D.C. Mun. Regs. tit. 25, r. 25-F604
All floors, floor coverings, walls, wall coverings, and ceilings shall be designed, constructed, and installed so they are smooth and easily cleanable, except that antislip floor coverings or applications may be used for safety reasons.
The floors in bathrooms, restrooms, locker rooms, and toilet rooms that are next to showers or toilets, or any other wet areas, shall be constructed of smooth, durable, nonabsorbent, and easily cleanable material.
Every concrete, tile, ceramic, or vinyl floor installed in bathrooms, restrooms, locker rooms, and toilet rooms, which are next to showers or toilets, shall be covered at the junctures between the floor and the walls.
All material used to cover the junctures shall be fitted snugly to the floor and the walls so that they are water tight and there are not openings large enough to permit the entrance of vermin.
The material used in constructing the walls and ceilings must be joined along their edges so as to leave no open spaces or cracks.
Tanning rooms shall be constructed and maintained to provide client privacy.
D.C. Mun. Regs. tit. 25, r. 25-F604