Atrium or Floor Opening (or Both)?

[Jonathan Carr]

Question: I have three story B-occupancy building with a stacked lobby. In the lobby, there is a stacked, small floor opening and fancy stair. The floor opening / stair connects three stories. The floor opening / stair complies with 2015 IBC 1019.3 Condition #4, stating the stair can be unenclosed, provided:

1. Building is equipped with automatic sprinkler system.
2. Floor opening does not connect more than four stories.
3. Area of floor opening between stories does not exceed twice the horizontal projected area of the stair.
4. Opening is protected by draft curtain and closely spaced sprinklers per NFPA 13.

In this situation, is this three-story floor/stair opening also an atrium, by definition? It's confusing because IBC 404 Atrium definition excludes enclosed stairs. IBC 1019.3 Condition 4 allows the enclosed stair to be unenclosed. Does "unenclosing" my stair by IBC 1019.3 Condition #4 revert me to an atrium?

Note: the lobby stair is not a required means of egress.

 

[RLGA]

Section 1019.3 clearly states "floor openings containing exit access stairways or ramps that do not comply with one of the conditions listed in this section shall be enclosed..."

If you were made to comply with the requirements for atriums as well, then you'd be complying with two of the conditions listed, since conforming with the requirements of atriums is listed as Condition #5.

 

[Jonathan Carr]

Thanks very much for your reply! I was hoping you'd respond, because I read and reread your previous responses to atrium questions, and you are very knowledgeable!

To delve into your response a little further, I see your point. IBC 1019.3 states. "...floor openings containing exit access stairways or ramps that do not comply with one of the conditions listed shall be enclosed...."

I understand we only need to comply with one of the conditions to un-enclose the stair. But, if we invoke condition #4, and our floor openings and (now) unenclosed stair connect three stories, are we now ALSO an atrium? Chapter 2 defines an atrium as, "An opening connecting two or more stories other than enclosed stairways...." I never thought we had an atrium to begin with, and now it appears we're backing into an atrium situation!

Please help me escape this weird, circular IBC logic loop. Are we an atrium?

 

[RLGA]

You don't start in the atrium section--you go there when another section directs you to that section. Further, Section 102.1 states that a specific requirement will take precedence over a general requirement. The requirements for atriums in Section 404 are general requirements applicable to atriums with or without stairs, but the requirements of Section 1019 are specific to exit access stairs and ramps; thus, the requirements for atriums are only applicable when directed to that section.

Therefore, your situation would be considered an unenclosed exit access stair that could be considered an atrium but isn't unless you decide to follow Condition #5.

 

[Jonathan Carr]

Thanks very much for your reply! I was hoping you'd respond, because I read and reread your previous responses to atrium questions, and you are very knowledgeable!

To delve into your response a little further, I see your point. IBC 1019.3 states. "...floor openings containing exit access stairways or ramps that do not comply with one of the conditions listed shall be enclosed...."

I understand we only need to comply with one of the conditions to un-enclose the stair. But, if we invoke condition #4, and our floor openings and (now) unenclosed stair connect three stories, are we now ALSO an atrium? Chapter 2 defines an atrium as, "An opening connecting two or more stories other than enclosed stairways...." I never thought we had an atrium to begin with, and now it appears we're backing into an atrium situation!

Please help me escape this weird, circular IBC logic loop. Are we an atrium?

 

[Jonathan Carr]

I understand the response. We are not required to comply with more than one condition stated in IBC 1019.3. Thanks again!

 

[Jonathan Carr]

I missed your second response before writing mine above. Now it is completely clear. Thank you for the added explanation regarding precedence of "specific" over "general" requirements (IBC 102.1). I've escaped the logic loop! Thanks again.

 

[rematwork]

Appreciate this discussion...

