# Help Understanding Section 508 and Aggregate accessory occupancies



## EasilyConfused (Mar 7, 2016)

*508.2.1 Area limitations. *

Aggregate accessory occupancies shall not occupy more than 10 percent of the _building area _of the _story _in which they are located and shall not exceed the tabular values in Table 503, without _building area _increases in accordance with Section 506 for such accessory occupancies.

Am I confused again?

I have this building that I'm attempting to break up into it's various occupancies.

The way I'm approaching it is Mixed use with some occupancies that would be accessory to the business portion of the building.

So, half of the building is A3 and the other half is B.

Within the B portion of the building there is a small conference room that I'm calling an accessory use space (because it falls under the B classification because not required to be Assemble because of 303.1.2 "small assembly spaces".

There is also a computer lab that I'm calling as accessory Educational (for lack of anything better to call it) because technically it's not required to be classified as educational because only for adults.... and therefor business because of size. Except for the fact that it's still "Educational" for purposes of table 1004.1.2.

So, now I have what I believe to be 1 large A-3 space, 1 large B space that contains multiple types of "accessory spaces" that are "B" as far as occupancy is concerned but something else as far as Table 1004.1.2 is concerned.

Since they all are Business as far as occupancy is concerned, do they individually need to meet the 10% rule?

What about combined... "aggregate" of the same types of spaces. (Say I had two separate Business Accessory Assembly rooms that were small conference rooms. Is the aggregate adding those two spaces areas together and that can't be over 10%. That would probably make sense to me.

​Or, would it be that the aggregate would require that all the accessory spaces even though some of them have different functions (say accessory storage and accessory assembly) have to be added together and the combined can't be over 10%.

As far as 508 general questions go, I'm not sure how to handle the potential "overlap" between calling a space "Mixed Use" "Accessory Use" and "Non Separated" or "Separated". I've set this building up to Be Mixed use. I've also set this up to be classified as Non Separated. I don't understand how the "Accessory" aspect works into this. The way I'm thinking about this is building is 1/2 A-3, 1/2 B, with all these smaller, what I'm calling "Accessory" spaces on the business side where none of the spaces take up more than 10% of the floor area INDIVIDUALLY, with my understanding of Aggregate being only like spaces need to fall under the 10% requirement. If all the spaces fall under the correct occupancy heading irrespective of the 10% rule then there would be no need to classify them as accessory regardless correct?

Wondering if maybe I'm getting Ancillary and Accessory kind of confused.

Hopefully there is an easy way for someone to explain to me how all this works together.

Thanks.


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## cda (Mar 7, 2016)

Step away from the code book. Over analyzing again.

http://www.specsandcodes.com/articles/code_corner/The%20Code%20Corner%20No.%2014%20-%20Building%20Classification%20Part%201%20-%20Occupancies.pdf

http://www.specsandcodes.com/articles/code_corner/The%20Code%20Corner%20No.%2015%20-%20Building%20Classification%20Part%202%20-%20Construction%20Types.pdf

And other fantastic reading::::

http://www.specsandcodes.com/articles/default.html


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## mtlogcabin (Mar 7, 2016)

The A-3 may trigger sprinklers based on the fire area size or occupant load

 508.3.1 Occupancy Classification.

Nonseparated occupancies shall be individually classified in accordance with Section 302.1. The requirements of this code shall apply to each portion of the building based on the occupancy classification of that space.  In addition, the most restrictive provisions of Chapter 9 which apply to the nonseparated occupancies shall apply to the total nonseparated occupancy area.

[F] 903.2.1.3 Group A-3.

An automatic sprinkler system shall be provided for Group A-3 occupancies where one of the following conditions exists:

1.    The fire area exceeds 12,000 square feet (1115 m2);

2.    The fire area has an occupant load of 300 or more; or

3.    The fire area is located on a floor other than a level of exit discharge serving such occupancies.


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## RLGA (Mar 7, 2016)

Accessory occupancies (not uses) are occupancy groups that are accessory to the main occupancy.  If the main occupancy is Group B and you have accessory "uses" that can also be classified as Group B, then you do not have accessory "occupancies."  If your main occupancy was Group B, but you had a large conference room that had an occupant load greater than 50, then it would be classified as a Group A-3 and could be considered an accessory occupancy that would be restricted to the 10% of the building area of the floor in which it was located.


