Knit Fabrics

Everything I've written about on this site so far assumes woven fabric — two sets of threads crossing at right angles, held in place by friction and the weave itself. Knits are built completely differently: a single continuous thread (or a small number of them) looped through itself repeatedly, the way hand-knitting works, just done by machine at industrial speed. That loop structure is what gives knit fabric its stretch — the loops can flex and recover in a way crossed woven threads simply can't.

This changes the sewing rules more than beginners usually expect going in. A woven pattern generally needs darts and set-in details to fit a curved body; a knit pattern often skips them entirely, relying on the fabric's own stretch to do that shaping instead — which is why so many T-shirt and legging patterns look almost shapeless flat on the paper. Regular seams also behave differently: a straight-stitched seam has no give, so it can pop under stretch, which is the whole reason sergers and specific stretch stitches exist.

Not all knits behave alike, either — a stable, dense knit like ponte behaves almost like a woven for cutting and handling purposes, while something like a loose rib knit stretches and distorts if you so much as look at it wrong on the cutting table. I always check a fabric's stretch percentage against what the pattern calls for before cutting; sewing a garment in a knit with less stretch than the pattern was drafted for is a fast way to end up with something that doesn't fit.