What is a seam? The answer might “seam” simple at first. It’s a row of stitching that joins two pieces of fabric or material. But there’s a lot more to it than that. There are different seams for different purposes. There are also a variety of techniques for joining fabric in different ways. Knowing which seam to use and how to form it can help you to make the most of your project.
- 1 What is a Seam, Exactly?
- 2 How are Seams Used in Garments?
- 3 Seam Guide: Different Types of Seams
- 3.1 Single Seams
- 3.2 Double Seams
- 3.3 Shaping Seams
- 3.4 Decorative Seams/Seam Finishes
- 4 Knowing What Type of Seam to Use
- 5 Seam Finishes
- 6 What is Seam Allowance?
- 7 Seam Sewing Tips
- 8 Final Thoughts
What is a Seam, Exactly?
The simplest definition is this: a seam is a row of stitching that joins two pieces of fabric or material. But after that, things get a bit more complicated.
There are functional seams, which make up the construction of a garment. There are also decorative seams, which shape and decorate that garment.
Flat seams sit, well, flat, while ridge seams form a ridge or bump. Inconspicuous seams hide on the inside of the garment, while conspicuous seams are meant for the world to see.
And on top of that, each of these categories contains a number of different seams, each with their own purpose and technique.
How are Seams Used in Garments?
The first division is functional and decorative seams. It’s a bit of a misnomer, as decorative seams, too, serve a function. Let’s have a look.
Most clothing consists of fabric pieces joined together with seams.
Side seams go up the side of a garment, attaching front and back pieces. Back seams (and sometimes front seams) join left and right pieces. A shoulder seam holds a top together at the shoulders. An inseam runs along the insides of trouser legs, joining the pieces there.
“Decoration” sounds frivolous, but it’s not. Decorative seams don’t just add visual appeal to a garment. They also give the garment shape and help to shape it to the body.
One type of decorative seam that does a lot of heavy lifting is the Princess seam. Princess seams are most often seen in women’s wear. They shape the bodice of a garment to a curved bust and waistline, eliminating the need for darts.
The linen seam joins two pieces of material at the edges using a decorative or embroidery stitch. It’s not particularly strong, but it is pretty.
A channel seam forms an open channel over a contrasting piece of material, so that when the wearer moves, the seam opens to reveal a flash of color or pattern.
These are but a few examples.
Pleats are folds sewn into a garment, for example a skirt. They add fullness to the garment, as well as shape and movement. It’s a clever way to add space to a garment without increasing its width.
Pleats can be vertical or horizontal. They may be crucial to the structure, or they may be primarily decorative. Either way, though, a seam is crucial for securing the pleated piece and attaching to the garment.
Seam Guide: Different Types of Seams
We’ve examined seams by function, and seen some of their applications as far as garment making. Let’s have a look at specific seam designs.
Single seams involve, you guessed it: a single row of stitches. Here are some common ones.
A plain seam is exactly what it sounds like: the simplest possible joining of two pieces of fabric or material.
Plain seams typically use a straight stitch or tight zigzag stitch, and leave a seam allowance of one-quarter, three-eighths, or half an inch.
To make a plain seam, place your fabric pieces together with the right sides facing.
Line up your fabric edges with the seam guard markings on your needle plate. Stitch, and then press your seam flat.
Clipping your seam allowance after stitching will reduce the seam’s bulk. If you’re sewing on a curve, clip wedge-shaped pieces from the seam allowance along the curve.
A lapped seam is both decorative and functional. On the surface, it looks similar to a flat felled seam. However, it’s a single seam rather than a double one. Also, a lapped seam doesn’t enclose the seam edges. Rather, you serge off the seam edges on the wrong side of the fabric once you’re finished.
Lapped seams are excellent for:
- Non-fraying fabrics and materials, such as vinyl
- Reducing bulk (unlike a French or felled seam)
- Adding a decorative touch
Here’s how to make a lapped seam.
- Lay your first piece of material flat, right side up.
- Decide on your seam allowance.
- Lay the second piece of fabric on top of the first, wrong side up, lining up the edges. Right sides should be together.
- Fold the top fabric back along the seam allowance so that the right side of the top fabric is showing.
- Press if you desire.
- Stitch along the folded edge.
- Turn your work over and serge or overlock the seam edges.
Confused? Don’t be. This video will make it clear.
Double seams use two rows of stitches. They tend to be very strong. Many also hide raw seam edges.
To make a welt seam, first make a plain seam, as above. Then on the back of the fabric, press the seam allowance to one side, and secure it to the fabric with a second row of stitches.
