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Thatched Roof

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Thatching is the construction of a roof with dry vegetation such as straw, water reed, sedge, rushes, or heather, and then layering the plant material to shed water away from the inner roof. It is an old roofing method and has been used in both tropical and temperate climates. Thatching materials range from plains grasses to waterproof leaves found in equatorial regions. It is the most common roofing material in the world, because the materials are readily available and considered sustainable. It is not as flammable as often perceived, and is said to burn slowly, like a closed book. Because thatch is lighter, less timber is required in the roof that supports it, and is a versatile for covering irregular roof structures.

Thatching is employed by builders in developing countries, usually with low-cost, local vegetation, and is also popular in Europe (Germany, The Netherlands, Denmark, Belgium, Ireland, Switzerland, and especially in the United Kingdom); Asia (Japan, Korea); and Africa (Lesotho). Older communities also used thatching, including the Maya and Inca civilizations in South America, Mexico, and the Seminole Native American tribes in Florida in the United States.

Good quality straw thatch can last for more than 50 years when applied properly. In the UK, traditionally, a new layer of straw was simply applied over the weathered surface, and this ‘spar coating’ tradition has created accumulations of thatch over 7’ (2.1 m) thick on very old buildings. The straw is bundled into 'yelms' before it is taken up to the roof and then is attached using staples, known as 'spars', made from twisted hazel sticks. More than 250 roofs in Southern England have base coats of thatch that were applied more than 500 years ago, providing direct evidence of the types of materials that were used for thatching in the medieval period. Almost all of these roofs are thatched with wheat, rye, or a 'maslin' mixture of both - providing not only thatching but grain for food.

Documents

Insulating Thatched Roofs in the UK 2012 (1,407 kb)