D.C. Mun. Regs. tit. 11, r. 11-K231
The maximum permitted building height, not including the penthouse or rooftop structure, in the SEFC-2 zone shall be forty feet (40 ft.).
A building or structure located on, in or over the water; or a watercraft, including a floating home shall have a height of twenty-five feet (25 ft.) maximum. For the purposes of this subsection, the maximum height shall be measured from the mean high water level along the shore directly in front of the building, structure or watercraft to the highest point of the building or structure, not including sailboat masts.
The maximum permitted height of a penthouse or rooftop structure shall be twelve feet (12 ft.) except that a height of fifteen feet (15 ft.) shall be permitted for penthouse mechanical space; and the maximum number of stories 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-K231