A French seam is a double seam that encloses the rough edges of both pieces of fabric. It’s a great seam to use when:
- The fabric edges fray easily
- You don’t want the fabric edges or your seam to show
French seams protect the edges, keep them out of sight, and provide a double-strong seam.
They’re not difficult to make, either, though the setup is a bit different from a plain seam. You may also have to adjust your pattern’s seam allowance.
Here’s how to sew a French seam.
- Start with the wrong sides of your fabric pieces together (rather than the right sides).
- Stitch the first seam. The video below recommends a half-inch seam allowance, though you might prefer a different allowance.
- Trim the seam allowance to around one-quarter inch.
- Press the seam flat.
- Fold the fabric over so that the right sides are now facing.
- Press flat again.
- Sew the second seam to encase the raw edges.
- Press the new seam to one side.
Watch the entire process below.
Flat Felled Seam
A flat felled seam is a double seam that encloses the raw fabric edges. It’s very strong and durable. For this reason, it’s a favorite on garments meant for heavy wear, such as denim trousers and jackets.
A flat felled seam is similar to a French seam, however there are a few extra steps. The topstitching at the end gives the flat felled seam its very recognizable appearance.
Here’s how to make a flat felled seam.
- Start with the wrong sides, rather than the right sides, of your fabric pieces together. You will be working on the right side of the fabric.
- Stitch the first seam using the seam allowance of your choice.
- Decide which way your seam will lie. The seam allowance that will be on top is the top. The part of the seam allowance that will lie against the garment unseen is the bottom.
- Trim the bottom seam allowance by half.
- Fold the top seam allowance over the bottom one to enclose the edges.
- Press again to form a sharp crease.
- Now press the entire enclosed seam against the face of the garment.
- Finally, topstitch the seam down, as close to the folded edge as you can.
Want to see the process from start to finish? Check this out.
Slot (Channel) Seam
The slot, or channel seam is a way of adding a pop of color to your project. Structurally, it’s like a double lap stitch, with the laps facing one another.
The slot seam is both decorative and functional. Here’s how to make it.
- Place your two fabric pieces together, right sides touching.
- Baste along the seam allowance. You’ll be removing this row of stitches later.
- Turn your fabric over and press your seam open.
- Now, pin your contrasting strip over the open seam edges.
- Turn your work over, and sew two rows of stitches, one on each side of the basted row. How far apart you sew them is your choice, but they should be equidistant from the center.
- Take your seam ripper and remove the basted center row.
Here’s another video showing you how it’s done:
These are a few types of seams that you can use to add shape to your garment.
A Princess seam is a way of shaping a top, bodice, dress, or coat to complement a curved bustline and waist. The seam begins at the shoulder, curves slightly inward over the bust, coming back out again at the waist.
The Princess seam is both structural and decorative. It connects the front panels of a garment, and also adds shape.
A Viennese seam is similar to a Princess seam. It’s a curved seam that connects the front panels of a garment, and accentuates a curved waist and bustline.
Unlike the Princess seam, however, the Viennese seam begins at the armhole, rather than at the shoulder.
Decorative Seams/Seam Finishes
Decorative seams add visual appeal to a garment or project. They may be structural, also. However, many of them are not very strong.
Abutted (Butt) Seam
An abbutted seam joins two pieces of fabric together without overlapping them. There is no seam allowance. Instead, you sew a zigzag stitch over the fabric edges, joining them this way.
It’s not a very strong stitch. However, it’s a good stitch for when you want to reduce bulk, such as when sewing lingerie.
Sheet Seam or Linen Seam
A Sheet Seam, or Linen Seam is a type of abutted seam. Instead of a zigzag stitch, however, you join the pieces together with a decorative stitch.
Hong Kong Seam
A Hong Kong seam isn’t so much a seam as the way to finish one. It’s often called a Hong Kong finish.
To add a Hong Kong finish to your seams, you either serge off the seam edges or bind them with seam tape. Using a seam tape of a contrasting pattern or color can add a luxurious touch to the inside of your garment.
This technique is most often used in unlined jackets and garments.
Here’s how to do it:
Knowing What Type of Seam to Use
So now that you have an idea of some of the many seam types out there, how do you know which one you should be using? A good way to tell is to think about what you’re trying to accomplish.
Shaping Your Garment
If you want to shape your garments for a curved body type, think about these.
- Princess seam
- Viennese seam
When You Want to Hide the Edges
If you want to hide your raw seam edges, try these.
