Thatch, from thack, originally referred to any form of roof covering but is usually taken to mean a traditional form of roofing which uses reeds, straw or heather. Its use in England was widespread but its flammability caused it to be banned as a roofing material for new buildings in many towns from the medieval period onwards, and especially in London after the Great Fire. Thatch is therefore an essentially rural building material and one which depends upon traditional methods of harvesting. From the late 18th century, the introduction of mechanical methods of threshing made the straw less suitable for use in thatching. In areas where threshing machines were widely used and other roofing materials were available, such as stone slates or earthenware tiles, thatching was soon replaced. In other areas of the country, however, thatching has continued in use into the present. Thousands of examples survive, in all parts of England, but because thatch requires renewal few examples are likely to be more than a hundred years old. Thatch has always enjoyed popularity for its picturesqueGlossary Term qualities, and conservation of historic buildings has encouraged the continued use of traditional forms of thatching into the present century.

Raw materials for thatching were often readily available on or near the building site but in parts of East Anglia special beds were formed for cultivating reeds specifically for this purpose. The benefit of thatching as a roofing material is its lack of weight and simpler forms of wall construction, such as mud and chalk, could therefore support it. Even in areas where brick was available, roofing might be of thatch rather than tiles; often because suitable reeds or wheat stalks could be cut from the same clay soil from which the bricks would be made.

• Read about different thatching materials and techniques.