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Source Literature Similar To This And Related Others My own opinion on the reduction of risk of fire in thatched property. Any television or radio aerials should be, where possible be sited in the attic or externally on a gable end and not on the chimney so as to have the cable routed as far away from the thatch as possible. They should never be routed through the roof. Apart from minimising the risk from lightning strikes this will reduce undue strain on the chimney structure and remove the need for ladders on the roof for aerial maintenance. Ensure that any netting on the roof is fixed in such a way that it can be removed easily in case of fire. Twisting the tension strip of one panel to the next fastens most wire netting, a single twist will undo with minimum force making the easier rapid removal to provide fire crews access to the surface of the roof. All electrical wiring in the loft space should ideally be routed in appropriate fire retardant ducting to prevent possible rodent damage to cables and help contain a short circuit cable fire. http://www.niceic.org.uk/ A linked mains and battery powered smoke alarm should be fitted in the roof space in each bay. The use of these are not recommended in a normal attic by the manufactures but the insulating effect of thatch minimises the chances of false alarm through ambient temperatures fluctuations affecting them. (B.S. 5839 Pt. 6) http://www.newryandmourne.gov.uk/environment/building_control/smoke_detection.asp The chimney should be, if used by any appliance producing flue gases be lined according to the manufactures specification and in the case of solid fuels be swept regularly. The top of the stack should be no closer than 1.8 m from the ridge vertically and in the case of a stack in the wall 4 m vertically from any thatch surface. Spark arrestors on the flues should be treated with caution because they can clog and restrict the flow of flue gases. A stainless steel welders spark guard mesh made in two sections is my personal recommendation, the inner tube being fixed so that the flue brush enters it, an air gap to trap debris and allow cooling and the outer tube removable to allow for manual cleaning. Good quality smokeless fuel is preferable to ordinary coal or peat and any wood should be resin free (hard woods) and very well seasoned and dry to prevent build up of tars. Any building work requiring ladders or scaffolding resting on the thatch, in particular the ridge should be padded (for example rolled old carpet) this will minimise possible damage. Any building work that will result in rubble or mortar dust being shed onto the roof should have that area completely covered full length of the roof so that no building materials such as paint or mortar become lodged in the thatch. The lime in mortars are particularly harmful. Do not cut recessed lighting into the ceilings below the thatch. Light fittings within the roof space should be in a bulkhead fitting. External floodlights should not be located just under thatch overhangs. The provision of a loft hatch will be required for fire fighting purposes. The minimum recommended size is 600mm x 900mm ensuring that access can be gained to all roof void areas. It would be advantageous to have an external water tap and hose reel supplied from the rising main, appropriately lagged against frost and capable of reaching all parts of the roof, both externally and internally with adequate pressure and fitted with a pump if needed. Generally common sense is the best guide, although thatch in a well maintained condition is difficult to light, when it is allowed to decay or has been loosened, it is similar to the lighting of a solid block of wood, if this is half rotten or split into small pieces it will burn more readily. Do not burn garden waste, and try and persuade your neighbours not to do so particularly in dry and windy weather. The greatest area of risk is under the eave and in the roof void, never allow paint burning in these areas, and only have compression joints on plumbing to avoid the use of blowtorches. If you are thatching a new roof, or one that has had to have the rafters renewed, my advice would be to build in a fire retarding barrier - see PLANS this will at least give a measure of protection to the rest of the house and isolates the roof from possible internal source of ignition. It is possible to very effectively fire retard all the materials but if it will wash off, or does not penetrate the entire thickness I consider it to be of very limited value. For good protection the material has to be soaked in retardant, dried and then used - this will be very expensive but is effective. Remember that thatch, as we know it has been in use for hundreds of years, most properties, even today, do not fulfil all the above criteria. Unfortunately when a thatch does catch fire it invariably makes the news, could it be the rarity of occurrences? In nearly 40 years if thatching I have had to re roof only one and repair three with minor damage. (none of them thatched by me!) Most incidents are due to glaring omission of common sense rather than any inherent flammability of thatch. It is also worth noting that most thatch fires seem to happen to roofs that require re thatching but I expect this is also a coincidence ! To be extra careful note the latitude and longitude of your property, this can be vital for the services to find you quickly, the site of the nearest fire hydrant (yellow 'H') and stream, pond for water.
