D.C. Mun. Regs. tit. 11, r. 11-633
An area equivalent to ten percent (10%) of the total lot area shall be provided for all new development.
The area for new development shall be located immediately adjacent to the main entrance to the principal building or structure on the lot, and shall serve as a transitional space between the street or pedestrian right-of-way and the building or structure.
The area for new development shall be open to the sky or have a minimum vertical clearance of one (1) story or ten feet (10 ft.).
The area shall be suitably lighted and landscaped for public use, and may be utilized for temporary commercial displays.
The space shall be open and available to the general public on a continuous basis.
The area shall not be charged against the gross floor area of the building.
D.C. Mun. Regs. tit. 11, r. 11-633