Occupant Load Calc for A-2 Restaurant

[ccanney]

Hello,
We are currently in the plan check phase for a new ground up restaurant and have received a plan check comment from the building department noting that we need to use gross floor areas when determining occupant load and include all restrooms, hallways, storage rooms, electrical and mechanical rooms, etc. The occupancy of the space is A-2 and overall use of the space is dining with unconcentrated tables and chairs and booth seating. Per CBC Table 1004.5 the occupant load for the dining areas would 15sf/person Net, not gross. (booths calculated per linear foot) The definition of net floor area clearly omits unoccupied accessory areas such as corridors, stairways, ramps, toilet rooms, mechanical rooms and closets. While we do have accessory uses such as dry storage, commercial kitchen and chefs offices that have their occupant loads calculated on gross areas per the associated load factors from 1004.5 I do not believe that this should trigger the restrooms and mechanical rooms, etc. to be included in the occupant load for the building. We have built out numerous restaurants over the years and have never included these spaces as the are unoccupied accessory spaces serving the main use of the building. However, I am struggling to find clear notation in CBC Section 1004 that states this. Any suggestions appreciated.

 

[arwat23]

In my opinion (I don't know how to back this all up with code... but I've gotten Building Officials agree with this), it depends on the layout of the space. I typically exclude restrooms, corridors, etc. only when they are adjacent to, and only accessible by passing though, functions with a net load factor. If you have to pass through a function with a gross load factor to access the restroom (crappy example: restrooms that are accessed by passing through, and are immediately adjacent to, a kitchen), then you should include restrooms in the gross area. I can also see an argument for including hallways in the gross load factors, but again, that depends on the layout of the space.

Mechanical rooms would have a load factor of 300 for "mechanical equipment room" (top of Table 1004.5). I see no way of excluding those areas. Same with storage rooms ("accessory storage areas" - 300 Gross). These are typically separate, defined spaces with a separate function to the unconcentrated spaces and can be included in the occupant load. I do see an argument for small storage areas such as closets being excluded if accessed only from a space with a net function, but if the storage space is a larger room, then my bet is you need to include those areas in your occupant load.

Here's something I dealt with recently. Office building, so a bit different, but the concept is the same. We had a large conference room with a restroom that was only accessible from that conference room. We were able to exclude that restroom from occupant calcs since it was accessed only from an area with a net load factor. However, the restroom immediately adjacent to that conference restroom (shared a wall but is accessed from the corridor) had to be included in the 150 gross load factor for business areas.

 

[Yankee Chronicler]

Restrooms are never counted toward floor area for calculating occupant load. Mechanical rooms are calculated as Industrial Areas per IBC Table 1004.5.

 

[arwat23]

Restrooms are never counted toward floor area for calculating occupant load. Mechanical rooms are calculated as Industrial Areas per IBC Table 1004.5.

CBC is different then. Restrooms are included in gross load factors (see Ch2 definitions in the CBC for "Floor Area, Gross", compared to "Floor Area, Net").

Edit: At least, that's my understanding. Net factors explicitly remove restrooms. Gross doesn't, and I've been told by multiple plans examiners in CA that restrooms should be included in gross areas. If there's a way to exclude them, please share, because it has caused me some headaches on a few projects and I'd love to exclude them if possible

 

[ccanney]

Thanks,
I agree with your interpretation that as the restrooms are access from the main dining room they should be excluded as they would be part of the net area calculation. I think I can make this argument with the plan checker. Other spaces that are directly adjacent to office or storage uses, which would use a gross area calculations, would then be included in that specific calc. Thanks for the feedback.

 

[Yankee Chronicler]

CBC is different then. Restrooms are included in gross load factors (see Ch2 definitions in the CBC for "Floor Area, Gross", compared to "Floor Area, Net").

Edit: At least, that's my understanding. Net factors explicitly remove restrooms. Gross doesn't, and I've been told by multiple plans examiners in CA that restrooms should be included in gross areas. If there's a way to exclude them, please share, because it has caused me some headaches on a few projects and I'd love to exclude them if possible

Sure, towards gross areas -- such as Business. For that you don't even leave out the area occupied by stairs and elevators. I thought the question was about A-2 Assembly.

 

[Joe.B]

I was taught that everything has to be accounted for one way or another. Start with the total, break it up into clear occupancy (or use) areas, include appropriate areas that you can (such as the bathroom attached to the conference room example), then look for any exempt areas. I don't know if that's the "right" way or the best, but it makes sense to me and seems to work for plan check purposes.

 

[arwat23]

Sure, towards gross areas -- such as Business. For that you don't even leave out the area occupied by stairs and elevators. I thought the question was about A-2 Assembly.

"Occupancy Classification" (Chapter 3) is different than "Function of Space" (section 1004). An A-2 classified space can have functions with a gross load factor (a restaurant with a small manager's office, for example). See IBC/CBC 1004.3 vs 1004.4.

The way I understand this is that if an accessory space like a restroom is accessed from a space with a function that has a gross load factor, that accessory space should be included in the occupant load factor. "Occupancy classification" has no bearing on occupant load itself. If it did, why not just show Table 1004.5 with occupancy classifications instead like how UPC/CPC Table 4-1 shows?

Is my understanding of this incorrect?

 

[JPohling]

Here is an example of how we handle the occupant loads. fixed booths as well as tables and chairs. bathrooms get a zero
original image was difficult to read. try this one.

And yes, no occupant load attributed to rest rooms.

 

[Yankee Chronicler]

"Occupancy Classification" (Chapter 3) is different than "Function of Space" (section 1004). An A-2 classified space can have functions with a gross load factor (a restaurant with a small manager's office, for example). See IBC/CBC 1004.3 vs 1004.4.

