Fireproof coatings explained
The need for fireproof coatings
Fireproof coatings often go unnoticed during a project, but in an emergency, they can mean the difference between a safe evacuation and a major structural failure. Fire protection coatings are now seen as essential, working alongside alarms, sprinklers, and compartmentation. Their importance stems from stricter regulations, improved technical data, and a clearer understanding of how quickly unprotected steel and timber can reach dangerous temperatures in a real fire.
In our experience on active sites, projects go more smoothly when fireproof coatings are planned early, specified clearly, and applied by specialists. We are often called in to fix issues where coatings were chosen solely for price, applied like regular paint, and then fail inspection because the dry film thickness is incorrect or the topcoat is incompatible. These problems waste time, create tension between trades, and can leave a building with less fire resistance than expected.
We explain here how modern fireproof coatings work, the differences between intumescent and fire-retardant systems, and how they are tested and certified for steel, timber, and other materials. We’ll also cover how these products fit within UK fire regulations, what to look out for during specification and application, and share real examples of how good fire protection has benefited clients.
Understanding modern fireproof coatings
A fireproof coating is a special type of paint designed to protect the underlying material from heat and fire. Unlike regular paints, these coatings are designed to either form an insulating layer or to slow ignition and flame spread when exposed to high temperatures. The most common types used in commercial and industrial projects are intumescent coatings for steel and timber, and fire-retardant paints for surfaces such as timber linings, plasterboard, and composite panels.
Intumescent fireproof coatings react to heat by swelling to many times their original thickness, typically when temperatures exceed 200 degrees Celsius. This creates a stable, carbon-rich layer that insulates the steel underneath. For example, a 1-millimetre layer can expand to about 50 millimetres during a fire, forming a foam that slows down heat transfer. This delay is significant because unprotected steel can quickly lose its strength once temperatures go above 550 degrees Celsius. Tests to standards such as BS 476 and EN 13381 translate this performance into certified fire-resistance periods of 30, 60, 90, or 120 minutes.
Fire-retardant coatings work differently. Instead of forming a thick layer, they delay ignition by releasing gases that slow burning or by creating a thin insulating layer. These coatings are often used on timber cladding, doors, ceilings, and wall linings to improve the surface's performance in fire tests, rather than to keep the building structure safe for a set period. Many customers find that understanding the difference between structural fire protection and surface flame control is a helpful first step when evaluating options.
Intumescent coatings for structural steel
On the multi-storey commercial and residential projects we work on, intumescent coatings for steel are now standard, not a speciality. UK guidance, including Approved Document B, makes it clear that structural steel must meet certain fire resistance times, and buildings over 18 metres usually need certified intumescent systems as part of their fire plan. The British Constructional Steelwork Association points out that thin-film intumescent coatings are popular because they can provide up to 120 minutes of fire resistance with a good finish, whether applied on-site or off-site, and they do not add much weight to the steel.
Thin-film intumescent systems are usually water or solvent-based and include a primer, a reactive basecoat, and a sealer or topcoat to protect the intumescent layer from moisture and damage. The basecoat is key—it reacts to heat by expanding into an insulating layer that keeps the steel from heating up too fast. Because performance depends on the dry film thickness, manufacturers provide detailed tables showing how much product is needed for each steel size and shape to meet 30, 60, 90, or 120-minute ratings under standards such as BS 476 Part 21 or EN 13381. Our teams spend a lot of time with these tables to ensure the correct fire rating is achievable on site and that the system has the appropriate certification for building control.
We often see problems during installation when there is a gap between what was planned in fire engineering calculations and what is actually built on site. Extra brackets, stiffeners, or services can change the steel’s section factor, which affects the amount of intumescent coating required. When we get involved early, we work with engineers and fabricators to select coating systems that can handle these changes and plan the application. Clients often tell us that this teamwork helps them avoid last-minute design changes or rework when inspectors ask for test evidence and thickness records before the building is handed over.
Fire retardant coatings for surfaces
Intumescent coatings are designed to keep key structural parts cool for as long as possible, while fire-retardant coatings focus on slowing the rate at which flames spread over exposed surfaces. We are often asked whether fire-retardant paint can be covered with regular decorative paint once it has reached the required fire rating. This is possible, but only if you use an approved, compatible topcoat that does not compromise the underlying system's fire performance. When we plan refurbishment work, we always check the compatibility data sheets and, if needed, get written confirmation from the coating manufacturer before adding any decorative topcoats.
Many clients tell us that surface fire protection is more confusing than structural fire protection because it uses different tests and classifications. We help by relating these technical ratings to the goals for each space, such as keeping escape routes safe by limiting fire growth along corridor linings or reducing fire risk in high-risk rooms. This approach helps building owners and facilities managers see how fire-retardant coatings can be a practical way to meet regulations without removing and replacing existing finishes.
