustment...

1. On the first pass, stop stitching just before you reach the corner, leaving a little more than the width of the binding channel unstitched. With the needle down, raise the presser foot and pivot the project to stitch diagonally towards and slightly off the corner, without back tacking.

2. Fold the binding up, wrong sides together, along this angled stitching.

3. Then fold it back towards the next edge, the right sides together, aligning the raw edge of the binding with the next raw edge of the area you are binding, and the fold with the first raw edge.

4. Stitch the next side, again along the fold channel nearest the raw edge, back tacking at the beginning. Continue around the remaining edges, repeating the same process at each corner.

5. Once you've stitched around the whole edge, press the binding away from the project and around to the underside. At the corners, press the edge of the binding on one side of the corner around neatly to the underside – this should naturally create a diagonal angle at the corner. Fold the next edge neatly over it and around to the underside. Pin (or clip) in place.

6. Edgestitch from the stitched side, close to the inside fold of the binding. When you reach the diagonal seam at the corner, pause with the needle down, pivot the project, and continue stitching.

Give the finished binding a final press to neaten the corner and set the stitches.

And there you have it – a beautifully neat mitred corner!

Tips for sewing bias bound seams

• Choose the right width of binding. When buying bias binding ready-made, the width in the listing is usually for the single-fold binding, which is double the width it will be once stitched to the edge. Make sure it will be wide enough to cover the raw edge you're binding, without crossing the seam line.
• Don't stretch the binding as you sew. The bias has natural flexibility, but you don't need to pull it. Let it follow the shape of the edge.
• Press as you go. A good press makes a huge difference to the finished result, particularly around curves and corners.
• Check the underside when edgestitching. It's much less time-consuming to pause and check you're catch the loose fold of binding now than to unpick a whole row of stitching later!
• Try a contrast binding. A bright or patterned binding can turn a functional seam finish into a lovely design detail.

Other ways to use bias binding

Once you've got the hang of bias binding, there are lots of places you can use it in your sewing.

For example, you can use single-fold bias binding to finish a neckline or armhole, where the binding is turned to the inside of the garment. See our tutorial on how to sew bias binding on a neckline or armhole for a video showing you how.

So next time you're making a jacket, coat, or other piece where the inside deserves a little extra love, why not give bias bound seams a go? It’s one of those techniques that takes a little patience, but you'll be rewarded with a finish you'll be happy to show off.

If you'd like to try the technique on a garment, the Manon jacket and Sonny jacket are great choices for an unlined jacket with beautiful opportunities for bias-bound seam finishes.