Roof extension. Open vent pipes that extend through a roof shall be terminated not less than 12 inches (304.8 mm) above the roof. Where a roof or a portion thereof is to be used for assembly or as a promenade, observation deck, sunbathing deck or similar purposes, open vent pipes within 10 feet (3048 mm) of the walking surface of such roof uses shall terminate not less than 7 feet (2134 mm) above such walking surface.
D.C. Mun. Regs. tit. 12, r. 12-F903