Not buildable in Clothix. The cut-and-sew parts are within reach of a knit engine; the elastics and the bra components are a separate trade. Where this sits.
The elastics
An underwear manufacturer will ask about these before asking about the fabric, and that ordering tells you where the fit lives.
Three values per elastic, and the third is the one that gets left off.
- Width, finished. A 30 mm waistband and a 40 mm one are different products.
- Type — knitted, woven or braided. Knitted is soft and recovers moderately; woven is firm; braided narrows when stretched, which makes it wrong for a waistband and right for a drawcord.
- Tension ratio. The elastic is cut shorter than the opening and stretched on. The ratio is a spec value, usually 80 to 90 % for a waistband and 70 to 85 % for a leg opening, and it's the number that decides whether the garment grips or digs.
Same logic as a rib neck band, with higher stakes: a neck that's 5 % out looks slightly wrong, a waistband that's 5 % out is unwearable.
The gusset
A separate piece, usually a lighter or different fabric, caught into the front and back panels. It's specced as its own pattern piece with its own composition, and it's often the one part of the garment where a natural fibre is required for reasons that have nothing to do with design.
Two constructions: a single-layer gusset caught in the seams, or a double-layer one that encloses its own edges. The second is cleaner and slightly more expensive.
Fabric
Light jersey or a fine rib, 120 to 180 g/m², almost always with elastane. Modal and micromodal blends are common for hand-feel; cotton for the gusset; polyamide-elastane for anything performance-positioned.
Elastane content matters more than weight. A 150 g/m² jersey with 5 % elastane and one with none are different garments — the first fits, the second bags at the seat after a wash.
Bras are a different trade
Worth being clear about, because they get lumped in with underwear and shouldn't be.
A bra has components no other garment has: cups (moulded or cut-and-sewn from two or three pieces), wire channelling, a bridge, a back band under real tension, hook-and-eye tape, rings and sliders, and strap elastic with its own recovery spec. Fit runs on two independent axes — band and cup — and grading them is a specialist discipline, not a rule set.
Tolerances are also tighter than anywhere else on this site. A centimetre on a t-shirt chest is nothing; a centimetre on a bra band is a size.
If you're building a bra, you want a lingerie factory and a lingerie pattern maker, and no general garment tool is going to be the answer. Finding that specific kind of factory is the real first problem.
What a tech pack adds
Beyond a knit top: every elastic with its width, type, supplier and tension ratio; the gusset as its own piece with its own composition; stitch types per seam (coverstitch and zigzag do different jobs on elastic); and for a bra, the full component list — cup type, wire size and channelling, band elastic, hook-and-eye, rings, sliders, strap elastic.
Light jersey and elastane · recovery and tension ratios · specialist factories · all categories · what we cover