I have a similar scenario with a 3-story mixed use building (sprinklered). Ground floor retail/restaurant, second floor office, and third floor restaurant. The upper floors have (1) enclosed/rated interior exit stairway and wondering if the other required means of egress could be served by a common lobby that houses an elevator and open exit access stair that serves the upper floors per IBC 2015 1019.4 Condition #4 . Side note that we can make the max 250' travel distance from third floor to exit discharge on the ground floor. This section of code (1019.4) make it seem like it could be applicable, however 1006.3 states "The path of egress travel to an exit shall not pass through more than one adjacent story." In this scenario which section of code prevails? If section 1019.4 Condition #4 is trumped by 1006.3, would 1019.4 Condition #5 (atrium) be a potential solution if the common area was compliant with Section 404?

 

[cda]

Appreciate this discussion...

I have a similar scenario with a 3-story mixed use building (sprinklered). Ground floor retail/restaurant, second floor office, and third floor restaurant. The upper floors have (1) enclosed/rated interior exit stairway and wondering if the other required means of egress could be served by a common lobby that houses an elevator and open exit access stair that serves the upper floors per IBC 2015 1019.4 Condition #4 . Side note that we can make the max 250' travel distance from third floor to exit discharge on the ground floor. This section of code (1019.4) make it seem like it could be applicable, however 1006.3 states "The path of egress travel to an exit shall not pass through more than one adjacent story." In this scenario which section of code prevails? If section 1019.4 Condition #4 is trumped by 1006.3, would 1019.4 Condition #5 (atrium) be a potential solution if the common area was compliant with Section 404?

Welcome

From another DFWer

Give it a few days, it is Friday

 

[RLGA]

I believe you're referring to Section 1019.3 and not 1019.4.

Condition 4 allows an unenclosed exit access stairway to connect up to four stories based on the occupancies you listed; however, as you pointed out, Section 1006.3 only allows the use of an exit access stairway for reaching an exit on an adjacent story. Thus, you could use the exit access stairway as one of the two means of egress from the third story, but you would need a second exit from the second story.

An atrium stairway can be used as an exit stairway per Section 1023.2, Exception 2; however, the exception is only for the stairway enclosure construction--all other requirements for exit stairways are applicable, such as signage per Section 1023.9 and Class I standpipes per Section 905.4.1 associated with a sprinkler system.

 

[rematwork]

RLGA - Thank you for your response. You're correct I was referring to 1019.3 Condition 4.

In your opinion if an exit stairway within an atrium were to be utilized (rather than pursuing an exit access stair as previously mentioned), would an elevator be able to open into the atrium? I am imagining not because of 1023.4 "Elevators shall not open into interior exit stairways and ramps."

 

[cda]

RLGA - Thank you for your response. You're correct I was referring to 1019.3 Condition 4.

In your opinion if an exit stairway within an atrium were to be utilized (rather than pursuing an exit access stair as previously mentioned), would an elevator be able to open into the atrium? I am imagining not because of 1023.4 "Elevators shall not open into interior exit stairways and ramps."

I would say yes, see it all the time.

Talking two different conditions.

 

[Phil B]

I believe you're referring to Section 1019.3 and not 1019.4.

Condition 4 allows an unenclosed exit access stairway to connect up to four stories based on the occupancies you listed; however, as you pointed out, Section 1006.3 only allows the use of an exit access stairway for reaching an exit on an adjacent story. Thus, you could use the exit access stairway as one of the two means of egress from the third story, but you would need a second exit from the second story.

An atrium stairway can be used as an exit stairway per Section 1023.2, Exception 2; however, the exception is only for the stairway enclosure construction--all other requirements for exit stairways are applicable, such as signage per Section 1023.9 and Class I standpipes per Section 905.4.1 associated with a sprinkler system.

Is a simple 2 story lobby an atrium? Forgive me for being confused, but I see many instances where the 2nd level corridors for instance overlook a lobby below without major rated enclosures. I must be reading things wrong.

 

[cda]

Is a simple 2 story lobby an atrium? Forgive me for being confused, but I see many instances where the 2nd level corridors for instance overlook a lobby below without major rated enclosures. I must be reading things wrong.

Sometimes depends on which Edition Year you are reading.

 

[Phil B]

Sometimes depends on which Edition Year you are reading.

