D.C. Mun. Regs. tit. 17, r. 17-3717
Unless the Director of the Department of Consumer and Regulatory Affairs certifies in writing that business other than a salon or shop may be conducted in the space designated as the salon or shop without creating a public health or safety hazard, each salon or shop shall be completely separated by a solid floor-to-ceiling wall or partition, unbroken by any door or window, from any space in which any other business is conducted and from any place designed or intended for human habitation.
The solid wall or partition shall be constructed in accordance with the requirements of the District of Columbia Construction Code and must bear the appropriate preconstruction permits.
A salon or shop may have a door or window opening directly on a public corridor, hallway, passageway, lobby, or to the outside of the building.
Each salon or shop shall have at least one (1) water closet facility (a room with a sink and toilet), which shall be considered adequate if it meets the following requirements:
Water closet walls shall have nonabsorbent surfaces.
Water closet floors shall comply with the requirements of § 110 of Title 22 of the District of Columbia Municipal Regulations (Public Health and Medicine).
Adequate facilities for heating the salon or shop shall be provided in accordance with the requirements of § 110 of Title 22 of the District of Columbia Municipal Regulations (Public Health and Medicine).
All rooms used for the purpose of beauty and barber culture shall be provided with artificial illumination, reasonably uniformly distributed, to give an illumination of an intensity of thirty (30) foot-candles at the working surface of each work stand.
D.C. Mun. Regs. tit. 17, r. 17-3717