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Fire-rated floor-ceiling separation

Discussion in 'Commercial Building Codes' started by BayPointArchitect, Nov 16, 2016.

  1. BayPointArchitect

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    Given a small three story office building, non-combustible construction, and non-sprinkled. Entirely code compliant in terms of allowable height and area for a type "B" occupancy.

    Again I must say that there is only one type of occupancy throughout the entire building so that there is no need for occupancy separation between dissimilar occupancies.
    Type IIB Construction (although a Type VB Construction should yield the same answer).

    Question:
    Can you think of any reason why the floor-ceiling assemblies need to be fire-rated?

    I think I already know the answer but sometimes I second-guess myself.

    Thank you!

    ICC Certified Plan Reviewer
    NFPA Certified Fire Plan Examiner
    Unemployed paper route carrier
     
  2. Examiner

    Examiner Sawhorse

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    If the building's size and construction type for the most restrictive occupancy use group complies with non-separated occupancy section of the code then, I do not see why any type of rated construction is needed. But you stated that there is only one occupancy use group being, Business. Are there any large rooms over 750-sf used for meeting purposes? If there are, are they under 10% of the floor area they occur on? Do not know if this helps.
     
    BayPointArchitect likes this.
  3. BayPointArchitect

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    Yes. You have confirmed that the same rules applied to vertical partitions and barriers should also apply to horizontal floor separation.
    With business above and below the floor-ceiling assembly, that floor could consist of anything that is consistent with the type of construction (combustible or non-combustible).

    No UL fire-rated assembly required.

    Thanks
     
  4. steveray

    steveray Sawhorse

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    If there are any shafts or rated walls built on it (surgery center?) or something that might be a rated "B".....?
     
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  5. north star

    north star Sawhorse

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    # ~ # ~ #


    BayPoint,

    Has the building always been a Type B bldg., even from
    when it was a brand new bldg., or has it changed
    uses & Occ. Groups over the years ?


    One possible scenario is to have the fire rated assemblies
    installed when the construction is new, so as to have
    more flexibility in attracting new tenants, ...less costs,
    and a quicker turn-around as the tenants come & go.



    # ~ # ~ #
     
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  6. cda

    cda Sawhorse

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    Maybe where you have rated corridors??
     
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  7. BayPointArchitect

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    Yes, corridors would need to be one-hour rated all around. Good point.
    And the top/bottom of shafts would need to be one-hour rated as well.

    This scenario is entirely hypothetical as I try to think through reasons why any other code official would say that we need fire rated horizontal separation between two identical tenant spaces - or two small office rooms. Generally speaking, I don't think there needs to be fire-rated floor systems between similar occupancies. But my next step is to read through the entire NFPA 101 Life Safety Code (again) to see if there is anything that would be more restrictive. Unlike the IBC, NFPA requires a fire-rated barrier between storage (S1) and business (B) occupancies.

    After I making my final conclusion, I will give a lunch-n-learn presentation to a group of structural engineers who want to avoid unnecessarily difficult details between walls, floors, and structural framing. If the architect fails to clearly identify which walls and floor systems are fire-rated, then the structural engineer can still anticipate what might need to be rated. For example, he might orientate a structural beam or bar joist in a way that makes it easy and clean to extend a fire barrier up to the bottom of the metal roof deck (deflection track).

    Thanks again everyone.
     
  8. cda

    cda Sawhorse

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    There is always the passage that you can have an opening between two floors.

    So seems like a horizontal rating is not required, as long as not needed by another section of the code.
     
  9. steveray

    steveray Sawhorse

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    No offense but, some "older" BO's hang onto mythical "tenant separation" requirements that do not exist in most buildings these days. Where I see it in new construction now is, IIB buildings with shafts supported on the upper floors. Fire barriers are required to be supported by structure rated the same as the barrier, so the floor and beams and columns get rated back and down to the foundation....
     
  10. BayPointArchitect

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    "mythical tenant separation"
    I like the way you put that.
    If I am designing the building, I try to incorporate a MODERATE level of protection that affords future flexibility among various types of tenants. This would be consistent with NorthStar's comment above.

    Then the savvy contractor and/or building owner will dumb-down the type of construction from non-combustible to combustible and eliminate sprinkler systems to make the initial cost of construction as cheap as possible. No problem with saving between 6% and 25% in the cost of construction.
    During subsequent tenant finishes, those same individuals blame me for not insisting upon provisions that would otherwise avoid the need to add protection AFTER the building is considered to be "completed". No problem with trying to make things easier in the beginning but harder during tenant finishes. I just wish that I did not get blamed for not having any foresight.

    Ideal strip mall building:
    Type IIB Construction (non-combustible framing)
    One-hour fire-rated tenant separation
    Alarm system with sprinklers and smoke detection
    Plenty of parking spaces
    Aesthetic appearance
    Ready and available for any type of tenant that zoning will allow
     
    #10 BayPointArchitect, Nov 18, 2016
    Last edited: Nov 18, 2016
  11. north star

    north star Sawhorse

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    @ + @ + @


    BayPoint,

    Some years ago, there was a small strip development
    where the owner was persuaded to install 2 hr. rated
    Tenant Separation Walls at the new construction stage.
    There were no requirements for sprinklers, so the costs
    were a little bit lower initially........Over the past few
    years the various types of Tenants have come in and out
    rather quickly.

    Just sayin', ...the Long Term View needs to be a part
    of the dialogue when discussing type of construction and
    the [ quicker ] financial return on their investment.
    Magically, whenever the discussion of increasing their
    "Bottom Lines" is part of the process, their views are
    [ sometimes ] changed quickly.



    @ + @ + @
     
  12. Yikes

    Yikes Gold Member

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    One other "ideal" we have found is the use of post-tensioned flat slabs at the ground level, especially in areas that might be subject to inclement weather during construction. You'll spend more in concrete, but if you can avoid getting stuck cleaning out and drying muddy footings, rebar and formwork, you may actually save money during construction.
     
  13. JBI

    JBI Sawhorse

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    A rated corridor (or exit passageway if present) on the second or third story would need to be supported by rated construction all the way down through the load path, but that would not necessarily require the entire floor/ceiling assembly to be rated, only the supporting structural elements.
    NYS was one of 'those' states (prior to 2002) that required compartmentation within single occupancies. Upon adopting modified I-Codes in 2002 we had to learn what it meant to accept less compartmentation.
     
  14. RLGA

    RLGA Sawhorse

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    Fire-resistance-rated corridor walls in Type IIB, IIIB, and VB, are not required to be supported by fire-resistance rated supporting construction (Section 708.4, 2015 IBC; also exists in previous editions).
     

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