# occupant load calculations for multiple occupancies



## steve shaw (May 29, 2018)

the logic of rounding up occupant load calculations makes sense. but if this is applied to each individual occupancy group in a multiple-occupancy tenant space, such a tenant would be penalized relative to single-use and there could be numerous 'phantom occupants'.
is there any reference limiting the 'rounding up' to the final / total count?
thanks.


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## cda (May 29, 2018)

Welcome

Green or Red chili??


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## cda (May 29, 2018)

“”there could be numerous 'phantom occupants'.””

As in you calculate 1.5 people, and there is only one???

Normally it does not matter.

Where it does, than argue the point

As in one person adds say, another exit, assembly occupancy, panic hardware, sprinkler or fire alarm system,,, ETC


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## RLGA (May 29, 2018)

There is no requirement that occupant loads must be rounded up. Typically, I round down; however, I have rounded up on occasion when the decimal number is X.9 or higher.

For areas where the occupant load is based on gross floor area, I take the total area of all spaces (i.e., gross floor area) and then divide by the occupant load factor and round down--that is the occupant load for the story. Where multiple load factors are used per story, I determine each as described, then sum the totals of each to determine the occupant load for the story. For areas using net floor area, I determine by each space and round down and then add them to the other totals based on gross floor areas to get the occupant load for the story.

Each space is required to provide for the means of egress of the space's occupant load per IBC Section 107.2.3, so I determine the occupant load of each space to show compliance (rounding down as I've mentioned previously), but I do not add up the rounded occupant loads of each space to determine the occupant load of a story.


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## JBI (May 29, 2018)

Occupant load is used primarily to size the means of egress, so adding a few more people may require a larger MOE. 
In the extreme it could raise additional code requirements as noted above by cda. The language in 1004 of the IBC allows an increase in occupant load based on any such additional requirements and also a decrease based on 'actual number'. 
All the flexibility an applicant might need to mitigate any possible conflicts are built in.


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## steve shaw (May 29, 2018)

'M' occupant load calc: 29.2 / 'K' load: 6.4 / 'S': 13.4.
if each of these is rounded up before final tally, total is 51; if rounding up applied to total only, total is 49. this makes a huge difference; and we will have (3) 'phantom occupants' versus (1).


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## RLGA (May 29, 2018)

steve shaw said:


> 'M' occupant load calc: 29.2 / 'K' load: 6.4 / 'S': 13.4.
> if each of these is rounded up before final tally, total is 51; if rounding up applied to total only, total is 49. this makes a huge difference; and we will have (3) 'phantom occupants' versus (1).


What are "M," "K," and "S"?


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## steve shaw (May 29, 2018)

RLGA said:


> What are "M," "K," and "S"?


Mercantile, Kitchen, Storage (S1)


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## RLGA (May 29, 2018)

If this were my project, I would have occupant loads for each use per Table 1004.1.2 as 29, 6, and 13, respectively, for a total of 48 occupants.


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## steve shaw (May 29, 2018)

guessing that would be using '.5' as the threshold to round up or down.
if so, are you aware of any way to substantiate this approach?
appreciate your engagement here.


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## steve shaw (May 29, 2018)

cda said:


> Welcome
> 
> Green or Red chili??


... depends on the year and who's cooking ...


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## RLGA (May 29, 2018)

steve shaw said:


> guessing that would be using '.5' as the threshold to round up or down.
> if so, are you aware of any way to substantiate this approach?
> appreciate your engagement here.


As I previously stated, I usually round down regardless of the fractional number. There is nothing to substantiate that approach--or any other approach for that matter--because the IBC does not address fractional numbers in regard to occupant load calculations.


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## steve shaw (May 29, 2018)

RLGA said:


> What are "M," "K," and "S"?





RLGA said:


> As I previously stated, I usually round down regardless of the fractional number. There is nothing to substantiate that approach--or any other approach for that matter--because the IBC does not address fractional numbers in regard to occupant load calculations.


got it.
thanks.


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## mtlogcabin (May 29, 2018)

[A] 107.2.3 Means of egress.
The construction documents shall show in sufficient detail the location, construction, size and character of all portions of the means of egress including the path of the exit discharge to the public way in compliance with the provisions of this code. In other than occupancies in Groups R-2, R-3, and I-1, the construction documents shall designate the number of occupants to be accommodated on every floor, and in all rooms and spaces.

In your case I would add all the numbers and fractions then come up with the total of 49. As previously stated there is nothing in the code to round up except for plumbing fixtures (2902.1.1)


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## steve shaw (May 29, 2018)

mtlogcabin said:


> [A] 107.2.3 Means of egress.
> The construction documents shall show in sufficient detail the location, construction, size and character of all portions of the means of egress including the path of the exit discharge to the public way in compliance with the provisions of this code. In other than occupancies in Groups R-2, R-3, and I-1, the construction documents shall designate the number of occupants to be accommodated on every floor, and in all rooms and spaces.
> 
> In your case I would add all the numbers and fractions then come up with the total of 49. As previously stated there is nothing in the code to round up except for plumbing fixtures (2902.1.1)


thanks for your feedback; good support for arguing against incremental rounding up process.


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## steveray (May 30, 2018)

We round up, but I would have you at 49 as well....What is the huge difference at >50OL?


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## mark handler (May 30, 2018)

California Plumbing Code 2016
422.1 Fixture Count
"...such numbers shall be rounded to the next whole number..."


