How to calculate occupancy load in a corridor?

[ElArch]

Please see the floor plan: First floor plan

I have a 4 story type VA building. There are 500 OCC in the courtyard. The total occupancy load on the first floor is 824. How to calculate the corridor occupancy load in front of the community room?

Thanks a lot.

 

[Yankee Chronicler]

You don't. Corridors are considered "not normally occupied" spaces.

I understand that for residential occupancies Table 1004.5 says to calculate the occupant load based on 1 person per 200 gross square feet, which would include corridors. That also includes closets and bathrooms, but those are also not considered to be normally occupied.



Why do you need to assign an occupant load to a small portion of the corridor?

 

[ElArch]

You don't. Corridors are considered "not normally occupied" spaces.

I understand that for residential occupancies Table 1004.5 says to calculate the occupant load based on 1 person per 200 gross square feet, which would include corridors. That also includes closets and bathrooms, but those are also not considered to be normally occupied.

View attachment 16094

Why do you need to assign an occupant load to a small portion of the corridor?

"Why do you need to assign an occupant load to a small portion of the corridor?"

My co-worker moved the community door back and made the corridor in that area much wider.
I want to calculate how much the door can swing into the corridor. Please see below. I need the the occupant load served by corridor to calculate the width.

There are totally 824 OCC. Do I need to use this number to calculate the corridor width for every piece of the corridor?

"Door Encroachment: When doors are fully open, they are generally not permitted to reduce the required corridor width by more than 7 inches (178 mm). Additionally, at any point during its swing, a door should not reduce the required corridor width by more than half."
"The capacity, in inches, of means of egress components other than stairways shall be calculated by multiplying the occupant load served by such component by a means of egress capacity factor of 0.2 inch (5.1 mm) per occupant."

 

[ElArch]

If I use 824 OCC to calculate the corridor width: 824 x 0.15 = 10' !!!

 

[Yankee Chronicler]

So you're not really looking for the occupant load of the corridor, if I understand your question correctly you need to know for how many people the corridor serves as exit access so you can calculate the required width.

Is that what you're looking for?

 

[Yankee Chronicler]

There are totally 824 OCC. Do I need to use this number to calculate the corridor width for every piece of the corridor?

824 is the total occupant load of the first floor? Does that include the occupant load of the courtyard?

I see a heavy line that zig-zags through the building and courtyard, and there are bi-directional pairs of doors at each place this line crosses a corridor. What is this? Is this building split into two buildings by a fire wall, and does this line represent the fire separation line (the imaginary property line discussed in the Commentary)?

If this represents a fire separation line, are the pairs of doors where it crosses the corridors horizontal exits? I see two exit stairs on the right side of the line, but I only see one stair on the left.

Do you have an egress diagram?

 

[walker.t]

There are totally 824 OCC. Do I need to use this number to calculate the corridor width for every piece of the corridor?

No, you don’t use the entire occupant load of the entire floor to calculate the width of every egress component, only the occupant load served by the component:

2021 IBC 1005.3.2 Other Egress Components (emphasis added)
The capacity, in inches, of means of egress components other than stairways shall be calculated by multiplying the occupant load served by such component by a means of egress factor of 0.2” per occupant.

When you have small occupant loads the minimum width by component per 1005.2 may require a greater width then the width based on occupant load. See Table 1020.3 for minimum corridor width by component.

Once you have your minimum width based on component or occupant load, you have to check things such as door swing encroachment, any requirements for accessibility (passing space, door maneuvering clearances,) as well as any specific items related to your building (for example, we will have housekeepers with cleaning carts and we want our corridors to be a little wider than usual.)

 

[ElArch]

So you're not really looking for the occupant load of the corridor, if I understand your question correctly you need to know for how many people the corridor serves as exit access so you can calculate the required width.

Is that what you're looking for?

yes

 

[ElArch]

824 is the total occupant load of the first floor? Does that include the occupant load of the courtyard? Total OCC including courtyard

I see a heavy line that zig-zags through the building and courtyard, and there are bi-directional pairs of doors at each place this line crosses a corridor. What is this? Is this building split into two buildings by a fire wall, and does this line represent the fire separation line (the imaginary property line discussed in the Commentary)? This is imaginary property line separating building to 2 buildings

If this represents a fire separation line, are the pairs of doors where it crosses the corridors horizontal exits? I see two exit stairs on the right side of the line, but I only see one stair on the left. These are not horizontal exits because all space are within the 250' travel distance.

Do you have an egress diagram? No. But I measured it when I was designing the building, everywhere are within the 250' travel distance

 

[ElArch]

No, you don’t use the entire occupant load of the entire floor to calculate the width of every egress component, only the occupant load served by the component:

How to determine the occupant load served by the component?
For example, the corridor at the north side?

When you have small occupant loads the minimum width by component per 1005.2 may require a greater width then the width based on occupant load. See Table 1020.3 for minimum corridor width by component.

Once you have your minimum width based on component or occupant load, you have to check things such as door swing encroachment, any requirements for accessibility (passing space, door maneuvering clearances,) as well as any specific items related to your building (for example, we will have housekeepers with cleaning carts and we want our corridors to be a little wider than usual.)

 

[walker.t]

How to determine the occupant load served by the component?
For example, the corridor at the north side?

The component we’re discussing is the north corridor:
1. Calculate the occupant load of all the rooms that have doors opening into the north corridor.
2. Add the occupant loads from all of those rooms together. Let’s assume that is 200 occupants.
3. Your corridor has two ends, half of the people will go in one direction, the other half in the other direction, therefore divide your total occupant load by 2, so that’s 100 occupants in each direction.
4. Your building is sprinklered, so per 1005.3.2 Exception 1, the egress capacity factor is 0.15”/occupant, that means 100 occupants x 0.15”/occupant = 15” required capacity based on occupant load.
5. Compare the required capacity based on occupant load by the minimum width based on component for corridors in Table 1020.3 and we see you need to use a 44” minimum width for the corridor because the minimum width by component (in Table 1020.3) is greater than the required capacity based on occupant load (calculated in 1005.3.)

Then check the other things I mentioned such as door encroachment to see if you have to provide additional space for anything.

 

[ElArch]

The component we’re discussing is the north corridor:
1. Calculate the occupant load of all the rooms that have doors opening into the north corridor.
2. Add the occupant loads from all of those rooms together. Let’s assume that is 200 occupants.
3. Your corridor has two ends, half of the people will go in one direction, the other half in the other direction, therefore divide your total occupant load by 2, so that’s 100 occupants in each direction.
4. Your building is sprinklered, so per 1005.3.2 Exception 1, the egress capacity factor is 0.15”/occupant, that means 100 occupants x 0.15”/occupant = 15” required capacity based on occupant load.
5. Compare the required capacity based on occupant load by the minimum width based on component for corridors in Table 1020.3 and we see you need to use a 44” minimum width for the corridor because the minimum width by component (in Table 1020.3) is greater than the required capacity based on occupant load (calculated in 1005.3.)

Then check the other things I mentioned such as door encroachment to see if you have to provide additional space for anything.

Thank you very much! You are always so helpful.

 

[Yankee Chronicler]

This is imaginary property line separating building to 2 buildings

Okay, then for starters you don't have one building with an occupant load of 824, you have two buildings, each with an occupant load. All the community spaces are in the left building, but the right side of the courtyard is larger. So maybe the left building has an occupant load of 450 and the right building has an occupant load of 374. (You will have to do the math..)

From there, you need an egress diagram to determine which portions of the corridors serve which spaces and occupant loads.