IDAHO BUILDING CODES – Adds to existing law to establish provisions regarding single stairway building exceptions.

Idaho allows qualifying single-stair apartment buildings

Beginning July 1, 2026, Idaho local governments may approve qualifying Group R-2 apartment buildings with one stairway. This exception overrides conflicting local building codes or other laws, but local approval is not required. Buildings may have up to six stories above ground without a roof people can occupy, or five with one. They may also have one basement, up to four homes per floor, and 6,000 square feet per story. Construction must be Type I, II, III, IV, or V. The entire building must have NFPA 13 sprinklers. The interior stairway and elevator shaft need two-hour fire ratings, and the stairway must be at least 48 inches wide. Stairway openings need 90-minute fire protection and self-closing doors. Hold-open devices are allowed only when connected to the fire alarm system and released when occupant notification starts. Stairway doors must swing into the stairway, except exterior exit doors may swing in the direction of exit travel. Elevators cannot open into the stairway. A corridor with a one-hour fire rating must separate home doors from the stairway door and any related exit passageway. Home doors cannot open directly into the stairway. Travel between home doors and the stairway is limited to 20 feet; total exit-access travel is limited to 125 feet. Exits cannot pass through another use, including a parking garage. Exit courts cannot be deeper than their width unless people can reach a public way in either direction. Certain outside wall openings within 10 feet of the exit door, or into the stairway, need 45-minute fire protection. Every floor served by the single exit needs code-compliant emergency escape and rescue openings. Electrical outlets are barred from the stairway; shared corridor and lobby outlets need lockable covers accessible to maintenance staff. The building needs automatic smoke and fire detection that triggers occupant notification. Required alarms and smoke detection must also cover specified shared spaces, laundry, mechanical and storage rooms, corridors, stairways, and exit passageways. A sign beside the fire alarm control panel must state: “THIS BUILDING CONTAINS ONLY ONE STAIR.” Each lot may have at most two single-exit buildings or two single-exit areas within one building. Two buildings sharing a lot cannot use exception 1 of International Building Code section 705.3. All other local building-code rules still apply. The law does not guarantee lower housing costs or more housing.