In the case of a building devoted to both residential and nonresidential uses, the minimum width and area of a court shall be computed as follows:
No required opening for the admission of light and natural ventilation shall open onto a court niche where the ratio between the width of court niche and the depth of court niche is less than two to one (2:1).
No portion of a court niche shall be farther than three feet (3 ft.) from a point where the court niche is less than three feet (3 ft.) wide.
In the case of an alteration affecting the amount of light and ventilation required by other municipal law or regulation in an existing structure, no legally required window shall be permitted to open onto a court that does not comply with the dimensions in this title.
D.C. Mun. Regs. tit. 11, r. 11-C1801