Thatching Process

Thatching is the craft of building a roof covering from dry plant stems laid in thick, steeply pitched layers. It is practised across the world, using water reed, cereal straw, sedge, heather, palm leaves and grasses. In England, where the craft is well documented, three main materials are used: water reed, combed wheat reed and long straw. Each has its own preparation, fixing and dressing methods, and regional traditions remain strong.

Preparing the material

• Water reed is used in bunches with little further preparation.
• Combed wheat reed is wheat straw passed through a comber that removes the grain and leaf, leaving the butts aligned; it is tied into bundles.
• Long straw is threshed but not combed, then yealmed on the ground: wetted, straightened and tidied into compact layers called yealms, level at both ends.

Fixing

For a new water reed roof, bunches are fixed directly to the rafters or battens starting at the eaves, butts outward. Each course is held down by horizontal sways (rods of steel, hazel or willow) secured to the rafters, and the reed is beaten into shape with a legget, a wooden tool with a ridged face. Combed wheat reed is laid and dressed in a similar way.

Long straw is usually applied as a new coat over an existing base coat. The thatcher removes old weathered material back to sound thatch, then fixes the new yealms with twisted, pointed hazel spars. Hazel rods called liggers are fixed across the eaves and gables, and the roof is often covered with wire netting against birds and rodents.

Ridges

The ridge takes the most weather and is replaced more often than the main coat, on average every 10 to 15 years according to Building Conservation guidance. Ridges are usually made from the same material as the main coat, except that water reed roofs are commonly ridged with sedge. The two main ridge types are the wrap-over and the butt-up, and either may be finished flush with the main coat or block-cut and raised, often with decorative patterns of liggers and spars.

Durability

Water reed is the most durable of the English materials; steep Norfolk reed roofs in East Anglia last about 50 to 60 years on average, and some longer. Life for all thatch depends heavily on pitch, exposure, material quality and workmanship. Fire safety measures and regular maintenance are important parts of owning a thatched roof.