Fire caused by a burning ember from chimney igniting a thatched roof
How this fire happened
Fire involving a Grade II listed thatched cottage dating back to c1680.
Most likely origin of fire: External face of thatched roof.
Most likely cause of fire: Accidental - Burning ember from chimney igniting thatch.
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Approx 18:00hrs: Occupier lit log burning stove (approximately 18 months old and fitted by a professional company).
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Approx 20:20hrs: Partner arrived home and all appeared well.
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Approx 20:30hrs: Neighbour informs occupier that thatch is on fire.
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Occupier and neighbour fight fire with two garden hoses. Occupier climbs on to roof and observes outer face of thatch alight 6" in front of chimney.
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20:46hrs: Partner evacuates child and calls 999.
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20:50hrs: First two fire appliances in attendance.
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Fire appeared to be out. OIC entered with occupier to inspect loft space from hatch.
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No sign of fire, no smoke, no heat
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Ladder pitched to loft hatch to enable access for crews.
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Flames observed breaking into loft space
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Fire fighting and salvage operations commence (first incident within Hampshire utilising "CAFS" compressed air foam system to suppress fire within the roof space).
Fire Investigation
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Burn patterns observed confirm that fire did not originate within the loft space
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Burn patterns observed indicating that fire originated to right hand side of chimney and spread to the left
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Chimney inspected from Aerial Ladder Platform. Mortar joints suspect, could this be due to fire fighting operations?
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Detailed External investigation revealed chimney only fitted with a "Bird guard" and not a "Spark Arrester".
The effect it had
We have lived in the premises for the past 2 years and are very aware of the dangers associated with thatch properties and the risk of fire.
The log burner and flexible metal liner had been installed by a professional company and the chimney swept on installation.
We only burnt well-seasoned wood and were under the impression that the chimney pot had been fitted with a "spark arrester".
Safety message
Research has shown that more than 90% of fires in thatched properties are caused by faults in the flue or chimney.
It is vital that chimneys are regularly swept. Owners should ensure that their sweep is experienced in the type of fire, flue and fuel combination in use.
Intervals between sweeping will depend on the fuel burnt and the duration of burning, but should be a minimum of twice a year.
Chimneys: The outside of chimneys should be visually examined on a regular basis for poor jointing and staining, both outside and inside the property.
Heat conduction through the chimney leading to the ignition of the thatch has been the subject of recent research.
In houses built before the 1960s unlined, single brick chimneys (112 mm) were constructed.
The outside of the flue in contact with the thatch can, under certain conditions, reach such a high temperature that ignition can occur, particularly where the thatch exceeds 1m deep.
In circumstances where the thatch depth cannot be kept to a minimum, there are devices on the market that either give warning of any undue rise in the temperature of the outside of the chimney, or provide an insulating barrier around the chimney.
Solid Fuels: Where heating is provided by the burning of solid fuels, it is best to avoid those that emit sparks or produce a lot of soot or tar deposits.
To avoid sparks landing on any surrounding thatch, consideration may be given to the provision of a spark arrestor, however due consideration should be given to the difficulties of access for cleaning purposes.
A more preferable option might be to ensure that the flue outlet is high enough above the thatch.
A vertical distance of 1.8m between the flue outlet and the thatched ridge should be sufficient, provided this dimension is maintained whether the chimney is sited at the eaves, the ridge or any point between.
Flues: In older premises, timbers were often built into the chimney with little if any, separation from the flue.
Over a period of time these timbers become so dry that ignition could occur.
It is recommended that a visual inspection takes place, with any offending timbers either insulated from the heat or removed completely.
It must be understood that any alterations to the timber structure should only be carried out with professional advice.
Chimney Pots: Where possible, the top of the pot should be at least 1.8 m above the ridge.
Tips: Have the brickwork and the joints checked by a professional builder. If in doubt consider fitting a steel flue liner.
Regular inspection and cleaning of chimney flues will help prevent fires, we recommend the following:
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Solid fuel appliances - once a year for smokeless fuel and twice a year for coal wood burning appliances - every three months when in use, note that soot builds up rapidly from wood fires; avoid using wet or unseasoned wood
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Gas appliances - once a year if designed for sweeping
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Oil appliances - once a year
Spark arresters can prevent sparks from the flue landing on the thatch; however they must be cleaned regularly.