D.C. Mun. Regs. tit. 14, r. 14-406
No habitable room shall be divided in any manner into space intended for living, sleeping, eating, or cooking purposes by an installed partition or divider of any type above four feet (4 ft.) in height, unless each such subdivided part complies with the requirements for a habitable room, except as otherwise provided in this section.
The enclosure of cabinet-type kitchenettes by doors or other closing devices, where those kitchenettes are too small to be occupied when the doors or other closing devices are closed in a normal manner, and where those kitchenettes are continuously mechanically ventilated, at least when closed, shall not be deemed to subdivide the room.
If any separation of a habitable room leaves a clear unobstructed opening between the parts of that habitable room at least equal to eighty percent (80%) of the cross sectional area of that part of the room receiving its light through any other part, that separation shall not be in violation of this section.
D.C. Mun. Regs. tit. 14, r. 14-406