Interpretation #: CEB-2022-06-2014 IBC-1009.9.3

Building or Fire Safety Law Interpreted

675 IAC 13-2.6 2014 Indiana Building Code, Section 1009.9.3 Enclosures under interior stairways. The walls and soffits within enclosed usable spaces under enclosed and unenclosed stairways shall be protected by 1-hour fire-resistance-rated construction or the fire-resistance rating of the stairway enclosure, whichever is greater. Access to the enclosed space shall not be directly from within the stair enclosure.

Issue

Whether Section 1009.9.3 of the 2014 Indiana Building Code (IBC) requires fire-resistance-rated walls and soffits when enclosing usable spaces below interior stairways when those spaces terminate at ceilings below the elevation of the underside of the stair.

Interpretation of the State Building Commissioner

No, Section 1009.9.3 of the 2104 IBC does not require fire-resistance-rated walls and soffits when enclosing usable spaces below interior stairways when those spaces terminate at ceilings below the elevation of the underside of the stair.

Rationale

The regulation requires fire protection of interior stairs when spaces below the stair are usable and enclosed. However, it does not apply to all such spaces. The phrase "enclosed usable spaces under. . .stairways" is intended to apply only to the space immediately beneath stairs that is created and bound by the underside of the stair, the floor and the walls on each side. It does not apply to conditions in which the stair is elevated above a usable space that is enclosed by its own ceiling, and by walls that do not extend to the underside of the stair above. This is reflected in ICC commentary which describes the intent of the section as protection from the fire hazard of miscellaneous storage kept in the space under a stairway, a condition that is different from a typically occupied space with a ceiling plane that occurs below the underside of an elevated stair.