Thatch

Thatch is a roofing material made of dry plant stalks, typically water reed, straw, rushes or palm fronds, layered thickly and tied to a roof structure to shed water without cladding or membrane. It has been used for vernacular roofing on every inhabited continent, and its steep pitch, ordinarily forty-five degrees or more, is essential to its water-shedding performance, since a shallow thatched roof holds moisture and rots. Well-maintained water reed thatch can last several decades, and though it has largely been displaced by manufactured roofing in modern construction, it survives as a conservation and heritage material, notably on traditional cottages in England and rural dwellings across Africa and Southeast Asia.