Stair roof fire rating?

[Mech]

2015 IBC
3 story building; 2B construction, 0 hr fire resistance rating requirements per Table 601.

The interior exit stairways are located outside the building as shown below.

…...____________
…..|...……….…...|

…..|...…….……...|________
…..|...…….………|...……….|
…..|...…….……...| stairs..|
…..|...….…………|_______|
…..|...….…………|
…..|...….…………|
…..|___________|
​

The wall common to the building and stairway is rated one hour.

Does the roof of the stairway need to be fire rated if it is lower than the main building roof? The stairs roof could be 15 - 20 feet lower than the building roof.

Thanks

 

[RLGA]

No. Roofs of enclosed stairways comply with the requirements for the type of construction

 

[classicT]

Separation from the building, yes; enclosed by rated assembly at roof, no.

As indicated by Ron, roofs for exterior exit stairways do not need to be rated unless required per Table 601 and the given the type of construction.

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.

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. 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.​

 

[RLGA]

Ty J. - The OP doesn't indicate it's an exterior stair. It states "interior exit stairways" which are located in enclosures, thereby are not required to conform to the exterior exit stairway requirements.

However, the exterior walls of an enclosed interior exit stairway are required to comply with Section 1023.7.

 

[classicT]

Ty J. - The OP doesn't indicate it's an exterior stair. It states "interior exit stairways" which are located in enclosures, thereby are not required to conform to the exterior exit stairway requirements.

However, the exterior walls of an enclosed interior exit stairway are required to comply with Section 1023.7.

Agree, that's what he states, but the second half of his post sounds a lot more like an exterior exit stairway.

 

[Mech]

So if I have my understanding correct between stair types, this is an interior exit stair as it is enclosed with 4 walls and a roof.

 

[classicT]

If the stair and three of the four associated walls are on the exterior as suggested by the OP pictogram, then an exterior stair may allow greater benefit as the (3) walls would not need to be rated if appropriate setbacks are allowed. Would no longer require construction as a shaft.

 

[steveray]

Yep...and like Ron said....Watch for this:

1023.7 Interior exit stairway and ramp exterior walls.
Exterior walls of the interior exit stairway or ramp shall comply
with the requirements of Section 705 for exterior walls.
Where nonrated walls or unprotected openings enclose the
exterior of the stairway or ramps and the walls or openings
are exposed by other parts of the building at an angle of less
than 180 degrees (3.14 rad), the building exterior walls
within 10 feet (3048 mm) horizontally of a nonrated wall or
unprotected opening shall have a fire-resistance rating of not
less than 1 hour. Openings within such exterior walls shall be
protected by opening protectives having a fire protection rating
of not less than 3/4 hour. This construction shall extend
vertically from the ground to a point 10 feet (3048 mm)
above the topmost landing of the stairway or ramp, or to the
roof line, whichever is lower.