An automatic sprinkler system shall be installed throughout every first basement or cellar story below grade of buildings on which access is not provided directly from the outdoors within each 100 feet (30 480 mm) or fraction thereof of horizontal length of every wall that fronts on a street or frontage space required pursuant to Section 501.3.1.
- One- and two-family dwellings need not provide direct access.
- Any building classified in Occupancy Group R-2 not more than three stories in height and with not more than two dwelling units on any story need not provide direct access when such first basement or cellar story is used for dwelling units or for uses accessory to the residential use in the building.
- Except as provided in Exception 2, above, for Group R-1 and R-2 occupancies, only one direct access from the outdoors to the first basement or cellar story consisting of a stair or door shall be required when such story is used for dwelling units or for uses accessory to the residential use in the building.
Such access shall be by stairs, doors, windows or other means that provide an opening 48 inches (1219 mm) high and 32 inches (813 mm) wide, the sill of which shall not be higher than 36 inches (914 mm) above the inside floor. If an areaway is used to provide below grade access, the minimum horizontal dimension shall be at least one-third the depth of the areaway or 6 feet (1829 mm), whichever is less.