Part of a successful passive fire protection strategy is reviewing construction materials for their ability to inhibit the spread of fire. This ensures the right levels of protection for a building...Continue Reading
Part of a successful passive fire protection strategy is reviewing construction materials for their ability to inhibit the spread of fire. This ensures the right levels of protection for a building in the event of a fire and is in line with stringent building and construction regulations.
When it comes to fire-resistant materials, it’s important to know that not all were created equal. Multiple factors are considered when choosing the right material, from their load-bearing capabilities to their tendency towards decay. In this article, we will be reviewing the specific fire resisting properties of common building materials.
Brick and Mortar
Brick is resistant to fire up to the temperature of between 800°C and 1200°C. A building constructed from brick is held together with mortar, and it is this mortar that is less effective as a fire-resistant material.
Mortar is a component material in masonry construction. Its purpose is to fill the gaps in between the blocks and bricks that come together to create walls. Most mortar is fire resistant to some extent, as the materials that make it (usually a mix of clay, cement, lime, and sand) are resistant to fire and heat. Mortar can, however, crack and expand as a consequence of being exposed to temperatures. Hence why mortar can let the side down when it comes to brick construction.
Stone suffers under the effects of fire and is prone to disintegration when suddenly cooled. Based on the specific type of stone, the exothermic reactions can vary greatly. For example, granite explodes when exposed to heat – and therefore requires extensive risk management when used as a construction material. While limestone tends to crumble in high temperatures, sandstone’s unique composition (formed of small mineral particles and rock fragments) means it can usually withstand moderate fire conditions and is less likely to crack and break apart like other stone materials.
While wood is known as a common conductor of heat, timber that is used in heavy construction can be reasonably fire-resistant. The fire resistance levels of building materials will often differ following the addition of surface chemicals such as ammonium phosphate, sulphate, and zinc chloride. Timber can also be painted to provide an extra layer of fire protection. This reminds us that it is important to make the distinction between raw materials and materials that have been treated as part of the design and construction process.
Fire-retardant materials should not be confused with fire-resistant materials. Fire-retardant materials are designed to burn much more slowly, in comparison to some of their more flammable counterparts (such as plywood and fibreboard.)
Steel is well known for its enduring structural integrity. Steel buildings are resistant to degradation, withstanding the adverse effects of termites, rust and rot. However, steel is not so able to hold out against the temperatures of fire. When exposed to fire for too long, steel beams will sag and the columns will buckle, causing the structure to collapse. Heats of 600°C can induce the stress of mild steel, and at 1400°C, steel will melt completely.
It is for this reason that structural steel is often reinforced using intumescent paint. This paint forms a carbonaceous layer when subjected to extreme temperatures, offering additional protection to steel beams. To find out more, consult our guide to structural steel fireproofing.
How concrete behaves under high temperatures depends upon its composition of materials. This is to say that the quality of both cement and aggregates used will affect the fire resistance of building elements. Usually, reinforced concrete will tolerate temperatures of up to 1000°C for about sixty minutes before it begins to lose its strength. We cover this subject in more detail in our guide to the fire resistance of concrete.
Much like stone, glass will crack and shatter when it is exposed to heat and then left to then cool down again. Therefore, site teams will commonly use reinforced, toughened and laminated glasses for safety reasons. These glasses, especially those that feature steel wire, are far more fire-resistant than ordinary glass.
Cast iron is not frequently used as a common building material. This is because of its behaviour under high temperatures. When exposed to heat and then suddenly cooled, cast iron will shatter into pieces. Because of this, cast iron will often be covered with brickwork or another more stable fire-resistant material, such as concrete.
Fire-resistant materials are treated to reinforce them against extreme temperatures. These materials cannot be 100% fire-resistant however; fireproofing is a method that works to massively reduce their susceptibility to fire. Ultimately there is not a single material that cannot ultimately be destroyed by the effects of heat. It is for this reason that passive fire protection is so important. Choosing the right materials is only a small part of protecting buildings against fire. If you’re interested in finding out more, we recommend you start with our article on structural measures to prevent the spread of fire.
CLM Fireproofing are leading experts in passive fire protection and firestopping. We work with clients to identify areas of improvement in their fire protection strategy. By offering a comprehensive range of services, including compartmentation and spray-applied fireproofing, our clients are assured that their fire protection systems are reliable, auditable and compliant with the latest industry standards. If you would like to find out more about our passive fire protection services, contact our team of specialists today.