R-2 OPEN STAIR LIMITS

[danc]

I'm working on an apartment building on a sloping site. The walk out level has garages and a vestibule for a single straight run exit stair that serves levels 1, 2, and 3 above the garages. Levels 1, 2, and 3 have four 2 bedroom apartments on each. NFPA and IBC appear to indicate the stair cannot be an open stair and should be enclosed in a 1 hr rated enclosure and exit directly out. The building will be sprinklered. Of course my client would like the stair to be open. Any thoughts on whether any or all of the stair can be open that I might be missing? Part 2- Same building no garages. Treat the stair the same? Thank you

 

[steveray]

Pretty sure you get 125' one way out...Probably want to look at 1019.3 to see what your state does....CT has not jumped on board the exit access stair train....

 

[classicT]

Are you looking at using an Exterior Exit Stairway (Section 1027)?

 

[Paul Sweet]

Is this a single stair, or are there 2 stairs? 2 stairs will be required if the garage is considered a story above grade.

My gut feeling is that the stair(s) would have to be separated from the units by 2 hour construction since they connect 4 levels, but the exterior of the stairs could be left open if they meet IBC 1023.7.

 

[classicT]

Is this a single stair, or are there 2 stairs? 2 stairs will be required if the garage is considered a story above grade.

My gut feeling is that the stair(s) would have to be separated from the units by 2 hour construction since they connect 4 levels, but the exterior of the stairs could be left open if they meet IBC 1023.7.

I tend to agree... but there is a lack of information here that I can't be sure of much yet.

The walk out level has garages and a vestibule for a single straight run exit stair that serves levels 1, 2, and 3 above the garages

From this, I am thinking that the OP is describing the first story as having parking garages and an interior lobby-like area that serves as a vestibule for the interior stairway.

That said, the OP has muddied the water by indicating that...

my client would like the stair to be open.

I am not sure if this means open to the lobby/vestibule or if they mean open to the exterior of the building. My thought is that it is the clients wish to have the lobby/vestibule open to the stairs. Which if that is the case, the following applies:

2021 IBC 1023.2 Construction​

Enclosures for interior exit stairways and ramps shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both. Interior exit stairway and ramp 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 interior exit stairways or ramps shall include any basements, but not any mezzanines. Enclosures for interior exit stairways and ramps shall have a fire-resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours.​

Exceptions:​

1. Interior exit stairways and ramps in Group I-3 occupancies in accordance with the provisions of Section 408.3.8.
2. Interior exit stairways within an atrium enclosed in accordance with Section 404.6.
3. Interior exit stairways in accordance with Section 510.2.

1023.3 Termination​

Interior exit stairways and ramps shall terminate at an exit discharge or a public way.​

Exception: A combination of interior exit stairways, interior exit ramps and exit passageways, constructed in accordance with Sections 1023.2, 1023.3.1 and 1024, respectively, and forming a continuous protected enclosure, shall be permitted to extend an interior exit stairway or ramp to the exit discharge or a public way.​

If they are wanting to be open to the exterior of the building, then I would look to the following:

2021 IBC 1027.6 Exterior Exit Stairway and Ramp Protection​

Exterior exit stairways and ramps shall be separated from the interior of the building as required in Section 1023.2. Openings shall be limited to those necessary for egress from normally occupied spaces. Where a vertical plane projecting from the edge of an exterior exit stairway or ramp and landings is exposed by other parts of the building at an angle of less than 180 degrees (3.14 rad), the exterior wall shall be rated in accordance with Section 1023.7.​

Exceptions:

1. Separation from the interior of the building is not required for occupancies, other than those in Group R-1 or R-2, in buildings that are not more than two stories above grade plane where a level of exit discharge serving such occupancies is the first story above grade plane.
2. Separation from the interior of the building is not required where the exterior exit stairway or ramp is served by an exterior exit ramp or balcony that connects two remote exterior exit stairways or other approved exits with a perimeter that is not less than 50 percent open. To be considered open, the opening shall be not less than 50 percent of the height of the enclosing wall, with the top of the openings not less than 7 feet (2134 mm) above the top of the balcony.
3. Separation from the open-ended corridor of the building is not required for exterior exit stairways or ramps, provided that Items 3.1 through 3.5 are met:
   
   1. The building, including open-ended corridors, and stairways and ramps, shall be equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2.
   2. The open-ended corridors comply with Section 1020.
   3. The open-ended corridors are connected on each end to an exterior exit stairway or ramp complying with Section 1027.
   4. The exterior walls and openings adjacent to the exterior exit stairway or ramp comply with Section 1023.7.
   5. At any location in an open-ended corridor where a change of direction exceeding 45 degrees (0.79 rad) occurs, a clear opening of not less than 35 square feet (3.3 m2) or an exterior stairway or ramp shall be provided. Where clear openings are provided, they shall be located so as to minimize the accumulation of smoke or toxic gases.
4. In Group R-3 occupancies not more than four stories in height, exterior exit stairways and ramps serving individual dwelling units are not required to be separated from the interior of the building where the exterior exit stairway or ramp discharges directly to grade.

 

[Yankee Chronicler]

I'm assuming the desire is for an interior stair that is not enclosed. The IBC allows an open stair to serve as exit access (not as an exit) to traverse not more than one story in height difference, and the exit access travel distance is measured from the most remote point on the upper story to the stair, down the stair (measured along the line of the tread nosings), and from the foot of the stair to the exit door. The IBC commentary for section 1017.1 says:

“Exit access” is defined as “that portion of a means of
egress system that leads from any occupied portion of
a building or structure to an exit” (see the commentary
for the definition in Chapter 2). Exit access includes
rooms, spaces, aisles and corridors that an occupant
would travel along to get to an exit. This can also
include stairways and ramps between levels.

IBC section 1019 is all about exit access stairs. I suggest studying that section carefully -- preferably with the Commentary handy, if you have it.