# Occupant Load



## alacreative (Jun 3, 2014)

When determining the total occupant load of a building, in this case use group B, do you account for corridors or bathrooms when determining the load of each individual space in order to get the total number of occupants?


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## alacreative (Jun 3, 2014)

This is for 2009 IBC


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## fatboy (Jun 3, 2014)

100 gross, includes everything..........


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## alacreative (Jun 3, 2014)

Can you explain what you mean by that?

There are waiting areas and assembly areas within this building as well, so I do need to modify the square footage per occupant calculation for those spaces, correct? So I'm essentially dealing with each space individually when determining the total occupant load?


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## alacreative (Jun 3, 2014)

Can you explain what you mean by that?

There are waiting areas and assembly areas within this building as well, so I do need to modify the square footage per occupant calculation for those spaces, correct? So I'm essentially dealing with each space individually when determining the total occupant load?


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## cda (Jun 3, 2014)

alacreative said:
			
		

> Can you explain what you mean by that?  There are waiting areas and assembly areas within this building as well, so I do need to modify the square footage per occupant calculation for those spaces, correct? So I'm essentially dealing with each space individually when determining the total occupant load?


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, 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.

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


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## cda (Jun 3, 2014)

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, 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.

Gross floor area is that area measured within the perimeter formed by the inside surface of the exterior walls. The area of all occupiable and nonoccupiable spaces, including mechanical and elevator shafts, toilets, closets, mechanical equipment rooms, etc., is included in the gross floor area. This area could also include any covered porches, carports or other exterior space intended to be used as part of the building's occupiable space. This gross and net floor areas are primarily used for the determination of occupant load in accordance with Table 1004.1.1.

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

This area is intended to be only the room areas that are used for specific occupancy purposes and does not include circulation areas, such as corridors or stairways, and service and utility spaces, such as toilet rooms and mechanical and electrical equipment rooms. Floor area, net and gross, is utilized in Table 1004.1.1 to determine occupant load for a space.

Commentary::

http://publicecodes.cyberregs.com/icod/ibc/2009f2cc/index.htm


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## alacreative (Jun 3, 2014)

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


Does this mean I ignore my Assembly without fixed seats (standing space) areas?  The occupant load per floor is determined by its primary function?  Not each individual space?


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## cda (Jun 3, 2014)

alacreative said:
			
		

> Does this mean I ignore my Assembly without fixed seats (standing space) areas?  The occupant load per floor is determined by its primary function?  Not each individual space?


Please restate the question

Give example

I think the answer is no


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## mtlogcabin (Jun 3, 2014)

1004.6 Multiple occupancies.

Where a building contains two or more occupancies, the means of egress requirements shall apply to each portion of the building based on the occupancy of that space. Where two or more occupancies utilize portions of the same means of egress system, those egress components shall meet the more stringent requirements of all occupancies that are served.

No you do not ignore your assembly area


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## alacreative (Jun 3, 2014)

cda said:
			
		

> Please restate the questionGive example
> 
> I think the answer is no


I'm dealing with a B use group building that has multiple tenant spaces.  So, in turn, this building primarily consists of office space, common lounge areas, common waiting areas, storage areas, common kitchen areas, etc.  So, when referring to table 1004.1.1, not all areas of the building are business areas (yes? no?).  So I was assuming that there is a different square footage calculation for the office areas in comparison to some of the common areas (such as the storage areas being 1 person/300 sf and the kitchen areas being 1 person/200 sf as opposed to the 1 person/100 sf for all the office spaces).  Or, are all areas classified as business areas?


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## mtlogcabin (Jun 3, 2014)

> So I was assuming that there is a different square footage calculation for the office areas in comparison to some of the common areas (such as the storage areas being 1 person/300 sf and the kitchen areas being 1 person/200 sf as opposed to the 1 person/100 sf for all the office spaces)


That is correct


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## fatboy (Jun 3, 2014)

If the different area's are larger than what an accessory use would be, then yes, I would consider each use separately, for OL and egress.


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## alacreative (Jun 3, 2014)

Great, thank you all for the quick responses.  Much appreciated!


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## cda (Jun 3, 2014)

imho

you will find the occupant load normally will not push requirements till you get to border line, where one or two people added or subtracted, decides if you need something or not.

So sometimes I do one factor for  whole smaller buildings, if there are not to much of a mixed use, that may drive the occupant load up.


