A penthouse or rooftop structure on a single household dwelling or flat shall be permitted pursuant to Subtitle C § 1501.
A mechanical penthouse or rooftop structure with a maximum height of eighteen feet, six inches (18 ft. 6 in.) shall be permitted on a non-residential building constructed pursuant to Subtitle D §§ 203.3 through 203.6.
For all other buildings and uses, the maximum permitted height of a penthouse or rooftop structure shall be twelve feet (12 ft.) and one (1) story.
D.C. Mun. Regs. tit. 11, r. 11-D205