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A fire can be a weapon of mass destruction, recent fires in Knysna and London highlight the lightning speed and ultimate devastation that fire can cause. Michael Howard from Micon Coatings says that a thatched roof structure is no more likely to catch alight than those constructed of conventional roofing methods.

“The difference lies in the fact that once a thatched roof structure does ignite the chances of being classified as a total loss are significantly higher,” he says. Thatched roofs may be susceptible but preventative measures can be taken and that’s where fire retardant coatings and treatments come in to play.

Micon 01A fire spreads quickly and can destroy everything in minutes.
Image: 
Micon

Getting the thatch ready

“It is extremely important that the owners have a plan of action should their structure catch alight,” says Howard. A thatched roof fire once established will burn in temperatures exceeding 1 000°C,” says JC Steenkamp from Highveld Cape Thatchers.

Steenkamp also says that fighting a thatched roof fire carries a high-risk of injury for firemen and the general public involved in combating the fire. Before using anything to prevent fires, the thatch needs to be prepared properly.

Theo Bassoon, director at Fire Protection says, “It is important that grass cuttings are combed before a fire retardant is used.” Howard says there is a product that may provide a permanent solution. “The chemical is applied by vacuum pressure impregnation of the grass prior to construction. This allows for the entire thatched layer to be protected, with a fire-retardant chemical and biological preservative. The chemical attaches itself to cell structure of the grass, which on exposure to heat activates the fire retardant component,” he says.


“A grass crop must be sprayed everywhere.”
– Theo Basson from Fire Protection.

Treatment of thatch can last for five years. “The grass cannot be combed or brushed after treatment for at least five years,” he says.

“It is also important that the chemical UV provides light protection and works as a binder to make sure the fire retardant is out of the rain,” says Basson. A certificate is issued that is valid for five years, after which the application must be repeated. With more than 30 years in the industry, he recommends the following application system as the best.

“A compressor capable of delivering at least 3 000 PSI must use 0.9l/per m2 on the outside surface. At least a double layer on the inside, two to three layers on the ear, foot and risk area. For example, around braai areas, gas stations, or if your lapa or house borders an open field, then part two must be sprayed. If your roof is treated like this, the roof is well treated,” he says.

If a new roof is built, foil can be inserted to cut off the flow of oxygen during a fire. “It is best to use fire-treated grass to build the roof. The third option is to use a fire-retardant system after the roof is already built,” he says. The principle of flame retardant is like most manufacturers’ products, “but the quantities of chemicals per m2 differ. Some companies just spray outside and leave the rest. In my opinion, a grass crop must be sprayed everywhere where you can see grass. From outside, inside, base, overhangs,” says Basson.

How retardants stop fires
Matthew Human from Fire Shield says that fire retardants form a protective cap around the grass. “The fire retardant forms a translucent layer that stops the fire to pass. Therefore, it is important that the inside, as well as the outside and the edges (edges) are covered with this layer,” he says.

There are several spray-on products on the market, says Anthony Carte of Country Craft Thatching. High-temperature resistant glue, also called a phenolic, together with a binder is used popularly in the community. This attaches to the grass to a degree. “This reduces the flow of oxygen. The inside of the roofs is treated twice with the fire retardant, therefore cutting off oxygen to a large extent of a fire that may originate from the inside. The earrings are also treated twice, which also reduces oxygen flow,” says Basson.

Howard describes a chemical that is applied using a high pressure airless compressor into the thatched layer. “This achieves a minimum penetration of 75mm on the exterior and 10mm on the interior. This ensures that as the thatched layer ages and deteriorates; the newly exposed sections of grass stem are still protected for the duration of certification,” he says. On exposure to heat, this fire retardant will intumesce (foam and expand to create carbon).

“This expansion allows for absorption of heat, blocking the transfer onto the grass stems. As it happens over a larger area, the intumescing will also bind the expanding stems together creating a carbon barrier suffocating the air flow into the fire,” he says. By treating a thatch roof with the high-pressure chemical, the radiation is lowered from 12kW/m² to just 0.48kW/m².

If a treated roof catches fire, then the phenolic retardant will melt and black spots will burn which is called ‘charring’. The fire will struggle to burn the charring, therefore slowing down the system. “The retarder also seals the points of the grass ‘helmpies’. This is usually where the afterglow hides a fire and then flares again as soon as a wind blows on the grass,” he says. The afterglow is an indication that the fire isn’t completely quenched. Foil 420 placed between the interior spray coating and the thick thatch covering layer is also an effective fire retardant. “This not only retards the spread of fire, giving time to fight the fire, but also provides insulation against drafts,” says Carte.

