NYC ADU Rules & Permit Guide

City of Yes legalized ADUs on many one- and two-family lots. Learn the 800 sf cap, safety and flood limits, the city’s parking zones, and the exact DOB NOW steps—with official links.

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Step 2 of 4: Regulations

TL;DR: NYC now allows ADUs on many one- and two-family lots, capped at ≤800 sf and subject to strict safety and flood rules. Parking minimums were reformed citywide; many areas have reduced or no minimums. Until DOB/DEP rules finalize, approvals may be contingent—always verify status before filing in DOB NOW. {{verify locally}}

≤ 800 sf cap* Two exits + life-safety* Flood limits apply* Parking reform zones

*Per City of Yes text + DOB proposed/clarifying rules; see official links below. {{verify locally}}

Illustrative backyard ADU concept behind a NYC one- or two-family home
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NYC ADU — at-a-glance

Where allowed
On many one- and two-family lots citywide via City of Yes (with district-specific limits). {{verify locally}}
Maximum size
Up to 800 sq ft of floor area (ZR ADU definition). {{verify locally}}
Safety
Two means of egress and life-safety standards; DOB rules detail requirements. {{verify locally}}
Flood
ADUs barred/limited in high-risk flood areas; use interim flood risk maps + FEMA. {{verify locally}}
Parking
Citywide parking reform zones: many areas have reduced/eliminated minimums; confirm your zone. {{verify locally}}
Process
File online in DOB NOW: Build (NYC.ID + eFiling required). {{verify locally}}

DOB Bulletin 2025-006: ADU approvals are contingent on DEP flood-map rules and DOB rules being in effect. Always check the latest before filing. {{verify locally}}

How to permit an ADU in NYC (5 steps)

  1. Eligibility scan: Confirm one- or two-family status, district, and that ADUs are allowed on your lot. Note the ≤800 sf cap. {{verify locally}}
  2. Flood & safety: Check interim flood risk map + FEMA. Plan two exits, compliant ceiling height, and life-safety per proposed rules.
  3. Accounts & setup: Create DOB NOW: Build + eFiling + NYC.ID. Associate all stakeholders (owner, RA/PE, contractor).
  4. File online: Initiate job in DOB NOW: Build; upload searchable PDFs (plans, DPL1, required forms), pay fees, and respond to objections in-app.
  5. Permits → inspections → sign-off: Pull permits, schedule inspections, and obtain final sign-off/CO as applicable.
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Submittal checklist (quick scan)

  • Site plan + zoning diagram; confirm ≤800 sf ADU and lot compliance
  • Floor plans & elevations; egress diagrams showing two exits
  • Flood compliance exhibits (interim map/FEMA) and any required declarations
  • Structural notes/calcs; energy compliance
  • DOB NOW forms (e.g., DPL1) + stakeholder e-signatures

Tip: Combine drawings into a single, text-searchable PDF. Name files like ADU_NYC_Plans_2025-09-11.pdf.

Size & parking overview (illustrative)

ADU size cap

0 400 sf 700 sf 800 sf cap (ZR)

ZR defines ADUs up to 800 sq ft. Always check current text + DOB rules. {{verify locally}}

Parking reform zones

Zone 1 Often no mins Zone 2 Reduced mins Zone 3 Legacy mins

City of Yes modified parking requirements citywide; verify your location and whether an ADU is exempt. {{verify locally}}

Programs & assistance

HPD “ADU for You” (pre-approved plans)

NYC is building a pre-approved backyard ADU plan library; design pros can submit models now. Homeowner resources will follow as the library launches.

Plus One ADU (state)

NY State’s Plus One program funds owner-occupied ADUs via local partners. NYC’s Plus One program cycles in phases; monitor for re-openings and interest forms.

2-minute ADU permit walkthrough (NYC)

Transcript (abridged): Step 1 — Eligibility scan; Step 2 — Flood & safety pre-check; Step 3 — Set up DOB NOW + eFiling; Step 4 — File & respond; Step 5 — Permits, inspections, sign-off. {{verify locally}}

Local voice prompt

Try speaking to your assistant:

“Hey Siri, ask ADUPlanet — can I build an ADU at my address in New York City?”

Follow-ups: “How big can it be?” “Do flood rules block me?” “Do I need parking?”

Community rating (pilot)

We’ll publish aggregated ratings once we have enough responses.

FAQ — NYC ADUs

Is the program fully active yet?

City of Yes text is in effect, but ADU approvals depend on DOB/DEP rules and flood maps being promulgated. Check DOB Bulletin 2025-006 and the proposed rules page for current status. {{verify locally}}

Can I do a backyard cottage?

Backyard ADUs are contemplated, subject to lot/context rules, safety, and flood limitations. Pre-approved plan library is in development. {{verify locally}}

What about basement conversions?

Basement/cellar units face enhanced safety (two exits) and flood restrictions; some areas remain prohibited. Review proposed rules + flood maps. {{verify locally}}

How do parking rules affect me?

NYC adopted parking reform zones. Many locations have reduced or eliminated minimums; some retain legacy requirements. Confirm your zone before design. {{verify locally}}

Where should I start?

Scan the DCP guide, check DOB Bulletin 2025-006, then line up Costs, Builders, and Financing. File in DOB NOW: Build.