Penthouses and rooftop structures shall be subject to the regulations of Subtitle C, Chapter 15, and the height and story limitations specified in Subtitle K § 306.2.
The maximum permitted height of a penthouse or rooftop structure shall be twenty feet (20 ft.), and the maximum number stories within the penthouse or rooftop structure shall be one (1) plus a mezzanine, except that a second story for penthouse mechanical space shall be permitted.
D.C. Mun. Regs. tit. 11, r. 11-K306