Gross occupant load calculations and section 107.2.3

[Tim Mailloux]

In most of the project work my office does we are doing gross occupant load calculations for large swaths of the building and net area calculations for space here and there (conference rooms, assembly type spaces, etc...) as needed. However IBC section 107.2.3 states that the drawings ”shall designate the number of occupants on all floors and in all rooms or spaces”.

The way I read that, is even though we are doing gross occupant load calculation on a project, we also need to show individual occupant loads in every room. I have no issue doing this but I’m worried that it will cause confusion. The gross calculation will never match the sum of all the individual spaces if someone takes the time to add them up. What is everyone’s thoughts on this?

What I have been doing is showing individual room or space occupant loads in certain rooms that have close to or over 50 occuants, say in a large open office area, to help the BO reviewing the drawings know if we have enough exits for that space and if the doors are opening in the direction of egress travel.

 

[cda]

I agree with your method most of the time.

Sometimes will ask to get specific, when it looks like it matters.

Do you do a life safety plan?? travel distance, cpot, all that other good stuff??


Happy BO, Happy Plans

 

[Tim Mailloux]

I only waste me time with all that other stuff when SteveRay or his dad are the AHJ.

 

[Tim Mailloux]

Yes, in addition to occupant loads we show travel distances, CPET, separation of exits, fire ratings of walls, fire extinguisher locations and travel distance, stair egress loads, door egress loads, detailed plumbing fixture calculations and a detailed code summary.

 

[mtlogcabin]

Do every room and then add them up and that is the OL for the floor. Some rooms will be gross and some will be net. Do not round the numbers up for each room only round the total up for each the floor

 

[TheCommish]

I would expect a number for classrooms, shop areas, large office areas, with the egress path shown on the life safety plan, then the total projected through each egress path and exit access, then the capacity of the most restrictive egress component shown.

the easier you make it on the plan review, the fast the permit moves through the process.

 

[Tim Mailloux]

Do every room and then add them up and that is the OL for the floor. Some rooms will be gross and some will be net.

that kind of goes against the point of doing a gross calculation.

 

[Tim Mailloux]

I would expect a number for classrooms, shop areas, large office areas, with the egress path shown on the life safety plan, then the total projected through each egress path and exit access, then the capacity of the most restrictive egress component shown.
the easier you make it on the plan review, the fast the permit moves through the process.

We pretty much do all of that. Did you ever get a chance to review our code plans for that project in your town?

 

[mtlogcabin]

No where does 107.2.3 instruct you to use the gross calculation for large swaths of a building.


[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.

 

[Tim Mailloux]

Based on the definition of floor area gross, how to you accurately capture all of the areas included in the definition if you are doing room by room calculations? How do you capture small chases and shafts, thickness of interior walls, etc.? You do this by doing a calculation for a large swath of area that includes many rooms and or spaces that all fall under the same function or space. Not by going room by room.



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.

 

[steveray]

You know how I feel...I have no problem using the gross number "overall" just so long as we can verify egress works for the close areas....Just like you said...

I don't care if the egress numbers and overall numbers don't match....

 

[cda]

Tim,,,,

Slowly we will make them all think like we do!!!

Just takes a little indoctrination.

 

[mtlogcabin]

Tim
After re-reading 107.2.3 again it is used for determining the means of egress path is sized correctly based on the number of occupants in each room or space. So you are correct there will always be a difference between the numbers using 107.2.3 and the designed occupant load using 1004

Remember the design OL can have numbers higher or lower than 1004 uses. 107.2.3 would be used based on the actual OL of each room

1004.8 Concentrated business use areas.
The occupant load factor for concentrated business use shall be applied to telephone call centers, trading floors, electronic data processing centers and similar business use areas with a higher density of occupants than would normally be expected in a typical business occupancy environment. Where approved by the building official, the occupant load for concentrated business use areas shall be the actual occupant load, but not less than one occupant per 50 square feet (4.65 m2) of gross occupiable floor space.

 

[steveray]

Yep...1004 is the "overall" and 107.2.3 is the nuts and bolts of the spaces...

 

[Tim Mailloux]

Yep...1004 is the "overall" and 107.2.3 is the nuts and bolts of the spaces...

so the overall floor calculation may be 500 people, but the room by room tabulation may be 20 or 30 people lower. Thats not an issue for anyone? The means of egress needs to be sized for the overall load.

 

[steveray]

I might use the overall and make sure that 1006.3.1 exits per story works...But when it comes to doors and remoteness and stuff I'm going to use the room by room approach...30X.2 is 6 inches of egress somewhere spread out across a story....If there are only 2 exits, that is 3" each, if it gets that close in new construction then maybe it was designed too tight...

 

[RLGA]

Here is my methodology and I have not had any push-back from plans examiners:

Every occupiable room must have a door that is at least 32 inches clear. Since most of my projects provide 36-inch-wide doors, I use a clear width of 33 inches. Depending on the sprinklered condition of the building and the presence of an emergency voice/alarm communication system, I use either 0.2 inches or 1.5 inches per occupant. For the purposes of example, let us use 0.2 inches per occupant.

