D.C. Mun. Regs. tit. 11, r. 11-401
Except as provided in chapters 20 through 25 of this title and in the second sentence of this subsection, in the case of a building located, on May 12, 1958, on a lot with a lot area or width of lot, or both, less than that prescribed in § 401.3 for the district in which it is located, the building may not be enlarged or replaced by a new building unless it complies with all other provisions of this title. Notwithstanding the above, the lot area requirements of § 401.3 must be met when the building is being converted to a use or replaced by a building intended to house a use that would require more lot area or lot width than is on the building's lot.
Except as provided in § 401.3, in the case of an unimproved lot in single ownership on November 1, 1957, that has a lot area or width of lot less than that specified in § 401.3 for the district in which it is located and that does not adjoin another unimproved lot in the same ownership, a structure may be erected on the lot if both the lot area and width of lot are at least eighty percent (80%) of the lot area and width of lot specified under § 401.3; provided, that the structure shall comply with all other provisions of this title.
Except as prescribed in the other provisions of this chapter, the minimum dimensions of a lot in a Residence District shall be as set forth in the following table:
ZONE DISTRICT AND STRUCTURE | MINIMUM LOT AREA (square feet) | MINIMUM WIDTH OF LOT (feet) |
R-1-A Public School R-1-A All other structures R-1-B Public School R-1-B All other structures R-2 Public School R-2 One-family semi-detached dwelling R-2 All other structures R-3 Public School R-3 Row dwelling R-3 One-family semi-detached dwelling R-3 All other structures R-4 Public School R-4 Row dwelling and flat R-4 One-family semi-detached dwelling R-4 Conversion of a building or structure pursuant to §§ 330.7 or 336 to an apartment house R-4 All other structures R-5-A Public School R-5-A All other structures R-5-B Public School R-5-C, R-5-D,R-5-E Public School R-5-B, R-5-C, R-5-D,R-5-E All other structures | 15,000 7,500 15,000 5,000 9,000 3,000 4,000 9,000 2,000 3,000 4,000 9,000 1,800 3,000 900 sq. ft./apartment or bachelor apartment 4,000 9,000 As prescribed by the Board pursuant to § 3104 9,000 None prescribed None prescribe | 120 75 120 50 120 30 40 120 20 30 40 120 18 30 None prescribed 40 80 As prescribed by the Board pursuant to § 3104 80 80 None prescribed |
In the case of an unimproved plot of ground in single ownership on November 1, 1957, that has a lot area or width of lot less than two hundred percent (200%) of that prescribed in § 401.3 or the district in which it is located and that does not adjoin another unimproved plot of ground in the same ownership, two structures may be erected on the lot; provided, that each structure shall be erected on a lot that complies with eighty percent (80%) of both the required lot area and width of lot specified in § 401.3; and provided further, that each structure shall comply with all other provisions of this title.
In R-5-A Districts, each row dwelling shall have at least eighteen hundred square feet (1,800 ft.2) of gross land area exclusive of any land area in the project used as a basis for determining the floor area ratio of multi-family buildings. Each row dwelling, however, need not have a site of eighteen hundred square feet (1,800 ft.2), and the difference between the site area and the gross land area may be accumulated into common spaces. Land areas used to support this floor area ratio of multi-family buildings may also be used for common spaces.
Each lot created after February 15, 1966, to be used and occupied by a one-family detached dwelling, one-family semi-detached dwelling, community-house, or row dwelling, shall have a street frontage measured along the street a distance equal to at least forty percent (40%) of the required minimum width of lot and no case less than fourteen feet (14 ft.).
Each lot created after February 15, 1966, to be used and occupied by an apartment house shall have a street frontage measured along the street a distance of not less than thirty feet (30 ft.).
For public schools, minimum lot area may include adjacent parcels under the same ownership that are separated only by a public alley.
For public schools on a corner lot or through lot, minimum lot width may include the measurement of all street frontages.
For public schools on split-zoned lots, the minimum lot width and minimum lot area requirements if any, of the less restrictive zone shall apply to the entire lot as long as the lot was in existence as of February 13, 2006.
An apartment house in an R-4 Zone District, whether converted from a building or structure pursuant to former § 330.5(e) or existing §§ 330.7 or 336, or existing before May 12, 1958, may not be renovated or expanded so as to increase the number of dwelling units unless there are nine hundred square feet (900 sq. ft.) of lot area for each dwelling unit, both existing and new.
D.C. Mun. Regs. tit. 11, r. 11-401