Stairs - # required? Enclosure required?

[Mech]

IBC 2009

Type IIIB Construction

B, S-1, S-2 mixed occupancy, unseperated, unsprinklered

How many stairs do I need from a 2nd level parts storage area at a car dealership? I'm not sure yet if this will be a mezzanine or a second story. If 2 stairs are required, does one of them need to be enclosed or can they both be unenclosed? The occupant load is less than 10 and the common path of travel will be less than 75 ft from the most remote point of the 2nd level down to the ground floor. You can disregard accessibility requirements for now. That issue will be addressed under a separate thread.

709.2 Exception 16 says I may not need an enclosure.

1016.1 Exception 3 seems to indicate that I need two stairs, one of which can be unenclosed.

1022.1 Exception 1 says the staircase does not need to be enclosed if the occupant load is less than 10 and the design complies with Item 1.1 or 1.2, which it does.

I am thinking that I only need one stairs, which can be unenclosed, from the upper level that I can call a second story.

Below are the code sections that I referenced above.

Thanks in advance.



708.2 Shaft enclosure required. Openings through a floor/ceiling assembly shall be protected by a shaft enclosure complying with this section.

Exceptions:

11. A shaft enclosure shall not be required for floor openings created by unenclosed stairs or ramps in accordance with Exception 3 or 4 in Section 1016.1.

16. Where permitted by other sections of this code.

1016.1 Travel distance limitations. Exits shall be so located on each story such that the maximum length of exit access travel, measured from the most remote point within a story along the natural and unobstructed path of egress travel to an exterior exit door at the level of exit discharge, an entrance to a vertical exit enclosure, an exit passageway, a horizontal exit, an exterior exit stairway or an exterior exit ramp, shall not exceed the distances given in Table 1016.1.

Exceptions:

3. In other than occupancy Groups H and I, the exit access travel distance to a maximum of 50 percent of the exits is permitted to be measured from the most remote point within a building to an exit using unenclosed exit access stairways or ramps when connecting a maximum of two stories. The two connected stories shall be provided with at least two means of egress. Such interconnected stories shall not be open to other stories.

SECTION 1022 EXIT ENCLOSURES

1022.1 Enclosures required. Interior exit stairways and interior exit ramps shall be enclosed with fire barriers constructed in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 712, or both. Exit enclosures shall have a fire-resistance rating of not less than 2 hours where connecting four stories or more and not less than 1 hour where connecting less than four stories. The number of stories connected by the exit enclosure shall include any basements but not any mezzanines. Exit enclosures shall have a fire-resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours. Exit enclosures shall lead directly to the exterior of the building or shall be extended to the exterior of the building with an exit passageway conforming to the requirements of Section 1023, except as permitted in Section 1027.1. An exit enclosure shall not be used for any purpose other than means of egress.

Exceptions:

1. In all occupancies, other than Group H and I occupancies, a stairway is not required to be enclosed when the stairway serves an occupant load of less than 10 and the stairway complies with either Item 1.1 or 1.2. In all cases, the maximum number of connecting open stories shall not exceed two.

1.1. The stairway is open to not more than one story above its level of exit discharge; or

1.2. The stairway is open to not more than one story below its level of exit discharge.

 

[texasbo]

Based on the info given, one, unenclosed stair would probably be OK, but you need to measure travel distance from the most remote point on the 2nd floor/mezz to a legitimate exit, not the ground floor.

 

[Mech]

Forgot to add that part. Travel distance from most remote point on 2nd floor / mezz to first legitimate exit is less than 120 ft.

 

[RLGA]

If a story, see Table 1021.2. A Group S occupancy on a second story may have one exit if the occupant load is 29 or less and the travel distance is no more than 75 feet, but it must be to an exit.

If a mezzanine, one exit is permitted per Table 1015.1 as referenced in the exception to 505.3. The travel distance is either 250 feet or 400 feet depending on the occupancy (you don't indicate which of the Group S occupancies is on the upper level). However, the common path of egress travel is limited to 75 feet; so once down the stairs, if an occupant has a choice of two paths to an exit, then the mezzanine is okay, provided you comply with the other requirements for a mezzanine (i.e. area limitations and openness).

If it qualifies as a mezzanine, then it appears you're okay. If not, then the story-with-one-exit method would not work since the travel distance exceeds the the 75-foot maximum...another stairway would be required. But, both stairways would not have to be enclosed per Exception 1 of 1022.1.

 

[Mech]

RLGA - Let's suppose this a second story. I do not need an enclosed stairway (Exception 1 of 1022.1). Table 1015.1 (Spaces w/ One Exit or Exist Access Doorway) lists Storage Occupancies with a Maximum Occupant Load of 29. "Exit Access Doorway" includes unenclosed exit access stair in its definition. Wouldn't this qualify as a space only requiring one unenclosed stairway since my occupant load is less than 10, I can get from the second story to the first story in less than 75 feet before deciding which exit to procede to, and then it's less than 45 feet to my closest exterior exit door. (Total distance traveled is less than 200 feet.) Seems like this is contradictory to 1021.2???

If I need two stairs, are you saying that neither one needs to be enclosed?

 

[Francis Vineyard]

Don’t have the code book with me and using the information given here;

The exit access travel distance to the exterior exit door (see exit discharge definition) cannot exceed 75 ft. in this dealership. If the stairs cannot be place to meet the 75 ft. distance to the exit discharge then an "exit" component of those listed in 1016.1 (see definition of exit) is needed.

Man just about every other word in 1016.1 has a specialized definition!

 

[texasbo]

Agree with RLGA and Francis; 75' max to exit. Mech, notice the difference between exit access and exit. One exit is ok, but you are limited to 75'. I would try to call it a mezzanine if possible.