Looking at the current state of building fire safety, casualties and building destruction caused by substandard fire-resistant materials still occur from time to time. Among these incidents, the improper selection of fireproof material types and failure to meet quality standards have led to massive casualties during fires; buildings fail to withstand the invasion of fire, ultimately resulting in the loss of life and property.
It is evident that building fire safety is directly related to people’s lives, making the correct application of fire-resistant materials highly worthy of attention from construction entities.
With the emergence of new fireproof materials in recent years, countries globally have also strengthened public awareness and education on fire safety, continuously enhancing the level of building fire protection.
So, what are the common and widely used fire-resistant building materials?
Fire Performance and Mechanisms of Fire-Resistant Materials
Fire Performance
The fire performance of a material primarily includes its combustibility (reaction to fire), fire resistance rating (fire endurance), toxicity, and smoke generation.
Fire-Resistant Mechanisms
Combustible materials can be encased in non-combustible coatings to prevent contact with air, thereby transforming combustible surfaces into fire-retardant ones. Adding fire-retardant additives into the material can achieve inherent non-combustibility. Under high-temperature conditions, some materials will form a glaze film layer that isolates oxygen and provides thermal insulation. Additionally, the surface material may undergo intense intumescent carbonization, forming a difficult-to-burn, sponge-like carbonaceous layer. This effectively cuts off oxygen and prevents heat transfer to the substrate.
Common Fire-Resistant Materials
Many materials possess inherent fire resistance due to their natural characteristics. Common examples include stone, cement, metal, ceramics, and glass. Additionally, flame retardants can be added directly into materials or applied as coatings to surfaces requiring fire protection. This ensures the materials do not ignite when exposed to fire, effectively preventing the spread and escalation of the flames.
1. Stone Materials
Whether natural or artificial, stone materials inherently possess certain fire-resistant qualities, though these vary across different types of stone. Some stones will undergo chemical decomposition when exposed to high temperatures.
- Gypsum: Decomposes at temperatures above 107 °C (225 °F).
- Limestone and Marble: Decompose at temperatures above 910 °C (1,670 °F).
- Granite: Cracks at 600 °C (1,112 °F) due to the uneven thermal expansion of its constituent minerals.
Gypsum
Gypsum sets and hardens very quickly, though its overall strength is relatively low. Once hardened, it develops a highly porous structure and expands slightly in volume, which provides excellent thermal insulation and acoustic absorption properties. While gypsum products offer good fire performance, their water resistance needs improvement. Therefore, gypsum board materials are predominantly used for interior applications.
Autoclaved Aerated Concrete (AAC) Blocks and Panels
Today, Autoclaved Aerated Concrete (AAC) blocks are widely utilized in wall material upgrades and building energy-efficiency projects. They offer superior quality combined with excellent thermal insulation properties.
- Features: Exceptional fire resistance and thermal insulation, lightweight with good seismic resistance, high sound insulation, ease of construction, high efficiency, strong compressive strength and bonding adhesion, non-toxic and harmless, eco-friendly and energy-saving, and a long service life.
Flexible Stone (Soft Stone)
Strictly speaking, flexible stone is not a real stone but a flexible, stone-like material. It uses inorganic materials as a base, combined with eco-friendly, water-soluble architectural coatings. Through irradiation cross-linking and baking under a dynamic temperature curve, it is molded into a flexible, thin, and lightweight, new energy-saving, low-carbon architectural decorative surface material. It is a Class A non-combustible material, offering excellent fire resistance and flame retardancy. Flexible stone features three-dimensional textures that realistically replicate the feel of natural stone, providing rich and authentic decorative effects.
2. Metal Panels and Metal Composite Panels
Metal composite panels, also known as sandwich panels, consist of very thin external metal sheets and a low-strength composite core material designed to provide thermal insulation.
A common example is the Aluminum Composite Panel (ACP), which combines aluminum sheets with a polyethylene (PE) core. It retains the desirable characteristics of plastic materials while using metal to overcome their structural shortcomings. ACP features a lightweight profile, strong decorative appeal, and low cost.
Ordinary aluminum composite panels struggle to meet stringent fire safety requirements. However, between 2008 and 2010, Class A fireproof composite panels were developed. During this period, the fire resistance issues of metal composites were resolved, evolving progressively from difficult-to-burn (fire-retardant) and highly flame-retardant grades, all the way to Class A fireproof ratings, resulting in the birth of non-combustible metal composite panels.
