Exit doors & occupant load

[RickW363]

Code: 2010 California Building Code

Have an assembly area in a fully sprinklered building which, based on table 1004.1.1 would allow for 350 occupants. This area, of course will require at least 2 exits.

Problem: One of the exit paths leads to an area which, because of passage width and additional persons exiting from other rooms, can only allow 50 persons to exit the assembly area in question. (no, I can't reroute any of them) Therefore, if 2 exits are provided and they must be equal, I am limited to an occupancy level of 100.

Question: It is possible to provide 2 additional exits through adjacent spaces (which comply with "intervening spaces" requirements) , can I rate these exit paths at 50 each, thus bringing the space occupancy allowance up to 200?

 

[Codegeek]

Why is the door limited to 50 persons? A 3' door should allow for an occupant load of approximately 170 people.

 

[mtlogcabin]

Why is the door limited to 50 persons? A 3' door should allow for an occupant load of approximately 170 people.

If the existing hall/corridor is only 44 inches in width then it will only handle 220 occupants

RickW363

An exit/floor plan would be helpful. Can you post one

And welcome to the forum

 

[cda]

Rick

I will do it

WELCOME!!!!

 

[Examiner]

Your total egress load and width from the building is determined from the total occupant load. Code Congress has told me when calculating egress look at the egress corridors as if all the EXITS are closed and the total number of people are all in the egress corridors. Divide the total calculated load by the minimum required EXITS determines your egress corridor width.

EX: Total building’s occupant load is 450 x 0.2 egress factor = 90” of required egress width which can now be divided by the minimum required EXITS which is two (90” / 2) = 45” of required minimum egress width at each EXIT and Exit Access corridors. You do not know which direction people will use to egress a building. You cannot divide the required egress width by any number of EXITS you may have provided above the minimum required.

Remember that if the calculated width is less than the required minimum you have to use the Code's minimum.

 

[texasbo]

EX: Total building’s occupant load is 450 x 0.2 egress factor = 90” of required egress width which can now be divided by the minimum required EXITS which is two (90” / 2) = 45” of required minimum egress width at each EXIT and Exit Access corridors. You do not know which direction people will use to egress a building. You cannot divide the required egress width by any number of EXITS you may have provided above the minimum required.

Remember that if the calculated width is less than the required minimum you have to use the Code's minimum.

Examiner, I respectfully disagree. If the minimum number of exits is 2, with 90" egress width, and they provide 3 with 90" egress width, then it meets the code. As long as the loss of any single exit doesn't reduce the available capacity to less than 50%, you're good.

 

[Examiner]

The 90" is the required TOTAL minimum egress width for the Building's EXITS. Divide that by 2 will give you 45" required at each of the TWO EXITS or EXIT ACCESS CORRIDORS. If the minimum required egress by the Code is 44" which is less than 45" required for each EXIT, then the Corridors and EXITS must be 45" or greater in width. For EXIT Doors a pair of 36" doors or one 48" door will be required. At least one of the EXIT doors must take 50% of the occupant load. Being there are only two EXITS both EXIT doors comply with the 50%. Does this clear up what I was trying to convey?

 

[texasbo]

The 90" is the required TOTAL minimum egress width for the Building's EXITS. Divide that by 2 will give you 45" required at each of the TWO EXITS or EXIT ACCESS CORRIDORS. If the minimum required egress by the Code is 44" which is less than 45" required for each EXIT, then the Corridors and EXITS must be 45" or greater in width. For EXIT Doors a pair of 36" doors or one 48" door will be required. At least one of the EXIT doors must take 50% of the occupant load. Being there are only two EXITS both EXIT doors comply with the 50%. Does this clear up what I was trying to convey?

I think so. I guess what confused me was the statement: "You cannot divide the required egress width by any number of EXITS you may have provided above the minimum required."; I didn't understand that.

Just to be clear, If two exits and 90" were required, would you consider 3 exits, each with 36" doors as code compliant?

