For all non-complying buildings or other structures utilizing any of the provisions of this Section, the amount of pre-existing non-compliances shall be based either on the construction documents of such building or other structure previously approved by the Department of Buildings at the time of construction, enlargement, or subsequent alteration of such building or other structure, as applicable, or, where an approved set of construction documents does not exist for such building or other structure, an as-built drawing set completed by a professional engineer or architect. The Department of Buildings may request additional information to substantiate proof of non-compliances. Verification by the Department of Buildings of such documentation shall be a pre-condition prior to any demolition for reconstruction work, or alteration permit issued by the Department of Buildings for a zoning lot altering or reconstructing non-compliances pursuant to the provisions of this Section.