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Means of Egress Sizing - explained

T

trevorpan

Member
Joined
Mar 6, 2014
Messages
6
Location
United States
Hi,

When sizing a means of egress, I find 1005.3.2 (IBC 2012).

I am working on a one-story fast food restaurant (Occupancy A-2) we have an occupant load of 93. When I multiply this by .2", I yield 18.6".

How and where is this 18.6" applied? Clearly, the doors are larger and no hallway or pathway would be that size. Please, help take the mystery out of this.

Thank you,

Trevor
 
trevorpan said:
Hi,When sizing a means of egress, I find 1005.3.2 (IBC 2012).

I am working on a one-story fast food restaurant (Occupancy A-2) we have an occupant load of 93. When I multiply this by .2", I yield 18.6".

How and where is this 18.6" applied? Clearly, the doors are larger and no hallway or pathway would be that size. Please, help take the mystery out of this.

Thank you,

Trevor
Click to expand...
36" is greater than 18.6" so you are okay

increase the occupant load and the width increases. if you double the load a 36" door would not work...No mystery

It is only an issue with large occupancies
 
Ok Mark,

Thank you.

So, basically its about discharge capacity? Maybe that's a more apt term in this case?

Always something more to learn and improve on.

Trevor
 
trevorpan said:
Ok Mark,Thank you.

So, basically its about discharge capacity? Maybe that's a more apt term in this case?

Always something more to learn and improve on.

Trevor
Click to expand...
I wouldn't call it "discharge" capacity, since that may be confused with exit discharge. However, it is the capacity that a door, or any exit component, can effectively handle.

Since egress doors are required to have a minimum clear width of 32", any calculated egress width less than that would require at a door that provides the minimum 32" clear width. Using your 93 occupants as an example, per Table 1015.1, if the occupant load exceeds 49, then two exit or exit access doors are required, which really means the minimum exit width has increased to 64", because two 32" doors are now required.

Working the process backwards, a 32" door will have a capacity of 160 occupants (32"/ 0.2" per occupant = 160 occupants). Since two exits are required, the two doors will have a capacity of 320 occupants. This means the owner could potentially add area (increase the number of occupants) without having to add exits, unless there is common path of egress travel that exceeds 75'--but that's for another discussion.
 
mark handler said:
36" is greater than 18.6" so you are okayincrease the occupant load and the width increases. if you double the load a 36" door would not work...No mystery

It is only an issue with large occupancies
Click to expand...
Please note, that a 36" door will only provide a 34" clear opening.
 
being from the old days, so what is the current calculation that a 36" 34 clear opening, number of people can pass through?
 
cda said:
being from the old days, so what is the current calculation that a 36" 34 clear opening, number of people can pass through?
Click to expand...
When a door is open to 90-degrees, the clear width is measured from the face of the door to the stop.

Actually, the clear opening for a 36" door is closer to 33". The stop is typically 5/8", the door is 1-3/4", and the barrel of the hinge adds about another 0.6". Thus, subtracting these from the 36" dimension, you should end up with 33.025"--I'd go with 33".
 
So how many people does that equate to with 33 and today's code?

Use to be 50 per foot if I remember correctly or 150 rounded
 
cda said:
So how many people does that equate to with 33 and today's code?Use to be 50 per foot if I remember correctly or 150 rounded
Click to expand...
Depends on which code edition you're using and if a sprinkler system is installed.

Without a sprinkler system: 0.2" per occupant is the required factor for calculating egress width. So, a 33" clear opening will have a capacity of 165 occupants (33"/0.2" per occupant = 165 occupants).

With a sprinkler system: 0.15" per occupant is the required factor for calculating egress width. So, a 33" clear opening will have a capacity of 220 occupants (33"/0.15" per occupant = 220 occupants).

The 2009 IBC does not allow a reduction in the egress width factor when a building is sprinklered.
 
Last edited by a moderator:
Hi All,

Thank you for the responses, and welcomes.

And Ron, for turning me on to this forum via your website. Can't wait for your Wiley & Sons book to come out.

The job we have has (2) double doors doors, and a back of house service door, so the building far exceeds requirements. The chart was on our cover sheet and I just wanted to know exactly what, and how the egress factor was applied.

Since we're on topic, these factors are applied throughout the means of egress system-as stated in 1005.1? This includes halls, corridors, stairways, etc.? Where I'm a bit ignorant, is these exit way minimums are wider than the doors they serve-and seemingly, the factor which we are talking about.

It seems to me, the door is necessarily a bottle neck. Just trying get into the logic of these parameters. Certainly, I understand the end goal - life safety. But correctly understanding the components and their importance and how it factors in is what I'm after.

Trevor
 
there are different parameters for the means of egress system.

""""The job we have has (2) double doors doors, and a back of house service door"""""

Not sure if your set up meets code???

It appears you are required two exits from the dining area, which I assume seats over 50.

So it that is correct, you need to meet you distance apart for the two exits. And the second one cannot go through a kitchen or storeroom, plus is required to have panic hardware with no other locking device.

are you able to post a simple floor plan?
 
trevorpan said:
Hi CDA,I'm quite sure we are fine, as the building is only 80' long. All appropriate panic hardware is included. My initial post just wanted to clarify, in my own mind, what the code analysis chart on our sheets was referencing.

But please, if you have any comments feel free to share.

Thank you!

Trevor
Click to expand...
If I see correctly there are to separate doors just for the dining area

Appears the building has a fire sprinkler system??

If so do the two doors meet the 1/3 diagonal distance apart????
 
Yes CDA,

There is a fire sprinkler system slated.

The diagonal is 86'-9" from interior corner to interior corner. The distance between closest jambs is 33'-1 1/4", that is more than 28'-11" (1/3 of 86'-9").

So I think we are good ~

Than

Trevor
 
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