How intumescent coatings work during a fire protection event
Unlike decorative paints, intumescent coatings are formulated to react when exposed to high heat. Rather than burning away, the coating expands many times beyond its original thickness, creating a protective carbonaceous char that acts as an insulating barrier.
This intumescent layer reduces heat transfer through the coating system, helping the underlying steel, metal or timber remain below its limiting temperature for longer. By slowing the rise in temperature, the coating helps preserve the mechanical properties of the substrate and maintain structural stability during a fire.
Modern fireproof coatings are designed for reliable performance while remaining straightforward to apply. Depending on the product specification, they can be typically applied by brush, roller or spray, either on site or during off site application before installation.
Choosing intumescent paint for steel fire protection
One of the most common applications is intumescent paint for steel. Although steel is non-combustible, it begins to lose strength as temperatures rise, with its mechanical properties reducing rapidly once it reaches around 500°C. Without suitable fire protection, a steel element can lose its ability to support the structure, increasing the risk of structural collapse.
Applying intumescent paint for steel provides effective steel protection by delaying the rate at which heat reaches the substrate. The expanding intumescent layer forms a protective barrier around each steel member, helping maintain structural integrity and allowing the load bearing frame to continue performing for longer.
Selecting the correct coating system depends on several factors, including the required fire rating, the section factor of the structural steel, the intended environment, and whether the work will be completed on site or by off site application. The required dry film thickness, often referred to as dry film thickness DFT, must be achieved to adequately protect the steel. Applying the coating in multiple layers or thin layers, depending on the manufacturer's guidance, helps achieve the specified dry film thickness without affecting the finish.
For long-term performance, many systems also include compatible primers that provide corrosion protection, followed by a decorative topcoat layer where required. Following the specified drying times between coats helps maintain the integrity of the complete system.
For projects requiring specialist solutions, consider products such as:
- Bollom Flameguard Steel Fire Protection Paint
- Thermoguard Steel Fire Protection Systems
- Nullifire SC802 Intumescent Basecoat - 60 Minutes
- Sherwin Williams Firetex M90/02 Epoxy Intumescent
- Jotun Steelmaster 600WF
Using intumescent paint for wood fire resistant protection
Intumescent paint for wood offers an effective way to improve the fire resistant performance of timber used in both domestic and commercial building projects. When exposed to high heat, the coating expands to form a protective carbonaceous char layer, slowing heat transfer into the wood and helping preserve the substrate for longer.
These intumescent coatings are commonly used on fire doors, wall panelling, staircases, exposed beams and other timber features where additional fire protection is required. While the coating helps improve fire performance, it also allows the appearance of the timber to be maintained when used with an approved decorative finish.
As with steel, good surface preparation is essential. The surface should be clean, dry and free from grease, dust and loose material before application. Applying the coating to the correct dry film thickness ensures it performs as tested, while the use of compatible primers or finishing products, where specified, helps maintain the performance of the complete system.
If you require intumescent paint for wood, Promain Paints stocks trusted systems suitable for a wide range of timber applications, whether you're working on site or preparing components for off site installation.
Selecting the right intumescent paint solution for fire rating and corrosion protection
Every building has its own fire safety requirements, so selecting the right Intumescent paint UK product is an important part of any passive fire protection strategy. The correct coating system should provide the required fire rating while remaining suitable for the environment, substrate and method of application.
There are several factors to consider before choosing a product. These include whether the coating is being applied to structural steel, wood or another approved substrate, whether the work is carried out on site or through off site application, the required period of fire resistance, expected weather conditions for external work, and any long-term environmental conditions the coating will face.
For paint for steel, the section factor of each steel member plays an important role in determining the required dry film thickness. The specified dry film thickness DFT must be achieved to allow the intumescent layer to perform as tested during a fire. Using the correct compatible primers, followed by an approved topcoat layer where required, also helps provide corrosion protection, improves durability, and ensures the complete system delivers the same protection throughout its service life.
Our technical team can help specify the right intumescent coatings for your project, making sure every component works together as intended. From selecting the correct primer through to the finishing coat, we'll help you choose products that comply with the manufacturer's specification and the required fire rating.
Intumescent paint colours and decorative fire resistant finishes
Many people assume intumescent paint is only available in white, but modern fireproof coatings offer far more flexibility. Depending on the manufacturer, many systems can be finished with an approved decorative topcoat layer, allowing you to achieve the appearance you want without affecting the coating's fire protection performance.
