D.C. Mun. Regs. tit. 11, r. 11-G606
In the MU-15, MU-16, and MU-22 zones, no side yard is required; however, if a side yard is provided it shall be at least two inches (2 in.) wide for each one foot (1 ft.) of height of building, but no less than five feet (5 ft.).
In the MU-17, MU-18, MU-19, MU-20, and MU-21 zones, no side yard is required for a building or structure other than a detached single dwelling unit or semi-detached single dwelling unit; however, if a side yard is provided it shall be at least two inches (2 in.) wide for each one foot (1 ft.) of height of building but no less than five feet (5 ft.).
A side yard for a detached single dwelling unit or semi-detached single dwelling unit shall be a minimum of eight feet (8 ft.).
Any portion of a building set back from the side lot line shall be considered a side yard and not a court.
D.C. Mun. Regs. tit. 11, r. 11-G606