D.C. Code § 6-906
If the owner of any building or part of building condemned under the provisions of this chapter shall make such changes or repairs as will remedy in a manner satisfactory to the Board for the Condemnation of Insanitary Buildings the conditions which led to the condemnation of such building or part of building, the order of condemnation shall be canceled and the building may again be occupied. If the owner cannot make such changes or repairs within the period within which the owner may lawfully permit such building or part of building to be occupied under § 6-904, but proceeds with such changes or repairs with reasonable diligence during such period, said Board may, by special order, extend from time to time the period within which the occupants of said building or part of building may remain therein, and within which the owner of such building may permit the said occupants so to remain.
D.C. Code § 6-906