Chimneys

Where a chimney projects wholly or partially through a roof, the junction with the thatching has to be made with especial care to prevent leaks.

Historically, the junction between the chimney shaft and the thatch was probably protected by a lime mortar fillet. Today thatchers may choose to use a cement fillet.

As the thatch decays and its surface drops, a gap will open up between it and the fillet, which should be checked every time the ridge is re-thatched and replaced if necessary. A modern alternative to the lime mortar or cement fillet is lead flashing.

This can be dressed up into the chimney shaft. Lead was an expensive material, not locally produced. It is unlikely to have been used on thatched buildings before about 1900, but is readily available and commonly used today, although it can be difficult to dress lead into a masonry chimney shaft with irregular joints. For fire prevention reasons it is vital that chimney shafts are kept in a good state of repair.