The flame-retardant level of the core material is the decisive factor determining the fire performance of curtain wall panels. ACPs manufactured with low calorific value flame-retardant core materials not only meet the structural performance requirements of building curtain walls but also resist rapid burning, oxidation, and deformation during a fire. This significantly improves upon polyethylene’s tendency to soften and form molten drops when heated. Even if the core softens, the low proportion of polyethylene and the low heat value of the core make it difficult to ignite, thereby drastically reducing the product’s fire hazard.
Anodized Non-Combustible Core Composite Panels
Anodizing is a highly effective surface treatment process for aluminum panels. Through an electrolytic oxidation process, a high-hardness oxide film is formed on the surface of the aluminum. This provides excellent wear resistance, durability, and corrosion resistance. Utilizing a “sandwich” structure and a hot-pressing process, the thick anodized aluminum sheet, the aluminum backing sheet, and the fireproof core material are integrated into a single unified panel.
Material Features:
- Metallic luster with a premium texture.
- The continuous anodizing process ensures uniform decorative effects with no obvious color variation.
- The surface metal film offers ultra-weather resistance, is antibacterial, mildew-proof, and easy to clean.
- Surface hardness reaches 9H (sapphire-level hardness), providing excellent scratch and wear resistance.
- Superior weather resistance, guaranteed not to fade for 50 years, lasting as long as the building itself.
- Fire performance reaches the Class A Non-Combustible rating (A2-s1, d0, t0).
- Can be perforated; however, custom-shaped processing is slightly less flexible than single-layer aluminum panels.
- Suitable for large-format panel installations, ensuring exceptional flatness.
- High cost-effectiveness.
3. Fire-Rated Boards
Fire-rated boards are fire-resistant building materials primarily used for surface decoration. They are manufactured in high-temperature and high-pressure environments by impregnating base papers (such as titanium dioxide paper and kraft paper) with melamine and phenolic resins.
Features: Vibrant colors, diverse edge-banding options, and excellent resistance to wear, high temperatures, scratches, and liquid penetration. They are easy to clean, moisture-proof, fade-resistant, offer a refined tactile feel, and are highly cost-effective. As flat panels, however, they cannot replicate three-dimensional embossed or metallic visual effects.
The market offers a wide variety of fire-rated boards. Depending on the materials and manufacturing processes, these boards differ significantly in fire endurance, moisture resistance, structural strength, installation complexity, and environmental safety. Selecting the wrong material not only wastes budget but can also bury severe safety hazards within a project. Below are the most common types of fire-rated boards:
a. Mineral Wool Boards / Glass Wool Boards
Made primarily from slag wool or glass wool, these boards are lightweight and offer excellent acoustic and thermal insulation. Their fibrous structure naturally provides superior sound absorption, making them highly suitable for noise-sensitive ceiling applications. However, their critical flaw is exceptionally poor structural strength—they dent easily upon impact and cannot support heavy hanging objects. More importantly, installation generates dust that irritates the respiratory tract, requiring strict sealing post-installation to prevent airborne fiber health risks. Not recommended for residential use; they can be selectively used for commercial suspended ceilings.
b. Standard / Fiber Cement Boards
Using cement as the base material reinforced with fibers, these boards are non-combustible, moisture-resistant, and possess high strength. They offer top-tier waterproofing at a low cost, making them highly suitable for outdoor siding or basement walls. While traditional standard cement boards are incredibly heavy, labor-intensive to transport, and generate massive amounts of dust (like a sandstorm) during cutting, their biggest risk is a tendency to experience explosive spalling under high heat. Therefore, selecting the fiber-reinforced type is essential for structural reliability. Highly recommended for industrial-style exteriors or moisture-prone substrates.
c. Perlite Boards / Vermiculite Boards
Filled with expanded perlite or vermiculite and bonded with cementitious materials, these boards are lightweight and highly porous. They boast an incredibly low dead load—making them very structural-load-friendly—and provide top-tier fire and thermal insulation (equivalent to the EU Class A1/A2 non-combustible standards). However, their “brittle” nature is a distinct disadvantage. The texture resembles hard bread, resulting in extremely poor nail-holding power; driving a nail often causes the surrounding area to crumble and crack. They also suffer from high attrition rates during transport (prone to chipped corners). Suitable only for non-load-bearing partition walls; never use them in structural applications or areas requiring frequent drilling.
