What Is Flannel Fabric? Brushed Cotton, Wool Flannel, and the Nap
October 29, 2026
Flannel is not a pattern and not a weave on its own. It is a fabric, usually plain weave or twill, that has been brushed on one or both sides to raise a soft nap of loose fibers. That nap traps air, which is why flannel feels warm without being heavy. Plaid flannel shirts are just the most famous use. Solid gray wool flannel trousers are the same family.
The brushing is the fabric
After weaving, the cloth passes over fine metal brushes that pull fiber ends to the surface. One brushing gives a light nap for shirting. Repeated brushing gives the thick, almost fuzzy surface of flannel sheets and pajamas.
The nap explains the softness and also the pilling. Those raised fibers are loose by design, and they mat and pill where fabric rubs, at elbows, cuffs, and under seat belts. Good flannel pills less because its base yarns are longer and stronger.
Cotton flannel versus wool flannel
Cotton flannel is washable, soft immediately, and used for shirts, sheets, and baby blankets. It loses nap over many hot washes and gets thinner and smoother with age.
Wool flannel, common in trousers and suiting, is warmer for its weight, resists wrinkles better, and keeps its surface longer. It usually needs gentle washing or dry cleaning, and it costs noticeably more per yard.
Weight tells you the job
Shirting flannel runs about 5 to 7 ounces per square yard. Sheeting and heavy work flannel can go well above that. If a shirt feels thin and prints its pattern sharply with no visible nap, it may be a flannel print on plain cotton rather than brushed flannel.
Rub the surface between finger and thumb. Real brushed flannel feels soft in both directions and looks slightly fuzzy under light. A print feels flat.
Washing without killing the nap
Wash cotton flannel in warm or cold water, turn shirts inside out, and avoid high heat drying, which hardens the surface over time. Wool flannel trousers should be rested between wears and cleaned gently.
Fabric softener coats the nap and makes it feel slick rather than soft, and it reduces absorbency in flannel sheets and towels. Skip it for this fabric.
A quick word on flannel shirts sold very cheaply. The pattern is printed, the nap is minimal, and after three washes the shirt feels like any thin cotton shirt, because that is what it has become. If the price seems too good for brushed cotton, it usually is. Buy one honest flannel shirt instead of three printed imitations and you will be warmer for years.
Keep reading on this site: What is gabardine fabric, What is velveteen fabric, What is seersucker fabric. Each of those pieces connects to the ideas above and gives more detail on the parts this guide could only summarize.
Frequently asked questions
Is flannel always plaid?
No. Plaid is a pattern. Flannel is a brushed finish, and it comes in solid colors, including classic gray wool flannel for trousers.
Why does my flannel shirt pill?
The raised nap fibers are loose and rub together. Longer staple yarns pill less, and washing inside out on gentle helps.
Is flannel warm enough for winter bedding?
Yes for most sleepers. Cotton flannel sheets trap air in the nap and feel warm on contact, unlike smooth percale which feels cool.
Can I iron flannel?
Yes, on medium, preferably from the back or with a press cloth, so you do not flatten the nap completely.