How to Sew a Flat-Felled Seam

Up next in our series on Seam Finishes is a tutorial on flat-felled seams. This is a really useful seam finish to have in your sewing skill-set, as it pops up surprisingly frequently in many of our most-worn garments.

So what is a flat-felled seam?

A flat-felled seam is basically an overlapping seam that’s sewn flat.

It’s used frequently in workwear because it’s extremely durable and sturdy, in addition to providing a neat finish. Because of the hidden seam allowances and the extra row of stitching, this seam finish adds strength to a seam and is therefore, often used in areas that will get a lot of wear and tear. If you take a look at a pair of jeans, you will probably find flat-felled seams are used to finish the inside leg.

Why choose a flat-felled seam?

  1. You are making a hard wearing garment
    If you’re making a garment that will likely have a hard life then consider flat-felled to give the seams their very best chance!
  2. Your fabric frays a lot!
    If the fabric you are working with is fraying a lot, flat-felled seams are a good choice of seam finish. As the seam is stitched twice and the raw edge is enclosed, the seam is given extra strength and the fraying fabric won’t become a problem.
  3. Your garment suits a lot of topstitching
    Flat-felled seams add an attractive row of topstitching while finishing the seams – two for one! Saves time and energy!
  4. You don’t have an overlocker
    These seams are a brilliant way to finish a seam on your standard sewing machine. Only a straight stitch is needed to achieve a strong and beautifully finished seam.
  5. You are making clothes to last
    A lot of environmentally-friendly garments are made using stronger sewing techniques to add durability to a garment; if you are sewing for eco-conscious reasons then this is a technique you need to know!

How do I sew it?

There are several ways to achieve the flat-felled look, and there is even a specialty foot available for many sewing machines, sometimes known as a ‘felling foot,’ or a ‘lap seam foot.’ However, for this tutorial we are going to assume you don’t have one of these specialty feet.

To construct a flat felled seam using this tutorial you will need:

Pins, scissors (duckbilled are useful but not essential), sewing machine and an iron.

Step 1.
Sew your fabrics together. If you want two rows of stitching on the outside of the garment, then stitch them wrong sides together. In this example we want two rows of stitching on the inside of the garment so we have stitched them right sides together using a 1.5cm seam allowance.

Step 2.
Decide which side of the seam you want to have your row of topstitching visible on the outside. If you trim the layer on the right then your seam will also fold over to the right and the topstitching will (you guessed it!) also be on the right. Same goes if you choose to trim the left. It doesn’t matter in most cases, it would likely only matter if you want topstitching for aesthetic purposes.

Step 3.
Once you have decided where you want your visible topstitching to be, trim that side down to 0.5mm.

Step 4.
Fold the wider seam allowance to meet the edge of the narrow seam allowance and press.

Step 5.
Press both seam allowances over and down, so that both raw edges are concealed.

Step 6.
Pin the seam closed and edgestitch 1mm away from the edge.

Now you know how to sew a flat-felled seam, go forth and make strong garments!