Thinner-type fire-retardant coatings for steel structures refer to coatings with a thickness greater than 3mm and less than or equal to 7mm, offering certain decorative effects. These coatings exhibit fire resistance with an expansion and thickening to a maximum of 2.5 hours at high temperatures.

These fire-resistant coatings for steel structures are typically made with suitable water-based polymers as the base material, combined with flame-retardant composite systems, fire-retardant additives, and refractory fibers, etc., sharing the same fire-resistant principle as ultra-thin coatings. For such fire-resistant coatings, it is required that the water-based polymers chosen have good adhesion, durability, and water resistance to the steel substrate. They have better decorative properties than thick fire-resistant coatings but are inferior to ultra-thin steel structure fire-resistant coatings, usually with a fire resistance limit of 2.5 hours or less. Therefore, they are commonly used in fire protection projects for steel structures with a fire resistance limit of less than 2.5 hours and are often applied by spraying. They once occupied a significant market share, but with the emergence of ultra-thin steel structure fire-resistant coatings, their market share has gradually been replaced.