Fire resistance in building materials improves occupant safety during fire events and reduces the spread of fire to adjacent spaces. It also helps minimise structural damage and delays the time it takes to reopen a building, boosting community resilience.
Natural building materials like timber are combustible but can be made more fire resistant with specialised chemical treatments. These slow the fire down and provide resistance for a few minutes.
Brick
Bricks are one of the most fire-resistant building materials available. When stacked together, they form a solid structure that takes a long time to break down or burn. They also block out heat and sound, making them ideal for use in walls. Many homebuilders incorporate brick in their houses to protect against fires, but they’re not the only option. Insulated concrete forms, or ICFs, are another great choice. They’re made from polystyrene blocks that connect like Lego pieces to create your house’s shell, locking out sound and weather. They’re also non-combustible and provide excellent fire resistance.
While no building material is completely fireproof, choosing the right construction materials can help limit damage and save lives. These fire-resistant materials prevent and slow the passage of excessive heat and fire, which reduces structural damage and allows more time for occupants to safely escape a building.
The fire-resistant properties of a building’s materials are determined through an evaluation of their ability to resist the spread of flame, smoke and toxic gases. Typically, materials are tested in a horizontal tunnel and assigned a fire rating of 20-minutes, one-hour or two-hours. However, these ratings aren’t necessarily accurate representations of the actual performance of a material in a real-world application, as they may only be exposed to the conditions for a short time.
Gypsum Board
A fire-resistant gypsum board wall or ceiling can slow the speed at which the fire spreads, allowing for more time for evacuation and limit damage. This is accomplished by preventing the passage of heat and smoke into living areas and reducing the release of harmful gases. This type of passive fire protection is essential in commercial and multi-tenant residential buildings, as well as hospitals and schools.
Gypsum board can be enhanced to provide a higher level of fire resistance. This is done by using a special core that is denser than the regular version. It is also infused with additives such as fiberglass. While this adds to the cost of a sheet of drywall, it can significantly reduce the speed at which a fire spreads. This gypsum board is called fire-rated gypsum board, or Type X.
The gypsum core is made with a noncombustible material such as mineral fibers, cellulose or fiberglass. It is then covered with a paper facing or other surfacing that has a flame spread index of 50 or less, according to ASTM standards.
This type of gypsum board is often used in walls and ceilings that will be exposed to critical or severe lighting. This includes areas that abut wall or ceiling mullions of windows, areas where light is reflected off glass surfaces, and long hallways or atriums flooded with artificial and/or natural lighting. This is because strong, oblique lighting can highlight surface irregularities and exaggerate them.
Treated Cellulose Insulation
Cellulose insulation is made from recycled paper products such as old newspapers, cardboard and office papers. It is treated with chemicals such as ammonium sulfate, boric acid and borax to ensure that it meets all governmental safety requirements. These chemicals are also what give cellulose insulation its fire resistance. This insulation is typically used in wall cavities and attics. It can be installed wet or dry. Wet cellulose insulation is installed using a blowing machine and is commonly called “blown-in”. Dry cellulose can be used to add insulating value to existing walls or it can be sprayed into new construction stud walls before drywall is installed. Both wet and dry cellulose require a professional installer.
Although cellulose is an eco-friendly insulation product, some people are concerned that it can burn and that it will lose its fire resistance over time. However, research has shown that cellulose has the same fire-resistance ratings as fiberglass. This is due to the fact that cellulose fibers are tightly packed together and effectively choke wall cavities of combustion air, preventing flames from spreading through them.
Cellulose is also treated with pest-resistant chemicals, which can be beneficial in regions that experience insect infestations. It can be added to wood framing to make the wood more resistant to fire and to help prevent mold. In addition, cellulose can be added to steel framing and gypsum board to make them more resistant to fire as well.
Mortar
Mortar is a workable paste that hardens to bind building blocks, bricks and concrete masonry units together, fill the irregular gaps between them, and add decorative colors or patterns to masonry walls. When a mortar contains fire-resistant material, it can enhance the safety of a structure by resisting the spread of fire and providing additional time for occupants to escape.
Noncombustible construction materials are often rated according to their ability to withstand the duration and temperature of fire. The American Society for Testing and Materials standard E119 “Test Methods for Fire Tests of Building Construction and Materials” defines a number of tests that must be performed to determine the fire resistance rating of building elements such as walls, floors, ceilings, roofs and beams.
The fire-resisting capabilities of building materials can be determined by exposing them to a controlled propane gas-fired furnace and measuring the time and temperature required for them to reach ignition. A building element’s fire resistance rating is the average of the time and temperature it takes for the combustible part to reach ignition and the time and temperature needed for the combustible part to cool down after reaching ignition.
The use of concrete containing coarse aggregates like foamed slag, blast furnace slag, crushed granite and cinder has good fire-resisting characteristics. However, a mortar containing coarse aggregates can be made fire resistant by replacing some or all of the sand with fly ash or ground glass waste (AGW). Krishnamoorthy and Zujip [55] used 100% AGW as fine aggregate replacement to produce fly ash geopolymer mortar. Their results showed that the addition of AGW had significant effects on the UPV, TCC and density of mortars as well as their thermal insulating properties but only a slight effect on their 28-day compressive strength.