How to Apply for an ADU Permit in NYC — Step by Step DOB NOW Guide

So you have decided to build an ADU on your property. You have checked your eligibility, you have an idea of the type of unit you want, and you are ready to move forward. Now comes the part that trips up most homeowners: the permit process.

Every ADU in New York City must be permitted through the Department of Buildings (DOB). There are no shortcuts, no workarounds, and no "as of right" exceptions that let you skip the filing. The good news is that the process, while bureaucratic, is entirely navigable if you understand the steps before you start.

This guide walks you through every stage of the NYC ADU permit process — from confirming your eligibility to getting your Certificate of Occupancy.

Before You Start: You Cannot File This Yourself

This is the single most important thing to understand before you do anything else: you cannot file an ADU permit application on your own. NYC requires that all building permit applications be submitted by a Registered Design Professional — either a Registered Architect (RA) or a Licensed Professional Engineer (PE).

This is not a suggestion. It is a legal requirement under the NYC Building Code. The DOB NOW system will not even allow a filing without a professional's license number attached to it. Your architect or engineer acts as the "applicant of record" and takes professional responsibility for the design and code compliance of the project.

What this means for you as a homeowner:

• You will need to hire a design professional before you can file anything
• Your architect or engineer handles the actual DOB NOW submission
• You are the "owner" on the application, but the professional signs and seals the drawings
• If you are using a pre-approved ADU plan, you still need the original architect (or a new one) to adapt it to your specific lot

Do not waste time creating a DOB NOW account thinking you can get started on your own. The very first step is finding the right professional.

Step 1: Confirm Your Property Is Eligible

Before you spend money on an architect, confirm that your property actually qualifies for an ADU. Not every lot in NYC is eligible, and the rules are specific.

The core requirements under the city's ADU program:

• Zoning — your property must be in an eligible residential zoning district (most R1 through R5 zones qualify, but there are exceptions)
• Building type — the existing structure must be a one- or two-family home
• Lot size — for detached ADUs, you need sufficient rear yard space after accounting for setbacks and lot coverage limits
• Flood zone — properties in certain FEMA flood zones face additional restrictions, especially for basement conversions
• Landmark status — if your property is in a historic district or is individually landmarked, you will need Landmarks Preservation Commission (LPC) approval in addition to DOB

The fastest way to check eligibility is to use our free eligibility checker, which pulls your property's PLUTO data and zoning information directly from city records. You can also use the city's own "ADU For You" tool, though it provides less detail.

For a comprehensive breakdown of all eligibility criteria, read our complete eligibility guide.

If your property does not qualify, you will find out here — not after paying an architect thousands of dollars. This step takes five minutes and could save you months of frustration.

Step 2: Choose Your ADU Type

The type of ADU you are building determines everything that follows — the filing requirements, the construction scope, the cost, and the timeline. NYC recognizes several ADU configurations:

Basement or Cellar Conversion

• Converts existing below-grade space into a legal dwelling unit
• Must meet minimum ceiling height requirements (7 feet for basements)
• Requires fire sprinkler system in most cases
• Needs window wells or light wells for egress and natural light
• Generally the lowest cost option ($85K–$200K)

Attic Conversion

• Converts existing above-grade space into a legal dwelling unit
• Must meet ceiling height minimums across a percentage of the floor area
• May require structural reinforcement of floor joists
• Needs code-compliant egress (second means of escape)
• Moderate cost range ($100K–$250K)

Detached ADU (Backyard Cottage)

• A new, standalone structure in the rear yard
• Subject to lot coverage limits, rear yard setbacks, and height restrictions
• Maximum size typically governed by remaining FAR (Floor Area Ratio)
• Highest cost but most flexibility in design ($200K–$650K)
• Best candidate for pre-approved plans

Attached Addition

• An extension added to the existing structure
• Must comply with building envelope and zoning setback rules
• Requires structural integration with the existing building
• Moderate to high cost depending on scope ($150K–$400K)

Each type has different filing categories within DOB NOW, different required documents, and different review timelines. Your architect will advise on which type is feasible for your property, but you should have a strong preference going in — it affects who you hire and how much you budget.

