How to Sew a French Seam
Looking for ways to polish your homemade garments? A finishing seam can make the difference between obviously home-sewn and haute-couture tailored.
The french seam is one of the most elegant and popular of finishing seams — but be prepared to practice because it’s definitely advanced.
A french seam is a finishing seam most often used in custom-made and high-end clothing garments, such as wedding and evening gowns, highly tailored clothing, or interior design items including pillows and bedspreads. The purpose of the seam is to hide to raw edges of the fabric and prevent fraying for a stronger, cleaner, attractive finish.
Because several steps are involved in the creation of a french seam, it can be complex to learn. Do not attempt this seam until you are comfortable sewing (and ironing) a straight seam. Beginners should also avoid practicing this seam on a curved pattern — it is advisable to work with straight lines only until you have successfully completed a few practice runs of this technique.
There are eight general steps involved in a french seam (discussed in detail below). To begin, a regular straight seam is sewn. The seam is pressed open and the seam allowance trimmed. Next, the fabric is folded in half along the seam (with the seam allowance inside). A second seam is sewn, slightly wider than the original seam allowance, enclosing the raw edges inside and leaving a clean and durable inside seam.
What Will I Need?
The following supplies will be needed:
Fabric, fabric scissors, fabric pins, sewing machine (though technically a french seam could be sewn entirely by hand, as they were not that many generations ago), iron, and ironing board.
Note: French seams are often used on garments of silk, satin, and chiffon — some of the most challenging fabrics to sew. It’s helpful to start with scraps of a studier material, such as a non-stretchy cotton weave, while learning this technique.
Step One:
Place fabric pieces with WRONG (i.e. eventual inside of the garment) sides together and pin as necessary. Notice that this preparation is opposite to the preparation for a regular simple straight seam (which would require the fabric to be placed with the right sides together).
Step Two:
Sew a straight seam leaving 1/2 inch seam allowance.
Note: Seam allowances in commercial patterns may need to be adjusted.
Step Three:
Open the fabric and iron the seam down the middle.
Step Four:
Fold both seam allowances to one side and iron.
Step Five:
Trim seam allowance from 1/2 inch to 1/4 inch. Do not trim additionally, as it would weaken the seam.
Step Six:
Fold the fabric along the seam line so that the RIGHT sides of the fabric are together (as would be the preparation for a regular simple straight seam). The seam allowance from the first seam will be inside the fold.
Step Seven:
Sew another seam just over 1/4 inch in width. Be sure this seam is consistently wider than the remainder of the trimmed original seam or the raw edges will not be hidden.
Step Eight:
Press the new seam allowance to one side and iron.
Note: Each garment pattern piece will need to be sewn with french seams individually before assembling the pieces.
Troubleshooting:
-If the seam tends to pucker, be sure to keep a straight line while sewing.
-If there are threads poking through on the right side of the finished seam, either the second seam was too narrow or the first seam allowance was not trimmed enough.
-If unsure of the correct ironing procedure for a particular piece of fabric, consult a fabric handbook.
