1. Confirm the property and zoning
Begin with the legal parcel, zoning designation, existing structures, recorded easements, and any overlay that affects development. Coastal, flood, wildfire, historic, environmental, airport, utility, and homeowners-association controls may require separate review.
Ask whether an ADU is allowed, how the unit is defined, whether owner occupancy or rental restrictions apply, and whether an existing violation or unpermitted structure must be resolved first.
2. Map the buildable area
Record front, side, and rear setbacks; building separation; lot coverage; floor-area limits; height; open-space rules; tree protections; and required access. Then place easements, utilities, drainage paths, septic areas, and fire access on the same base plan.
A dimension that looks generous on an online map may shrink after a survey and code analysis. Use verified boundaries and professional measurements for design decisions.
3. Define the required drawing set
Ask the reviewing authority for the current submittal checklist. A typical project may need a site plan, floor plans, elevations, sections, structural calculations, energy documents, utility plans, drainage information, landscape or tree information, and product specifications.
Identify which documents must be prepared or signed by licensed professionals. Confirm digital file standards, naming rules, application forms, deposits, and whether separate departments review the same project.
4. Coordinate utilities and life safety
Verify water, sewer or septic, electrical capacity, gas if proposed, stormwater, waste collection, and metering expectations. Ask utilities directly about connection procedures, service upgrades, lead times, and fees.
Fire access, hydrant distance, address visibility, alarms, separation, emergency egress, and sprinkler requirements can affect the design. Building-code compliance and planning approval are related but separate questions.
5. Understand review, inspections, and closeout
Request the current review sequence and ask which approvals must be complete before construction starts. Record the expected plan-check rounds, correction process, permit expiration rules, inspection stages, and required closeout documents.
Do not schedule occupancy or rental based on a best-case construction date. Include time for utility coordination, revisions, inspections, corrections, and final authorization to occupy.
- Planning or zoning approval
- Building, structural, mechanical, electrical, and plumbing review
- Utility and public-works coordination
- Fire, environmental, health, or specialty review where applicable
- Construction inspections and documented corrections
- Final approval or certificate required before occupancy
COMMON QUESTIONS
Frequently asked questions
Short answers to the practical questions homeowners ask while comparing ADU options.
Can a builder confirm that my ADU is allowed?+
A qualified builder can help assess feasibility, but obtain property-specific confirmation from the official authority and appropriate licensed professionals before making a major commitment.
Do ADU rules stay the same?+
No. State and local laws, fees, interpretations, and application procedures can change. Record the date of every source and recheck requirements before submission.
Does permit approval include utility approval?+
Not necessarily. Utilities and other agencies may use separate applications, fees, designs, or schedules. Ask for the complete interdepartmental path.
PRIMARY SOURCES
Sources and further reading
Regulations and program rules can change. Review the latest official material and confirm requirements with the authority responsible for the property.
This guide provides general educational information and does not replace property-specific legal, financial, tax, design, engineering, or construction advice. The editorial team writes the guide; the research-review role checks cited primary sources and calculation consistency. Last updated September 8, 2026.