D.C. Mun. Regs. tit. 11, r. 11-C203
If a nonconforming structure is destroyed by fire, collapse, explosion, or act of God to an extent of more than seventy-five percent (75%) of the cost of reconstructing the entire structure, the nonconforming structure shall not be restored or reconstructed except in conformity with all provisions of this title, except as provided otherwise in Subtitle C §§ 203.2 through 203.7.
If a casualty or act of God results in damage to an extent of more than seventy-five percent (75%), and if the structure is nonconforming only with respect to percentage of lot occupancy the structure may be reconstructed or restored to its previous condition or to a more conforming condition, even if that condition does not comply with the applicable percentage of lot occupancy.
If a casualty or act of God results in damage to an extent of seventy-five percent (75%) 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 continued diligently 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 seventy-five percent (75%) 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) contractor 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 Subtitle C § 203.4 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 Subtitle C § 203.1, a nonconforming structure that is a historic landmark or certified by the Historic Preservation Office 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 of the structure, subject to the provisions of the Historic Landmark and Historic District Protection Act of 1978.
The twenty-four (24) month period provided in Subtitle C § 203.3 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.
If a nonconforming antenna stops functioning, a temporary replacement antenna may be installed, subject to the following conditions:
D.C. Mun. Regs. tit. 11, r. 11-C203