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## EasilyConfused (Mar 7, 2016)

CDA- Thanks for the links. I'll read it.

mtlogcabin- I'm covered. Don't need sprinklers.

RLGA- I need to think this through a little. Pre-ordered your book by the way. You're a good salesman!


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## RLGA (Mar 7, 2016)

Glad to be of some help.


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## EasilyConfused (Mar 9, 2016)

How about this....

I have a building that the main occupancy is Group B.

Half of the building is group B occupancy and half of the building is group A3 occupancy (large "conference" room).

Because the large A-3 designated space is larger than 10% of the total floor area, there is no way it can be classified as Accessory to the B occupancy, and therefor the space & it’s requirements fall under the A-3 occupancy umbrella.

However, within the part of the building that is not designated as A3 (so within the B part of the building (as far as "USE" goes), there is another smaller conference room (under 50 occupants and under 750SF) that will still be classified as assembly for 1004.1.2 purposes but will not be required to be A-3 occupancy. Therefor the space & it’s code requirements will fall under the B occupancy umbrella.

However, if this same space was over 50 occupants and/or over 750SF, but less than 10% of the combined SF of the floor it’s on, then the space would still be classified as assembly (as far as USE goes) AND it would also need to be classified as A-3 for purposes of occupancy goes, BUT because it would be classified as an ACCESSORY OCCUPANCY (as opposed to accessory use, the space would not need to be separated from the B part of the building. Therefor the space & it’s code requirements will fall under the A-3 occupancy umbrella.

Thanks


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## RLGA (Mar 9, 2016)

You were good right up to the last part.  You are correct that a Group A-3 conference space (more than 50 occupants and greater than 750 sq. ft.) within a Group B can be considered an accessory occupancy if less than 10% of the story floor area and does not need to be separated.  However, this assumes that the larger Group A-3 portion of the building is separated from the Group B portion per Table 508.4. For calculating allowable area, the accessory Group A-3 occupancy is considered part of the Group B occupancy per Section 508.2.3.  Since the Group B (with the Group A-3 accessory occupancy) and the Group A-3 portions of the building are separated, then the sum of ratios for those two occupancies cannot exceed 1.


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## EasilyConfused (Mar 9, 2016)

Getting somewhere maybe. Thanks.

So basically what the code is saying is that I can't just go breaking up assembly areas into smaller units to skirt the code (or maybe something along those lines?)

So, If I want to have my one large assembly area, then yes, I'd be allowed some smaller assembly areas into the B part of the building, but don't go thinking about maxing out another assembly space based on the 10% rule.

On the other hand, if I had a huge business space and wanted to add in an assembly area and wanted to figure out just how large I could make it with minimal impact as far as separation is required, then I could do some quick math and just make sure I stay under the 10%?

Where does the code stipulate that the two large separate occupancies would need to be separated per table 508.4?

Wondering this because, for this particular example, I've already established that I don't need to separate these two occupancies (Mixed use, non separated) and I don't need to separate because I have exits from the A3 area directly to the exterior.

Also, not following how to do the math you're describing....

What does "then the sum of ratios for those two occupancies cannot exceed 1." mean. I Don't get it.


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## EasilyConfused (Mar 9, 2016)

Also....

For the time being, want to make sure my understanding for this particular building design is correct.

Building is 1/2 A3 and 1/2 B occupancy.

Inside the B occupancy, I have another Assembly USE space, that will be classified as B occupancy, with A use (for figuring occupant load), because this "A"space is less than 50 people and less than 750SF, So, the space will fall under the B occupancy umbrella when determining it's code requirements.