d. Fire-Rated Gypsum Boards (Fire-Resistant Plasterboards)
Featuring a gypsum core infused with glass fibers and sandwiched between heavy-duty paper facings, these boards release crystallized water to delay temperature rise during a fire. They are the absolute mainstream choice for residential ceilings, but water resistance is their fatal flaw. They are budget-friendly, easy to cut (requiring only a utility knife), and eco-friendly. The fire-retardant mechanism—absorbing heat through the evaporation of crystallized water—is highly effective. Caution: Standard gypsum boards on the market are not fireproof; buyers must specifically verify the “fire-rated” classification (typically meeting EU Class B or German B1 flame-retardant standards). They are extremely vulnerable to water and should not be used in bathrooms or basements; moisture causes them to mold, soften, and lose their grip on the framing keels.
e. Fiber-Reinforced Calcium Silicate Boards
Made from siliceous and calcareous materials reinforced with fibers and cured through high-temperature autoclaving, these boards feature a moderate density. They are the “comprehensive all-rounders” of building materials, albeit at a slightly higher price point. They perfectly combine the lightweight nature of gypsum boards with the moisture resistance of cement boards. Their fire performance reaches the EU Class A1/A2 non-combustible standard, coupled with high structural strength and deformation resistance. The surface accommodates various paint finishes, making them exceptionally popular for office partitions and hospital walls. The minor downsides are a relatively brittle surface, high-gloss finishes that are less vibrant than those of HPL, and the need for specialized saw blades during cutting. If budget permits and you want a foolproof solution for both moisture and fire resistance, this is an excellent choice.
f. Magnesium Oxychloride Boards / Magnesium Oxide (MgO) Boards
Pressed from magnesia cementitious materials (magnesium oxide, magnesium chloride) and reinforced with fiberglass mesh, these are absolute performance monsters, but market quality is highly inconsistent. Their fire rating easily hits the EU Class A1 non-combustible standard, producing virtually no smoke or toxicity under fire. They boast extreme strength (can be directly nailed and sawed) and outclass gypsum boards in water and moisture resistance. The biggest pitfall lies in substandard products (with excessive chloride ions) that suffer from a phenomenon known as “moisture absorption and halogen leaching” (often causing a sweating effect). These inferior boards form water beads on the surface, corrode iron nails and structural framing, and produce white efflorescence. Buyers must strictly source from top-tier, reputable manufacturers. Highly suitable for basements, kitchens, and bathroom walls.
g. High-Pressure Laminate (HPL) Decorative Fire-Rated Boards
These feature a core of multiple kraft paper layers impregnated with phenolic resin, topped with a decorative surface layer impregnated with melamine resin, all formed under high heat and pressure. Aesthetically, they are the industry ceiling, but buyers should not blindly trust them to block massive fires. Favored for hotel lobbies and premium cabinet panels, they offer endless patterns and textures while being highly wear-resistant, scratch-resistant, and stain-resistant. However, they remain inherently organic materials. Even with added flame retardants, they typically only reach EU Class B/C (equivalent to German B1 flame-retardant) and fall short of the non-combustible grade. Under sustained intense fire, they will char. Note that their edges are extremely brittle; poor cutting and edge-banding craftsmanship will immediately cause chipping and peeling, demanding highly skilled installers.
h. Polyurethane (PU) Composite Panels / Rock Wool Sandwich Panels
These panels consist of two metal facing sheets (like color steel) with a sandwich core of either PU or rock wool. You cannot have both maximum thermal insulation and maximum fire resistance simultaneously—check the core material carefully before purchasing. They are frequently used in cold storage, cleanrooms, or prefabricated modular buildings. If the core is rock wool, the fire rating reaches EU Class A1/A2 non-combustible while providing decent insulation. If the core is PU, the thermal insulation is top-tier, but the material generally falls into EU Class E or F (combustible). It only reaches Class C (flame-retardant) with added fire retardants. When procuring, always request test reports to verify the core grade; numerous engineering fire accidents have occurred because combustible PU cores were mistakenly utilized as fireproof panels.
4. Foam Glass (Cellular Glass) and Fire-Rated Glass
Foam glass, also known as cellular glass, is a new type of inorganic thermal insulation material. It uses glass as the primary raw material, mixed with an appropriate amount of foaming agent. It is then heated and baked in a high-temperature tunnel kiln, followed by an annealing and cooling process. This manufacturing method creates a uniform structure of independent closed-cell pores.