Whether your project calls for a clean architectural finish, coloured decorative paints, or a more industrial appearance, there are suitable systems available for both commercial and residential construction. Using an approved finish also helps protect the intumescent layer from everyday wear and, in some cases, improves resistance to the surrounding environment.
It's important that any finishing coat is approved for use with the selected intumescent paint system. Using an incompatible product may affect the coating's performance and could invalidate the tested specification.
Surface preparation, dry film thickness DFT and fire protection performance
Good surface preparation is one of the most important parts of any intumescent paint installation. Whether you're protecting steel, metal or timber, the substrate should be clean, dry and free from contamination before application.
For structural steel, the correct primer should already be in place where specified. Using compatible primers not only improves adhesion but also provides valuable corrosion protection beneath the intumescent coatings. On timber, the surface should be free from dust, grease and any loose or failing coatings before work begins.
Applying the correct dry film thickness is just as important as choosing the right product. Every coating has a specified required dry film thickness, often referred to as dry film thickness DFT, which has been tested to deliver a particular fire rating. Applying too little material may not adequately protect the substrate during a fire, while excessive build can affect appearance, drying times, and the performance of the complete coating system.
Most intumescent coatings are applied in multiple layers, allowing the required film build to be achieved consistently. Following the manufacturer's guidance on application methods, drying times, environmental limits and overcoating intervals helps ensure the finished system performs as intended throughout its service life.
Why professional advice makes a difference for intumescent coatings
Fire protection products are highly specialised, and choosing the wrong specification can lead to unnecessary cost, delays and compliance issues. Every project is different, and selecting the right intumescent paint, primer, decorative finish and application method requires careful consideration of the substrate, fire rating, environmental conditions and intended use.
At Promain Paints, we work with leading manufacturers to supply high-quality intumescent coatings for structural steel, wood, metal and other approved substrates used in modern construction. Whether your project involves commercial buildings, residential developments or industrial facilities, we can recommend a coating system that provides dependable fire protection while also delivering long-term corrosion protection where required.
Our experienced technical team can also advise on off site application, on site installation, section factor calculations, required dry film thickness, surface preparation, compatible primers and approved finishing coats. By selecting the correct products from the start, you can help maintain structural stability, protect load bearing elements, and ensure the building achieves the required level of passive fire protection.
Intumescent paint performance and fire protection standards
Intumescent paint is independently tested to recognised standards, including BS 476 and BS EN 13381, to confirm its performance as part of a passive fire protection system. When applied to the correct required dry film thickness (DFT), these intumescent coatings can provide a fire rating of 30, 60, 90 or up to 120 minutes, helping to protect structural steel, maintain structural integrity, and support safe evacuation during a fire. The specified dry film thickness DFT must always comply with the relevant test standard and the manufacturer's guidance.
Types of intumescent coatings
There are several types of intumescent coatings available, each designed for different environments and project requirements. Water based systems are widely used for internal applications as they are lower in odour, more environmentally friendly and often more cost effective. Solvent based products are suitable for a broader range of environmental conditions, while epoxy based fireproof coatings are commonly chosen where greater durability and protection are required. Some hybrid intumescent coatings also offer faster curing times and can achieve the required protection in a single layer, helping to reduce application time on certain projects.
Application and surface preparation
Correct surface preparation is essential for any intumescent paint system to perform as tested. For steel, preparation should follow the SA 2.5 Swedish Standard before applying the specified primer, intumescent layer, and any approved topcoat layer. Applying the coating to the correct dry film thickness is critical to achieving the required fire protection. Compared with alternative methods of protecting structural steel, intumescent paint is often less disruptive to install, can be applied off site or on site, and is frequently a more cost effective solution while delivering the same level of certified fire protection.
Buy quality intumescent paint from Promain Paints
Choosing the right intumescent paint means more than buying a coating. The correct system helps provide reliable passive fire protection, protects load bearing elements, and supports the structural integrity of a building when exposed to high temperatures during a fire.
Whether you need intumescent paint for steel, intumescent paint for wood, specialist primer systems, or complete fireproof coatings for new construction or refurbishment projects, Promain Paints supplies trusted products from leading manufacturers. Our range includes solutions for structural steel, timber and other approved substrates, with technical support available to help you select the most suitable coating system for your application.
We'll help you identify the correct fire rating, calculate the required dry film thickness where needed, recommend compatible primers, and advise on approved finishing coats to achieve lasting fire protection, corrosion protection, and excellent durability.
Contact our knowledgeable team today for technical advice, product recommendations or assistance selecting the right intumescent paint system. Browse our range online or speak with one of our specialists to find the right solution for your next project.