How Fire-Resistant Are Concrete Floors?

Architects and contractors now put fire safety first in construction. They aren’t just checking boxes, and that’s always been the right approach. However, the Grenfell Tower tragedy in 2017 raised serious concerns in the industry. It resulted in new fire safety regulations and changes in building methods. Since then, materials like concrete have been in the spotlight for their fire resistance. People are now more aware of fire risks than ever.

But let’s get something straight: concrete – it’s not just good at holding up buildings; it’s also a fire-fighting hero in its own right. Not that we’re calling concrete a firefighter (though it would look pretty cool in uniform). Concrete is a top choice for architects, contractors, and property owners who care about safety. Its natural fire-resistant properties make it reliable for construction. If you’re in construction, it’s safe to say concrete has your back.

How will evolving fire safety standards shape future construction material choices?

What Concrete Is Made Of & Why It’s Fire-Resistant

Concrete’s fire resistance starts with its ingredients. In short, it’s composed of cement, aggregates (sand, gravel, etc.), and water. Now, none of these ingredients are what we’d call “flammable”. In fact, they’re chemically inert, meaning they don’t easily catch fire, even when exposed to extreme temperatures. This is why concrete floors don’t just burn away in a fire, unlike timber or certain metals that melt faster than ice cream in the sun.

How Concrete’s Ingredients Play a Role in Fire Resistance

1. Cement is made from limestone, clay, and gypsum, all with a high melting point. So, when concrete is exposed to heat, these components don't burn. Instead, they hold their ground and help prevent the spread of fire throughout the building.
2. Aggregates like gravel and sand add bulk and structure to concrete. Most aggregates also naturally resist heat, helping to keep a concrete floor strong during a fire.
3. The water content of concrete plays a pivotal role. When concrete gets hot, the water inside evaporates. This can cause some cracking but also helps control the temperature, stopping the concrete from heating up too fast.

So, while concrete doesn’t win any awards for being “light as a feather,” it’s certainly got what it takes when it comes to fire resistance.

Fire Resistance Ratings & What Concrete Can Handle

Now, it’s important to note that not all concrete is created equal. Concrete’s fire resistance depends on the mix, the reinforcement, and the thickness of the material. Fortunately, there are industry standards that concrete can meet, such as Euroclass ratings and BS 8110. These ratings help architects, engineers, and builders know how much fire exposure a concrete element can take.

Euroclass Ratings

This is the European standard for classifying materials based on their fire behaviour. Concrete usually falls into Euroclass A1 or A2. This means it doesn't burn and won’t help fire spread.

BS 8110

BS 8110, a UK standard, provides guidelines for the fire resistance of concrete structures. For example, it shows how thick a concrete slab should be for fire resistance ratings. Depending on the design, these ratings can range from one to four hours of protection.

If you’re specifying concrete for a project, fire resistance is a key metric you’ll want to check. And don’t worry – concrete has got your back, meeting or exceeding most fire safety regulations.

Comparing Concrete to Other Building Materials

When it comes to fire resistance, concrete has some stiff competition. But let’s be clear: concrete’s fire safety credentials put many other materials to shame. Let’s compare it to steel, wood, and plasterboard – three of the more common building materials.

Concrete vs. Steel

Steel might seem like a strong contender in the fire-resistance game, but don’t be fooled. While steel has a high melting point, it loses its structural integrity at a much lower temperature than concrete. Steel begins to weaken at around 550°C, which is pretty low when you think about how hot a fire can get. Concrete, however, can handle much higher temperatures and still keep its strength. And the best part? Concrete doesn’t expand and distort in the way steel does when heated.

Concrete vs. Wood

Wood, bless its natural beauty, isn’t known for its fire resistance. When exposed to flames, wood catches fire easily and burns rapidly, turning into ash with alarming speed. On the flip side, concrete doesn't burn at all. Instead, it acts as a fire barrier, preventing flames from spreading and giving occupants more time to escape. So, if you want fire safety, you might want to stick with concrete instead of wood for your floors.

Concrete vs. Plasterboard

Plasterboard is often used for fire protection because of its fire-retardant properties, but it can only protect so much. When exposed to fire, plasterboard can melt or dissolve. Concrete lasts longer and keeps its strength and structure, making it a more durable option for resisting fire. In fact, concrete is far superior to plasterboard in terms of long-term fire protection. This is especially the case in large buildings where fire containment is essential.

How Concrete Responds to Fire Exposure

Now, let’s dig into what really happens when concrete is exposed to extreme heat. Concrete, as sturdy as it is, can still experience some issues when subjected to high temperatures. One common issue is spalling. This happens when the outer layers of concrete crack, break off or even explode. It occurs because steam quickly escapes from the water inside the concrete.

What is Spalling?

Spalling occurs when moisture trapped inside concrete turns into steam during fire exposure. As the steam expands, it can cause the outer layers of concrete to break off or explode. This can compromise the concrete's aesthetic quality and weaken its fire resistance. Modern concrete mixes with less moisture and added fibres can lower the risk of spalling, leading to better performance in fire conditions.