The way I understand this is that if an accessory space like a restroom is accessed from a space with a function that has a gross load factor, that accessory space should be included in the occupant load factor. "Occupancy classification" has no bearing on occupant load itself. If it did, why not just show Table 1004.5 with occupancy classifications instead like how UPC/CPC Table 4-1 shows?

Is my understanding of this incorrect?

Maybe my understanding is incorrect, but over my 50+ year career I have never counted toilet rooms in assembly occupancies toward occupant load. After all, toilet rooms are considered to be "not normally occupied" areas and, since they serve the actual assembly areas, for the most part there aren't additional people in the building just to use the toilet facilities. The same occupants you count as occupants in the dining area or theater are the same occupants who will be using the toilet facilities, so why double-count them?

 

[bill1952]

I think its the Gatlin Brothers who sing about "California's a brand-new game". Maybe people can be on the toilet and at their table at the same time. Just saying my colleagues who deign theatres in California have to follow code interpretations I've never imagined.

 

[Sifu]

Maybe my understanding is incorrect, but over my 50+ year career I have never counted toilet rooms in assembly occupancies toward occupant load. After all, toilet rooms are considered to be "not normally occupied" areas and, since they serve the actual assembly areas, for the most part there aren't additional people in the building just to use the toilet facilities. The same occupants you count as occupants in the dining area or theater are the same occupants who will be using the toilet facilities, so why double-count them?

Agree with your understanding, but even have a hard time understanding why they would be counted in a gross area condition, but I know they are. IMHO, in all but extreme circumstances (large multi-user toilet rooms) if the OL is close enough for the toilet rooms to make a difference a way could probably be found to make them not make a difference...

When I have a mix, I try to ascertain what the toilet rooms are primarily serving. In an A2, with a mangers office, a storage room, a coat closet....the toilets are primarily serving the diners, so I don't count them.

I arrived at that philosophy from various posts over the years on this here forum and I like it. Seems like RLGA is to thank for most of it.

 

[arwat23]

Maybe my understanding is incorrect, but over my 50+ year career I have never counted toilet rooms in assembly occupancies toward occupant load. After all, toilet rooms are considered to be "not normally occupied" areas and, since they serve the actual assembly areas, for the most part there aren't additional people in the building just to use the toilet facilities. The same occupants you count as occupants in the dining area or theater are the same occupants who will be using the toilet facilities, so why double-count them?

Quick question. In business areas, would you include the restrooms in OL calcs? It's a gross load factor, so by my understanding you would even though those spaces aren't typically occupied and the occupants are counted elsewhere (or maybe I'm just horribly mistaken lol...).

My understanding is that the issue isn't the classification. It's the layout and association with the fiction of the space (where the toilet rooms are or who uses them) that's the issue.

If the restrooms are directly attached to a function that uses a net load factor (example: restrooms in lobbies of a theater), then yes, completely ignore the restrooms when calculating occupant load. I completely agree with that. However, if there is a restroom that's for employee use only that's directly attached to a space with a gross load factor, then shouldn't that be included in the gross load factor. Obviously it wouldn't be included in the net area, but it's being used by people who are in the gross load factor areas.

Tbh, I've never gotten an exact, clear-cut answer on this. I've had building officials disagree with each other, plan reviewers who adamantly disagree with their building officials... I've even gotten one building official to give me three completely different answers on something similar to this.

Just the other day, a colleague of mine got called out for not showing office break rooms and small lobby with a net load factor (unconcentrated). Asked the fire department? They agreed with the comment. Asked the building official? They disagreed with the comment.

 

[Yankee Chronicler]

Quick question. In business areas, would you include the restrooms in OL calcs? It's a gross load factor, so by my understanding you would even though those spaces aren't typically occupied and the occupants are counted elsewhere (or maybe I'm just horribly mistaken lol...).

The 2021 IBC Commentary offers this:

The use of net and gross floor areas as defined in
Chapter 2 is intended to provide a refinement in the
occupant load determination. The gross floor area
technique applied to a building only allows the deduction
of the exterior walls, vent shafts and interior courts
from the plan area of the building.

Going back to BOCA days, it has long been my understanding that the overriding concern (since these occupant load factors are found in chapter 10) is ensuring that a building or story has -- and will have in the future -- adequate egress capacity. The types of occupancies that are listed as using a gross floor area for calculation are typically occupancies that are more likely to undergo alterations and changes of use in the future.

I don't lose sleep over why the table is set up as it is; I just use it. For a restaurant, I see no reason to add the area of two toilet rooms to the area of a 150 s.f. office in calculating the occupant load. The toilets serve the building. If the dining room seats 150 people, it's unlikely that adding one more occupant for the office and two or three more for the kitchen will make a difference. Why add in the toilet rooms?

 

[arwat23]

Going back to BOCA days, it has long been my understanding that the overriding concern (since these occupant load factors are found in chapter 10) is ensuring that a building or story has -- and will have in the future -- adequate egress capacity. The types of occupancies that are listed as using a gross floor area for calculation are typically occupancies that are more likely to undergo alterations and changes of use in the future.

Another concern, more so for CA I believe, is plumbing fixture count. The Plumbing Code can really mess you up depending on the classification (CA does not adopt IBC Ch 29). For example, if you have 200 occupants in a B occupancy, then you only need 6 WC total. Go up to 201 occupants? Guess what? You just massively increased the WC count to 11... Makes me want to pull my hair out (I mostly do TIs, and this makes my life hard sometimes).

But that's getting off topic... Thanks for the replies!