Penthouses or rooftop structures shall be subject to the regulations of Subtitle C, Chapter 15, and to the height and story limitations specified in each zone of this subtitle; provided that public schools shall be permitted a mechanical penthouses to a maximum height of eighteen feet, six inches (18 ft., 6 in.) or the permitted mechanical penthouse height in the zone, whichever is greater.
D.C. Mun. Regs. tit. 11, r. 11-D4905