D.C. Mun. Regs. tit. 11, r. 11-2004
If a structure devoted to a nonconforming use is destroyed by fire, collapse, explosion, or act of God to an extent of more than fifty percent (50%) of the cost of reconstructing the entire structure, it shall not be restored or reconstructed except in conformity with all provisions of this title, except as provided otherwise in this section.
If the casualty or act of God results in damage to an extent of fifty percent (50%) or less of the cost of reconstructing the entire structure, the structure may be restored or reconstructed to its previous condition or to a more conforming condition; provided, that the reconstruction or restoration shall be started within twenty-four (24) months of the date of the destruction and diligently continued to completion.
If there is a dispute between the property owner and the Zoning Administrator as to whether the structure has been destroyed to the extent of fifty percent (50%) of reconstruction cost, the costs of restoration and of reconstruction shall be determined by the average of the estimates furnished by three (3) independent qualified contractors. One (1) of the contractors shall be selected by the owner, one (1) by the Zoning Administrator, and one (1) by the first two (2) mentioned contractors.
The estimates required by § 2004.3 shall be prepared and submitted according to a standard procedure and format established by the Zoning Administrator, and the cost of estimates shall be at the expense of the property owner.
Notwithstanding the restrictions of § 2004.1, a structure devoted in whole or in part to a nonconforming use that is also a historic landmark or certified by the State Historic Preservation Officer to be a structure that contributes to the character of the historic district within which it is located may be restored or reconstructed regardless of the extent of destruction, subject to the provisions of the Historic Landmark and Historic District Protection Act of 1978, effective March 3, 1979 (D.C. Law 2-144, as amended; D.C Official Code §§ 6-1101 to 6-1115 (2001) (formerly codified at D.C. Code §§ 5-1001 to 5-1015 (1994 Repl. and 1999 Supp.))), and all other municipal laws and regulations. The nonconforming use may be resumed and continued as before.
The twenty-four (24) month period provided in § 2004.2 may be extended for as long as it takes to apply for and receive any governmental approvals necessary to accomplish the reconstruction or restoration including, but not limited to, approvals from the Board of Zoning Adjustment, the Historic Preservation Review Board, and the Mayor's agent for the Historic Landmark and Historic District Protection Act.
D.C. Mun. Regs. tit. 11, r. 11-2004