The maximum permitted building height, not including the penthouse or rooftop structure, in the R-1-A, R-1-B, R-2, and R-3 zones shall not exceed forty feet (40 ft.) and the number of stories shall not exceed three (3) stories.
The maximum permitted height of a penthouse or rooftop structure, except as permitted in Subtitle D § 303.3 and as limited in Subtitle C § 1501, on the roof of a detached dwelling, semi-detached dwelling, rowhouse, or flat shall be twelve feet (12 ft.) and one (1) story.
A non-residential building constructed pursuant to Subtitle D § 207.6 shall be permitted a mechanical penthouse to a maximum height of eighteen feet six inches (18 ft. 6 in.).
D.C. Mun. Regs. tit. 11, r. 11-D303