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 Fight the fire

Based on findings from the official forensic investigation into the cause of the devastating June 2017 fires, human activity as well as several natural factors was responsible for the fire outbreak. According to research by Knysna fire chief Clinton Manual, who conducted the investigation on the Cape fires, the deadly blaze was caused by man-made fires coupled with strong berg winds, drought, topography, and dry vegetation. 

“Bushfires are a natural disaster and parts of the world affected by global warming, such as Africa and Australia, will increasingly experience the horrific effects of these catastrophes,” says Kobus Strydom, FIRELAB owner and honorary member of the South African Emergency Services Institute technical committee.

In February 2009, Australia was hit by a series of bushfire disasters – the worst recorded in Australian history. Dubbed the ‘Black Saturday’ bushfires, the Victoria fire tragedy resulted in the deaths of 173 people, the injury of 414 people and destruction of more than 3 500 buildings. The country recorded a total loss of an estimated AUD4.4-billion.

As a result of the disaster, the Australian building regulations were revised to include new guidelines and standards for bushfire planning and building. The new regulations state that all properties will now require a bushfire attack assessment and a Bushfire Attack Level that outlines the type of construction required.

“So what lessons do we take from Australia’s biggest natural disaster? Certainly that fire safety policies and management are a key response that should be implemented by government and local authorities. However, government cannot do it alone. The public and private sector and in particular, the research and development sector need to play their part in assisting the country in the development of these environmental protection plans,” says Strydom.

Fire policies a hot topic

The South African built sector is guided by the National Building Regulations and Building Standards Act (No. 103 of 1977) and SANS 10400. Therefore regulation regarding fire protection is of high importance. According to the Institute for Timber Construction (ITC-SA), engineers signing off roof structures which do not comply with the Fire Regulations could be put to task with the Engineering Council of South Africa.

Professor Walter Burdzik of the Department of Civil Engineering at the University of Pretoria confirms, “Any failure of a truss plant or roof inspector to insist on the separation of roofs as per fire regulations needs to be reported to the ITC-SA. The same principle applies to low-cost housing; just because a roof is over a low-cost house does not justify deviating from National Building Regulations.”

“Compartmentation is a very important requirement very often neglected at the top floors of multi-tenancy buildings including hotels, hostels, offices, flats and more. Public buildings require special consideration, and in some applications not permitted in terms of the National Building Regulations,” says Strydom.

Fire 01Timber a safer choice

The aftermath of the Cape fires led to a lull in the local timber economy – more than a million cubic metres of timber was lost from South Africa’s annual supply. On the positive side, the use of timber in construction is on the rise.

When it comes to fire safety, engineers signing off non-compliant roof structures can be put to task. Image: Pixabay

The ITC-SA states while there are a few misconceptions around timber’s fire performance, structural timber for roofing is both commonplace and performs well under fire conditions. As with every aspect of building, timber roof trusses must be manufactured and erected in line with the National Building Regulations and SANS 10400, which provide for fire safety. 

“Building regulations, set in place by bodies such as the South African Bureau of Standards (SABS) after extensive research and consultation with industry experts, consider all aspects of a given building material’s composition and properties to ensure that it meets the same safety and performance standard as any other building material in the same application,” highlights the ITC-SA.

“There is a significant market in South Africa for timber-framed housing and log homes with thatch roofs. Steps can be taken to minimise the fire risk to these properties by using new innovations in fire retardants,” notes Strydom.

He adds that timber or log-home buildings with external walls treated with fire retarded treated timber as well as treated thatch boast a reduced fire load of up to 50%, therefore allowing safety distances to be reduced by up to a third.

“It is legal to use timber trusses for many applications in terms of the National Building Regulations. The use of timber trusses has challenges to consider if used in multi-occupancy and multi-tenancy structures. Fire divisions have to be addressed properly as to prevent the spread of fire.

“Although timber is combustible it can be used safely for stability which is the major consideration. Timber trusses can withstand fire better than light-weight steel roof structures. This is also applicable to light-weight steel buildings which are commonly found today,” explains Strydom.

“There are fire prevention requirements available in legislation and many technologies that can be utilised in the prevention and fighting of fires.” – Kobus Strydom, FIRELAB.

Fire prevention and treatment

Strydom highlights that timber trusses are only one of the components for a roof structure as the roof covering could either be combustible or non-combustible. Should both be Fire 03present like a thatch roof construction, both the truss and the thatch covering should be treated.

The most common causes of fires include human negligence and poor maintenance. Image: Pexels

“Thatched roofs are not the only combustible roof known, hence the test method, SANS 10177-12, for combustible roofs as stipulated in the National Building Regulations, SANS 10400-T. To prevent combustible roofs, trusses and the thatch layer from being ignited, it can be treated with a suitable approved fire retardant (FR) or protective FR treatment,” says Strydom.

Strydom says the treatment of the timber used for the construction of the roof structure must be treated using an industrial treatment process called vacuum-pressure impregnation (VPI). The process is similar to that of preservation treatment, SANS 457. Strydom adds that thatching grass used for the construction of thatch roofs can also be treated using the same VPI process as a permanent fire retardant option for the life of the thatch layer.

Tech putting out fires

Technology is available and can be used very effectively for most applications, says Strydom. However, it is not commonly known or ignored in most instances, he adds. Despite this, South Africa is a world leader with regards to fire retardant treatment of timber or cellulosic materials, he notes.

Strydom continues, “There are fire prevention requirements available in legislation and many technologies that can be utilised in the prevention and fighting of fires. The technologies available vary from techniques used in the fighting as well as additives to water in minimising losses.”

Common causes of fires within the built environment

  • Human negligence
  • Poor maintenance
  • Bad housekeeping
  • Electrical – negligence, bad maintenance or illegal installations
  • Arson – very common and fraudulent insurance related
  • Natural disasters – lightning, veld and bush fires
  • Unattended fires

Fire regulations relating to timber roof trusses

  • Each independent dwelling unit situated on either side of a fire wall must have its own bracing system within its roof structure, regardless of the fire wall projecting above
    the roof covering or not.
  • The fire regulations do not state the size of a permissible gap between timber members bearing on either side of the fire wall. However, trusses passing through a fire wall must be split into separate trusses.
  • The regulation states that ‘No part of the roof assembly, made of wood or any other combustible material shall pass through the separating wall.’
  • No tile underlay or insulation may pass over the fire wall.


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