"Mezzanine" between Lobby & Prayer Hall

[bseck]

Hello all, this is my first time posting on this forum & I wanted some second opinions on a two-story mosque (A-3) we are currently designing. My intention is to not sprinkle the building if we can, but our client is already prepared that they might have too. We have a partially** double height prayer hall & a true double height entry/lobby area with a stair leading up to a space that can look down into the prayer hall (no fixed seating or anything of the sorts). From this space, you have entry to the second floor space. See the image below of a section cutting through what I just talked about:

Yellow is prayer hall, green is lobby, blue is upper space.

As for the "partially" part, this is a section through the prayer hall:

Yellow is prayer hall, orange is accessory classrooms (305.1.1)
.
Just some basic info on the building as it currently stands:

• New construction
• II-B
• Jurisdiction uses IBC 2021

I have a few questions:

1. Is the blue area technically a mezzanine (implying it meets the min. 1/3 area)?
   1. I'm not sure which space (or both) would determine this area requirement. My initial assumption is the lobby since it hosts the stair to get up to it.
   2. The code doesn't go into any detail about a situation where its 1st floor→mezzanine→2nd floor (if that's even allowed?)
      1. We already have designed two dedicated egress stair shafts and an elevator to the second floor.
2. If the blue area is a mezzanine, how would that affect 903.2.1.3, specifically point 3;
   1. In the event that the floor & wall construction between the yellow & orange space is fire rated & thus create two separate fire areas, is the fire area of the prayer hall+lobby intervening on the second floor (thus triggering the need for sprinklers) or is it still considered a single story space?
3. I'm not sure if the interconnection between the lobby & the prayer hall would prohibit exception 2 for 903.2.1.3. More specifically, I'm confused on what exactly entails "are part of a separated use." My assumption is that there needs to be a full wall between the yellow and blue space?

If you need any more info, just ask!

Thanks for the assistance.

 

[Yankee Chronicler]

I have a few questions:

1. Is the blue area technically a mezzanine (implying it meets the min. 1/3 area)?

There is more to a space being a mezzanine that just 1/3 of the area. 1/3 of the area of WHAT? Definition:

MEZZANINE. An intermediate level or levels between
the floor and ceiling of any story and in accordance with
Section 505.

You have acknowledged that you have a two-story building. This space you are asking about is not an intermediate level between the first story and the second story, therefore it isn't a mezzanine. What you have is a portion of the second floor that connects two second-floor spaces.

The definition also sends us to IBC section 505:

505.2.1 Area limitation. The aggregate area of a mezzanine or
mezzanines within a room shall be not greater than one-third of
the floor area of that room or space in which they are located.
The enclosed portion of a room shall not be included in a
determination of the floor area of the room in which the mezzanine
is located. In determining the allowable mezzanine area,
the area of the mezzanine shall not be included in the floor area
of the room.

As drawn, the space you are asking about is not located within either the worship hall or the entry lobby. Again -- it's not a mezzanine.

Too many architects think they can label anything as "Mezzanine" and that makes it a mezzanine. This is an incorrect and potentially dangerous assumption.

 

[steveray]

505.2​

A mezzanine or mezzanines in compliance with Section 505.2 shall be considered a portion of the story below. Such mezzanines shall not contribute to either the building area or number of stories as regulated by Section 503.1. The area of the mezzanine shall be included in determining the fire area.

That might be your answer...

 

[Yankee Chronicler]

505.2​

A mezzanine or mezzanines in compliance with Section 505.2 shall be considered a portion of the story below. Such mezzanines shall not contribute to either the building area or number of stories as regulated by Section 503.1. The area of the mezzanine shall be included in determining the fire area.

That might be your answer...

1. It's not an intermediate level between the floor and ceiling of a single story.

2. It's not located within a room or space.

It's not a mezzanine. It's a second story bridge.

 

[RLGA]

What are the occupant loads of the accessory classrooms (i.e., orange areas)?

