36 Inch stair exception mezzanine

[TheCommish]

2015 IBC, no applicable local amendments.

Reviewing a major distribution warehouse for permit issuance, very large mezzanine area at least three stairs down to the main floor 36 inched wide. My comment to the designer Stairs x,y,z seem to violate the requirement of 1011.2 44 inch width.


Answer 1011.2 width and capacity. Exception #1 stairway serving an occupant load of less then 50 shall have a width of not less the 36". refer to code analysis sheet, Platforms do not contribute to building or fire area. Only 100 occupants are calculated for the mezzanine perimeter has multiple stairs. There would be less than 50 at each stair.

505.2 Mezzanines. A mezzanine or mezzanines in compliance with Section 505.2 shall be considered a portion of the story below. Such mezzanines shall not contribute to either the building area or number of stories as regulated by Section 503.1. The area of the mezzanine shall be included in determining the fire area. The clear height above and below the mezzanine floor construction shall be not less than 7 feet...

505.2.2 Means of egress. The means of egress for mezzanines shall comply with the applicable provisions of Chapter 10.

1006.1 General. The number of exits or exit access doorways required within the means of egress system shall comply with the provisions of Section 1006.2 for spaces, including mezzanines, and Section 1006.3 for stories.

1006.2 Egress from spaces. Rooms, areas or spaces, including mezzanines, within a story or basement shall be provided with the number of exits or access to exits in accordance with this section.

I agree that the mezzanine does not count to the build area or building height, this has nothing to do with occupant load.
Definition chapter 2 OCCUPANT LOAD. The number of persons for which the means of egress of a building or portion thereof is designed.

Concern/question for the group is the designer allowed to use multiple stairs in the scenario to divide the load (like exit doors) or is the occupant load of 100 counted to a single stair and a second exit off the mezzanine needed?


Thanks

 

[RLGA]

The exception states stairways (plural) serving an occupant load of less than 50--not each stairway serving an occupant load of less than 50.

Additionally, the Commentary clearly states the following:

"The use of this exception is limited to buildings where the entire occupant load of each upper story and/or basement is less than 50."​

I know that the Commentary uses "story" and "basement," but the code does not, so it is really applicable to the use of stairways for any situation.

 

[TheCommish]

Ron,

can you expand on that? I am seeing that the occupant load is 100, more than 50, so each stairway is serving a load of more than 50 which equals 44 in stair.

BTY I have your book, can find it, it is a good reference

 

[bill1952]

"at least 3 stairs" so less than 34 each.

 

[bill1952]

I know that the Commentary uses "story" and "basement," but the code does not, so it is really applicable to the use of stairways for any situation.

I'm beginning to think commentaries should have a review cycle.....

 

[mtlogcabin]

You have an OL of 100 which requires 2 exits which requires 44" wide stairs
Why would you want to build three 36" wide stairs instead of two 44" wide stairs when the 44" stairs would make it easier to carry things up to and down from the mezzanine and use up less space.

And then there is this section
1009.3 Stairways.
In order to be considered part of an accessible means of egress, a stairway between stories shall comply with Sections 1009.3.1 through 1009.3.3.

1009.3.1 Exit acess stairways.
Exit access stairways that connect levels in the same story are not permitted as part of an accessible means of egress.

Exception: Exit access stairways providing means of egress from mezzanines are permitted as part of an accessible means of egress.

1009.3.2 Stairway width.
Stairways shall have a clear width of 48 inches (1219 mm) minimum between handrails.

Exceptions:

1. The clear width of 48 inches (1219 mm) between handrails is not required in buildings equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.1 or 903.3.1.2.

2. The clear width of 48 inches (1219 mm) between handrails is not required for stairways accessed from a refuge area in conjunction with a horizontal exit.

 

[RLGA]

Ron,

can you expand on that? I am seeing that the occupant load is 100, more than 50, so each stairway is serving a load of more than 50 which equals 44 in stair.

BTY I have your book, can find it, it is a good reference

You are correct -- minimum of 44-inch-wide stairways are required since the total occupant load of the mezzanine is greater than 50.

Thank you for purchasing the book and I am glad it helps!

 

[TheCommish]

You have an OL of 100 which requires 2 exits which requires 44" wide stairs
Why would you want to build three 36" wide stairs instead of two 44" wide stairs when the 44" stairs would make it easier to carry things up to and down from the mezzanine and use up less space.

space is not a problem total platform is 325,500 sf and main floor is 634,000 sf, there are 15 plus stairs