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## north star (Jun 3, 2014)

*& - & - &*

*From the `12 IBC, Section 302.1:*

*"*Structures or portions of structures shall be classified with respect to  occupancy in one

or more of the groups listed in this section..................A room or space that  is intended to be

occupied at different times for different purposes shall comply  with all of the requirements

that are applicable to each of the purposes for which  the room or space will be occupied.

Structures with multiple occupancies or uses  shall comply with Section 508............Where a

structure is proposed for a purpose that  is not specifically provided for in this code,

such structure shall be classified  in the group that the occupancy most nearly resembles,

according to the fire safety  and relative hazard involved."

*& - & - &*


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## alacreative (Jun 3, 2014)

What about conference rooms?  Are these considered an assembly?  And common seating/lounge areas... these aren't necessarily assembly spaces.  Can this be considered business?


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## hlfireinspector (Jun 3, 2014)

*303.1.2 Small assembly spaces. *The following rooms and

spaces shall not be classified as Assembly occupancies:

1. A room or space used for assembly purposes with an

_occupant load _of less than 50 persons and accessory to

another occupancy shall be classified as a Group B

occupancy or as part of that occupancy.

2. A room or space used for assembly purposes that is less

than 750 square feet (70 m2

) in area and accessory to

another occupancy shall be classified as a Group B

occupancy or as part of that occupancy.

IMO I always think about this, the people in the conference room are almost always the people from the building.


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## steveray (Jun 3, 2014)

Another way to think about it is to calc it at the assembly number,(if that is the intended use) if the totalfor the room or space comes out with less than 50, you can just lump it all in with the business spaces...


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## alacreative (Jun 3, 2014)

hlfireinspector said:
			
		

> *303.1.2 Small assembly spaces. *The following rooms andspaces shall not be classified as Assembly occupancies:
> 
> 1. A room or space used for assembly purposes with an
> 
> ...


One thing I always found confusing is the connection between the building use group and individual space classification.  From my understanding and based on the definition above, Chapter 3 Use and Occupancy Classification, defines not only the building classification, but also individual space classification that can help you understand which conversion to use for table 1004.1.1?


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## north star (Jun 3, 2014)

*& ~ & ~ &*

Each space \ room \ area must be evaluated for its intended use.

That's why you can have a multi-occupancy type building \ structure.

An accurate, designed occupant load is a very crucial part of the

overall design & use of a building.

*& ~ & ~ &*


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## cda (Jun 3, 2014)

My shot

Occupancy types the building and spaces in it.

Which is different from the occupant load factor table. That just is used to determine the occupant load of a room.

But indirectly can affect the occupancy type as in A and B, once you hit fifty you fall into a different occupancy.

So,

1. sq foot of building and rooms in it

2. Occupant load

3. Occupancy type


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## alacreative (Jun 3, 2014)

cda said:
			
		

> My shotOccupancy types the building and spaces in it.
> 
> Which is different from the occupant load factor table. That just is used to determine the occupant load of a room.
> 
> ...


Ahhh, I see.

I think essentially what was confusing me was the assumption of determining the Occupancy Use before the Occupancy Load rather than after.


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## alacreative (Jun 3, 2014)

I have another simple question related to this topic that I can't seem to locate within the code.  Once you have your occupant load, how do you determine how many females vs. males?  Split the load?


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## Frank (Jun 3, 2014)

alacreative said:
			
		

> I have another simple question related to this topic that I can't seem to locate within the code.  Once you have your occupant load, how do you determine how many females vs. males?  Split the load?


Assume 50/50 unless have firm data to the contrary

2009 IPC

403.1.1 Fixture calculations. To determine the occupant load of each sex, the total occupant load shall be divided in half. To determine the required number of fixtures, the fixture ratio or ratios for each fixture type shall be applied to the occupant load of each sex in accordance with Table 403.1. Fractional numbers resulting from applying the fixture ratios of Table 403.1 shall be rounded up to the next whole number. For calculations involving multiple occupancies, such fractional numbers for each occupancy shall first be summed and then rounded up to the next whole number.

Exception: The total occupant load shall not be required to be divided in half where approved statistical data indicates a distribution of the sexes of other than 50 percent of each sex.

403.1.2 Family or assisted-use toilet and bath fixtures. Fixtures located within family or assisted-use toilet and bathing rooms required by Section 1109.2.1 of the International Building Code are permitted to be included in the number of required fixtures for either the male or female occupants in assembly and mercantile occupancies.