Florida Building Code 2020

 

[cda]

ATRIUM. An opening connecting two or more stories other than enclosed stairways, elevators, hoistways, escalators, plumbing, electrical, air-conditioning or other equipment, which is closed at the top and not defined as a mall. Stories, as used in this definition, do not include balconies within assembly groups or mezzanines that comply with Section 505.

 

[cda]

Florida Building Code 2020

Is a simple 2 story lobby an atrium? Forgive me for being confused, but I see many instances where the 2nd level corridors for instance overlook a lobby below without major rated enclosures. I must be reading things wrong.

depends on year built?

depends on code adopted at the time?

depends on if someone knows the code?

 

[RLGA]

A two-story volume is an atrium by definition (see cda's response above). HOWEVER, the best place to start regarding two-story openings is Section 712 on vertical openings rather than going directly to Section 404 for atriums. That Section 712, which includes a reference to Section 404, also includes Section 712.1.9 for two-story openings. If your two-story opening complies with the conditions listed, then compliance with Section 404 is not required. It is still an atrium by definition but is not required to comply with the atrium requirements.

Even if you went the route of Section 404 for atriums, a two-story atrium is not required to comply with the smoke control requirements per Section 404.5, Exception, or the enclosure requirements of Section 404.6 per Exception 3. However, other requirements per Section 404 would be applicable that otherwise would not be applicable if using Section 712.1.9.

 

[Phil B]

A two-story volume is an atrium by definition (see cda's response above). HOWEVER, the best place to start regarding two-story openings is Section 712 on vertical openings rather than going directly to Section 404 for atriums. That Section 712, which includes a reference to Section 404, also includes Section 712.1.9 for two-story openings. If your two-story opening complies with the conditions listed, then compliance with Section 404 is not required. It is still an atrium by definition but is not required to comply with the atrium requirements.

Even if you went the route of Section 404 for atriums, a two-story atrium is not required to comply with the smoke control requirements per Section 404.5, Exception, or the enclosure requirements of Section 404.6 per Exception 3. However, other requirements per Section 404 would be applicable that otherwise would not be applicable if using Section 712.1.9.

Thank you all! CDA - This is for potential new work so it would be under the FBC 2020

 

[Phil B]

A two-story volume is an atrium by definition (see cda's response above). HOWEVER, the best place to start regarding two-story openings is Section 712 on vertical openings rather than going directly to Section 404 for atriums. That Section 712, which includes a reference to Section 404, also includes Section 712.1.9 for two-story openings. If your two-story opening complies with the conditions listed, then compliance with Section 404 is not required. It is still an atrium by definition but is not required to comply with the atrium requirements.

Even if you went the route of Section 404 for atriums, a two-story atrium is not required to comply with the smoke control requirements per Section 404.5, Exception, or the enclosure requirements of Section 404.6 per Exception 3. However, other requirements per Section 404 would be applicable that otherwise would not be applicable if using Section 712.1.9.

Here's where I am getting stuck: I would like to have portions of my second level floor open to the floor below. If the floor area of the 2nd level exceeds that which would allow it to be considered a mezzanine, I believe I can still have portions of the second level open to the floor below if it opens into an atrium and the surrounding walls are rated, correct?

What if I have a 2 story space that complies with 712.1.9 as a vertical opening? Can I have the 2nd level open to the floor below? I don't think I can, but am not sure.

 

[ChrisCampbell]

If your two-story space complies with 712.1.9, it would only be connecting two stories. If your second level is a mezzanine and not a story, this would not count towards the two story limit in using 712.1.9.

 

[Phil B]

If your two-story space complies with 712.1.9, it would only be connecting two stories. If your second level is a mezzanine and not a story, this would not count towards the two story limit in using 712.1.9.

Understood, but I am trying to understand the limitations of having the 2nd level open to the 1st, which I can't do because I'm not a mezzanine, right?

 

[ChrisCampbell]

If Level 2 is a story, you have really two options:

1. Comply with all the criteria of IBC 712.1.9
2. Consider the space an atrium and comply with IBC 404 (though smoke control would not be required with only two stories in the atrium).