Howard explains how one of two things may happen after the afterglow appears. “The first is the ignition source may be effectively worn out, taking heat out of the equation and the fire self-extinguishes, or the process will slowly continue repeating itself until the heat source and available fuel outweighs and overpowers the fire-retardant capabilities, finally flashing over into a fully developed fire,” he says.

An untreated lawn can be burned within seven minutes and some fire retardants can slow this down by 24 hours. “We have a testimony of an international hotel and casino group whose lawn was treated by us. The lightning struck a hole across the roof. There was no fire. Just a lot of smoke. They could quench the smoldering smoke, and fill the grass again,” says Marshall.

A well combed thatch is easier to treat against fires.
Image: Fiber ThatchThatched roofs are used over various buildings like, lapas and braai areas. 
Image: Thatch of the DayA fire spreads quickly and can destroy everything in minutes.
Image: MiconThatched roof saved by a fire retardant. 
Image: Micon

Steenkamp highlights the importance of maintaining the structure. “Maintaining the structural integrity of the building is the single most important aspect regarding the fire safety and performance of a thatched roof under fire conditions,” he says.

The compaction of the thatch plays an integral part in the effectiveness of the thatch to withstand the exposure to heat. When tightly packed the effect is like burning telephone books. The lack of oxygen in feeding the fire can delay its development and propagation,” he says. In areas where the thatch is not compacted the oxygen flow in between the strands of grass assists in the propagation of the fire.

Fire retarders must comply with the ASTM E 108 test that can be done at the SABS. “Such a test applies to the chemical manufacturers of the fire retardant,” says Basson. Added benefits of a fire retardant include reducing sun and weather damage. A copy of the test report should be requested on enquiry and a certificate must be issued on completion of work.

Errors and risks
Howard states that owners and others underestimate the risks associated with a thatch fire. There is a level of preparedness required should you be a victim of a fire in a thatched roof structure. Having smoke alarms around the structure, practising emergency drills, as well as having a packed emergency bag and emergency numbers stored on your phone can go a long way to saving the lives of those in the building.

“Thatch fire problems also occur due to careless use of fire near the roof but I believe in a layer of Sisalation,” says Carte. The biggest mistakes Basson has seen are human errors or fraud where certificates are extracted without any application, or the contractor dilutes the chemicals. He has also found that applicants do not follow manufacturer's instructions. “The risk is that the roof does not have a proper fire-retardant system which provides little or no protection,” he says.

To prevent errors inspection staff should maintain a standard follow up with the client – after five years. “Chemical manufacturers must train inspection staff,” Basson recommends. Better controls can also be taken, some chemicals have a white glow when wet. During inspections, the white glow helps to identify whether the applicator has sprayed to the top of the roof.

Human says that the SABS fails the industry when it comes to distinguishing and regulating retardants. “One of the products contains toxins like formaldimine,” he says. Using a retardant that contains toxins can cost people their lives.

“Thatched roof firefighting techniques are specialised and knowledge of them are necessary to effectively and safely combat the fire,” says Steenkamp. Whatever fire retardant you use ensure the applicator has a certificate of compliance (COC) of treatment that is accepted by all insurance companies, municipalities and fire engineers. Care must be taken when selecting a fire retardant for your thatched roof. The efficacy of the product is tantamount, and all products should be backed up by comprehensive testing reports from agencies such as the SABS or Firelab.

“It is important that clients know that thatch roofs are not ‘fireproof’ after treatment,” says Basson. “It reduces the flammability or delays the ignition of its protected substrate,” says Howard.

“The best way to fireproof your thatch is to ensure thatch awareness and to have access to very effective fire extinguishers,” adds Carte.

Must have preventative measures 
  • A fire evacuation strategy.
  • Regular fire drills for occupants.
  • An escape route planned.
  • Easily accessible alarm activation system.
  • Torches, fire blankets and important documents kept in a central and accessible place.
  • Keys for security doors and burglar bars kept in a central and accessible place.
  • An assembly point outside for occupants.

 

Other must have requirements 
  • Be properly insured.
  • Have all property plans approved.
  • Have your thatched roof constructed to SANS 10407.
  • Ensure that a properly tested and recognised fire-retardant system is applied.
  • Have working smoke alarms scattered around the home.
  • Have working fire extinguishers scattered around the home.
  • Ensure all electrical wiring is installed in compliance with applicable standards.
  • Ensure all chimneys are installed in compliance to applicable standards.
  • Ensure spark arrestors dissipate any sparks emanating from the chimney.
  • Ensure water proofers, plumbers and any contractors use no equipment which cause sparks/open flames.
  • Ensure braais or bonfires are positioned well away from the roof.


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T-01: Thatched roofs are used over various buildings like, lapas and braai areas.
F-12: A well combed thatch is easier to treat against fires.
15: Thatched roof saved by a fire retardant.

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T-01: Thatch of the Day
F-12: Fiber Thatch
15: Micon

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