D.C. Mun. Regs. tit. 11, r. 11-C908
All loading berths or service/delivery spaces that are not enclosed within a building and are located in a zone other than a PDR zone or a PDR zone that abuts an R, RF, or RA zone, shall have screening around the entire perimeter, subject to the standards of Subtitle C §§ 908.3 and 908.4.
Screening is not required if the loading area is in a rear yard and separated from all contiguous property by at least twenty-five feet (25 ft.).
The screening required by Subtitle C § 908.1 shall be a solid masonry wall at least twelve inches (12 in.) thick and seventy-two inches (72 in.) high. The wall shall harmonize with the main structure in architectural character, material, and color.
Gaps in the screening are allowed only to provide driveways and pedestrian exits or entrances that open directly onto a street or alley. No individual gap may exceed twenty feet (20 ft.) in width.
Any lighting used to illuminate a loading berth, loading platform, or service/delivery space shall be arranged so that all direct light rays are confined to the surface of the berth, platform, or space.
D.C. Mun. Regs. tit. 11, r. 11-C908