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 Many have largely been superseded by the development of machine stitches that finish as you sew them, and by the development of the overlocker (or serger in some parts of the world), it is useful to know some of the basic seams types and finishes.
There are simple commercial patterns for making up a variety of garments in order to learn sewing techniques. Following are some of the basic sewing techniques.
Common Types of Seams
Superimposed Seam (SS)
The superimposed seam is achieved by two or more separate pieces of together. This is one of the most common methods 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 a plain seam, French seams, and Double machine seam.
Lapped Seam (LS)
The 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)
The 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)
This is the most commonly used seam. It is pressed open and flat and is usually neatened using different techniques. If the fabric is knitted a stretch stitch is used that will allow the stitched seam to stretch as much as the fabric needs to in use.
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.
A flat seam is the basic seam joining the edges of two pieces of fabric. It is used on normal-weight fabrics where there is no special strain on the seam. In most cases, a plain straight stitch is used to stitch the seam.
French Seam
The French Seam is particularly useful when a fabric is delicate and prone to fraying, such as chiffon. Raw edges are concealed inside a double-stitched seam.
A French Seam is generally used for fine fabrics or for those which fray easily. It is a seam within a seam and when finished should be about 5 mm or less in width.
Flat Fell Seam
This gives strength and decoration to a product. Denim jeans are made strong by this technique. A double line of stitching is often used in a contrasting coloured thread.
A flat fell seam is a very strong neat seam which withstands heavy wear and frequent washing provides a neat finish with either side of the fabric. You can choose which side of the seam you use on the right side of the fabric.
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).
Neatening Seams
Pinking
Pinking shears are used to cut a zigzag edge along a woven fabric edge. This helps to prevent the woven threads from unravelling, making a flat seam.
Overlocking and Zigzag Stitching
An overlocker with three or more threads is used simultaneously to trim, stitch and neaten the seam. This is an inexpensive way to neaten the seam.
Bias Binding
When it is essential to cover the fabric edge, bias binding can be folded in half and stitched along both edges of the flat seam. Seams in more expensive fashion clothing often feature bound edges. This technique can also be a cheaper alternative to making a fully lined garment.
In clothing that has special high-performance features, the seams are taped, for example in a wetsuit. The water movement through the seam is restricted by the tape and the seams are also strengthened.
Shaping Techniques
Darts
Darts are used to create 3D shaping in flat fabric in order to fit the figure. A dar in the fabric is useful at the waist or bust where a pointed fold is made to shape the garment panel. Darts are stitched along the fold line and pressed down, towards the side seam.
Pleating
A pleat is a fold in the fabric, which can be pressed in order to keep its edge or stitched down along a section of the fold. Skirts are often pleated to allow for ease of movement at the knee. On some skirt-front panels, very small pleats called pintucks are stitched down to give a decorative effect.
Gathering
Fabric width can be reduced by gathering to give a wavy shaping to curtains or garment waistlines or sleeves. Fabric volume is controlled by two lines of long stitches at the top edge of the fabric. The two threads on one side of the fabric are gently pulled taut as the fabric is eased back along the length of the threads. This technique is useful when inserting sleeves; the sleeve top is gathered and the fullness distributed according to the fit around the armhole opening when the majority of the gathering around the shoulder.
To ease in fullness at the top of the sleeve, make a row of machine stitching along the seam line and 6 mm inside seam line between notches, using a long machine-stitches.
Seam – best practices
- Smooth and even in an 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 throughout
- 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 the right side of the garment.
Factors affecting the 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 |
|---|---|
| Loose Stitches | Puckers |
| Poorly formed stitches | Twists |
| Crowded stitches | Plaits |
| Tight stitches | Undulations |
| Crooked stitches | Run-off (raised seams) |
| Skipped stitches | Raw edges exposed (felled seams) |
Methods for Making
There is often a choice of method to use when constructing features such as pockets, tabs, collars, cuffs, and plackets, or when inserting zips or adding a facing. The designer will need to consider fabric type and weight and whether the construction technique is also to be decorative. Interlining may need to be fused to the back of the fabric to strengthen it when constructing collars, packets, pocket opening and flaps.
More complex procedures will take longer to make and the machinists will need more skill. Linings and interlinings will add to the cost, as will larger features that need extra fabric (e.g. gathers or pleats) or complex fastenings.
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