The flat felled seam is a flat, comfortable seam suitable for medium-weight fabrics and garments requiring maximum durability. This seam makes sportswear and casual wear look very professional and if you have an active little toddler running around, it is hardwearing and perfect for overalls and rompers. They are comfortable because the bulk of the seam is on the outside.
What is a Flat Felled Seam?
A flat felled seam is a simple seam designed to encase raw edges to prevent them from fraying as well as providing an attractive and extremely durable seam.
You can see from this photo below that the inside of the item has a clean finish with no raw edges or finishing visible. This makes it a great seam for people and especially kids who are irritated by serged seams.
These seams are a seam and seam finish all in one! If you don't have a serger then this can be a great alternative to create simple flat open seams.
When to Use a Flat Felled Seam
The flat felled seam is ideal for denim and cotton fabrics but may be too bulky for heavier material. If you look at your denim jeans, shirts, or jackets, you will see lots of felled seams. Flat felled seams are also a great choice for linen since the raw edges are encased preventing them from fraying. It is more difficult to sew around curves and is best used on straight seams if you are a beginner.
- Sewing Basics - Sewing machine, scissors, thread, pins
- Pressing Tools - Iron and ironing board
- Presser Foot - All-purpose sewing foot and optionally an edge stitch foot or felling foot.
Flat Felled Seam - Video Tutorial
Here is a video I made to show you how easy it is to sew this seam. Subscribe to my YouTube channel for weekly sewing videos.
Relax and press play below >>
How to Sew a Flat Felled Seam, Instructions
Step 1 - Seam Allowance for Flat Felled Seam
Before you start, check your seam allowance width. It should be at least ⅝ inch (15mm) wide. Any less than this will result in a really narrow seam that will be hard to sew. Do a test of the seam on a scrap of fabric and adjust the seam allowance if necessary.
Step 2 - Stitch the Seam
Place your fabric pieces with wrong sides together and stitch along the normal seam line. (This is the opposite to what you would normally do so it may feel a little strange!)
Press the seam open. If you have a delicate fabric, use a presser cloth for all pressing so you don't damage the fabric.
Step 3 - Trimming
Trim one side of the seam to a width of ⅛ inch (3mm). It is important that there is no fraying as loose threads can stick out and get caught under your stitching in the next step.
Step 4 - Press and Fold
Press the wider seam allowance (untrimmed) edge over by ¼ inch (6mm).
Fold the wider, pressed edge over to encase the trimmed edge. Make sure the pressed and folded edge is the same width all along the seam. It can look strange if it goes in and out. The smaller seam allowance which was trimmed is now hidden inside.
Step 5 - Outside Stitching
Stitch along the open edge of the seam 1/16 (1.5mm) to ⅛ inch (3mm) from the edge. You want to stitch as close as you can without going off track.
Beginners: Use pins or hand baste with a large running stitch to secure the seam before you sew. Cotton normally irons a crisp edge but slippery fabrics or thin fabrics like silk and polyester will be difficult to sew without some hand basting first.
You can use your regular all-purpose sewing foot, but for really accurate and neat stitching, an edge stitching foot can really help. See how it has a guide in the center that will run along the edge of the seam. You will need to move your needle position slightly to the left rather than leaving it in the center as you would for normal sewing. You could also use a twin needle for extra topstitching.
Further Reading: How to use an edgestitch foot
Using a Felling Foot
The felling foot is a presser foot designed for sewing flat-felled seams. It will glide along the edge of the pressed seam and accurately stitch the edge. This specialty foot comes in different widths so you can match your desired seam allowance. Choose a wider foot for thicker fabrics and a narrower foot for fine or sheer fabrics.
The advantage of the felling foot is that it saves you from so much pressing as the fabric will guide you through the gap in the foot.
Curves and Flat Felled Seams
Flat felled seams are often sewn around curves in the center crotch area of pants and trousers. These give a durable seam that won't unexpectedly rip and cause undue embarrassment.
If you are using the flat felled seam around a curved edge, then clip the trimmed edge of the seam before encasing the seam as this will give more elasticity to the seam and allow you to turn a corner. There is an example of this in my video.
When clipping, put tiny snips every ¼ inch (6mm) making sure you do not cut the stitching line. If you accidentally snip the stitching line, make sure you go back with your machine and reinforce it.
Further Reading: Clipping Sewing
However, it is worth noting that this seam is best suited to the straight path of your seam line or gently curved seams.
Variations of the Flat Felled Seam
Variation 1 - Mock Flat Felled Seam
A mock flat felled seam is a variation used for thicker fabrics such as denim and canvas. This seam is commonly found on the inside of your jeans and denim jackets. It is faster to complete and reduces bulk as the seam allowance does not need to be pressed over.
A mock flat felled seam is best sewn on seam allowances that are at least ½ inch (12mm) wide.