- French seam
- Flat felled seam
- Hong Kong finish
Securing Fabrics that Fray
If you’re working with a fabric that’s prone to fraying, and you want to secure the edges, these are the seams to think about.
- French seam
- Flat felled seam
- Welt seam
- Hong Kong finish
Heavy Duty Seams
For seams that will take a beating and stay strong, you want one of these.
- Flat felled seam
- French seam
To add some flair to your project, check these out.
- Channel seam
- Linen seam
- Abutted seam
- Lapped seam
- Hong Kong finish
The “finish” of a seam refers to how you deal with the raw edges of the seam allowance. When using non-fray materials such as vinyl, you can leave the edges raw. However, if you have a fabric that frays easily, you will definitely want to finish those edges. Finishing your seam edges can also add a professional touch to your project.
Pinking shears cut the edges of your fabric in a zigzag pattern.
You can pink your seam edges for a neat finish, if:
- The fabric is not overly prone to fraying
- Your garment will not be worn a lot
- You won’t be washing the garment often
You can finish most seam edges with a zigzag stitch, as long as the fabric is relatively strong and stable.
If you have a serger or an overlock stitch, you can also serge off your seam edges. You can even do this before sewing your seam.
If you have a generous seam allowance, you can use this technique to give your seams a professional touch.
On the wrong side of your garment, press your seam flat. Now fold each side of the seam allowance in half, so that the raw edge is on the underside. Press and secure with a straight stitch. Then finish the other side. You can also finish your edges before you sew the seam.
What is Seam Allowance?
When you look at many patterns, you’ll notice that the pattern pieces are larger than you might expect from the measurements of the finished garment. This comes down to seam allowance. Seam allowance is extra width which will accommodate your stitching.
After you’ve stitched your seam, the seam allowance will not figure into the measurement of the garment. You might finish off your seam allowance using one of the finishes we discussed above. You might also trim it.
Seam allowances vary from pattern to pattern. Here are some different standards and when you might use them.
- A ⅜ inch or half-inch seam allowance is a good general standard.
- A ¼ inch seam allowance is good for curves, as it doesn’t add a lot of bulk.
- If you’re serging or overlocking your seams, many experts recommend a ⅜ inch or ½ inch seam allowance.
- If you’ll be adjusting the fit of your garment, a ⅝ inch seam allowance will give you room to do that.
- Use a ⅝ inch seam allowance for French or Flat felled seams also.
Seam Sewing Tips
So, now that you know how to choose your seam, and the basics of how to produce it, how can you get the best possible results?
Choose the right seam type for your purpose. Do you:
- Want to hide your edges?
- Need a strong seam?
- Plan to sew structure into your garment?
- Want to add a decorative touch?
If so, there’s a seam for that. So find it.
If you’re working with a fabric that doesn’t like to hold its shape — think chiffon or similar — consider using a stabilizer, such as:
- A spray-on, wash-out stabilizer
- Iron-on interfacing
- Tissue paper pinned to the back of the fabric and removed later
Make Friends with Your Guide Lines
The guide lines are those measurements marked on the needle plate of your sewing machine. Line your fabric edge up with the appropriate line and keep it there while you sew. This will ensure that your seam is straight, and that the measurements of the garment will match the pattern measurement when you’re done.
Take Your Time
It’s just a straight line, right? Wrong! Don’t hurry through your seams, especially if you’re using a complicated or decorative design. Slow down and take the time to do it right.
- Dial down your sewing machine speed to ensure consistent, high-quality stitching.
- Remember the old saying, “measure twice, cut once” — or, in this case, stitch once.
- Check and double check your guide lines.
- Press your seams and creases.
Clip Your Allowance
If you want to reduce bulk once you’ve sewn your seam, you can clip your seam allowance closer to your line of stitches. If your seam is curved, you’ll want to cut notches along the seam allowance in order to facilitate the curve.
Finish Your Seams
In a lot of cases, you can leave your seam edges raw. After all, they’re on the inside of the garment. No one’s going to see them.
On the other hand, why not take that extra step and give those edges a nice finish? It doesn’t take that long. It can help your garment to last a bit longer, and to look more professional, too.
For more advice about specific techniques, don’t miss our upcoming article, How to Sew a Seam.
If you’ve made it this far, you’ve probably learned more about seams than you thought there was to know. And this article only scratches the surface!
Seams play a variety of different roles in project construction. From assembling the pieces of a garment, to giving it shape, to adding strength or decorative flair, seams are at the heart of any project.
What’s your favorite seam to use? Do you have any tips or tricks for people who might want to learn it? We’d love to hear about it in the comments. And if you enjoyed this article, please share it!