Rulebook topic
Check what official records say about an existing ADU or secondary suite, how local authorities handle unpermitted work, and what inspections or certificates may still be needed.
An existing accessory dwelling unit (ADU), secondary suite, or other small secondary dwelling needs more than a plausible layout or a long history of use to establish its status. The relevant authority records, approved plans, completed inspections, current use, and later alterations all matter. This category helps you check those pieces and understand what a local correction or regularization route can—and cannot—establish.
Begin with the exact municipal address or parcel and identify every authority that may have approved or inspected the unit. Compare the permit and inspection record with the physical unit: its location, number of dwellings, layout, construction date, services, and current use. A record can be genuine but cover a different scope or an earlier version of the property.
Use the record-check guide for a general process, or the Toronto property-report guide for that city’s municipal report. If you need to establish a program’s historic date, see which construction or use evidence may help; if searches do not find the permit or occupancy file, use the missing-record guide. Seattle has a distinct permit to establish use for an existing ADU. A report, tax entry, property listing, photograph, or owner statement is not by itself proof that the current unit was approved.
For a Toronto garage or ancillary-building conversion, the Toronto garden-suite guide explains why the structure’s permit history affects its treatment under current zoning.
Some authorities provide a route for assessing completed work; others may require a new application, corrections, removal, or a different response. An application is not an approval. Requirements can include plans, opening concealed work, permits for trades, inspections, fees, and corrections to meet the applicable rules. See retrospective approval and regularization, the California state-and-local route guide, and the Atlanta expired-permit guide to distinguish state protections, a prior permit that expired, and work with no permit. Other examples include the Portland guide to unpermitted ADUs and former accessory rental units, the Berkeley certificate-path comparison, the Calgary legalization example, and the England certificate distinction. For New York City, the illegal-conversion correction guide explains the Department of Buildings correction sequence. DOB says its separate Local Law 126 pilot for some existing occupied basement and cellar apartments is not currently accepting applications; check the current NYC ADU program page for status and limits, and see the NYC Local Law 126 pilot guide for the City’s stated scope and the distinction between a temporary authorization and final legal status.
Planning or zoning status, building and fire safety, utility approvals, permission to occupy, rental rules, title restrictions, and lender or insurer requirements may be separate questions. A certificate or inspection record proves only what its issuer, date, approved scope, and stated conditions cover. Start with possible corrective-work checks, then compare the specific documents in completion certificates and legal-status records.
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Existing-Unit Legalization and Compliance
A practical way to compare an existing accessory dwelling unit with the permits, approved plans, inspections, and use records held by the responsible authorities.
Existing-Unit Legalization and Compliance
Learn how authorities may assess an accessory dwelling built without approval, what a retrospective route can require, and why applying does not guarantee legalization.
Existing-Unit Legalization and Compliance
Understand the kinds of checks an authority may make when an existing secondary dwelling is legalized, without assuming a generic code checklist applies to every property.
Existing-Unit Legalization and Compliance
Separate an authority notice and legal-status question from tenancy rights, occupancy approval, sale records, and private lending or insurance decisions.
Existing-Unit Legalization and Compliance
Match an approval or completion record to its issuer, date, property, approved use, inspection scope, and the unit as it exists now.
Existing-Unit Legalization and Compliance
Learn how to match historical records to a local construction, installation, conversion, or occupancy date test without treating age as proof of approval.
Existing-Unit Legalization and Compliance
What Toronto's address-specific Property Information Report can show about permits, inspections, and orders—and what it does not decide about a secondary suite.
Existing-Unit Legalization and Compliance
A Calgary-specific overview of the permit, zoning, inspection, registry, and status checks involved in assessing an existing secondary suite.
Existing-Unit Legalization and Compliance
Follow a records search through the right authority, date range, archive, and access route, then separate an inconclusive search from a missing approval.
Existing-Unit Legalization and Compliance
Understand how an England lawful development certificate differs from building-regulations regularization, and why neither document answers every approval or occupancy question.
Existing-Unit Legalization and Compliance
Separate expired permits from never-permitted work, then check which Atlanta renewal or extension route may apply and what approval remains unfinished.