Factors Affecting Concrete’s Fire Resistance

Several factors influence how concrete behaves when exposed to fire. These include:

1. Moisture Content

The more moisture in concrete, the greater the risk of spalling. Proper mix design and curing techniques can help reduce moisture content and improve fire resistance.

2. Reinforcement

The type and amount of reinforcement (such as steel bars or fibres) used in the concrete mix play a big role in its performance during a fire. Steel, for instance, can weaken under heat, potentially compromising the concrete’s strength. Yet well-designed concrete mixes with fibres or special reinforcement can handle more heat.

3. Mix Composition

The specific mix of aggregates used in concrete can also impact its fire resistance. Some aggregates may react with heat, while others may enhance the concrete's ability to perform under fire conditions.

Reinforced vs. Non-Reinforced Concrete

As we mentioned earlier, not all concrete mixes are the same. One key distinction in concrete’s fire performance is whether it’s reinforced or unreinforced.

Reinforced Concrete

Reinforced concrete includes steel bars or mesh, which give it extra strength. However, steel reinforcement can lose its strength in high heat. Plus, concrete can crack, which may affect its overall fire resistance. Even so, reinforced concrete is very fire-resistant. It can keep its strength for a long time in extreme heat.

Non-Reinforced Concrete

Non-reinforced concrete doesn't have steel reinforcement. This makes it more fire-resistant than reinforced concrete, as no steel can weaken in a fire. The downside? Non-reinforced concrete is more prone to cracking under stress. However, when it comes to fire resistance, non-reinforced concrete is still a top performer. It provides excellent protection in the event of a fire.

Fibre-Reinforced Concrete

A recent trend in concrete design is using fibres (such as glass, carbon, or polypropylene) in the concrete mix. These fibres help reduce spalling during fire exposure and provide additional structural stability. Fibre-reinforced concrete is a great option for projects requiring high fire resistance.

Fire-Resistant Concrete Mixes & Best Practices

Not all concrete is created equal when it comes to fire resistance. Standard concrete provides good protection, but specialised fire-resistant mixes offer even more. These formulations are designed to withstand extreme temperatures and minimise fire-related damage. Let’s look at some of the most effective options.

Fire-Resistant Concrete Mixes

1. High-Strength Concrete (HSC)

High-strength concrete is denser and more compact than regular concrete. This reduces porosity and makes it less likely to spall. The lower moisture content in HSC also helps prevent explosive steam buildup when exposed to fire. This type of concrete is often used in high-rise buildings and tunnels, where fire resistance is a priority.

2. Lightweight Aggregate Concrete (LWAC)

This mix swaps out standard aggregates for lighter options, such as expanded clay, pumice, or perlite. The result? Concrete has lower thermal conductivity, meaning it slows down heat transfer more effectively. This makes it an excellent choice for fireproofing walls, floors, and structural elements.

3. Calcium Aluminate Cement (CAC) Concrete

CAC-based concrete is formulated explicitly for high-temperature environments. Calcium aluminate cement is different from regular Portland cement. It can withstand temperatures above 1,000°C. This cement is commonly used in fireproof vaults, furnaces, and industries with constant fire risks.

Fire-Resistant Additives & Treatments

Beyond the concrete mix itself, certain additives and treatments can enhance fire performance:

Polypropylene Fibres

When heated, these tiny fibres melt, forming micro-channels. This lets steam escape and lowers the risk of spalling.

Silica Fume & Fly Ash

These materials boost density and heat resistance. This makes the concrete stronger in extreme fire conditions.

Intumescent Coatings

These special coatings get bigger when heated. They create an insulating layer that protects the concrete below.

Choosing the right concrete mix and additives helps builders improve fire resistance. This way, they can keep structural strength intact.

Fire Safety Starts at the Ground Level – Make the Right Choice

Your floors do more than just support the building – they hold the key to fire safety. And when fire protection is non-negotiable, only one material delivers: concrete.

Fire can destroy a building in minutes. However, using the right materials can slow down the spread, save lives, and reduce damage. Concrete is one of the safest and most fire-resistant building materials. It outperforms options like wood, steel, and plasterboard.

If you’re building a commercial property, an industrial site, or a high-rise, fire-resistant concrete is a great choice.

Why Concrete Floors Are a Smart Fire-Resistant Choice

• Concrete stays strong in intense heat, unlike wood that burns or steel that warps.
• Concrete does not conduct heat well. This means it holds heat, which stops flames from spreading quickly through a building.
• The right mix matters. Whether you use fibre-reinforced concrete or lightweight aggregates, it provides better protection.
• Concrete is one of the safest options for fireproof construction. It meets BS 8110 standards and Euroclass ratings.

Don’t take risks when it comes to fire safety. The LGW Group focuses on top-quality, fire-resistant concrete solutions made for your project. Let’s talk about fire-resistant concrete today. Get expert guidance and a custom quote from the LGW Group – because safety starts with the right foundation.

Call 0117 958 2090 now or get in touch to take the first step towards safer, fire-resistant construction.