D.C. Mun. Regs. tit. 11, r. 11-D1105
In the R-1B/GT and R-3/GT zones, notwithstanding Subtitle D § 5000, accessory buildings shall be subject to the development standards of this section.
In the R-1B/GT and R-3/GT zones, except for a shed, an accessory building shall be located facing an alley or private alley to which the owner has access by an easement recorded with the Recorder of Deeds, and shall be set back a maximum of five feet (5 ft.) from the rear property line or a line perpendicular to the façade of the principal building.
In the R-1B/GT zone, an accessory building within five feet (5 ft.) of a public or private vehicular alley may have a maximum height of twenty-two feet (22 ft.), a maximum building area of four hundred and fifty square feet (450 sq. ft.) and a maximum number of two (2) stories.
In the R-3/GT zone, an accessory building within five feet (5 ft.) of a public or private vehicular alley may have a maximum height of twenty-two feet (22 ft.), a maximum building area of four hundred and fifty square feet (450 sq. ft.) and a maximum number of two (2) stories.
In the R-1B/GT and R-3/GT zones, a shed may be permitted in a required rear or side yard provided it is at least five feet (5 ft.) from a public or private vehicular alley.
In the R-1B/GT and R-3/GT zones, roof decks are prohibited.
D.C. Mun. Regs. tit. 11, r. 11-D1105