Existing-Unit Legalization and Compliance
Toronto gives limited zoning relief to some permitted existing garages and ancillary buildings converted into garden suites. Unpermitted structures are treated as new buildings under current zoning, regardless of age.
Existing-Unit Legalization and Compliance
Understand California's pre-2020 permit protections, health-and-safety limits, and why local ADU programs can issue records with different scopes.
Existing-Unit Legalization and Compliance
Berkeley's pilot offers two different certificate paths for qualifying unpermitted ADUs and JADUs: a building-permit route to a Certificate of Occupancy or a Housing Certificate of Compliance.
Existing-Unit Legalization and Compliance
New York City's Department of Buildings outlines a local path from deciding whether an illegal conversion can be legalized through permits, corrective work, final sign-off, and correction records.
Existing-Unit Legalization and Compliance
New York City's Local Law 126 pilot covers some existing occupied basement and cellar apartments, but DOB is not currently accepting applications for temporary residence authorization.
Existing-Unit Legalization and Compliance
Seattle identifies a construction permit to establish use as the route for legalizing an existing accessory dwelling unit; the permit record and approved scope still need to be checked for the property.
Existing-Unit Legalization and Compliance
Portland requires a permit for an ADU built without permits, while older accessory rental units may need a separate current-zoning status check.
Existing-Unit Legalization and Compliance
See what regulation 13 and a district council's regularisation certificate can establish, what checks may follow, and why planning permission remains separate.
Existing-Unit Legalization and Compliance
Oakland lists separate planning amnesty, enforcement-delay, and AB 2533 permit routes for qualifying existing ADUs and JADUs.
Existing-Unit Legalization and Compliance
Compare Carmarthenshire's inspection and correction route to its rare letter saying no further enforcement action will be taken.
Existing-Unit Legalization and Compliance
Hayward’s local process uses pre-2020 date evidence, an inspection and corrections before issuing a Certificate of Compliance.
Existing-Unit Legalization and Compliance
Costa Mesa’s pre-2020 ADU legalization guidance separates optional early inspections from permits, corrections and final inspections.
Existing-Unit Legalization and Compliance
Follow the City inspection, certificate preparation, notarization, and recording steps, then verify the separate permit and property records.
Existing-Unit Legalization and Compliance
Fremont separates an initial health-and-safety amnesty inspection from the later building permit and final inspections needed to legalize an ADU.
Existing-Unit Legalization and Compliance
San José asks for evidence that an unpermitted ADU predates 2020; if the City cannot establish the date, its FAQ points to the current-code permit path.
Existing-Unit Legalization and Compliance
Saskatoon limits its existing-suite program by dwelling type and installation date, and requires permits, corrections and a final inspection.
Existing-Unit Legalization and Compliance
Section 207.3 offers a local path for certain unauthorized dwelling units, with DBI eligibility screening, Planning approval and Building Code review.
Existing-Unit Legalization and Compliance
Riverside separates its SB 1226 date range for existing dwellings from the AB 2533 route for qualifying pre-2020 ADUs and JADUs.
Existing-Unit Legalization and Compliance
Marin County’s AB 2533 process includes an optional confidential pre-application inspection and a one-year completion window after applying for a permit.
Existing-Unit Legalization and Compliance
Unincorporated San Luis Obispo County uses different AB 2533 checklists depending on whether the host structure or an addition was permitted.
Existing-Unit Legalization and Compliance
Piedmont lists local building and fire items to check when legalizing an existing ADU, including egress, utilities, garage conversion and fire separation.
Existing-Unit Legalization and Compliance
Edinburgh and Highland describe different routes for incomplete work and completed work without a required building warrant.
Existing-Unit Legalization and Compliance
Mississauga requires existing second units to be registered and asks for an inspector-signed permit; an unpermitted unit must first enter the permit process.
Existing-Unit Legalization and Compliance
Merton’s regularisation certificate covers the Building Regulations requirements it specifies at the time of the unauthorized work, not planning or current-condition status.
Existing-Unit Legalization and Compliance
Pinole’s pre-2020 amnesty includes a self-assessment, City inspections and corrections; an enforcement delay is conditional and not final approval.
Existing-Unit Legalization and Compliance
Portland requires a building permit to document when an ADU or former ARU no longer functions as a separate dwelling unit.