Open Seams – Sewing Tutorial for Beginners

Open seams are one of the most common seam types used in sewing. They are simple, flat, beginner-friendly, and suitable for everything from dresses and skirts to shirts, trousers, and home décor projects. Unlike with closed seams, the seam allowances are pressed open after sewing rather than enclosed within the seam. Because the seam allowances remain visible on the inside of the garment, open seams usually require seam finishing to prevent fraying. In this tutorial, you’ll learn how to sew open seams step by step, the best seam finishes to use, and tips for sewing open seams on stretch fabrics.

What are Open Seams?

Open seams are seams in the fabric where the edges have been pressed, separated, and opened. Open seams are quick and easy to sew, but because the edges show and can fray, the seam needs to be carefully neatened. Neatening the edges of an open seam is particularly necessary if the seam is visible on the reverse side of the item or if the fabric frays excessively. 

If you are learning sewing construction methods, explore the full types of seams guide to compare open seams with enclosed seam finishes.

Open Seams vs Plain Seams: Don’t confuse open seams with a plain seam. A plain seam is stitched, and the whole seam is pressed to one side while the open seams are pressed open.

How to Sew Open Seams (Step by Step)

Here are the four steps to sew open seams, followed by four ways to neaten open seams once you have completed the seam successfully.

1. Optional: Finish the Edges

At some point, you will need to finish the raw edges of your seam allowance. This can be done on the pieces before or after the seam is sewn.

I always prefer to finish the seams at the end, but on rare occasions, your pattern will specify to finish the raw edges first. See the finishing options after the seam instructions.

Seams enclosed in a lining do not need to have their edges finished. Seams sewn with a serger are neatened automatically, as the serger does the job of sewing, cutting, and neatening all in one simple seam. 

2. Stitch the Open Seam

Put the right sides of the fabric together. Match any notches or markings together to get an accurate seam matching. It is advisable to cut notches pointing out and not cut into the fabric edge.

Sew a stitch line with your sewing machine along the seam allowance.  Sew to the end of the seam allowance and remember to start and end with a backstitch. Read more about how to start and stop seams.

3. Press the Seam Open

Press your seam open on the wrong side of the item. The edges may already be neatened if you did that at the beginning of step one. The iron should be used in an up-and-down motion rather than dragging it along, which may distort the seam line. Read more about pressing fabric for sewing.

4. Finish the Seams

If you didn’t finish the seams before, now is the time to do so. There are four choices set out below.

Seam Finishes for Open Seams

As previously mentioned, the order of finishing the seam edges is a personal choice. Some sewers like to do it before the seam is completed, and some like to do it last. Either way is perfectly fine.

Here are four different ways to finish off and neaten the edges of open seams.

Serger for Open Seams

A serger is a separate machine specially designed for finishing seams. For open seams, you need to make sure your seam allowance is at least 1/2 inch (12mm), as the width of the serged stitches is usually at least 1/4 inch (6mm). In most cases, you will trim the minimum amount of fabric with the serger knife. Read more about how to use a serger.

Pinking Shears

Using pinking shears is a quick and easy way to neaten the raw edges of open seams. Simply hold the two raw edges together and cut along the edge with the pinking shears. The jagged or zigzag edge will prevent the edges from fraying. Pinking shears need to be kept sharp to cut fabric without burring, so never use them to cut paper or anything other than fabric. Read about the best scissors for sewing.

Bias Tape

Using bias tape to enclose the edges of a seam creates a very neat edge and stops the seams from fraying.  This method of finishing is often used to neaten unlined jackets, inside bags, and for quilted edges. It can be a contrast to the main fabric or made out of the fabric itself as a self-made binding.

There are two methods you can use to add the bias tape – Hong Kong finish or a regular bias bound seam. My preference is the Hong Kong seam which is what I have used in the photo below, as the stitching is almost invisible when done in a matching color thread.

On a regular bias-bound seam, you can see the stitching on the bias itself, so you need to be a little more accurate.

Zigzag

A simple zigzag stitch along the edge of the fabric when it has been pressed open will neaten the edges and prevent fraying. You can use a regular zig-zag stitch or a 3-step zig-zag. Stitch a small way in from the raw edge to prevent the edges from rolling over and causing bulk. You can trim closer to the zig-zag if necessary.

What are Open Seams Used For?

Open seams are the most useful seams for sewing plain cotton fabric. The good thing to note about open seams is that the bulk of the fabric from sewing two pieces together is spread on either side of the seam when the open seam is pressed open. 

The open seam is the best seam for the sides of skirts and dresses, and the side seams of trousers too. Open seams are used on the sides of a blouse pattern under the arm and to sew up the side seam of the sleeves. 

The pattern pieces you use will often have markings to guide the joining of the open seam. Sewing notches that indicate a meeting point should be cut outwards for matching purposes. Once the notches have been matched, the seam neatening will trim off the notches.

Tips for Pressing Open Seams

Remember to test your fabric first and make sure your iron setting is at the right temperature for the kind of fabric you are using. A presser cloth, laid over the fabric, lets you press directly onto the seam with some pressure. A further pressing with the tip of the iron along the join of the seam gives the seam a clean, neat open finish. Read more about the best pressing tools for sewing and pressing fabric for sewing.

Open Seams in Stretch Fabric

Although stretch fabrics are wonderful to sew because they do not need to be finished, getting the right stitch for open seams is sometimes tricky. You must practice on a scrap to get it right before setting foot on your good stretch fabric.

Here are some tips to remember as you sew open seams on stretch fabric.

1. NEEDLE – Change the needle on your machine to a ballpoint needle or a stretch needle. Ballpoint pins are advisable too. This prevents snagging and allows for a smoother stitching line.
2. DON’T PULL – Do not be tempted to stretch the fabric as you sew. Let the stretch fabric feed through the machine without pulling. If you pull the fabric your open seams will pucker.
3. SUPPORT – Don’t let the fabric drag to the ground and pull on the garment as you sew. Support the fabric somehow so the seam is not pulled out of shape.
4. STITCHES – Reserve some scraps to practice on and use a small zig-zag stitch instead of a straight stitch. The reason is a zig-zag stitch will stretch with the fabric and not snap when the fabric is pulled or worn.
5. FINISHES – A stretch-knit seam does not need neatening. Ideally, a serger is the best machine to use for the stretch knit fabric. The serger seam would be finished all in one action.
6. READ MORE about how to sew stretch fabric.

Common Open Seam Mistakes and Tips

Common Mistake	Tip for Better Results
Dragging the iron stretches the seam.	Press up and down instead of sliding.
Raw edges fray excessively.	Finish seam allowances properly.
Uneven seam allowances create bulky seams.	Follow seam guides carefully.
Stretch fabrics pucker while sewing.	Avoid pulling fabric through the machine.
Thick seams refuse to lie flat.	Press carefully with steam and a pressing cloth.
Pins distort seam alignment.	Match notches accurately before sewing.
Crooked stitching affects garment fit.	Sew slowly and follow seam guides.
Heavy fabrics stretch while sewing.	Support the garment weight while stitching.

Open Seams FAQs

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Open Seams – In Conclusion

Open seams are one of the most useful and beginner-friendly seam constructions in sewing. Their flat-pressed finish helps reduce bulk while creating comfortable, professional-looking garments. Once you learn how to sew and finish open seams properly, they become a versatile seam option for clothing, tailoring, home décor, and many everyday sewing projects.

More Seam Articles

• Sewing Facings
• Hong Kong Finish
• Seam Finishes
• Grading Seams
• How to Start and Stop a Seam
• French Seam
• How to Sew a Seam