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## alacreative (Jun 3, 2014)

Frank said:
			
		

> Assume 50/50 unless have firm data to the contrary2009 IPC
> 
> 403.1.1 Fixture calculations. To determine the occupant load of each sex, the total occupant load shall be divided in half. To determine the required number of fixtures, the fixture ratio or ratios for each fixture type shall be applied to the occupant load of each sex in accordance with Table 403.1. Fractional numbers resulting from applying the fixture ratios of Table 403.1 shall be rounded up to the next whole number. For calculations involving multiple occupancies, such fractional numbers for each occupancy shall first be summed and then rounded up to the next whole number.
> 
> ...


Anyone happen to know where this section is located in the 248 CMR - Massachusetts State Plumbing Code?


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## steveray (Jun 3, 2014)

alacreative said:
			
		

> Anyone happen to know where this section is located in the 248 CMR - Massachusetts State Plumbing Code?


While I do not have the section...The number is determined by the AHJ....Local BO...I know we had this discussion here about MA before...Try searching fixture count Massachusetts here on the forum..


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## cda (Jun 3, 2014)

alacreative said:
			
		

> Ahhh, I see.I think essentially what was confusing me was the assumption of determining the Occupancy Use before the Occupancy Load rather than after.


Well sometimes the occupancy type is easy, just by looking at it.

Say a stadium or a school or a hospital


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## cda (Jun 3, 2014)

alacreative said:
			
		

> Anyone happen to know where this section is located in the 248 CMR - Massachusetts State Plumbing Code?


Not into potties so do not know if this helps

http://www.specsandcodes.com/Articles/The%20Code%20Corner%20No.%2033%20-%20Calculating%20Plumbing%20Fixture%20Counts.pdf


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## cda (Jun 3, 2014)

Since helping with design

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http://idighardware.com

http://idighardware.com/about-2/about-me-mobile/


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## el cholo (Jun 5, 2014)

cda said:
			
		

> ....Which is different from the occupant load factor table. That just is used to determine the occupant load of a room.
> 
> ...


So, I've heard of this before.  A tenant build-out space for one company has a large conference room (over 750 sf), the occupant load is counted as 1/15sf for that room, but they still count the whole floor as a Building Occupancy, no mixed occupancy!  Is this right, the 2009 IBC code TABLE 508.4 says you need to separate an Assembly Occupancy from a Business Occupancy by 1 hour if sprinklered.  But, this doesn't make sense when it's the same occupants in both places (all one company).


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## cda (Jun 5, 2014)

Welcome

How did you find us??


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## cda (Jun 5, 2014)

el cholo said:
			
		

> So, I've heard of this before.  A tenant build-out space for one company has a large conference room (over 750 sf), the occupant load is counted as 1/15sf for that room, but they still count the whole floor as a Building Occupancy, no mixed occupancy!  Is this right, the 2009 IBC code TABLE 508.4 says you need to separate an Assembly Occupancy from a Business Occupancy by 1 hour if sprinklered.  But, this doesn't make sense when it's the same occupants in both places (all one company).


Sometimes it can be an "accessory use"

508.2 Accessory occupancies. Accessory occupancies are those occupancies that are ancillary to the main occupancy of the building or portion thereof. Accessory occupancies shall comply with the provisions of Sections 508.2.1 through 508.2.5.3.

Buildings often have rooms or spaces with an occupancy that is different from, but accessory to, the principal occupancy of the building. When such accessory areas are limited in size, they will not ordinarily represent a significantly different life safety hazard. This principle does not apply, however, to the incidental accessory occupancy areas indicated in Section 508.2.5 or where otherwise indicated in Sections 508.2.4 and 508.3.3 for areas classified as Group H.

The occupancy must be ancillary to the principal purpose for which the structure is occupied. This means that the purpose and function of the area is subordinate and secondary to the structure's primary function. As such, the activities that occur in accessory use areas are necessary for the principal occupancy to properly function and would not otherwise reasonably exist apart from the principal occupancy.


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## Yikes (Jun 7, 2014)

When you exclude "closets", do they have to be full-height?  If I have 34" high built-in storage cabinets with a countertop (in a classroom, for example), can I exclude the SF of these cabinets?


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## steveray (Jun 7, 2014)

Yikes said:
			
		

> When you exclude "closets", do they have to be full-height?  If I have 34" high built-in storage cabinets with a countertop (in a classroom, for example), can I exclude the SF of these cabinets?


If it is not "gross" you can exclude anywhere you can't fit a person.....IMHO


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