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## steve shaw (May 30, 2018)

steveray said:


> We round up, but I would have you at 49 as well....What is the huge difference at >50OL?


more than 49 gets us to two exits required.


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## cda (May 30, 2018)

steve shaw said:


> more than 49 gets us to two exits required.




Maybe yes maybe no


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## steveray (May 30, 2018)

Small restaurant or "to go" place?


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## VAC (Aug 4, 2022)

So I read the prior (old) comments. My question is similar regarding rounding up/down, but not exact, so here it is.

When adding up the occupant load for egress, do you *sum* and then _round up_ (like for plumbing -the NFPA is so clear!) or round up for each space and then round up again? 
I (have) always sum and then round up, but just today I was told I'm supposed to do it the other way, which doesn't make a lot of sense to me but hey, I've been wrong before.
Any thoughts or where I can find clarification on the IBC... if any? Nothing on 107 or 1004 about this that I can see, but perhaps somewhere else? or am I doomed to make that change? rounding up twice puts me over 50 occupants.... and sigh, everything else.


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## Sifu (Aug 4, 2022)

I would sum and then round up...but, if I have a space where that extra 1/2 person is going to change egress or fixtures I find a way to lose that 1/2 person.


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## Paul Sweet (Aug 4, 2022)

Each space has to have adequate exits for its occupants, so you should round up for each room.  I would do a separate calculation with the total areas for each occupancy for building exits and plumbing.  That way you wouldn't have a lot of "phantom" occupants fro rounding many 1.5 person offices up to 2 each.


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## mtlogcabin (Aug 4, 2022)

Sum and then round up is how I have always done it for the entire floor. Basically when you are doing a room by room calculation it is a net calculation versus a gross calculation. If the entire floor is a "B" occupancy and you calculate the entire floor at 100 sq ft per person you will probably not exceed the sum of all occupiable spaces when adding up all the fractional amounts' and then rounding up to the next whole number. 

[BE] FLOOR AREA, GROSS. The floor area within the inside perimeter of the exterior walls of the building under consideration, exclusive of vent shafts and courts, *without deduction for corridors, stairways, ramps, closets, the thickness of interior walls*, columns or other features. The floor area of a building, or portion thereof, not provided with surrounding exterior walls shall be the usable area under the horizontal projection of the roof or floor above. The gross floor area shall not include shafts with no openings or interior courts.

[BE] FLOOR AREA, NET. The actual occupied area not including unoccupied accessory areas such as corridors, stairways, ramps, toilet rooms, mechanical rooms and closets.


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## VAC (Aug 4, 2022)

mtlogcabin said:


> Sum and then round up is how I have always done it for the entire floor. Basically when you are doing a room by room calculation it is a net calculation versus a gross calculation. If the entire floor is a "B" occupancy and you calculate the entire floor at 100 sq ft per person you will probably not exceed the sum of all occupiable spaces when adding up all the fractional amounts' and then rounding up to the next whole number.
> 
> [BE] FLOOR AREA, GROSS. The floor area within the inside perimeter of the exterior walls of the building under consideration, exclusive of vent shafts and courts, *without deduction for corridors, stairways, ramps, closets, the thickness of interior walls*, columns or other features. The floor area of a building, or portion thereof, not provided with surrounding exterior walls shall be the usable area under the horizontal projection of the roof or floor above. The gross floor area shall not include shafts with no openings or interior courts.
> 
> [BE] FLOOR AREA, NET. The actual occupied area not including unoccupied accessory areas such as corridors, stairways, ramps, toilet rooms, mechanical rooms and closets.


Thank you! agree! and this is how I've done it, (entire floor as B) but I was stumped about the request. 
It was in particular regarding a "B" occupancy with a Conf. Room, (accessory only 200 sf) and a couple of other areas like that (a small exercise room and a lounge room) so first it was that each room's use is different, so I couldn't classify them as B. I had to calculate load (based on use) individually (fine, I get that even though I didn't think it was necessary but what do I know?!....)

Then, came the rounding up for each, which was news to me based on how I had have done it...(currently using IBC 2018) If I calculate the load based on use for each room, I end up with fractions (like Conf. Rm would be 13.33) so rounding up each and then rounding up again puts me over 49... 

Maybe I need a chat with the AHJ


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## VAC (Aug 4, 2022)

Paul Sweet said:


> Each space has to have adequate exits for its occupants, so you should round up for each room.  I would do a separate calculation with the total areas for each occupancy for building exits and plumbing.  That way you wouldn't have a lot of "phantom" occupants fro rounding many 1.5 person offices up to 2 each.


I get that and pretty much how I've done it for years. The issue is I have been asked to classify the use of each room differently (Conf. Rm and small employee lounge, etc as "A") even though the space is "B". Which now creates a few "phantom" occupants... hence my dilemma. Thanks for your input. At least I know I haven't been doing something unique


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## Sifu (Aug 5, 2022)

Who asked you to _*classify*_ them as A?  Small conference rooms would not be classified as A, they would be B or the same as the main occupancy.  But, as you say, load is based on use, not classification so in your application it wouldn't matter.  But, if you classify them as A, then you have to account for that in your mixed-use strategy.


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## ADAguy (Aug 8, 2022)

Is there a maximum distance allowed from an egress door to corridor for a room with 49 occupants?


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## mtlogcabin (Aug 8, 2022)

Depends on Occupancy Type and if sprinkled or not. Anywhere from 25 feet to 125 feet


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