How Thatching Works
This traditional – and now very pricey – craft requires a host of speciality tools and techniques.
Thatching is the craft of building a roof with a variety of dry vegetation, ranging from wheat and water reed through to long straw and heather. The basic principle is to layer the thatch material in such a way that rainwater is shed away from the inner roof and off the side of the building, providing a waterproof barrier much the same as that granted by typical slate/tile-based roofs.
Any thatching operation starts with the preparation of the thatching material, with straws/reeds bundled together into a loose sheaf. The sheaf is then leveled off by first knocking it against the ground to force all strands to descend to the bottom, then secondly removing any remaining anomalies, and finally shearing off the bottom inch. This last step ensures that the sheaf has a neat, uniform finish. Once the sheaves (many are required) have been prepared, they can then be positioned on the roof.
The layering of the thatch begins at the bottom of the roof, where it is secured to the framework -or a turf substrate (foundation) running over the framework – with wooden or metal rods called sways. Once this base is in place, layering of the thatch begins proper, with hazel rods, referred to as spars, used to peg sheaves into position up the roof. The positioning of the spars and layering of the thatch ultimately determines the quality of waterproofing and the roof’s life span.
The type of thatching material varies in both price and longevity too, with straw roofs typically lasting between 20 and 30 years, and reed lasting 30-60 dependent on type. Long straw is cut in the field with a binder and then threshed in a drum, and when applied to a house, typically requires a thickness of 40 centimetres (16 inches) to be effective. Reeds, on the other hand, are more robust and so are layered onto a building with a thickness of around 30 centimetres (12 inches).
Today, however, thatched properties are typically far more expensive than slate-based equivalents due to the great drop in professional thatchers available, the limited quantities of cheap thatching materials and the higher-than-average maintenance costs.