Yes, I'm repeating myself.... just want to make sure I'm understanding this.


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## cda (Mar 9, 2016)

> Also....For the time being, want to make sure my understanding for this particular building design is correct.
> 
> Building is 1/2 A3 and 1/2 B occupancy.
> 
> ...


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## mtlogcabin (Mar 9, 2016)

What is the square footage and occupant load of each occupancy group for this project? Because you have an A-3 and a B use occupancies using the non-separated may not be the best option.


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## JBI (Mar 9, 2016)

Or just sprinkler the whole damn thing and build it as Type IA construction, all problems solved.


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## EasilyConfused (Mar 9, 2016)

mtlogcabin & JBI- Already hashed out this I think. But I can use some practice!

Sprinklers not an option at this point and not required.

"A-3" Occupancy Area is 2475 SF

"B" Occupancy area is 2283 SF (combined of B, A, E, and S use areas).

Exits from A-3 area are directly to exterior of building.


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## EasilyConfused (Mar 9, 2016)

cda- point taken.


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## mtlogcabin (Mar 9, 2016)

If the total occupant load of the entire fire area exceeds 300 then you have to sprinkle the entire structure

The A-3 OL can 7 sq ft per person or 15 depending if it is a dance hall or a library.

A fire area  id defined as

FIRE AREA. The aggregate floor area enclosed and bounded by fire walls, fire barriers, exterior walls or horizontal assemblies of a building. Areas of the building not provided with surrounding walls shall be included in the fire area if such areas are included within the horizontal projection of the roof or floor next above.

Since sprinklers are not an option I don't want you to miss another section that could require them


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## EasilyConfused (Mar 9, 2016)

I'm covered. That's my story and I'm sticking to it. Enough said.

Seriously though, total building occupant load is 207 (@ 15 net for assembly unconcentrated tables & chairs which this is) within the "Fire Area". Thanks for giving me another term to have to come to terms with. Isn't this fun?

What you bring up concerns me for another renovation project I am working on.

Total RENOVATED occupant load is 318. Unrenovated occcupant load is another 34 occupants +/-.

Are you saying that because the occupant load is over 300, that by default, the building will need to be sprinklered? Or would this only be the case for new construction? Hoping I don't have to come up with a way to argue this. Sprinklers are not an option for this building either   .


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## cda (Mar 9, 2016)

> I'm covered. That's my story and I'm sticking to it. Enough said.Seriously though, total building occupant load is 207 (@ 15 net for assembly unconcentrated tables & chairs which this is) within the "Fire Area". Thanks for giving me another term to have to come to terms with. Isn't this fun?
> 
> What you bring up concerns me for another renovation project I am working on.
> 
> ...


You have to read the entire book!!!

Depends on occupancy type

Than under occupancy type,,,, than the qualifiers per occupancy

http://publicecodes.cyberregs.com/icod/ibc/2012/icod_ibc_2012_9_par015.htm


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## mtlogcabin (Mar 9, 2016)

> What you bring up concerns me for another renovation project I am working on.
> 
> Total RENOVATED occupant load is 318. Unrenovated occcupant load is another 34 occupants +/-.
> 
> Are you saying that because the occupant load is over 300, that by default, the building will need to be sprinklered? Or would this only be the case for new construction? Hoping I don't have to come up with a way to argue this. Sprinklers are not an option for this building either   .


Start with the IEBC for an existing building. The sprinklers may not be required for a renovation. Change of use may still trigger them


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## JBI (Mar 10, 2016)

Last point I'll make on this, Easily Confused you have to stop using an E classification for anything that is not a regular school curriculum up to the 12th grade (see definition/description of E Occupancy). Training and skill development is typically a B Occupancy (see definition/description of B Occupancy).


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## EasilyConfused (Mar 10, 2016)

CDA & MT Logcabin- thanks.

JBI- Did I refer to E occupancy somewhere in the discussion incorrectly. Could be. Yes, I just recently figured out that E was "only" for grade school applications. Thanks.


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