What is Thatching?
Thatching is the craft of building a roof with dry vegetation such as straw, water reed, sedge (Cladium mariscus), rushes, or heather, layering the vegetation so as to shed water away from the inner roof. It is a very old traditional roofing method and has been used in both tropical and temperate climates. Thatch is still employed by builders in developing countries, usually with low-cost, local vegetation. By contrast in some developed countries it is now the choice of affluent people who desire a rustic look for their home, would like a more ecologically friendly roof, or who have purchased an originally thatched abode.
How The Thatch Works
Thatching is a highly-skilled job and a good thatcher will lay the material so that water runs quickly, evenly and efficiently off the roof and is carefully directed away from any points where a leak might occur, particularly junctions with chimney stacks or dormers. The steeper the pitch of the roof, the faster rainwater runs down the stems of the thatching material and off the roof. Damp does not penetrate far into the top layer of a thatched roof in good condition; most of the thatch remains dry all the time. Unlike other roofing materials, there is no need for guttering because thatch has deep projecting eaves. This ensures that water is shed from the roof well away from the base of the walls, avoiding splash damage.
Thatched roofs provide excellent insulation, keeping the house warm in winter and cool in summer. As an organic material thatch decays and, over time, the stems of the thatching material degrade and rot back. The ridge of a thatched roof is particularly vulnerable and will need replacing at intervals of anything between six to twelve years. The rest of the thatch will last much longer. When the fixings of thatch (which may be horizontal lengths of split wood called sways, or today, sometimes wire), which are covered by courses of thatch, begin to show, it is an obvious sign that it is time to carry out some patching, or re-thatching. Orientation and local conditions mean that one pitch of the roof may need attention before the other.
Care of Thatch