An ADU zoning check starts with the exact parcel and the kind of dwelling you plan to create. Confirm whether the unit is detached, attached, converted from existing space, or treated as a junior unit locally; then read the current local zoning standards and permit route. State permission for ADUs does not mean one design fits one lot, and a zoning answer does not replace building, fire, utility, or recorded-property review.
Checked August 25, 2026. ADU names, review paths, setbacks, utility rules, and local ordinances can change.
Name the proposed dwelling before checking dimensions
The same backyard idea can enter a different rule path depending on whether it creates a complete independent dwelling, remains inside the main building, or shares facilities. The California Department of Housing and Community Development ADU page is a useful state example because it distinguishes ADUs and junior ADUs and links a current handbook. It is not a national rule. Outside California, use the definitions adopted by the city, county, or other authority that controls the parcel.
| Project description | Record before searching | Question for the local code |
|---|---|---|
| Detached unit | Footprint, height, distance from lot lines and main dwelling | Where may a new accessory dwelling sit on this lot? |
| Attached addition | Shared wall, added floor area, roof and entrance | Which addition and ADU standards apply together? |
| Interior conversion | Existing room, garage or basement and legal occupancy | Does the conversion need zoning review or a change in building use? |
| Junior or limited unit | Size, facilities, owner-occupancy facts and interior connection | Does this jurisdiction recognize a separate junior category? |
Match the address to one legal parcel
Search the official local parcel or zoning map and select the feature, not merely the address suggestion. Record the assessor parcel number, city or county, zoning district, overlays, lot boundary, and any split-zone line. A mailing address may name a city while the property lies in unincorporated territory. A corner lot may contain more than one parcel, and a condominium or planned community can have property records that the map does not explain.
- Compare the map boundary with the survey, assessor sketch, or deed description available to you.
- Save the base district and every overlay or special plan displayed for the selected parcel.
- Open the linked ordinance version and locate the local definition of accessory dwelling unit.
- Search parcel-specific cases, variances, conditions, easements, and recorded covenants separately.
If the street search is uncertain, use the parcel-number zoning lookup workflow. The zoning code versus zoning map guide explains why the district label and the written standards must be read together.
Test the design against the standards that actually bind it
Turn the concept into measurements before asking whether an ADU is allowed. Record existing and proposed building area, unit floor area, height, front and rear location, side and rear setbacks, lot coverage, parking, access, entrances, trees, utilities, and any work in an easement. Then trace each number to the local code section or an official project page. Do not transfer a setback or size limit from another city, even when both use the term ADU.
The City of Portland ADU zoning page shows why this screen is local: it connects placement, design, permit, and short-term-rental considerations within Portland rules. Use it only for a Portland parcel. For another location, find the equivalent planning or permitting page and current code chapter.
Access can be as important as floor area. Mark the route from the street to the proposed entrance, emergency access, refuse area, parking, meters, sewer or septic connection, water service, and utility easements. A design that appears to meet a setback can still change when the legal lot line, required access path, protected tree, drainage feature, or recorded easement is located accurately. Put uncertain dimensions on the sketch instead of replacing them with estimates.
Keep zoning permission and construction approval separate
A map and use table answer only part of the project. Building-code review may examine structure, fire separation, light, ventilation, energy, plumbing, electrical work, egress, and legal occupancy. Utility agencies may require service information. Historic, coastal, flood, wildfire, septic, tree, or design-review rules may sit outside the base zoning chapter. Fees and application documents can also depend on whether the work is new construction or a conversion.
| Gate | Evidence to obtain | What it does not prove |
|---|---|---|
| Zoning | District, overlay, ADU use rule and dimensional standards | That construction documents comply |
| Building and fire | Applicable code edition, plan requirements and inspections | That zoning or private restrictions permit the unit |
| Utilities | Water, sewer, power and access requirements | That capacity or connection approval is final |
| Property records | Easements, covenants, prior permits and lot history | That every private right has been cleared |
If the ADU rule or parcel result is missing
Do not treat a blank map, an old handout, or a search result with no ADU row as permission or prohibition. Retry with the parcel number, check city limits, open the ordinance index, and search for accessory apartment, secondary dwelling, backyard cottage, in-law unit, or local equivalent. If a recent rezoning or annexation is involved, save both dates and ask which rule edition applies to an application submitted now.
- Send the planning office the address, parcel number, district, overlays, and a simple site sketch.
- State the unit type, floor area, height, setbacks, access, parking, and utility concept.
- Ask which zoning section controls and which separate permit reviews are required.
- Request the available written confirmation process when the answer affects a purchase, loan, or construction contract.
Leave a project-specific record for the next decision
Save the official URLs, ordinance edition, map date, parcel identifier, measurements, staff response, and unresolved questions in one file. Recheck them before submitting plans because an ADU policy page is not a permit or an approval. If the planned unit may later be rented for short stays, review the separate short-term rental zoning check before assuming the ADU approval covers that activity.
For a purchase or construction contract, identify who will verify the survey, title restrictions, utility feasibility, and code design. The local planner can answer a defined zoning question, but one informal answer may not cover those other disciplines or create a vested right.