Carhartt Men's Relaxed Fit Straight Leg 5-Pocket Jean

Are these made with stretch fabric or are they 100% cotton?

These are crafted from 100% cotton denim. Unlike the "Rugged Flex" versions, these offer a traditional, rigid feel that many workers prefer for their classic durability and structural integrity over a long work day.

Are these heavy enough for construction work?

Yes, they use a 13-ounce midweight denim. While not as heavy as ultra-thick canvas, they are significantly more durable than typical casual, store-bought jeans and are specifically built to withstand the daily abrasion and wear found on professional jobsites.