Our Guide to Structural Steel Fire Protection

Structural steel fire protection is a critical part of passive fire protection in modern buildings. Steel is strong, durable, and widely used in commercial and industrial construction, but it can lose strength quickly when exposed to high temperatures. Without suitable protection, loadbearing steel columns, beams, and frames may weaken during a fire, which increases the risk of structural failure.

To prevent this, buildings often require specialist fire protection for structural steel. This can include intumescent coatings, board systems, spray-applied materials, and other structural fireproofing systems that are designed to help steel retain its loadbearing capacity for a defined period.

In this blog, we delve deeper into structural steel fire protection, exploring specifically what it is, why it matters, and some key factors to consider when choosing the right system for your building.

What is structural steel fire protection?

Structural steel fire protection refers to the systems and materials used to protect steel columns, beams, frames, and other loadbearing elements from the effects of fire. These systems are designed to insulate the steel and slow the rate at which it heats up.

Steel itself is non-combustible, but that doesn’t mean it’s unaffected by fire. As temperatures rise, steel can lose a significant amount of its strength. If unprotected steel reaches critical temperatures during a fire, it may no longer be able to support the loads it was designed to carry.

That’s where structural fireproofing systems come in. These systems help maintain the loadbearing capacity of structural steel for a specified time, such as 30, 60, 90, or 120 minutes. The required period will depend on the building type, height, use, occupancy, and fire strategy.

Essentially, structural steel fire protection helps give occupants more time to evacuate, supports fire service intervention, and reduces the risk of progressive structural failure.

Why is structural steel fire protection important?

Steel performs very well in construction, but it’s vulnerable to extreme heat. During a fire, unprotected steel can heat rapidly, especially where beams and columns are exposed. As the temperature increases, the steel begins to lose its ability to carry load, which can affect the stability of floors, roofs, and the overall frame.

This makes fire protection of steel structures essential for life safety and building resilience. If the steel frame remains stable for longer, the building has a better chance of maintaining safe escape routes and reducing the risk of collapse.

It’s also important for:

• Protecting life safety – structural steel fire protection supports safe evacuation. If structural elements remain stable for the required fire resistance period, occupants have more time to leave the building safely.
• Maintaining structural integrity – protecting the core framework of a building helps prevent structural failure during a fire, particularly in large commercial, industrial, or multi-storey buildings.
• Supporting compliance – in England, fire safety guidance is set out in Approved Document B, which includes provisions around fire resistance and structural elements. For property owners, contractors, and developers, this reinforces the need to choose tested, appropriate, and properly documented fire protection for structural steel in buildings.

Ultimately, structural steel fire protection isn’t just about meeting compliance requirements, it’s about protecting the people inside the building, preserving critical structural stability, and ensuring the wider fire safety strategy performs as intended when it matters most.

What requirements should be considered for structural steel fire protection?

Structural steel fire protection must be designed and installed in line with the building’s fire strategy, relevant regulations, and applicable test evidence. The exact requirements will depend on the project, but there are several key areas to consider, including:

Approved Document B

As we’ve briefly mentioned, Approved Document B provides fire safety guidance for meeting the functional requirements of the Building Regulations in England. It covers areas including means of escape, internal fire spread, external fire spread, and access and facilities for the fire service. For structural steel, the key issue is ensuring that loadbearing elements achieve the required period of fire resistance.

Fire resistance classifications

Approved Document B now uses the European classification system for fire resistance, set out in BS EN 13501-2 to 4. Fire resistance is expressed in terms such as loadbearing capacity, integrity, and insulation. For structural frames, beams, and columns, loadbearing capacity is a key performance requirement.

Relevant test standards and evidence

Structural fireproofing systems should be supported by relevant test data and system-specific evidence. Depending on the system, this may include European fire resistance testing such as BS EN 13381, along with appropriate classification reports and manufacturer installation guidance. Historic BS 476 evidence may still be encountered, but the regulatory direction is increasingly moving towards European classifications, which makes current test evidence and documentation especially important.

Competent specification and installation

The performance of any system depends on correct specification and installation. A coating, board, or spray system must be suitable for the steel section, required fire rating, site conditions, and final use of the building. Incorrect thicknesses, poor surface preparation, incompatible products, or missing documentation can all compromise compliance.

Wider regulatory attention on building safety and structural fire protection has increased in recent years, particularly under the Building Safety Act environment. This has placed greater emphasis on traceability, competent workmanship, and reliable fire safety information throughout the project lifecycle.

Common methods of fire protection for structural steel in buildings

There are several common methods of fire protection for structural steel in buildings, each with their own advantages and limitations. The best choice depends on numerous factors including the project requirements, the building environment, and whether the steel will be visible or concealed.