The objective of the research being carried out by the team at RHM Technology is to identify' and eliminate the major causes of preventable fires in houses with thatched roofs. STRUCTURAL DAMAGE Thatch fires make up a minor position of all domestic fires in the UK. Unlike other fires there is seldom loss of life. The only question currently asked, at the time of a thatch fire, is "what is the source of ignition" (malicious or otherwise)? Research has shown that a high proportion of thatch fires are chimney related, probably as many as 90%. FIRE FIGHTING Fire brigades with a large number of thatched properties in their area have special problems. Each has its own strategy for dealing with thatch fires, though experience shows, whatever the initial response, thatch ultimately demands a high level of manpower and equipment in attendance. Fighting thatch fires is problematical, properties can be in isolated rural locations and difficult to find, especially in the depths of winter. The fire is often well alight before it is detected and the brigade called. Fighting thatch fires carries a high risk of injury for firemen. Fire fighting is frustrated for a variety of reasons. Pouring water onto thatch is ineffective (a thatched roof is designed to repel water). The insulating properties of thatch counteract any cooling benefit from water. Once established, a thatch fire can be sustained by oxygen diffusing from beneath the roof. Wire netting on the outside of the roof, restricted loft access and barrier boards add to the difficulties of dealing with a thatch fire. Under these circumstances the brigade strategy can often only be one of salvage. Thatch has an ability to burn unseen, making the cutting and placing of fire breaks difficult. Insurers are becoming alarmed by the increasing number of fires associated with thatched properties. The level of damage from a thatch fire means that claims are high, the average cost per claim in 1995 was £8 5k. From insurance records it can be seen that the incidence of thatch fires is seasonal, occurring in early autumn, late spring, during cold snaps, weekends or holiday periods. Problems seldom start in unoccupied houses. For CGA 50% of claim payments are fire related, but these constitute only 7% of the total number of claims submitted. CURRENT ADVICE Current advice to thatched property owners is in containing or retarding a fire rather than in identifying the most likely cause. Because many thatched houses are listed buildings and because there is inconsistency in advice given across county borders, planning requirements vary. Some conservation officers favour the installation of "thatch batts" and barrier foil as "underlay" for thatch. Research elsewhere is examining this practice in relation to moisture migration through thatch and its effectiveness as a fire barrier. In some areas, unless straw or reed is treated with chemical fire retardant, thatching a roof would not be allowed. This requirement has led to some thatching projects going ahead where otherwise an alternative roofing material would have to be found. Only limited records are available to indicate the effectiveness of chemical treatments as a means of controlling fires. The modern thatching industry faces a variety of challenges. Many thatched properties are listed buildings forming a valued part of our heritage. A fire in a listed building is doubly distressing not only to the current owners but in the irretrievable loss of a unique structure. In formulating conservation strategies it may be necessary to sublimate some entrenched views to ensure that the building can be protected from fire as well as other modern types of wear and tear. The formula quoted by the National Trust is "to conserve and preserve a property in the right way, following what has gone before". This would involve maintaining the building in perpetuity, giving value for money and following the best methods to prevent fires. PREDICTIONS Results from a mathematical model of the processes of heat transfer in thatch have produced a series of temperature, time and condition profiles indicating conditions which are likely to result in a thatch fire. Few thatched properties are new buildings, many of them have listed building status. The majority of thatched properties have chimneys built prior to the 1960s when chimney construction was of only a single brick thickness. At this time many thatched properties had large inglenook fire places, where flue gases would be mixed with large quantities of cooling air, drawn in through ill fitting doors and windows. Traditional thatch maintenance techniques often require a spar coating to be applied over existing thatch. Under these circumstances, and over a long period of time, the depth of thatch can reach up to 2 metres, 1 metre is not uncommon. Under these conditions the insulating characteristics are such that little heat is lost through the body of the thatch. On the other hand 10 cm thickness of chimney brick is a relatively poor insulator and even in circumstances when the brick work is sound, heat is easily transferred into the thatch. The temperature profiles which can develop in thatch, a metre deep, when flue gases reach 300~C. This level of heat transfer into the thatch can occur after only 12 hours of continuous use. Once a sustainable temperature of over 200~C has been reached within the thatch, conditions are favourable for the first stages of slow breakdown and charring. Under these circumstances, over a period of time, changes can occur which may lead to a potential for fire. Because these changes occur within the deep body of thatch, a fire generated in this way may be well alight before discovery. Prolonged, high temperatures can lead to ignition of thatch even with an intact chimney. Where a faulty flue allows gases to escape the risk is increased. Heat generated by a woodbuming stove was so intense that, over a period of time, the whole chimney had become distorted and cracked. Enclosed solid fuel stoves are becoming very popular with thatch property owners. Under normal operating conditions it is not unreasonable to expect flue gas temperatures to reach 300~C, when a fire is burning strongly temperatures can rise to 600~C and higher. In properties with double glazing and extensive draught proofing, flue gas temperatures remain high for the entire length of the chimney. Changes in the way people live, double glazing, wood burning stoves to replace open fires, has probably led to the steady increase in the number of thatch fires. Thatch adjacent to a single skin brick chimney will reach 85% of the flue gas temperature after one day of continuous use, with little cooling across the brick work. THE EVIDENCE Findings predicted by the model have been supported by evidence from fire brigades and "post mortem" examinations carried out following fires in thatched properties. All the fires investigated in 1996 appear to have been chimney related. LOOK FOR THE WARNING SIGNS Spark arrestors, up to now, seem to be given tentative approval, though in this investigation even thatch fire visited had some type of device on the chimney pot. If fitted, spark arrestors must be cleaned regularly. Soot is a powder! Any solid material or tar removed from a chimney during sweeping a should be investigated. Thatch separating from the chimney could be drying out from excessive heat. Ask your thatcher to inspect the condition of the thatch and chimney. Check pointing and flashing regularly particularly where the chimney is surrounded by thatch. FIRE PREVENTION Sweep chimneys regularly and thoroughly. Burn only dry and seasoned wood. Install a chimney liner, advice can be obtained from the National Association of Chimney Lining Engineers, telephone: 01785 811732. Whilst essential, smoke alarms in a thatched property alert the owner often too late. In thatch fire prevention is essential, detection is usually too late! © This article is a summary of research being undertaken at RHM Technology, High Wycombe as part of the "Partners in Technology" initiative funded through the Department of the Environment. CGA Select (a division of CGA Direct Insurance Brokers) and supported by in-kind contributions from the thatching industry.
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