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    NYC Building Permits Guide

    A plain-English guide to the NYC DOB permit types — ALT-1, ALT-2, ALT-3, New Building (NB), and Demolition (DM). Covers when each applies, what triggers each type, filing requirements, and typical timelines.

    DOB Permit Types: The Overview

    Nearly all construction and alteration work in NYC requires a permit from the Department of Buildings. The permit type depends on the scope of work — from replacing a boiler to constructing a new tower. The most common permit types are Alteration Type 1 (ALT-1), Alteration Type 2 (ALT-2), Alteration Type 3 (ALT-3), New Building (NB), and Demolition (DM).

    Filing the correct permit type is critical. Filing an ALT-2 when the work actually requires an ALT-1 typically results in plan exam objections, project delays, and — if the wrong classification is discovered mid-project — potential violations. This guide covers the standard permit types and when each applies.

    If you need help selecting and filing the right permit type, see our DOB filings service and permit expediting.

    The Five Main Permit Types

    ALT-1 — Major Alterations

    An ALT-1 is required whenever alterations change the building's use, occupancy, or exits. This is the most complex alteration permit type and typically results in a new or amended Certificate of Occupancy.

    Common ALT-1 scopes:

    • Converting a warehouse to residential lofts
    • Converting one unit into two (or vice versa)
    • Adding a rooftop bar or lounge to a commercial building
    • Enlarging the building's footprint or height
    • Any project that requires a new CO

    ALT-2 — Multiple Work Types

    An ALT-2 covers alterations involving multiple work types (plumbing, mechanical, electrical, etc.) that do not change the use, occupancy, or exits. This is the workhorse permit for interior renovations.

    Common ALT-2 scopes:

    • Interior office fit-out with new HVAC and electrical
    • Combining or reconfiguring apartments within same use group
    • Bathroom or kitchen renovations with plumbing work
    • Retail space build-out inside existing envelope
    • Boiler or elevator replacement with associated work

    ALT-3 — Minor / Single Work Type

    An ALT-3 covers a single work type without changes to use, occupancy, or exits — the simplest alteration permit type. Also known as a "One Work Type" filing.

    Common ALT-3 scopes:

    • Boiler replacement with no other work
    • Standalone plumbing replacement
    • Elevator modernization
    • Façade repairs (sometimes)
    • Curb cut alterations

    NB — New Building

    An NB permit is required for new construction from the ground up. It's the most rigorous permit type and always results in a new Certificate of Occupancy.

    Common NB scopes:

    • Ground-up residential development
    • Ground-up commercial or mixed-use construction
    • Detached accessory structures on existing lots
    • Full replacement of a demolished building

    DM — Demolition

    A DM permit is required for demolition of an entire structure. Partial demolitions (interior gut, façade removal without full structure loss) are usually covered by an ALT-1 or ALT-2 instead.

    Common DM scopes:

    • Full teardown of a residential or commercial building
    • Demolition ahead of new construction (paired with NB filing)
    • Emergency demolition of unsafe structures

    The Permit Filing Process

    Regardless of permit type, DOB filings follow a common workflow:

    • Pre-filing work — Property research, zoning analysis, and architectural or engineering drawings are prepared by a licensed design professional.
    • PW1 submitted through DOB NOW — The Plan/Work application (PW1) is filed electronically. Job filing fee is paid at this stage.
    • Plan examination — DOB reviews the plans for code and zoning compliance. Objections are issued if any items need correction.
    • Objection resolution — The design professional or expediter responds to each objection. This can be a multi-round process.
    • Approval and permit issuance — Once all objections are resolved, DOB approves the plans and issues the actual work permit. Construction can begin.
    • Inspections during work — DOB conducts progress inspections at required milestones (foundation, structural, MEP rough-in, final).
    • Sign-off and closeout — Once work is complete and inspected, the permit is signed off. For ALT-1 and NB filings, this leads to CO issuance.

    Filing the Wrong Permit Type — What Goes Wrong

    Choosing the wrong permit type is a common mistake. Consequences include:

    • Plan exam objections that force reclassification mid-review
    • Project delays of weeks or months while the correct filing is prepared
    • Additional filing fees for the correct permit
    • Loss of professional certification privileges if the misclassification is severe
    • Potential violations if work proceeds under the wrong permit

    Need help selecting and filing the right permit?

    BVS's DOB filings service and permit expediting team handle everything from PW1 preparation through final sign-off. Contact BVS for a free consultation.