Owners of listed thatched properties have a responsibility and duty of care to protect their precious thatched buildings. “Chocolate box” style thatched houses with multi-layers of historic thatch are unique to the United Kingdom, but it is this very design, coupled with a wood burning stove that has made England the thatch fire capital of the world. Open fires or oil/gas enclosed appliances in properties with thatch are considerably safer than an enclosed stove. The property below had two wood burning stoves as the sole source of heating. The hidden poor condition of both chimneys meant this property was at risk.
Almost all of them are older properties, pre-1960. Listed properties with deep straw thatch are the most at risk. In many such properties ancient chimney construction makes them incompatible with the installation of modern stoves. In some at risk properties there is no safe way to install and use a wood burning stove.
Since 2008 there have been at least 450 serious fires in properties with a thatched roof; this is equivalent to the devastation of one family per week losing their home, and the irretrievable destruction of heritage. Media reports of a roof suddenly bursting into a sheet of flame are an accurate account of what happens when a fire deep inside thatch is fed by oxygen from the surface, which causes the fire to flash over the roof. The thatch may have been burning for many hours before the fire is detected. The majority of thatch fires occur from September to Easter; particularly during cold snaps in bank holiday periods. Fires are associated with modern enclosed stoves, inappropriate fuel, a build-up of tar in the flue, cold snaps during holiday periods. Once alight thatch fires are almost impossible to control with salvage the only option for the Fire and Rescue Service.
The detail on the left, shows the positions of layers of thatch which have built up over the years. It also shows the missing brick, which would have been hidden between the thatch layers. The wood burner fitted in this chimney had no liner and the tar indicates leaking flue gases into the thatch.
The chimney on the right was also fitted with a wood burner, again with no flue liner. The chimney had no bricks, only a plaster construction, the chimney cracked with the heat. Both of these flues were an accident waiting to happen, and with a neat thatched roof the serious structural faults would have been hidden.
The pictures are details from the featured property and are an example of the damage caused from a thatch fire and also illustrate the hidden dangers and the difficulty in knowing where the fire started and the exact cause.
Thatch was a common roofing material long before chimneys were invented, with the obvious consequence of numerous thatch fires. The invention of the chimney reduced the risk but introduced a new range of issues and causes for fire in thatch. Because of the age of many thatched properties, chimney construction can be “unusual”. Some chimneys might be built off a cob breast, causing them to lean, and others might have lath and plaster in-fills where old fire places have been closed. Homes built before the introduction of the Building Regulations may often have timber lintels over a fireplace and timber joists built directly into the chimney stack; these can be scorched as protective pargeted linings disintegrate. Any chimney built before 1960 is likely to be constructed of single thickness brick work and parged but not lined. This type of internal sealing of the brick work will crumble with age after which further erosion of the brickwork and mortar will be assisted through acid condensation from flue gases. Even with a flue liner these chimneys are unsuitable for the installation of a wood burning stove.