How to sew a flat-felled seam

The strong, flat seam you see on jeans and shirts: one allowance is trimmed, the other folded over it and stitched down, so there are no raw edges.

Pinny's tip
Practise on a scrap first and decide which side you want the visible double stitching on.

What you'll need

• Medium or heavy woven: denim, drill, shirting.
• Jeans needle for denim: heavier needle for the layers.
• Topstitching thread (optional): for a jeans look.

Step by step

1. Sew the seam at the full allowance (wrong sides together for stitching on the outside, right sides together for stitching inside).
2. Press both allowances to one side.
3. Trim one seam allowance narrower than the other so the wider one can wrap over it.
4. Fold the wider allowance over the trimmed one, tucking its raw edge under. Press.
5. Press the folded allowance flat against the garment and pin.
6. Edgestitch close to the fold through all layers.

Common mistakes

• Trimming the wrong allowance. Trim the one that ends up underneath.
• Skipping the pressing. The fold is hard to keep even without it.
• Wobbly edgestitching. Use an edgestitch foot or move the needle position.

Watch it done

• Easy How To Sew a TRUE Flat Felled Seam Sewing Tutorial 3 Versions- Step by Step Sewing Tutorial by Notches Sewing on YouTube. Opens on YouTube; the video belongs to its creator.
• How to Sew a Flat Felled Seam aka The Strongest Seam by MadamSew on YouTube. Opens on YouTube; the video belongs to its creator.
• How to Sew a Flat Felled Seam | Sewing Machine by Howcast on YouTube. Opens on YouTube; the video belongs to its creator.

Sources

All checked November 1, 2026. We read these; we did not test the products ourselves.

1. YouTube: Easy How To Sew a TRUE Flat Felled Seam Sewing Tutorial 3 Versions- Step by Step Sewing Tutorial (Notches Sewing)
2. YouTube: How to Sew a Flat Felled Seam aka The Strongest Seam (MadamSew)
3. YouTube: How to Sew a Flat Felled Seam | Sewing Machine (Howcast)