Fire Resistance Rating

Written by Nicholas Kamuda
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One aspect of building materials that is essential to consider when building a house is the fire resistance rating of the material. In a nutshell, the fire resistance rating is just what you may imagine: it is a number given to a material by a testing center that describes how long the material can withstand the effects of high heat and fire. For example, a material with a two-hour fire rating can withstand a blaze for as long as two hours.

Building materials, assemblies, and other structural elements such as beams and columns are all tested and rated for performance under adverse conditions. The tests are given in controlled laboratory settings, with all parameters according to ASTM (the American Society for Testing and Materials) Standard E 119 for Fire Tests of Building and Construction Materials. All of ASTM's fire tests require that the materials be tested using full-scale configurations and assemblies.

The single catch regarding fire resistance ratings is that the tests rate the relative performance of materials, not the actual performance. In a real fire, there are far more variables than laboratories can possibly simulate, so there is no guarantee that materials will perform exactly as rated. However, a material with a three-hour fire rating will likely withstand fire for much longer than a material with a one-hour rating.

The Fire Resistance Rating of Insulated Concrete Forms

Modern building systems, such as ICFs, generally have longer fire resistance ratings than traditional wood framing. Though the performance of ICF walls under fire may vary from manufacturer to manufacturer, some have performed well enough in tests to earn three-hour fire ratings. Combined with non-wood roofing and carefully considered insulation and details such as fasteners and finishes, ICFs can generally provide builders with effective resistance to the damaging effects of fire.


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