how do you calculate occupant load...


This is for a three story condominium with 6 units...First story on grade is parking...the second and third stories each have three units each...I'm looking at this table (table 10-A) in the los angeles building code and found out that the occupancy load factor for our project is 300 i divide that from the square footage of the individual units or the total floor area of each story...

Dec 20, 05 7:03 pm

Short answer: divide the area of floor of each unit by the load factor to get the population.

Dec 20, 05 8:15 pm

Population of that one area, that is.

Dec 20, 05 8:15 pm

Janosh, thanks...i was about to go to the building dept., which i don't mind 'cause i get to see the pretty ticket-girl, just to ask them this,

Dec 20, 05 8:36 pm

hey, read your code book carefully, and see if you have a statewide code too. generally, you use common sense - ie: in residential, it's unlikely anyone will be living in the closet, bathroom or hallway, so these areas are excluded from your area calcs, however, look carefully to see how your code asks for 'gross' or 'net' s.f. in the calculation.

i think the gross vs net calc is what you are asking about, no?

Dec 21, 05 10:23 am


is this correct?...I use the gross occupant load to determine the number of exits for each story...and the net to determine the number of exits for each unit

Dec 21, 05 12:31 pm
el jeffe

not quite. i think what gruen means by gross vs. net has to do with the floor area under consideration. the gross floor area yields one number, the net floor area (in terms of occupancy calculations under the UBC) is typically less due to certain areas being excluded.
you are correct in thinking that you can aggregate the occupant load in each unit to achive a load for each floor, which will then tell you what your min. exit width(s) would need to be.
Just to save you the agony of making the following mistake: you don't add the occupant load from each floor above as they exit into a stairway or other exit. It is called cascading and hasn't been a part of the codes for a few years now.
Bonus - the IBC doesn't differentiate between gross & net for occupant load calcs now.

Dec 21, 05 2:17 pm
Devil Dog

el jeffe. . .
"Bonus - the IBC doesn't differentiate between gross & net for occupant load calcs now."

i'm not sure you're correct. look at section 1004 and table 1004.1.2 of the IBC. that table gives load factors based on either net or gross depending in the use.

Dec 21, 05 4:17 pm
el jeffe

Extra Bonus - Devil Dog is correct, my bad. Thanks.

Dec 21, 05 4:25 pm

el jeffe. what version of the ibc doesn't differentiate between gross and net?

ibc 2003 uses gross or net load factors (dependant on area type, most are gross) in the table 1004.1.2. this is one of the more confusing code concepts. if you read the commentary to IBC 2003 it defines net as excluding bathrooms, among other things. one would infer that one should count bathrooms using the gross occupant load factors. For residential occupancies (apply the gross load factor), i typically do a room by room count (using the greater of the calculated vs. anticipated load for the room) for exit widths and corridor loading. i'll include restrooms using the residential loading factors. on a recent project, this analysis bumped my corridor load over 10 occupants which triggering a requirement to rate the corridor. i sat down with the building official who explained that the restrooms were accessory to the bed room units (not to be confused with accessory use areas from chapter 3) and that i could exclude the loads. This brought the corridor loading below 10 which was good, but left me a bit murky on the code intent.

My experience has been that plan reviewers really like a code specific floor plan with little boxes in each room showing load factors and loads.

Dec 21, 05 5:53 pm

sorry, el jaffe. i skipped the subsequent posts regarding net vs gross.

Dec 21, 05 6:13 pm

good work guys.

Dec 22, 05 3:26 pm

The Los Angeles Building Code is based on the UBC. Net vs. Gross shouldn't really matter for the project dammson is describing since things are pretty simple until you get over 10 occupants.

Dec 22, 05 5:02 pm

I found out from the plan checker yesterday than i need not be concerned with net or gross calcs for this specific project because, like what Janosh said, it's relatively simple if the occupant load is below 10...plan checker told me to just divide the floor area of a unit by the occupant load factor. Technically, that's gross.

Dec 22, 05 6:58 pm

*that instead of than

Dec 22, 05 6:59 pm

Love those people to square feet square feet, gross square feet. Always wanted to meet the guy who figured out how many people there are to square feet.....I also wondered if the guy had a third eye. Then I also wondered if his brother worked for the NFPA....and did their square feet calculations...Maybe he has a square head.

Dec 22, 05 7:09 pm


I'm calculating massive amounts of occupancy loads here, and I've always thought that if you got a fraction of people, you had to round up, because quite frankly, you can't have 1/10th of a person. Is this correct? Or are you allowed to round down? Doesn't matter too much in the grand scheme of things but we are debating it and I'm doing a little survey....

Mar 16, 07 9:59 am

gotta round up...

Mar 16, 07 10:17 am
vado retro

max occ load for one exit is 10.
min number of occ w/ 2 exits-11 to 500
lenght of common path of egress travel before 2 paths are required is 75' sprinklered or non.

Mar 16, 07 10:58 am

^^^all contingent on type of occupancy

Mar 16, 07 2:14 pm


more info on pretty ticket girl please

Mar 16, 07 6:03 pm

mdler's ramping up to a comment involving the pretty ticket girl and the term "gross load"

you've been warned.

Mar 16, 07 6:06 pm
vado retro

referring to r-2 occupancy loads as this is the subject of the thread.

Mar 16, 07 7:14 pm

lets keep the sexual inyourendos off of Archinect

Mar 16, 07 7:28 pm

talk about occupant load....

Mar 16, 07 8:15 pm

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