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Lightwell Shaft with Fire Shutters

Discussion in 'Commercial Building Codes' started by nealderidder, May 26, 2020.

  1. nealderidder

    nealderidder Bronze Member

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    Hello all,

    I've got an existing four story commercial building I want to put some holes in. It's a poured-in-place concrete building so I'm OK with the required 1HR floor/ceiling ratings that are required.

    The new holes are in the floors to allow a two-story "atrium" space between 1st and 2nd. To get light into that new "atrium" I also want to open up 3rd and 4th and the roof and plop a skylight on the top (see sketch).

    Those dashed lines you see in the light wells would ideally be non-rated strorefront with fire shutters (Like an McKeon coiling door). I believe these "light wells" would be considered "shafts" per CBC 713 (yep, California 2019 code) and need a 2 HR rating.

    My questions for you fine folk:

    1. Is the space that includes the 1FL and 2FL an "atrium" and is it a two-story atrium?
    2. Are the Light wells a "shaft" and are they connecting four floors?
    3. Do you see any issues with using fire shutters to reach the 2HR shaft rating requirement in the light wells?

    Any insight would be appreciated!
     

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  2. cda

    cda Sawhorse

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    Fire sprinkler system installed already??
     
  3. cda

    cda Sawhorse

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    Sorry with my limited knowledge


    You are an atrium
     
  4. nealderidder

    nealderidder Bronze Member

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    Yes but we'll have to extensively remodel
     
  5. nealderidder

    nealderidder Bronze Member

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    A two-story atrium with two-story shafts? Or a four story atrium?
     
  6. cda

    cda Sawhorse

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    So all four floors are open to each other?
     
  7. Enri Code

    Enri Code Sawhorse

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    Based on your drawing sections (that are well done by the way...), it appears that once you make the new floor opening you will then have atria that spans the 4 stories.

    I don't see any issues with using fire shutters. You may be able to make do with the 1 hour fire shutters for an atrium but I see the logic of keeping them as 2 hour.

    I say this because of the size of the floor opening between the first and second floor.

    Unless you also provide fire shutters to enclose the perimeter of that big opening as well, you'll always have to contend with the 4 story atrium situation. Treating those light wells as shafts (2 hour fire rated) with no openings once the fire shutters activate may technically make the opening through the first and second floor as just a 2 story atrium which is probably what you are trying to get to.

    The required smoke control also gets muddled up somehow. If it is acceptable that it is considered just a 2 story atrium based on treating those light wells as shafts, then it may be acceptable that the smoke control requirement goes away? Not sure.

    It's a creative solution all-in-all in my opinion. Really having the fire sprinklers integrated into the design will be key I would think as any solution will need to prove to be equally or more safe. Maybe extra sprinklers in the light well, etc.

    Another possible thing to do would be to use a horizontal fire shutter between the second and third floor openings which would bolster the case of truly having just a 2 story atrium between first and second floor.

    This is fascinating. Let us know what the AHJ says.
     
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  8. nealderidder

    nealderidder Bronze Member

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  9. nealderidder

    nealderidder Bronze Member

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    I'm relying on the definition of an atrium which is an opening connecting stories which is enclosed at the top. The light wells are not open to the other stories so I don't see this as connecting four stories. I see it as connecting two stories. Agreed that if this gives the AHJ heartburn we might be able to mitigate some of that worry with additional sprinklers.

    Thanks for the input.
     
  10. Paul Sweet

    Paul Sweet Sawhorse

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    Anything that doesn't have a floor in it is an opening between stories. You shouldn't need a smoke control system because the atrium only CONNECTS two stories. The upper two stories are isolated from the atrium.
     
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  11. Enri Code

    Enri Code Sawhorse

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    Definitely give us an update on this when you can. I really like how you opened up the space and how you thought about getting light into the building. Good to know what to watch out for when doing something similar. Thanks for sharing.
     
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  12. Builder Bob

    Builder Bob Sawhorse

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    questionable? I believe smoke seals would be required along with annual inspection of shutters. What method of activation is going to be used for the shutters? Why not install glazing in frames required by the code along with fire sprinkler protection and eliminate the maintenance nightmare associated with the fire shutters?
     
  13. Enri Code

    Enri Code Sawhorse

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    I had thought the same but if he did that, it would go against what he is trying to achieve... which is to show that only 1st and 2nd floor has an atrium and that 3rd and 4th floor openings are shaft enclosure.

    It would be an acceptance that the "light well" that goes through 3rd and 4th floor is also an atrium... and since 1st and 2nd floor is an atrium... and since there is an opening between 2nd and 3rd floor... then it is therefore an atrium spanning 4 floors. Dominoes fall down from there since now perimeter of floor opening between 1st and 2nd floor would also need to be addressed and so on...

    Personally, I also do think it is questionable as it is currently presented. My mind still thinks it is a 4 story atrium because there is a connection of vertical spaces with the floor openings stacked on top of each other. But I do acknowledge that this is somewhat different because of dimensional and spatial differences as space goes up with 1st and 2nd floor opening quite big in relation to the 3rd and 4th floor openings that are smaller so there may be something else that could be at play here.

    With some time to think about it, an alternate solution would be to add glazing at the floor openings between 2nd and 3rd floor.
    1. Glazing won't impede the light coming through.
    2. Glazing will provide a physical separation between 2nd and 3rd floor and will bolster case that there is definitely no vertical connection between spaces of 1st floor through 4th floor space.
    3. Physical separation will support case that atrium is only at 1st and 2nd floor because any sense of connection to the upper floors is cut off for sure.
     
  14. cda

    cda Sawhorse

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    Plus not sure if you could find a BO. to buy off on using shutters
     
  15. steveray

    steveray Sawhorse

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    4 story atrium and your 2 hr shutters need to be supported by 2hr construction...But it could be 1hr...
     
  16. steveray

    steveray Sawhorse

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    404.6 may be your friend...or not....
     
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  17. nealderidder

    nealderidder Bronze Member

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    That's where I'm leaning right now. CBC 404.6 has an exception for the 1 HR separation requirement that allows the use of a glass wall (probably double glazed storefront for sound) as long as I've got a deluge-type sprinkler system on the room side of the glass. Much better than fussing with fire shutters and trying to detail the shutters/storefront/blinds etc.
     
  18. nealderidder

    nealderidder Bronze Member

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    I'm counting on it!
     
  19. nealderidder

    nealderidder Bronze Member

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    It could be a fall back position but I'm going to give the hard-sell that those shafts are not atriums since they don't "connect" anything (other than visually) to the 3rd and 4th floors.
     

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