D.C. Mun. Regs. tit. 11-E, § 4908
4908.1 In the RF zones, a side yard shall not be required. However, except as provided in Subtitle E §§ 4908.2 and 4908.3, if the yard is provided, it shall be not less than five feet (5 ft.) wide.
4908.2 In the case of a lot that abuts or adjoins a public open space, recreation area, or reservation on one (1) or more side lot line, a required side yard may be reduced or omitted.
4908.3 A side yard may be reduced or omitted along a side street abutting a corner lot in an RF zone.
SOURCE: Final Rulemaking published at 67 DCR 3776 (April 3, 2020).