Code: ALT-1 (Major alteration permit category)
Description: (Alteration Type 1) is a major NYC building alteration that changes the building’s use, egress, or occupancy and requires a new or amended Certificate of Occupancy.
Practical Meaning: For a homeowner, an ALT-1 filing means your project is big enough to change how your building is legally used, how many people can live or work there, or how people exit in an emergency, so you must work with a Registered Architect or Professional Engineer to get DOB plan approval and permits. ALT-1 jobs often have longer review times, more inspections, and stricter paperwork than smaller renovations, so you should plan for extra cost, time, and coordination with your design professional and contractor.
Where You May See It: You may see “ALT-1” on DOB permit applications, plan sets, and approval documents, in DOB NOW and BIS job records, on Letters of Completion and Certificates of Occupancy, and in emails or proposals from your architect or contractor describing the scope of work.
Why It Matters: ALT-1 matters because misclassifying a major project as a smaller alteration can delay approvals, trigger stop-work orders, or force you to refile and redo work to meet current Building Code and zoning rules once DOB reviews the job. It also affects refinancing, resale, and legal use of your building, because banks, buyers, and city inspectors rely on the updated Certificate of Occupancy that is issued at the end of a properly filed ALT-1 job.
Source: DOB Guide to ALT-1 Permits