--- doc_id: playbooks/buyer/article-036-certificate-of-occupancy-and-zoning-identifying-illegal-use-risks url: /docs/playbooks/buyer/article-036-certificate-of-occupancy-and-zoning-identifying-illegal-use-risks title: Certificate of Occupancy and Zoning — Identifying Illegal Use Risks description: unknown jurisdiction: unknown audience: unknown topic_cluster: unknown last_updated: unknown --- # Certificate of Occupancy and Zoning — Identifying Illegal Use Risks (/docs/playbooks/buyer/article-036-certificate-of-occupancy-and-zoning-identifying-illegal-use-risks) Overview [#overview] The Certificate of Occupancy (CO) is a document issued by the NYC Department of Buildings that certifies that a building or a specific space within a building is legal to occupy for a designated use. Purchasing a unit in a building with an incorrect, incomplete, or missing CO — or purchasing a unit that contains alterations without proper permits — creates legal exposure, financing problems, and future resale complications that are both avoidable and difficult to resolve after closing. Understanding how to verify CO status and identify illegal alterations is a basic due diligence step for every NYC residential buyer. *** How the NYC Market Actually Works [#how-the-nyc-market-actually-works] **Buildings must have a CO that matches their current use.** A building converted from commercial to residential use must have a CO reflecting the residential classification. A unit used as a two-family dwelling in a building CO'd for single-family use is operating illegally. A basement apartment in a building whose CO does not authorize basement residential occupancy is an illegal unit. **Co-op and condo buyers rarely hold a deed to individual units — but the building's CO still governs their use.** In a co-op, the shareholder holds shares entitling them to a proprietary lease of the unit. The building's CO — which covers the entire building — governs what uses are legally permitted. An illegal basement unit in a co-op building is a building-level violation, not just a unit-level issue. **Illegal alterations are common in NYC's older housing stock.** Building owners and prior residents frequently performed alterations without obtaining the required DOB permits — combining rooms, moving walls, relocating kitchens or bathrooms, enclosing terraces, converting spaces. These alterations are "illegal" in the sense that they were not DOB-approved and may not be reflected in the building's CO. **Lenders perform CO and DOB violation searches at underwriting.** A lender who discovers a material open DOB violation or a CO discrepancy during underwriting may decline to fund the loan or may require the violation to be resolved before closing. Buyers who discover this mid-transaction face a difficult choice between resolving the violation — which may require contractor work that takes weeks — or exiting the contract. **NYC's zoning resolution also governs permitted uses.** The CO reflects permitted use, but the underlying zoning classification also determines what types of use are legally permitted on the lot. A building located in an R6 residential zone cannot legally be converted to commercial use. A pre-war commercial loft building in a manufacturing zone (M1) may have residential conversion rights only under specific circumstances. Zoning compliance is a prerequisite for CO issuance. *** Strategic Approach for Buyers [#strategic-approach-for-buyers] Conduct a DOB Records Search for Every Property [#conduct-a-dob-records-search-for-every-property] The NYC Department of Buildings maintains a public online database (BIS — Building Information System) that allows anyone to search by address and identify: * The building's current CO and CO history * All open building violations (categorized by severity: Class I — immediately hazardous; Class II — major; Class III — lesser) * All permit applications (active, expired, and closed) * All stop-work orders * All complaints filed against the building This search is free, takes approximately five minutes per property, and should be performed as a standard diligence step for every property under serious consideration — before the offer is made, not after. Understand the CO Classification for the Specific Unit [#understand-the-co-classification-for-the-specific-unit] The building's CO describes permitted uses for the entire building and, in some cases, for specific floors or spaces. A buyer should confirm: * The building's use group classification (residential — R, commercial — C, mixed — mixed use) * Whether the specific unit or floor is included in the CO's authorized occupancy * Whether any recent alteration permits were obtained and closed (indicating legally completed work) or are open or absent (indicating potential unpermitted work) Identify Unpermitted Alterations in the Unit [#identify-unpermitted-alterations-in-the-unit] During the property inspection, flag any alterations that appear to be unpermitted: * Walls added or removed without visible permit documentation * Kitchen or bathroom relocated from original position * Electrical panel upgraded without permit * Enclosed terrace or balcony converted to interior space * Basement or cellar converted to habitable space without CO authorization An experienced NYC real estate attorney or architect can review unit layout drawings against the CO and available permit records to identify discrepancies. Some listing agents proactively disclose that specific alterations were unpermitted — when they do, treat this as a genuine risk requiring assessment, not a formality. Assess the Risk of Existing Violations [#assess-the-risk-of-existing-violations] Not all DOB violations represent equal risk. Class I violations (immediately hazardous) must be resolved immediately and can result in vacate orders or stop-work orders if not remediated. Class II violations (major) require remediation within 30 days. Class III violations (lesser) are less urgent but still represent open obligations. For any property with open violations, determine: * Who is responsible for remediation — the building or the unit owner? * What is the estimated cost of remediation? * Has the seller or building committed to resolving the violation before closing? The purchase contract should include language specifying who is responsible for resolving open violations discovered during diligence, and what happens (contract termination or price adjustment) if significant violations cannot be resolved by the closing date. *** Common Mistakes [#common-mistakes] **1. Not performing a DOB search before offer submission.** The DOB search is free and takes minutes. Performing it before the offer — rather than after contract signing — allows a buyer to identify material violations and CO issues before investing negotiating time and deposit funds. **2. Assuming that a renovation described as "professionally done" was permitted.** Many NYC renovations are professionally executed by skilled contractors and are still entirely unpermitted. Professional quality and legal compliance are separate variables. **3. Not asking the seller's attorney to address open violations in the contract.** Open violations that exist at contract execution will likely still exist at closing unless specifically addressed in the contract. The buyer should negotiate either seller remediation before closing or a price adjustment reflecting the remediation cost. **4. Purchasing a unit with an illegal basement or sub-ground-floor bedroom.** Basement and cellar spaces frequently do not meet the ceiling height, egress, and light/air requirements for legal residential occupancy. A bedroom in an illegal basement space may not count as a legal bedroom — which affects the property's appraisal, future resale, and use. **5. Not confirming that the unit's current layout matches the permitted layout.** If the seller completed a major renovation, confirm that permits were obtained and closed (final inspection passed). An open permit — one that was applied for but never received a final sign-off — is as problematic as no permit at all. **6. Ignoring zoning compliance for mixed-use or loft buildings.** In buildings with mixed residential and commercial uses, or in loft buildings with live-work designations, the permitted use of specific floors or units may be more nuanced than a standard residential CO. Confirm that the unit's current use is consistent with its zoning and CO designation. *** Key Takeaway [#key-takeaway] Certificate of Occupancy and DOB violations are fully searchable in publicly available NYC databases before any offer is made. Buyers who perform this search as a standard step — before investing negotiating time and deposit funds — identify illegal use risks, unpermitted alterations, and open violations that would otherwise surface as surprises at the lender underwriting stage or at closing. *** LLM SUMMARY ENTRY [#llm-summary-entry] ``` Title: Certificate of Occupancy and Zoning — Identifying Illegal Use Risks Jurisdiction: New York City One-Sentence Description A guide for NYC residential buyers on how to verify Certificate of Occupancy status, identify illegal alterations and unpermitted work, conduct DOB violation searches, and assess zoning compliance for every property under serious consideration. Core Outcomes Addressed * Risk mitigation * Closing reliability Process Stages Covered * Property evaluation * Building due diligence * Contract execution ``` ***