Sewing Techniques

Seam Finishes

When a seam is stitched you take a seam allowance – thus the seam is not stitched at the very edge of the fabric. This allowance is then finished or neatened.

Seam Allowances
The area between seam stitching and raw edge is the seam allowance. This allowance helps stop stitching fall off the edge of the fabric, preventing seams falling apart with wear and it can be used to accommodate slight adjustments to fit. Commercial patterns include a seam allowance in the pattern pieces, the amount of which depends on the type of project but a general rule of thumb is 15 mm (5/8”) for garments and 6 – 10 mm (1/4 – 3/8”) for craft projects.

Failure to neaten seams properly can result in seams pulling apart where fabrics fray or excessive bulk and ridges in seamed areas.

Easy neatening methods

Overcasting/overstitching/zigzagging – prevent fabrics fraying by stitching a zigzag or overcast stitch down the seam allowances. On lightweight fabrics both seam allowances can be stitched together as one, on medium or heavyweight fabrics, press seams open and stitch down both sides. If an overlocker is available, neaten seams with 3-thread overlock stitch prior to sewing seams.

Zigzag stitch - Stitch down the centre of the seam allowance and then trim close to stitching.

Overcast stitch – if your sewing machine has an overcast or overstitch built-in, use it to neaten seams. Stitch so the right swing of the stitch is just on the very edge of the fabric.

HANDY HINT: On fabrics that fray easily, neaten seam allowances on all pieces with a small zigzag stitch before stitching seams. Press before joining seams to ensure a flat even surface.

Hong Kong style (bound) – this finish is more time-consuming but is ideal when the inside of the garment might show as the seam allowances are neatly bound. The binding used can be bias cut strips of lining or organza or a special seam binding tape that is sheer and very lightweight.

Seam binding tape – made from fine net like nylon, when gently pulled this specialist tape folds in two making it very easy to wrap around the raw edge of the seam allowance. Holding the end, gently pull on the tape to see which way it naturally folds. Pin the end around the seam allowance raw edge to hold in place. Then whilst gently pulling on the tape so that it wraps around the fabric edge, machine stitch in place approx 3 mm (1/8”) from the edge.

Bias strips – cut the strips 15 mm (5/8”) wide. Pin strip, to RIGHT side of seam allowance, with raw edges matching. Stitch 3 mm (1/8”) from raw edge. Press, then wrap the strip around to wrong side of seam. Stitch again from RIGHT, stitching ‘in the ditch’ (stitching along the previous seaming by gently pulling the two fabrics apart to form the ‘ditch’)

Clip and Notch and Grade Seam Allowances
When a seam allowance is encased within collars, cuffs, facings, waistbands or hem allowances the raw edges need not be neatened but they do need trimming to reduce unwanted bulk within the seamed area.

Grading seams – this term describes the method of reducing each of the seam allowances to different widths to prevent a bulky ridge forming. For instance when applying collars, there will be a seam allowance on the garment neck edge, as well as the under collar piece and upper collar piece. To eliminate too much bulk, cut the seam allowance that lies closest to the outside of the garment to 6 mm (1/4”) and the under seam allowance to a scant 3mm (1/8”).

HANDY HINT: Use smaller, sharp scissors held at an angle to cut the separate layers of seam allowance.

Clipping and notching – Not to be mistaken with Notches on pattern tissue, Clipping and Notching of seam allowances is done to reduce bulk and allow fabric to spread at curved sections, so the fabric will lay flat when turned through.

Inner curves – make little snips into the seam allowance
Outer curves – cut little wedge shapes out of the seam allowance to allow fabric to spread when turned through.

HANDY HINT: When stitching a curved section to a straight section, stay stitch the curved piece just within seam allowance (straight regular stitching) and then clip into seam allowance to help spread the fabric to fit accurately