How to Sew a Split Seam

A split seam is an incredibly versatile detail that can be used across most garments in lots of ways. They can alter the silhouette, changing a regular pair of trousers into flares, add movement to a dress or skirt and add interest to a top or jumper. In this tutorial we are going to walk you through the steps required to make a standard split seam hem and a French seamed version. 

Please ensure that you read through this guide before cutting out your fabric


1. First you need to decide how long you would like the split to be. Once you have determined this you will need to add extra width to the seam allowance of the split opening so you will have enough fabric to turn back and finish the slit opening nicely. The easiest way to do this is by adding on a seam extension to your pattern before you cut it with a little rectangle of paper. 

For this example I would like the slit to have a length of 5cm (2”) opening, so cut out a rectangle measuring:

5cm (2") + 2.5cm (1”) + 2.5cm (1”) = 10cm (4”) 

(The length of the split + depth of the hem + extra for finishing at the top = length of rectangle

The width of the rectangle will be at it’s thinnest, the same width as the seam allowance but can be wider depending on the thickness of your fabric. For this example I have used a width of 1.5cm (5/8”).

2. Line up and tape the rectangle in line with the hem, butting the edges together.

3. Make a small mark one inch below the top of the rectangle on the seam allowance

4. Cut out your fabric (including the rectangle extension) and transfer the mark onto the fabric

5. Place right sides together, pin the seam down to the mark and sew

6. At the top of the rectangle extension cut a horizontal line to meet the stitches

7. Press both seams open.

8. Finish the edges of the slit by either overlocking/zigzag or fold under the edges and sew

 9. Your split is complete!

A variation on this which is a good option for tops, is a split level hem, where you can cut the back of the garment longer and apply the same principles as above.




French seam version

 1. As per version 1, firstly you will need to decide how long you would like the split to be and follow instructions above, however for this example we are going to reduce the width of the rectangle so it is 1cm (3/8”). Attach to the bottom of the pattern piece and cut out your fabric.

2. Place wrong sides of the fabric together so the edges match and mark a line across from the top of the rectangle to the seam allowance. Make a second mark 0.5cm (1/4") above the chalk line.

3. For this example the seam allowance is 1.5cm (5/8”), so first you will need to sew 0.5cm (1/4”) seam allowance from the edge down to the 0.5cm (1/4") mark and pivot the needle to sew diagonally to the corner of the other mark. Ensure that you sew forwards and backwards a few times to strengthen this point

4. Next, you will need to cut along the horizontal line up to (but not into), the stitching

5. Trim the fabric diagonally, close to the corner

6. Turn the fabric so that the wrong side is facing out and press. Press the seam

7. Ensure that the corner is pushed out, using a pair of scissors or something pointed if necessary

8. Using a 1cm (3/8”) seam allowance, sew straight down, past the corner and 0.5cm (1/4”) below it

9. Open the bottom two seams and press

10. To finish the edges of the split fold the top corners down at a right angle and tuck under the long sides and press

11. Edge stitch around the split. The split can be left like this or to strengthen further, sew across the right angles to form a small triangle.