Step 3: Hire a Design Professional

This is where your money starts being spent, so choose carefully. You need either a Registered Architect (RA) or a Licensed Professional Engineer (PE) with NYC DOB filing experience.

Not all architects are equal when it comes to ADU work. You want someone who:

• Has filed DOB NOW applications before (not just designed buildings)
• Understands NYC zoning resolution as it applies to ADUs specifically
• Has experience with the ADU type you are pursuing (basement work is very different from detached new construction)
• Can navigate the Professional Certification path if appropriate (more on this below)

If you are using a pre-approved plan: Contact the architect who designed the plan. Pre-approved plans from the city's program were created by specific design firms, and those firms are best positioned to adapt their design to your lot. The adaptation cost is significantly lower than a custom design — typically $2,000 to $5,000 versus $5,000 to $30,000 for fully custom architectural services.

Browse available pre-approved designs on our plans page to see which might work for your property before you start calling architects.

If you are going custom: Expect to pay $5,000 to $30,000 for full architectural services including design, drawings, filing, and construction administration. The range depends on project complexity, ADU size, and how much site-specific engineering is needed.

Need help finding the right professional? Schedule a consultation and we can connect you with architects who specialize in NYC ADU work.

Step 4: Prepare Your Documents

Your architect will prepare the required documentation, but you should understand what goes into the package. Incomplete submissions are the number one cause of delays, so review this list with your design professional before they file.

Required documents for most ADU filings:

• Scope of Work Statement — a written description of exactly what construction is proposed
• Architectural Drawings — floor plans, elevations, sections, and details showing the proposed ADU. Must be drawn to scale and include dimensions
• Structural Calculations — engineering analysis proving the structure can support the proposed loads. Critical for attic conversions and attached additions
• Site Plan — a scaled drawing showing the lot, existing buildings, proposed ADU location, setbacks, lot coverage calculations, and distances to property lines
• Zoning Analysis — a table or narrative demonstrating compliance with all applicable zoning regulations (FAR, lot coverage, open space, height, setbacks)
• Energy Code Compliance — documentation showing the project meets NYC Energy Conservation Code requirements

Additional documents for specific ADU types:

• Sprinkler Plans — required for most basement and cellar conversions. Must be designed by a licensed fire suppression contractor and filed as a separate application
• Plumbing Plans — if adding a new bathroom or kitchen, separate plumbing plans may be required
• Geotechnical Report — sometimes required for detached ADUs depending on soil conditions
• Flood Zone Documentation — if your property is in a FEMA flood zone, additional elevation certificates and flood-proofing details are required
• LPC Approval — if in a historic district, you need Landmarks Preservation Commission sign-off before DOB will accept the filing

Your architect should provide a checklist specific to your project. Do not assume they have everything — ask to review the submission package before it goes to DOB.

Step 5: File on DOB NOW: Build

DOB NOW is the city's online portal for all building permit applications. Your architect handles the actual filing, but here is what happens:

Account Setup

Your architect will file through their own DOB NOW professional account at dobnow.nyc.gov. As the property owner, you may also need a DOB NOW account to electronically sign the owner's authorization. If you do not have one, create it at the same site — you will need your property's BIN (Building Identification Number) or BBL (Borough, Block, Lot) number.

Two Filing Paths

There are two ways an ADU application can be reviewed:

1. Professional Certification (Prof Cert) — Your architect self-certifies that the plans comply with all applicable codes and zoning regulations. DOB accepts the filing without detailed plan review, and you can pull a permit much faster. However, the architect takes on significant professional liability, and DOB conducts random audits. Not all architects are comfortable with this path for ADU work, and not all ADU types are eligible.
2. DOB Plan Examination — The standard path. DOB plan examiners review your drawings for code and zoning compliance. Takes longer but provides an official city review of your plans. This is the more common path for ADU projects, especially custom designs.

