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What is a Fire-Resistance Rating and why is it important?

We’ve all heard the term “fire resistance”, but all the codes, language, and rules around it can be confusing. It is important to understand why we have fire ratings, what they really mean, how they’re created and how to use them. When installed correctly, fire-resistant materials and assemblies can slow or even stop the spread of a fire. The essential purpose of fire resistance is to protect the building structure itself and the building’s occupants, allowing them adequate time to exit the building in a safe manner before it is engulfed in flames or the structure collapses.

What is a fire-resistance rating?

A fire-resistance rating is a measure of the ability of the building construction assemblies (partition, wall, floor, etc.) to withstand the spread of fire, smoke, or both. Building codes typically require that buildings be constructed with a certain level of fire resistance of both building structural systems and finishes in order to protect the lives and property of the people who use them. Different types of buildings, such as residential, commercial, and industrial, may have different rating requirements. Fire resistance is usually quantified as the amount of time taken to withstand a standard test fire, while not exceeding a certain temperature for a specified amount of time.

Fire-resistance ratings are the results of tests in which materials and assemblies (some of which are fire-resistant) are tested against fire. These tests include different construction elements, like beams, floors, columns, walls, and roofs. These ratings give us an idea of how long and how well these materials and systems stand up to the fire while retaining their structural integrity. They are usually given a rating between one and four hours.

The language and abbreviations of fire ratings often can be confusing because of the different organizations that create ratings, tests, and standards. Testing is done by various entities with the most common being Underwriters Laboratories (UL) and the American Society for Testing and Materials (ASTM). UL and ASTM rigorously test materials and assemblies in all kinds of environments to determine their fire-resistance rating. The results inform the creation of codes by the International Code Council (ICC) as well as local building codes.

Adequately avoiding, controlling, or containing fires relies on several different systems including fire detection systems like smoke and fire alarms, and compartmentalization systems that contain the fire by stopping it from quickly spreading throughout the building. These systems could include fire doors, fire-resistant walls, and rated assemblies. Suppression systems like sprinklers, hose systems, and non-water-based fire suppression/extinguishing systems attempt to put the fire out or slow its spread until firefighting crews arrive.

Requirements for these systems, as well as fire-resistance-rated building materials and assemblies, depend on several factors:

  • The type of building occupancy

  • Fire resistance demands in a warehouse will be far less stringent than those for an office building or apartment complex, where occupancy is higher.

  • Building height

  • Distance between the building and adjacent structures or property lines

  • Building material

Final Thoughts

The integration of fire-resistant assemblies and materials into any construction project can be as complex and varied as the buildings in existence today. Testing agencies cannot test for every eventuality, a combination of materials, or newly devised assemblies. The best method to cope with this fact is to plan early and plan well.

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