BS 476-21 Fire Resistance Standard

What is steel structure coating?

Steel structure fire-retardant coating is a type of coating applied in construction engineering. Steel structures typically lose their load-bearing capacity at temperatures between 450°C and 650°C, undergoing significant deformation that causes steel columns and beams to bend. As a result, excessive deformation renders them unusable. Generally, unprotected steel structures have a fire resistance limit of about 15 minutes.

Based on fire protection mechanisms, steel structure fire-retardant coatings are classified into:

a)Intumescent steel structure fire-retardant coating: A coating that expands and foams at high temperatures to form a fire-resistant insulating protective layer. Industry practice often follows older standards, referring to intumescent fire-retardant coatings as a combination of ultra-thin and thin steel structure fire-retardant coatings.

b)Non-intumescent steel structure fire-retardant coating: A coating that does not expand or foam at high temperatures but itself acts as a fire-resistant insulating protective layer. Industry practice often follows older standards, referring to non-intumescent fire-retardant coatings as thick fire-retardant coatings.

According to the product scope defined by the 476-21 standard, steel structure coatings can be tested in accordance with the 476-21 standard.

Refer to the 476-21 product scope:

BS 476-21 is primarily used to evaluate the fire resistance of load-bearing building materials under high-temperature conditions. It is mainly applied to determine the load-bearing capacity, integrity, and thermal insulation of materials such as beams, flooring, ceilings, and walls under high-temperature and high-pressure conditions within a specified time frame.

476-21 standard name:

BS 476-21: Fire test on building materials and structures - Part 21: Method for determination of the fire resistance of load bearing elements of construction.

The most critical aspect of fire resistance testing for steel structure coatings is thermal insulation performance. Refer to the standard furnace temperature changes:

According to the standard, time-temperature is controlled, with different temperatures displayed at different times as follows:

538°C at 5 min

795°C at 20 min

843°C at 30 min

927°C at 1 h

1010°C at 2 h

1093°C at 4 h

Other additional times

For details, consult: CAS Fire

Source: RZ202501