Chapter 7, Section 717.4.2- Draftstopping must be provided in attics, mansards, overhangs, or other concealed roof spaces of Group R-2 buildings with three or more dwelling units and in all Group R-1 buildings. The intervening space between any two draftstops or walls must be designed for adequate cross ventilation as described in Section 1203.2. Draftstopping must be installed above, and in line with, tenant and dwelling separation walls that do not extend to the underside of the roof sheathing above.
Chapter 7, Section 717.4.2- Draftstopping in attic spaces of Groups R-1 and R-2 occupancies that do not exceed four stories in height may be installed so that the area between draftstops that extends from the ceiling to the roof does not exceed 3,000 square feet, and the greatest horizontal dimension does not exceed 60 feet. The draftstops do not have to be located directly above or in line with walls separating tenant spaces, unless part of construction required by other provisions of this code. Adequate cross ventilation must be provided in accordance with Section 1203.2.
