Fire resistance of building materials improves the safety of occupants and firefighters during fire events, minimises damage, and ensures buildings can return to use quickly, boosting community resilience.
Non-combustible materials are non-flammable and do not contribute to the spread of fire. They also do not produce toxic gases. Combustible materials, on the other hand, burn easily and increase the intensity of fire.
Timber
Timber frame buildings are often perceived to be a fire risk, but that’s not necessarily the case. While natural building materials such as lumber and cotton offer very little in the way of fire resistance, builders now have access to a range of specialized chemicals that can improve their performance. In fact, recent research has shown that CLT (cross laminated timber) can achieve a fire resistance rating equal to or better than those of concrete and steel-framed buildings.
Timber’s inherent fire resistance is derived from its slow rate of combustion. Once the exposed surface of a timber element has burned away, a layer of char forms that limits oxygen supply and acts as an insulator. This char layer also subdues the fire, delaying heating of the unaffected core. Timber can also be treated with fire retardant chemicals or intumescent paint to further enhance its performance.
Other mainstream structural materials such as concrete and steel are also very fire resistant, providing a significant amount of time before they reach the point at which their mechanical properties begin to be affected by a developing fire. For example, metal begins to melt when it reaches a critical temperature, but concrete remains intact well past that point, so it can provide substantial structural support. For this reason, many concrete structures have been tested and verified to meet or exceed the current fire safety codes.
Stone
Fire is one of the most destructive forces to monumental and architectural stone heritage. Practically all historical churches, palaces and other buildings have suffered from the effects of fire at one point or another. These effects include aesthetic changes, such as a color shift to reddish hues and structural damage caused by the oxidation processes triggered by sudden temperature increase.
Stone is a common building material, and there are many different types of stones. The fire resistance of a stone depends on its mineral composition, the aggregates and cementing materials used to produce it. For example, compacted sandstone has higher fire resistant properties than polished granite, and brick is less flammable than stucco.
Concrete is a popular construction material, and it can also provide excellent fire resistance. This is because it has low thermal conductivity, which means that it takes a long time for fire to spread through it.
For added fire protection, consider using rock wool insulation in your building project. This noncombustible building insulation is highly effective at reducing the speed at which a flame travels, helping to prevent dangerous structural damage and toxic smokes. Rock wool insulation is also approved for use in Wildland-Urban Interface Zone (WUI) buildings, so it can be used in areas with stringent fire regulations. It is available in a variety of thicknesses, widths and profiles, allowing you to achieve the look you want while meeting WUI requirements.
Concrete
The fire resistance of concrete helps to improve the safety of occupants, fire fighters and neighbouring buildings. It also minimises damage, allowing structures to be used for longer and boosting community resilience.
Natural building materials like timber and cotton offer poor fire resistance, but they can be made more resilient with specialised chemical treatments. Concrete and gypsum, however, offer excellent fire resistance.
The constituent components of concrete – cement (limestone, clay and gypsum) and aggregate materials – are non-combustible, making the material impervious to fire. Furthermore, concrete has a slow rate of heat transmission. This means that concrete walls in a home act as a fire shield, protecting rooms from flames and maintaining their load-bearing properties for a long time.
Concrete’s fire performance is influenced by its aggregate type, water-cement ratio and moisture content. Concretes with lower unit weights generally perform better than higher ones, with the use of lightweight aggregates providing particularly good performance. Concretes with a high permeability may experience spalling, especially if they contain silica.
The addition of polymer or polypropylene monofilament fibres significantly increases the ‘fire resistance’ of concrete, helping to reduce explosive spalling in the event of a fire. The fibres melt at around 160 degC, creating channels through which water vapor escapes and minimising pore pressures in the concrete. In the case of tunnels where this option is not available, alternative measures are employed, such as local concrete thickening and cladding using heat shields coated with intumescent paint.
Glass
Fire resistant glass is a highly useful safety feature for building construction. It is specially designed to withstand high amounts of heat without cracking or shattering, protecting occupants from serious injuries and deaths. It also helps to keep the fire contained within a limited area, keeping people safe while they wait for help or assistance.
There are several types of fire-rated glass, including insulating glass with an invisible barrier between layers, which doubles the time it takes for the inner layer to break. This glass has the added benefit of improving energy efficiency. Another option is tempered glass with wire reinforcement, which is often used in doors that need visibility while also offering fire resistance.
When it comes to fire resistance, rated glass must pass a number of tests to ensure that it meets building codes. These tests include putting the glass in a fire-rated wall and subjecting it to varying temperatures over a set period of time. The tests are regulated to simulate the different stages of an actual fire and determine how long the glass will retain its integrity.
The glass can also be tested to determine its ability to restrict radiant heat transmission. This is important because unrestricted radiant heat can cause paper, drapes, clothing, and other combustible materials to ignite even though they are not in direct contact with the fire.