Multi Story area with Stacked Mezzanines

[blindcheesecake]

We have a 2 story UL area building with a set of mezzanines in an open room. Its set up with a ground floor/ mezzanine / second floor / second mezzanine. We need the floor to be a floor as it has enclosed offices & restrooms

https://flic.kr/p/2qSwjcS

How would you count the area of the area per 505.2.1 - IBC 2021

This is all one room / space. IBC 505.2.1 stats that is the floor area of the room / space in which its located.

My interpretation is (GROUND FLOOR + SECOND FLOOR) / (GROUND FLOOR MEZZANINE / SECOND FLOOR MEZZANINE)

The other interpretation is each mezzanine is tied to its designated floor. So to get the area of the second floor mezzanine larger, I would have to increase the area of the second floor. Problem with this is how is this a safer space by having more floor area which would be unprogrammed and open to the tenant doing whatever up there.

 

[RLGA]

In my opinion, the area on the left is a single-story space with four mezzanines, with the one mezzanine on the right having direct egress to the second story.

Just FYI, the total area of all mezzanines in the room on the left cannot exceed 1/3 the floor area of the room in which they are located. The floor area of the mezzanines does not count toward building area.

 

[walker.t]

We need the floor to be a floor as it has enclosed offices & restrooms

Not quite sure to what you are referring when you said you need the “floor” to be a “floor” - maybe the thing labeled on the left as “second floor”? You mention it has enclosed rooms so it sounds like you are aware of the requirements for mezzanines to be open per 505.2.3 and I assume you don’t qualify for one of the exceptions.

In my opinion, the area on the left is a single-story space with four mezzanines, with the one mezzanine on the right having direct egress to the second story.

That’s what it looks like to me, the “ground floor” has four mezzanines, three on the left, one of the right.

I was going to suggest that maybe there was a way to analyze this as an atrium but then the mezzanines would become stories and as an unlimited area building (per IBC 507) I think the limit is two stories. Maybe that’s why they said they need the floor to be a floor.

 

[bill1952]

If you slide the "opening" in the 2nd floor to the right, sure looks a lot like 2 floors each with a mezzanine. And can't 2 floors be open?

I've seen and designed a lot of theatres that look conceptually very similar with multiple "balconies", some of which get labeled mezzanine simply for code. I've yet to see a many level theatre - or stadium or arena - treated as an atrium, even though they seem to be.

 

[blindcheesecake]

In the code you can have a floor + mezzanine + floor + mezzanine. I don't think anyone could argue that is incorrect.

Then you can have a 2 story opening per IBC 712.1.9. This section does not mention any thing about a mezzanine and per IBC 505.2 a mezzanine is considered a portion of the story below. So given this the design should be compliant to have the multiple mezzanines in an open 2 story space.

This particular use is an industrial use that needs the 4 levels. Its a rather large building and its just a small section with the mezzanines. Its an unlimited area building II-B construction for cost. I know a I-A would make this easy.

The unlimited area building per II-B construction is limited to 2 floors. The second floor in the diagram would connect through walkways from one side to the other (not shown in diagram above; imagine floor 2 is built like a doughnut. Floor on every side of the wall, just open in the middle. The mezzanines are isolated to the left side (minus required egress stairs)

The mezzanines are too large for it to be 3 mezzanines, so one of them needs to be a floor. They are mezzanines not equipment platforms. The IBC allows you to go up to 1/2 per exception 2 of 505.2.1.

The start of 505.2.1 Area limitation stats that its the "floor area of the room or space in which its located"

So it leaves the gap in the code. Is it the equation for the 1/2 limitation:
a. (Mezz 1+Mezz 2) divided by (Floor 1 + Floor 2)
b. OR separated in to two separate calculations
1. Mezz 1 divided Floor 1
2. Mezz 2 divided Floor 2
c. (Mezz 1 + Mezz 2) divided by (floor 1 only)

If its B, then we are going to make floor 2 larger, but still open. Thinking logically a larger building would have more room for combustibles more occupants. It would represent a larger hazard and the option a would in theory be safer. I believe it should be calculated using formula "a" as its all atmospherically the same, and this would be more restrictive. A fire protection engineer thought I was completely our of my mind and the only justifiable is to have 3 levels of mezzanine or if its calculation c. given the intro to this post, I can't find any justification for that. On level 2 there are enclosed restrooms and offices that can only be access through the "room or space" of this mezzanine area. They are over the allowances for the exceptions in IBC 505.2.3 Openness.

I do appreciate everyone taking a look at this. I don't think the code really addresses a situation like this.

 

[Yankee Chronicler]

Of course the code addresses this. The question is, does your argument comply with the code?

You want/need to make that big space two stories, each with one mezzanine. To determine whether or not your idea can comply with the code, start off by removing the two "mezzanines" from consideration and analyze whether or not your design jumps through all the hoops required for a two-story building with a communicating opening between the stories. If so, be sure you can clearly convey that in your construction documents.

If you can establish that, it should then be straightforward to plug the two mezzanines back in, and to ensure that each meets the requirements for mezzanines.

 

[steveray]

What are the size of the mezzanines and do you need an elevator to them?