D.C. Mun. Regs. tit. 11, r. 11-405
In an R-2, R-3, R-4, or R-5 District, a one-family detached dwelling shall be subject to the side yard requirements of an R-1 District.
In an R-3, R-4, or R-5 District, a one-family semi-detached dwelling shall be subject to the side yard requirements of an R-2 District.
In R-2, R-3, R-4, and R-5 Districts, when a one-family dwelling, flat, or multiple dwelling is erected that does not share a common division wall with an existing building or a building being constructed together with the new building, it shall have a side yard on each resulting free-standing side.
Except as provided in § 405.1, in an R-5-A District, one (1) side yard shall be provided for all structures unless the structure is an apartment house containing three (3) or more dwelling units per floor, in which case two (2) side yards shall be provided, each with the minimum width set forth in § 405.9.
A side yard shall not be required along a side street abutting a corner lot in a Residence District.
Except as provided in §§ 405.1 and 405.2, a side yard shall not be required in an R-3, R-4, R-5-B, R-5-C, R-5-D, or R-5-E District. However, if the yard is provided, it shall be at least three inches (3 in.) wide per foot of height of building, but not less than eight feet (8 ft.) wide.
In the case of a lot located in an R-1 or R-2 District proposed to be used by a public school or a public recreation and community center that abuts or adjoins on one (1) or more side lot lines a public open space, recreation area, or reservation, the required side yard may be reduced or omitted.
In the case of a building existing on or before May 12, 1958, with a side yard less than eight feet (8 ft.) wide, an extension or addition may be made to the building; provided, that the width of the existing side yard shall not be decreased; and provided further, that the width of the existing side yard shall be a minimum of five feet (5 ft.).
Side yards shall be provided on lots in Residence Districts as set forth in the following table, subject to the special requirements of other provisions of this chapter:
ZONE DISTRICT | MINIMUM WIDTH OF EACH SIDE YARD |
R-1-A,R-1-B, R-2 R-3, R-4 R-5-A R-5-B, R-5-C, R-5-D, R-5-E | 8 feet None required, except as provided under §§ 405.1, 405.2, and 405.6 3 inches per foot of height of building, but not less than 8 ft. None required, except as provided under §§ 405.1, 405.2, and 405.6. |
In the case of a lot in an R District proposed to be used by a public library that abuts or adjoins along one (1) or both side lot lines a public open space, recreation area, or reservation, the required side yards may be reduced or omitted.
D.C. Mun. Regs. tit. 11, r. 11-405