Stop Chimney Fires in Thatched Properties

A quintessential “Chocolate box” thatched house is a unique feature of the UK country landscape. Add a glowing wood burning stove on a chilly spring evening and the picture becomes a rural dream for some lucky (or unlucky) families; that dream combination is not without extreme risk for the unwary.   A chimney fire is wholly preventable.   In a thatched property, a fire in the chimney can easily spread to the thatch and once alight thatch is very difficult, almost impossible, to put out.  The damage caused in dealing with a thatch chimney fire can be devastating.

Records taken over many years show March to June, is the most likely time to experience a chimney fire.  Peak times are during cold spring bank-holiday weekends, after the central heating has been turned off.

There are two causes of chimney fires, nesting birds and using unsuitable material as fuel.

Bird Nests

A determined pair of Jackdaws can fill a chimney with large twigs and sticks in a surprisingly short period of time.  Next time a fire is lit in the hearth below, the Jackdaws sticks, above, can catch fire. Burning twigs can be ejected onto the thatch.

An essential precaution is to fit a bird guard, your thatcher or local chimney engineer will advise. A clean bird guard indicates that properly prepared and stored fuel is being used.

Chimney Fires in Thatched Properties

Selecting fuel for a wood burning stove

Wood burning stoves are not incinerators. The only safe fuel is properly seasoned wood. All wood should be stored in a position that allows free air circulation, protected from rain and adverse weather. Inappropriate fuel will cause a rapid build-up of flammable tar in the liner.

Chimney sweeping

Regular cleaning and sweeping is essential. The chimney must be swept at least twice a year when logs are used and more often if they are constantly in use.

A sound, unrestricted chimney flue is essential to the safe operation of the stove.  Tar is flammable.

In thatched properties sweep the chimney in the autumn and in February.  Look for the warning signs: soot is a powder and looks like black granulated sugar, but any hard black lumps are tar.

Blockages & Chimney Fires

Water vapour combines  with other gases and particles going up the chimney and unless the chimney is kept warm, the condensation forms a creosote-like substance  which  hardens  to  form  tar  on the  surface  of  chimney liners  and  may  seep  into  brickwork  in  an  unlined  chimney.  The following picture is a blocked liner after only one year of burning chemically treated builders’ timber off-cuts.

Chimney Fires in Thatched Properties
Roof Thatchers - National Society of Master Thatchers