Pre-Approved Plan Advantage

If you are using one of the city's pre-approved ADU plans, your filing may qualify for expedited review. Because the base design has already been vetted by DOB, the review focuses primarily on the site-specific adaptations — your lot dimensions, setbacks, utility connections, and any modifications. This can significantly reduce review time.

Once filed, DOB assigns a job number to your application. This is your tracking number for the life of the project. Keep it somewhere accessible — you will reference it constantly.

Step 6: Pay Filing Fees

DOB charges fees at several stages of the permit process. The total typically ranges from $1,000 to $3,000 depending on the scope of work and filing type.

Common fees include:

• Application Filing Fee — charged when the application is submitted. Amount varies by work type
• Plan Examination Fee — charged if your application goes through DOB review (not Professional Certification)
• Permit Issuance Fee — charged when the work permit is actually issued after approval
• Inspection Fees — some inspection types carry additional fees

Fees are paid through DOB NOW using a credit card or electronic check. Your architect can handle this or walk you through the payment portal. These fees are separate from your architect's professional fees and your contractor's construction costs.

For a full picture of ADU costs including permits, design, and construction, see our complete cost breakdown.

Step 7: DOB Review and Approval

This is the waiting stage, and the timeline varies dramatically depending on your filing path and ADU type.

Expected timelines:

• Professional Certification — permit can be issued within days of filing, since there is no DOB plan review
• Pre-Approved Plans (DOB Review) — typically 2 to 8 weeks, since the base design is already vetted
• Custom Plans (DOB Review) — typically 3 to 6 months, depending on complexity and DOB workload

What happens during review:

A DOB plan examiner reviews your drawings against the Building Code, Zoning Resolution, and all applicable regulations. If they find issues, they will issue objections — a written list of problems that must be resolved before the application can be approved.

Common reasons for objections:

• Zoning calculations that do not add up (FAR, lot coverage, setbacks)
• Insufficient egress or means of escape
• Missing or inadequate structural details
• Non-compliant ceiling heights (especially basements and attics)
• Missing sprinkler or fire protection details for basement units
• Conflicts with existing violations on the property
• Incomplete energy code compliance documentation

Your architect responds to objections through DOB NOW, uploading revised drawings and written responses. Each round of objections can add weeks to the timeline. This is why document preparation (Step 4) matters so much — the more complete and accurate your initial submission, the fewer objections you will receive.

Once all objections are resolved, DOB approves the application and issues a work permit. This permit must be posted at the job site before construction begins.

Step 8: Construction

With your permit in hand, construction can begin. But the permit process is not over — DOB remains involved throughout the build.

Hire a Licensed General Contractor

NYC requires that building work be performed by or under the supervision of a Licensed General Contractor (LGC). Verify their license through the DOB license lookup tool. Your contractor should also carry general liability insurance and workers' compensation coverage.

Pull Separate Trade Permits

Your general building permit does not cover all work. The following require separate filings by licensed subcontractors:

• Electrical Permit — filed by a Licensed Master Electrician
• Plumbing Permit — filed by a Licensed Master Plumber
• Sprinkler/Fire Suppression Permit — filed by a licensed fire suppression contractor (if applicable)
• Boiler Permit — if installing a new heating system

Each of these is a separate DOB NOW filing with its own review and approval process. Your general contractor typically coordinates these subcontractors, but confirm that all required trade permits are in place before work begins in those areas.

DOB Inspections During Construction

DOB inspectors will visit the job site at required milestones. Typical inspection points include:

• Foundation inspection (for detached ADUs)
• Framing inspection
• Electrical rough-in inspection
• Plumbing rough-in inspection
• Insulation inspection
• Fire suppression system inspection
• Final inspection

Inspections are requested through DOB NOW. Your contractor schedules them, but as the homeowner you should track their completion. A failed inspection means work stops in that area until the issue is corrected and the inspection is passed.

Step 9: Certificate of Occupancy

The final step in the permit process is obtaining an updated Certificate of Occupancy (CO) that reflects the new ADU on your property.

