Fire Ratings Rule of Thumb

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    Amna Martinez

    The BCI book - section in the back called 'fire rated construction' has some info and illustrations.  

    Also this link was helpful, for me at least:

    http://www.usg.com/content/dam/USG_Marketing_Communications/united_states/product_promotional_materials/finished_assets/usg-fire-resistant-assemblies-catalog-en-SA100.pdf

     

     

     

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    Allison Burrell

    Thank you! This is really helpful

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    Jose Magana

    Very good link, thank you

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    Mary Genis

    Awesome reference link! A very general rule of thumb I've noticed is that if it has 2 layers of gyp - it's usually 2hr rated 

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    Artem Melikyan (Edited )

    Hello All,

    I have several questions on this topic:

    1. While going through Fundamentals of Building Construction I came across these fire-rated partitions.

    Can someone, please, explain why partition B is 1-hr rated (as says the description to illustration below)

    if it has 2 layers of gyp on one side and even 3 layers (2 of which are 1/2") on the other side?

     

    2. In Building Construction illustrated, it says that 1-hr rating can be achieved by 2 layers of 1/2" regular gyp? I thought that rating can only be provided by type X or type C board, but not a regular one. Please see below and correct me:

     

    3. If a partition has 2 layers of 1/2" gyp on each side would it be 1-hr or 2-hr rated?In other words does 1/2" layer equal 5/8" layer rating capability? 

    4. Do I understand it correctly that a partition framed with wood studs can be fire-rated (just as with metal studs) if that wood is fire-retardant treated?

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    Gang Chen (Edited )

    This is the most useful "rule of thumb":

    Type X gypsum board is defined by ASTM C1396 and generally requires a fire-resistance rating of not less than one hour for 5⁄8” thick boards or 45 minutes for ½” boards.

    Gang Chen, Author, Architect, LEED AP BD+C (GreenExamEducation.com)

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    Gang Chen

    I think another main point of dealing with fire rated construction is to make sure you have a complete fire rated enclosure. For example, if you are designing a 1-hour corridor, make sure the ceiling is 1-hour rated, in addition to the walls, and the enclosure is completely 1-hour fire rated with no gap.

    If I were the exam writer, I can easily show you a few graphic diagrams, showing the 1-hour rated construction stops at the T-bar ceiling, or stops at the underside of the structure, or stops at a 1-hour rated ceiling and ask you to pick the correct answer(s), OR ask you to drag and drop to place elements of a 1-hour corridor in the proper places.

    Gang Chen, Author, Architect, LEED AP BD+C (GreenExamEducation.com)

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