Flammability thumb|right|River houses on the River Kwai Thatch is not as flammable as many people believe. It burns slowly, "like a closed book," thatchers say. The vast majority of fires are linked to the use of wood burners and faulty chimneys with degraded or poorly installed or maintained flues. Sparks from paper or burned rubbish can ignite dry thatch on the surface around a chimney. Fires can also begin when sparks or flames work their way through a degraded chimney and ignite the surrounding semi-charred thatch. This can be avoided by ensuring that the chimney is in good condition, which may involve stripping thatch immediately surrounding the chimney to the full depth of the stack. This can easily be done without stripping thatch over the entire roof. Insurance premiums on thatched houses are higher than average in part because of the perception that thatched roofs are a fire hazard, but also because a thatch fire can cause extensive smoke damage and a thatched roof is more expensive to replace than a standard tiled or slate roof. Workmen should never use open flame near thatch, and nothing should be burnt that could fly up the chimney and ignite the surface of the thatch. Spark arrestors usually cause more harm than good, as they are easily blocked and reduce air flow. All thatched roofs should have smoke detectors in the roof space. Spray-on fire retardant or pressure impregnated fire retardants can reduce the spread of flame and radiated heat output.
Flammability thumb|right|River houses on the River Kwai Thatch is not as flammable as many people believe. It burns slowly, "like a closed book," thatchers say. The vast majority of fires are linked to the use of wood burners and faulty chimneys with degraded or poorly installed or maintained flues. Sparks from paper or burned rubbish can ignite dry thatch on the surface around a chimney Fires can also begin when sparks or flames work their way through a degraded chimney and ignite the surrounding semi-charred thatch. This can be avoided by ensuring that the chimney is in good condition, which may involve stripping thatch immediately surrounding the chimney to the full depth of the stack. This can easily be done without stripping thatch over the entire roof. Insurance premiums on thatched houses are higher than average in part because of the perception that thatched roofs are a fire hazard, but also because a thatch fire can cause extensive smoke damage and a thatched roof is more expensive to replace than a standard tiled or slate roof. Workmen should never use open flame near thatch, and nothing should be burnt that could fly up the chimney and ignite the surface of the thatch. Spark arrestors usually cause more harm than good, as they are easily blocked and reduce air flow. All thatched roofs should have smoke detectors in the roof space. Spray-on fire retardant or pressure impregnated fire retardants can reduce the spread of flame and radiated heat output.