Some of the most common steel structure fire protection examples include:

Intumescent coatings

Intumescent coatings are one of the most widely used methods of structural steel fire protection, particularly where the steel is visible as part of the architectural design.

These coatings look similar to paint when applied, but they react when exposed to high heat. During a fire, the coating expands to form a protective insulating char around the steel. This slows heat transfer and helps the steel maintain its loadbearing capacity for longer.

Intumescent coatings are often chosen for:

• Commercial offices
• Retail environments
• Public buildings
• Exposed architectural steelwork
• Projects where appearance matters

They’re popular because they can provide fire resistance while preserving the appearance of the steel. They can also be finished with decorative topcoats, making them suitable for modern buildings where structural steel is intentionally left visible.

However, intumescent systems require careful surface preparation, correct dry film thickness, suitable environmental conditions, and accurate quality control. The finished coating must match the tested system specification to perform correctly.

Board systems

Board systems involve encasing structural steel in fire-resistant boards. These boards provide insulation by physically separating the steel from heat and fire exposure.

They’re often used where steelwork is hidden within walls, ceilings, service areas, or plant spaces. Board systems can be particularly effective where a robust, impact-resistant, and clearly defined system is required.

Board systems are typically found in:

• Commercial buildings
• Industrial units
• Plant rooms
• Service areas
• Car parks
• Concealed structural zones

One of the main advantages of board systems is consistency. Because the boards are manufactured to a defined specification, they can offer a controlled and predictable level of protection when installed correctly. They can also be a strong option where durability and mechanical protection are important.

The trade-off is that board systems may be less suitable where the steel is intended to remain visually exposed. They can also require more space around the steel section, which needs to be considered during design.

Spray-applied systems

Spray-applied structural fire protection involves applying a fire-resistant material directly onto steelwork. These systems are often used on large-scale projects where speed and coverage are important.

Spray systems can be cementitious or mineral fibre based and are typically used where steelwork is hidden from view. They can be especially useful for complex steel arrangements where board cutting and detailing would be more time-consuming.

Spray-applied systems are often suitable for:

• Warehouses
• Industrial buildings
• Large commercial structures
• Basements
• Car parks
• Back-of-house structural areas

They can offer fast application across large steel areas, making them practical for industrial and commercial projects. However, finish quality is generally more functional than decorative, so they’re less commonly used where steel is exposed within the final design.

As with other systems, correct application thickness, substrate preparation, curing, and protection from damage are essential.

Which structural fireproofing system is right for you?

Choosing the right structural fireproofing system depends on more than simply selecting a product. The correct solution should be based on fire strategy, building use, design intent, and long-term maintenance requirements.

Some key factors to keep in mind when choosing the right structural fireproofing system include:

• Appearance and finish – if steelwork is visible, intumescent coatings are often preferred because they can maintain a clean architectural appearance. Where the steel is concealed, board or spray systems may be more practical.
• Speed of installation – spray-applied systems can be efficient across large areas, particularly on industrial sites. Board systems may take longer in complex areas but they offer a neat, robust finish. Intumescent coatings may require more preparation, drying time, and quality checks.
• Durability – board systems can offer good durability in concealed or high-impact areas. Intumescent coatings may require protection from moisture, abrasion, or impact depending on the environment. Spray systems may need additional protection in areas exposed to damage.
• Exposed or hidden steel – exposed steel usually requires a more visually acceptable solution, such as intumescent coating. Hidden steel gives more flexibility and may allow for board or spray-applied systems.
• Maintenance considerations – some systems are easier to inspect and maintain than others. Coatings may require periodic checks for damage or deterioration, while board systems need inspection to confirm they remain intact and properly fixed.
• Project type – for commercial offices and public buildings, appearance and finish may be key. For industrial buildings, warehouses, and back-of-house areas, speed, robustness, and cost efficiency may be more important.

Ultimately, the right system should be specified by competent specialists, like Fire Industry Specialists (FIS), who understand both fire performance and practical site conditions.

Get in touch with our specialists for expert advice

Structural steel fire protection is an essential part of keeping buildings safe, compliant, and structurally stable during a fire. Whether your project requires intumescent coatings, board systems, spray-applied protection, or a combination of different structural fireproofing systems, the right solution depends on your building, its fire strategy, and its long-term use.

At Fire Industry Specialists, we provide expert advice and installation for fire protection of steel structures across commercial and industrial buildings. Our team can help you assess your requirements, choose the right system, and ensure installation is completed to the correct standard.

If you need support with structural steel fire protection, get in touch with our team today to discuss your requirements in more detail or to arrange a project assessment.