A rear yard shall be provided for each structure located in an Industrial District.
Except as provided in § 842.5, the rear yard need not be provided below a horizontal plane twenty feet (20 ft.) above the mean finished grade at the middle of the rear of the structure.
For that portion of the structure above the horizontal plane, the depth of rear yard may be measured as follows:
The minimum depth of the rear yard shall be two and one-half inches per foot (2.5 in./ft.) of vertical distance from the mean finished grade at the middle of the rear of the structure to the highest point of the main roof or parapet wall, but not less than twelve feet (12 ft.).
Where the rear lot line of a lot abuts a Residence District or is separated only by an alley from a Residence District, the waiver in § 842.2 shall not apply and a rear yard shall be provided from the ground up.
In the case of a through lot or a corner lot abutting three (3) or more streets, the depth of rear yard may be measured from the center line of the street abutting the lot at the rear of the structure.
D.C. Mun. Regs. tit. 11, r. 11-842