What this involves:

• All construction work must be complete and all inspections passed
• Your architect files a request for final inspection and CO amendment through DOB NOW
• DOB conducts a final inspection of the completed ADU
• If the ADU passes final inspection, DOB issues an amended CO showing the property now contains an additional dwelling unit

Why the CO matters:

Without an updated Certificate of Occupancy, your ADU is not legally habitable. You cannot legally rent it, and you may face violations and fines if you occupy it without the CO in place. Insurance companies and lenders also require a valid CO.

The CO process typically takes 2 to 6 weeks after the final inspection request, assuming no issues are found. If the final inspector identifies problems, you will need to correct them and schedule a re-inspection before the CO is issued.

Once you have the amended CO in hand, your ADU is a legal dwelling unit. You can rent it, use it for family, or use it however you choose within the terms of the ADU program.

Common Mistakes That Delay Permits

Having walked through the process, here are the mistakes we see most often — and each one can add weeks or months to your timeline:

1. Incomplete drawings — missing details, dimensions, or code compliance annotations. The number one cause of DOB objections
2. Wrong filing type — filing under the wrong work type category in DOB NOW. Your architect should know the correct classification, but mistakes happen
3. Missing sprinkler plans for basement ADUs — fire sprinkler requirements catch homeowners off guard. If your basement ADU requires sprinklers, those plans need to be filed before or concurrent with your main application
4. Zoning errors — incorrect FAR calculations, wrong setback measurements, or failure to account for lot coverage limits. These generate immediate objections
5. Existing violations on the property — open DOB or ECB violations can block your permit application. Check for and resolve violations before you file
6. Not accounting for flood zone requirements — if your property is in a FEMA flood zone, additional documentation is required. Missing this can mean a complete re-filing
7. Filing before LPC approval — if you are in a historic district, DOB will reject your application without Landmarks Preservation Commission sign-off
8. Hiring an architect with no DOB filing experience — residential design experience is not the same as NYC permitting experience. An architect who has never navigated DOB NOW will learn on your dime and your timeline

How to Speed Up the Process

The permit process has built-in timelines you cannot change, but you can minimize delays with these strategies:

Use a Pre-Approved Plan

Pre-approved ADU plans from the city's program have already been reviewed and accepted by DOB. Using one means your application focuses on site-specific adaptation rather than a full design review. This can cut months off the approval timeline. Browse available options on our plans page and read our detailed review of the pre-approved plan library.

Hire an Expediter

A DOB expediter is a professional who specializes in navigating the city's building department. They track your application, respond to examiner questions quickly, and know how to resolve objections efficiently. Good expediters cost $1,500 to $5,000 but can save you months of delays. Many architects have expediters they work with regularly.

Ensure All Documents Are Complete Before Filing

This sounds obvious, but it is the biggest controllable factor in your timeline. Review the full submission package with your architect before they click "submit." Every missing document, every incomplete calculation, every ambiguous detail is a potential objection that adds weeks to your timeline.

Resolve Existing Violations First

Check your property for open DOB and ECB violations before you start the ADU process. Use our property checker to see if there are outstanding issues. Resolving violations before you file prevents a common blocker.

Have Your Contractor Lined Up Early

Do not wait until your permit is approved to start looking for a general contractor. Licensed NYC contractors with ADU experience are in demand. Start vetting contractors during the DOB review period so you can begin construction as soon as the permit is issued.

Coordinate Trade Permits in Advance

Electrical, plumbing, and sprinkler permits are separate filings. Have your subcontractors identified and their permit applications ready to file as soon as the main building permit is approved. Staggering these filings is a common source of construction delays.

The Bottom Line

The NYC ADU permit process is not fast and it is not simple. From your first meeting with an architect to a Certificate of Occupancy in hand, expect 6 to 18 months — with pre-approved plans and an experienced team on the shorter end, and custom designs with complications on the longer end.

But the process is well-defined, and thousands of NYC homeowners will navigate it successfully in the coming years. The key is preparation: confirm eligibility early, hire the right professionals, prepare thorough documentation, and track every milestone.

Ready to start? Check your property's eligibility to see if your home qualifies, then schedule a consultation to discuss next steps with an ADU specialist.