Modern lifestyles require specialist fire risk management when thatch involved, says fire expert

A DEVASTATING fire destroyed many homes in St Francis Bay in the Eastern Cape on Sunday night (11 November 2012) and investigators are trying to assess the cause which may turn out to be an unfortunate combination of high winds, the open flames of a braai or an overheated chimney surrounded by thatch without the defensive surround required in today’s bylaws.    

We asked the chair of the Fire Services Investigation Committee of the South African Insurance Association, Marcel Wood, for comment about how homeowners can prevent and manage this type of fire event and prevent the type of spread of fire through homes that took place in St Francis Bay this last weekend.  Wood is also the head of Risk Management at Etana Insurance as well as board director of the Fire Protection Association of South Africa.

“The fire spread through neighbouring thatch roofed homes fanned by strong winds. Thatch in its simplest form is a dried type of grass interwoven to form a strong roofing material which is popular in holiday homes and delivers three main advantages:  individualistic décor, superb insulation in all seasons and, compared with tile roofing, is comparatively cheap and has been proving itself as a roofing material for 10,000 years.  

“In spite of these attractions thatch presents a higher risk of fire than other roofing materials and special precautions need to be taken.”

Fire risk management in homes

Wood explains that common ignition sources for thatch fires include electrical faults, hot chimneys passing through thatch, lightning and power surges, and, on rare occasions the embers from open flames of a bonfire or braai can be blown onto a highly combustible substance such as dried trees, wood piles or thatched roofs. 

· Electrical faults – requiring vigilant and regular maintenance to manage this risk

· Hot chimneys passing through the thatch roof – requiring purpose designed protective linings

· Lightning and power surges – effective surge protection devices are available for domestic and business premises. These work better than lightning protection rods  and more importantly protect electronic equipment  during power interruptions caused by power surges and lightning.

How thatch fires spread?

According to Wood, a ‘fire front’ is the portion sustaining continuous flaming combustion. As the front approaches, the fire heats both the surrounding air and woody materials, e.g. the thatch roof adjacent to the one on fire. They may also spread by jumping as winds carry hot embers and other burning materials through the air over roads, etc. that may otherwise act as firebreaks. It follows, in areas with multiple thatch roofs, that embers set alight neighbouring properties downwind from the fire.

It also follows then that the best method to prevent the spread of fires between thatched roof occupancies in a suburb is the application of water which cools the thatch below its combustion / ignition temperature. It is believed that St. Francis does not have a dedicated fire service meaning requisite cooling is missing. Nor do the thatch risks have any fixed type of water system installed to protect the thatch. The drenching systems are a far better protection method in any event in that fire fighting staff (and if none available, then likely homeowners) may well have to stand in the path of radiated heat and smoke (if they are downwind of the fire which is very likely to occur) and makes this an extremely difficult task. The drenching system does not require any human interaction and can be turned on (if not automatic) and then people can leave the area immediately thereby not endangering their own lives.

How can homeowners prevent what happened in St. Francis Bay?

Possibly, the best method to prevent these types of disasters happening is to have a dedicated drencher water system installed at the highest part of the roof which can cascade water over and down all of the exposed thatch in the event of a fire. Whilst it may not save the immediate property involved, it will certainly prevent or minimise the effect of having multiple properties destroyed. The reason is that thatch fires, on the back of high winds, can generate lots of radiant heat (the type of heat that prevents one standing too close to a braai for example) which assists dramatically, the spread of fire by heating up the neighbouring thatch to a temperature close to that of the ignition temperature of grass as well as carry hot embers and deposit them onto neighbouring thatch properties. So, if one can keep the thatch wet or cool in the first instance, it limits the effects of radiated heat as well as cools or wets embers that are deposited on neighbouring thatch roofs which “struggle” to set alight wet or cooled thatch.

How prone are thatch-roof homes to fires?

Thatch roofed properties are certainly more prone to fire than what is commonly termed “standard” construction in the insurance industry which is tiled roofs, etc. Simple reasons are that electrics (which all thatch homes have) can easily set fire to thatch (if faulty) as opposed to tiles. A big problem with thatch however are chimneys which carry heat through the thatch roof and can easily set alight surrounding thatch from the heat or embers from the braai. Lightning and more importantly surges are additionally another big risk making thatch properties more susceptible to fires than normal standard construction.

Thatch risks are insurable but need to meet some specific risk management criteria in order to be insured.