Step 1 - Finish One Side
Finish the seam allowance on one side of your fabric. Ideally, you would use a serger but a simple zig-zag stitch will do the trick if you just have a regular sewing machine. Ensure that the serger knife only cuts the minimum seam allowance as you don't want your piece of fabric to become smaller.
Step 2 - Sew the Seam
With right sides together, sew the seam with your regular sewing machine with your desired seam allowance.
Step 3 - Trimming
Trim down the seam allowance that was unfinished to ¼ inch (6mm) in width.
Step 4 - Press to the Side
Press the finished seam allowance over the trimmed seam allowance. Check the right side to ensure there are no wrinkles and the seam is open and smooth.
Step 5 - Stitch
Stitch the seam in place next to the finished edge. If your seam allowance was ½ inch (12mm) this means you will be stitching around ⅜ inch (1cm) from the seam.
To finish, turn your work to the right side of the fabric and give it a final press to flatten the seam.
Variation 2 - Run and Fell Seams
The biggest difference when you sew a run and fell seam is that the fabric is placed right sides together when you sew the first seam. The folded seam will be underneath and not visible on the right side of the fabric. All you will see on top is a single row of stitching around ⅜ inch (1cm) from the seam.
Step 1 - Sew the Seam
Place your fabric right sides together and stitch the seam. Because we will be folding the seam allowance on one side, it is best for seams that are ⅝ inch (15mm) or wider. Adjust your pattern if necessary.
Step 2 - Trimming One Side
Trim one side of the seam allowance down to ¼ inch (6mm). Use sharp scissors so there is no fraying. If you are using fabric such as linen that frays endlessly, you may want to use some pinking shears instead of regular scissors.
Step 3 - Press
Press over the wider seam allowance (untrimmed) so it folds over the trimmed side. It will encase it so the raw edges are hidden. Also, press the fabric from the right side so the seam and the folded seam allowance below are all sitting flat and smooth.
Step 4 - Stitch
Turn the fabric to the right side and stitch around ¼ inch (6mm) from the seam. It is important to catch in the seam allowance underneath. I use my fingers to feel the seam underneath as I sew to keep on track.
BEGINNERS - If you find this hard to keep straight, you can always sew from the wrong side instead. The reason it is better to stitch on the top is that the stitching will just look neater. The top spool stitching always looks better than the bobbin stitching.
When you have finished, press your fabric from both sides. This will meld the stitches to the fabric and create a smooth seam.
Variation 3 - How to Sew a Flat Felled Seam Allowance by Hand
Any of the regular or variations of the flat felled seam can be sewn using hand stitches. It is, however, better used on the mock seam where the seam allowance is on the inside. That way your hand stitches will hold tight and prevent fraying but will not be visible.
For the main seam, the strongest hand stitch is the backstitch. Because the top of the backstitching looks better, plan ahead and stitch on the side that will be visible once the seam is folded and tucked.
When sewing the folded edge, use a whip stitch or blind stitch so the stitching isn't visible on the outside. All you will see is the tiny pinpricks of stitching which will be invisible if you use a matching thread.
Alternatives to a Flat Felled Seam
While slightly different in the look and construction, topstitching, French seams, and edge stitching can also be used to strengthen seams and add a decorative edge.
More Types of Seams:
Flat Felled Seam vs Topstitch
Topstitching is mainly decorative and does not always encase the seams like flat-felled seams. Rather than joining pieces of fabric flat, topstitch is often used on the edge of 2 pieces of fabric sewn together and then turned the right way out. It can also be used on pocket edges and may be done in 1 or 2 rows. When done in 2 rows, it looks very similar to a flat felled seam on the outside.
Flat Felled Seam vs French Seam
French seams will encase the edges but there is no stitching visible on the outside. It is also a durable seam and is often used on sheer fabrics and pillowcases. Like the flat fell seam, it is best for straight seams with little or no curve. You can also use a mock French seam for faster results.
Flat Felled Seam vs Edge Stitch
Edgestitch has a decorative row of stitching on the outside like flat-felled seams but has a raw or serged seam underneath. Because you don't need to hide the raw edges, it can be used on thicker fabrics. Often there will only be one row of stitching instead of 2.
Flat Felled Seam - In Conclusion
Run your fingers along the completed article and see what a smooth finish you have on the inside and a tough edge to the outside. This is a rugged, but smart seam, and a winner for sports and outdoor wear!
Flat Felled Seams
- Sewing Basics
- Place your fabric pieces with wrong sides together and stitch along the normal seam line.
- Press the seam open.
- Trim one side of the seam to a width of ⅛ inch (3mm).
- Press the wider seam allowance (untrimmed) edge over by ¼ inch (6mm).
- Fold the wider, pressed edge over to encase the trimmed edge.
- Stitch along the open edge of the seam 1/16 (1.5mm) to ⅛ inch (3mm) from the edge with an edge stitch foot or all purpose foot. Press.