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Exposed joists in a 1/2hr rated corridor.

Discussion in 'Commercial Building Codes' started by Ryan Schultz, Jul 4, 2019.

  1. Ryan Schultz

    Ryan Schultz Sawhorse

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    So we have a Type VB w/ R-2 occupancy.

    I would like to have exposed floor joists in the corridors.

    ---

    First off, per TABLE 1020.1 CORRIDOR FIRE-RESISTANCE RATING it looks like the corridors need to be 0.5hr rated. Is this a correct reading?

    Dumb question, i assume this applies to the floors as well, correct?

    Assuming that it does, does anyone know a UL rated assembly that achieves the 0.5hr rating with exposed wood joists?

    Per the heavy exception and TABLE 602.4 WOOD MEMBER SIZE EQUIVALENCIES, could we use 3 1/2 x 5 1/2" LVL for the joists, and achieve our rating?

    Happy 4th!
     
  2. Ryan Schultz

    Ryan Schultz Sawhorse

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    Forget to mention, is fully sprinklered.
     
  3. cda

    cda Sawhorse

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    Not sure how you get a rated corridor with exposed wood.

    Built the rated corridor to code,,

    Than add the fake or fire retardant wood decoration??
     
  4. cda

    cda Sawhorse

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    “”I would like to have exposed floor joists in the corridors. “””

    Are these part of the ceiling floor assembly for the story above???
     
  5. cda

    cda Sawhorse

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    Yes 1/2 hour rating required
     
  6. RLGA

    RLGA Sawhorse

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    You probably could, but the floor, too, must be constructed to heavy-timber requirements per Section 602.4.6.
     
  7. Ryan Schultz

    Ryan Schultz Sawhorse

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    ugg. 1/2 is so minimal, common sense wise, you'd think you could achieve this rating with heavy timber joists and a gyp bd. covered sheathing.

    Beyond the prescriptive application of ul ratings, is there a way to approach this via a 'calculated' approach i wonder?
     
  8. RLGA

    RLGA Sawhorse

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    For floor and roof assemblies, fire resistance is determined from the exposed underside of the assembly—not from the top side. Therefore, you have to have something protect the joists. For a 1/2-hour rating, you probably could wrap all the exposed surfaces, including joists, with 5/8-inch gypsum board per Table 722.6.2(1) and not include the joists in the calculation as the airspace between joists would have contributed to the performance of the assembly if the gypsum board was continuous across the bottom of the joists.
     
  9. Ryan Schultz

    Ryan Schultz Sawhorse

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    But if the joist's themselves are heavy timber (with an integral 1hr rating themselves) it would seem you wouldn't need to 'wrap' them.
     
  10. tmurray

    tmurray Sawhorse

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    We see it some here. They use char ratings on the wood as an insulator...there was a bunch of research done by the National Research Council here in Canada about it.

    The structural engineer needs to be involved so they can tell the building official that the loss of the wood won't compromise the structure of the building (i.e., the joist might be rated for an hour based on the char, but will fail due to the loss of structural strength).

    This is treated as an alternative solution to the prescriptive requirements though.
     
  11. RLGA

    RLGA Sawhorse

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    I thought you were going back to using regular joists. You might be able to get approval by using glue-laminated joists of the size mentioned and applying 5/8-inch gypsum board to the underside of the deck in between joists. However, that will be something that the building official will have to approve and not us here on the forum.
     
  12. Ryan Schultz

    Ryan Schultz Sawhorse

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    Gotcha.. Will give it a try and report back!
     
  13. Ryan Schultz

    Ryan Schultz Sawhorse

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  14. cda

    cda Sawhorse

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    Any chapter 8 problems?
     
  15. ADAguy

    ADAguy Sawhorse

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    What happened to the waiver of rating if the building is fully sprinklered?
     
  16. cda

    cda Sawhorse

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    The half hour is required

    Even with sprinklers
     
  17. Chrisjoneill

    Chrisjoneill Registered User

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    If you have the height build a rated floor ceiling and put decorative beams underneath
     
  18. Ryan Schultz

    Ryan Schultz Sawhorse

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