Seam types are the place where two pieces of fabric are joined by application of a series of stitches or stitch types with a defined geometry. Over the years there are a number of different types of seams that have been developed to do different jobs. Many have largely been superseded by the development of machine stitches that finish as you sew them, and by the development of the over locker (or serger in some parts of the world), it is useful to know some of the basic seams types and finishes.
Common Types of Seams
Superimposed Seam (SS): The superimposed seam is achieved by two or more separate pieces of together. This is the one of the most common method of seaming. The most basic superimposed seam is made when one ply of fabric is stacked upon another with thread stitching through all plies of fabric. Variations are plain seam, French seams and Double machine seam.
Lapped Seam (LS): Lapped seam is made with two or more pieces of fabric overlapping each other. LS commonly, but not always, have one ply of fabric fold under itself for a finished edge. Lapped seams are common when sewing side seams on jeans and dress shirts. This class of seaming has the largest number of variations.
Bound Seams (BS): Bound seam is made to finish and edge of a garment. A common example of this would be a neckline of a Crew T. A bound seam is one piece of fabric encompassing the raw edge of another piece of fabric. There are many variations of a bound seam.
Flat Seam (FS): A flat seam is constructed by having two pieces of fabric meet precisely at their edges. A cover stitch is used to sew the two pieces of fabric together. This stitch has multiple needles and creates a stitch perpendicular to the seam line. This creates a flat seam. Plain seam is a flat seam.
Edge Finished Seams (EF): This seam is used to prevent the edges of the fabric from rolling or curling. Primarily used for knit fabrics and is suitable for straight or curved seams and edges.
Ornamental Seam (OS): this seam is made using machines with zigzag capability. It is used on a plain seam on woven or knit fabric. The zigzag stitch length (coverage) must be adjusted to accommodate and prevent fabric from ravelling. The more the fabric ravels, the closer together the stitches need to be (tighter or shorter stitch length).
Seam - best practices
- Smooth and even in appearance on the inside and outside. (Properly adjust machine tension, stitch length, and presser foot pressure to suit the fabric and thread. Fabric should not pucker)
- Even in width through out
- Pressed open or closed according to the type of seam and how it is used in the construction process
- When stitched with thread, the thread should be appropriate to the fabric type and fibre content. Thread colour should match or slightly darkest.
- Neat and smooth in appearance, without added bulk.
- Free from ravelling, stretching, rolling and curling.
- Should not be visible from right side of garment.
Factors affecting appearance of Seam
The technique and skill of the sewing machine operators also govern the appearance of sewn seams. Some of the factors that will adversely affect the appearance of a seam.
|Stitch Defects||Seam Appearance Defect|
|Poorly formed stitches||Twists|
|Crooked stitches||Run-off (raised seams)|
|Skipped stitches||Raw edges exposed (felled seams)|