D.C. Mun. Regs. tit. 11, r. 11-F202
In any of the RA-1 zones, each single household row building shall have at least one thousand eight hundred square feet (1,800 sq. ft.) of gross land area exclusive of any land area in the project used as a basis for determining the floor area ratio of multiple dwelling unit buildings. Each single household row building however, need not have a site of one thousand eight hundred square feet (1,800 sq. ft.) and the difference between the site area and the gross land area may be accumulated into common spaces. Land area used to support this floor area ratio of multiple dwelling unit buildings may also be used for common spaces.
In any of the RA-1 zones, lot area and lot width for residential uses permitted as a special exception shall be as prescribed by the Board of Zoning Adjustment.
D.C. Mun. Regs. tit. 11, r. 11-F202