08.09.2026
At room temperature steel is an extremely strong building material; but when it reaches around 500–600°C in a fire, it loses most of its load-bearing capacity and can deform and collapse in a relatively short time. The job of fire-resistant (intumescent) coatings is to delay this temperature rise so the structure stays standing during the first minutes that are critical for evacuation and firefighting.
How It Works
Under normal conditions an intumescent coating is a thin layer of a few millimetres. When it comes into contact with fire or with heat above a certain temperature, it reacts chemically and swells to many times its thickness, turning into a foam-like, porous char layer. This layer has low thermal conductivity and insulates the steel surface from the heat — delaying the moment the steel reaches its critical temperature.
Fire Resistance Ratings
Systems are applied to provide different resistance times depending on the load carried by the protected member and the use of the building — usually in 30, 60, 90 and 120 minute classes (expressed in Europe with codes such as R30/R60/R90/R120 under EN 13501-2). The thicker the dry film, the longer the protection; that is why applying the correct thickness is decisive in actually meeting the rating the project requires.
Not Only on Steel
Contrary to common belief, these systems are not limited to structural steel: timber surfaces (especially in the restoration of historic buildings), fire doors and partition wall systems, cable trays and ventilation ducts, and high-occupancy buildings such as hotels, hospitals, shopping malls and schools.
Application Process
For a durable result that matches its certification, the order matters: first surface preparation (by sandblasting on steel), then a compatible primer, then the intumescent intermediate coat and, where needed, a decorative/protective top coat. The dry film thickness of every coat is measured to make sure the rating targeted in the project is achieved.