At 33 inches, the occupant load capacity of a single door is 165. So if a space has one door, then it is assumed the occupant load is 165 or less (there is no need to state that a small office has two occupants unless your plans examiner is really that stupid, IMHO).

So I state in my egress portion of the code data that all spaces with an occupant load of 165 or less have an egress capacity of 33 inches except as indicated below. Below that, I list each space that is required to have two or more means of egress per Table 1006.2.1. I identify the space, the occupant load, the required egress width capacity, the provided egress width capacity, and the separation distance.

Then, for the story, I list the total occupant load, the required egress width capacity, the provided egress width capacity, and the separation distance. The total occupant load is the sum of all occupant loads based on gross floor area and the individual occupant loads for each space based on net areas.

I have had no known problems using this method.

 

[cda]

Here is my methodology and I have not had any push-back from plans examiners:

Every occupiable room must have a door that is at least 32 inches clear. Since most of my projects provide 36-inch-wide doors, I use a clear width of 33 inches. Depending on the sprinklered condition of the building and the presence of an emergency voice/alarm communication system, I use either 0.2 inches or 1.5 inches per occupant. For the purposes of example, let us use 0.2 inches per occupant.

At 33 inches, the occupant load capacity of a single door is 165. So if a space has one door, then it is assumed the occupant load is 165 or less (there is no need to state that a small office has two occupants unless your plans examiner is really that stupid, IMHO).

So I state in my egress portion of the code data that all spaces with an occupant load of 165 or less have an egress capacity of 33 inches except as indicated below. Below that, I list each space that is required to have two or more means of egress per Table 1006.2.1. I identify the space, the occupant load, the required egress width capacity, the provided egress width capacity, and the separation distance.

Then, for the story, I list the total occupant load, the required egress width capacity, the provided egress width capacity, and the separation distance. The total occupant load is the sum of all occupant loads based on gross floor area and the individual occupant loads for each space based on net areas.

I have had no known problems using this method.

Interesting

Nice approach

 

[Tim Mailloux]

Here is my methodology and I have not had any push-back from plans examiners:

Every occupiable room must have a door that is at least 32 inches clear. Since most of my projects provide 36-inch-wide doors, I use a clear width of 33 inches. Depending on the sprinklered condition of the building and the presence of an emergency voice/alarm communication system, I use either 0.2 inches or 1.5 inches per occupant. For the purposes of example, let us use 0.2 inches per occupant.

At 33 inches, the occupant load capacity of a single door is 165. So if a space has one door, then it is assumed the occupant load is 165 or less (there is no need to state that a small office has two occupants unless your plans examiner is really that stupid, IMHO).

So I state in my egress portion of the code data that all spaces with an occupant load of 165 or less have an egress capacity of 33 inches except as indicated below. Below that, I list each space that is required to have two or more means of egress per Table 1006.2.1. I identify the space, the occupant load, the required egress width capacity, the provided egress width capacity, and the separation distance.

Then, for the story, I list the total occupant load, the required egress width capacity, the provided egress width capacity, and the separation distance. The total occupant load is the sum of all occupant loads based on gross floor area and the individual occupant loads for each space based on net areas.

I have had no known problems using this method.

this is similar to how I am currently doing things. I do have a couple of questions:

165 occupants is well above the threshold for having more than one exit from a room or space. The highest occupant load to allows only one exit is 49 people and only gets lower from there depending on occupancy. so why do you use 165 as your start point?

I think the intent of 107.2.3 is to make sure entire means of egress system works. We have gotten into the habit of saving this floor has 400 ocupants and the (2) stairs have a capacity of 450 people but we dont show how all those people get to the stairs and if there are any pinch points along the way to the exits.

 

[RLGA]

this is similar to how I am currently doing things. I do have a couple of questions:

165 occupants is well above the threshold for having more than one exit from a room or space. The highest occupant load to allows only one exit is 49 people and only gets lower from there depending on occupancy. so why do you use 165 as your start point?

I think the intent of 107.2.3 is to make sure entire means of egress system works. We have gotten into the habit of saving this floor has 400 ocupants and the (2) stairs have a capacity of 450 people but we dont show how all those people get to the stairs and if there are any pinch points along the way to the exits.

165 is the capacity of a single door with a 33-inch clear width; thus, it can be assumed that every room not listed below has an occupant load under that capacity and is not required to have two or more means of egress. Right below that I list those areas where two means of egress are required per Table 1006.2.1. If the area is a Group A occupancy and the occupant load is 50+, then I state the occupant load, the required egress capacity, the provided egress capacity, and the minimum separation distance. If the drawings do not show graphically the CPET and travel distances, then I would list those, also.

What I would usually state is some like this (it is usually in a table): "(Area or Story) All areas not listed below: (OL) <165; (Required Capacity) 32 inches; (Provided Capacity) 33 inches; (Separation Distance) N/A"