Fire resistance in building materials allows occupants to escape and reduces the risk of structural damage, saving lives and reducing long-term disruption. It also increases the durability of structures, limiting their need for refurbishment and strengthening community resilience.
Concrete is one of the most durable and inherently fire resistant construction materials. It takes a long time for fire to affect its structural load-bearing properties and it helps protect less fire resistant materials like steel.
Wood
Wood is a sustainable material that can be used in a wide range of building applications. It can be used in conjunction with other materials, such as concrete and steel, to create high-performance, fire-resistant buildings. Innovative construction techniques are helping to improve the safety of timber-based structures, ensuring that fire safety standards are met.
Protective materials that cover wood framing members help to increase the time of fire resistance of walls, floors, ceilings, and roofs. These protective coverings may be made of a variety of materials, including gypsum board, aerated lightweight concrete (ALC), and mineral wool panels. Some empirical models based on ASTM E119 fire tests have been developed to quantify the added time of fire resistance achieved with specific protective materials.
Another fire protection method is the use of protective coatings that do not change the chemical properties of the loadbearing timber element but form a shell around it, inhibiting its thermal degradation and slowing down the charring rate. This increases the fire resistance of the timber element and prolongs its ability to function as a load-bearing structure.
The use of protective coatings is a simple way to enhance the fire resistance of wooden constructions. Modern intumescent coatings expand when exposed to heat, forming an insulating layer that significantly reduces the fire risk of timber elements. These systems are also effective in increasing the fire resistance of timber beams and columns, providing a cost-effective solution for timber-framed buildings. In addition to these protective measures, mass timber construction techniques, such as cross-laminated timber (CLT) and glued laminated timber (glulam), are gaining popularity because they provide superior structural performance with enhanced fire resistance.
Stone
Fire-resistant construction materials are a vital component of building safety. These materials are not only safer, but they also prevent the spread of fire and help prevent the release of dangerous smoke and toxic gasses. They also contribute to a more secure and stable structure, making them an ideal choice for high-rise buildings.
Concrete is one of the most commonly used fire-resistant materials. It maintains its strength up to 250degC, with a reduction in strength occurring when the temperature surpasses this point. Reinforced concrete structures can withstand fire for up to an hour at 1000degC.
Using fire-resistant concrete can reduce the risk of structural damage and the release of harmful substances during a fire outbreak. It can also prevent the engulfment of a building by flames, providing people with an unobstructed escape path and minimizing the impact of a fire.
Stone is a poor conductor of heat, and it can be used to increase the fire resistance of a building. Fine-grained sandstones can resist fire moderately, while granite and limestone disintegrate under fire. Brick masonry is another good option, and it can be made fire resistant by adding a layer of stucco to its surface.
Noncombustible fire-resistant insulation can improve a building’s fire rating and reduce its energy consumption. It is also more environmentally friendly than traditional insulation and is available in a wide range of shapes and sizes.
Brick
Bricks have a high fire resistance rating, but their ability to resist heat and flames can depend on how they are assembled into structures. The mortar used to bond bricks together can be vulnerable to sudden changes in temperature and can crack under the strain. For this reason, it is important to use special fire-resistant mortar when building with bricks.
Brick walls provide excellent thermal insulation, which helps to contain fires and prevent them from spreading quickly throughout a structure. They also do not erode under the effects of heat or flames, and their non-combustible properties are a safety benefit for occupants. Bricks can be combined with other materials, such as plaster and gypsum boards, to increase their fire-resistant qualities.
While natural materials like lumber and cotton have poor fire resistance, builders can treat them with specialized chemical treatments to boost their fire-resistance qualities. These chemicals form a char layer that subdues the flames and delays the effects of the fire for a specified time period.
The National Construction Code (NCC) divides buildings into five different categories based on the type of material they are constructed with. These construction types are then assigned a number that indicates the fire-resistant capabilities of specific elements within the building. For example, a concrete building with a fire-rated floor is classified as Type 1. In contrast, a wooden frame building with no fire resistant elements is classified as Type 5.
Timber
Wood is a very combustible material, but it’s the subject of ongoing research to make it safer. This work has informed past building codes and is guiding upcoming ones, making it possible for more projects to use the cost, schedule, and environmental benefits of timber construction.
Research into mass timber construction is proving that these structures are safe, strong, and resistant in the face of fire. When exposed to a fire, engineered wood products and mass timber char at a predictable rate, forming a protective insulating layer that slows combustion and prevents the interior wood from being affected.
As a result, mass timber and light-frame wood construction can meet or exceed the fire resistance ratings required by building codes. For example, when protected with gypsum wall board, cross-laminated timber (CLT) walls in a recent test lasted three hours and six minutes—far exceeding the two-hour fire resistance rating that is required by most current code requirements for buildings of this type.
The flammability of timber can be further reduced through a range of fire-resistant treatments, including immersing the materials in seawater or impregnating them with chemical formulas. Other systems, such as intumescent coatings, are spray-on solutions that expand on exposure to high temperatures, forming an insulating layer that protects the wood underneath.