Alteration application

Alteration applications are the Department of Buildings filings for work on existing buildings, graded by consequence: the major alteration that changes use, egress, or occupancy — and therefore ends in a new or amended certificate of occupancy — and the lesser tiers for renovations that do not. The filing type is the owner's declaration of what the project is, reviewed accordingly.

Analytically, alteration history is the building's change log: what was altered, when, at what claimed scope. Mismatches carry signal — a building whose visible transformation exceeds its filed scope raises legalization questions, and a certificate of occupancy older than a major renovation suggests the paperwork never caught up with the work.