Thatching is the craft of building a roof with dry vegetation such as straw, water reed, sedge (Cladium mariscus), rushes, or heather and layering the vegetation so as to shed water away from the inner roof.
The thatch is applied to the roof by pinning bundles of reed side by side on the roof and fixing a sway or ligger two-thirds up along the bundle. Then opening the string and tying the bundle together. Each bundle then has to be dressed into the other coarses.
It is a very old roofing method and Thatched roofs can be traced back in Ireland for over 9,000 years. The thatched dwellers would use whatever local vegetation was available to them; like water reed, oaten straw, rye straw.
An even earlier form of thatched house was the round houses that were built on a Crannog and these are a good example of an early thatched dwelling in Ireland. The Crannog refers to Small Island which was often man-made. These islands in most cases were fortified and lived on by people with their livestock. The Crannogs (island dwelling) were usually round or oval in shape, constructed from oak poles set in the ground in a circle and the walls were woven with split hazel to make wattle walls. The interior surfaces were built up with any mixture of clay, peat, stone, timber or brush- whatever was available. The roof was them made from ash poles and thatched with water reed.