A fire raging miles from where you live might not necessarily threaten your safety, but a fire in your building or home changes the situation completely. The risks of total devastation and even loss of lives are reasons why most developed countries have comprehensive fire regulations.
The Building Code of Australia (BCA) has performance-based provisions for fire resistance that all designers and builders must comply with. Section C, for instance, contains requirements that ensure a building is able to maintain its structural integrity during a fire, as well as prevent fires from spreading to other buildings.
Fire resistant systems need to be tested in accordance with AS 1530.4 - 2005: Methods of fire tests on building materials, components and structures – Fire-resistance test of elements of construction. Based on their test results, these systems will achieve a fire resistance level (FRL) that is measured in minutes, for example, a FRL of 90/30/60. ‘90’ represents the structural adequacy of the element, and applies for load-bearing walls, floors, beams and columns; ‘30’ relates to the integrity of the element, such as its ability to prevent flames and hot gases from passing through.
The last number – ‘60’ – refers to the insulation of the tested element, or its ability to maintain the temperature on the non-fire side of the separating element.
Kingwood Exterior Timber Cladding has excellent fire resistant performance
While fire resistance regulations are an integral part of the design and construction of buildings, Professor Jose L. Torero, Head of the School of Engineering at the University of Queensland, says they can also be ineffective. This is because they often hide inefficiencies, mistakes, misinterpretations and ignorance which can lead to expensive and poorly constructed projects.
At the same time, they are predominantly designed to be responsive rather than pro-active.
For instance, the true performance of fire safety systems and materials is only established in the event of the fire. This has led ‘designing by disaster’ to be inherent – when something enters the market but should not have, only a disaster (like a fire) will prompt the industry to respond by changing its standards.
A responsive regulatory system has many shortfalls, including slowing the use of new products or designs when they enter the market. Innovations often challenge codes and standards, says Professor Torero, which then requires the codes to change. However, this is rarely a surmountable hurdle:
“In some cases this is to allow a non-compliant product that is in reality good to enter the market, but in other cases, it is to stop a bad but compliant product that meets the requirements of the code.”
Fire aftermath: residents come to terms with the loss of their home in the Blue Mountains, NSW. Photo: Wolter Peeters. Source: SMH
Professor Torero addressed these issues at an Australian Institute of Building talk at the University of Melbourne last week. Titled ‘How do buildings burn?’, he argued that the weak links introduced in the ‘chain of safety’ are the reasons why most buildings burn today. Innovations driven by architecture, engineering optimisation and sustainability have created many weak points that have never been analysed.
“The current codes do not require for us to analyse them, therefore, it becomes very difficult to establish weaknesses. Most of the failures we see today are through those weak points,” he says.
The Glenorie house designed by Architect Glenn Murcutt still stands today despite being located in a highly fire-prone section of the bush. Source: SMH
Following the bushfires of 2009, Narbethong Community Hall by BVN Donovan Hill was designed to pre-empt new regulations. Image: John Gollings
Instead, a foundational understanding of buildings burn will enable the industry to understand and anticipate performance. This in turn, allows for a more proactive response to codes and standards, allowing architects to design in a preventive way.
“You free the market from rules and enable better products to enter with a true performance analysis,” explains Professor Torero.
“It also helps us to identify weaknesses in our practices and identify design weaknesses that otherwise will never be studied. It changes the responsive design by disaster to a proactive design by performance.
“The freedom that this can give to architects is enormous and the capacity it provides to engineers for true optimisation and sustainable design becomes real.”
A good example of this understanding, which spurs better fire-safe designs, is the Hollingworth House by Ian Weir Architect. Located in a bushfire zone, the house is situated near the diverse vegetation of the site and able to defend itself from bushfires. This means that, contrary to official advice, its occupants do not have to clear the surrounding vegetation away to reduce their fire risks.
"I'm fundamentally not interested in clearing vegetation just to achieve bushfire safety, because there are a lot of problems with that approach other than just taking away the nice trees," Dr Weir had said. Instead, he focused on a ground-up approach and included a number of design strategies to prevent a structural fire from occurring within the house during a bushfire. Read more about the project here.