D.C. Mun. Regs. tit. 11-K, § 233
233
233.1 A minimum required side yard of twelve feet (12 ft.) shall be provided in the SEFC-4 zone.
233.2 No side yard is required for any building or structure located entirely on, over, or in the water. If a side yard is provided, its minimum width shall be at least five feet (5 ft.).
233.3 Any building or structure located in whole or in part on land shall provide a side yard on each side of twelve feet (12 ft.) minimum.
SOURCE: Final Rulemaking published at 63 DCR 2447, 3176 (March 4, 2016 – Part 2).