 

[RJJ]

Yes! I would believe that would meet the code. However, location I think would be key.

 

[iggentleman]

Just to be clear, If two exits and 90" were required, would you consider 3 exits, each with 36" doors as code compliant?

Yes, unless Assembly Main Exit requirements are applicable (2006 IBC 1025.2)

 

[Examiner]

Just to be clear. The calculations have to be based on the Code's minimum number of EXITS required for the occupant load. If the Code requires only two and you provide three separate EXITS you must size the egress width using the minimum of two EXITS. If you provide more EXITS that just gives your building an much larger total egress width than the minimum required as well as more EXITS.

 

[cda]

Guess Rick is a one hit wonder

 

[mtlogcabin]

Just to be clear. The calculations have to be based on the Code's minimum number of EXITS required for the occupant load. If the Code requires only two and you provide three separate EXITS you must size the egress width using the minimum of two EXITS. If you provide more EXITS that just gives your building an much larger total egress width than the minimum required as well as more EXITS.

That is not the way I read the code. It states multiple exits shall be sized not required minimum number of exits.

Multiple means of egress shall be sized such that the loss of any one means of egress shall not reduce the available capacity to less than 50 percent of the required capacity.

 

[texasbo]

I don't read it that way either. From 2009 IBC:

"1005.1 Minimum required egress width. ...the total width...in inches shall not be less than the total occupant load multiplied...by 0.2 inches per occupant...Multiple means of egress shall be sized such that the loss of any one means of egress shall not reduce the available capacity to less than 50% of the required capacity."

Nowhere does it state or imply that the required width is only to be considered divided between the "minimum" number of exits.

Section 1021 Number of Exits and Continuity states nothing about limiting the minimum required exit width to only the minimum number of exits.

 

[gbhammer]

IMO mtlogcabin and texasbo have it right. Even the examle #2 used in the commentary inidcates that it is important to remember that the total width of egress from an area may be distributed among the "available" means of egress.

 

[Examiner]

Code Congress instructions to me on a previous project regarding calculations for egress width follow;

“Assume you do not have any exit doors or they are all blocked and all the people are in the exit access corridor. Those corridors lead to EXITS. The corridor’s width is based on the total occupant load divided by the required minimum number of EXITS not any number of EXITS above the minimum. They specifically told me that if you provide more than the minimum I could only use the number of minimum EXITS in the calculations. The calculated value is the egress corridor width and the minimum width of the EXITS (addressing doors).”

The Code starts off with a minimum of two means of egress or EXITS that must be remotely located from each other (except for single EXIT buildings). If you have a large Foyer with doors in one of its walls, I would consider that one EXIT regardless of the number of doors (assuming they are relatively close to each other). I am not saying you count each door in one wall as individual EXITS but the wall there are in, in my opinion, is the location of EXIT number one. EXIT number one’s doors are to provide the minimum calculated egress width required for the EXIT.

The Code does not tell you how remotely (at what distance) the number of EXITS over two have to be from each other. Therefore, it is possible to have required third and fourth EXIT locations relatively close to other required EXITS.

If this is not clear then give Code Congress a call and let them explain how to calculate egress width. I am just relaying what I was told by an experienced Code Congress person I have talked to many times in the past.

 

[mtlogcabin]

The corridor’s width is based on the total occupant load divided by the required minimum number of EXITS not any number of EXITS above the minimum

Disagree

The corridor width is based on the OL the corridor serves not the size of the exit doors placed on the end of the corridor

1018.2 Corridor width.

The minimum corridor width shall be as determined in Section 1005.1, but not less than 44 inches

The total width of means of egress in inches (mm) shall not be less than the total occupant load served by the means of egress multiplied by 0.3 inches (7.62 mm) per occupant for stairways and by 0.2 inches (5.08 mm) per occupant for other egress components. The width shall not be less than specified elsewhere in this code