Testing, certification and regulations
Current UK building regulations and associated guidance documents make passive fire protection a central part of the overall fire strategy. Commentary on recent regulatory changes highlights that buildings with storeys above 18 metres now face particular scrutiny, with expectations that structural steel will be protected by certified intumescent systems, backed up by documented on-site thickness checks and clear maintenance information for the building owner. Alongside this, the Regulatory Reform Fire Safety Order places ongoing duties on responsible persons to assess fire risk throughout the life of the building, including monitoring the condition of fireproof coatings and ensuring they have not been damaged, removed or compromised by later works.
Clients tell us that meeting regulations is now much more evidence-based. Building control officers, fire engineers, and insurers want to see not just a specification, but also test certificates, product data sheets, installation records, and inspection reports to prove that the installed fire protection matches the tested system. We help by keeping detailed records of wet and dry film thicknesses, using calibrated gauges on-site, and providing handover documents that link each protected part to its specific certification. This level of traceability gives both project teams and end users confidence that their fireproof coatings are a key part of a carefully checked safety system.
Application quality and common pitfalls
Modern fireproof coatings are backed by impressive chemistry and test data, but their real-world performance depends on how well the surface is prepared and how carefully they are applied. Thin-film intumescent coatings especially need the right dry-film thickness across complex steel shapes, which is harder than just putting on a few coats of regular paint.
When we are called to sites after problems arise, we often see the same issues. Sometimes coatings were applied to steel that was not properly cleaned or primed, resulting in poor adhesion and flaking during inspection. Other times, applicators relied on visual inspection of coverage rather than measuring wet film thickness, only to find later that dry-film checks showed the coating was too thin for the required fire rating. Fixing these problems usually means abrasive preparation, reapplying the coating, and re-inspecting, which disrupts other trades and delays the project.
We believe the best results occur when fireproof coatings are treated as a separate trade package, not just part of general decorating. This means setting up inspection and test plans, and allowing enough time for access and curing in the schedule. We also advise clients to consider future maintenance when applying coatings, choosing topcoats and other details that will protect the intumescent layer from damage during normal use and future refurbishments. By focusing on quality from the start, building owners can avoid costly repairs later and trust that the coatings will perform when needed.
Case examples and practical choices
In a recent commercial project, the design team needed 90-minute fire resistance for exposed steelwork in a double-height reception, and the architect wanted a high-quality decorative finish. By working with manufacturer loading tables and mock-up samples, we found a water-based thin-film intumescent system with a tinted topcoat that met the rating, satisfied building control, and gave the client the look they wanted. The key was early coordination between the fire engineer, architect, and contractor, so the system could be built into the design from the start.
In another industrial refurbishment, we needed to improve the fire performance of large areas of existing timber linings in a production area but without stopping operations. We chose a proven fire-retardant coating that provided a strong, easy-to-clean topcoat. To keep downtime low, we scheduled the work around shift patterns and gave clear documentation linking the installed system to test data for future audits and risk checks. This helped meet insurer and regulator requirements without costly and disruptive strip-out work.
For many building owners and project managers, the main decision is how to match fireproof coatings to their needs for safety, schedule, appearance, and budget. When we meet with them, we use real examples to discuss trade-offs, like site-applied versus off-site coatings, water-based versus solvent-based systems, and whether to leave structural elements exposed or covered. These talks often reveal ways to simplify the fire protection plan, such as using fewer certified systems across different areas or coordinating coatings with other passive measures like fire stopping and compartment walls.
Choosing a trusted fireproof partner
Because fireproof coatings are technically and legally complex, many clients now want a partner who can guide them through the choices and deliver a compliant installation, not just a product. We see our job as more than just applying coatings—we help project teams understand what each system does, how it should be applied, and what evidence will be needed at handover and later.
As building safety rules continue to change and there is greater focus on responsibility and accountability, we expect demand for high-quality fireproof coatings to continue rising. From our talks with industry groups and other experts, it’s clear that traceable, well-documented passive fire protection will become a must-have for both regulators and insurers. By choosing experienced contractors and insisting on clear documentation and certified systems, building owners can protect both the people in their buildings and the long-term value of their property.
Safer buildings through better fireproofing
Fireproof coatings are crucial for protecting lives and property. Whether it’s intumescent coatings that keep structural steel safe in a high-rise or fire-retardant paints that slow flames on timber linings, the main goal is the same: gaining extra minutes in a fire so people can escape and firefighters can respond.
In our experience, the best results come from clear design intent, careful selection of certified products, and skilled application with proper inspection and documentation. If coatings are chosen solely for price, applied without following the manufacturer's guidance, or damaged by subsequent work, the building may not have the safety margin everyone expects.
We also notice that early discussions let fireproof coatings fit smoothly with structural plans and the construction schedule, avoiding last-minute compromises. Taking a strategic approach from the start not only lowers risk but is often more cost-effective than making rushed decisions later.
If you are planning a new build, refurbishment, or compliance upgrade and want your fireproof coatings to be both technically sound and practical, we recommend getting in touch. By working together from the start, we can help you define the fire performance you need, choose the right certified systems, and plan installation and inspection that will meet the standards of building control, insurers, and, most importantly, the people who use your building. If you want to explore options, talk about a current project, or review your fire protection, our team is always ready to share practical advice, walk through case studies, and help you create safer, more resilient buildings.