If they are Group A-3 occupancies, then Condition 3 of Section 903.2.1.3 will apply regardless of whether the blue area is considered a mezzanine or not, which I would not classify as a mezzanine anyway, since it appears to be necessary for the means of egress and accessibility for the classrooms.

 

[RLGA]

Additionally, as a further note, if the classrooms are not classified as Group A-3 but are not separated from the Group A-3 occupancy as per Section 707.3.10, then the classrooms become part of the Group A-3 "fire area" and Condition 3 is triggered.

 

[bseck]

There is more to a space being a mezzanine that just 1/3 of the area. 1/3 of the area of WHAT? Definition:

Well I hadn't necessary defined the area itself because as it currently stands, it's just an extension of the lobby.

Too many architects think they can label anything as "Mezzanine" and that makes it a mezzanine. This is an incorrect and potentially dangerous assumption.

Well this is why I ask, I didn't want to just label it a mezzanine if it wasn't. And my own curiosity was stemmed from trying to troubleshoot a potential solution to not have to sprinkle the building if I could since 903.2.1.3 prohibits multi-story fire areas from being non-sprinkled. Thank you for the response.

 

[bseck]

What are the occupant loads of the accessory classrooms (i.e., orange areas)?

If they are Group A-3 occupancies, then Condition 3 of Section 903.2.1.3 will apply regardless of whether the blue area is considered a mezzanine or not, which I would not classify as a mezzanine anyway, since it appears to be necessary for the means of egress and accessibility for the classrooms.

34 & 27 each. But this is a net factor and I haven't placed any kind of tables & chairs in so it'll probably lower when that happens.

Additionally, as a further note, if the classrooms are not classified as Group A-3 but are not separated from the Group A-3 occupancy as per Section 707.3.10, then the classrooms become part of the Group A-3 "fire area" and Condition 3 is triggered.

They would be classified as A-3. But this is also why I proposed if the floor & walls were fire rated, would they be their own fire areas separate from the double height prayer hall?

 

[steveray]

1. It's not an intermediate level between the floor and ceiling of a single story.

2. It's not located within a room or space.

It's not a mezzanine. It's a second story bridge.

But even if it was, it would be included in the fire area and I think the question was getting out of sprinklers....

 

[RLGA]

34 & 27 each. But this is a net factor and I haven't placed any kind of tables & chairs in so it'll probably lower when that happens.

I assume a net factor of 20 square feet per occupant, correct?

They would be classified as A-3. But this is also why I proposed if the floor & walls were fire rated, would they be their own fire areas separate from the double height prayer hall?

If separated, then they would be classified as Group B if they are only for adult education. However, if used for education through the 12th grade, per Section 305.1.1, the classrooms are considered Group A-3 occupancies. Thus, you have a Group A-3 "fire area" on a floor other than a level of exit discharge; therefore, Condition 3 would apply.

Keep in mind that if you provide the 2-hour separation, any construction that supports that separation must also have a 2-hour fire-resistance rating.

 

[bseck]

I assume a net factor of 20 square feet per occupant, correct?

Yup, that's correct.

If separated, then they would be classified as Group B if they are only for adult education. However, if used for education through the 12th grade, per Section 305.1.1, the classrooms are considered Group A-3 occupancies. Thus, you have a Group A-3 "fire area" on a floor other than a level of exit discharge; therefore, Condition 3 would apply.

Keep in mind that if you provide the 2-hour separation, any construction that supports that separation must also have a 2-hour fire-resistance rating.

Ah I see what you're saying now. So any and all A-3 occupancies not on the first floor or has any kind of direct access to a public way would be required to be sprinkled? (or at min. just that fire area?)

 

[RLGA]

Ah I see what you're saying now. So any and all A-3 occupancies not on the first floor or has any kind of direct access to a public way would be required to be sprinkled? (or at min. just that fire area?)

Per Section 903.2.1.3, the second story would need to be sprinkled, and any stories between the Group A-3 occupancy, including the level of exit discharge serving that story, would need to be sprinkled. Thus, in your situation, the entire building would need to be sprinkled.