Today, specialized fire-rated glass is also widely available. Its primary function during a fire is to control the spread of flames and block smoke, serving as a measure-oriented passive fire protection material. Processed and treated using specialized techniques, this specialty glass can maintain its structural integrity and thermal insulation during mandatory fire resistance tests. Of course, standard glass itself also possesses certain inherent non-combustible properties.
5. Fire-Retardant Wood
In common knowledge, wood is a highly combustible material. However, through specialized treatments, timber can achieve a significant degree of fire resistance.
Carbonized Wood (Thermally Modified Timber)
Originating in Europe, carbonized wood is widely utilized in outdoor architectural applications. Without relying on any chemical additives, the wood undergoes a homogeneous thermal carbonization process at extremely high temperatures. This treatment gives the wood surface a rich, textured grain effect while providing excellent rot resistance. Commonly used wood species include Douglas Fir, Red Pine, Cedar, and Mongolian Pine.
Based on the carbonization process, it is divided into two main categories: surface-charred wood and deeply carbonized wood. By deliberately using fire or high temperatures to break down the wood fibers, a carbonized protective layer is formed. Compared to ordinary, untreated timber, the fire performance of carbonized wood is notably improved.
High-Pressure Thermosetting Wood Fiber Boards (Exterior Compact Laminates)
High-pressure thermosetting wood fiber boards are composite panels formed by curing and bonding a wood fiber core with a decorative surface layer under high-temperature and high-pressure conditions. It is a high-tech, green, and eco-friendly decorative wall panel for building facades.
These panels can adapt to a variety of outdoor environments, featuring excellent waterproofing, UV resistance, acid and alkali corrosion resistance, and overall weatherability. The physical properties of the panels are highly stable, typically achieving a Class B1 (flame-retardant) fire rating. The installation of high-pressure thermosetting wood fiber boards requires the implementation of a ventilated rainscreen system, meaning a ventilation cavity (air gap) must be strictly maintained between the cladding panels and the insulation layer.
6. Fire-Retardant Plastic Materials
Fire-retardant plastics are primarily utilized in electrical appliances that generate high thermal energy and operate at high temperatures, such as printers and heat guns. Their fire-resistant ratings are typically achieved by modifying the base resins or incorporating specific filler materials. Common additives include fiberglass and calcium carbonate, which are mixed with the resins in precise proportions and injection-molded to produce flame-retardant plastic components.
The UL 94 flammability standard is the most widely adopted benchmark for evaluating the flammability of plastic materials. It assesses a material’s ability to extinguish a flame after being ignited. Evaluation methods depend on multiple criteria, including the burning rate, burning duration, drip resistance, and whether the dripping molten particles are actively burning. A single tested material may receive various classification values depending on its color and thickness. When selecting a material for a specific product, its UL rating must correspond to the specific wall thickness of the plastic part. The UL rating must always be reported alongside the thickness value; stating a UL rating without specifying the thickness is insufficient and invalid.
Flame-Retardant Classifications for Plastics
The flame-retardant classifications for plastics increase sequentially from HB, V-2, V-1, V-0, 5VB, to 5VA:
HB
The lowest flame-retardant rating in the UL 94 standard. For specimens with a thickness of 3 to 13 mm, the burning rate must be less than 40 mm per minute; for specimens thinner than 3 mm, the burning rate must be less than 70 mm per minute, or the flame must extinguish before reaching the 100 mm mark.
V-2
After subjecting the specimen to two 10-second flame applications, the afterflame and afterglow must extinguish within 60 seconds. Flaming drips are allowed to ignite surgical cotton placed below the specimen.
V-1
After subjecting the specimen to two 10-second flame applications, the afterflame and afterglow must extinguish within 60 seconds. Flaming drips must not ignite the cotton.
V-0
After subjecting the specimen to two 10-second flame applications, the afterflame and afterglow must extinguish within 30 seconds. Flaming drips must not ignite the cotton.
5VB
After subjecting the specimen to five 5-second flame applications, the afterflame and afterglow must extinguish within 60 seconds. Flaming drips must not ignite the cotton. Plaque specimens are allowed to exhibit burn-through (a hole).
5VA
After subjecting the specimen to five 5-second flame applications, the afterflame and afterglow must extinguish within 30 seconds. Flaming drips must not ignite the cotton. Plaque specimens are strictly not allowed to exhibit burn-through.
Because most plastics achieve flame retardancy through the addition of chemical flame retardants during the molding process, extreme attention must be paid to the relevant regulatory and compliance requirements of the final product. The majority of chemical flame retardants contain varying degrees of hazardous or toxic substances. Therefore, when a product demands fire-retardant properties, manufacturers must concurrently evaluate and ensure compliance with environmental and safety regulations (such as RoHS or REACH) during the production process.
