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Lightwell Shaft with Fire Shutters

nealderidder

Sawhorse
Joined
Dec 7, 2010
Messages
394
Location
Sacramento, CA
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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A two-story atrium with two-story shafts? Or a four story atrium?

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.
 
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. Which is exactly the conclusion I'm trying to avoid.

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. That is indeed what I'm 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. I hope so!

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. Maybe as a last resort.

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

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.
 
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.
 
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.

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.
 
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?
 
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?

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.
 
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?

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.
 
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.


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.
 
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.

Agreed, I need to be careful not to argue against them being "openings" they obviously are. My argument needs to be that they are not "connecting".
 
Agreed, I need to be careful not to argue against them being "openings" they obviously are. My argument needs to be that they are not "connecting".


My argument would be are you going to get the shutters past an AHJ??

Will they fly???
 
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.

As an aside, I am wondering why we moved away from having a dimensional criteria as part of what differentiates a shaft and atrium. We used to have it in the UBC but not anymore.

Other countries still have it. I think in Australia - apart from other criteria - they only consider something an atrium if it can at least allows passage of a 20 foot cylinder. Anything less would be a shaft.

The dimensional criteria may help especially in situations like this where there is a mix of different configurations of vertical spaces that appear to blend with each other.

However, on the design side, I do see how dimensional limits can also be a shackle to some creative solutions. I wonder if that factored in the code committees decision in taking out the dimensional criteria.
 
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