D.C. Mun. Regs. tit. 25-B, § 1806
1806.1 Wall and ceiling covering materials shall be attached so that they are easily cleanable.
1806.2 Except in areas used only for dry storage, concrete, porous blocks, or bricks used for indoor wall construction shall be finished and sealed to provide a smooth, nonabsorbent, easily cleanable surface.
SOURCE: Final Rulemaking published at 56 DCR 5245 (July 3, 2009).