7. Other Fire-Resistant Materials
Fire-Resistant Soft Porcelain (Modified Clay Materials – MCM)
This product is composed of inorganic powders—such as natural soil, stone powder, sand, and recycled cement blocks—combined with specific modifiers, achieving a density of 2,327 kg/m³. Upon testing, the product’s fire performance meets the requirements of Class A, with additional classifications satisfying the s2, d0, t0 criteria. Evaluated against the GB 8624-2006 standard, its overall fire performance achieves the Class A2-s2, d0, t0 rating.
Firestop Mastic (Fire-Resistant Putty / Sealant)
Firestop mastic, also known as organic firestop putty, uses organic synthetic resins as a binder, mixed with fire-retardant agents and fillers through a rolling process. This putty is non-hardening and highly moldable, allowing it to be shaped arbitrarily for sealing purposes. It is primarily applied in through-penetration firestop systems for building pipes, wires, and cables, often used in conjunction with inorganic firestop mortars and firestop pillows. Inorganic firestop material is a gray powder that, when mixed with water, is used to seal cable penetrations or build firestop walls in cable tunnels. This firestop mortar is non-toxic and odorless, offering excellent water and oil resistance alongside a simple installation process. With an Oxygen Index (OI) of 100, it is classified as a non-combustible material, providing a fire resistance rating of up to 3 hours or more. For permanent engineering applications, using inorganic firestop mortar not only saves project costs but also ensures structural durability.
Composition:
- Inorganic Binders: Primarily water glass (sodium silicate), gypsum, phosphates, cement, etc.
- Refractory Mineral Fillers: Alumina, asbestos powder (Note: Often replaced in modern eco-friendly materials), calcium carbonate, perlite, and titanium dioxide.
- Flame-Retardant Organic Resins: Mainly PVC, perchlorovinyl, chlorinated rubber, neoprene emulsion, epoxy resin, and phenolic resin.
- Flame-Retardant Additives: Primarily organic compounds containing phosphorus, halogens, or nitrogen (e.g., chlorinated paraffin, tributyl phosphate, decabromodiphenyl ether), and inorganic compounds based on boron (boric acid, zinc borate, aluminum borate), antimony, aluminum, or zirconium.
Firestop Pillows (Firestop Bags)
Firestop pillows are primarily used for fire-sealing various cable penetration holes in industries such as power, telecommunications, petrochemicals, construction, and marine vessels. They effectively prevent flames from spreading along cable routes, maximizing the protection of life and property. At normal temperatures, the product is highly breathable, resistant to acids, alkalis, water, and oil, lightweight, and easy to install. When exposed to fire, it rapidly intumesces (expands) and chars to form a fire barrier of considerable thickness and strength. During this expansion and charring process, it absorbs heat and releases non-combustible gases to block fire, heat, and smoke. It is an ideal fire-retardant product for power cable facilities.
Fire-Retardant Coatings (Intumescent Coatings)
Fire-retardant coatings are specially formulated protective paints, typically solvent-based, composed of chlorinated rubber, paraffin, and various fire-retardant additives. They offer excellent fire resistance. When applied to the surface of ordinary cables and exposed to fire, the coating rapidly intumesces to produce a foam/char layer up to 200 mm thick. This carbonized protective layer completely isolates the fire source. It is highly suitable for the fire protection of indoor and outdoor cable lines in high-grade facilities such as power plants and substations.
Conclusion
Selecting the appropriate fire-resistant building materials is a critical decision that directly determines the safety, compliance, and longevity of any construction project. As we have explored, the mechanisms and performance of these materials vary significantly. While options like fire-retardant plastics, treated wood, and specialized coatings serve important roles in specific niches, structural and architectural safety relies heavily on the foundation of the building itself.
For core building elements, choosing the right substrates, such as inherently non-combustible cement boards or mineral-based panels, forms the first line of defense against fire hazards. Furthermore, the application context matters immensely. Materials chosen for interior decorative wall panels—where aesthetics and low toxicity are paramount—will differ in specifications from those selected for durable, weather-resistant exterior wall panels.
Ultimately, understanding the specific fire ratings (such as the UL 94 standard or EU Class A/B ratings) and the physical properties of each material is essential. By making informed choices, architects and contractors can construct safer, more resilient buildings that effectively protect both life and property in the event of a fire emergency.