Definition: A facing is the area of a garment or sewn item that turns to the inside, giving a finished appearance to what would otherwise just be a raw edge of fabric. The facing is usually interfaced to add shape to the edge of the fabric and help the garment maintain the desired shape. Understanding the different types of interfacing and how they work is an important aspect to sewing facings. In some cases another layer of the fabric itself is used as interfacing.
Common facing areas on garments are necklines (without a collar), armholes in sleeveless garments and waistband-less waistlines. Peek a boo type garment openings usually also have a facing.
When you are following a pattern the pattern directions are your first source of assembly instructions. In most cases the facing pieces are assembled or sewn together and then attached to the garment to finish the raw edge of the garment.
The inside edge of the facing, the edge that is not attached to the garment, is finished in a seam finish type of method to prevent the facing from fraying. In many cases the edge of the facing is sewn with a single line of stitching to help the facing hold its shape and then the raw edge is trimmed with pinking shears to prevent fraying. This type of edge treatment is done so the facing does not have a "bulging" edge that might be seen through the garment. the facing should have a seamless transition from the outside of the garment.
A facing should always stay inside the garment. When attaching a facing, the pattern provides dots, notches and seams that should line up with the same parts on the facing. Seams must intersect properly for the facing to lay properly. Once a facing is attached, grading the seam and under stitching the facing helps the facing stay turned inside the garment and provide a professional finish to the way your facing looks from the outside of the garment.
Many store bought garments have finished and turned edges instead of a facing. Many newer patterns have bias tape edging inside the garment as a facing or replacing the facings rather than full fabric facings. This changes how the garment edge lays and forces a line of stitching to be visible on the outside of the garment in order for the bias tape to be stitched down in to place. The garment, and the desired finished appearance, dictates if a full facing is needed or a bias tape facing is sufficient.
A facing pattern piece is small and a commonly lost pattern piece. Preserving your pattern and taking care to refold and package the pattern when you are dine is important if you want to use the pattern again. Buying a whole new pattern is expensive and may not even be possible if the pattern is discontinued.
The raw edge of a facing is finished with a seam finish to prevent fraying and help the facing hold its shape. Avoid heavy turned edges on the edge of the facing that will show through the garment.
Most facings will require you to tack or slip stitch the facing to a seam allowance or inside part of the garment to assist the facing in staying inside the garment. This stitching is not sewn to the main boy but only to things like seam allowances so the "tacking" is not visible on the outside of the garment.