D.C. Mun. Regs. tit. 11-K, § 232
232.1 The maximum permitted lot occupancy in the SEFC-4 zone shall be twenty-five percent (25%), except as provided in Subtitle K § 232.3.
232.2 Lot occupancy shall be the total area occupied by all buildings and structures located on land and by any associated permanent structure located on, in, or over water, other than a floating home, divided by the total area of the lot.
232.3 The lot occupancy on a lot used exclusively for a recreational use, marina, yacht club, or boathouse buildings and structures shall not exceed fifty percent (50%).
SOURCE: Final Rulemaking published at 63 DCR 2447, 3176 (March 4, 2016 – Part 2).